GB2530318A

GB2530318A - Drill bit retention sleeve and chuck for a percussive drill

Info

Publication number: GB2530318A
Application number: GB1416606.0A
Authority: GB
Inventors: Adam Baker; Neil Woollen; Jamie Atkin
Original assignee: Halco Rock Tools Ltd
Current assignee: Halco Drilling International Ltd
Priority date: 2014-09-19
Filing date: 2014-09-19
Publication date: 2016-03-23
Also published as: GB201416606D0

Abstract

A drill bit retention system for a percussive drill 10 comprising a chuck 12 and retention sleeve 11. The chuck 12 and the retention sleeve 11 comprise first co-operating engagement means 44, such that when the retention sleeve 11 and chuck 12 are engaged the retention sleeve and chuck are constrained to rotate together in at least one direction. The first cooperating engagement means 44 may be a raised diameter portion 49 formed by a shoulder 48 of the chuck 12 with an external screw thread 47 to co-operate with an internal screw thread 63 on the retention sleeve 11. The engagement means may also be splines (Fig 8, 64) on the sleeve that interlocks with recesses (Fig 8, 67) formed between external rounded splines (Fig 8, 66) on the chuck 12. The system further comprises housing 13, with engagement means 19 for securing to the chuck; and a drill bit 22 mounted in the sleeve and chuck, with third engagement means 43 between the chuck 12 and drill bit 22 and fourth engagement means 59 between drill bit 22 and retention sleeve 11.

Description

DRILL BIT RETENTION SLEEVE AND CHUCK FOR A PERCUSSIVE DRILL

Technical Field

This disclosure is directed towards a drill bit

retention system for a percussive drill, comprising a drill bit chuck and a drill bit retention sleeve.

Background

Percussive drills may be used in the drilling of bore holes in a hard material, such as soil and/or rock, particularly in the fields of deep well and exploration drilling (for example for oil and gas) . The percussive drill may comprise a drill bit having a head in contact with the material for boring a hole therethrough. A percussive mechanism or hammer may be provided for applying successive blows to a rear end of the drill bit and a rotation arrangement may also be provided for rotating the drill bit.

As the hole becomes deeper, a number of extensions, known as drill pipes, may be connected to upper end of the hammer such that it can still be operated at depth.

However, the successive blows by the hammer to rear of the drill bit may cause the drill bit to fracture, which is known as "shanking" in the art. If the drill bit does fracture then part of the drill bit may remain in the bore hole and the operator may need to retrieve the fractured part from the bottom of the bore hole before drilling can continue. Such retrieval, known as "fishing", may be extremely difficult with deep boreholes and may consume valuable operating time.

For these reasons a drill bit catohing arrangement may be provided to catch any fractured part of the drill bit as the percussive hammer is withdrawn from the bore hole. One such drill bit catohing arrangement is disolosed in US-B- 8312613. The percussive drill comprises a housing member formed as a hollow tube having an internal thread at an end.

A driver sub, also known as a chuck, is also formed as a hollow tube and comprises an external thread mated with the internal thread of the housing member. An external shoulder is also provided around the periphery of the chuck. The comprises a number of axially extending internal splines which mate with external splines on the shank of the drill bit. The shank of the drill bit extends into the housing member and the head of the drill bit extends away from the housing member and chuck. The drill bit comprises an external thread on the back of the head. A tubular retaining member or catcher shroud is provided around both the chuck and drill bit. An internal thread of the retaining member is mated to the external thread of the drill bit and an inward shoulder of the retaining meirher engages the external shoulder of the chuck.

Typically, if the drill bit shanks, it will fracture on the inner side of the drill bit head and through the shank. If the drill bit shanks it may be retained in the percussive drill upon removal from a borehole due to the engagement between the drill bit, retaining member, chuck and housing member. However, if the drill bit is fractured entirely across the shank it may be very difficult to remove the chuck from the housing member.

