Hydraulic tensioning tool

Abstract

A hydraulic tensioning tool comprising: a housing; a puller bar located within the housing, wherein the puller bar has a proximal end having a first socket for securing to a fastener, and a distal end; and a reaction nut secured to the puller bar; wherein: the reaction nut comprises a recess and wherein the distal end of the puller bar is received within the recess.

Description

[0001] HYDRAULIC TENSIONING TOOL

[0002] TECHNICAL FIELD

[0003] The present Invention relates to a hydraulic tensioning tool, a hydraulic tensioning system, a method of tensioning a fastener, a method of assembling a hydraulic tensioning tool and a method of retro-fitting a hydraulic tensioning tool.

[0004] BACKGROUND

[0005] Hydraulic tensioning tools are known and are used to apply precise and uniform tension to bolts. The bolt typically comprises a conventional bolt having a hexagonal head and a cylindrical threaded shaft. A nut having an internal thread is threaded onto the (external) thread of the shaft of the bolt. The bolt and the nut together comprise a fastener which is used to secure a joint. The joint may comprise a joint between two flanges. For example, two cylindrical components having end flanges may be brought together with the flanges abutting each other, and a plurality of fasteners may be used to secure the two flanges together.

[0006] A known hydraulic tensioning tool comprises an annular jack with a hollow cylindrical internal bore. Hydraulic force is generated which is transferred into stretching the thread of a bolt. When the thread of the bolt is stretched, then the nut may be tightened to a precise tension easily and efficiently. One of the reasons why hydraulic tensioning tools are used is that they use significantly less energy to tighten the nut compared to, for example, using a torque wrench. It will be understood that one of the problems with using a torque wrench to tighten the nut of a bolt is that up to 80% of the applied energy may be wasted by the need to overcome friction. By contrast, known hydraulic tensioning tools are advantageous since they do not use torque to tighten the nut of a bolt at least in the sense that hydraulic tensioning tools do not require any forceful turning of the nut. As such, hydraulic tensioning tools are more energy efficient than using a torque wrench and allow a nut to be tightened quickly and in a controlled manner. Furthermore, as will discussed in more detail below, hydraulic tensioning tools can be linked together in order simultaneously to tighten the nuts of multiple fasteners which are being used to secure a joint.

[0007] The known hydraulic tensioning tool comprises a puller bar which has an internal thread. The internal thread of the puller bar is rotated onto the external thread of the shaft of a bolt. The thread of the shaft of the bolt secured to the puller bar is then pulled using hydraulic force in order to stretch the shaft of the bolt. The known hydraulic tensioning tool also comprises a bridge which has a socket for engaging with the nut of the bolt. The socket housed within the bridge is rotatable enabling the socket within the bridge to rotate and tighten the nut of the bolt whilst the bolt is being stretched. Accordingly, a precise amount of tension can be applied into a joint which the nut and bolt are being used to secure.

[0008] The known hydraulic tensioning tool comprises two axially stacked interlocking load cells. Each load cell comprises a body, a piston, an inner seal and an outer seal. The puller bar is connected to the load cells via a reaction nut. The puller bar has a drive socket located in an upper surface of the puller bar which enables a user to rotate the puller bar so as to thread the internal thread of the puller bar onto the external thread of the shaft of the bolt. Other hydraulic tensioning tools are known comprising more than two loadcells. For example, a known hydraulic tensioning tool comprises five axially stacked interlocking load cells.

[0009] The known hydraulic tensioning tool is useful for tightening bolts in various different fields. One particular application for hydraulic tensioning tools is in the field of wind turbines and other energy sector applications where small radial clearances are expected with no height limit. The known hydraulic tensioning tool produces a very high total load in parallel.

[0010] According to the known arrangement the reaction nut has a through bore and the reaction nut is screwed onto the puller bar. Accordingly, the puller bar may be translated by the load cells via the reaction nut which connects the load cells to the puller bar. The reaction nut and the puller bar are locked against relative rotation to each other by a set screw which prevents the reaction nut and the puller bar from becoming unwound from each other during use. During assembly a hole is drilled and tapped into both the reaction nut and the puller bar in order to accept a set screw on the pitch diameter of the thread. During use the set screw is loaded in shear across its length in order to resist any twisting forces developed between the reaction nut and the puller bar. As will be discussed in more detail, loading the set screw in shear is sub-optimal and a person skilled in the art will appreciate that the greater mechanical strength of the set screw lies in its ability to resist tensile force i.e. force directed along the longitudinal axis of the set screw.

[0011] It is also known to use an alternative arrangement to secure the reaction nut to the puller bar. According to the alternative arrangement a hole is drilled perpendicular to the pitch axis i.e. through the outside diameter of the reaction nut and into the puller bar. A set screw is then used to secure the reaction nut to the puller bar. However, with this arrangement the set screw is still loaded in shear during rotation.

[0012] It will be understood by those skilled in the art that with the known hydraulic tensioning tool that the puller bar and the associated reaction nut are paired items i.e. that they cannot be replaced individually. Accordingly, if either the puller bar or the reaction nut suffers damage or otherwise fails, then both the puller bar and the reaction nut need to be replaced. This is obviously both wasteful and equally a non-trivial problem as the replacement of both the puller bar and the reaction nut of the known hydraulic tensioning tools requires the use of a specialist field stripping tool. This is both expensive, time consuming and less than ideal.

[0013] Furthermore, a person skilled in the art will appreciate that using a set screw to secure the reaction nut to the puller bar is problematic since the set screw is particularly prone to becoming damaged. It will also be appreciated that the set screw will be loaded in direct shear i.e. a shear force which acts perpendicular to the longitudinal axis of the set screw. It will be understood that a set screw typically has a greater tensile strength than its shear strength i.e. set screws are best used to resist tensile forces along the longitudinal axis of the screw rather than to resist shear forces which act perpendicular to the longitudinal axis of the screw.

[0014] It is desired to provide an improved hydraulic tensioning tool.

