WO2018229690A1

WO2018229690A1 - Head assembly

Info

Publication number: WO2018229690A1
Application number: PCT/IB2018/054334
Authority: WO
Inventors: Christopher COUTU; Sergio HUAPAYA
Original assignee: Groupe Fordia Inc.
Priority date: 2017-06-14
Filing date: 2018-06-13
Publication date: 2018-12-20

Abstract

A head assembly (50) for retrieving a core sample. The head assembly (50) includes an axial passageway (84) though which drilling fluids can circulate inside the head assembly (50). In some embodiments, a valve (82) is provided to selectively obstruct the head assembly (50). The valve (82) provides information about the state of the head assembly (50) to a surface operator by providing high or low resistance to fluid flow through the axial passageway (84), according to the configuration of the head assembly (50).

Description

HEAD ASSEMBLY

FIELD OF THE INVENTION

[001] This invention relates to the retrieval of core samples. More particularly, the invention relates to a head assembly for a core barrel assembly.

BACKGROUND OF THE INVENTION

[002] Core samples are obtained through core drilling operations. Core drilling is typically conducted with a core drill comprising an outer tube assembly and an inner tube, the inner tube being secured to a head assembly to form a core barrel assembly. A hollow drill bit are attached to the outer tube assembly, typically with a reamer therebetween, so that rotational torque applied to the outer tube assembly is transmitted to the drill bit. A core is generated during the drilling operation, with the core progressively extending along the inner tube as drilling progresses. When a core sample is acquired, the core within the inner tube is fractured. The core barrel assembly, and the fractured core sample contained therein, are then retrieved from within the drill hole, typically by way of a retrieval cable lowered down the drill hole and attached to the inner barrel assembly with an overshot. Once the inner barrel assembly has been removed from the bore, the core sample can be removed and subjected to analysis.

[003] Typically, the head assembly and inner tube are secured in position inside the outer tube assembly by the means of latches that extend substantially radially outwardly from the inner barrel barrel assembly. The latches are received inside notches or grooves formed into the inner surface of the outer tube assembly and are selectively retractable for locking and unlocking the inner barrel assembly to and from the outer tube assembly. However, currently used latches may become disengaged from the outer tube assembly during the drilling process because of vibrations and pressure changes produced during this process. A mislatch is inconvenient as the core can then no longer be retrieved. Also, in uphole drilling, a mislatch represents a danger since the core barrel assembly can come back to the driller's working area. In addition, the inner barrel assembly may be damaged if this occurs.

[004] Also, retrieval and lowering of the head assembly represents a significant portion of the time spent drilling. Since any minute spent during a drilling operation is expensive, there is a need to accelerate these operations while ensuring that they remain safe ad reliable.

[005] Against this background, there exists a need in the industry to provide an improved head assembly.

[006] An object of the present invention is therefore to provide an improved head assembly.

SUMMARY OF THE INVENTION

[007] In a broad aspect, the invention provides a head assembly for supporting an inner tube usable to retrieve a core sample and releasably latching in a latch seat provided in an outer tube assembly of a drill string, the head assembly including: a substantially elongated main body defining a main body outer surface; substantially axially opposed main body proximal and distal ends; a main body passageway extending substantially axially therethrough between the main body proximal and distal ends; a tube attachment at the main body distal end for attaching the inner tube thereto; and a main body latch slot extending between the main body passageway and main body outer surface, the main body latch slot being substantially elongated and substantially axially extending; a latch pivotably mounted at the main body latch slot so as to be pivotable about a latch pivot axis, the latch pivot axis extending across the main body latch slot circumferentially relative to the main body, the latch being movable between a latch extended position wherein a latch radially outwardmost portion of the latch protrudes radially outwardly from the main body and a latch retracted position wherein the latch radially outwardmost portion is radially inwardly located relative to a position of the latch radially outwardmost portion in the latch extended position; a latch actuator mounted to the main body and operatively coupled to the latch for selectively moving the latch from the latch retracted position to the latch extended position; wherein the head assembly defines an axial passageway extending therealong between the main body distal and proximal ends to allow fluids to move through the axial passageway between the main body distal and proximal ends with the fluids remaining inside the head assembly.

[008] There may also be provided a head assembly further comprising a valve for selectively at least partially obstructing the axial passageway.

[009] There may also be provided a head assembly further comprising a valve for selectively substantially obstructing the axial passageway.

[0010] There may also be provided a head assembly wherein the valve includes a valve body provided in the main body passageway and defining a valve body passageway extending axially therethrough, the valve body passageway defining part of the axial passageway, the valve body defining a valve seat around the valve body passageway; a valve stop movable axially along the valve body passageway; and a stopper provided proximally relative to the valve seat and extending across the axial passageway for preventing movements of the valve stop proximally to the stopper; wherein, when the valve stop is withdrawn from the valve seat, the valve is in a valve open configuration allowing passage of fluids axially therethrough, and when the valve stop is seated on the valve seat, the valve is in a valve closed configuration substantially preventing passage of fluids therethrough.

[0011] There may also be provided a head assembly wherein the valve stop is smaller than a cross-section of the axial passageway at the stopper to allow passage of fluids around the stopper when the valve stop abuts against the stopper.

[0012] There may also be provided a head assembly wherein the main body defines a main body valve aperture extending between the main body passageway and main body outer surface; the valve body defines a valve body aperture extending substantially radially therethrough from the valve body passageway; the valve body is movable between valve body proximalmost and distalmost positions wherein the valve body aperture is respectively proximal and distal relative to the main body valve aperture.

[0013] There may also be provided a head assembly wherein the valve body is also movable to a valve body register position wherein the valve body aperture and the main body valve aperture are substantially in register with each other. [0014] There may also be provided a head assembly wherein the latch actuator includes a latch piston provided distally relative to the latch, the latch piston being movable between a latch piston distalmost position and a latch piston proximalmost position, wherein, in the latch piston distalmost position, the latch piston is spaced apart from the latch so that the latch is movable between the latch extended and retracted positions, and in the latch piston proximalmost position, the latch piston engages the latch and pushes the latch to the latch extended position.

[0015] There may also be provided a head assembly wherein the latch is freely movable between the latch extended and retracted positions when the latch piston is in the latch piston distalmost position.

[0016] There may also be provided a head assembly wherein the latch piston defines a latch piston passageway extending axially therealong and defining part of the axial passageway, the latch piston being terminated proximally by a piston cam surface extending across the latch piston passageway and engaging the latch in the latch piston proximalmost position, the piston cam surface being provided with at least one cam surface aperture extending therethrough forming part of the latch piston passageway.

[0017] There may also be provided a head assembly wherein the latch is configured and sized to achieve the latch retracted position under the action of the fluids on the latch when the head assembly is lowered in a fluid column.

[0018] There may also be provided a head assembly wherein in the latch retracted position, the latch is completely withdrawn inside the main body latch slot. [0019] There may also be provided a head assembly further comprising a spearhead point at the main body proximal end securable to an overshot.

[0020] There may also be provided a head assembly further comprising a latch collar provided in the main body passageway, the latch collar defining a collar latch slot extending radially therethrough, the latch collar being movable between latch collar proximal and distal positions, wherein, in the latch collar distal position, the collar latch slot is in register with the main body latch slot and allows movement of the latch to the latch extended position and, in the latch collar proximal position, the latch collar at least partially obstructs the main body latch slot so that the latch is constrained in the latch retracted position.

[0021] There may also be provided a head assembly wherein the spear head point and the latch collar are mechanically coupled to each other so as to be jointly movable axially relative to the main body upon the spearhead point being moved proximally.

[0022] There may also be provided a head assembly further comprising a latch collar biasing element biasing the latch collar towards the latch collar distal position.

[0023] There may also be provided a head assembly wherein the spearhead point is movable axially over a predetermined movement range relative to the main body, a resiliently deformable bumper being provided between spearhead point and the main body to absorb overshot landing shocks on the spearhead point.

[0024] There may also be provided a head assembly wherein the main body defines at least three main body latch slots each extending between the main body passageway and main body outer surface, each of the main body latch slots being substantially elongated and substantially axially extending and wherein a latch is pivotably mounted at each of the main body latch slots so as to be pivotable about a respective latch pivot axis, each latch pivot axis extending across the respective one of the main body latch slots circumferentially relative to the main body.

