US2996940A

US2996940A - Predetermined torque release wrench

Info

Publication number: US2996940A
Application number: US789084A
Authority: US
Inventors: William E Van Hoose
Original assignee: PENDLETON TOOL IND Inc
Current assignee: PENDLETON TOOL IND Inc
Priority date: 1959-01-26
Filing date: 1959-01-26
Publication date: 1961-08-22
Anticipated expiration: 1978-08-22

Description

Aug. 22, 1961 w. E. VAN HoosE PREDETERMINED TORQUE RELEASE WRENCH 2 Sheets-Sheet l Filed Jan. 26, 1959 4 l l l A Y bzfforLZ-] Aug. 22, 1961 w. E. VAN HoosE PREDETERMINED ToRQUE RELEASE WRENCH- 2 sheets--sheet 2 Filed Jan. 26, 1959 IN VENTOR.

ilnited tates 2,995,940 PREDETERMINED TORQUE RELEASE WRENCH William E. Van House, Beli, Calif., assiguor to Pendleton Tool Industries, Inc., Los Angeles, Calif., a corporation of California Filed Ian. 26, 1959, Ser. No. 789,084 18 Claims. (Cl. 81-52.4)

This invention deals generally with wrenches, and more particularly with an improved predetermined torque release wrench.

The present application is a continuation-in-part of my copending application, Serial No. 695,323, tiled November 8, 1957, now abandoned, and entitled Magnetic Torque Limiting Wrench.

Predetermined torque release wrenches of the type With which this invention is concerned are equipped with a handle, a torque applying member pivoted on the handle, yand a predetermined torque release connection between the member and handle. So long as the torque applied to a work element through the member is less than the torque release setting of the Wrench, the member is locked to the handle `for rotation with the latter.

When the applied torque becomes equal to the torque setting, the handle is released to turn with respect to the member. This release of the handle affords an indication that the torque setting of the wrench has been reached.

A broad object of the invention may be stated as being the provision of an improved predetermined torque release wrench of the character described.

A more specific object of the invention is to provide `an adjustable predetermined torque release wrench embodying a new and improved multiple, lever-type, predetermined torque release connection between the torque applying member and the wrench handle.

Another oibject of the invention is to provide a predetermined torque release wrench of the character described in which the torque release setting of the wrench is adjusted by varying the mechanical advantage off the lever-type connection between the wrench handle `and torque applying member.

Yet another object of the invention is to provide a predetermined torque release wrench of the character described wherein the means for adjusting the torque release setting of the wrench possesses purely linear calibration characteristics so as to permit the use of a linear torque scale.

A further object of the invention is to provide a predetermined torque release Wrench of the character described Which may be either mechanically or magnetically controlled.

Yet a further object of the invention lis to provide a predetermined torque release wrench of the character described which has a' relatively simple and compact 'construction so as to be capable of manufacture at appreciably reduced cost, which is pleasing in appearance and easy to use, and which is otherwise especially well suited to its intended purposes.

Other objects, advantages and features of the invention will become apparent as the description proceeds.

Briefly, the objects of the invention `are attained by the provision of a predetermined torque release wrench in which the force exerted on the Wrench handle to? rotate a work element is transmitted to the torque applying member through the multiple lever connection or lever system between the member and handle. This connection includes a lirst lever arm which is operatively connected to the member so as to pivot in a given direction on the handle when the member turns on the handle in the direction of the reaction or resisting torque exerted on the member during the application of a torqueload.

Patented ug. 22, 11961 The multiple lever connected is completed by a predetermined torque release means including a second lever arm and snap action means for releasably latching the second lever against pivoting.

This second arm engages the iirst lever arm so as to normally prevent pivoting of the latter in said given direction and thereby lock the torque applying member to the wrench handle for rotation with the latter to apply a torque load to a Work element.

When a predetermined torque load is reached, the snap action means release to release the first and second lever yarms for pivoting onthe handle. Adjustment of the torque release setting of the Wrench is accomplished by shifting the torque release means on the handle to shift the point of contact of the lever arms lengthwise of one `arm and thereby change the effective length of the latter arm.

This results in a change in the mechanical advantage of the multiple lever connection between the torque applying member and wrench -handle and a corresponding ohange in the torque release value of the wrench.

A primary feature of the invention resides in-the fact that the mechanical -advantage of the lever system is varied by changing the length of one ar-m only of a lever in the system. This results in a linear calibration of the wrench and permits the use of a linear torque setting scale without the need of the exponential-tolinear conversion means required in some existing torque limiting wrenches.