[0015] SUMMARY

[0016] According to an aspect of the present invention there is provided a hydraulic tensioning tool comprising: a housing; a puller bar located within the housing, wherein the puller bar has a proximal end having a first socket for securing to a fastener, and a distal end; and a reaction nut secured to the puller bar; wherein: the reaction nut comprises a recess and wherein the distal end of the puller bar is received within the recess.

[0017] The recess may comprise a blind bore which extends only partially through a portion of the reaction nut.

[0018] The recess may comprise a partial bore which extends only partially through a portion of the reaction nut.

[0019] The hydraulic tensioning tool according to various embodiments is particularly advantageous compared to the known hydraulic tensioning tool for a number of reasons.

[0020] The hydraulic tensioning tool according to various embodiments comprises an elongated reaction nut having a recess (blind bore) which has an internal (female) thread. The distal end of the puller bar is arranged to have an external (male) thread and is screwed into the recess (blind bore) of the elongated reaction nut in order to secure the puller bar to the reaction nut. It will be appreciated that the known hydraulic tensioning tool has a reaction nut having a through bore which is threaded onto the puller bar and in contrast to embodiments of the present invention, the distal end of the conventional puller bar extends beyond the upper surface of the reaction nut. This is possible because the conventional reaction nut is screwed on to the distal end of the puller bar such that the distal end of the puller bar extends beyond an upper surface of the reaction nut.

[0021] One advantage of the reaction nut and puller bar arrangement according to various embodiments is that the reaction nut and the puller bar no longer form paired items i.e. if the puller bar becomes damaged or otherwise needs replacing then it can be replaced with needing to also replace the reaction nut (and vice versa).

[0022] In contrast, in the case of the known hydraulic tensioning tool, the reaction nut and the puller bar are paired items meaning that if either the reaction nut or the puller bar needs to be replaced, then this necessitates replacing both items i.e. if the puller bar becomes damaged, then this would also necessitate the replacement of the reaction nut.

[0023] It will be appreciated that this is both potentially wasteful but also problematic as a specialist field stripping tool is needed to remove both the puller bar and the reaction nut. In contrast, according to various embodiments, since the puller bar and the reaction nut are no longer paired items, then if the puller bar becomes damaged then it is only necessary to replace the puller bar - the elongated reaction nut according to various embodiments does not also need to be replaced at the same time.

[0024] As will be explained in more detail, the redesigned arrangement also has a number of further advantages over the known hydraulic tensioning tool. Accordingly, the hydraulic tensioning tool according to various embodiments represents a significant advance in the art.

[0025] The reaction nut may further comprise a through bore which extends fully through a portion of the reaction nut. An upper portion of the through bore may comprise a second socket configured to accept a tool for rotating the puller bar.

[0026] According to other embodiments the upper portion of the (elongated) reaction nut may have an external or exterior socket rather than an internal or interior socket. For example, the external or exterior socket may comprise two flats i.e. two flattened sides. Other embodiments are contemplated wherein the external or exterior socket may have a hexagonal form. Yet further embodiments are contemplated wherein the upper portion of the (elongated) reaction nut may comprise both an internal socket and an external socket.

[0027] It will be understood that this another important difference compared to the known hydraulic tensioning tool. With the known hydraulic tensioning tool, the distal end of the puller bar extends beyond the upper surface of the reaction nut to the distal end of the tool. According to the known arrangement a drive socket is located in a distal end of the puller bar.

[0028] However, according to various embodiments the puller bar has been shortened and no longer extends to the distal end of the housing. Rather, the reaction nut has been elongated and redesigned so that it both receives, at one end, the distal end of the puller bar and also extends at the other end to the distal end of the housing. Importantly, according to various embodiments, the modified elongated reaction nut according to various embodiments includes a drive socket.

[0029] Accordingly, a user using the hydraulic tensioning tool according to various embodiments will insert a tool into the drive socket of the reaction nut rather than a drive socket of the puller bar. This is significant because end users often subject the hydraulic tensioning tool to heavy use and sometimes aggressive tooling operations. As a result the drive socket can quickly become worn or damaged. Sometimes aggressive engagement with the drive socket can result in tools becoming stuck and needing to be cut off. However, conventional puller bars are fabricated from highly heat treated high- alloy steel and cannot be subjected to hardening procedures which might assist in preventing the drive socket from becoming damaged.

[0030] In contrast to the known arrangement, according to various embodiments the reaction nut rather than the puller bar now incorporates a drive socket. Unlike the puller bar, the reaction nut according to various embodiments can be fabricated from other materials which can accept a surface coating which serves to protect the drive socket from damage.

[0031] The second socket may have a square-shaped profile. However, other embodiments are contemplated wherein the second socket may more generally comprise either: (i) an internal or interior socket; (ii) an external or exterior socket; and (ill) the combination of both an internal / interior socket and an external / exterior socket. The internal / interior socket may have a square-shaped, rectangular, triangular, hexagonal or twelve-sided shape. More generally the internal / interior socket may be polygonal in shape and may include castellations. The internal / interior socket may also comprise two flats i.e. two flattened surfaces. The external / exterior socket may have a square-shaped, rectangular, triangular, hexagonal or twelve-sided shape. More generally the external / exterior socket may be polygonal in shape and may include castellations. The external / exterior socket may also comprise two flats i.e. two flattened surfaces.

[0032] According to an embodiment the elongated reaction nut may be designed so as to extended beyond the upper surface of an elongated endcap and may comprise an external profile (e.g. square, hexagonal, polygonal etc.) which enables a tool to engage with the outer profile of the reaction nut in order to rotate the reaction nut and hence the puller bar which is mechanically locked or secured to the reaction nut so that rotation of the reaction nut causes the puller bar to rotate. In such embodiments the reaction nut may not comprise an internal socket for accepting a tool. According to various embodiments the reaction nut may be rotated either externally and / or internally. For example, the outer profile of the reaction nut may be shaped so that it can accept a first tool to rotate the reaction nut. The reaction nut may in addition comprise an internal socket allowing a second tool to be inserted into the internal socket to rotate the reaction nut.

