GB2060453A - Stud Rotating Power Wrench - Google Patents

Abstract

The power wrench (20) for rotating the stud (10a) comprises a wrench body (12) defining a socket (29) for loosely encircling the stud. A pawl (22) is pivotably connected with the wrench. The pawl has an outer end (23) outwardly extending from the wrench body, and an inner end (23a) extending into the socket. A first jaw (50) is axially disposed in the socket between the inner end of said pawl and the stud. A second jaw (52) is axially disposed in the socket between the body and an opposite portion of the stud. A clamp actuator (58) is mounted on the body. The clamp actuator has a ram (57) which pushes against the pawl. A wrench driver (26) is coupled to the outer end of the pawl. The actuator clamps the jaws to the stud by relative pawl-body movement. Anti-clockwise rotation of the pawl by the driver rotates the body with the pawl and thus the stud. The driver has a reaction assembly comprising two arms (32, 35) connected by an adjustable rack (34) and clamp (42) assembly and having respective stud surrounding rings (34, 36). <IMAGE>

Description

SPECIFICATION Power Wrench Assembly This invention relates to a power wrench assembly.

In many industries, for example, in split electric turbine casings, there are many elongated members, such as studs, and it is often necessary to apply a torque to them. Prior to the present invention, no effective tool was commercially available for applying a torque to such studs.

According to the present invention there is provided a power wrench assembly comprising a wrench member defining an aperture for loosely receiving a member to which torque is to be applied by the wrench assembly, and a pawl pivotably connected with the wrench member, the pawl having an outer end projecting outwardly from the wrench member, and an inner end extending into the aperture, a pair of jaws being provided in the aperture whereby, in use of the assembly, one of the jaws is disposed between the inner end of the pawl and one side of the member to which torque is to be applied and the other jaw is disposed between the wrench member and an opposite side of the member, a clamp actuator being mounted on the wrench member and having a ram which is adapted to push against the pawl to cause the pawl to rotate relatively to the wrench member whereby the jaws are forcibly clamped to the member to which torque is to be applied, and a wrench driver being coupled to the outer end of the pawl for applying a torque to the clamped jaws and to the member.

Ways of carrying out the invention are described with reference to the drawings which illustrate specific preferred embodiments and in which: Figure 1 is a front view in elevation, partly in section, of a preferred embodiment of the power stud wrench assembly; Figure 2 is a sectional view taken on line 2-2 of the wrench shown in Figure 1; Figure 3 is a sectional view taken on line 3-3 of the wrench shown in Figure 2; Figure 4 is a front view of the pawl; Figure 5 is a side view of the pawl shown in Figure 4; Figure 6 is a front view of the wrench and of the pawl without the actuators and with the wrench shown in its torquing condition.

Figure 7 is a view similar to Figure 6 but with the wrench shown in its relaxed condition just prior to starting the torquing operation; Figures 8a-Sc are front views of the wrench showing distinct shapes for the jaws for clamping different diameter studs; and Figure 9 is an enlarged sectional view taken on line 9-9 of Figure 8a.

The preferred embodiment of the power wrench assembly is generally designated as 20. It is illustrated in Figures 1 and 9 for torquing an elongated member such as a stud 10 which is used on a flange 9 of an electric turbine casing. A typical stud 1 0a has an unthreaded center portion and threaded ends 11,11'.

Power wrench assembly 20 comprises a wrench 12 intimately interconnected with a pawl 22. A clamp actuator 58 and a wrench driver 26 are adapted to exert separate and distinct forces on pawl 22. A reaction-and-support structure 30 supports wrench driver 26 and provides the necessary reaction forces thereto.

It is desired to rotate stud 1 Oa by clamping thereto wrench 12 and to react against adjacent studs, as will be subsequently described.

The body of wrench 1 2 defines an axial socket 29 of a predetermined configuration. Socket 29 has an inwardly-projecting stop shoulder 29a (Figure 2). The upper end of wrench 1 2 is provided with a platform 56 onto which is bolted the clamp actuator 58.

