US3016773A

US3016773A - Predetermined torque release wrench

Info

Publication number: US3016773A
Application number: US779891A
Authority: US
Inventors: Woods Robert Glen
Original assignee: Individual
Current assignee: KD Manufacturing Co
Priority date: 1958-12-12
Filing date: 1958-12-12
Publication date: 1962-01-16
Anticipated expiration: 1979-01-16

Description

R. G. wooDs 3,016,773

PREDETERMINED TORQUE RELEASE WRENCH 2 Sheets-Sheet 1 ilu @s Jan. 16, 1962 Filed Deo. 12, 1958 mw f NEN/nl W We? G/f r r A E. E mM @j Jan. 16, 1962 R. G. woons 3,016,773

PEEDETEEMINED TORQUE RELEASE WRENCH Filed Dec. 12, 1958 2 Sheets-Sheet 2 e4 rraeA/ y:

Patented Jan. lb', 1952 dee 3,016,773 PREDETERMENED 'EQRQUE RELEASE WRENCH Robert Glen Woods, 3102 Grand Ave., Huntington Park, Calif. Filed Dec. l2, 1953, Ser. No. 779,391 28 Claims. (Ci. 8l52.4)

The present invention relates generally to wrenches and more particularly to an improved adjustable torque wrench of simplied design.

A variety of torque wrenches have been heretofore marketed and devised that are assembled from ostensibly identical parts. Each of these parts theoretically must be held to extremely close tolerances, but due to their geometry it is impractical to obtain these tolerances with consistency. The resulting torque wrenches, while apparently being composed of identical parts, are actually composed of parts which are not identical. Accordingly, it is common practice in the manufacture of such wrenches to provide integral means for Calibrating the wrench prior to the time it leaves the factory, in order to compensate for errors in manufacturing tolerances. Once the wrenches have reached the iield, if any breakage or deterioration of the parts occurs the wrench must be returned to the factory in order to be recalibrated when new parts are substituted.

A major object of the present invention is to provide a torque wrench comprising a combination of parts of simple geometry each of which readily can be held to close tolerances in order to produce torque wrenches which do not require integral adjustment means to compensate or errors in manufacture.

Another object of the present invention is to provide a torque wrench having a geometry which enables the wrench to be repaired by the user in the eld without changing the calibration of the wrench.

It is also an object of the present invention to provide a torque wrench utilizing a cylindrical pivot or cam element adapted for breaking of the wrench within an extremely narror range of critical limits. When the load approaches the predetermined limit tor which the wrench is set, the wrench will break immediately upon the load on the wrench exceeding the preset limit.

Another object of the present invention is to provide a torque wrench of this type in which any force applied to the handpiece in a direction other than the plane of the torque to be measured is absorbed by the wrench without affecting the present breaking point of the wrench.

It is also an object of the present invention to provide an adjustable torque wrench with a simplied locking means to prevent variation from a predetermined torque limit for which the wrench has been adjusted.

An additional object of the present invention is to provide an adjustable torque wrench having a simple design and a rugged construction whereby it will afford a long and useful service life.

These and other objects and advantages of the present invention will be apparent from the following description, when taken in conjunction with the appended drawings wherein:

FIGURE l is a longitudinal vertical sectional view of an adjustable torque wrench embodying the present invention;

FIGURE 2 is a reduced fragmentary sectional view of said wrench, with portions partly broken away in longitudinal section;

FIGURE 3 is a transverse sectional view, on an enlarged scale, taken along line 3--3 of FIGURE l;

FIGURE 4 is a transverse sectional View, on an enlarged scale, taken along the line 4-4 of FIGURE 1;

FIGURE 5 is a partial longitudinal Section of the Wrench in the area 5 of FIGURE l and on an enlarged scale;

FIGURE 6 is a transverse sectional view taken on line 6 6 of FIGURE l;

FIGURE 7 is a transverse sectional view taken on line 7-7 of FIGURE 1;

FIGURE 8 is an elevational View partly in section and on an enlarged scale of an alternate form of cam or pivot element for utilization with said wrench;

FIGURE 9 is an elevational View, with parts broken away and in section, of an alternate form of lock means;

FIGURE l0 is a transverse sectional View taken on the line 10-10 of FIGURE 9 showing details of the interior construction of the lock means ot FIGURE 9;

FIGURE ll is a view similar to FIGURE 9 and showing the alternate form of lock means in locking position; and

FIGURE l2 is a sectional view on an enlarged scale of the area 12 in FIGURE 11.

