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Title:
A SYSTEM FOR SIMULTANEOUSLY PRE-SET TORQUEING AND TENSIONING A MULTI-JACKBOLT TENSIONER
Document Type and Number:
WIPO Patent Application WO/2019/089414
Kind Code:
A1
Abstract:
An assembly for simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner, the apparatus comprising: a first tensioning device comprising a first plurality of spindles arranged to simultaneously tension the plurality of jackbolts to an initial tightened configuration, the spindles being arranged to interrupt delivery of torque to one or more of the jackbolts when the one or more of the jackbolts attain an initial torque value; and a second tensioning device comprising a second plurality of spindles arranged to simultaneously tension the initially tightened plurality of jackbolts to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously to attain a pre-determined torque value that is greater than the initial torque value.

Inventors:
MCPHEE, Andrew, Duncan (36 Hakea Crescent, Chapel HillQueensland, 4069, 4069, AU)
ARMSTRONG, Peter, Elliott, Scott (49 Trossachs Place, Upper KedronQueensland, 4055, 4055, AU)
GREENWELL, Steven (972 St. Clair Parkway, Mooretown, ON N0N 1M0, 1M0, CA)
Application Number:
US2018/057919
Publication Date:
May 09, 2019
Filing Date:
October 29, 2018
Export Citation:
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Assignee:
SUPERBOLT, INC. (1000 Gregg Street, Carnegie, PA, 15106, US)
International Classes:
B25B23/14; B23P19/06; B25B21/00; B25B29/02
Domestic Patent References:
WO2017118960A12017-07-13
Foreign References:
US20140245869A12014-09-04
US20030226427A12003-12-11
US2069882A1937-02-09
EP1753065A12007-02-14
SU975303A11982-11-23
Attorney, Agent or Firm:
MORNEAULT, Monique (Scherrer Patent & Trademark Law, P.C.17 E. Crystal Lake Ave, Crystal Lake IL, 60014, US)
Download PDF:
Claims:
CLAIMS

1 . An assembly for simultaneously tensioning a plurality of jackbolts of a multi- jackbolt tensioner, the assembly comprising: a first tensioning device comprising a first plurality of spindles arranged to simultaneously tension the plurality of jackbolts to an initial tightened configuration, the spindles being arranged to interrupt delivery of torque to one or more of the jackbolts when the one or more of the jackbolts attain the initial torque value; and a second tensioning device comprising a second plurality of spindles arranged to simultaneously tension the initially tightened plurality of jackbolts to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously to attain a pre-determined torque value that is greater than the initial torque value.

2. An assembly in accordance with claim 1 wherein the first tensioning device further comprises a first plurality of spindle gears such that each of the first plurality of spindle gears is associated with a corresponding spindle of the first plurality of spindles respectively and wherein the second tensioning device comprises a second plurality of spindle gears associated with a corresponding spindle of the second plurality of spindles.

3. An assembly in accordance with any one of claims 1 or 2 wherein the first tensioning device further comprises a plurality of clutch mechanisms such that each of said clutch mechanisms is associated with a corresponding spindle gear and/or spindle of the first tensioning device and wherein each of said clutch mechanism is arranged to interrupt delivery of torque to the spindle of the first tensioning device when a torque force applied to the spindle gear of the first tensioning device exceeds the initial torque value.

4. An apparatus in accordance with claim 3 wherein the clutch mechanism comprises a biased member positioned in a bore of the spindle gear of the first tensioning device, said bore being positioned circumferentially relative to the spindle associated with said spindle gear of the first tensioning device, the biased member being urged towards engagement with an engagement portion of the spindle wherein in a torque transmitting configuration, the biased member is received in the engagement portion to allow transmission of torque to the spindle member; and wherein in a torque interrupting configuration, the biased member moves out of associated engagement with the engagement portion when the jackbolt coupled to the associated spindle attains the initial torque value.

5. An apparatus in accordance with claims 3 or 4 wherein each spindle gear comprises a plurality of said clutch mechanisms that are circumferentially arranged relative to the associated spindle of the first tensioning device.