Two different embodiments of the present Wrench are disclosed herein. One of these embodiments is magnetically controlled while the other embodiment is mechanically controlled.

The invention may be better understood from the following detailed description thereof, taken in connection with the annexed drawing, wherein:

IFIG. l is a View in perspective of the present wrench;

FIG. 2 is an enlarged rear end view of the wrench of FIG. l;

FIG. 3 is an enlarged longitudinal sectional View through the magnetic version of the present wrench showing the parts of the latter in their normal positions;

HG. 4 is a partial view similar to FIG. 3, but on reduced scale, showing the parts of the wrench in the positions they occupy after release of the wrench;

FIG. 5 is a section taken along line 5 5 of FIG. 3;

FIG. 6 is an enlarged section taken along line 6--6 of FIG. 3;

FIG. 7 is an enlarged section taken along line 7-7 of FIG. 5;

FIG. 8 is a section taken along line 8 8 of FIG. 3;

FIG. 8a is a section taken along line Saz-3a of FIG. 3;

FIG. 9 is a longitudinal secton through the mechanical version of the present wrench;

FIG. l0 is a section taken along line 1li-10 of FIG. 9;

FIG. l1 is a partial view illustrating certain parts of the wrench in FIG. 9 in released position; and

FIG. 12 is an enlarged detail View of the mechanical latch means of the wrench in FIG. 9.

IReference is made first to FIGS. l-Sa, illustrating the magnetic version of the present wrench. This form of the wrench comprises a tubular wrench handle 10 which is slightly widened and flattened at its front end. Pivoted on a transverse axis in this end of the handle is a torque applying member in the form of a pin 12. This pin has, outside the handle 10, a square stud 14 for receiving a socket (not shown) or the like.

When using the Wrench, a torque is applied to a work handle. The handle, therefore, tends to turn in a clockwise direction with respect to the pin.

Generally indicated at 16 is a multiple lever-type, magnetically controlled, predetermined torque release connection between the handle 10 and pin 12 for locking the latter to the handle for clockwise rotation with the handle until a predetermined torque load is applied. As will shortly be clear, when this predetermined torque load is reached, the handle is released for limited clockwise turning with respect to the pin.

The lever system 17 of connection 16 comprises a transverse lever arm 18 rigid on the pin 12 within the flattened, forward end of the wrench handle and a series of three

levers

20, 22 and 24 located within the central portion of the handle.

Levers

20 and 22 are rigid on cross pins 26 and Z8, respectively, opposite ends of which are pivoted in the wall of the wrench handle on axes parallel to the turning axis of pin 12. Final lever 24 extends through slot 30 in a fulcrum block 32 and is rigid on a cross pin 34, opposite ends of which are pivoted in the block on an axis also parallel to the turning axis of pin 12.

The rear, free end of lever arm 18 has a fulcrum, shown as a knife edge 36, which engages the forward arm of lever 20. The forward arm of lever 22 is engaged by a knife edge fulcrum 38 on the rear arm of lever 20, while the rear arm of lever 22 is engaged by a knife edge fulcrum 40 on the forward arm of lever 24.

The arrangement of the lever system is such that counterclockwise turning of pin 12 in the handle 10 causes counterclockwise pivoting of lever 22. Lever 24 forms part of a snap action type, predetermined torque release, restraining means 42 which restrains the lever 22 against such counterclockwise pivoting, and, therefore, the pin 12 against counterclockwise turning in the wrench handle, until a predetermined torque load is applied. This snap action means comprises a cylindrical permanent magnet 44 and magnetically permeable armature 46 having a generally frustoconical shape.

Armature 46 has a slot 48 in the plane of lever 24 which opens through the front face of the armature. Rotatably received within the slot is a disc 50 rigid on an eccentric shaft S2 which projects beyond the opposite faces of disc t). Opposite ends of shaft 52 are slidably and rotatably received in aligned bores 54 in the armature, the axis of which bores is normal to the armature slot 48.

As will presently be described, there is reason to adjust the angular position of the eccentric disc 50 in the armature slot during calibration of the wrench. One end of the eccentric shaft 52 has a screwdriver slot 56 for this purpose. The eccentric disc is locked in its adjusted angular setting by means of a set screw 58 threaded in one of the armature bores 54 and engageable with the other end of the eccentric shaft.

The rear end of lever 24 is slidably received in the armature slot 48 and engages the eccentric disc 50. The arrangement is such that clockwise pivoting of lever 24 rocks the armature in a counterclockwise direction about a fulcrum edge 60 formed by the intersection of `the rear face 62 and conical side wall 64 of the armature. This fulcrum edge engages the inner wall of the wrench handle 10.