Referring to the drawings, a preferred form of adjustable torque wrench embodying the present invention broadly comprises a head 2t having a rigid downwardly projecting load-engaging member 2i and a pivotally mounted rearwardly projecting hinge member 22. The rearwardly projecting hinge member 22 is disposed within the forward end oi a tubular lever member 23 and, in turn, pivotally suports the lever member 23 for movement about an axis that is normally concentric with the axis of rotation of the load member 21. At its rear end the lever member 23 carries a threadedly adjustable hand hold 24- that is drivingly engaged with a compression spring 25 enclosed within the lever member 23. The forwardend of the spring 25 abuts a plunger 26 and a cam or pivot member 27 is interposed between the forward end of the plunger 26 and the rear end of the hinge member 22. As will be apparent, rotation of the hand hold 24 will vary the compressive force of the spring 2S. Variation of the latter in turn will vary the torque at which the camming element or member 27 will break to permit relative angular movement to take place between the hinge member 22 and the lever member 23. When the operator feels such breakingj he is made aware that the torque applied by the load-engaging member 21 has reached the preset limit.

More particularly, the head Ztl is formed with an axially extending passage or counterbore 28 of oblate cylindrical conguration. The smaler end 28a of the counterbore is flattened at the poles of its minor axis and adapted to slidably receive the forward end of the hinge 22 as shown in FIGURE 1, and has a major axis greater than the diameter of the forward end of the hinge 22, as shown in FIG- URE 2. A vertical pin 29 pivotally interconnects the hinge 22 and head 20 through the smaller end 28a of the passage and has its axis coincident with the minor axis of the opening 28a. Since the pin 29 is offset but parallel to the axis of the load-engaging member 21, a slight lost-motion is permitted between the head 26 and the hinge 22, the hinge 22 being s'ightly angularly movable within the head 20. This relationship is indicated in FIGURE 2.

The larger rear end 28h of the passage 2S is flattened at the poles or its minor axis and adapted to slidably receive the outer diameter of the tubular cylindrical lever member 23. A pivot pin Sti interconnects the lever 23 and hinge 22 for relative angular movement about an axis normally aligned with the axis of the load-engaging member 2l. Since the major diameter of the passage 28 is substantially larger than the outer diameter of the lever 23, an appreciative amount of limited relative angular movement is possible between the head member 20 and the lever 23, as is indicated in FIGURE 2. rIbis limit is irnposed by contact of the lever 23 with one side ofthe opening 28h at a point coincident with the intersection of the major axis and thesurface defining the opening 28h. This limit preferably occurs coincidentally with the engagement of the hinge 22 with the side Wall of lever 23.

In order to permit relative angular movement between the lever 23 and the hinge 22, a ball and socket type of construction is utilized in these parts around the pivot pin 3i?. Referring to FIGURE 5, it will be observed that the hinge 22 is formed with a rearwardly facing convex shoulder 35i comprising a segment of a spherical surface having the radius R whose center is coincident with or lies on the longitudinal axis 32 of the wrench as a whole. A complementary and concentric concave ball shoulder 33 is formed in the forward end of the lever 23. These two shoulders permit free relative angular movement of the lever 23 and hinge 22 and within the range of such relative angular movement, portions of the interior diameter surface of lever 23 and hinge 22 are at all times in contact. The contacting surfaces of the hinge 22 and lever Z3 also provide a seal which will prevent the escape of lubricant from within the lever 23.

To limit relative angular movement of the lever 23 and hinge 22, the hinge is conically tapered to a reduced diameter. The rear end face of the hinge 22 is formed with a sloping-sided cavity 34. The width of cavity 34 approximates the diameter of the cylindrical cam member 27. A rearwardly tapering truncated frusto-conical depression 35 is centrally formed in the forward face of the plunger 26 with a bottom diameter equal to that of cam 27. The sloping walls of both

depressions

34 and 35 have an angle suiiicient to permit canting or shifting of the cam 27 from side to side without contacting the walls of the

depressions

34 and 35. Thus, when the wrench breaks with the parts assuming the positions shown in FIGURE 2, the cam 27 contacts each of the

depressions

34 and 35 in but a single point. It will be appreciated that upon the slightest shifting of the cam 27 out of coaxial alignment with the hinge 22 such point to point contact occurs immediately so that an extremely sensitive breaking point is achieved with this construction.