[0025] There may also be provided a head assembly further comprising a valve for selectively substantially obstructing the axial passageway, the valve including a valve body provided in the main body passageway and defining a valve body passageway extending axially therethrough, the valve body passageway defining part of the axial passageway, the valve body defining a valve seat around the valve body passageway, the valve body being movable between valve body proximalmost and distalmost positions along the main body passageway; and a valve stop movable axially along the valve body passageway; wherein, when the valve stop is withdrawn from the valve seat, the valve is in a valve open configuration allowing passage of fluids axially therethrough, and when the valve stop is seated on the valve seat, the valve is in a valve closed configuration substantially preventing passage of fluids therethrough; a stopper provided proximally relative to the valve seat and extending across the axial passageway for preventing movements of the valve stop proximally further than the stopper, the valve stop and stopper being configured and sized for allowing passage of fluids around the valve stop when the valve stop abuts against the stopper; and a latch piston mounted in the main body passageway distally to the latches and defining part of the axial passageway, the latch piston defining latch piston proximal and distal ends, the valve body being provided at the latch piston distal end, the latch piston being movable between latch piston proximalmost and distalmost positions along the main body passageway, wherein, in the latch piston distalmost position, the latch piston is spaced apart from the latch so that the latch is movable between the latch extended and retracted positions, and in the latch piston proximalmost position, the latch piston engages the latch and pushes the latch to the latch extended position; the valve body and latch piston being movable between an engaged configuration and a disengaged configuration, wherein, in the engaged configuration, the valve body and latch piston are secured to each other and prevented from moving axially from each other beyond a predetermined distance, and, in the disengaged configuration, the valve body and latch piston are movable independently from each other along the main body passageway further away than the predetermined distance.

[0026] There may also be provided a head assembly wherein the stopper is provided in the latch piston.

[0027] There may also be provided a head assembly wherein the valve body defines axially opposed valve body proximal and distal ends, the valve seat being provided at the valve body distal end.

[0028] There may also be provided a head assembly wherein, in the engaged configuration, the latch piston is maintained distal to the latch piston proximalmost position by the valve body.

[0029] There may also be provided a head assembly wherein, in the engaged configuration, the valve body is maintained proximal to the valve body distalmost position by the latch piston.

[0030] There may also be provided a head assembly wherein, in the engaged configuration, the latch piston is maintained distal to the latch piston proximalmost position by the valve body and the valve body is maintained proximal to the valve body distalmost position by the latch piston.

[0031] There may also be provided a head assembly wherein the latch piston and valve body are configured and sized to that the disengaged configuration is achieved from the engaged configuration when a predetermined axial tension is exerted between the latch piston and valve body; and the engaged configuration is achieved from the disengaged configuration when a predetermined axial compression is exerted between the latch piston and valve body.

[0032] There may also be provided a head assembly wherein one of the latch piston and valve body defines a resiliently deformable tongue having a hook portion; and an other one of the latch piston and valve body defines a hook receiving portion for releasably receiving the hook portion; wherein, in the engaged configuration, the hook portion is received by the hook receiving portion, and, in the disengaged configuration, the hook portion is outside of the hook receiving portion; the valve body and latch piston being configured and sized so that passage between the engaged and disengaged configurations occurs through deformation of the tongue to allow movements of the hook portion and hook receiving portion relative to each other.

[0033] There may also be provided a head assembly wherein the hook receiving portion defines a flange, the hook being raised over the flange through deformation of the tongue when moving between the engaged and disengaged configurations. [0034] There may also be provided a head assembly further comprising a latch piston biasing element biasing the latch piston towards the latch piston proximalmost position and a valve body biasing element biasing the valve body towards the valve body proximalmost position.

[0035] There may also be provided a head assembly wherein in the engaged configuration with the valve body in the valve body proximalmost position, the latch piston is disengaged from the latch.

[0036] There may also be provided a head assembly wherein in the engaged configuration with the valve body in the valve body proximalmost position, the latch piston is between the latch piston proximalmost and distalmost positions.

[0037] There may also be provided a head assembly wherein in the disengaged configuration, the latch piston is moved to the latch piston proximalmost position by the latch piston biasing element.

[0038] There may also be provided a head assembly wherein the main body defines a main body valve aperture extending between the main body passageway and main body outer surface; the valve body defines a valve body aperture extending substantially radially therethrough from the valve body passageway; the valve body aperture being respectively proximal and distal relative to the main body valve aperture in the valve body proximalmost and distalmost positions.

[0039] There may also be provided a head assembly wherein in the engaged configuration, the valve body aperture is in register with the latch piston so that the latch piston obstructs the valve body aperture, and, in the disengaged configuration, the latch piston is movable to be withdrawn from the valve body aperture.

[0040] There may also be provided a head assembly wherein the valve body is also movable to a valve body register position wherein the valve body aperture and the main body valve aperture are substantially in register with each other.

[0041] There may also be provided a head assembly wherein the latch piston, valve body and valve stop are configured and sized so that in the engaged configuration, creating a predetermined fluid pressure differential between the main body proximal and distal ends with a higher pressure at the main body proximal end causes the valve to achieve the valve closed configuration and to exert the predetermined axial tension to cause the latch piston and valve body to achieve the disengaged configuration, thereby allowing movement of the latch piston towards the latch piston proximalmost position; causing a resistance to pumping of the fluids in a distal direction through the axial passageway.

[0042] There may also be provided a head assembly further comprising a shut off provided distally to the main body valve aperture for sealing passage of fluids between the head assembly and the outer tube assembly upon a predetermined shut off compression being exerted between the inner tube and the latch.

[0043] There may also be provided a head assembly wherein the latch piston and valve body are configured and sized so that with no fluid pressure differential exerted between the main body proximal and distal ends, moving the latch to the latch retracted position causes the latch piston and valve body to enter the engaged configuration.

[0044] There may also be provided a head assembly wherein the predetermined axial tension is larger than the predetermined axial compression.

[0045] There may also be provided a head assembly wherein the main body defines a main body bypass aperture extending between the main body outer surface and the main body passageway distal to the latch piston, the head assembly further comprising a dry hole adapter mountable to the main body distal to the latch piston with the valve body removed from the head assembly, the dry hole adapter defining a dry hole adapter bypass aperture extending in register with the main body bypass aperture and a dry hole adapter passageway extending between the dry hole adapter bypass aperture and the latch piston passageway, the dry hole adapter passageway defining a neck and the dry hole adapter passageway containing an adapter biasing element distal to the neck, the neck and adapter biasing element being configured and sized so that when fluids are pumped though the dry hole adapter in a distal direction, the valve stop is maintained in the neck by the biasing element and substantially obstructs passage of fluid through the neck until a predetermined fluid pressure differential across the dry hole adapter is achieved, at which point the valve stop moves distal to the neck to allow fluids to exit through the bypass apertures.

[0046] There may also be provided a head assembly wherein the main body defines a landing shoulder for abutting on the landing ring.

[0047] There may also be provided a head assembly further comprising a removable resiliently deformable seal mounted to the main body for sealing against the outer tube assembly.

[0048] There may also be provided a head assembly wherein the head assembly includes a core stopper at the main body distal end, the core stopper being axially rotatable relative to the latch.

[0049] There may also be provided a head assembly wherein the head assembly is configure and sized so that in operation, after throwing down the head assembly in a fluid column while pumping fluid, landing the head assembly while continuing pumping causes a persistent increase in resistance to pumping that results in a persistent increase in pressure in the fluid column.

[0050] The proposed head assembly is relatively easily manufacturable at a relatively low cost using known components and methods. Furthermore, the proposed head assembly is relatively robust and is therefore at relatively low risk of being damaged during operation. Yet furthermore, the proposed head assembly includes many safety features and is relatively convenient to operate due to the mechanical logic implemented therein.

[0051] Advantageously, the axial passageway accelerates descent of the head assembly in a fluid column contained in the drilling rods as the fluid can then pass inside the head assembly, instead of being limited to the small space between the head assembly and the outer tube assembly. Since this space is relatively small, a lot of resistance to the descent of the head assembly is created in this small space.