From the description of the wrench thus far, it will be observed that when a torque is applied to a work element through the pin 12, by rotating the wrench handle in a clockwise direction, as viewed in FIG. 3, the resulting counterclockwise, resisting torque on the pin results in a clockwise reaction torque on the lever 24 which tends to rock the armature 46 on its fulcrum edge 60 away from the magnet 44. This counterclockwise rocking of the armature, of course, is resisted by the magnetic attraction between the armature and magnet.

It is evident that the magnitude of the counterclockwise torque acting on the armature 46 is related to the magnitude of the applied torque load. The magnitude of the torque acting on the armature at any given applied torque load, however, is much less than the magnitude of the applied torque because of mechanical advantage of the lever system 17.

It is also evident that a predetermined magnitude of counterclockwise torque on the armature, and hence a predetermined magnitude of applied torque load, are required to break or rock the armature away from its magnet 44. If the magnitude of the applied torque load is less than such predetermined magnitude, the magnetic attraction between the magnet and armature retains the latter, and hence the pin 12, against counterclockwise pivoting in the wrench handle and in their normal position of FIG. 3. Under these conditions, the predetermined torque release connection 16 acts as a rigid connection between the wrench handle 10 and pin 12, and the latter is rotated in the clockwise direction with the handle. When the magnitude of the applied torque load equals said predetermined magnitude of applied torque load the armature 46 rocks away from the magnet 44 so that the connection 16 is released to permit a limited clockwise turning of the wrench handle 10 with respect to the pin.

ln reality, the armature 46 suddenly snaps away from the magnet 44 and the conical side wall 64 of the armature strikes the inner surface of the wrench handle. This impact of the armature with the wrench handle produces an audible click which affords an indication that the torque release value of the wrench has been reached. A second indication of this fact is afforded by the sudden release of the handle 10 for limited clockwise turning `with respect to the pin 12 when the connection 16 releases The wrench is capable of certain calibration adjustments as well as adjustment by the user of the wrench to vary its torque release value or setting. The means for accomplishing these adjustments will now be described.

The calibration adjustments are three in number and involve adjustment of the length of the rear arm of lever 24, to alter the break away force exerted on armature 46 by lever 24 for any given magnitude of applied torque, adjustment of the air gap between the magnet 44 and armature 46 to alter the magnitude of counterclockwise torque on the armature necessary to break the latter away from the magnet, and the aforementioned angular adjustment of the eccentric disc 5t) to maintain contact between the lever 24 and armature in every position of adjustment of the latter.

Adjustment of the length of the rear arm of lever 24 is accomplished by shifting the fulcrum block 32 for the lever toward or away from the armature. To this end, the fulcrum block is generally cylindrically shaped, as shown in FIG. 8a, and slidably received within the wrench handle 10. This fulcrum block is rotatably connected to an adjusting rod 66 by means of a pin 68 engaging in a circumferential groove in the end of the rod 66. Rod 66 extends loosely through a clearance slot 70 in armature 46 and has its rear end slidably and rotatably received in a bore 72 in a cylindrical magnet housing 74. 'This magnet housing is made of magnetically non-permeable material -and is slidably received in the rear end of the wrench handle 10. Magnet 44 is tightly fitted in an axial bore 76 in, and opening through, the forward face of the magnet housing 74. Magnet housing 74 and fulcrum block 32 together form a movable support on the handle for lever 24 and the magnetic snap-action means.

The rear end of bore 72, in the magnet housing 74, is counter-bored and threaded, as illustrated at 78. Threaded in this counterbore is an enlarged, threaded end at the rear of the adjusting rod 66. Formed in the rear end of the adjusting rod is a screwdriver slot 82 by which the rod may be turned to adjust the fulcrum block 32, and the lever 24 pivoted thereon, axially l of the handle 10, toward and away from the armature 46. This adjustment varies the effective length A of the rear arm of lever 24 as measured between the pivot axis of the lever and point of Contact of the rear end of the lever with the eccentric disc Sil. Such adjustment of the lever arm length A, of course, varies the force exerted on the armature by lever 24, and hence the counterclockwise torque acting on the armature, for any givn value of applied torque.

The second calibration adjustment, namely, adjustment of the air gap spacing between the armature 46 and magnet 44, is accomplished by 'axial adjustment of a second adjusting rod 84. This second adjusting rod is slidably and rotatably received in a bore 86 in the magnet housing 74 and is arranged to engage the armature 46 diametrically opposite its fulcrum edge 60. The rear end of bore 86 is counter-bored and threaded at 88 for receiving an enlarged, threaded end 90 on the rear end of the adjusting rod 84. The rear end of adjusting rod 84 has a screwdriver slot 92 by which the rod may be rotated.

