GB2595257A - Bolt tensioner - Google Patents

Abstract

The bolt tensioner 1 has a body 10, and a bolt coupling (50, Figure 6) receivable within the body, for connecting to a bolt (100, Figure 8) to be tensioned. The body has a hydraulic piston (20, Figure 4) for applying a tensioning force to the bolt coupling. A moveable barrier 40 is configured, in at least one orientation or position, to restrict removal of the bolt coupling from the body. The bolt tensioner thus reduces the risk of injury due to bolt coupling fracture. The barrier may be connected to the body by one or more pivots and may be moveable between an operative and one or more non-operative positions. The bolt tensioner may include a fluid port 30 for connecting to a hydraulic fluid hose and a moveable cover portion 41 to obstruct access to the fluid port. A bolt coupling (50, Figure 7) for use in a bolt tensioner includes a shaft 51 with an internal screw thread for engaging an external screw thread on a bolt to be tensioned. A flange portion 52 extends radially from the shaft. The bolt coupling comprises a frangible portion, 55 or 56, defining a preferential break line.

Description

Bolt Tensioner

Field of Invention

This invention relates to the field of bolt tensioners for high performance bolting operations.

Background

Torque wrenches and bolt tensioners are two competing tools for use in applications which require components to be bolted together and withstand high loads and stresses. It is generally accepted that bolt tensioners are the preferred option for applications requiring high tension loads within the bolt and when a higher degree of precision is required with respect to the loading applied to the bolt. For example, when the loading on the bolt (or the tool itself) approaches the failure point (e.g. the yield stress) of the material of the bolt or tool, it is critical not to over-tension the bolt.

Conventional bolt tensioners use hydraulic pistons to apply a tensioning force, which 'stretches' the bolt while a nut is wound along the bolt to its tightened position. In order to provide the high forces required to tension large bolts, the pistons are powered by high pressure hydraulic pumps, often operating at 1500 bar. Although the technology is well established, there are inherent risks to any system operating at such high pressures, and even more so when used to apply forces to components near their failure limits. Should a component fail, whether in the tool or the bolt, the result can be very dangerous to the tool operators nearby, as well as potentially causing damage to the construction itself.

The present invention attempts to resolve and/or ameliorate one or more of the problems with existing bolt tensioners and/or provide a valuable alternative.

Summary of Invention

According to a first aspect of the invention, there is provided a bolt tensioner. The bolt tensioner may comprise a body. The bolt tensioner may comprise a bolt coupling. The bolt coupling may be receivable within the body. The bolt coupling may be for connecting to a bolt to be tensioned. The body may comprise a hydraulic piston. The hydraulic piston may be for applying a tensioning force to the bolt coupling. The bolt tensioner may comprise a moveable barrier. The moveable barrier may be configured, in at least one orientation or position, to restrict removal of the bolt coupling from the body.

The invention is particularly advantageous, since should the material forming the bolt or bolt coupling fail during a bolt tensioning operation, the barrier can prevent or reduce the damage caused by the bolt or bolt coupling (or pieces thereof) being thrown from the bolt tensioner.

The body may be annular. The hydraulic piston may be annular and configured to be located within the wall of the body. The body and the piston may form a load cell. The hydraulic piston may comprise at least a portion of the upper surface of the body and/or bolt tensioner. The body may define a channel extending therethrough. The bolt coupling may be locatable within or partially within the channel. The body may comprise a bridge portion configured to extend over or past a nut engaged with the bolt to be tensioned. The bridge portion may be for supporting the device on a surface comprising the bolt to be tensioned. The bridge may be integrally formed in the body e.g. the load cell and bridge portion may be of the monobody type. In alternative embodiments, the bridge may be a separate component connectable to the body of the invention.

In some embodiments, the hydraulic piston and the bolt coupling are discrete components. Such embodiments are desirable since they permit easy replacement of the bolt coupling. In alternative embodiments, the hydraulic piston and the bolt coupling may be integrally formed with each other i.e. the bolt coupling may be received within the body and a hydraulic force applied directly to a surface of the bolt coupling.

The bolt tensioner may be a single-stage type bolt tensioner, wherein the bolt is brought to the desired tension in a single operation. The bolt tensioner may comprise a multi-stage type bolt tensioner, wherein the bolt is brought to the desired tension in a series of increasing steps. The bolt tensioner may be configured to receive hydraulic fluid from a conventional hydraulic pump. The bolt tensioner may be configured to receive fluid pressure at or above 1200 bar e.g. 1300 bar, 1350 bar, 1400 bar, 1450 bar, 1500 bar, 1550 bar, 1600 bar or higher. In some embodiments, the bolt tensioner may be configured to operate at pressures above 1600 bar. Configuring the bolt tensioner to receive fluid pressure at approximately 1500 bar is advantageous, since many hydraulic pumps are available on the market and can output this pressure.