[0052] Also, in some embodiments, the latches are completely retracted inside the main body during descent. Therefore, there is no friction between the latches and the drilling rods during descent. This further decreases the friction between the head assembly and the drilling rods compared to some existing head assemblies, and reduces wear on the latches.

[0053] The proposed head assembly can, in some embodiments, also be used in underground operation, in which the head assembly is pushed sometimes against gravity with a fluid, or in dry holes in which a water column is not formed, or formed with difficulty, because of leaks.

[0054] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In the appended drawings:

[0056] Figure 1 , in a perspective cutaway view, illustrates a head assembly in accordance with an embodiment of the present invention;

[0057] Figure 2, in a perspective cutaway view, illustrates latches part of the head assembly of FIG. 1 and adjacent portions of the head assembly, the latches being shown in a latch extended position;

[0058] Figure 3, in a perspective cutaway view, illustrates the latches and adjacent portions of the head assembly of FIG. 2 , the latches being shown in a latch retracted position;

[0059] Figure 4, in a partially exploded view, illustrates the head assembly of FIG. 1 ;

[0060] Figure 5, in a side cross-sectional view, illustrates a step in the operation of the head assembly of FIGS. 1 and 4;

[0061] Figure 6, in a side cross-sectional view, illustrates an other step in the operation of the head assembly of FIGS. 1 and 4;

[0062] Figure 7, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0063] Figure 8, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0064] Figure 9, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0065] Figure 10, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0066] Figure 1 1 , in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4; [0067] Figure 12, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0068] Figure 13, in a side cross-sectional view, illustrates yet an other step in the operation of the head assembly of FIGS. 1 and 4;

[0069] Figures 14, in a side cross-sectional view, illustrates a valve body and part of a latch piston both part of the head assembly of FIGS. 1 and 3 to 13, here shown in an engaged configuration;

[0070] Figure 15, in a partial perspective cut away view, illustrates the valve body and the latch piston of FIG. 14 in the engaged configuration;

[0071] Figures 16, in a side cross-sectional view, illustrates the latch piston and valve body of FIGS. 14 and 15 in a disengaged configuration;

[0072] Figure 17, in a partial perspective cut away view, illustrates the latch piston and valve body of FIGS. 14 to 16 in the disengaged configuration;

[0073] Figure 18, in a side cross-sectional view, illustrates a dry hole kit usable in the head assembly of FIGS. 1 and 4 to 14; and

[0074] Figure 19, in a side cross-sectional view, illustrates a resiliently deformable seal usable in the head assembly of FIGS. 1 and 4 to 14 for underground drilling.

DETAILED DESCRIPTION [0075] Referring to FIG. 1 , there is shown a head assembly 50 for retrieving a core sample (not shown in the drawings) in a drilling bore (not shown in the drawings). As seen for example in FIG. 9, the head assembly 50 is used in a drill string including an outer tube assembly 52 (only part of which is illustrated) supporting a distal drill bit (not shown in the drawings). The outer tube assembly 52 may in some embodiments be a conventional outer tube assembly 52 including a locking coupling 54 secured to proximally located drill rods, an adapter coupling 56 secured to the locking coupling 54 and an outer tube 58 secured to the adapter coupling 56. The outer tube assembly 52 defines a latch seat 60 in the form of a conventional shoulder adjacent the junction between the locking and adapter couplings 54 and 56 defined by a groove in the adapter coupling 56 that frees the distal end of the locking coupling 54 so that the latter can define the shoulder. The latch seat 60 faces generally towards the distal end of the outer tube assembly 52. The latch seat 60 is usable to firmly secure the head assembly 50 adjacent the distal end of the drilling bore during the drilling process. The outer tube assembly 52 also includes an outer tube landing ring 62 distally relative to the latch seat 60 and protruding radially inwardly in the outer tube assembly 52, typically adjacent the junction between the adapter coupling 56 and outer tube 58. The landing ring 62 stops the distally oriented movement of the head assembly 50 substantially adjacent the drill bit when the head assembly 50 is inserted in the outer tube assembly 52. The head assembly 50 is usable with a fluid, such as a conventional drilling fluid.

[0076] The terminology distal and proximal refers to the distance from an operator located outside of the bore. Therefore, proximal elements are closer to the operator of the head assembly 50 than distal elements. This terminology is used to facilitate the description of the head assembly 50 and should not be used to restrict the scope of the present invention. The term "axial" refers to a direction parallel to the longitudinal axis of the drill string. Also, the terminology "substantially" is used to denote variations in the thus qualified terms that have no significant effect on the principle of operation of the head assembly 50. These variations may be minor variations in design or variations due to mechanical tolerances in manufacturing and use of the head assembly 50. These variations are to be seen with the eye of the reader skilled in the art. The present application claims priority from US provisional patent application 62519469 filed June 14, 2017, the contents of which is hereby incorporated by reference in its entirety.

[0077] Referring to FIG. 1 for example, the head assembly 50 includes a main body 64, one or more latch 2 and a latch actuator 74. The head assembly 50 is usable with a conventional overshot 40, partially shown in FIG. 12. The latch actuator 74 and latch 2 are mounted to the main body 64. The latch actuator 74 is operatively coupled to the latch 2 for selectively moving the latch from a latch retracted position to a latch extended position, as detailed hereinbelow.

[0078] The main body 64 typically has a generally elongated cylindrical configuration and is sized so as to substantially fill the portion of the outer tube assembly 52 where the head assembly 50 is located. The main body 64 defines a main body outer surface 48, which is typically of generally cylindrical configuration. The main body 64 also defines substantially axially opposed main body proximal and distal ends 66 and 68 and a main body passageway 70 extending substantially axially therethrough between the main body proximal and distal ends 66 and 68. The main body 64 may be manufactured in a single block of material. However, typically, the main body 64 is manufactured using many segments that are secured to each other using threads, nuts 10 and 37 and spindle shaft 16, for example main body first, second, third, fourth and fifth segments 1 , 3, 12, 5 and 17. The use of many segments facilitates manufacturing, assembly, maintenance and repair of the head assembly 50 and is known in the art. The coupling between the main body first, second, third, fourth and fifth segments 1 , 3, 12, 5 and 17 is therefore known in the art and not further described. The main body fifth segment 17, to which an inner tube 39 (seen in FIG. 10) is attachable, may rotate in some embodiments relative to the remainder of the main body 64, for example on the spindle shaft 16 through bearing 15. Grease may be applied to the interior of the head assembly 50 using a grease fitting 9 removable to reveal an aperture leading into the head assembly 50. Typically, the main body 64 defines a landing shoulder 4 for abutting on the landing ring 62 when the landing ring 62 is reached.

[0079] The head assembly defines an axial passageway 84 (seen for example in FIGS. 5 to 13) extending therealong between the main body distal and proximal ends 68 and 66 to allow fluids to move through the axial passageway 84 between the main body distal and proximal ends 68 and 66 with the fluids remaining inside the head assembly 50.

[0080] In other words, fluids can enter the head assembly 50 at the main body distal end 68, and through a path that extends through the whole head assembly 50 only, for example through the center thereof, and exit at the main body proximal end 86. Therefore, when the head assembly 50 is lowered in a fluid column, for example contained in drilling rods, the fluids don't have to go only through the relatively tight space between the head assembly 50 and the drilling rods, but may also go through the center of the head assembly 50, which allows the head assembly 50 to be lowered faster in the fluid column. It should be noted that the axial passageway 84 does not need to be straight and completely unobstructed. However, there needs to be a straight or more or less direct path through the head assembly 50 that allows passage of the fluids, even though.

[0081] In some embodiments, the head assembly 50 further includes a valve 82 for selectively at least partially obstructing the axial passageway 84. In some embodiments, the valve 82 is provided for selectively substantially obstructing the axial passageway. The term "substantially obstructing" means that fluids cannot flow through the valve 82 in large quantities, but that there can be relatively small leaks, due for example to manufacturing imperfections or to wear in the valve 82. However, these small leaks are not sufficient to alter the manner in which the head assembly 50 operates, as described below.