Pawl 22 has an outer yoke 23 and an outer cam shoulder 59. Yoke 23 is pivotably connected by a drive pin 24 to the ram 25 of the wrench driver 26. Pawl 22 is pivotably mounted in the body of wrench 12 on a pivot-pin 28. The inner end 23a of pawl 22 defines a semi-cylindrical bearing surface 23b (Figure 4).

A first clamping jaw 50 is axially disposed in an opening 23c in the socket 29 between the bearing surface 23b of pawl 22 and a portion of stud 1 0a being torqued. A second clamping jaw 52 is also axially disposed in the socket 29 between the outer end of wrench 12 and a diametrically-opposed portion of stud 1 Oa. The second clamping jaw 52 is positioned in a rectangular slot 53 defined by socket 29. Jaws 50 and 52 have arcuate clamping surfaces 50a, 52a provided with teeth 50b, 52b, respectively.

Jaw 50 can rotate or oscillate relative to pawl 22, and it can also move sideways or transversely relative to wrench 12. Jaw 52 can neither rotate nor move sideways relative to wrench 1 2. Jaws 50, 52 can be placed in and removed from socket 29 but only in an axial direction. Jaw 52 can be secured to wrench 12 by a bolt 54.

The reaction and support structure 30 includes a first leg 35 having at its outer end a ring 36 and at its inner side a rack gear 39. A clamp 31 having an inner meshing gear (not shown) is made to ride up or down on the rack gear 39. A second leg 32 has an inner end 33 and an outer anchor ring 34.

Clamp 31 is connected to the inner end 33 of leg 32 by a pivot pin 38. Clamp 31 can be secured to leg 35 by a bolt-and-nut 42.

Anchor rings 34. 36 have an inner diameter which is larger than the outer diameters of stud 1 0. A split sleeve 34' is inserted between studs 10 and anchor rings 34, 36.

The ram 57 of clamp actuator 58 engages cam shoulder 59 on the pawl 22 during its power stroke for the purpose of exerting a downward force on the pawl as shown by the arrow on the rod 57.

One of the salient features of the wrench 12 is the rotational and sideways motions permitted to upper jaw 50. Jaw 50 is mounted for limited sideways movement. This ensures an optimum and safe total clamping force exerted on stud 1 Oa by hydraulic cylinders 26 and 58 acting indirectly on clamping jaws 50, 52. This clamping force depends on the angle "a" (Figure 6) between Line B, joining the axes of pivot 28 and jaw 50, and Line C joining the axes of pivot 28 and stud 1 0a. If angle "a" is too small, the total clamping force will become too high (theoretically reaching infinity for angle "a"=OO);; if angle "a" is too large the total clamping force will be insufficient for wrench driver 26 to rotate stud 1 0a. It was found, therefore, that angle "a" is critical and should be within a range between 20 and 150. The preferred range for angle "a" is between 30 and 60.

In the preferred embodiment, the yoke 23 of pawl 22 is formed by a pair of ears 23'a, 23'b (Figure 5), and the body of pawl 22 has at least two, but preferably three or five, side plates 22a-22c. These plates have aligned holes 28f within which pin 28 is rotatably mounted. The end faces 22'a--22'e of these plates constitute the bearing surface 23b of pawl 22 which bears against first jaw 50. Wrench 12 has matching recesses 1 2a-1 2c (Figure 3) for slidably accepting therein the corresponding pawl's plates 22a-22c (Figure 9). With this construction the clamping and shear forces become distributed instead of being concentrated.

The slidable jaws 50, 52 allow wrench 12 to accommodate various sizes of jaws and studs, as better illustrated in Figures 8a-8c from which it will be seen that the dimensions of both jaws 50 52 must change for different diameter studs to maintain angle "a" within its critical range.

In operation, to open jaws 50, 52, pawl 22 is rotated clockwise (Figure 7) by an angle "b" about pivot 28 by retracting rod 25 of driver 26.

Wrench 12 is then movable over and removable from stud 1 0a. When actuator 58 is in its retracted position, actuator 26 is also in its retracted position.