Summary

The present disclosure provides a drill bit retention system for a percussive drill, the system comprising a chuck and a retention sleeve, wherein the chuck and the retention sleeve comprise first co-operating engagement means such that when the retention sleeve and chuck are engaged the retention sleeve and chuck are constrained to rotate together in at least one direction.

By way of example only, embodiments of a drill bit retention sleeve for a percussive drill, a drill bit chuck for a percussive drill and a percussive drill comprising said drill bit retention sleeve and drill bit chuck are now described with reference to, and as shown in, the accompanying drawings.

Brief Description of the Drawings

Figure 1 is a perspective view of a percussive drill of

the present disclosure;

Figure 2 is a cross-sectional perspective view of the percussive drill of Figure 1; Figure 3 is a cross-sectional side elevation of the percussive drill of Figures 1; Figure 4 is a perspective view of a drill bit of the percussive drill of Figure 1; Figure 5 is a cross-sectional side elevation of a chuck and a retention sleeve from the percussive drill of Figures 1; Figure 6 is a perspective view of the chuck of Figure 5; Figure 7 is a perspective view of the retention sleeve of Figure 5; Figure 8 is a cross-sectional side elevation of a further embodiment of the percussive drill of the present

disclosure;

Figure 9 is a cross-sectional side elevation of a chuck and a retention sleeve from the percussive drill of Figures 8; Figure 10 is a perspective view of the retention sleeve of Figure 9; and Figure 11 is a perspective view of the chuck of Figure 9.

Detailed Description

The present disclosure is generally directed towards a drill bit retention system including a retention sleeve (also known as a "bit catcher") and a chuck for a percussive drill. The retention sleeve is engaged with the chuck in a manner which prevents relative rotation therebetween in at least one direction.

Figures 1 to 3 illustrate an embodiment of a percussive drill 10 comprising a retention sleeve 11, a chuck 12 and a housing 13. The percussive drill 10 may be a "down the hole" (DTH) percussive drill 10. The housing 13 may comprise a housing member 14, which may be tubular, having an internal surfaoe 15, an external surface 16, a first housing end 17 and a second housing end 18. During operation of the percussive drill 10 the second housing end 18 may be located distally from the operator towards the bottom of the borehole. The first housing end 17 may be located proximally to the operator towards the upper end, or above the opening, of the borehole.

The housing 13 may further oomprise a housing engagement means 19 for securing the chuck 12 to the housing 13. The housing engagement rreans 19 may comprise an internal screw thread 20 forced in the internal surface 15 at the second housing end 18.

The percussive drill 10 may further comprise a hammer arrangement 21 provided within the housing 13 for applying repeated blows to a drill bit 22. The hammer arrangement 21 may be of any suitable type known in the art and, for example, may comprise a pistcn 23 pneumatically driven by an actuator 24. The actuator 24 may be driven by an external power source (not shown in the Figures) , for example compressed air or hydraulic fluid. An adaptor 25 located at the first housing end 17 may provide the means for connection to the power source.

The drill bit 22 (see Figures 2, 3 and 4) may comprise a head 26 located towards a distal first drill bit end 27 and a shank 28 towards a proximal second drill bit end 29.

The piston 23 may be arranged to impact upon the second drill bit end 29. The head 26 may comprise a cutting surface extending around the first drill bit end 27 for boring holes or the like in a material. The first drill bit end 27 may be located at the extremity of the percussive drill 10 and may be located at the bottom of a hole during the operation of the percussive drill 10. As illustrated, the diameter of the head 26 may be larger than the diameter of the shank 28 such that a shoulder 31 is provided therebetween. A first drill bit engagement means 32 may be provided on the head 26 and cay be adjacent to the shoulder 31. The first drill bit engagement means 32 may be separated from the cutting surface 30 by an intermediate portion 33, which may be a substantially smooth cylindrical surface. The first drill bit engagement means 32 may comprise an external screw thread 34 extending arcund the circumference of the head 26.