[0082] The main body passageway 70 has a generally cylindrical configuration and receives thereinto the latch actuator 78, valve 82 and latches 2. The main body passageway 70, and correspondingly the latch actuator 78 and valve 82 are not necessarily of uniform transversal cross-sectional configuration longitudinally therealong as shoulders, described in further details hereinbelow, are defined therein to limit movements of some components of the head assembly 50 in the main body passageway 70.

[0083] A tube attachment 71 is provided at the main body distal end 68 for attaching the inner tube 39 thereto. For example, the tube attachment 71 takes the form of an internal thread to which the inner tube 39 can be screwed.

[0084] At least one main body latch slot 72 extends between the main body passageway 70 and the body outer surface 12. Typically, more than one main body latch slot 72 is provided, for example, 2, 3 or 4 body latch slots. When more than one main body latch slot 72 is provided, the main body latch slots may for example be equidistantly spaced apart from each other around a circumference of the main body 64. Each of the main body latch slots 72 is substantially elongated and substantially axially extending.

[0085] As better seen in FIGS. 2 and 3, a latch 2 is pivotably mounted at each of the main body latch slots 72 so as to be pivotable about a latch pivot axis 75. The latch pivot axis extends across the main body latch slot 72 circumferentially relative to the main body 64, each latch 2 being movable between a latch extended position (seen for example in FIG. 2) wherein a latch radially outwardmost portion 76 of the latch 2 protrudes radially outwardly from the main body 64 and a latch retracted position (seen for example in FIG. 3) wherein the latch radially outwardmost portion 76 is radially inwardly located relative to a position of the latch radially outwardmost portion 76 in the latch extended position.

[0086] In some embodiments, in the latch retracted position, the latches 2 are completely withdrawn inside the main body latch slots 72. However, in other embodiments, the latches 2 may slightly protrude from the main body 64 in the latch retracted position.

[0087] It should be noted that in some embodiments, the configuration of the mechanism that is used to move latches 2 received in the latch slots 72 allows for the use of more than 2 latches and corresponding main body latch slots 72, for example at least three latches 2 and main body latch slots 72. This is in contrast to many existing similar mechanisms that can only accommodate two latches because of their configuration and actuation mechanism. Having more than 2 latches may be advantageous as it allows to better spread the relatively large loads supported by the latches 2 between a larger number of latches 2, and may, in some embodiments, increase locking coupling 54 life.

[0088] In some embodiments, the latches 2 are substantially freely movable between the latch extended and retracted positions when a latch piston 32 part of the latch actuator 78 and further described hereinbelow is in a latch piston distalmost position. In this position, the latch piston 32 is spaced apart from the latches 2 and in opposition to some existing head assemblies, no biasing element is present to bias the latches 2 to either the latch extended or retracted positions. In some embodiments, retraction at throwdown is achieved through the interaction between the latches 2 and the fluid column, as described below.

[0089] Referring for example to FIG. 4, the latch actuator 78 includes a latch piston 32 provided distally relative to the latches 2. The latch piston 32 defines latch piston proximal and distal ends 90 and 93. The latch piston 78 is movable between a latch piston distalmost position (seen for example in FIG. 6) and a latch piston proximalmost position (seen for example in FIG. 7). In the latch piston distalmost position, the latch piston 32 is spaced apart from the latches 2 so that the latches 2 are movable between the latch extended and retracted positions. In the latch piston proximalmost position, the latch piston 32 engages the latches 2 and pushes the latches 2 to the latch extended position.

[0090] Referring to FIG. 1 , the latch piston 32 defines a latch piston passageway 88 (seen in FIGS. 5 to 13 for example) extending axially therealong and defining part of the axial passageway 84. The latch piston 32 is terminated proximally by a piston cam surface 92 extending across the latch piston passageway 88 and engaging the latches 2 in the latch piston proximalmost position. The piston cam surface 92 is provided with at least one cam surface aperture 94 extending therethrough forming part of the latch piston passageway 88.

[0091] The latch piston 32 defines a distally facing latch piston shoulder 96 and the main body 64 defines a proximally facing main body piston shoulder 98. A latch piston biasing element 1 1 , for example a coil spring, is provided between the latch piston shoulder 96 and the main body piston shoulder 98 and biases the latch piston 32 towards the latch piston proximalmost position. When the latch piston biasing element 1 1 is fully compressed, the latch piston is in the latch piston distalmost position.

[0092] Referring for example to FIG. 1 7, the latch piston 32 also defines a hook receiving portion 104, the purpose of which is further explained hereinbelow. For example, the hook receiving portion 1 04 includes an annular flange 1 06 extending around the outer surface of the latch piston 32.

[0093] Referring for example to FIG. 16, the valve 82 includes a valve body 6 provided in the main body passageway 70 and defining a valve body passageway 108 extending axially therethrough, the valve body passageway 108 defining part of the axial passageway 84. The valve body 6 defines a distally located valve seat 1 10 around the valve body passageway 108, defining for example an annular restriction inside the valve body passageway 108. The valve body 6 defines axially opposed valve body proximal and distal ends 85 and 87. In some embodiments, the valve seat 1 10 is provided at the valve body distal end 87.

[0094] A valve stop 8, for example a ball, is movable axially along the valve body passageway 108. A stopper 1 12, seen for example in FIGS. 5 to 13 is provided proximally relative to the valve seat 1 1 0 and extends across the axial passageway 84 for preventing movements of the valve stop 8 proximally to the stopper 1 12. For example, in some embodiments, the stopper 1 12 takes the form of a pin extending diametrically across the latch piston passageway 88. In other embodiments, as in the drawings, the stopper 1 12 includes a proximal wall of the latch piston 32 that is configured to allow flow of fluids around the valve stop 8 through the cam surface apertures 94 when the valve stop 8 abuts against the latch proximal wall. Other suitable stoppers are also within the scope of the invention.

[0095] When the valve stop 8 is withdrawn from the valve seat 1 10, the valve 82 is in a valve open configuration allowing passage of fluids axially therethrough. When the valve stop 8 is seated on the valve seat 1 10, the valve 82 is in a valve closed configuration substantially preventing passage of fluids therethrough. The valve stop 8 and stopper 1 12 are configured and sized for allowing passage of fluids around the valve stop 8 when the valve stop 8 abuts against the stopper 1 12. For example, in some embodiments, the valve stop 8 is smaller than a cross-section of the axial passageway 84 at the stopper 1 12 to allow passage of fluids around the valve stop 8 when the valve stop 8 abuts against the stopper 1 12. Therefore, the valve 82 controls flow of fluids through the axial passageway 84.

[0096] Returning to FIG. 1 , in some embodiments, the valve 82 also controls flows of fluids laterally between inside and outside the main body 64 when fluids flow distally. To that effect, the main body 64 defines a main body valve aperture 1 14 extending between the main body passageway 70 and main body outer surface 48. The valve body 6 defines a valve body aperture 1 16 extending substantially radially therethrough from the valve body passageway 108 (not shown in FIG. 1 ). It should be noted that typically, many main body valve apertures 1 14 and valve body apertures 1 16 are provided, distributed circumferentially around the valve 82. and configured to never block out due to misalignment between the main body valve apertures 1 14 and valve body apertures 1 16 if the valve body 6 rotates on its axis.

[0097] The valve body 6 is movable between valve body proximalmost and distalmost positions (seen respectively in FIGS. 5 and 6 for example) wherein the valve body aperture 1 16 is respectively proximal and distal relative to the main body valve aperture 1 14. The valve body 6 is also movable to a valve body register position (seen in FIG. 9) wherein the valve body aperture 1 16 and the main body valve aperture 1 14 are substantially in register with each other.

[0098] The main body 64 defines a main body first valve shoulder 120 facing generally distally and the valve body 6 defines a valve body flange 122 protruding radially outwardly therefrom. The main body 64 also defines a main body second valve shoulder 128 facing generally proximally, and located distally relative to the main body first valve shoulder 120. When the valve body 6 is in the valve body proximalmost position, the valve body flange 122 abuts against the main body first valve shoulder 120, which prevents further proximal movements of the valve body 6. When the valve body 6 is in the valve body distalmost position, the valve body flange 122 abuts against the main body second valve shoulder 128, which prevents further distal movements of the valve body 6.