When the adjusting rod 84 is turned in one direction, it is advanced against the armature 46 to rock the latter away `from the magnet 44 and thereby increase the air gap spacing between the magnet and armature. Rotation of the 4adjusting rod 84 in the opposite direction retracts the latter away from the armature, thereby allowing the latter to be rocked, by magnetic attraction, toward the magnet 44, to decrease the air gap spacing.

Increasing the air gap spacing, of course, has the effect of reducing the magnitude of the force or counterclockwise torque which must be applied to the armature to break the latter `away from its magnet. Decreasing the air gap spacing obviously has the opposite effect.

It will be evident from an inspection of the drawings that adjustment of the armature away from the magnet, to increase the Iair gap spacing, will create a gap between the rear end of the lever 24 and the eccentric disc Si). Such a gap is undesirable since it introduces slack or play into the wrench. After adjustment of the armature, to set the air gap between the latter and magnet 44 to the desired width, therefore, the eccentric disc 5t) is angularly adjusted, in the manner previously described, to eliminate any clearance between the disc and rear end ofthe lever 24.

The above adjustments are for calibration purposes and performed at the time of manufacture of the wrench. The additional adjustment, previously referred to, namely, that of adjusting the mechanical advantage of the lever system 17 to vary the torque release setting of the wrench, is performed by the user of the tool.

This latter adjustment is `accomplished by shifting the torque release means 42, comprising fulcrum block 32 and lever 24 pivoted thereon, armature 46, and magnet housing 74, lengthwise of the wrench handle 16 to vary the eifective length -B of the rear arm of lever 22 measured between the pivot axis of the latter lever and the point of engagement of the fulcrum edge 4@ on lever 24 with lever 22. Tlhis adjustment of the torque release means is accomplished by rotation of an external sleeve handle 94 on the rear end of the wrench handle 10.

Sleeve handle 94 is formed intermediate its ends with a relatively coarse, internal thread 96 which meshes with a similar external thread 98 on the rear end of the wrench handle 1t). The forward portion of the sleeve handle, ahead of its internally threaded portion 96, has a smooth internal wall and is slidably and rotatably tted on the smooth wall portion of the wrench handle 1d ahead of its threaded portion 98.

The rear end. of the central opening in the sleeve handle 94 is slightly counter-bored and internally threaded for receiving a cylindricallyshaped, threaded insert ltltl. This insert projects beyond the rear end of the sleeve handle and has a `lock nut 102 threaded thereon. The lock nut is tightened against the rear end of the sleeve handle to keep the insert 160 against turning in the sleeve handle.

Magnet housing 74 has, at its rear end, a reduced cylindrical extension 104 which is rotatably received in an axial bore 106 in the insert 100. The magnet housing land insert are connected for relative rotation and against relative axial movement by means of a set screw 1% threaded in the insert and engaging in a peripheral groove 110 in the extension 104. As shown most clearly in FIG. 7, the magnet housing 74, which, as mentioned earlier, is axially slidable in the wrench handle 10, is keyed against rotation relative to the latter by means of a pin 112, one end of which is threaded in the wrench handle, and the other end of which slidably engages in a longitudinal groove 114 in the magnet housing.

From this description, it will be evident that when the sleeve handle 94 is rotated on the wrench handle 1G, the former moves axially relative to the latter. This axial movement of the sleeve handle is imparted to the magnet housing 74 by virtue of the engagement of the set `screw 108 in the peripheral groove 110 of the magnet housing. The latter, of course, is restrained against turning with the sleeve handle by the engagement of the pin 112 in the key slot 114 of the magnet housing. The armature 46, which is held against the forward face of the magnet housing by the magnetic attraction between the armature and magnet 44, the fulcrum block 32, which is connected to the magnet housing by the adjusting rod 66, `and the lever 24 which is pivoted on the fulcrum block are axially shifted in the wrench handle with the magnet housing. As mentioned earlier, this axial adjustment of the lever 24 varies the effective length of the rear arm of lever 22 and, therefore, the mechanical advantage of the lever system 17.