6. An apparatus in accordance with any one of claims 3 to 5 wherein the biased member comprises a spring loaded member preferably a spring loaded ball and wherein the engagement portion on the spindle comprises an opening to receive the spring loaded ball.

7. An assembly in accordance with any one of the preceding claims further comprising a power transfer unit to transfer torque from a drive unit to the first tensioning device and the second tensioning device.

8. An assembly in accordance with claim 7 wherein the power transfer unit comprises a driving gear configured to be meshed with the first plurality of spindle gears to transfer drive to the first plurality of spindles in a first tensioning configuration and wherein the driving gear is configured to be meshed with the second plurality of spindle gears in a second tensioning configuration.

9. An assembly in accordance with claim 8 wherein the drive gear is centrally positioned relative to the first and second plurality of spindle gears during use.

10. An assembly in accordance with any one of claims 8 and 9 wherein the drive gear comprises a gear wheel to receive drive from a drive shaft coupled to said gear wheel.

1 1. An assembly in accordance with claim 10 wherein the drive shaft comprises a connector for connecting the drive shaft to a drive unit.

12. An assembly in accordance with any one of claims 7 to 1 1 wherein the drive gear comprises a forwardly extending coupling portion for being meshed with the first or second plurality of spindle gears.

13. An assembly in accordance with claim 12 wherein the driving gear, gear wheel and the drive shaft are housed in a housing, said housing comprising an outwardly facing receiving portion for receiving said first or second tensioning device during use to position and retain said first or second tensioning device to position the coupling portion of the drive gear in a meshed configuration with the first or second plurality of spindle gears.

14. A method of simultaneously tensioning a plurality of jackbolts of a multi- jackbolt tensioner, the method comprising the step of:

(a) coupling the plurality of jackbolts to a first plurality of spindles of a first tensioning device to simultaneously tension the plurality of jackbolts to an initial tightened configuration including interrupting delivery of torque to one or more of the jackbolts when the one or more of the jackbolts attain an initial torque value;

(b) coupling the plurality of jackbolts to a second plurality of spindles of a second tensioning device to simultaneously tension the initially tightened jackbolts from step (a) to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously to attain a pre-determined torque value that is greater than the initial torque value.

15. A tensioning device for simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner, the device comprising:

a plurality of spindles arranged to simultaneously tension the plurality of jackbolts to an initial tightened configuration,

a plurality of clutch mechanisms such that each of said clutch mechanisms is associated with a corresponding spindle gear and/or spindle wherein each of said clutch mechanisms is arranged to interrupt delivery of torque to the spindle of the first tensioning device when a torque force applied to the spindle gear of the first tensioning device exceeds an initial torque value.

Description:
A SYSTEM FOR SIMULTANEOUSLY PRE-SET TORQUEING AND TENSIONING A MULTI-JACKBOLT TENSIONER

BACKGROUND

[0001 ] A Multi-Jackbolt Tensioner (MJT), such as the tensioner sold under the Superbolt ® brand, is generally used as a direct replacement for hex nuts, covered nuts, bolts, etc. of a size typically of 1 " or greater. A conventional (nut based) MJT threads onto an existing bolt or stud providing a highly effective means to "bolt up the joint". The typical MJT consist of three components, i) a hardened washer to provide a hardened, flat surface for the jackbolts to "push" against; ii) an often round nut body that threads onto the existing bolt or stud and seats hand tight against the washer initially; and iii) a polar array of jackbolts that thread through the nut body so that their points force against the washer to pre-tension the bolt or stud.