When the wrench is in the condition illustrated in FIG- URE 2, the neutral axis of the cam 27, in conjunction with the points of contact of the cam with the hinge 22 and plunger 26, will deiine a plane through which force is transmitted between the hinge 22 and the plunger 26. In order for the point at which the wrench actually breaks to truly reflect the torque limit for which the Wrench is set at that time it is desirable that this plane be exactly coincident with the plane in which torque is actually being applied to the load. Accordingly, the passage 28 in the head 2@ is formed with the aforementioned oblate conguration. When force is applied to the handhold 24 of the wrench having components which resolve themselves into planes other than the plane in which torque is transmitted to the load, these other forces will tend to be directly absorbed by the head Ztl, hinge 22 and lever 23. In other words, for a given input force applied to the handle 24, an equal resultant force will not always be applied to the load member 21 within the plane of the app'ied torque. Some of the input force will be dissipated in planes other than the plane of the applied torque. With the arrangement just described, only the actual resultant forces applied within the plane of the applied torque will have any effect in causing breaking of the wrench. Thus, if the user of the wrench exerts a force only in a plane normal to the plane of the applied torque, such force will be directly absorbed by the direct connection between the head 20, hinge 22 and lever 23. Other forces which resolve themselves into planes between the plane of the applied torque and a plane normal to that of the applied torque will be reflected in the plane of the applied torque only in proportion to vector resultants within the plane of the applied torque.

In order to adjust the aforedescribed torque wrench to a desired torque limit, the compressive force of the spring 4 25 can be varied by rotation in an appropriate direction of the handhold 2d. The tubular handheld 24 is adapted for telescopic slidable movement on the lever 23 with its rear end being closed by an end wall 36. A central opening 37 is formed in the end wall 36. This opening 37 has a driving connection with a splined reduced-diameter rear end portion 38 of a cylindrical drive member 39 which is coaxially disposed within the rear end of the lever 23. in order to compensate for variations in the spring rates of ostensibly identical springs 25, one or more adjustment washers 4G may be mounted on the rear end 3S of the drive member 39. These washers 4t) are held in place between the rearwardly-facing shoulder of the drive member 39 and the inside face of the end wall 36 of the handhold 24. The splined rear end 33 of the drive member 39 at its extreme end threadedly receives a nut 41 that locks the drive member 39 and washers Ait) rigidly in place.

The rear end of the lever 23 is internally threaded, as indicated at 42, for the reception of an adjustment nut 43. This adjustment nut 43 has a novel driving engagement with the drive member 39. The adjustment nut 43 is slidably mounted on the forward end of the drive member 39 and is formed with a pair of diametrically opposed transverse bores 44 adapted to slidably receive outer ends of a drive pin 55. The drive member 39 is formed with a diametrically extending passage 46 in which the drive pin 45 is received in a universal joint connection. For this purpose, the opposite radial halves of the passage 46 have a rectangular cross-sectional configuration having an intersection adapted for slidable re ception of the drive pin 45. The passage te has a width transversely of the wrench axis adapted to receive pin 45 in a close sliding fit to provide a positive driving connection of the drive member 32, pin 45 and adjustment nut 43. However, the opposite sides of each radial half of the passage 46 that are spaced apart along the longitudinal axis of the wrench, are tapered to engage the pin i5 at its midpoint. inasmuch as the inner diameter of the adjustment nut 43 has a slidable clearance with `the drive member 39, a slight amount of shifting is permitted between these two members. Accordingly, any misalignment of these parts can be compensated for by the aforedescribed universal joint arrangement inasmuch as the center of the passage i5 will tend to center itself on the drive pin 45.

From the foregoing it will be apparent that rotation of the handhold 24 will result in axial movement of the drive member 35 in order to alter the compressive force of the spring 25. However, it is desirable that rotation of the drive member 3% should not be drivingly transmitted to the spring 25 inasmuch as the influence of torque on one end of the spring 25 may affect the accuracy of the wrench. In order to avoid any tendency of the spring 25 to rotate along with the drive member 39, a disc 47 is disposed between the rear end of the spring 25 and a small diameter crown 43 centrally formed on the forward end of the drive member 39. Since the crown 43 engages the center of the disc 47 over an area which is extremely small, there will be little tendency for rotation of the drive member 39 to be transmitted to the spring 25.