In some embodiments, the bolt tensioner may be a multi-stud type i.e. the bolt tensioner may be configured to engage more than one bolt simultaneously. For example, the body may comprise more than one channel and bolt coupling. The bolt tensioner may comprise a hydraulic piston per bolt coupling. In embodiments wherein the bolt tensioner is a multi-stud type, the barrier may be configured to restrict removal of one or more of the bolt couplings from the body. In some embodiments, more than one barrier may be provided.

The moveable barrier may be pivotable and/or may be connected to the body by one or more pivots. Moving the barrier may comprise pivoting the barrier. The barrier may pivot about a pivot axis perpendicular to the axis of the bolt and/or bolt coupling.

In some embodiments, the barrier comprises a hinge or pivot allowing the barrier to be pivotable. Alternatively, the barrier may be connected to the body by a hinge or by a fastener around which the barrier can rotate, such as a bolt, screw, rivet or other mechanical fastener. Alternatively, the barrier may be integrally formed with the body such as via additive manufacturing. For example, the barrier or body may comprise a pin retained within the other of the barrier or body.

The barrier may be moveable between an operative and one or more non-operative positions. The operative position may be the position in which the barrier restricts removal of the bolt coupling from the body.

When in the operative position, the barrier may be positioned axially of the bolt coupling. For example, the barrier may be positioned above the bolt coupling in use. The axial direction may correspond to the axial length of the bolt to be tensioned. In the operative position, the barrier may be spaced apart from, but aligned with, the bolt coupling.

Preferably, the barrier will be spaced apart by a distance less than the length of the bolt coupling. For example, should the bolt coupling be moved axially, it cannot be removed from the body when the barrier is in the operative position.

When in the non-operative position, the barrier may be offset laterally from the axis of the bolt coupling. In the non-operative position, the barrier may not restrict removal of the bolt coupling from the body. For example, in the or a non-operative position, the barrier may be positioned away from the axis of the bolt coupling.

In alternative embodiments, the barrier may pivot about a pivot axis parallel to the axis of the bolt coupling and or bolt to be tensioned. For example, the barrier may be rotatable from a position extending over the bolt coupling to a position extending away from the axis of the bolt coupling.

The barrier may be configured to operate as a handle e.g. for carrying or lifting the bolt tensioner.

In some embodiments, the barrier may comprise an arm or a clip e.g. engageable with or above the bolt coupling. In some embodiments, the barrier may comprise a plate, ring or grid and may be locatable adjacent to the bolt coupling. The plate, ring, or grid may be extend perpendicularly to the axis of the bolt coupling when the barrier is in the operative position. The barrier may have a width greater than the corresponding dimension of the bolt coupling. The barrier may have a length (i.e. a dimension perpendicular to the width) greater than the corresponding dimension of the bolt coupling. The barrier may have a radius greater than the radius of the bolt coupling.

The body may comprise one or more detents or indexing means. The detent or indexing means may be configured to engage the barrier when in the operative position, and/or resist movement of the barrier away from the operative position. The detent or indexing means thus provides a simple mechanism by which a user can feel whether the barrier is correctly aligned for use and/or prevent the barrier accidentally being knocked out of alignment. The detent or indexing means may resist movement of the barrier into the operative position. The detent or indexing means may thus require the user to consciously put the barrier into position prior to use, and thus prevent the use of the bolt tensioner unless the barrier is correctly positioned.

The one or more detent or indexing means may be configured to engage the barrier when the barrier is in a non-operative position. For example, the detent may be configured to engage the barrier when the barrier does not prevent removal of the bolt coupling. This provides a feedback mechanism for an operator to know when the barrier is positioned to allow de-installation of the bolt tensioner.

The one or more detent or indexing means may be configured to engage the barrier when the barrier is positioned to extend laterally and/or obliquely from the body. The detent may be configured so that the barrier engages with an adjacent bolt tensioner. For example, the barrier may be positioned so that it is aligned with the bolt coupling of an adjacent bolt tensioner and prevents the removal of a bolt coupling therefrom. Optionally, the barrier may be connectable to an adjacent barrier or body portion.

The barrier and or detent may comprise a locking mechanism to lock the barrier in a position as described herein.

The one or more detents or indexing means may comprise a groove or recess in the body. The groove or recess in the body may be configured to receive a portion of the barrier therein when the barrier is aligned with the groove or recess. Moving the barrier out of the operative position may comprise moving the barrier out of the groove or recess. Such embodiments provide a form of haptic feedback for users. In alternative embodiments, the detent or indexing means may comprise one or more projections or ridges over which a portion of the barrier rides.