[0099] A valve body biasing element 34, for example a coil spring, biases the valve body 6 towards the valve body proximalmost position. The valve body biasing element 34 is provided between a valve biasing element shoulder 129 provided in the main body passageway 70 distally to the valve body 6 and the valve body 6. [00100] As better seen for example in FIGS. 14 to 17, the valve body 6 also defines at least one, and typically a plurality of circumferentially spaced apart, resiliently deformable tongue 130 having a hook portion 132. The hook receiving portion 104 is provided for releasably receiving the hook portion 132. For example, the hook portion 132 takes the form of a flange protruding radially inwardly at the proximal end of the tongues 130. The interaction between the hook portion 132 and the hook receiving portion 104 is further described hereinbelow.

[00101] The valve body 6 is provided at the latch piston distal end 93. The valve body 6 and latch piston 32 are movable between an engaged configuration (seen for example in FIGS. 14 and 15) and a disengaged configuration (seen for example in FIGS. 16 and 17). In the engaged configuration, the valve body 6 and latch piston 32 are secured to each other and prevented from moving axially from each other beyond a predetermined distance. In the disengaged configuration, the valve body 6 and latch piston 32 are movable independently from each other along the main body passageway 70 further away than the predetermined distance. In the engaged position, the latch piston 32 and valve body 6 may be fixed relative to each other, or allowed to become even closer than the predetermined distance. In the engaged configuration, the latch piston 32 is maintained distal to the latch piston proximalmost position by the valve body 6 and the valve body 6 is maintained proximal to the valve body distalmost position by the latch piston 32. In other words, in the engaged configuration, the valve body 6 and latch piston 32 have a restricted range of motion. When the disengaged configuration is achieved, the valve body 6 and latch piston 32 can move further respectively distally and proximally than in the engaged position to perform some actions that implement functionalities in the head assembly 50. [00102] In the engaged configuration, the hook portion 132 is received in the hook receiving portion 104, and in the disengaged configuration the hook portion 132 is outside of the hook receiving portion 104. For example, the flange 106 interferes with the hook portion 132 to retain the hook portion 132 in the hook receiving portion 104 in the engaged configuration. The valve body 6 and latch piston 32 are configured and sized so that passage between the engaged and disengaged configurations occurs through deformation of the tongue 130 to allow movements of the hook portion 132 and hook receiving portion 104 relative to each other. In the specific embodiment shown in the drawings, this is achieved by the hook portion 132 being raised over the flange 106 through deformation of the tongue 130 when moving between the engaged and disengaged configurations.

[00103] The disengaged configuration is achieved from the engaged configuration when a predetermined axial tension is exerted between the latch piston 32 and valve body 6. The engaged configuration is achieved from the disengaged configuration when a predetermined axial compression is exerted between the latch piston 32 and valve body 6. The magnitudes of the predetermined axial tension and compression are determined by the material properties, shape and dimensions of the tongues 130 and by the shape and dimensions of the surfaces of the hook portion 132 and flange 106 that abut against each other during this transition. In some embodiments, the predetermined axial tension is larger than the predetermined axial compression, so that disengagement between the latch piston 32 and valve body 6 is more difficult then re-engagement of these components.

[00104] It should be noted that in other embodiments, the hook receiving portion 104 and hook portion 132are on the other component, ie respectively on the valve body 6 and latch piston 32. Also, while the flange 106 protrudes outwardly and the hook portions 132 are open inwardly, the opposite is also within the scope of the invention with a flange 106 provided inside the latch piston 32. Finally, other mechanism for achieving the engaged and disengaged configurations are within the scope of the invention. For example, and non-limitingly, a recess could replace the flange 106.

[00105] In the engaged configuration with the valve body 6 in the valve body proximalmost position, the latch piston 32 is disengaged from the latches 2. In the engaged configuration with the valve body 6 in the valve body proximalmost position, the latch piston 32 is between the latch piston proximalmost and distalmost positions. In the disengaged configuration, the latch piston 32 is moved to the latch piston proximalmost piston by the latch piston biasing element 1 1 .

[00106] In the engaged configuration, the valve body aperture 1 16 is in register with the latch piston 32 so that the latch piston 32 obstructs the valve body aperture 1 16. In the disengaged configuration, the latch piston 32 is movable to be withdrawn from the valve body aperture 1 16.

[00107] The latch piston 32, valve body 6 and valve stop 8 are configured and sized so that in the engaged configuration, creating a predetermined fluid pressure differential between the main body proximal and distal ends 66 and 68 with a higher pressure at the main body proximal end 66 causes the valve 82 to achieve the valve closed configuration and to exert the predetermined axial tension to cause the latch piston 32 and valve body 6 to achieve the disengaged configuration. Thus, movement of the latch piston 32 towards the latch piston proximalmost position is allowed, and a resistance to pumping of the fluids in a distal direction through the axial passageway 84 is created.

[00108] The latch piston 32 and valve body 6 are configured and sized so that with no fluid pressure differential exerted between the main body proximal and distal ends 66 and 68, moving the latches 2 to the latch retracted position causes the latch piston 32 and valve body 6 to enter the engaged configuration. This is because when this movement occurs, the latches 2 push distally on the latch piston 32 until the hook portions 132 pass over the flange 106.

[00109] As better seen in FIGS. 2 and 3, each latch 2 defines opposed latch proximal and distal portions 144 and 146, and a latch intermediate portion 148 extending therebetween. The latch proximal portion 144 defines a latch proximal end surface 150 and a latch proximal portion outer lateral surface 152, typically extending substantially perpendicularly thereto. The latch distal portion 146 defines a latch distal end surface 156 and a latch distal portion inner lateral surface 158, extending for example substantially parallel to the latch proximal portion outer lateral surface 152. The latch intermediate portion 148 may take the form of a generally elongated portion of the latch 2 that extends at an acute angle relative to the latch proximal portion outer lateral surface 152. The latch 2 is rotatable relative to the main body 64. To that effect, the latch 2 is mounted to a latch pin 20 extending therethrough in the latch intermediate portion 148.

[00110] Each latch 2 is movable between the latch retracted position, shown in FIG. 3 for example, and a latch extended position, shown in FIG. 2 for example. In the latch retracted position, the latch 2 is entirely, or almost entirely, contained in the main body 64. The latch 2 is then oriented so that the latch proximal end surface 150 is angled relative to a perpendicular to the longitudinal axis of the head assembly 50. In the latch extended position, the latch 2 is rotated relative to the latch retracted position so that the latch proximal end surface 150 is substantially perpendicular to the longitudinal axis of the head assembly 50 and the latch proximal end surface 150 protrudes from the body outer surface 12.

[00111] The latches 2 are in some embodiments configured and sized to achieve the latch retracted position under the action of the fluids on the latches 2 when the head assembly 50 is lowered in a fluid column. In other words, the latches 2 are configured so that when a fluid is moved towards the main body proximal end 66 relative thereto, both outside of the main body 64 and inside the axial passageway 84, the fluid exerts a net torque on the latches 2 that is larger on the part of the latches 2 proximal to the latch pin 20 than on the part of the latches 2 distal to the latch pin 20.

[00112] Returning to FIG. 1 , the head assembly 50 also typically includes a spearhead point 27 at the main body proximal end 66 and securable to an overshot 40 (seen partially in FIG. 13) in a conventional manner. A latch collar 24 is provided in the main body passageway 70. As better seen in FIG. 4, the latch collar 24 defining collar latch slots 160 extending radially therethrough. The latch collar 24 is movable between latch collar proximal and distal positions, seen for example in FIGS. 5 and 13 respectively). When the latch collar 24 is in the latch collar distal position, the collar latch slots 160 are in register with the main body latch slots 72 and allow movement of the latches 2 between the latch extended and retracted position. When the latch collar 24 is in the latch collar proximal position, the latch collar 24 at least partially obstructs the main body latch slots 72 so that the latches 2 are constrained in the latch retracted position. [00113] Referring for example to FIGS. 1 , 4 and 5, the spearhead point 27 and the latch collar 24 are mechanically coupled to each other so as to be jointly movable axially relative to the main body 64. For example, the spearhead point 27 is secured to a spearhead base 23, provided distally relative thereto, which is itself mounted to a spearhead base housing 36 provided distally relative to the spearhead base 23. These elements may be secured to each other using pins 29 and 33.