As is indicated in FIGURE l, the plunger 26 and hinge 22 are spaced apart a distance X when the wrench is in unbroken condition. Referring to FEGURE 2, it will be seen that when the wrench breaks, the spacing between the plunger 25 and hinge 22 will be elongated, due to the camming action of the cam 27', to a distance Y. As a result, there will be a change in the internal volume Within the lever 23 forwardly of the plunger 26 and rearwardly of the plunger 26. Accordingly, it is desirable to provide a means for the free passage of air between opposite ends of the plunger 26 in order that the air within the lever will not be compressed concurrently with breaking of the wrench, such air compression causing inaccurate results.

In order to avoid such air compression, the plunger 26 preferably is made from a piece of hexagonal stock material, as indicated in FIGURE 3. The plunger 26 will then contact the interior surface of the lever 23 only at spaced-apart points leaving a relatively large volurne of clearance space between the flat surfaces of plunger 26 and the lever Z3. With this arrangement, the passage of air between opposite sides of the plunger is facilitated and no air compression -Will take place. It should also be noted that the multi-sided plunger 26 pr-ovides more than one longitudinally extending line of contact between the plunger and lever '23. Accordingly, the unit stresses imposed on the plunger Z6 when an input force is applied to the lever 23 are reduced. Frictional resistance to sliding of the plunger 26 upon breaking of the wrench is `also reduced and the wrench is therefore made more accurate.

In order to provide `lubricant reservoirs for the axially shiftable plunger 26, the plunger is formed with a plurality of reduced-diameter portions 26a adapted to receive a sufficient quantity of lubricant.

A lock ring 9 is provided on the handhold 24 to maintain the compression of spring 25 at a selected torque limiting force. This lock. ring is mounted on the forward end of the handhold 24 against a forwardly-facing shoulder 50 formed in the handhold and held against this shoulder to prevent relative axial movement by a lock nut 51 that is threadedly engaged with a reduceddiameter externally threaded forward end portion of the handhold 24.

In order to maintain the wrench at a selected torque limit for which it is set, the lock ring 49 is provided with the mechanism seen in FIGURE 6, which is similar'to the locking mechanism disclosed in my Patent No. 2,731,855 issued January 24, 1956. Accordingly, this mechanism need not be described in detail. Suffice it to say that the portion of the lever 23 underlying the forward portion of handhold 24 is formed with a plurality of longitudinally extending grooves 52 cor-responding in number to the Vernier graduations on the forward end of the handhold '24. rihese grooves are adapted to receive one end of a locking butt-on 53 that is slidable through -a 'bore 54 formed in the handhold 24 in a portion immediately underlying the lock ring 49.

An arcuate spring 'finger 55 is also connected at one end to the handhold 2d and at its free end this spring carries the locking button 53 for movement into and out of engagement with slots 52 through the bore 5d. In order to accommodate the spring finger 53, the lock ring S9 on its inner surface is formed with a spring pocket 56 having an arcuate length of approximately twice that of the spring finger 55, s-o that the lock ring 49 is capable of limited angular movement relative to the handhold Z4. At one end the pocket 56 is formed with an enlarged recess 57 so that when the parts are in the position shown in FEGURE 6 the locking button 53 can be moved out of engagement with the groove $2 by rotation of the handhold 2d, the recess 57 permitting sufficient outward movement of the locking button 53. When the lock ring i9 is rotated in a clockwise direction from the position in FGURE 6, while the handhold 24 is held against rotation, the locking button 53 is prevented from moving radially outwardly of the groove 52 due to the shallowness of the pocket 56.

As thus far described, this locking mechanism is substantially the same as that disclosed in my aforesaid Patent No. 2,731,865. However, the present locking mechanism provides a more positive indication of when the locking ring is in locked and unlocked position because of the following construction. Thus, it will be noted that the handhold 24 in `a portion immediately underlying an intermediate portion of the spring finger 55 is relieved by a flat surface S8, above which a radially outwardly projecting dimple 59 is formed in the spring finger 5. The pocket 56 of the lock ring 49 is formed in two steps; a relatively shallow step 56a in that end of the pocket opposite to the enlarged recess 57, and a slightly deeper step 56h in that portion of the pocket S6 immediately adjacent the recess 57. A shoulder 6ft is thus formed at the junction of the steps 56a and Sb. A cavity 61 is formed in the shallow step 56a and is adapted to receive the dimple 59 of the spring linger 5S.