The barrier may comprise a U-shaped arm. The barrier may be pivotably connected to the body at first and second positions on opposite sides of the body. The first and second positions on the body may define a pivot axis which extends perpendicularly to the axis of the bolt coupling. The barrier may be pivotably connected to the body adjacent to the upper end of the body, and/or adjacent to the bolt coupling. The U-shaped barrier may be configured so that the base of the U is located axially above the bolt coupling when the barrier is in the operative position.

The bolt coupling may comprise a shaft. The shaft may comprise an internal screw thread for engaging an external screw thread on a bolt to be tensioned. The bolt coupling may comprise a flange portion extending radially from the shaft. The body may comprise a channel extending therethrough for receiving the shaft of the bolt coupling therein. The hydraulic piston may be configured to apply a force to the flange of the bolt coupling in use. The flange may comprise a mating surface for engaging the hydraulic piston. Some embodiments may comprise more than one flange as described herein.

In some embodiments, the bolt coupling may be configured to clamp onto the bolt to be tensioned. For example, the bolt coupling may comprise a plurality of gripping jaws or arms, engageable with a bolt. In such embodiments, the bolt coupling may comprise a mating surface for engaging the hydraulic piston, or for directly receiving a hydraulic force from a hydraulic fluid in embodiments wherein the piston and bolt coupling are integrally formed.

The bolt coupling may comprise a frangible portion. The frangible portion may define a preferential break line The frangible portion may be located at or adjacent the flange portion and/or between the shaft and the flange portion. In some embodiments, the frangible portion may be located within the flange portion. The frangible portion may be located between the threaded region and the mating surface.

The frangible portion may be configured so that when the bolt coupling breaks (e.g. along the preferential break line) a portion remains engaged with the bolt to be tensioned. In such embodiments due to the high stresses involved, should the bolt coupling fracture, the portion in contact with the hydraulic piston will be thrown from the shaft portion. Since the barrier is configured to restrict removal of the bolt coupling in the operative position, the fractured bolt coupling portion will hit the barrier and thus will not be thrown clear of the tool where it could harm an operator.

The bolt coupling may comprise a circumferential ridge extending around the outer surface of the shaft. The circumferential ridge may be located on the shaft side of the bolt coupling with respect to the frangible portion. The body may comprise an annular ridge extending around the internal surface of the channel. The annular ridge may be configured to engage the circumferential ridge of the bolt coupling. For example, the circumferential ridge on the bolt coupling may have a greater diameter than the internal diameter defined by the annular ridge within the channel. Thus, the bolt coupling can be prevented from moving past the annular ridge of the body. In some embodiments, the circumferential ridges may comprise a further flange or a shoulder between different diameter regions of the bolt coupling.

In some embodiments, the circumferential ridge may be continuous or segmented. In alternative embodiments, the circumferential ridge may be replaced with one or more projections or shoulders performing the same function as the circumferential ridge.

The circumferential ridge of the bolt coupling may be located between the flange of the bolt coupling and the annular ridge of the channel. When the bolt coupling fails and breaks at the frangible portion, there is no longer a compressive force acting upon the piston and body from the flange of the bolt coupling to force it against the surface holding the bolt. Thus, the bolt tensioner would jump or be thrown from the surface due to the significant forces involved. In embodiments as described herein, when the bolt coupling breaks, the shaft portion remains threaded onto the thread of the bolt and is retained in position. Thus, the circumferential ridge of the shaft is retained in position, and the annular ridge is prevented from passing over the circumferential ridge. Thus, the body of the tool is prevent from rising away from the surface. Damage to the tool can be avoided or minimised and the risk to the operator is drastically reduced.

In second aspect of the invention, there is provided a bolt tensioner. The bolt tensioner may comprise a body. The body may comprise a channel. The bolt tensioner may comprise a bolt coupling for connecting to a bolt to be tensioned. The bolt coupling may be receivable within the channel. The bolt coupling may comprise a shaft and a flange. The body may comprise a hydraulic piston. The hydraulic piston may be for applying a tensioning force to the bolt coupling. The bolt coupling may comprise a circumferential ridge extending around the outer surface of the shaft. The body may comprise an annular ridge extending around the internal surface of the channel. The annular ridge may be configured to engage the circumferential ridge of the bolt coupling.

The bolt tensioner according to the first and second aspects of the invention may further comprise a fluid port for connecting to a hydraulic fluid hose. The bolt tensioner may comprise a moveable cover portion. The moveable cover portion may be configured, in at least one orientation or position, to obstruct access to the fluid port.

According to a further aspect of the invention, there is provided a bolt tensioner. The bolt tensioner may comprise a body. The body may comprise a hydraulic piston. The bolt tensioner may comprise a fluid port for connecting to a hydraulic fluid hose. The bolt tensioner may comprise a moveable cover portion. The moveable cover portion may be configured, in at least one orientation or position, to obstruct access to the fluid port.