[0002] FIG. 1A is a partially cutaway version of a nut-style MJT 10. The MJT 10 comprises an annular body 12. The body 12 of the MJT 10 is formed with a threaded central hole 15 to receive a bolt, shaft, or stud. A polar array of threaded jack bolt holes 1 1 , each disposed on a circle concentric with the central hole, pass though the body 12. Corresponding jack bolts 14 traverse the jack bolt holes 1 1 and are threadedly received therein. The MJT 10 further includes a load bearing member in the form of a hardened washer 16 against which points of the jack bolts 204 abut in use. The hardened washer 16 bears against a workpiece being fastened. As an alternative to the nut-style MJT of FIG. 1A, bolt-style MJTs are also known. A bolt- style MJT generally comprises a body having a threaded shaft that may be used for blind tapped holes and counterbores. MJTs are commercially available from Superbolt, Carnegie PA. Further discussions of MJTs may be found in U.S. Pat. Nos. 4,622,730, RE33.490, 4,927,305, 5,075,950, 5,083,889 and 6, 1 12,396, which are incorporated herein by reference.

[0003] MJTs have addressed some significant problems from the past. However, the use of MJT has given rise to some other problems which need to be addressed. Specifically, each jackbolt of the MJT must be separately tightened. Some industrial applications require implementation of multiple MJTs and in such applications, the tightening of each jackbolt can become time consuming. Typically, the tightening of jackbolts involves the use of a wrench or a hand held tool with a socket whereby each jackbolt needs to be individually tightened.

[0004] Prior art tools that include multiple spindles that can be used for tightening many fasteners at one time are known in the art. Such tools typically include a single motor employed to drive a plurality of spindles with a gear arrangement placed between the motor and the spindles. The gear arrangement usually comprises a central gear and three planet gears fixed in a common carrier. However, such prior art tools that incorporate a geared arrangement for driving multiple spindles have been found to be quite ineffective for tightening multi-jackbolt tensioners because such tools will often result in some of the jackbolts being undertightened and other fasteners being overtightened.

[0005] It is important to note that during tightening of an individual jackbolt, a strong thrust (axial) force is generated and this thrust force is directed against a hardened washer. Jackbolts have a small friction diameter and can therefore create a high thrust force with relatively little torque input. As result, controlling the level of torque imparted to the jackbolts is an important consideration. During typical use, the jackbolts are initially tightened by hand and this might often result in the jackbolts being tensioned to an unequal initial torque values. As a result, when the prior art tools for simultaneously fastening these multiple jackbolts are used, some of the jackbolts are likely to be under-tightened and other jackbolts are likely to be overtightened. Accordingly, there is a need to provide an improved tensioning apparatus that can simultaneously and equally tension all the jackbolts.

SUMMARY OF THE INVENTION

[0006] In a first aspect, the invention provides an assembly for simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner, the assembly comprising:

a first tensioning device comprising a first plurality of spindles arranged to simultaneously tension the plurality of jackbolts to an initial tightened configuration, the spindles being arranged to interrupt delivery of torque to one or more of the jackbolts when the one or more of the jackbolts attain an initial torque value; and a second tensioning device comprising a second plurality of spindles arranged to simultaneously tension the initially tightened plurality of jackbolts to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously to attain a pre-determined torque value that is greater than the initial torque value.

[0007] In a second aspect, the invention provides a method of simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner, the method comprising the steps of:

(a) coupling the plurality of jackbolts to a first plurality of spindles of a first tensioning device to simultaneously tension the plurality of jackbolts to an initial tightened configuration including interrupting delivery of torque to one or more of the jackbolts when the one or more of the jackbolts attain the initial torque value;

(b) coupling the plurality jackbolts to a second plurality of spindles of a second tensioning device to simultaneously tension the initially tightened jackbolts from step (a) to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously to attain a pre-determined torque value that is greater than the initial torque value.

[0008] In an embodiment, the first tensioning device further comprises a first plurality of spindle gears such that each of the first plurality of spindle gears is associated with a corresponding spindle of the first plurality of spindles respectively and wherein the second tensioning device comprises a second plurality of spindle gears associated with a corresponding spindle of the second plurality of spindles.

[0009] In an embodiment, the first tensioning device comprises a plurality of clutch mechanisms such that each of said clutch mechanisms is associated with a corresponding spindle gear and/or spindle of the first tensioning device and wherein each of said clutch mechanism is arranged to interrupt delivery of torque to the spindle of the first tensioning device when a torque force applied to the spindle gear of the first tensioning device exceeds the initial torque value.