In FIGURE 6 the lock ring 49 is shown in unlocked position so that when the handhold 241 is rotated the lock button 53 is cammed out of the grooves 52 by the sides of the grooves, such displacement of the locking button being permitted by the enlarged recess 57 of the lock ring 49. The distance between the grooves 52 is such that each click which occurs upon camming of the lock button out of a groove 52 will indicate a definite change in foot pounds or inch pounds.

After a desired torque limit has been set into the wrench by rotation of the handhold 241, the lock ring 49 is then rotated in a clockwise direction as viewed in FIGURE 6. When this occurs, the shoulder 60 will first ride over the dimple 59 of the spring nger 55 to depress the spring into the relief 58 of the handhold 24. When the cavity 61 is in registration with the dimple 59, the dimple will engage the cavity and this resurgence of the spring can be felt on the lock ring 49. At the same time the fixed end of the spring finger S5 will engage the counterclockwise end of the pocket 56 and the step 56b will be disposed above the lock button 53 to reta-in it in the selected groove 52. rl`he wrench is thus securely locked in the desired setting so that when manual force is applied to the handhold 24 this input force will not cause any relative rotation between the handhold and the lever 23 and the desired compression of the spring 25 remains unaffected.

When it is desired to unlock the wrench for adjustment to a new torque limit, the lock ring 49 is rotated counterclockwise into the position shown in FIGURE 6. Such rotation of the lock ring first causes depression of the dimple 59 into the relief 5S due to the camming action of the walls of the cavity 61. Thereafter, the shailow step 56a rides over the dimple S9 until the shoulder 6ft has been rotated past the dimple. The dimple 6i) is then permitted to spring outwardly into the deeper step Sb and the passage of the shoulder 69 over the dimple can be felt on the lock ring 49. This arrangement, therefore, gives a positive indication that the lock ring 49 is now in completely unlocked position with the enlarged recess S7 disposed immediately over the locking button 53.

An `alternate form of locking mechanism of greater simplicity is shown in FGURES 9 through 12. ln this forni a tubular handhold 62 is provided which is similar' to the handhold 24 but has a reduced-diameter forward end portion that slidably supports a tubular locking ring 63. As before, the lever 23 is formed with a plurality of longitudinally extending grooves 52 in the portion underlying the forward end of the handhold 62 and the handhold is formed with a bore 6d adapted to receive a locking device which in this instance takes the for of a ball 65.

The lock ring 63 on its inner surface is formed with an axially disposed slot 66 of varying depth and having a w-idth adapted for the reception of the locking ball 65. As can be seen in FIGURE 9, the slot 66 at the rear end of the lock ring 63 merges into the inner diameter of the locking ring and increases in depth forwardly to terminate in a rearwardly-facing internal shoulder 67. The lock ring 63 is thus held against rotation relative to the handhold 62 but is axially slidable between a rearward, unlocked position and a relatively forward, locked position.

The locking ball 65 has a diameter greater than the wall thickness of the surrounding portion of the hand hold 62. Therefore, when the parts are in the unlocked position of FIGURE 9 rotation of the handheld 62 causes the ball 65 to be c-ammed outwardly by the sidewalls of the groove 52 of the lever 23, the ball 65 being received in the forward end portion of greatest depth of the slot 66. After the handheld 62 has been set for a desired torque limit of the wrench the lock ring 63 is slid forwardly into the position of FIGURE ll wherein the ball 65 is wedged between a shallower portion of the slot 66 with its inner side against a locking groove S2.

In order to give positive indication of locked and unlocked positions of the lock ring 63, the ring on its inner surface is formed with an annular groove 66 that carries a snap ring 69. This snap ring 69 has a normal contracted diameter less than the outer diameter of the handheld 62.. The groove 68 has a depth at least as great as the gauge or thickness of the wire material of snap ring 69 so that the snap ring can be expanded completely into the groove 68 to be carried along with the lock ring 63 over the outer diameter of the handheld 62.

The handheld 62 is formed with a pair of circumferential-ly extending grooves 7i) and '71 both of which have a depth less than the radius of the wire material of the snap ring 69. The groove 71 is spaced rearwardly of the groove 76 to intersect the ball holding bore 64. Thus, whenever the lock ring 63 is axially shifted along the handhold 62, the snap ring 69 will contract into engagement with either the groove 7i) or 71 to yieldably resist further axial movement of the lock ring, whereby the lock ring is positioned in locked or unlocked position as the case may be. In this regard, it will be observed from FIGURE 10 that the snap ring 69 has a length less than the circumference of the forward end portion of the handhold 62 so that the ends of the ring do not intrude into the slot 66 and will not obstruct relative movement between the lock ring and the handhold.