A change in the mechanical advantage of the lever system obviously produces a corresponding change in the counterclockwise torque acting on the armature 46, tending to break the latter away from magnet 44, for any given applied torque load. Thus, rotation of the sleeve handle 94 in one direction retracts the lever 24 rearwardly in the wrench handle and increases the effective lever arm length B. This, in turn, increases the mechanical advantage of the lever system 17 and, therefore, the torque release value of the wrench. Ihat is, increasing the mechanical advantage of the lever system decreases the magnitude of the counterclockwise torque acting on the armature for a given magnitude of applied torque and therefore increases the magnitude of applied torque necessary to break the armature away from the magnet 44. Similarly, rotation of the sleeve handle 94 in the opposite direction yadvances the lever 24 forwardly in the wrench handle and decreases the effective lever arm length B. This, in turn, decreases the mechanical advantage of the lever system 17 and, therefore, the applied torque value necessary to release the connection 16.

lt is evident that a purely linear relationship exists between the axial position of the lever 24 within the wrench handle and the magnitude of applied torque at which the connection 16 releases, that is, the torque release setting of the wrench. It is also evident that a purely linear relationship exists between the angular and axial position of the sleeve handle 94 and the axial position of the lever Z4. Clearly then, a linear relationship exists between the torque release setting of the wrench and the angular and axial position of the sleeve handle.

Thus, the torque release setting of the wrench, for different positions of adjustment of the sleeve handle, may be simply indicated by a Vernier scale 116 inscribed on the wrench handle 1@ and a linear scale 118 inscribed on the forward end of the sleeve handle. The forward edge of the sleeve handle is used as the reference which is read against the scale 116. This scale includes a longitudinal reference line 120 against which the Vernier scale 118 is read.

Formed in the forward, annular face of the insert 100 are a series of circumferentially spaced, spherical recesses 124. A spring-pressed ball 126, contained in an axial bore in the rear end of the magnet housing 74 and projecting beyond the annular shoulder 12S formed on the housing at the base of its reduced extension 104, is engageable in the recesses 124 to provide an indexing action for the sleeve handle 74 during rotation of the latter to adjust the torque release setting of the wrench. After the torque release setting of the wrench has been adjusted, it is desirable that the parts be locked in position so as to avoid the possibility of accidental change of the setting. This is accomplished by a lock nut 130.

Lock nut 130 has a reduced, threaded forward end 132 engaging in a threaded axial bore 134 extending into the rear end of the magnet housing 74. Rearwardly of its threaded end 132, lock nut 130 has a slightly enlarged cylindrical shoulder 136 which is rotatable in a counterbore 13S at the rear end of the threaded bore 134. The rear end of the lock screw is enlarged to form a cylindrical head 140 which is disposed in a counterbore 142 in the rear of the insert 100. This lock screw head 140 has an upstanding rib 144 by which the lock screw may be turned.

When the lock screw 130 is turned in one direction, the enlarged head 140 thereof is forced against the annular shoulder 146 formed at the juncture of bore 106 and counterbore 142 in the insert. The insert 100, and, therefore, the sleeve handle 94 are thereby frictionally restrained against rotation relative to the magnet housing 74 and wrench handle 10.

Operation of the wrench is believed to be obvious from the foregoing description. Thus, a socket or the like is placed on the external, square stud 14 of the torque applying member or pin 12. The lock screw 130 is then loosened and the sleeve handle 94 is rotated in one direction or the other to adjust the wrench to the desired torque release setting. Lock screw 130 is then again tightened to lock the sleeve handle in its adjusted position.

A torque load is applied to a work element by rotating the wrench handle in a clockwise direction, as Viewed in FIG. 3. When the applied -torque load becomes equal to the torque release setting of the wrench, the armature 46 suddenly breaks or snaps away from the magnet 44 and rocks on its fulcrurn edge 60 into impact with the interior wall of the wrench handle 10. This impact produces an audible click which may be heard and felt by the user of the tool and serves as an indication that the torque release setting of the wrench has been reached. As mentioned, an additional indication of this nature is afforded by the slight pivotal movement which occurs between the wrench handle and pin 12 upon release of the connection 16. When the wrench is removed from the tool, the connection 16 is automatically reset in its normal condition of FIG. 3 by the magnetic attraction between the latter and armature.

It will be apparent that at the time of initial calibration of the wrench, its range of torque release settings may `be adjusted by adjustment of the rod 84 to vary the air gap between the magnet 44 and armature 46 in the normal unreleased position of the latter. That is, as the air gap spacing between `the magnet and armature is reduced, the torque release value for any given setting of the sleeve handle 94 is increased. Increasing the normal air gap spacing, of course, has the opposite effect. Thus, a series of the present wrenches, all of which will be identical in construction, may be adjusted to have different ranges of torque release values by appropriate setting of the normal air gap spacing between their magnets and armatures.