[0033] The hydraulic tensioning tool may further comprise a securing mechanism located in a lower portion of the through bore provided in an upper portion of the reaction nut, wherein the securing mechanism is configured to secure the reaction nut to the puller bar.

[0034] The securing mechanism may comprise a locking screw. For example, according to an embodiment a left-handed (“LH”) locking screw may be utilised which has a screw thread that tightens in the counterclockwise direction which is the opposite to more common right-handed (“RH”) screw threads that tighten clockwise. It will be understood that such a locking screw is used in applications where right-handed threads might loosen due to the direction of motion or force applied. Other embodiments are contemplated wherein the locking screw comprises a right-handed screw thread.

[0035] It should be understood that according to various embodiments an off-axis (or perpendicular) small set screw as is used known arrangements is no longer utilised to prevent the puller bar from rotating relative to the reaction nut. Instead, a fundamental different and advantageous locking arrangement is utilised according to various embodiments. In particular, a larger locking screw is utilised which is disposed along the central longitudinal axis of the reaction nut and the puller bar. Importantly, as the puller bar is bottomed out against the reaction nut during installation (i.e. when tightening a nut) and the reaction nut is essentially bottomed against the head of the locking screw during unwinding, then all torque transmissions are occurring face to face in compression which results in a significantly improved torque capability.

[0036] Furthermore, the screw threads are loaded in axial tension which results in the full strength of the material being utilised. According to various embodiments as the new design no longer requires the removal of any thread to install a set screw, then a significantly larger screw can now be utilised.

[0037] Although according to various embodiments a locking screw is utilised to secure the reaction nut to the puller bar, it will be understood that embodiments are contemplated wherein other locking arrangements are utilised. For example, more generally a counteracting thread arrangement may be utilised i.e. the puller bar may comprise a right-handed thread arrangement and the locking screw may comprise a lefthanded thread arrangement to counteract rotational forces. Alternatively, the puller bar may comprise a left-handed thread arrangement and the locking screw may comprise a right-handed thread arrangement to counteract rotational forces. Yet further embodiments are contemplated wherein a mechanical locking device may be utilised to secure the reaction nut to the puller bar to prevent relative rotation. For example, a deformed thread lock, one or more jam nuts or equivalent mechanism may be utilised.

[0038] According to various embodiments the locking mechanism (e.g. locking screw or alternative securing device) between the reaction nut and the puller bar is arranged concentric or co-axial with the longitudinal axis of the reaction nut and / or the puller bar. The locking mechanism (e.g. locking screw or alternative securing device) may be concentric and / or co-axial with the first socket and / or the second socket and / or the third socket as discussed in more detail below. The locking mechanism (e.g. locking screw or alternative securing device) may be arranged or otherwise disposed symmetrically about the longitudinal axis of the reaction nut and / or puller bar.

[0039] The hydraulic tensioning tool may further comprise one or more locking washers located between the locking screw and the reaction nut.

[0040] The use of one or more locking washers provides further locking power to the screw.

[0041] At least a portion of the through bore provided in an upper portion of the reaction nut may be coated with a surface hardening coating.

[0042] With the known arrangement it was not possible to apply a surface hardening coating to the drive socket of the puller bar because the puller bar was fabricated from highly heat treated high-alloy steel which could not accept a surface hardening coating. By contrast, according to various embodiments at least the portion of the reaction nut which forms a drive socket may be provided with a surface hardening coating such as ARCOR (RTM). As a result, the drive socket according to various embodiments may be protected from damage which was not possible with the conventional arrangement. The hydraulic tensioning tool may further comprise a bridge mechanism comprising a third socket for rotating, in use, the fastener.

[0043] In particular, the third socket may comprise a hexagonal-shaped socket which is configured to rotate a hexagonal head of a nut which is threaded onto the thread of a bolt. However, it will also be understood that alternative arrangement may be used. For example, embodiments are contemplated wherein the socket comprises two parallel flats or snake eyed arrangement for using with a pin hole spanner. Yet further embodiments are contemplated wherein more specialised sockets are utilised such as twelve-pointed nuts or castellated nuts.

[0044] The hydraulic tensioning tool may further comprise a gearbox coupled to the bridge mechanism for rotating the third socket.

[0045] The hydraulic tensioning tool may further comprise one or more load cells configured to cause the puller bar to withdraw into the housing thereby pulling, in use, a fastener secured to the first socket of the puller bar. According to various embodiments the hydraulic tensioning tool may comprise one, two, three, four, five, six, seven, eight, nine, ten or more than ten load cells which may be provided in an interlocking arrangement.

[0046] According to another aspect there is provided a hydraulic tensioning system comprising: a hydraulic tensioning tool as described above; and one or more fasteners.

[0047] The one or more fasteners may, for example, comprise a bolt having a thread and a hexagonal head and a nut threaded onto the thread of the bolt.

[0048] According to another aspect there is provided a method of tensioning a fastener comprising: placing a hydraulic tensioning tool as described above over the fastener, wherein the hydraulic tensioning tool further comprises one or more load cells and a bridge mechanism; threading the puller bar on to an end of the fastener so that the bridge mechanism rests on a surface around the fastener; applying hydraulic pressure to the one or more load cells so that the load cells push against the bridge mechanism while pulling up on the puller bar thereby stretching the fastener and creating tension; whilst the fastener is under tension, tightening the fastener to a desired torque; and then releasing the hydraulic pressure. According to another aspect there is provided a method of assembling a hydraulic tensioning tool comprising: providing a housing; locating a reaction nut comprising a recess within the housing; and providing a puller bar having a proximal end having a first socket for securing to a fastener, and a distal end; and receiving the distal end of the puller bar within the recess.