Referring now to FIGURE 8, there is shown a modified form of a cam member identified generally by the numeral '7 2. The member 72 is also of solid cylindrical form and comprises a base 73 formed with an integral reduceddiameter stem portion 74 extending coaxially from one end. A plurality of spacer Washers 75 of a thickness and number as desired are coaxially mounted on the stem 74 against the enlarged head of the base 73 and a relatively thick end spacer 76 than is coaxially mounted on the stem 74. It will be apparent that all of these parts will be held in assembled relationship by the force of the spring 25 when the modied cam member 72 is interposed between the rear end of the hinge 22 and the front end of the plunger 26. The modified cam member 72 will operate in precisely the same manner as the solid cylindrical cam 27 but provides a convenient means of changing the effective length of the cam for the p-urpose of changing the calibration of the wrench from inch pounds into foot pounds.

In operation, the aforedescribed wrench is adjusted to a desired torque limit by first unlocking the

lock ring

49 or 63, as the case may be, and rotating the handheld 24 or 62 in the appropriate direction to a desired torque limit setting, after which the lock ring is then returned to locked position. The head 2d is then applied to the load and manual force applied to turn the lever 23 in either a clockwise or counterclockwise direction. When the resistance of the load reaches the preset torque limit, the force of the spring 25 is overcome and compressed by the camming action of Kthe member 27, which permits slight angular movement of the lever 23 relative to the hinge 22. This breaking of the wrench can be felt when the hinge 22 contacts the wall of the lever 23.

It will be apparent that various modifications and changes may be made with respect to the wrench construction herinabove described without departing from G the spirit of the present invention or the scope of the fol-- lowing claims.

I claim:

l. A torque wrench, comprising: a head member formed with a load-engaging means and having a rearwardly extending hinge member through which a torque can be applied to said load-engaging means; a lever pivotally connected at its forward end to said hinge member; coacting surfaces on said hinge member and said lever to limit relative angular movement therebetween; a plunger axially movably mounted in said lever rearwardly of said hinge member; yieldable means interposed between said plunger and said lever to urge said plunger forwardly towards said hinge member; and a cam means interposed between and having opposite end flat faces abutting the rear of said 1ninge member and the front end of said plunger, said cam means, said hinge member and said plunger being normally held in coaxial alignment with said lever by the force of said yieldable means, and said yieldable means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge member and said lever within the limits of said coacting means, said cam means moving out of said coaxial alignment to translate said excessive force into said relative movement to cause said yielding, said faces of said cam means having single point contact with said hinge member and plunger when said yielding occurs.

2. A torque wrench as set forth in claim 1 in which said cam means comprises a cylindrical member interposed between said plunger and said hinge member and in which the ont end of said plunger and the rear end of said hinge member are each formed with a depression adapted to seat one end of said cylindrical cam in a manner to prevent sliding iof said end in said depression and also adapted to permit relative angular camming movement of said cam means, said cam means being normally held against said camming movement by said resilient means.

3. A torque wrench, comprising: a head member formed with load-engaging means and having a rear- Wardly extending hinge member through which a torque can be applied to said load-engaging means; a lever pivotally connected at its forward end to said hinge member; coacting means on said hinge member and said lever to limit relative angular movement between said hinge member and said lever; a plunger axially movably mounted in said lever rearwardly of said hinge member; resilient means interposed between said plunger and said lever to yieldably urge said plunger forwardly towards said hinge member; and a cylindrical cam interposed between said plunger and said hinge member, the front end of said plunger and the rear end of said hinge member each being formed with a depression for seating opposite ends of said cam and adapted to normally hold said cam in coaxial alignment with said plunger, said lever and said hinge member under the force of said resilent means, and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge member and lever within the limits of said coacting means, said cam translating said excessive force into said relative movement and into yielding of said resilient means.

4. A wrench as set forth in claim 3 in which said cam is of a uniform length and at least one of said depressions comprises a truncated, conical recess having a reduced diameter bottom of a diameter substantially equal to the diameter of said cam.