Reference is now made to FIGS. 9-12 which illustrate a mechanical version of the present predetermined torque release wrench. This modified wrench is identical to the magnetic version of the wrench just described, except that the modified wrench utilizes spring-type snap action means for controlling the release'of the wrench rather than the magnetic snap action means of the previous wrench.

Thus, the modified wrench comprises a predetermined torque release connection 16 between the wrench handle 10 and torque applying member or pin 12 which restrains the latter against relative rotation in the wrench handle until the applied torque load `equals, the torque release setting of the wrench. Connection 16 includes a lever system 17 which is identical to the lever system 17 of FIGS. 1-8a, except for certain changes in the final lever 24 of the lever system.

This final lever 24 is formed at its rear end withl a diagonal slot 200 in a plane normal to the pivotal axis of the lever. Within this slot is a latch plate 202. This latch plate is rigid on a pin 204 which is pivoted at opposite ends in the lever 24 at opposite sides of slot 200, for pivoting of the latch plate 202 about an axis parallel to the pivotal axis of the lever 24.

Latch plate 202 has an edge 206 which is engageable with the bottom 208 of the slot 200 to limit counterclockwise pivoting of the latch plate on the lever 24' to its normal position of FIG. 9 wherein a corner 210 on the latch plate projects beyond the rear end of the lever 24. Diagonally opposite the corner 210, latch plate 202 has a rounded edge 212 having its center located approximately on the axis of latch plate pivot pin 204 to permit clockwise pivoting of the latch plate from its normal position of FIG. 9 for reasons to be seen.

Slidably fitted in a ybore 214 in the rear wall 208 of the lever slot 200 is a spring-pressed pin 216 which is urged against a `bevelled edge 217 of the latch plate to bias the latter in a counterclockwise direction to its normal position. Clockwise pivoting of the latch plate 202 effects a camming action on the pin 216 which depresses the latter against the action of its spring.

Slidably fitted within the rear end of the wrench handle 10 is a cylindrical housing 218 which is similar to the magnet housing 74 in the wrench of FIGS. l-Sa and keyed against rotation in the wrench `handle in the same manner as described with reference to the magnet housing of the previous wrench. Housing 218 has an axial bore 220 opening through its forward face. Slidably received in this bore is a detent 222 having a forward, conical tip 224. The rear end of the detent 222 is cylindrically enlarged at 226 and Slidably received within a counterbore 228 at the rear end of bore 220.

Counterbore 228 opens at its rear end into a slightly enlarged and threaded counterbore 230 which opens through the rear face of the housing 218. The threaded forward end 132 of lock nut 130, which is identical t0 that previously described, and a set screw 231 are threaded in counterbore 230, as shown. Received within the intermediate counterbore 228, and engaging at opposite ends the detent 222 and set screw 231, is a cornpression spring 232. A second compression spring 234 having one end engaged in a lateral bore in lever 24', adjacent its pivotal axis, and its other end engaging the bottom of the slot 30 in the fulcrum block 32 for the lever 24' "biases the latter in a counterclockwise direction. The modified wrench of FIGS. 9-l2 is otherwise identical in construction to the magnetic wrench previously described and, therefore, no further structural description of the modified wrench is deemed necessary.

The mechanical version of the wrench is used in precisely the same way as the previous magnetic wrench. Thus, a torque load is applied to a work element by rotating the wrench handle 10 in a clockwise direction as viewed in FIG. 9. The reaction or resisting torque on the pin 12 of the wrench results in a clockwise reaction torque on the lever 24. Clockwise rocking of the lever, however, is normally prevented by engagement of the corner 210 of the latch plate 204 with the conical end 224 of the detent 222, as may be most readily observed in FIG. 9 At this time, therefore, connection 16 serves as a rigid connection between the wrench handle 10 and pin 12 whereby the latter is rotated in a clockwise direction with the wrench handle to apply a torque load to the work element.

It will be observed that the clockwise torque on the lever 24 urges the corner 210 of the latch plate 202 against the conical tip 224 of the detent 222. This, in turn, produces an axial camming action on the detent tending to depress the latter rearwardly against the aotion of its spring 232. When the applied torque load reaches a predetermined magnitude, this axial camming force becomes suicient to cam the detent to a position wherein it clears the corner 210 of the latch plate, thereby releasing the lever 24 for clockwise pivoting in the wrench handle. This release of the lever 24 releases the connection 16 for limited turning of the handle 10 relative to the pin 12 which affords an indication to the user of the tool that the torque release setting of the wrench has been reached, as before.