A substantially-perpendicular angular relationship should be established between the axis of ram 25 and a line A which joins the axes of stud 1 Oa and of pin 24. This perpendicular relationship will allow for the most efficient operation.

The extension of ram 57 (from its position as shown in Figure 7 to its position as shown in Figure 1) causes pawl 22 to rotate counter clockwise, and wrench 12 to rotate clockwise in a scissoring motion. This scissoring motion of pawl 22 and wrench 12, during the initial clamping operation produced by actuator 58, allows rod 25 of driver 26 to remain fully retracted, thereby obtaining the most efficient operation. The upper jaw 50 then moves to the right (Figure 6) towards stud 1 Oa so that jaws 50 and 52 assume their clamping positions. Shoulder 29a in socket 29 limits the maximum transverse movement of jaw 50 in response to the extension of ram 57.

When ram 57 of actuator 58 becomes extended, pawl 22 rotates counter-clockwise about stationary pivot 28 (Figure 7) by the same angle "b" until jaws 50, 52 clamp stud 1 Oa (Figure 6). Jaw 50 has to rotate slightly counter clockwise about its longitudinal axis and move transversely or sideways to the right (Figure 7) in order to clamp stud 1 Oa.

The clamping action produced when ram 57 pushes downwardly against cam 59 of pawl 22 is transmitted to the stud by the teeth 50b, 52b of jaws 50, 52, respectively. These teeth are forced radially inwardly onto stud 1 Oa, first by cylinder 58, and this initial clamping action is then augmented by the torque produced by cylinder 26.

When pawl 22, housing 12 and jaws 50, 52 become locked to stud 1 Oa they will all rotate together, and jaws 50, 52 will be diametrically opposite from each other.

The extension of ram 25, therefore, causes stud 1 0a to rotate in a counter-clockwise direction, as shown by arrow 1 0c (Figure 6). The rotation of stud 1 Oa entrains therewith the rotation of housing 12. Both will rotate by an angle dependent on the stroke of the rod 25 of driver 26.

After stud 1 Oa is fully rotated, both rods 25 and 57 of cylinders 26 and 58, respectively, are moved to their fully-retracted positions, which completes a full clamping and torquing cycle, and wrench 12 is ready to restart a new cycle of operation.

Claims (6)

Claims

1. A power wrench assembly comprising a wrench member defining an aperture for loosely receiving a member to which torque is to be applied by the wrench assembly, and a pawl pivotably connected with the wrench member, the pawl having an outer end projecting outwardly from the wrench member, and an inner end extending into the aperture, a pair of jaws being provided in the aperture whereby, in use of the assembly, one of the jaws is disposed between the inner end of the pawl and one side of the member to which torque is to be applied and the other jaw is disposed between the wrench member and an opposite side of the member, a clamp actuator being mounted on the wrench member and having a ram which is adapted to push against the pawl to cause the pawl to rotate relatively to the wrench member whereby the jaws are forcibly clamped to the member to which torque is to be applied, and a wrench driver being coupled to the outer end of the pawl for applying a torque to the clamped jaws and to the member.

2. A wrench assembly as claimed in claim 1, in which each jaw has a toothed face for engagement with the member to which torque is to be applied, and in which the said one jaw is mounted for limited lateral movement within the aperture so as to permit release of the jaws from the member and to allow the wrench member to be mounted over or to be removed from the member.

3. A wrench assembly as claimed in claim 1 or 2, in which the pawl has at least three parallel plates for operatively engaging the said one jaw, the wrench member having at least three recesses for movably receiving the plates.

4. A wrench assembly as claimed in any one of claims 1 to 3, in which the aperture has a stop shoulder for limiting the movement of the said one jaw in the aperture.

5. A wrench assembly as claimed in any one of the preceding claims, in which the said other jaw is limited for movement in an axial direction parallel to the axis of pivotal movement between the pawl andthe wrench member.

6. A wrench assembly substantially as described herein with reference to, and as shown in, the accompanying drawings.