[00114] In some embodiments, referring to FIG. 4, the spearhead base 23 is movable axially relative to the spearhead base housing 36 over a predetermined range of motion, for example by having the pin 33 mounted in a pair of diametrically opposed spearhead slots 200 receiving the pin 33. The spearhead base 23 has a portion thereof received in a spearhead passageway 202 formed in the spearhead base housing 36. The spearhead slots 200 extend from the spearhead passageway 202. The spearhead passageway 202 is terminated distally by a spearhead passageway end element 204 and a bumper 28 extends between the spearhead base 23 and the spearhead passageway end element 204. The bumper 28 is for example a resiliently deformable ring and serves to reduce the shock given when the overshot 40 lands on the spearhead point 27. The spearhead base housing 36 is coupled to the latch collar 24 through a coupling element 25. The spearhead base housing 36 is received axially slidably received in a guide 19 that is mounted in the main body 64 and prevented from moving proximally by a suitably shaped shoulder.

[00115] A latch collar biasing element 26 biases the latch collar 24 towards the latch collar distal position. The latch collar biasing element 26, for example a coil spring, extends between the latch collar 24 and a collar shoulder 162 defined in the guide 19 proximally to the latch collar 24 and facing distally. The latch collar biasing element 26 also pushes the guide 19 distally. The guide 19 is configured to ensure that the coupling element 25, main body second segment 3 and spearhead point 27 have suitable axial rotation properties for proper operation of the head assembly 50.

[00116] Referring for example to FIG. 1 , the head assembly 50 also includes a core stopper 18 at the main body distal end 68. The core stopper 18 abuts against the core to retrieve once the inner tube 39 is full. In some embodiments, the core stopper 18 is axially rotatable relative to the latches 2, for example through bearings 15, or suitable bushings. This reduces damages to the top portion of the core in typical operations. More specifically, the core stopper 18 is mounted to the main body fifth segment 17, which itself is rotatable about the spindle shaft 16, through bearings 15. The spindle shaft 16 is fixed to the main body fourth segment 5. If no rotatable element, such as the core stopper 37, were present, this could damage the core.

[00117] The head assembly 50 also includes many other conventional components. For example, a shut off 164 is provided distally to the main body valve apertures 1 14 valve for sealing passage of fluids between the head assembly 50 and the outer tube assembly 52 upon a predetermined shut off compression being exerted between the inner tube 39 and the head assembly 50. For example, the shut off 164 includes deformable rings 21 that expand radially outwardly when compressed axially. The rings 21 are coupled to the tube attachment 71 and core stopper 18 so that when the inner tube 39 is full, the shut off 164 is activated. Washers 22 may be provided between the deformable rings 21 to adjust their deformation. [00118] A spindle biasing element 7, for example a coil spring mounted on the spindle shaft 16, is mounted between a lock nut 37 provided at the distal end of the spindle shaft 16 and the proximal end of the main body fifth segment 17 and biases distally the main body fifth segment 17. When a proximally oriented force is exerted on the main body fifth segment 17, the latter moves on the spindle shaft 16 to compress the rings 21 and activate the shut off 164. Also, a seals, such as seal washer 38, may be provided between the bearing 15 and the spindle biasing element 7.

[00119] Operation of the head assembly 50 is now described with reference to the sequence of FIGS. 5 to 13. This operation supposes that this sequence has been performed many times before and that a new section of the drilling bore is to be drilled, with retrieval of the corresponding core. This description is also made supposing a surface operation with a downwardly oriented bore. Underground operation, with horizontal or upward drilling is discussed separately hereinbelow, as is operation in dry holes that cannot maintain a fluid column.

[00120] First, as seen in FIG. 5, the head assembly 50 and its attached inner tube 39 (not shown in FIG. 5) are thrown down in a fluid-filled bore hole, in the outer tube assembly 52 in a head assembly first configuration. The drill rods and outer tube assembly 52 may be filled with drilling fluid and/or subterranean water. These fluids slow down the downward movement of the head assembly 50 and the attached inner tube 39 . The head assembly 50 of the invention increases the descent rate when compared to existing drilling systems. Conventionally, water or drilling fluid is injected under pressure in the drill rods and outer tube assembly 52 from the bore hole origin with the head assembly 50 inserted therein. This operation is referred hereinbelow as "pumping". This moves the whole water column through the drill rods and outer tube assembly 52. In the present invention, the descent rate is increased for downwardly oriented bores as gravity further moves the head assembly 50 and inner tube 39 faster than the whole water column contained in the drill rods and outer tube assembly 52. This movement is facilitated by the axial passageway 84 which allows water and other fluids to flow through the head assembly 50.

[00121] Also, the latch piston 32 and valve body 6 are in the engaged configuration, which prevents the latch piston 32 from engaging the latches 2 as is is retained distally to the latches 2 by the valve body 6. The latches 2 are then free to achieve the latch retracted configuration. This eliminates friction between the latches 2 and the drilling rods and also reduces wear on the latches. Furthermore, the valve 82 is in the valve open configuration as fluid flow through the axial passageway 84 push the valve stop 8 against the stopper 1 12.

[00122] With reference to FIG. 6, once the head assembly 50 and attached inner tube 39 has reached its destination at the distal end of the outer tube assembly 52, the landing shoulder 4 abuts against the landing ring 62 and the latches 2 are in register with the latch seat 60. The operator continues pumping fluids downwardly from the surface, which pushes the valve stop 8 against the valve seat 1 10. By exerting a sufficient pressure, the latch piston 32 and valve body 6 achieve the disengaged configuration as the fluid pushes on the valve body 6 while the latch piston 32 is in the latch piston distalmost position, and therefore prevented from moving further distally by a suitably configured, shaped and positioned shoulder formed in the main body 64, while the valve body 6 can still move to a more distal position by compressing the valve body biasing element 34. [00123] Once the disengaged position is achieved, as seen in FIG. 7, the latch piston biasing element 1 1 pushes on the latch piston 32 proximally until the latter engages the latches 2 and pushes the latches 2 to the latch extended configuration through sliding of the latch distal portion 146 on the piston cam surface 92. Also, since the valve 82 is in the valve closed configuration and since the valve body apertures 1 16 are distal to the main body valve apertures 1 14, there is a relatively large resistance to passage of fluids at the head assembly, which registers as a persistent high pressure signal in the pumping system used to pump the fluids. This indicates to the operator the head assembly has reached the position where drilling can resume. This persistent high pressure signal is advantageous as it is difficult to miss, as opposed to conventional transient high pressure signals.

[00124] Then, as seen in FIG. 8, the operator stops pumping, which allows the valve body biasing element 34 to push the valve body 6 to the valve body proximalmost position. The latch piston 32 remains disengaged from the valve body 6 as the flange 106 is then too proximal to the valve body 6 to allows the hook portions 132 to reach the flange 106.

[00125] Subsequently, as seen in FIG. 9, pumping is resumed, which pushes the valve body 6 to the valve body register position, in which drilling fluids can exit the head assembly 50 laterally to reach the drill bit. Since the fluids can exit at the main body valve apertures 1 14, no pressure differential is created and the valve body 6 remains at the valve body register position. Subsequently, drilling can start. During the drilling operation, the core will enter the inner tube 39 (shown in FIG. 10). [00126] When the inner tube 39 is full, the core pushes on the core stopper 18, which activates the shut offs 164, thereby blocking the cross-section of the outer tube assembly 52, as seen in FIG. 10. This increases the pressure at the pump as the fluid is then no longer allowed to easily reach distally to the head assembly 50. This again provides a persistent pressure signal signaling to the operator that drilling is to be stopped and that retrieval of the head assembly 50 may start. Because of this high pressure, the valve body 6 is then moved to the valve body distalmost position.