[0010] In an embodiment, each clutch mechanism comprises a biased member positioned in a bore of the associated spindle gear of the first tensioning device, said bore being positioned circumferentially relative to the spindle associated with said spindle gear of the first tensioning device, the biased member being urged towards engagement with an engagement portion of the spindle wherein in a torque transmitting configuration, the biased member is received in the engagement portion to allow transmission of torque to the spindle member; and wherein in a torque interrupting configuration, the biased member moves out of associated engagement with the engagement portion when the jackbolt coupled to the associated spindle attains the initial torque value.

[001 1 ] In an embodiment, the clutch mechanism is adjustable for varying the initial torque value at which delivery of torque is interrupted. Such an arrangement allows the user to easily adjust the initial torque value and control when the clutch engages and interrupts delivery of torque. The adjustment may be provided by adjusting the extent of biasing of the biased member. By way of example, a grub screw may be utilised for adjusting the biased member.

[0012] In an embodiment each spindle gear comprises a plurality of said clutch mechanisms that are circumferentially arranged relative to the associated spindle of the first tensioning device.

[0013] In an embodiment, the biased member comprises a spring loaded member preferably a spring loaded ball and wherein the engagement portion on the spindle comprises an opening to receive the spring loaded ball.

[0014] In an embodiment, the assembly further comprises a power transfer unit to transfer torque from a drive unit to the first tensioning device and the second tensioning device.

[0015] Preferably, the power transfer unit comprises a driving gear configured to be meshed with the first plurality of spindle gears to transfer drive to the first plurality of spindles in a first tensioning configuration and wherein the driving gear is configured to be meshed with the second plurality of spindle gears in a second tensioning configuration. [0016] In an embodiment, the drive gear is centrally positioned relative to the first and second plurality of spindle gears during use.

[0017] In an embodiment, the drive gear comprises a gear wheel to receive drive from a drive shaft coupled to said gear wheel.

[0018] Preferably, the drive shaft comprises a connector (such as a socket) for connecting the drive shaft to a drive unit.

[0019] In an embodiment, the drive gear further comprises a forwardly extending coupling portion for being meshed with the first or second plurality of spindle gears.

[0020] In an embodiment, the driving gear, gear wheel and the drive shaft are housed in a housing, said housing comprising an outwardly facing receiving portion for receiving said first or second tensioning device during use to position and retain said first or second tensioning device to position the coupling portion of the drive gear in a meshed configuration with the first or second plurality of spindle gears.

[0021 ] In yet another aspect, the invention provides a tensioning device for simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner, the device comprising:

a plurality of spindles arranged to simultaneously tension the plurality of jackbolts to an initial tightened configuration,

a plurality of clutch mechanisms such that each of said clutch mechanisms is associated with a corresponding spindle gear and/or spindle wherein each of said clutch mechanisms is arranged to interrupt delivery of torque to the spindle of the first tensioning device when a torque force applied to the spindle gear of the first tensioning device exceeds an initial torque value.

BRIEF DESCRI PTION OF THE DRAWINGS [0022] In order that this invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a preferred embodiment of the invention and wherein:

Figure 1 is a top photographic view of a first tensioning device 100. Figure 1A is a partially cutaway view of an MJT.

Figure 2 is a top photographic view of the second tensioning device 200 coupled with socket drivers 217.

Figure 3 is an internal top view of the first tensioning device 100 (with the housing 150 removed).

Figure 4 is top view of the first tensioning device 100.

Figure 5 is a broken-out sectional view of the first tensioning device 100.

Figure 5A is an enlarged view of the inset shown in Figure 5.

Figure 5B is a cross section through a clutch assemblies of a spindle at the tensioning device 100.

Figure 6 is a perspective view of the power transfer unit 300.

Figure 7 is a broken-out sectional view of the power transfer unit 300 shown in a coupled configuration with the first tensioning device 100.

Figure 8 is a photographic perspective view of the second tensioning device 200.

Figure 9 is a broken-out sectional view of the second tensioning device 200.