By selectively restricting access to the hydraulic fluid port, it is possible to prevent operation of the bolt tensioner unless the cover is appropriately positioned. The cover can be operatively linked to other features of the bolt tensioner in order to prevent the cover from being moved from an obstructing position or removed unless the bolt tensioner is correctly set up.

According to any of the above aspects of the invention, the cover may be moveable between an operative and one or more non-operative positions. The operative position of the cover may be when the cover does not obstruct access to the fluid port. The non-operative position of the cover may be when the cover obstructs access to the fluid port.

The cover may rotatable. The cover may be rotatable about an axis parallel to the pivot axis of the barrier. The cover may be rotatable about an axis parallel to the axis of the fluid port and/or perpendicular to the axis of the bolt coupling. The cover may be connected to a handle, such as a carrying handle, such that moving the handle rotates the cover.

The cover may comprise an aperture for a hydraulic fluid hose to extend through. The cover may be configured so that when in the operative position, the aperture is axially aligned with the fluid port. The cover may be configured such that a hydraulic fluid hose extends through the aperture when connected to the fluid port. Such embodiments are advantageous, since the position of the hose may prevent the cover from rotating out of the operative position. The cover may comprise a plate or disc. The cover may be a U or C-shaped plate.

In some embodiments, the cover may rotate or pivot about an eccentric axis, such that rotation of the cover reveals/conceals the fluid port.

The cover may be connected to the barrier such that moving the barrier causes movement of the cover.

The cover may be configured so that when the barrier is in the operative position, the cover is in the operative position. With both the barrier and the cover in the operative positions, access to the fluid port is not restricted and the barrier restricts removal of the bolt coupling from the body. Thus, the bolt tensioner can be used safely. This configuration prevents the bolt tensioner from being operated by preventing the connection of a hydraulic fluid hose until the barrier is in the operative position.

The cover may be provided on or connected to the barrier. The cover may be offset from the barrier e.g. the cover may comprise an arm or linkage connecting the cover to the barrier. The arm or linkage may be configured to extend past or beyond the fluid port, such that the cover is positionable in front of the fluid port. The barrier and cover may be configured so that moving (e.g. rotating/pivoting) the barrier moves (e.g. rotates/pivots) the cover. Thus the barrier cannot be disengaged or removed until after the hose is disconnected, allowing the cover to move, and the bolt tensioner is safe to remove from the bolt.

The bolt tensioner may further comprise a curved or annular shim. The curved or annular shim may be connectable to the body. The shim and body may each comprise corresponding curved or tapered seating surfaces such that they form a ball joint.

The ball joint configuration is advantageous, since the shim and body are able to move relative to one another e.g. angularly. In some situations the bolt to be tensioned may be angled relative to the surface in which it is located, rather than precisely perpendicular. Applying a perpendicular force to an angled bolt thus risks creating imbalanced loadings within the bolt and the bolt tensioner, which can cause the bolt or tool to fail. The shim and body configuration thus allows for relative movement to compensate for the misalignment of the bolt. The curved or annular shim may be or comprise a foot portion configured to bear against a surface comprising a bolt to be tensioned. The bolt tensioner can thus apply an axial force to the bolt which is angled relative to the surface containing said bolt.

In one series of embodiments, the curved or annular shim is connected to the body by one or more of: mechanical fasteners (such as bolts or cap screws), magnets, interlocking features, a tubular sheath or housing or any other suitable means. The curved or annular shim is connected to allow relative movement of the shim and body.

The curved or annular shim may be sacrificial and/or replaceable. For example, the shim may comprise a material weaker than the body, thus ensuring that the shim breaks preferentially. Expensive damage to the body is thus avoided.

In some embodiments, the curved or annular shim may be formed integrally with the body, such as via additive manufacturing.

The body may comprise a cavity for receiving a nut rotation socket. The cavity may have at least one open end for locating over a bolt to be tensioned. The shim may be connectable to the body at the open end of the cavity. The shim may be configured to retain a nut rotation socket within the cavity. In some embodiments, the shim and nut may be replaceable such that different sizes of nut and shim can be used with a single size of body to improve adaptability. In some embodiments, the bolt tensioner may comprise a powered nut drive mechanism for driving the rotation of the nut once the bolt has been tensioned. The powered nut drive mechanism may be hydraulic, pneumatic, mechanical and/or electromechanical, and may be computer controlled and/or automatic.

According to a further aspect of the invention, there is provided a bolt coupling for use in a bolt tensioner. The bolt coupling may comprise a shaft comprising an internal screw thread for engaging an external screw thread on a bolt to be tensioned. The bolt coupling may comprise a flange portion extending radially from the shaft. The bolt coupling may comprise a frangible portion defining a preferential break line.