A second drill bit engagement means 35 (see Figure 4) may be provided on the shank 28. The second drill bit engagement means 35 may comprise a plurality of external splines 36 extending axially (i.e. parallel to the central axis of the drill bit 22 between the first and second ends 27, 29) along the shank 28 from the head 26. The external splines 36 may extend along approximately one third of the length of the drill bit 22 and may not extend all the way along the shank 28. An end pcrtion 37, which may be substantially cylindrical with varying diameters along its length, may be provided along the shank 28 between the second drill bit engagement ireans 35 and the second drill bit end 29.

As illustrated in further detail in Figures 5 and 6, the chuck 12 may comprise a chuck member 38, which may be tubular. The chuck member 38 may have a first chuck member end 39 and a second chuck member end 40 and may have a chuck member internal surface 41 and a chuck member external surface 42. The chuck member 38 may be chamfered between the first and second chuck member ends 39, 40 and the chuck member internal surface 41 fcr assisting in the insertion of the drill bit 22 into the chuck 12 during assembly of the percussive drill 10. The chuck 12 may further comprise first and second chuck engagement means 43, 44.

The first chuck engagement means 43 may enable the drill bit 22 to be secured to the chuck member 38 by means of the second drill bit engagement means 35. The first chuck engagement means 43 may comprise a plurality of internal splines 45 on the chuck member internal surface 41 of the chuck member 38. The plurality of internal splines 45 may extend axially along approximately half of the length of chuck member 38 and may be arranged in close proximity to, but not directly adjacent to, the first chuck member end 39.

A relatively small portion 46 of around one-tenth of the length of the chuck member 38 may be provided on the chuck member internal surface 41 between the plurality of internal splines 45 and the first chuck member end 39. when the percussive drill 10 is assembled, the drill bit 22 may be located within the chuck member 38 such that the external splines 36 of the drill bit 22 mate with the internal splines 45 of the chuck 12. Therefore, the drill bit 22 and chuck 12 may be constrained to rotate together and during drilling, when the chuck 12 is secured to the housing 13, any rotation of the housing 13 may be transmitted to rotate the drill bit 22 via the chuck 12.

The second chuck engagement means 44 may enable the chuck member 38 to be secured to the retention sleeve 11 such that the chuck member 38 and retention sleeve 11 are constrained to rotate together in at least one direction.

The second chuck engagement means 44 may further prevent relative axial movement between the chuck member 38 and retention sleeve 11. The seccnd chuck engagement means 44 may comprise an external screw thread 47 extending around the chuck member external surface 42 and may be located adjacent to the first chuck member end 39. The second chuck engagement means 44 may further comprise a shoulder 48 on the chuck member external surface 42, thereby forming a second end portion 49 between the shoulder 48 and the second chuck member end 40. The external diameter of the chuck member 38 may be greater over the second end portion 49 than the rest of the chuck member 38. The external screw thread 47 may extend around this second end portion 49 of the chuck member 38.

The chuck 12 may comprise a third chuck engagement means 50 for securing the chuck 12 to the housing 13. The third chuck engagement means 50 may comprise an external screw thread 51 on the chuck member external surface 42. The external screw thread 51 may be separated from the shoulder 48 by an intermediate portion 52 of the chuck member external surface 42 and the major diameter of the external screw thread 51 may be slightly less than the external diameter of the intermediate portion 52. The external screw thread 51 may extend along over half or approximately five-eighths of the length of the chuck member 38. The external screw thread 51 may be separated from the first chuck member end 39 by a relatively small first end portion 53 of the chuck member external surface 42. The chuck member external surface 42 may have an external diameter which is approximately the same as the minor diameter of the external screw thread 51. When the percussive drill 10 is assembled, the third chuck engagement means 50 may be engaged with the housing engagement means 19, for example by screwing the aforementioned screw threads 20, 51 together.