Figure 10 is a first in-use view of the power transfer unit 300 shown in a coupled configuration with the second tensioning device 200 being used to tension jackbolts in a MJT 500. Figure 1 1 is a second in-use view of the power transfer unit 300 shown in a coupled configuration with the second tensioning device 200 being used to tension jackbolts in a MJT 500.

DETAILED DESCRIPTION

[0023] Referring to Figures 1 to 1 1 an assembly for simultaneously tensioning a plurality of jackbolts of a multi-jackbolt tensioner (MJT) 500 (shown in Figures 10 and 1 1 ) is decited. The assembly comprises a first tensioning device 100 having a first plurality of spindles 1 10 that are arranged to simultaneously tension the plurality of jackbolts on the MJT 500 to an initial tightened configuration. The assembly also comprises a second tensioning device 200 comprising a second plurality of spindles 210 arranged to simultaneously tension the initially tightened plurality of jackbolts to a subsequent tightened configuration by delivering torque to all of the jackbolts simultaneously by means of socket couplers 217 (See Figure 2) to attain a predetermined torque value that is greater than the initial torque value. Each of the first and second tensioning devices 100 and 200 is adapted to be coupled to a power transfer unit 300 (See Figure 6) that allows a drive unit to transmit power to the tensioning devices 100 and 200. Specifically, each of the tensioning devices 100 and 200 are configured to be coupled with the power transfer unit 300. The power transfer unit includes a socket 370 (shown in Figure 10) that can receive an input shaft of a drive unit (not shown). The drive unit (not shown) may encompass electrical or pneumatic motors. Pneumatic motors are powered by compressed air and vary in terms of air fittings and air consumption. Electric power motors typically use a DC controller as a power supply. The motor is preferably provided with fixed, typically square, drives (or output shafts) that are designed to mate with a socket provided in the power transfer unit 300.

[0024] The power transfer unit 300 (shown in Figures 6 and 7) comprises a central drive gear 310 mounted for rotation in the housing 320 along a central drive gear axis. The central drive gear axis defines a longitudinal axis for the power transfer unit 300. The central drive gear 310 is configured to be coupled to the source of rotating power for rotating the central drive gear 310. Specifically the central drive gear 310 is coupled to a concentric gear wheel 315 that is driven by a drive shaft, specifically a worm shaft 340 coupled with the gear wheel 315 of the central drive gear 310. A hign torque worm drive of the type described in international patent publication WO/2016/141407.

[0025] The central drive gear 310 comprises an outwardly extending coupling portion 312 that is adapted to be coupled with the first tensioning device 100 to the initially tensioned configuration. In a first step, the power transfer unit 300 is coupled with the first tensioning device 100 in a coupled configuration (best shown in Figure 7). The coupling portion 312 is received into an opening (or receiving portion) of the first tensioning device 100 in order to mesh the central drive gear 310 of the power transfer unit 300 with the spindle gears 120 of the first tensioning device 100 that are arranged to drive each of the plurality of spindles 1 10 (that transfer torque to the jackbolts of the MJT 500 during use). A fastening arrangement comprising fasteners 330 (shown in Figure 6) is also provided to fasten the housing 150 of the first tensioning device 100 onto the housing 320 of the power transfer unit 300 in order to maintain the coupling portion 312 in a meshed configuration with the spindle gears 120 whilst the first tensioning step is carried out. The coupling portion 312 is positioned centrally relative to a cradle portion 335 defined by the housing 320 of the power transfer unit 300 that receives and engages the housing 150 of the first tensioning device 100.

[0026] The spindles 1 10 and the associated spindle gears 120 are arranged in an annular arrangement surrounding the coupling portion 312 of the power transfer unit 300. Each spindle 1 10 is independently mounted for rotation within the housing 150 of the first tensioning device 100, with one spindle 1 10 being associated with one of the series of jackbolts of the MJT 500. The first tensioning device 100 may include the same number of spindles 1 10 as the number of jackbolts provided in the MJT 500. MJTs such as the MJT 500 shown in Figures 10 and 1 1 includes 8 jackbolts. However, in other embodiments, the number of spindles 1 10 provided in the first tensioning device 100 may be varied to suit use with MJTs containing a wide variety of numbers of jackbolts (such as six or ten jackbolts). Socket couplers may be used for coupling the spindles with the jackbolts during use.