When the wrench is removed from the work element, spring 234 returns the lever 24 to its normal position. During this return of the lever, the latch plate 202 again engages the detent 222 and is pivoted against the action of its biasing pin 216 (FIG. l2) to a position wherein the corner 210 of the latch plate can ride past the tip of the detent. Upon pivoting of the lever 24 to its normal position, the spring-pressed pin 216 cams the latch plate 202 back to its normal position, so that the connection 16' is reset for the next use of the wrench.

The fulcrum block 32 is connected to an adjusting rod 236 in the same manner as the fulcrum block 32 in the wrench of FIGS. l-Sa. This rod is slidable in a lug 238 on the housing 2118 and held in a fixed axial position by threaded adjusting sleeves 240 on the rod at opposite sides of the lug. Thus, rod 236 and block 3,2 may be shifted relative to housing 218, to adjust the point of contact of latch plate corner 210 with detent 222, by turning of the adjusting sleeves 240. This is done at the time of manufacture of the wrench.

It is evident that the torque release setting of the |wrench may be varied by the user of the tool by rotation of the sleeve handle 94 on the wrench handle 1t) to shift the point of engagement of the knife edge fulcrum 40' of the lever 24' along the lever 22, as before. It is also evident that the magnitude of the applied torque load at which the connection 16" releases, for any given position of adjustment of the sleeve handle 94, is dependent on the tension of the detent biasing spring 23124 That is, the greater the tension of this spring, the greater will be the torque release value of the wrench for any given setting of the sleeve handle. Reducing the tension of the spring 232, of course, has an opposite effect. It will be clear, therefore, that the range of torque settings of the wrench may be varied, by adjustment of the set screw 231 to increase or decrease the tension of the spring 232. Thus, several wrenches of the type illustrated in `FIGS 9-12, which are identical in construction, may be provided with different ranges of torque release values by adjustment of the set screw.

Clearly, therefore, there has been described and illustrated a predetermined torque release wrench which is fully capable of attaining the several objects and advantages preliminarily set forth.

While certain perferred embodiments of the wrench have been described and illustrated, numerous modifications in design and arrangement of parts are possible within the scope of the following claims.

I claim:

1. A predetermined torque release wrench comprising a handle, a torque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable restraining means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said releasable means releasing said arm to swing in said given direction when has said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, and means on the handle for adjusting the point of application of said preset force on the arm lengthwise of the latter to change the troque release value ofv the wrench.

2. A predetermined torque release wrench comprising a handle, a Atorque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable snap-action means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said snap-action means abruptly releasing said arm to swing in said given direction when said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, and means on the handle for adjusting the point of application of said preset force on the arm lengthwise of the latter to change torque release value the wrench.

3. A predetermined torque release wrench comprising a handle, a torque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one `direction on the handle when the arm is restrained against swinging in a given direction on the handle, mechanical, spring-controlled snapaction means on the handle for exerting a preset -force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said snap-action means abruptly releasing said arm to swing in said given direction when said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, `and means on the handle tfor adjusting the point of application of said preset force on the arm lengthwise of the latter to change the torque release value of the wrench.

4. A predetermined torque release Wrench comprising a handle, a torque applying member mounted on the handle for turning on a given `axis with respect to the handle, a pivoted -arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable magnetically controlled snapaction means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm `against swinging in said given direction on the handle until a predetermined torque load is 4applied to a workpiece through said member, said snap-action means abruptly releasing said yarm to swing in said given direction when said predetermined torque load is attained whereby the handle turns with respect to said member to -ind-icate said predetermined torque load, and means on the handle for adjusting the point of application of said preset force on the arm lengthwise of the latter to change the torque release value of the Wrench.

5. A predetermined torque release wrench comprising a handle, a torque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable restraining means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is -applied to a workpiece through said member, said releasable means releasing said arm to` swing in said given direction when said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, means on the handle for adjusting the point of application of said preset force on the arm lengthwise of the latter to change the torque release value of the wrench, indicia on the handle associated with said adjusting means for indicating the torque release value of the wrench for different settings of said adjusting means, and calibration adjustment means for adjusting the point of application of said preset force on the larrn lengthwise of the latter independently of said rst-mentioned adjusting means whereby to change the torque release value of the wrench without changing the torque release value indicated by said indicia.