The retention sleeve 11 may be connected to, and arranged to encapsulate, at least part of the chuck 12 and the drill bit 22. Thus, if the drill bit 22 shanks, the head 26 of the drill bit 22 will remain connected to the chuck 12 via the retention sleeve 11. The retention sleeve U may comprise a sleeve member 54, which may be tubular. The sleeve member 54 may extend from a first sleeve member end to a second sleeve member end 56 and may have a sleeve member internal surface 57 and a sleeve member external surface 58. Although illustrated as being formed of a single piece, the retention sleeve 11 may be formed by multiple connected pieces as is known in the art. For example, the retention sleeve 11 may be formed by two connected pieces, each having a semi-circular cross-section. The retention sleeve 11 may further comprise first and second sleeve engagement means 59, 60. L5

The first sleeve engagecent means 59 may enable the sleeve member 54 to be secured to the drill bit 22 and may comprise an internal screw thread 61 extending around the sleeve member internal surface 57. This internal screw thread 61 may be provided adjacent to the second sleeve member end 56 and may be arranged to engage with the first drill bit engagement means 32 during assembly.

The second sleeve engagement means 60 may enable the sleeve member 54 to be secured to the chuck 12 such that the chuck 12 and sleeve member 54 are constrained to rotate with one another in at least one direction. This engagement may further prevent relative axial movement between the sleeve member 54 and the chuck 12. The second sleeve engagement means 60 may comprise a shoulder 62 of reduced diameter on the sleeve member internal surface 57, substantially adjacent to the first sleeve member end 55, relative to the -10 -diameter of the rest of the sleeve member internal surface 57.

The second sleeve engagement means 60 may comprise an internal screw thread 63 extending around the sleeve member internal surface 57. This internal screw thread 63 may be located adjacent to the shoulder 62. The internal screw thread 63 may have the same form as the screw thread 61 of the first sleeve engagement means 59 such that the screw threads 63, 61 cooperate. As a result, when the chuck 12 is inserted into the retention sleeve 11 the shoulder 48 is sufficiently small enough that it can pass through the screw thread 61 of the first sleeve engagement means 59. Such a retention sleeve 11 has been found to be relatively simple to manufacture and relatively effective during use. An alternative may be for the shoulder 48 of the chuck 12 to be of a smaller diameter. A further alternative would be for the shoulder 62 of the retention sleeve 11 to be larger, which would result in a chuck 12 of greater structural strength.

During assembly of the percussive drill 10, the drill bit 22 may be inserted into the chuck 12 such that the first chuck engagement means 43 is engaged with the second drill bit engagement means 35 to fcrm third co-operating engagement means, for example by engaging the splines 36, 45. Subsequently, the retention sleeve 11 may be placed around the drill bit 22 and chuck 12 by inserting the second drill bit end 29 and first chuck member end 39 through the second sleeve member end 56. The first sleeve engagement means 59 may pass through the second chuck engagement means 44 by, for example, screwing the screw threads 61, 47 -11 -entirely through one another. The first sleeve engagement means 59 may then be engaged with the first drill bit engagement means 32 to form fourth oo-operating engagement means and subsequently disengaged by, for example, screwing the screw threads 34, 61 entirely through one another.

The drill bit 22 and chuck 12 may then be moved further along the retention sleeve 11 and the second chuck engagement means 44 engaged with the second sleeve engagement means 60 to form first co-operating engagement means, for example by screwing the screw threads 47, 63 together. The shoulder 48 of the second chuck engagement means 44 may be in contact with the shoulder 62 of the second sleeve engagement means 60. As a result, the chuck 12 and retention sleeve 11 will be constrained to rotate together in at least one direction. Finally, the retention sleeve 11, chuck 12 and drill bit 22 may be attached to the housing by engaging the third chuck engagement means 50 with the housing engagement means 19 to form second co-operating engagement means.

Figures 8 to 11 illustrate a further embodiment of the percussive drill 10 of the present disclosure. The same reference numerals have been used to denote the same features as in the first embcdiment. In this further embodiment the second sleeve engagement means 60 may comprise a plurality of internal splines 64 on the sleeve member internal surface 57. The internal splines 64 may be axially aligned to one another and spaced further apart from each other by a dimension greater than their width. The internal splines 64 may be provided on a raised inner annulus 65 extending around the sleeve member internal -12 -surface 57 towards the first sleeve member end 55 and adjacent to the shoulder 62. Each internal spline 64 may be rounded.