5. A wrench as set forth in claim 3 in which said cam is lof uniform length and at least one of said depressions is a sloping-sided slot parallel to the pivotal axis of said hinge and said lever, and having a reduced Width bottom complementary to the diameter of said cam.

6. A torque wrench, comprising: a head member formed with load-engaging means and having a hinge member extending rearwardly therefrom through a rearwardly facing opening formed in said head member, said opening being `of oblate cylindrical congur-ation ilattened at the pole areas of its minor axis and said minor axis lying in a plane including the axis of rotation of said load-engaging means; a tubular lever coaxially receiving said hinge member through the forward end thereof and pivotally connected at its forward end within said plane to said hinge member, the forward end `of said lever being received within said rearwardly facing opening of said head and having a ldimension in Said plane adapted for slidable angular movement on said flattened pole areas of said opening, said front end of said lever in the plane of the major axis of said oblate opening having a dimension less than said major axis to permit relative angular movement of said lever and said head; coacting means on said hinge member and said lever to limit relative angular movement therebetween; a plunger axially movably mounted on said lever rearwardly of said hinge member; resilient means interposed between said plunger and said lever to yieldably urge said plunger forwardly towards Said hinge member; and a cam means interposed between the rear of said hinge member and the from end of said plunger, said cam means, said hinge member and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means and said resilient means `yielding to an excessive force applied to said lever to permit relative angular movement of said hinge member and said lever within the limits of said coaoting means, said cam means translating said excessive force into said relative movement and into yielding of said resilient means.

7. A wrench as set forth in claim 6 in which the pivotal axis of said lever and said hinge is coaxial with the axis of rotation of said load-engaging means.

S. A torque wrench, comprising: a head member having a load-engaging means and formed with an axially extending passage therethrough of oblate cylindrical conguration attened at the pole areas of its minor axis and said minor axis lying in a plane including the axis of rotation of said load-engaging means; a hinge pivotally connected at its forward end to said head within said passage and extending rearwardly from said head, said hinge having a dimension in said plane adapted for slidable angular movement on said iiattened pole areas of said passage and having a dimension in the plane of the major axis of said passage less than said major axis to permit relative angular movement of said hinge and said head; a lever pivotally connected at its forward end to said hinge member; coacting means on said hinge member and said lever to limit relative angular movement therebetween; a plunger axially movably mounted on said lever rearwardly of said hinge member; resilient means interposed between said plunger and said lever to yieldably urge said plunger forwardly towards said hinge member; and a cam means interposed between the rear of said hinge member and the front end of said plunger, said cam means, said hinge and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means, and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge and said lever within the limits of said coasting means, said earn means translating said excessive force into said relative movement and into said yielding of said resilient means.

9. A torque wrench, comprising: a head member having a load-engaging means and formed with an axially extending counterbored passage therethrough including an enlarged rearwardly facing opening, said passage being of oblate cylindrical configuration flattened at the pole areas of its minor axis and said minor axis lying in a plane including the axis of rotation of said load-engaging means; a hinge pivotally connected at its forward end to said head in a smaller forward portion of said passage and extending rearwardly therefrom through said enlarged rearward ly facing opening, said hinge having a dimension in said plane adapted for slidable angular movement on said flattened pole areas of said forward portion of said passage and having a dimension in the plane of the major axis of said oblate forward portion of said passage less than said major axis to permit relative angular movement of said hinge and said head; a tubular lever coaxially receiving said hinge through the forward end thereof and pivotally connected at its forward end within said plane to said hinge, the forward end of said lever beingreceived Within said rearwardly facing opening of said head and having a dimension in said plane adapted for slidable angular movement on said flattened pole areas of said opening, said front end of said lever in the' plane of the major axis of said oblate opening having a dimension less than said major axis to permitirelative angular movement of said lever and said head; coacting means on said hinge and said lever to limit relative angular movement therebetween; a plunger axially movably mounted on said lever rearwardly of said hinge; resilient means interposed between said plunger and said lever to yieldably urge said plunger forwardly towards said hinge; and a cam means interposed between the rear of said hinge and the front en d of said plunger, said cam means, said hinge and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge and said lever within the limits of said coacting means, said cam means translating said excessive force into said relative angular movement and into yielding of said resilient means.

l0. A torque wrench as set forth in claim 9 in which said cam means is a cylindrical member of uniform length and in which the front end of said plunger and the rear end of said hinge are each formed with a depression adapted to seat one end of said cam means in a manner to prevent sliding of said end in said depression and further adapted to permit relative angular camming movement of said cam means.

l1. A wrench as set forth in claim l0 in which at least one of said depressions comprises a truncated conical recess having a reduced diameter bottom of a diameter substantially equal to the diameter of said cam means.

l2. A torque wrench as set forth in claim l0 in which at least one of said depressions is a sloping-sided slot parallel to the pivotal axis of said hinge and said lever and having a reduced width bottom complementary to the diameter of said cam means.

