Stud Wrench

There are numerous applications, for example, in turbine split casings for power generation, wherein a very high torque must be applied to a stud to rotate the same. No effective wrench is known for wrenching such studs. Accordingly, torches and similar awkward means must presently be used to remove the studs. This is a very time-consuming, expensive, and destructive operation.

High torque ratchet wrenches and related prior art are described in U.S. Pat. Nos. 4,091,890 and 4,132,136, assigned to the same assignee. Such ratchet wrenches for loosening or tightening nuts and bolts do not lend themselves for wrenching applications such as described above, because the required high torques would produce substantial bending and tensile forces in the housing of the ratchet wrench, requiring such housing to be made very large and heavy to maintain its structural integrity. Also, conventional ratchet wrenches would not develop a sufficient prior clamping force on the stud to be wrenched, so that the required torque could not be effectively transmitted to and maintained on the stud.

Drill pipe tongs are also well known and are used in making up or breaking apart drill pipe joints. Typical such tongs are described in U.S. Pat. Nos. 4,082,017 and 3,844,547. Such tongs include hydraulically or pneumatically powered upper and lower tongs which are swivelly connected for a scissoring action. Each of the tongs typically includes a door that is hingedly mounted at one edge and is provided with a latch at the other edge to enable the door to be swung to a completely open position for removal of the tongs from the drill pipe when desired.

The tool wrench for wrenching a stud or shaft comprises a housing having a longitudinal recess therein for mounting the housing over the shaft to be turned. A pawl is connected to the housing for rotation about a pivot having an axis parallel to the axis of the shaft to be turned. A first clamping jaw is slidably mounted in the recess. This jaw has a toothed concave face for clamping an arcuate portion of the shaft, and a convex arcuate wall engageable by a concave matching wall in the pawl, whereby the pawl is adapted to exert a torque on the shaft through the first jaw. A second jaw is slidably mounted in the recess and has a toothed concave face for clamping a diametrically-opposed arcuate portion of the shaft. The first jaw is disposed for limited rotational and transversal movement within the housing recess so as to open the clamping jaws, thereby to allow the tool wrench to be mounted over or to be removed from the shaft. A wrenching actuator is connected to the pawl yoke for turning the pawl clockwise and counter-clockwise about the pawl's pivot. A clamping actuator is mounted on the housing for turning the pawl and the housing in a scissoring action, thereby to securely clamp the pair of jaws about the shaft prior to wrenching the shaft with the wrenching actuator. The wrenching actuator applies a torque on the pawl in a direction so as to increase the initial clamping force produced by the clamping actuator on the jaws, and to rotate the shaft together with the housing.

FIG. 1 is a front view in elevation, partly in section, of a preferred embodiment of the stud wrench assembly;

FIG. 2 is a sectional view taken on line 2--2 of the wrench shown in FIG. 1;

FIG. 3 is a sectional view taken on line 3--3 of the wrench shown in FIG. 2;

FIG. 4 is a front view of the pawl;

FIG. 5 is a side view of the pawl shown in FIG. 4;

FIG. 6 is a front view of the wrench and of the pawl without the actuators and with the wrench shown in its torquing condition;

FIG. 7 is a view similar to FIG. 6 but with the wrench shown in its relaxed condition just prior to starting the torquing operation;

FIGS. 8a-8c are front views of the wrench showing distinct shapes for the jaws for clamping different diameter studs; and

FIG. 9 is an enlarged sectional view taken on line 9--9 of FIG. 8a.

With reference in particular to FIGS. 1 and 9, there are shown a plurality of studs 10 which carry at their opposite ends threads 11, 11'. The threaded ends 11 are shown to threadedly engage a flange 9, such as that of a turbine split casing used for high power generation. While the invention is suitable for such studs, however, it should be understood that it is applicable to any rod or shaft whether threaded or not which requires to be wrenched. The word "shaft" is therefore used in its fullest generic sense so as to include any rotatable member. The wrench of this invention is especially characterized in that it can be mounted over the end of a shaft in completely encircling relation, as will become subsequently apparent.

As depicted in FIGS. 1-5 and 9, the improved stud wrench, generally indicated by the reference numeral 20, includes a pawl, generally designated as 22, attached at its outer yoke 23 to a drive pin 24 which is connected to the ram 25 of a wrenching actuator which can be a hydraulic cylinder 26. Pawl 22 pivots on a pivot pin 28 supported by the wrench housing 12. Housing 12 has a center recess 29 of a predetermined configuration.

The pawl 22 thus presents its longitudinal length in a horizontal plane perpendicular to the longitudinal axis of the stud 10a over which housing 12 is mounted. Wrenching actuator 26 in its power stroke serves to forcefully rotate stud 10a together with housing 12. The casing end 26a of the cylinder 26 is pivotably secured by a pivot 27 to a reaction-support structure 30 which includes a discreetly adjustable clamp 31 adapted for discreetly varying the angular position of the actuator 26 to distinctly different patterns of studs 10, while maintaining intact the pivotal connection on pivot 27.

In any operable position of the reaction-support structure 30 within the provided adjustability range, a substantially-perpendicular angular relationship will be established between the axis of rod 25 and the line A joining the axes of stud 10a and of pin 24. With this perpendicular relationship, maximum torque will be exerted on stud 10a, as more fully explained in said U.S. Pat. No. 4,132,136.