The frangible portion may be located at or adjacent the flange portion and/or between the shaft and the flange portion. The bolt coupling may comprise a circumferential ridge or projection extending from the outer surface of the shaft. The bolt coupling may be configured for use in a bolt tensioner as previously described. The bolt coupling may have any of the features previously described.

In some embodiments, the bolt tensioner may comprise a piston retraction mechanism. The piston retraction mechanism may comprise a spring assembly connecting the body and the piston. The piston retraction mechanism may comprise a pneumatic port and pathway configured to apply a pneumatic force to the piston. The piston retraction mechanism may be configured to apply a force to the piston in the opposite direction to the hydraulic force. The piston retraction mechanism may be integrally formed in the body and/or with the piston. In alternative embodiments, the piston retraction mechanism may be connectable to the body and/or the barrier.

In some embodiments, the bolt tensioner may comprise a bolt coupling wind-down mechanism, configured to drive the bolt coupling such that it engages the bolt. The bolt coupling wind-down mechanism may comprise a mechanism for rotating the bolt coupling such that the internal thread on the bolt coupling engages the thread on the bolt. The bolt coupling wind-down mechanism may comprise a wheel or gear configured to engage a corresponding wind-down surface on the bolt coupling. The wind-down surface may be, for example, toothed, splined or knurled. The bolt coupling wind-down mechanism may be integrally formed in the bolt tensioner or it may be connectable to the bolt tensioner e.g. it may be connectable to the barrier to allow for easy alignment with the bolt coupling and for simple installation/removal.

Brief Description

Embodiments of the invention will now be described, by way of example only, with reference to the following drawings, in which: Figure 1 is a perspective view of a bolt tensioner; Figures 2 and 3 are end-on and side-on views of the bolt tensioner of Figure 1; Figure 4 is a cross section taken through the bolt tensioner of Figure 1 in the plane AA; Figure 5 is a perspective view of a bolt tensioner in use; Figure 6 is a perspective view of a bolt coupling; Figure 7 is a cross-section through the bolt coupling of Figure 6 in the plane B-B; and Figure 8 is a cross-section in a vertical plane through a bolt tensioner in use.

Specific Description

The invention is illustrated in the Figures of the accompanying drawings, which are meant to be exemplary and not limiting, in which like references are intended to refer to like or corresponding parts.

Figures 1 to 4 show a bolt tensioner 1 in perspective view, end-on, side-on and in cross-section respectively. The bolt tensioner 1 has a generally cylindrical body 10 which has a channel 11 extending through the centre thereof. The body 10 is provided with a piston 20 and a hydraulic fluid port 30. The body 10 is connected to a moveable barrier 40. A bolt coupling 50 is located within the channel 11.

In conventional bolt tensioners as known in the art, the bolt tensioner would comprise a load cell comprising the piston, and would be combined with or connected to a bridge which extends over the nut and bolt to be tightened, such that the bridge sits on a flat surface surrounding the nut. In contrast. the body 10 is of the monobody design, and thus acts as both the load cell and the bridge.

The moveable barrier 40 is an inverted U-shaped arm comprising a pair of supports 40a and a connecting beam 40b. The barrier 40 has a round cross-section and can be solid or hollow. In alternative embodiments (not shown) the barrier is formed from a tube with a square cross-section. The supports 40a are connected to the upper end of the body 10 on opposite sides thereof. The barrier 40 is pivotably connected to the body 10 via mechanical fasteners (not shown) of any suitable type, such as bolts, screws or rivets. In some embodiments (not shown), the barrier may be integrally formed with the body.

The barrier 40 is rotatable around a pivot axis which extends between two connections 44, 45, as shown by the dashed arrows C in Figure 2. The pivot axis is shown as line DD in Figure 3. This configuration means the barrier 40 can be connected securely to the body 10 and the barrier 40 can thus act as a carrying handle. To pivot the barrier 40, the operator applies a lateral force to the barrier to 'fold' it away i.e. move the barrier to the side/laterally of the bolt coupling 50. The body 10 immediately adjacent to the connections 44, 45 has grooves formed therein (not shown), which act as a detent or indexing means for the movement of the barrier 40. This prevents the barrier from being accidentally knocked out of position, and also provides positive feedback to an operator, who is able to feel when the barrier is in an operative position.