[0027] Importantly, the spindle gears 120 for each of the spindles 1 10 are offset from each other along the axis of the central drive gear 310 to allow for all of the spindle gears 120 to be accommodated in the housing 150 of the first tensioning device 100. A clutch mechanism 180 is positioned radially between each spindle gear 120 and the associated spindle 1 10, wherein the clutch mechanism allows for rotation of the spindle 1 10 below a torque setting of the clutch mechanism 180 in the tightening direction. As will be understood by those in the art, when the force or torque resisting the spindle rotation (i.e. the loading torque on the jackbolt) exceeds the torque setting of the clutch mechanism 180 in the tightening direction the spindle 1 10 will cease rotation despite the rotation of the associated spindle gear 120 due to the slipping of the clutch mechanism 180.

[0028] Referring to Figures 5 and 5A, a detailed view of the clutch mechanism 180 is illustrated. The clutch mechanism 180 comprises a plurality of clutch assemblies 185(Fig 5B) which are ball detent style clutch assemblies that are arranged circumferentially around the spindle 1 10. Each of the clutch assemblies 185 comprises a flange 1 16 located concentrically around the base of spindle 1 10 and integrally formed there with, biased member provided in the form of a spring loaded ball 182 positioned in a bore 184 of the spindle gear 120 and biased toward flange

1 16 by spring 1 19. A plurality of bores 184 are provided in each spindle gear 120 to circumferentially surround the spindle 1 10. Each of the said bores 184 corresponds to a respective clutch assembly 185. A plurality of these clutch assemblies 185 surround the spindle 1 10. During use, the spring loaded ball 182 is urged towards engagement with an engagement portion in the form of a hole or recess in 1 16 of the spindle 1 10. In a torque transmitting configuration, the spring loaded ball 182 is partcially received in the engagement portion 1 17 of the spindle 1 10 to allow transmission of torque to the spindle member 1 10. When the torque value provided by the central gear 310 exceeds a preset value, the engagement portion 1 17 exerts sufficient force on spring loaded ball 182 to overcome the biasing of the spring 1 19 sotset the ball moves out of associated engagement with the engagement portion

1 17 and thus the clutch disengages. When the jackbolt coupled to the associated spindle attains the initial preset torque value and is in an initially tightened position. In at least some embodiments, the clutch mechanism180 may be adjusted for varying the initial torque value at which delivery of torque is interrupted. Such an arrangement allows the user to easily adjust the initial torque value and control when the clutch mechanism 180 engages and interrupts delivery of torque. The adjustment may be provided by adjusting the extent of biasing of the spring loaded ball 182. For example, a grub screw 121 may be provided to control the compression of spring 1 19 and thus the spring loading of the spring loaded ball 182. The user may set the torque at which the clutch mechanism 180 disengages by tightening or untightening the grub screw associated with each clutch assembly or by selecting springs with a different stiffness.

[0029] The inventors have found that using the tensioning device 100 for tightening the jackbolts to an initially tightened position at a common initial torque value provides several advantages. It is important to realise that the jackbolts on the MJT 500 (shown in Figures 10 and 1 1 ) are typically positioned on the threaded nut body of the MJT by hand. As a result, every jackbolt of the MJT may be tightened a unique starting torque value. The use of the tensioning device 100 that incorporates the clutch arrangement 180 allows for all of the jackbolts to be tightened to a substantially similar torque value without encountering the issue of overtightening or undertightening the jackbolts. In other words, each of jackbolts of the MJT which may have been finger tight with varying levels of torque values are tightened and positioned to a substantially identical torque value, the initial torque value.