The reaction-support structure 30 further comprises: an anchor leg 32 having a head portion 33 at its inner end and an anchor ring 34 at its outer end, and a back-up leg 35 having a reaction ring 36 at one end thereof and the locking clamp 31 disposed longitudinally therealong. Clamp 31 is discreetly movable longitudinally on the back-up leg 35. The clamp 31 carries a pivot 38 for establishing the pivotal connection with the anchor leg 32. The back-up leg 35 carries a rack 39 extending longitudinally on the inner side thereof. Rack 39 has a plurality of teeth, and the clamp 31 carries at one side internal matching teeth. The clamp's opposite side can be secured to the back-up leg by a hand-operated bolt 42.

Since the anchor rings 34, 36 must have an inner diameter which is slightly larger than the outer diameters of the threaded end portions 11' on the studs 10 used as anchors, there is provided for each one of rings 34, 36 a split sleeve 34' which more snugly fits around the unthreaded solid portions of the studs.

As a result of these linkages, pressurization of the drive actuator 26 causes the pawl 22 to pivot clockwise and counter-clockwise on pin 28. The end 23a of pawl 22 inside housing 12 defines a cylindrical wall 23b.

A vertically-extending (as viewed in FIG. 1) clamping jaw 50 is removably insertable into the semi-cylindrical opening 23c (FIG. 4) of pawl 22. Correspondingly, a second clamping jaw 52 is diametrically positioned in a rectangular slot 53 (FIG. 2) formed as part of recess 29 within the housing 12. Jaw 50 can rotate or oscillate relative to pawl 22 and move sideways or transversely relative to housing 12, while jaw 52 can neither rotate nor move sideways relative to housing 12. Both jaws 50 and 52 can be positioned in and lifted out from the recess 29 only in the axial direction. Jaw 52 is securable to the housing 12 by a key retainer bolt 54.

The clamping jaws 50, 52 are formed with cylindrical surfaces 50a, 52a, respectively, which have the same radius. In their clamping and torquing positions, jaws 50, 52 are diametrically opposite from each other. Jaw teeth 50b, 52b reside in surfaces 50a, 52a, respectively, in facing relation to one another.

A mounting platform 56 is provided on the upper end of housing 12. A hydraulic cylinder 58, acting as a clamp actuator, has its ram 57 positioned to move towards and away a cam shoulder 59 on the plate of pawl 22.

The pawl 22 is rotated clockwise (as viewed in FIG. 7) by an angle b about the axis of the pawl pivot 28 by the retraction of rod 25 in drive actuator 26 to open jaws 50, 52. The stud wrench 20 is then movable over and removable from the stud 10a. When the clamping actuator 58 is in its retracted position, the drive actuator 26 is also in its retracted position.

The extension of ram 57 (from its position as shown in FIG. 7 to its position as shown in FIG. 1) causes pawl 22 to rotate counter-clockwise, and housing 12 to rotate clockwise in a scissoring motion. The upper jaw 50 then moves to the right (as viewed in FIG. 6) towards stud 10a so that jaws 50 and 52 assume their clamping closed position. Pivot 24 is kept stationary by piston rod 25. The movement of jaw 50 is limited by the wall protrusion 29a projecting into recess 29. Thus, the stop means 29a in the housing 12 limit the maximum transverse movement of jaw 50 in response to the extension of ram 57.

When the ram 57 of the hydraulic clamping cylinder 58 becomes extended, pawl 22 rotates counter-clockwise about stationary pivot 24, as viewed in FIG. 7, by the same angle b until the jaws 50, 52 close (FIG. 6). Jaw 50 has to rotate slightly counter-clockwise about its longitudinal axis and move transversely or sideways to the right (as viewed in FIG. 7) in order to grip the stud.

The clamping action produced by ram 57 on cam 59 is transmitted to the stud by the teeth of the jaws 50, 52. At this time, pawl 22, housing 12, and jaws 50, 52 are locked with stud 10a and will rotate together. The extension of ram 25 therefore causes stud 10a to rotate in a counter-clockwise direction, as shown by the arrow 10c (FIG. 6). The rotation of the stud 10a entrains the rotation of housing 12 therewith. Both will rotate by an angle dependent on the stroke of the piston rod 25 of drive cylinder 26. After stud 10a is fully rotated, both the piston rod 57 of clamping cylinder 58 and piston rod 25 of drive cylinder 26 are moved to their fully retracted positions, which completes a full cycle of operation. The clamping and torquing cycle can then start over again. The jaw teeth are forced radially inwardly onto the stud 10a by the clamping action of cylinder 58 and this clamping action is then augmented by the torque produced by the clamping action resulting from the drive cylinder 26.

One of the salient features of the stud wrench 20 is the rotational and sideways motions of the upper jaw 50. Jaw 50 is mounted for limited sideways movement so as to ensure an optimum and safe total clamping force exerted by the cylinders 26 and 58 through the clamping jaws 50, 52 on the stud 10a. This clamping force depends on the angle a (FIG. 6) between Line B joining the axes of pivot 28 and jaw 50, and Line C joining the axes of pivot 28 and stud 10a. If angle a is too small, the total clamping force will become too high (theoretically reaching infinity for angle a equal to 0.degree.); if angle a is too large the total clamping force will be insufficient for the drive cylinder 26 to rotate stud 10a. It was found, therefore, that angle a is critical and should be within a range between 2.degree. and 15.degree.. The preferred range for angle a is between 3.degree. and 6.degree..

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

An important advantage is the scissoring motion of pawl 22 and housing 12 during the initial clamping operation produced by actuator 58, which allows piston rod 25 to remain fully retracted for most efficient operation.

The slidable jaw construction also allows the tool wrench 20 to accommodate various sizes of jaws and studs, as better illustrated in FIGS. 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 addition, the wrenching actuator 26 and the clamping actuator 58 can be controlled manually, or preferably with suitable valves together with a fluid system, thereby alleviating the possibility of injury due to handling and improving safety throughout operation.