Extending from the barrier 40 is a cover 41 connected by an arm 43. The arm is configured so that the cover 41 is positioned axially in front of the fluid port 30. The cover 41 is disc shaped and has an aperture 42 extending therethrough. In Figure 2, the barrier 40 and the cover 41 are in their respective operative positions. As shown, in the operative position, the aperture 42 is aligned with the fluid port 30, such that an operator can connect a hose to the fluid port through the aperture 42. The cover 41 is attached to the barrier 40 such that the pivoting movement C of the barrier 40 causes the cover 41 to rotate, as shown by the dashed line E, moving the aperture 42 out of alignment with the fluid port 30. When unaligned in the non-operative position, fluid port 30 is blocked by the region of the cover 41 adjacent to the aperture 42. Thus, in the non-operative position, the operator is unable to connect a hose to the fluid port 30, and operation of the bolt tensioner is prevented. The cover 41 as shown is a C-shaped plate or disc, although other shapes are envisaged within the scope of the present invention. The axis of rotation of the cover 41 is the same as the pivot axis D-D, and thus the cover 41 rotates slightly eccentrically. The eccentricity is configured so that when in the non-operative position, the cover 41 still blocks access to the fluid port 30.

With reference to Figure 4, the body 10 and piston 20 are annular in shape, extending around the channel 11. The lower region of the channel 11 opens into a cavity 12 which is a wider region of the channel and which has an annular recess 14 in the inner surface for housing a Nut Rotation Socket (NRS) 13. The NRS 13 is annular with a cylindrical outer surface and a hexagonal internal surface for closely fitting with a hexagonal nut. The NRS 13 has a series of radial NRS apertures 13a for receiving a tool (such as a tommy bar) for driving the rotation of the NRS 13 and thus the nut. The NRS apertures 13a may be offset and/or eccentric i.e. they may be located away from the centre of each face on the internal surface of the NRS 13 and/or they may be angled such that they do not intersect at the geometric centre of the NRS 13. The annular recess 14 is capped by a shim 15 to retain the NRS 13 within the recess 14 and cavity 12.

With additional reference to Figure 5, the shim 15 is annular and connected to the lower end of the body 10 by mechanical fasteners (not shown). The shim 15 has a flat (planar) surface 16 which acts as a foot for the bolt tensioner, and a curved mating surface 17 which aligns with a similarly curved mating surface 18 of the body 10. The shim 15 is able to move angularly relative to the body 10 as shown by the arrow F, such that they form a partial ball joint. Figure 5 shows a bolt tensioner installed on a surface defined by the line H-H, wherein the bolt has an axis defined by line G-G which is not perpendicular to the surface. The shim 15 allows the bolt tensioner 1 to sit securely on a surface with the body 10 at a slight angle, should a bolt be misaligned (e.g. not perpendicular) with the surface. In such circumstances, the bolt tensioner is able to provide an axial tensioning force to the bolt i.e. in the axis G-G, without requiring the bolt to be perpendicular to the surface. In situations wherein the bolt is not perpendicular to the surface and there is no shim 15, it is possible for uneven strain to develop within the tool and the bolt, increasing the fatigue experienced by the tool and potentially causing failure of the tool or bolt. Thus, by providing the shim 15, such increased strain is avoided and the lifetime of the tool is greatly improved, as well as reducing the risk of the tool or bolt breaking.

With additional reference to Figures 6 and 7, the bolt coupling 50 is received within the channel 11 in the body 10. The bolt coupling 50 has a T-shaped cross-section and comprises a shaft 51 and a flange 52. The flange 52 extends radially and perpendicularly from the shaft 51 and extends over the piston 20 located within the walls of the body 10. The shaft 51 is tubular and has an internal screw thread (not shown). The flange 52 is provided with a series of apertures 53 which are arranged radially of the shaft, around the circumference of the flange 52. The apertures 53 extend into the flange 52 and are configured to receive a tool, such as a tommy bar or another suitable lever, in order to drive the rotation of the bolt coupling 50 and engage the internal screw thread of the shaft 52 with a corresponding screw thread on a bolt to be tensioned.

The shaft 51 has a circumferential ridge 54 located part way along its length. The circumferential ridge 54 thus divides the shaft 51 into upper and lower shaft portions 51a, Sib respectively. The upper shaft portion 51a has a larger diameter with respect to the lower shaft portion 51b, such that the circumferential ridge 54 forms a shoulder. In alternative embodiments (not shown), the upper and lower shaft portions may have the same diameter and the circumferential ridge comprises a projection extending radially from the shaft 51.

As shown in Figure 4, the body 10 has an annular ridge 19 extending around the internal surface of the channel 11. The annular ridge 19 is configured to have an inner diameter with approximately the same diameter as the lower shaft portion 51b and configured to allow the lower shaft portion 51b to pass, but not permit the circumferential ridge 54 or the upper shaft portion 51a to pass. In the embodiment shown, the flange 52 sits on the piston 20 and also prevents the bolt coupling 50 from passing further into the body 10.

The bolt coupling 50 may be frangible. In Figure 7, there are shown two exemplary locations for a frangible portion in the bolt coupling 50, although a number of alternative positions could be used. The dashed line 55 denotes a first location wherein a frangible portion may be provided. Similarly, the dashed lines 56 denote an alternative annular frangible portion extending between the shaft 51 and the flange 52. The frangible portions can be of any suitable form, such as a groove or discontinuity extending around the bolt coupling, which would create a preferential break line. Should the force within the bolt coupling 50 exceed its material limits, the position at which the bolt coupling breaks is thus easily controlled and predetermined.