[0049] According to another aspect there is provided a method of retro-fitting a hydraulic tensioning tool comprising: providing a puller bar having a proximal end having a socket for securing to a fastener, and a distal end; re-profiling the distal end of the puller bar; providing a housing; locating a reaction nut comprising a recess within the housing; and receiving the distal end of the puller bar within the recess.

[0050] According to an aspect of the present invention there is provided a hydraulic tensioning tool comprising: a housing; a puller bar located within the housing, wherein the puller bar has a proximal end having a first socket for securing to a fastener, and a distal end; and a reaction nut secured to the puller bar; wherein: the reaction nut comprises a recess and wherein the distal end of the puller bar is received within the recess; and wherein a securing mechanism is configured to prevent relative rotation between the reaction nut and the puller bar.

[0051] According to an embodiment the securing mechanism may comprise a fixing such as a set screw. The reaction nut may have a proximal end which abuts against the distal end of the puller bar. The reaction nut may have a distal end which is opposed to the proximal end and may be arranged so as to be flush with an upper surface of an endcap. The distal end of the reaction may also project beyond the upper surface of the endcap or may be located below the upper surface of the end cap. The securing mechanism may be configured to secure the distal end of the puller bar to the proximal end of the end cap. According to various embodiments, the securing mechanism may extend via a through bore formed through the distal end of the reaction nut and extend into a partial bore located in the distal end of the puller bar. However, other embodiments are contemplated wherein a reverse arrangement may be provided i.e. the securing mechanism may extend through a through bore which extends through the distal end of the puller bar and into a partial bore which extends partially into the proximal end of the reaction nut.

[0052] In general, according to various embodiments the reaction nut and the puller bar may be secured to each other to prevent relative rotation by the use of opposing lefthanded and right-handed thread arrangements.

[0053] According to various embodiment the reaction nut may comprise a through bore, the puller bar may comprise a partial bore, and a securing mechanism may be provided through the through bore of the reaction nut and into the partial bore formed in the puller bar. Alternatively, the reaction nut may comprise a partial bore and the puller bar may comprise a through bore, and a securing mechanism may be provided through the through bore of the puller bar and into the partial bore formed in the reaction nut.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Various embodiments of the present invention together with other arrangements given for illustrative purposes only, will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0056] Fig. 1 shows an exploded view of components of a known hydraulic tensioning tool;

[0057] Fig. 2 shows a known arrangement for simultaneous bolt tensioning utilising an interconnecting hose arrangement;

[0058] Fig. 3 shows an exploded view of a known hydraulic tensioning tool;

[0059] Fig. 4 shows an isometric view of the known hydraulic tensioning tool;

[0060] Fig. 5 shows a plan view of the known hydraulic tensioning tool;

[0061] Fig. 6 shows a side view of the known hydraulic tensioning tool;

[0062] Fig. 7 shows a cross sectional view of the known hydraulic tensioning tool showing both the loadcell assembly and the bridge assembly;

[0063] Fig. 8 shows a cross sectional view of the loadcell assembly of the known hydraulic tensioning tool;

[0064] Fig. 9 shows a cross sectional view of the bridge assembly of the known hydraulic tensioning tool; and

[0065] Fig. 10 shows a hydraulic tensioning tool according to various embodiments.

[0066] DETAILED DESCRIPTION

[0067] Various embodiments of the present invention will be described in further detail below. However, a known hydraulic tensioning tool will first be described by way of background explanation. Fig. 1 shows an exploded view of some of the key components of a known hydraulic tensioning tool 100.

[0068] The known hydraulic tensioning tool 100 comprises two axially stacked interlocking load cells 1 . Each load cell 1 comprises a body, a piston, an inner and an outer seal. The load cells 1 are configured to engage via a reaction nut (not shown) with a puller bar (not shown). The hydraulic tensioning tool 100 further comprises a spring retraction system (not shown).

[0069] The load cells 1 are pressurised via a radial manifold block 6 using a CEJN 116 high pressure nipple. The hydraulic load cells 1 are interlocked for simultaneous pressurisation and are supported by a bridge 4. The bridge 4 has an internal thread which engages with the external thread 5a of a bolt having a hexagonal nut 5b threaded onto the thread of the bolt. The known bolt tensioning tool 100 further comprises a spring retraction system comprising heavy duty springs located within a spring cap 2. When the pressure within the hydraulic tensioning tool 100 returns to zero the spring force will retract the pistons fully back into the respective outer bodies. Each cell is fitted with a polymer lip seal 3 with an anti-extrusion ring.

[0070] The bridge 4 incorporates a spring-loaded gear-driven nut rundown mechanism (not shown) which also incorporates a square drive socket. A gear driven socket within the bridge 4 interfaces with the across flats dimensions of a nut 5a as supplied by an end user.

[0071] Nut rundown following pressurisation is achieved by rotating the gear driven socket. Rotation of the gear driven socket is performed via a square drive socket on the top of the gearbox (not shown). The gearbox and geared socket mechanism may also be utilised to unwind nuts during de-tensioning procedures.

[0072] Hydraulic tensioners such as the hydraulic tensioning tool 100 shown and described above with reference to Fig. 1 can be used with a variety of fasteners including standard hex nuts, large width hex nuts, round nuts or special nuts. An extra length of thread 5a must protrude through the nut 5b in order for the hydraulic tensioner 100 to screw onto the thread 5a of the bolt and apply the bolt tension.

[0073] It is also known to conduct simultaneous bolt tensioning operations. Simultaneous bolt tensioning improves the speed and efficiency when performing a tensioning operation on a multi stud application. When tensioning a plurality of bolts simultaneously the tensioning procedure is essentially the same as tensioning a single bolt but the hydraulic hose setup is different. Fig. 2 shows an arrangement which may be utilised to allow simultaneous bolt tensioning wherein a number of hydraulic tensioners 21 and associated hydraulic hoses 22 are interconnected in a pattern to allow effective oil flow and oil feed into each hydraulic tensioner 21 simultaneously from a common pump unit (not shown). It will be appreciated that whilst there are a variety of different ways in which the hydraulic hoses 22 may be interconnected, the particular arrangement shown in Fig. 2 is perhaps the most common hose setup and is particularly suited for multiple tensioning tools 21 which are simultaneously operated as a group.