The second chuck engagerr.ent means 44 may comprise a plurality of external splines 66 separated by recesses 67, which may be provided around the second end portion 49 of the chuck member 38. The recesses 67 may be rounded to cooperate with the internal splines 64 of the retention sleeve 11.

During assembly of the second embodiment of the percussive drill 10, the drill bit 22 may be inserted into the chuck 12 such that the first chuck engagement means 43 is engaged with the second drill bit engagement means 35 to form third co-operating engagement means, for example by engaging the splines 36, 45. Subsequently, the retention sleeve 11 may be placed around the drill bit 22 and chuck 12 by inserting the second drill bit end 29 and first chuck member end 39 through the second sleeve member end 56. The first sleeve engagement means 59 may pass over the second chuck engagement means 44 by virtue of the outer diameter of the external splines 66 of the second chuck engagement means 44 being smaller than the internal diameter of the internal screw thread 61 of the first sleeve engagement means 59. The first sleeve engagement means 59 may then be engaged with the first drill bit engagement means 32 to form fourth co-operating engagement means and subsequently disengaged by, for example, screwing the screw threads 34, 61 entirely through one another.

-13 -The drill bit 22 and chuck 12 may then be moved further along the retention sleeve 11 and the second chuck engagement means 44 engaged with the second sleeve engagement means 60 to form first co-operating engagement means, for example by engaging the internal splines 64 of the second sleeve engagement means 60 with the external splines 66 and recesses 67 of the second chuck engagement means 44. The shoulder 48 of the second chuck engagement means 44 may be in contact with the shoulder 62 of the second sleeve engagement means 60. Therefore, the chuck 12 and sleeve member 54 are constrained to rotate together in either direction about the axis of the percussive drill 10.

Axial movement between the retention sleeve 11 and chuck 12 may be prevented by the shoulders 48, 62. Finally, the retention sleeve 11, chuck 12 and drill bit 22 may be attached to the housing by engaging the third chuck engagement means 50 with the housing engagement means 19 to form second co-operating engagement means.

As illustrated in Figures 2 and 3, when the percussive drill 10 is assembled and the drill bit 22 is in its operating position, the first drill bit engagement means 35 and first sleeve engagement ireans 59 may be positioned such that they do not mate when the drill bit 22 is fully inserted into the chuck 12. Thus the drill bit 22 may be able to move axially by a predetermined distance, the predetermined distance being defined as the distance between the first drill bit engagement means 35 and first sleeve engagement means 59 when the percussive drill 10 is assembled. However, the first drill bit engagement means 32 and first sleeve engagement ireans 59 may prevent axial movement of the drill bit 22 beyond a certain displacement.

-]_4 -For example, each of the aforementioned screw threads 34, 61 may act as opposing stop means or shoulders against one another to prevent the excessive axial movement.

Industrial Applicability

When the percussive drill 10 is operated the housing 13 may rotate and the hammer arrangement 21 may be engaged such that the cutting surface 30 cf the drill bit 22 cuts through the material to be drilled. The drill bit 22 may be designed such that if it shanks it will do so between the first drill bit engagement means 32 and the second drill bit end 29.

Thus, if shanking were to occur, the head 26 of the drill bit 22 may remain attached to the retention sleeve 11 by virtue of the contact between the first drill bit engagement means 32 and the first sleeve engagement means 59. However, the operator may need to remove the drill bit 22, the retention sleeve 11 and the chuck 12 from the housing 13 in order to replace the drill bit 22 before drilling can resume.

In prior art systems the retention sleeve and chuck may not be engaged to prevent relative rotation therebetween.