Typically, since bolt couplings are relatively cheap to produce compared to the rest of the bolt tensioner, it is desirable to produce them from a material weaker than the body and piston 20 such that the bolt coupling breaks first and can be replaced without damaging the rest of the tool. In such cases, failure of the bolt coupling typically consists of the bolt coupling stretching plastically and safely. To avoid plastic failure of the bolt coupling occurring in operations requiring very high bolt tension, stronger materials and/or heat treated materials can be used. However, such materials are typically far more brittle and, instead of plastically deforming, are prone to shearing and fracturing. The high forces involved often mean that pieces of the fractured bolt coupling can be violently thrown from the tool, endangering operators nearby.

With additional reference to Figure 8, there is shown a bolt tensioner in use on a nut 200 and bolt 100, wherein the bolt coupling 50 has fractured along the frangible portion denoted by line 55 in Figure 7. The bolt tensioner 1 thus has two main advantages. Firstly, should a bolt coupling fracture, as shown in Figure 8, the barrier 40 is located axially above the bolt coupling 50 and prevents the broken pieces from flying away from the tool. Secondly, the frangible portion within the bolt coupling 50 means that the failure will happen at a position whereby the flange 52 and shaft 51 shear apart. Once broken, the shaft 51 remains engaged with the bolt 100 via their respective screw threads. During the tensioning operation, the flange 52 is providing a reactive force against the piston 20 and body 10. When the flange 52 shears, there is no downward force acting on the bolt tensioner, which would jump, potentially harming an operator and damaging the tool. In the embodiment shown, the circumferential ridge 54 of the shaft 51 is fixed in position by its engagement with the bolt 100. This prevents the body 10 from rising upwards beyond the circumferential ridge 54 and being thrown from the surface, thus further improving the safety of the operator. Thus, it is possible to use stronger materials for the bolt coupling 50 without risking the safety of the operator.

In the Figures 1 to 8 there is shown a single size of bolt tensioner. Multiple sizes of body, and corresponding bolt couplings and NRSs, may be provided in order to securely connect with different sizes of bolts. A small range of body sizes can be further adapted to fit a wide range of bolts by providing a range of bolt couplings and NRSs to fit each size of body.

In alternative embodiments (not shown), the barrier may be configured to be connected to the body by a single connection. For example, the pivot axis of the barrier may be parallel to the axis of the bolt coupling 50 and/or channel 11. For U-shaped barriers such as barrier 40, the non-pivoting free end may be lockable to the body by a catch or fastener. Alternatively, the barrier may have a single support and beam, such as an L-shape.

In alternative embodiments (not shown), the cover may comprise a disc or plate without an aperture. For example, the cover may be rotatable, and have an eccentric rotational axis, such the rotating the cover conceals/reveals the fluid port 30. In embodiments where the barrier has a pivot axis parallel to the axis of the bolt coupling 50, the cover may comprise one or more arms which extend from the barrier to a position in front of the fluid port when the barrier is in the non-operative position.

The function of the bolt tensioner will now be described with reference to Figures 1 to 8.

In order to tension a bolt (such as bolt 100 in Figure 8), the bolt coupling 50 would be separated from the body 10. Using the barrier 40 as a handle, an operator is able to locate the bolt tensioner 1 over a bolt and nut (such as nut 200 in Figure 8) such that the nut 200 is located within the NRS 13 and the shaft of the bolt 100 extends up through the channel 11. The shim 15 acts as a foot and contacts the surface containing the bolt.

To connect the tool 1 to the bolt, the bolt coupling 50 must then be connected. First, the barrier 40 is moved to a non-operative position by the operator pushing the barrier laterally so that it rotates in the direction C and no longer lies axially above the channel 11. The bolt coupling 50 is then inserted into the channel and wound onto the bolt until the flange 52 contacts the piston 20. While the barrier 40 is in the non-operative position, the cover 41 is rotated in the direction E such that a fluid hose cannot be connected to the bolt tensioner 1. The operator subsequently raises the barrier 40 back into its operative position as shown in Figure 1 whereby it is retained in position by the detent in the body. Rotating the barrier 40 causes the cover 41 to rotate, revealing the fluid port 30 through the aperture 42. The operator can then connect a fluid hose to the fluid port and perform a tensioning operation. The cover 41 thus prevents pressurising of the piston 20 until after the barrier 40 has been positioned for operation. Once the bolt is tensioned, the nut can be wound down by inserting a lever into the NRS and rotating the NRS and nut. Once the nut is sufficiently tightened, the hydraulic pressure can be released and the piston reset. The fluid hose can be removed, the barrier 40 lowered into a non-operative position and the bolt coupling unwound from the bolt.