[0074] The setup as shown in Fig. 2 is 100% external and effectively forms a hydraulic ring-main thereby allowing easy manual piston reset or quick reset for auto return tensioners. According to the arrangement shown in Fig. 2, a plurality of hydraulic tensioning tools 22 may be interconnected utilising a plurality of hoses 22 having female- male-female (“F-M-F”) connectors. A plurality of T-blocks 23 may be utilised together with a male-female (“M-F”) link hose to the common pump unit (not shown).

[0075] Fig. 3 shows an exploded view of a known hydraulic tensioning tool. The hydraulic tensioning tool 300 comprises a puller bar 301 which is housed within the hydraulic tensioning tool 300. It should be understood that when all the components of the hydraulic tensioning tool 300 are assembled into the final tool, then the puller bar 301 extends the full axial length of the hydraulic tensioning tool 300. In particular, the puller bar 301 has a proximal end 330 and a distal end 331.

[0076] The hydraulic tensioning tool 300 comprises a lower body portion 302 which connects with a bridge 321, an upper body portion 305 which connects to the lower body portion, and a spring cap 310.

[0077] Two pistons are located within the housing of the hydraulic tensioning tool 300. In particular, a lower piston 304 together with a first seal kit 303a is provided within the lower body portion 302. An upper piston 306 together with a second seal kit 303b is provided within the upper body portion 305.

[0078] An important feature of the known hydraulic tensioning tool 300 is the provision of a reaction nut 307 which is secured to the puller bar 301. A single socket set screw 308 is provided to secure the reaction nut 307 against relative rotation in respect of the puller bar 301. A piston return mechanism comprising a plurality of disc springs 309 is provided within the spring cap 310.

[0079] A manifold block 314 is provided with a blanking plug 315. A swivel block 313 is secured to the manifold block 314. O-rings 311 and four socket head cap screws 312 are used to secure the manifold block 314 to the housing of the hydraulic tensioning tool 300. Fig. 4 shows an isometric view of the known hydraulic tensioning tool 300 showing the spring cap 310, upper body portion 305, lower body portion 302 and bridge 321 which together form the main components of the external housing of the hydraulic tensioning tool 300. A gearbox 324 is shown attached to the bridge 321 for rotating a socket (not shown) within the bridge housing. The gearbox 324 is energised by inserting a square-shaped tool into a square drive 326 located on the upper surface of the gearbox 324.

[0080] Fig. 5 shows a plan view of the known hydraulic tensioning tool 300.

[0081] Fig. 6 shows a side view of the known hydraulic tensioning tool 300.

[0082] Fig. 7 shows a cross sectional view of the known hydraulic tensioning tool 300 in more detail. The known hydraulic tensioning tool 300 may be considered as comprising two main components namely an (upper) loadcell assembly A and a (lower) bridge assembly B.

[0083] As will be discussed in more detail below, according to various embodiments various modifications have been made to the loadcell assembly A shown in Fig. 7. In particular, according to various embodiments the puller 301 and the reaction nut 307 have been modified. However, the hydraulic tensioning tool according to various embodiments may utilise the same bridge assembly B as shown in Fig. 7.

[0084] Fig. 8 shows in greater detail a cross sectional view of the loadcell assembly A of the known hydraulic tensioning tool 300 i.e. the bridge assembly B is not shown.

[0085] The loadcell assembly A comprises an inlet manifold 314, a puller bar 301 having an internal (female) thread at the proximal end 330 of the puller bar 301 and a square drive 332 on the distal end 331 of the puller bar 301 . The loadcell assembly A further comprises an endcap 310, disc springs 309, a socket set screw 308, a reaction nut 307, an upper piston 306 and a lower piston 304.

[0086] Fig. 9 shows the bridge assembly B of the known hydraulic tensioning tool in more detail.

[0087] The bridge assembly B comprises a bridge 321 having an internal volume in which a NRS spring 323 is located. A gearbox 324 having a square-drive 326 is connected to a geared socket 361. The bridge assembly B is secured to a tapered proximal end of the loadcell assembly A by six grub screws 327 (not shown) which pass through threaded bores 326 in the upper portion of the bridge 321 and each grub screw 327 then either screws up against the tapered proximal end of the loadcell assembly A or is secured in a threaded bore located within the tapered proximal end of the loadcell assembly A.

[0088] The present inventors have identified a series of problems with the known hydraulic tensioning tool 300.

[0089] One problem with the known hydraulic tensioning tool 300 is that the puller bar 301 and the reaction nut 307 are paired items and cannot be re-paired or reused if one fails. Accordingly, if either the puller bar 301 or the reaction nut 307 becomes damaged, wears out or otherwise fails then both the puller bar 301 and the associated reaction nut 307 need to be replaced.

[0090] It will also be understood that the puller bar 301 is fatigue limited and so will eventually fail and will require replacement. However, replacing the puller bar 301 and the reaction nut 307 involves using a field stripping tool which is time consuming and problematic.

[0091] Another problem with the known arrangement is that securing the reaction nut 307 to the puller bar 301 using a socket set screw 308 means keeping machinable blanks becomes difficult.

[0092] In addition to problems inherent with the known design, users may not use the hydraulic tensioning tool 300 according to the manufacturer’s instructions. In particular, end users may wind down the hydraulic tensioning tool 300 too aggressively with nut runners, windyguns or impacts and this can result in shearing the socket set screw 308 by inertia. Similarly, users can wind down the tools too aggressively which can cause damage to the square drive 332 on the upper surface of the puller bar 301 or indeed break it off completely. As a result, it is common for users to get a tool stuck on the joint. In such scenarios, it may be necessary to have to use a cutting tool in order to release the hydraulic tensioning tool 300 which is obviously undesirable.