[0030] Once the jackbolts have been tightened by the first tensioning device 100, the power transfer unit 300 is coupled to a second fastening device 200 (shown in Figures 2, 8 and 9). As previously described, the central drive gear 310 of the power transfer unit 300 comprises an outwardly extending coupling portion 312 that is adapted to be coupled with the second tensioning device 200. In a second tensioning step, the power transfer unit 300 is coupled with the second tensioning device 100 in order to mesh the central drive gear 310, specifically the coupling portion 312, of the power transfer unit 300 with the second plurality of spindle gears 220 of the second tensioning device 200 that are arranged to drive each of the second plurality of spindles 210 that transfer torque to the jackbolts of the MJT 500 to tighten the jackbolts further to a pre-set torque value that is greater than the initial torque value achieved with the first tensioning device. Once again the fastening arrangement comprising fasteners 330 is also suitable to fasten the housing 250 of the second tensioning device 200 onto the housing 320 of the power transfer unit 300 in order to maintain the coupling portion 312 in a meshed configuration with the second plurality of spindle gears 220. The coupling portion 312 is positioned centrally relative to a cradle portion 335 defined by the housing 320 of the power transfer unit 300 that receives and engages the housing 250 of the second tensioning device 200. [0031 ] The second plurality of spindles 210 and the associated spindle gears 220 are also arranged in an annular arrangement surrounding the coupling portion 312 of the power transfer unit 300. Each spindle 210 is independently mounted for rotation within the housing 250 of the second tensioning device 200, with one spindle 210 being associated with one of the series of jackbolts of the MJT 500. As previously explained in relation to the first tensioning device 100, the second tensioning device 200 may include the same number of spindles 210 as the number of jackbolts provided in the MJT 500. MJTs such as the MJT 500 shown in Figures 10 and 1 1 includes 8 jackbolts. It will be understood that in other embodiments, the number of spindles 210 provided in the second tensioning device 200 can also be varied to suit use with MJTs containing a wide variety of numbers of jackbolts (such as six or ten jackbolts).

[0032] The spindle gears 220 for each of the spindles 210 are also offset from each other along the axis of the central drive gear 310 to allow for all of the spindle gears 220 to be accommodated in the housing 250 of the second tensioning device 100. Figures 10 and 1 1 illustrate the power transfer unit 300 in a coupled configuration with the second tensioning device 200. It is also important to note that unlike the first tensioning device 100, the second tensioning device 200 does not include a clutch arrangement or any other means of interrupting delivery of torque to the spindles 210.

[0033] The inventors have found that using the first and second tensioning devices 100 and 200 for the above-described two-step jackbolt tightening process provides an advantage over the prior art tools that are currently available. First, the step of aligning the jackbolts to an initially tightened position using the first tightening device 100 is helpful in aligning the jackbolts to a uniform starting position whereby all of the jackbolts have been tightened to a substantially identical initial torque value. The use of the clutch mechanism 180 in the first tensioning device 100 interrupts delivery of torque to individual spindles 1 10 when the initial torque value for each of the jackbolts has been achieved. The inventors have found that applying high levels of torque to completely tighten the jackbolts results in overtightening and undertightening of the jackbolts (because of the non-uniform starting positions). The use of the first tensioning device to align the jackbolts into an initial and uniform torque value before applying a higher level of torque alleviates some of the shortcomings of the prior art. In particular, the use of the two different tensioning devices 100 and 200 alleviates the need for complicated and voluminous gearing systems to impart torque over a wide range of values. The use of the first tensioning device 100 with a clutch mechanism 180 which initially aligns all the jackbolts to an initial and uniform torque value followed by using the second tensioning device 200 provides two compactly configured devices that can be easily coupled to the power transfer unit 300.

[0034] All documents cited herein are incorporated herein by reference, but only to the extent that the incorporated material does not conflict with existing definitions, statements, or other documents set forth herein. To the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern. The citation of any document is not to be construed as an admission that it is prior art with respect to this application.

[0035] In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term "comprises" and its variations, such as "comprising" and "comprised of" is used throughout in an inclusive sense and not to the exclusion of any additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

[0036] While particular embodiments have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, numerous equivalents to the specific apparatuses and methods described herein, including alternatives, variants, additions, deletions, modifications and substitutions. This application including the appended claims is therefore intended to cover all such changes and modifications that are within the scope of this application.