[00127] To release the shut offs 164 and break the core from the bottom of the bore, the operator will pull slightly on the whole drill string, which will remove the pressure exerted on the core stopper 18, to achieve the configuration of FIG. 1 1 . Stopping pumping then allows the valve body 6 to reach the valve body proximalmost position under the action of the valve body biasing element 34, as seen in FIG. 12.

[00128] Finally, as seen in FIG. 13, the overshot 40 is lowered in a conventional manner to latch to the spearhead point 27. Pulling on the spearhead point 27 causes the latch collar biasing element 26 to be compressed and moves the latch collar 24 to the latch collar proximalmost position, thereby moving the latches 2 to the latch retracted position. This in turn pushes the latch piston 32 distally until the engaged configuration is achieved. This automatically rearms the head assembly 50 so that the head assembly 50 is immediately reusable once the core has been removed. This is advantageous as in conventional drilling equipment, drillers often forget to reset the head assembly to a configuration required for proper operation after a core has been retrieved. [00129] Referring to FIG. 19, if desired, a seal 44 can be provided between the head assembly 50 and the outer tube assembly 52 to allow conventional underground operation. For example, a removable resiliently deformable seal 44 is mounted to the main body 64 proximal to the main body valve aperture 1 14, for example in an annular groove 35 formed in the main body 64, and thus allows switching between surface and underground operations easily.

[00130] Referring to FIG. 18, in some embodiments, the main body 64 defines at least one, and typically a plurality of, main body bypass aperture 170 extending substantially radially between the main body outer surface 48 and the main body passageway 70 distal to the latch piston 32. The head assembly further includes a dry hole adapter 41 mountable to the main body 64 distal to the latch piston 32 with the valve body 6 removed from the head assembly 50. The dry hole adapter 41 defines at least one, and typically a plurality of, dry hole adapter bypass aperture 174 extending substantially radially in register with the main body bypass apertures 170 and a dry hole adapter passageway 176 extending between the dry hole adapter bypass aperture 170 and the latch piston passageway 88. The dry hole adapter passageway 176 defines a neck 178 and the dry hole adapter passageway 176 contains an adapter biasing element 42, for example a coil spring, distal to the neck 178. The neck 178 and adapter biasing element 42 are configured and sized so that when fluids are pumped though the dry hole adapter 41 in a distal direction, the valve stop 8 is maintained in the neck 178 by the adapter biasing element 42 and substantially obstructs passage of fluid through the neck 178 until a predetermined fluid pressure differential across the dry hole adapter 41 is achieved. Therefore, a sizable fluid column can be accumulated above the head assembly in cases in which leaks prevent such a fluid column to be accumulated naturally. Once the fluid column has reached a sufficient height, the fluid can flow through the dry hole adapter 41 to allow drilling for a set period of time. Changing the adapter biasing element 42 for one having a different stiffness allows to obtain different fluid column heights.

[00131] Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims. Also, the head assembly 50 presented in the present document have many features that do not all require to be implemented in all devices according to the invention.

Claims

WHAT IS CLAIMED IS: l. A head assembly for supporting an inner tube usable to retrieve a core sample and releasably latching in a latch seat provided in an outer tube assembly of a drill string, the head assembly comprising:

- a substantially elongated main body defining

- a main body outer surface;

- substantially axially opposed main body proximal and distal ends;

- a main body passageway extending substantially axially therethrough between the main body proximal and distal ends;

- a tube attachment at the main body distal end for attaching the inner tube thereto; and

- a main body latch slot extending between the main body passageway and main body outer surface, the main body latch slot being substantially elongated and substantially axially extending;

- a latch pivotably mounted at the main body latch slot so as to be pivotable about a latch pivot axis, the latch pivot axis extending across the main body latch slot circumferentially relative to the main body, the latch being movable between a latch extended position wherein a latch radially outwardmost portion of the latch protrudes radially outwardly from the main body and a latch retracted position wherein the latch radially outwardmost portion is radially inwardly located relative to a position of the latch radially outwardmost portion in the latch extended position;

- a latch actuator mounted to the main body and operatively coupled to the latch for selectively moving the latch from the latch retracted position to the latch extended position;

- wherein the head assembly defines an axial passageway extending therealong between the main body distal and proximal ends to allow fluids to move through the axial passageway between the main body distal and proximal ends with the fluids remaining inside the head assembly.

The head assembly as defined in claim 1 , further comprising a valve for selectively at least partially obstructing the axial passageway.

The head assembly as defined in claim 1 , further comprising a valve for selectively substantially obstructing the axial passageway.

The head assembly as defined in claim 3, wherein the valve includes

- a valve body provided in the main body passageway and defining a valve body passageway extending axially therethrough, the valve body passageway defining part of the axial passageway, the valve body defining a valve seat around the valve body passageway;

- a valve stop movable axially along the valve body passageway; and

- a stopper provided proximally relative to the valve seat and extending across the axial passageway for preventing movements of the valve stop proximally to the stopper;

- wherein, when the valve stop is withdrawn from the valve seat, the valve is in a valve open configuration allowing passage of fluids axially therethrough, and when the valve stop is seated on the valve seat, the valve is in a valve closed configuration substantially preventing passage of fluids therethrough.

The head assembly as defined in claim 4, wherein the valve stop is smaller than a cross-section of the axial passageway at the stopper to allow passage of fluids around the stopper when the valve stop abuts against the stopper.

The head assembly as defined in claim 4 or 5, wherein - the main body defines a main body valve aperture extending between the main body passageway and main body outer surface;

- the valve body defines a valve body aperture extending substantially radially therethrough from the valve body passageway;

- the valve body is movable between valve body proximalmost and distalmost positions wherein the valve body aperture is respectively proximal and distal relative to the main body valve aperture.

The head assembly as defined in claim 6, wherein the valve body is also movable to a valve body register position wherein the valve body aperture and the main body valve aperture are substantially in register with each other.

The head assembly as defined in any one of claims 1 to 7, wherein the latch actuator includes a latch piston provided distally relative to the latch, the latch piston being movable between a latch piston distalmost position and a latch piston proximalmost position, wherein, in the latch piston distalmost position, the latch piston is spaced apart from the latch so that the latch is movable between the latch extended and retracted positions, and in the latch piston proximalmost position, the latch piston engages the latch and pushes the latch to the latch extended position.

The head assembly as defined in claim 8, wherein the latch is freely movable between the latch extended and retracted positions when the latch piston is in the latch piston distalmost position.

The head assembly as defined in claims 8 or 9, wherein the latch piston defines a latch piston passageway extending axially therealong and defining part of the axial passageway, the latch piston being terminated proximally by a piston cam surface extending across the latch piston passageway and engaging the latch in the latch piston proximalmost position, the piston cam surface being provided with at least one cam surface aperture extending therethrough forming part of the latch piston passageway.

The head assembly as defined in any one of claims 1 to 10, wherein the latch is configured and sized to achieve the latch retracted position under the action of the fluids on the latch when the head assembly is lowered in a fluid column.

The head assembly as defined in any one of claims 1 to 1 1 , wherein in the latch retracted position, the latch is completely withdrawn inside the main body latch slot.

The head assembly as defined in any one of claims 1 to 12, further comprising a spearhead point at the main body proximal end securable to an overshot.

The head assembly as defined in claim 13, further comprising a latch collar provided in the main body passageway, the latch collar defining a collar latch slot extending radially therethrough, the latch collar being movable between latch collar proximal and distal positions, wherein, in the latch collar distal position, the collar latch slot is in register with the main body latch slot and allows movement of the latch to the latch extended position and, in the latch collar proximal position, the latch collar at least partially obstructs the main body latch slot so that the latch is constrained in the latch retracted position.

The head assembly as defined in claim 14, wherein the spear head point and the latch collar are mechanically coupled to each other so as to be jointly movable axially relative to the main body upon the spearhead point being moved proximally.

The head assembly as defined in claim 15, further comprising a latch collar biasing element biasing the latch collar towards the latch collar distal position.

The head assembly as defined in any one of claims 13 to 16, wherein the spearhead point is movable axially over a predetermined movement range relative to the main body, a resiliently deformable bumper being provided between spearhead point and the main body to absorb overshot landing shocks on the spearhead point.