[0093] The present inventors have also recognised that the socket set screw 308 in the conventional arrangement is frequently damaged but there is an upper limit on the size of a socket set screw 308 which may be used before too much thread is lost.

[0094] Furthermore, a significant issue with the conventional arrangement is that the socket set screw 308 is loaded in direct shear which is less than ideal and is not utilising the material strength of the socket set screw 308 in an optimal manner.

[0095] The present inventors have also recognised that the puller bar 301 is fabricated from highly heat treated high-alloy steel and hence cannot be subjected to further hardening procedures which might otherwise prevent the square-drive 322 located on an upper surface of the puller bar 301 from becoming damaged.

[0096] The present inventors have also appreciated that end users may be tempted to ignore the manufacturer’s instructions, and to use tools such as impact drivers on the hydraulic tensioner tool 300 contrary to the manufacturer’s operating instructions. It is recognised that end users may be contractors who are likely to be under time pressure to complete a task. Accordingly, the inventors recognise that some end users may not follow the manufacturer’s guidelines because of commercial time pressures.

[0097] The present inventors have therefore considered how the known hydraulic tensioning tool 300 can be redesigned in order to provide a more robust hydraulic tensioning tool which is sufficiently robust such that it might be subjected to misuse without being caused to fail.

[0098] The present inventors have recognised that it is also increasingly difficult to improve the fatigue resistance of the current arrangement as the fatigue resistance is already at a high level due to thread rolling processes and by controlling surface finishes on the fatigue threads and common crack initiation points.

[0099] The present inventors have also recognised that it is not practical for the puller bar 301 not to be secured against the reaction nut 307 in order to prevent relative rotation as this might then allow the reaction nut 307 and the puller bar 301 to work loose from each other resulting in the respective threads stripping as the engagement reduces.

[0100] With the above considerations in mind, the present inventors have re-designed the load cell assembly A in order to solve at least some of the above mentioned problems.

[0101] Fig. 10 shows a hydraulic tensioning tool 300a according to various embodiments. The hydraulic tensioning tool 300a according to various embodiments represents a significant improvement in the art as will discussed in more detail below and the improved design addresses at least some of the technical problems discussed above.

[0102] It should be understood that whilst the hydraulic tensioning tool 300a according to various embodiments utilises an improved loadcell assembly A, the new design deliberately maintains the same bridge assembly B as the known hydraulic tensioning tool 300. As a result, the hydraulic tensioning tool 300a according to various embodiments can be fabricated from re-purposing existing known hydraulic tensioning tools 300 and wherein a majority of the parts can be re-used. Indeed, as will be discussed in more detail below, a conventional puller bar 301 can be shortened and re- profiled and a conventional reaction nut 307 can be replaced with a newly designed elongated reaction nut 307a.

[0103] According to various embodiments a conventional bridge assembly B such as the bridge assembly shown in Fig. 9 may be utilised. Accordingly, a bridge assembly B is not shown in Fig. 10 for clarity reasons.

[0104] In addition to utilising a conventional bridge assembly B, according to various embodiments the hydraulic tensioning tool 300a may utilise a conventional upper piston 306 and a conventional lower piston 304 arrangement along with a conventional manifold block 314.

[0105] Fig. 10 shows that according to various embodiments the hydraulic tensioning tool 300a comprises a housing and a modified puller bar 301a located within the housing. The modified puller bar 301a has a proximal end 300 which has a first internal (female) socket 360 for securing to a fastener e.g. the thread of a bolt. The first socket 360 may have an internal thread which is configured to thread onto the thread of a bolt and hence effectively lock the bolt to the puller bar 301a.

[0106] The puller bar 301a has a distal end 331a but the distal end 331a of the puller bar 301 a is no longer located at the upper surface of the hydraulic tensioning tool 300a. Instead, the puller bar 301a according to various embodiments may be fabricated by reprofiling a conventional puller bar 301 in order to shorten the puller bar and to provide a threaded bore on the new top (distal) end 331a of the puller bar 301a. The modified puller bar 301a is secured to a modified (elongated) reaction nut 307a.

[0107] According to various embodiments the hydraulic tensioning tool 300a according to various embodiments differs from the known hydraulic tensioning tool 300 in that the modified reaction nut 307a comprises a recess or blind bore 380 and wherein the distal end 331a of the puller bar 301a is received within the recess or blind bore 380. It will be understood that the recess or blind bore 380 only extends a limited extent through a portion of the reaction nut 307a and may be created by boring a portion out of any otherwise solid reaction nut 307a during manufacturing.

[0108] It will be understood that according to various embodiments the hydraulic tensioning tool 300a is configured to tension a fastener comprising a bolt having an external thread and a nut having an internal thread which is threaded on to the external thread of the bolt. The bolt may have a hexagonal head. According to various embodiments the first socket 360 is provided in the proximal end 330 of the puller bar 301a and is configured to be secured on to the external thread of a bolt (not shown). The modified reaction nut 307a may further comprise a through bore 385 which extends completely through a portion of the reaction nut 307a. An upper portion of the through bore 385 may comprise a second socket 332a configured to accept a tool for rotating the modified puller bar 301a.

[0109] In contrast to the known arrangement, according to various embodiments it is the modified reaction nut 307a rather than the conventional puller bar 301 which includes a socket 322a which is configured to accept a tool for rotating the reaction nut 307a and hence the puller bar 301a which is connected to the reaction nut 307a. It will be understood that in use the proximal end 330 of the puller bar 301a may be secured to the thread of a bolt. The second socket 322a may have a square-shaped profile.

[0110] The hydraulic tensioning tool 300a according to various embodiments may further comprise a securing mechanism 350 located in a lower portion of the through bore 385, wherein the securing mechanism 350 is configured to secure the reaction nut 307a to the puller bar 301a. The distal end 331a of the puller bar 301a may comprise a recess or blind bore 390 such that during manufacturing the securing mechanism 350 is passed into an upper portion of the through bore 385 formed in the reaction nut 307a and is then screwed or otherwise secured into the recess or blind bore 390 formed in the distal end 331a of the puller bar.