The barrier 40 and the cover 41 thus each prevent mishandling of the bolt tensioner by an operator, thereby improving the safety of the device over existing bolt tensioners.

Claims (24)

1. CLAIMS: 1. A bolt tensioner comprising: a body; a bolt coupling, receivable within the body, for connecting to a bolt to be tensioned; wherein the body comprises a hydraulic piston for applying a tensioning force to the bolt coupling; and a moveable barrier configured, in at least one orientation or position, to restrict removal of the bolt coupling from the body.
2. The bolt tensioner according to claim 1, wherein the barrier is pivotable and/or is connected to the body by one or more pivots.
3. 3. The bolt tensioner according to any one of the preceding claims, wherein the barrier is moveable between an operative and one or more non-operative positions.
4. 4. The bolt tensioner according to claim 3, wherein when in the operative position, the barrier is positioned axially of the bolt coupling.
5. The bolt tensioner according to claim 3 or 4, wherein when in the non-operative position, the barrier is offset laterally from the axis of the bolt coupling.
6. 6. The bolt tensioner according to any one of claims 3 to 5, wherein the body comprises a detent or indexing means configured to engage the barrier when in the operative position, and/or resist movement of the barrier away from the operative position.
7. 7. The bolt tensioner according to claim 6, wherein the detent or indexing means comprises a groove or recess in the body, configured to receive a portion of the barrier therein when the barrier is aligned with the groove or recess, and wherein moving the barrier out of the operative position comprises moving the barrier out of the groove or recess. 9. 10. 11. 12. 13. 14. 15.
8. The bolt tensioner according to any one of the preceding claims, wherein the barrier comprises a U-shaped arm, pivotably connected to the body at first and second positions on opposite sides of the body.
9. The bolt tensioner according to any one of the preceding claims, wherein the bolt coupling comprises: a shaft comprising an internal screw thread for engaging an external screw thread on a bolt to be tensioned, and a flange portion extending radially from the shaft, and wherein the body comprises a channel extending therethrough for receiving the shaft therein.
10. The bolt tensioner according to any one of the preceding claims, wherein the bolt coupling comprises a frangible portion defining a preferential break line.
11. The bolt tensioner according to claims 9 and 10, wherein the frangible portion is located at or adjacent the flange portion and/or between the shaft and the flange portion.
12. The bolt tensioner according to any one of claims 9 to 11, wherein the bolt coupling comprises a circumferential ridge or projection extending from the outer surface of the shaft, and wherein the body comprises an annular ridge extending around the internal surface of the channel, configured to engage the circumferential ridge of the bolt coupling.
13. The bolt tensioner according to any one or the preceding claims, further comprising a fluid port for connecting to a hydraulic fluid hose; and a moveable cover portion configured, in at least one orientation or position, to obstruct access to the fluid port.
14. The bolt tensioner according to claim 13, wherein the cover is rotatable between an operative and one or more non-operative positions.
15. The bolt tensioner according to any one of claims 13 to 14, wherein the cover is rotatable. 16. 17. 18. 19. 20. 21. 22. 23.
16. The bolt tensioner according to any one of claims 13 to15, wherein the cover comprises an aperture for a hydraulic fluid hose to extend through.
17. The bolt tensioner according to claim 14 and 16, wherein the cover is configured so that when in the operative position, the aperture is axially aligned with the fluid port.
18. The bolt tensioner according to any one of claims 13 to 18, wherein the cover is a U or C-shaped plate.
19. The bolt tensioner according to any one of claims 13 to 18, wherein the cover is connected to the barrier such that moving the barrier causes movement of the cover.
20. The bolt tensioner according to any one of the preceding claims, further comprising a curved or annular shim connectable to the body, wherein the shim and body each comprise corresponding curved or tapered seating surfaces such that they form a ball joint.
21. The bolt tensioner according to claim 20, wherein the body comprises a cavity for receiving a nut rotation socket, and the cavity having at least one open end for locating over a bolt to be tensioned, and wherein the shim is connectable to the body at the open end of the cavity and configured to retain a nut rotation socket within the cavity.
22. A bolt coupling for use in a bolt tensioner, wherein the bolt coupling comprises: a shaft comprising an internal screw thread for engaging an external screw thread on a bolt to be tensioned, a flange portion extending radially from the shaft, wherein the bolt coupling comprises a frangible portion defining a preferential break line.
23. The bolt coupling according to claim 24, wherein the frangible portion is located at or adjacent the flange portion and/or between the shaft and the flange portion.
24. 24. The bolt coupling according to either claim 22 or 23, comprising a circumferential ridge or projection extending from the outer surface of the shaft.