The head assembly as defined in any one of claims 1 to 17, wherein the main body defines at least three main body latch slots each extending between the main body passageway and main body outer surface, each of the main body latch slots being substantially elongated and substantially axially extending and wherein a latch is pivotably mounted at each of the main body latch slots so as to be pivotable about a respective latch pivot axis, each latch pivot axis extending across the respective one of the main body latch slots circumferentially relative to the main body.

The head assembly as defined in claim 1 , further comprising

- a valve for selectively substantially obstructing the axial passageway, the valve including

- a valve body provided in the main body passageway and defining a valve body passageway extending axially therethrough, the valve body passageway defining part of the axial passageway, the valve body defining a valve seat around the valve body passageway, the valve body being movable between valve body proximalmost and distalmost positions along the main body passageway; and

- a valve stop movable axially along the valve body passageway;

- wherein, when the valve stop is withdrawn from the valve seat, the valve is in a valve open configuration allowing passage of fluids axially therethrough, and when the valve stop is seated on the valve seat, the valve is in a valve closed configuration substantially preventing passage of fluids therethrough;

- a stopper provided proximally relative to the valve seat and extending across the axial passageway for preventing movements of the valve stop proximally further than the stopper, the valve stop and stopper being configured and sized for allowing passage of fluids around the valve stop when the valve stop abuts against the stopper; and

- a latch piston mounted in the main body passageway distally to the latches and defining part of the axial passageway, the latch piston defining latch piston proximal and distal ends, the valve body being provided at the latch piston distal end, the latch piston being movable between latch piston proximalmost and distalmost positions along the main body passageway, wherein, in the latch piston distalmost position, the latch piston is spaced apart from the latch so that the latch is movable between the latch extended and retracted positions, and in the latch piston proximalmost position, the latch piston engages the latch and pushes the latch to the latch extended position;

- the valve body and latch piston being movable between an engaged configuration and a disengaged configuration, wherein, in the engaged configuration, the valve body and latch piston are secured to each other and prevented from moving axially from each other beyond a predetermined distance, and, in the disengaged configuration, the valve body and latch piston are movable independently from each other along the main body passageway further away than the predetermined distance.

The head assembly as defined in claim 19, wherein the stopper is provided in the latch piston.

The head assembly as defined in claim 19 or 20, wherein the valve body defines axially opposed valve body proximal and distal ends, the valve seat being provided at the valve body distal end.

The head assembly as defined in any one of claims 1 9 to 21 , wherein, in the engaged configuration, the latch piston is maintained distal to the latch piston proximalmost position by the valve body.

The head assembly as defined in any one of claims 1 9 to 21 , wherein, in the engaged configuration, the valve body is maintained proximal to the valve body distalmost position by the latch piston.

The head assembly as defined in any one of claims 1 9 to 21 , wherein, in the engaged configuration, the latch piston is maintained distal to the latch piston proximalmost position by the valve body and the valve body is maintained proximal to the valve body distalmost position by the latch piston.

The head assembly as defined in claim 24, wherein the latch piston and valve body are configured and sized to that

- the disengaged configuration is achieved from the engaged configuration when a predetermined axial tension is exerted between the latch piston and valve body; and - the engaged configuration is achieved from the disengaged configuration when a predetermined axial compression is exerted between the latch piston and valve body.

The head assembly as defined in claim 25, wherein

- one of the latch piston and valve body defines a resiliently deformable tongue having a hook portion; and

- an other one of the latch piston and valve body defines a hook receiving portion for releasably receiving the hook portion;

- wherein, in the engaged configuration, the hook portion is received by the hook receiving portion, and, in the disengaged configuration, the hook portion is outside of the hook receiving portion;

- the valve body and latch piston being configured and sized so that passage between the engaged and disengaged configurations occurs through deformation of the tongue to allow movements of the hook portion and hook receiving portion relative to each other.

The head assembly as defined in claim 26, wherein the hook receiving portion defines a flange, the hook being raised over the flange through deformation of the tongue when moving between the engaged and disengaged configurations.

The head assembly as defined in any one of claims 25 to 27, further comprising a latch piston biasing element biasing the latch piston towards the latch piston proximalmost position and a valve body biasing element biasing the valve body towards the valve body proximalmost position.

The head assembly as defined in claim 28, wherein in the engaged configuration with the valve body in the valve body proximalmost position, the latch piston is disengaged from the latch.

The head assembly as defined in claim 28 or 29, wherein in the engaged configuration with the valve body in the valve body proximalmost position, the latch piston is between the latch piston proximalmost and distalmost positions.

The head assembly as defined in any one of claims 28 to 30, wherein in the disengaged configuration, the latch piston is moved to the latch piston proximalmost position by the latch piston biasing element.

The head assembly as defined in any one of claims 28 to 31 , wherein

- the main body defines a main body valve aperture extending between the main body passageway and main body outer surface;

- the valve body aperture being respectively proximal and distal relative to the main body valve aperture in the valve body proximalmost and distalmost positions.

The head assembly as defined in claim 32, wherein in the engaged configuration, the valve body aperture is in register with the latch piston so that the latch piston obstructs the valve body aperture, and, in the disengaged configuration, the latch piston is movable to be withdrawn from the valve body aperture.

The head assembly as defined in claim 33, wherein the valve body is also movable to a valve body register position wherein the valve body aperture and the main body valve aperture are substantially in register with each other. The head assembly as defined in claim 34, wherein the latch piston, valve body and valve stop are configured and sized so that in the engaged configuration, creating a predetermined fluid pressure differential between the main body proximal and distal ends with a higher pressure at the main body proximal end causes the valve to achieve the valve closed configuration and to exert the predetermined axial tension to cause the latch piston and valve body to achieve the disengaged configuration, thereby

- allowing movement of the latch piston towards the latch piston proximalmost position;

- causing a resistance to pumping of the fluids in a distal direction through the axial passageway.

The head assembly as defined in any one of claims 28 to 35, further comprising a shut off provided distally to the main body valve aperture for sealing passage of fluids between the head assembly and the outer tube assembly upon a predetermined shut off compression being exerted between the inner tube and the latch.

The head assembly as defined in any one of claims 28 to 36, wherein the latch piston and valve body are configured and sized so that with no fluid pressure differential exerted between the main body proximal and distal ends, moving the latch to the latch retracted position causes the latch piston and valve body to enter the engaged configuration.

The head assembly as defined in any one of claims 25 to 37, wherein the predetermined axial tension is larger than the predetermined axial compression. The head assembly as defined in any one of claims 18 to 38, wherein the main body defines a main body bypass aperture extending between the main body outer surface and the main body passageway distal to the latch piston, the head assembly further comprising a dry hole adapter mountable to the main body distal to the latch piston with the valve body removed from the head assembly, the dry hole adapter defining a dry hole adapter bypass aperture extending in register with the main body bypass aperture and a dry hole adapter passageway extending between the dry hole adapter bypass aperture and the latch piston passageway, the dry hole adapter passageway defining a neck and the dry hole adapter passageway containing an adapter biasing element distal to the neck, the neck and adapter biasing element being configured and sized so that when fluids are pumped though the dry hole adapter in a distal direction, the valve stop is maintained in the neck by the biasing element and substantially obstructs passage of fluid through the neck until a predetermined fluid pressure differential across the dry hole adapter is achieved, at which point the valve stop moves distal to the neck to allow fluids to exit through the bypass apertures.

The head assembly as defined in any one of claims 1 to 39, wherein the main body defines a landing shoulder for abutting on the landing ring.

The head assembly as defined in any one of claims 1 to 40, further comprising a removable resiliently deformable seal mounted to the main body for sealing against the outer tube assembly.

The head assembly as defined in any one of claims 1 to 41 , wherein the head assembly includes a core stopper at the main body distal end, the core stopper being axially rotatable relative to the latch.

43. The head assembly as defined in claim 1 , wherein the head assembly is configure and sized so that in operation, after throwing down the head assembly in a fluid column while pumping fluid, landing the head assembly while continuing pumping causes a persistent increase in resistance to pumping that results in a persistent increase in pressure in the fluid column.