[0111] The securing mechanism 350 may comprise a locking screw 350. The hydraulic tensioning tool 300a may further comprise one or more locking washers 370 located between the locking screw 350 and the modified reaction nut 307a. Advantageously, at least a portion of the through bore 385 formed in the reaction nut 307a may be coated with a surface hardening coating. The hydraulic tensioning tool 300a according to various embodiments may further comprise a bridge assembly B (not shown) which comprises a third socket for rotating, in use, a fastener (not shown). In particular, the third socket may comprise a hexagonal-shaped socket which is configured to rotate a hexagonal head of a nut which is threaded onto the thread of a bolt. The hydraulic tensioning tool 300a according to various embodiments may further comprise a gearbox (not shown) which is coupled to the bridge mechanism for rotating the third socket.

[0112] The hydraulic tensioning tool 300a according to various embodiments may comprise one or load cells configured to cause the puller bar 301a to withdraw into the housing of the hydraulic tensioning tool 300a thereby pulling, in use, a fastener secured to the first socket 360 of the puller bar 301a. Accordingly, various embodiments relate to a hydraulic tensioning system comprising a hydraulic tensioning tool 300a as described above in combination with one or more fasteners. For example, the one or more fasteners may comprise a bolt having an external thread and a hexagonal head and a nut having an internal thread which is threaded onto the external thread of the bolt. A method of tensioning a fastener is also disclosed comprising placing a hydraulic tensioning tool 300a over the fastener. The puller bar 301a is then threaded on to an end of the fastener so that the bridge mechanism 321 rests on a surface around the fastener. The next step is to apply hydraulic pressure to the one or more load cells so that the load cells push against the bridge mechanism 321 while also pulling up on the puller bar 301a thereby stretching the fastener and creating tension. Whilst the fastener is under tension, the method further comprises tightening the fastener to a desired torque. Once this has been achieved then the hydraulic pressure can be released.

[0113] A method of assembling a hydraulic tensioning tool is also disclosed comprising providing a housing and locating a reaction nut 307a comprising a recess (blind bore) 380 within the housing. The method further comprises providing a puller bar 301a having a proximal end 330 and having a first socket 360 for securing to a fastener. The puller bar 301a also has a distal end 331a. The method further comprises receiving the distal end 331 a of the puller bar 301 a within the recess (blind bore) 380 of the reaction nut 307a.

[0114] A method of retro-fitting an existing hydraulic tensioning tool is also disclosed comprising providing a conventional puller bar 301 having a proximal end 330 and having a first socket 360 for securing to a fastener. The puller bar 301 also has a distal end 331a. The method further comprises re-profiling the distal end 331 of the conventional puller bar 301 to make it shorter and take the form of the modified puller bar 301a shown in Fig. 10. The method further comprises providing a housing, locating a reaction nut 307a comprising a recess (blind bore) 380 within the housing and receiving the distal end 331a of the puller bar 301 a within the recess (blind bore) 380 of the reaction nut 307a.

[0115] The hydraulic tensioning tool 300a according to various embodiments may therefore be considered as comprising a reduced length puller bar 301a and an elongated reaction nut 307a when compared against the known hydraulic tensioning tool 300. The elongated reaction nut 307a according to various embodiments has a recess (blind bore) 380 at a proximal end which receives the distal end 331a of the puller bar 301a. It will be appreciated that the elongated reaction nut 307a according to various embodiments has a different configuration to the known reaction nut 307.

[0116] According to various embodiments the elongated reaction nut 307a extends to the upper surface of the tool 300a and is provided with a square drive 332a in order to rotate the puller bar 301a. The puller bar 301a according to various embodiments differs from the known puller bar 301 in that the distal end 331a of the puller bar 301a is received within an end of the elongated reaction nut 307a and has an internal (female) tapped threaded hole on the top face of the puller bar 301a. The puller bar 301a is also bottomed out inside the elongated reaction nut 307a (using snake eye holes 362 on the botom or distal end 330 of the puller bar 301 a). A screw 350, which may be left handed, is inserted into the square drive 332a of the top of the tool and is tightened into the threaded hole 390 on the top face of the puller bar 301 a. Various further embodiments are contemplated wherein one or more locking washers 370 may be included into order to add further locking power to the screw 350.

[0117] The above arrangement provides a locking action between parts. It will be appreciated that in order to unwind the puller bar 301a from the reaction nut 307a, one set of threads must be undone but this can only be done by first removing the screw 350. As a result, the puller bar 301a and the reaction nut 307a are effectively locked together on a coincident axis so that no specific orientation of the parts or staking is required. The puller bar 301a is essentially agnostic as to the reaction nut 307a it is used with.

[0118] According to various embodiments as the puller bar 301a is bottomed out against the reaction nut 307a during installation, the reaction nut 307a is essentially bottomed out against the head of the locking screw 350 during unwinding. As a result, all torque transmissions occur face to face in compression which results in a significantly improved torque capability. The screw threads are additionally loaded in axial tension which results in the full strength of the material being utilised as it is no longer removing thread to install, larger screws 350 may be utilised.

[0119] Another aspect of various embodiments is that the reaction nut 307a now forms a part which contains the square drive 322a on the top of the tool which enables the reaction nut 307a to receive surface treatments such as ARCOR (RTM) wherein a 10-25 pm surface layer of epsilon iron nitride is provided above a nitrogen diffusion layer. The provision of a surface treatment layer makes the square drive 322a significantly less susceptible to becoming worn out or damaged by hand tooling.

[0120] A further significant feature of various embodiments is that the reaction nut 307a is no longer paired to the puller bar 301a it is being used with. Accordingly, the reaction nut 307a can be pre-installed inside a cylinder assembly. For final assembly of tools, the only thing which needs to be done is for the puller bar 301a to be installed into the cylinder assembly and then the bridge assembly B can be added. It will be understood that with the known arrangement the cylinder assembly would need to be partially disassembled in order to add a paired reaction nut 307 to it.