Therefore, the operator may have difficulty in removing the chuck from the housing as it is covered by the retention sleeve and, therefore, cannot be gripped for unscrewing from the housing. With the prior art systems the operator may have to mill off the retention sleeve in order to access the chuck so that it can be unscrewed from the housing. Whilst the retention sleeve is considered to be a disposable item in the art, the operator may damage the chuck, which is a non-disposable item, and this method adds unwanted delays to the drilling operation. Alternatively, the operator may

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apply a compressive force to the outside of the retention sleeve in order to grip the chuck underneath it. However, again, this may cause irreparable damage to the retention sleeve such that it must be replaced and may even result in the chuck needing to be replaced due to damage thereto.

With the chuck 12 and retention sleeve 11 of the present disclosure, in the event that shanking occurs, the operator is able twist the retention sleeve 11 and, due to the geometrically locked mating between the second sleeve engagement means 60 and second chuck engagement means 44, the chuck 12 will also rotate. Therefore, the chuck 12 may be rotated out of its threaded engagement with the housing 13 of the percussive drill 10. This enables the broken drill bit 22 to be removed and replaced.

In the first embodiment, the screw threads 47, 63 may prevent relative rotation between the retention sleeve 11 and chuck 12 in one direction. This direction may be the screw tightening direction, although if the screw threads 47, 63 are sufficiently tightened then relative rotation in both directions may be prevented. In addition, due to the tapered, self-centring function provided by the screw threads 47, 63, the mating of the chuck 12 and retention sleeve 11 may be relatively accurate. Furthermore, the screw threads 47, 63 have been found to effectively distribute stresses.

The interlocking splines 64, 66 of the second embodiment may prevent relative rotation between the retention sleeve 11 and chuck 12 in both directions. In addition, the splines 64, 66 may provide an increased ease -16 -of assembly and manufacture. Furthermore, the use of splines 64, 66 may reduce the opportunity for the second chuck engagement means 44 to beoome permanently engaged with the second sleeve engagement means 60.

Claims

--CLAIMS: 1. A drill bit retention system for a percussive driii, the system comprising a chuck and a retention sleeve, wherein the chuck and the retention sleeve comprise first co-operating engagement means such that when the retention sleeve and chuck are engaged the retention sleeve and chuck are constrained to rotate together in at least one direction.
2. A drill bit retention system as claimed in claim 1 wherein the first co-operating engagement means comprises engaged screw threads.
3. A drill bit retention system as claimed in claim 2 wherein the retention sleeve comprises a sleeve member and the chuck comprises a chuck member, the first co-operating engagement means comprising an internal screw thread on the sleeve member and an external screw thread on the chuck member.
4. A drill bit retention system as claimed in claim 1 wherein the first cc-operating engagement means comprises interlocking splines.
5. A drill bit retention system as claimed in claim 4 wherein the sleeve comprises a sleeve member and the chuck comprises a chuck member, the first cc-operating engagement means comprising a plurality of internal splines on the sleeve member and a plurality of external splines on the chuck member.

-18 -
6. A drill bit retention system as claimed in claim 5 wherein the external splines on the chuck member are rounded.
7. A percussive drill comprising an actuator for driving a drill bit and the drill bit retention system of any one of claims 1 to 6.
8. A percussive drill as claimed in claim 7 further comprising a housing, wherein the housing and the chuck comprise second co-operating engagement means such that when the housing and the chuck are engaged the housing and chuck are constrained to rotate together in at least one direction.
9. A percussive drill as claimed in claim 7 or claim 8 further comprising a drill bit mounted in the retention sleeve and the chuck, wherein the drill bit and the chuck comprise third co-operating engagement means such that when the chuck and the drill bit are engaged the chuck and the drill bit are constrained to rotate together in both directions.
10. A percussive drill as claimed in any one of claims 7 to 9 wherein the retention sleeve and drill bit comprise fourth co-operating engagement means which are arranged to engage during assembly of the retention sleeve and drill bit and which are disengaged when the drill bit is in its operating position, in which operating position said fourth co-operating engagement means form opposing stop means.