6. A predetermined torque release wrench comprlsing a tubular wrench handle, a torque applying member pivoted on the handle for turning on a transverse axis of the handle, a pivoted arm within and swingable on a transverse axis of the handle, the arm extending generally longitudinally of the handle, means operatively connecting the said arm to said member for restraining the latter against turning in one direction with respect to the handle when the arm is restrained against swinging in a given direction on the handle, -releasable restraining means within the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said releasable means releasing said arm to swing in said given direction when said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, and means operable exteriorly of the handle for adjusting said releasable means lengthwise of the handle to shift the point of application of said preset force on the arm lengthwise of the latter to change the torque release value of the wrench.

7. A predetermined torque release wrench according to claim l wherein said means operatively connecting the arm and member comprises a torque reduction means whereby a given torque applied to said arm to restrain the latter against swinging in said given direction and produced by a given preset force on the arm balances an appreciably greater torque acting on said member in a direction to turn the member in said one direction on the handle.

8. A predetermined torque release wrench comprising a handle, a pivoted torque applying member on the handle, a lever pivoted on the handle, a force reduction connection between said member and said lever including a radial arm rigid on said member and pivoted lever means on the handle engaging between said arm and lever for restraining said member against turning in one direction on the handle when said lever -is restrained against swinging in a given direction on the handle, releasable restraining means on the handle for exerting a preset force to a part of an arm of said lever in a direction to restrain the latter against swinging in said given direction until a predetermined applied torque load is applied to a workpiece through said member, and means on the handle for adjusting the point of application of said preset force on said lever arm lengthwise of the latter whereby to change the torque release value of the wrench.

9. A predetermined torque release wrench comprising a handle, a torque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means for operatively connected said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable restraining means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said releasable means comprising a movable support on the handle, a lever pivoted on said support and having an arm engaging a part of said first-mentioned arm to resist swinging of the latter arm in said given direction when said lever is restrained against swinging in a predetermined direction on the support, snap-action means on the support for exerting a preset force on said lever in a direction to restrain the latter against pivoting in said predetermined direction on the support until a predetermined torque is applied to a workpiece through said member, and means to adjust the support on the handle to shift the point of contact of the lever arm with said first-mentioned arm whereby to change the torque release value of the wrench.

10. A predetermined torque release wrench according to claim 9 in which said snap-action means comprises a mechanical, spring-controlled snap-action means carried on the support.

l1. A predetermined torque release wrench according to claim 9 in which said snap-action means comprises a magnetically controlled snap-action means carried on the support.

12. A predetermined torque release wrench according to claim 9 in which said handle comprises a tubular handle enclosing said arm, lever and support, said arm and lever extending generally longitudinally of the handle, and said support being longitudinally adjustable within the handle.

13. A predetermined torque release wrench comprising a handle, a torque applying member mounted on the handle for turning on a given axis with respect to the handle, a pivoted arm on the handle, means operatively connecting said arm to said member for restraining the latter against turning in one direction on the handle when the arm is restrained against swinging in a given direction on the handle, releasable restraining means on the handle for exerting a preset force on a part of the arm in a direction to restrain the arm against swinging in said given direction on the handle until a predetermined torque load is applied to a workpiece through said member, said releasable means releasing said arm to swing in said given direction on the handle when said predetermined torque load is attained whereby the handle turns with respect to said member to indicate said predetermined torque load, means to adjust the magnitude of said preset force, and means on the handle for adjusting the point of application of said preset force on the arm lengthwise of the latter to change the torque release value of the wrench.

14. A predetermined torque release wrench according to claim 13 wherein said releasable means comprises a spring-controlled snap-action means, and said preset force adjusting means comprises means to adjust the tension of the spring in said snap-action means.

l5. A predetermined torque release wrench according to claim 13 in which said releasable means comprises a magnetically controlled snap-action means including a magnet and an armature, and said preset force adjusting means comprises means to adjust the air gap between said magnet and armature.

16. A predetermined torque release wrench according to claim 9 including means to adjust the magnitude of said preset force.

17. A predetermined torque release wrench according to claim 9 wherein said lever comprises a rst class lever, one end of which engages saidrst-rnentioned arm, said preset force being exerted on the other end of the lever.

18. A predetermined torque release wrench according to claim 17 including means to adjust the point of application of said preset force on said lever lengthwise of said other end of the lever to change the torque release value of the wrench.

References Cited in the le of this patent UNITED STATES PATENTS Garwood l Feb. 2, 1954 Livermont Jan. 31, 1956 Woods May 1, 1956 Woods Apr. 23, 1957 Johnson et al. May 7, 1957 Walraven et a1. May 2l, 1957 Paterson Nov. l2, 1957 Aijala May 26, 1959 Livermont May 26, 1959