[0121] It will also be understood that according to various embodiments if the puller bar 301a fails or is otherwise damaged then it can be replaced without needing to replace the reaction nut 307a. As a result, it is not necessary to field strip the hydraulic tensioning tool 300a in order to replace a worn or damaged puller bar 307a. One advantage of the hydraulic tensioning tool 300a according to various embodiments is that stock can now be held as cylinder assemblies with the final puller bar 301a being selected on order thereby saving assembly time and improving lead times. Also, the arrangement enables a higher torque to be transmitted via the puller bar-reaction nut interface thereby permitting end users to complete installations more quickly and equally allowing for more aggressive de-installation run-down methods. This represents a significant technical and economic advantage since installation time is an important commercial consideration for end users.

[0122] The improved hydraulic tensioning tool 300a according to various embodiment enables the cost of warranty replacements to be reduced where warranty replacements are warranted and reduces the cost of replacements due to end user misuse. This reduces the cost for end users in terms of reduced servicing and repair costs.

[0123] Another advantageous aspect of the hydraulic tensioning tool 300a according to various embodiments is that the parts are common or re-machinable from existing parts enabling 80% of a conventional hydraulic tensioning tool 300 to be reused in order to convert it into a hydraulic tensioning tool 300a according to various embodiments. As a result, according to various embodiments a conversion or retrofit kit may be provide which is attractive to end users who already have a fleet of conventional tools which they might wish to upgrade to the improved design.

[0124] It is contemplated that according to various embodiments that the puller bar 301a is fabricated from metal or another material having a high tensile strength. In particular, the puller bar 301a may be fabricated from hardened steel. The reaction nut 307a may be fabricated from metal especially a metal which enables a surface hardening treatment to be applied to at least a portion of the reaction nut 307a.

[0125] Although the reaction nut 307a and puller bar 301a have been described as discrete components which form an interlocking arrangement during tool assembly, it is also contemplated that the reaction nut 307a and the puller bar 301a may form or comprise an integral or monolithic component i.e. a single machined component.

[0126] It is also contemplated that the reaction nut 307a may be located at a different position relative to the puller bar 301a as shown in Fig. 10. In particular, the reaction nut 307a may be elongated even further so that the reaction nut 307a engages instead with the lower piston assembly 304 rather than the upper piston assembly 306. Yet further embodiments are contemplated wherein the reaction nut 307a has a portion which engages with both the upper piston assembly 306 and the lower piston assembly 304. While particular embodiments have been illustrated and described, it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the scope of the present invention.

Claims

Claims1. A hydraulic tensioning tool comprising: a housing; a puller bar located within the housing, wherein the puller bar has a proximal end having a first socket for securing to a fastener, and a distal end; and a reaction nut secured to the puller bar; wherein: the reaction nut comprises a recess and wherein the distal end of the puller bar is received within the recess.

2. A hydraulic tensioning tool as claimed in claim 1 , wherein the recess comprises a blind bore which extends only partially through a portion of the reaction nut.

3. A hydraulic tensioning tool as claimed in claim 1 or 2, wherein the reaction nut further comprises a through bore which extends fully through a portion of the reaction nut.

4. A hydraulic tensioning tool as claimed in 3, wherein an upper portion of the through bore comprises a second socket configured to accept a tool for rotating the puller bar.

5. A hydraulic tensioning tool as claimed in claim 4, wherein the second socket has a square-shaped profile.

6. A hydraulic tensioning tool as claimed in any of claims 3, 4 or 5, further comprising a securing mechanism located in a lower portion of the through bore, wherein the securing mechanism is configured to secure the reaction nut to the puller bar.

7. A hydraulic tensioning tool as claimed in claim 6, wherein the securing mechanism comprises a locking screw.

8. A hydraulic tensioning tool as claimed in claim 7, further comprising one or more locking washers located between the locking screw and the reaction nut.

9. A hydraulic tensioning tool as claimed in any of claims 3-8, wherein at least a portion of the through bore is coated with a surface hardening coating.

10. A hydraulic tensioning tool as claimed in any preceding claim, further comprising a bridge mechanism comprising a third socket for rotating, in use, the fastener.

11. A hydraulic tensioning tool as claimed in claim 10, further comprising a gearbox coupled to the bridge mechanism for rotating the third socket.

12. A hydraulic tensioning tool as claimed in claim 10 or 11 , further comprising one or more load cells configured to cause the puller bar to withdraw into the housing thereby pulling, in use, a fastener secured to the first socket of the puller bar.

13. A hydraulic tensioning system comprising: a hydraulic tensioning tool as claimed in any preceding claim; and one or more fasteners.

14. A method of tensioning a fastener comprising: placing a hydraulic tensioning tool as claimed in claim 1 over the fastener, wherein the hydraulic tensioning tool further comprises one or more load cells and a bridge mechanism; threading the puller bar on to an end of the fastener so that the bridge mechanism rests on a surface around the fastener; applying hydraulic pressure to the one or more load cells so that the load cells push against the bridge mechanism while pulling up on the puller bar thereby stretching the fastener and creating tension; whilst the fastener is under tension, tightening the fastener to a desired torque; and then releasing the hydraulic pressure.

15. A method of assembling a hydraulic tensioning tool comprising: providing a housing; locating a reaction nut comprising a recess within the housing; and providing a puller bar having a proximal end having a first socket for securing to a fastener, and a distal end; and receiving the distal end of the puller bar within the recess.

16. A method of retro-fitting a hydraulic tensioning tool comprising: providing a puller bar having a proximal end having a socket for securing to a fastener, and a distal end; re-profiling the distal end of the puller bar; providing a housing; locating a reaction nut comprising a recess within the housing; and receiving the distal end of the puller bar within the recess.

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