13. A torque wrench, comprising: a head member with a load-engaging means and having a rearwardly extending hlnge member of circular cross-section tapering to a reduced diameter rear end; a cylindrical lever adapted to coaxially receive said hinge member into a forward end portion of said lever, said lever having an inner diameter complementary to the diameter of a transverse circular `section of said tapered hinge and connected to said hinge for pivotal movement about a diametral axis` lying in a plane including the axis of rotation of said load-engaging means; ball and socket means formed in the `contacting surfaces of said hinge member and said lever and having a radius of curvature Whose center is coincident with the center of said diametral axis to permit relative angular movement of said lever and said hinge member, said tapered hinge member and the interior of said lever providing coacting means to limit said relative angular movement; a plunger axially movably mounted on said lever rearwardly of said hinge member; resilient means interposed between said plunger and said lever to yieldably urge `said plunger forwardly towards said hinge member; and a cam means interposed between the rear of s aid hinge member and the front end of said plunger, said cam means, said hinge and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of s aid hinge member and said lever within the limits of said coacting means, said cam means vtranslating said excessive force into said relative movement and into yielding of said resilient means.

14. A torque wrench, comprising: a head member having a load-engaging means formed with an axially extending counterbored passage of oblate cylindrical configuration including an enlarged rearwardly facing opening,

said passage being flattened at the pole areas of its minor axis and said minor axis lying in a plane including the axis of rotation of said load-engaging means; a hinge pivotally connected at its forward end to said head in smaller forward portion of said oblate passage and extending rearwardly therefrom through said enlarged rearwardly facing opening, said hinge having a dimension in said plane adapted for slidable angular movement on said flattened pole areas of said forward portion of said passage and having a dimension in the plane of the major axis of said oblate forward portion of said passage less than said major axis to permit relative angular movement of said hinge and said head; a tubular lever coaxially receiving said hinge member through the forward end thereof and pivotally connected at its forward end within said plane to said hinge member, the forward end of said lever being received within said rearwardly facing opening of said head and having a dimension in said plane adapted for slidable angular movement on said flattened pole areas of said opening, said front end of said lever in the plane of the major axis of said oblate opening having a dimension less than said major axis to permit relative angular movement of said lever and said head, said hinge being of circular cross-section tapering to a reduced diameter rear end and said lever having an inner diameter complementary to the diameter of a transverse circular section of said tapered hinge and connected to said hinge for pivotal movement about a diametral axis lying in said plane; ball and socket means formed in the contacting surfaces of said hinge and said lever and having a radius of curvature whose center is coincident with the center of said diametral axis to permit relative angular movement of said lever and said hinge, said tapered hinge and the interior of said lever providing coacting means to limit said relative angular movement; a plunger axially movably mounted on said lever rearwardly of said hinge member; resilient means interposed between said plunger and said lever to yieldably urge said plunger forwardly towards said hinge; and a cam means interposed between the rear end of said hinge and the front end of said plunger, said cam means, said hinge and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge and said lever within the limits of said coacting means, said cam means translating said excessive force into said relative angular movement and into yielding of said resilient means.

15. A torque wrench as set forth in claim 14 in which said cam means comprises a cylindrical member of uniform length and in which the front end of said plunger and the rear end of said hinge are each formed with a depression adapted to seat one end of said cylindrical cam, each of said depressions being formed with sloping sides tapering to a bottom oor of a reduced width complementary tothe diameter of said cam means and adapted to prevent sliding of said cam means and to permit relative angular camming movement of said cam means.

16. A torque wrench as set forth in claim 14 in which the pivotal axis of said lever and said hinge is coaxially disposed with the axis of rotation of said load-engaging member.

17. A torque wrench, comprising: a head member formed with load-engaging means and having a rearwardly extending hinge member through which a torque can be applied to said load-engaging means; a tubular lever adapted to coaxially receive said hinge member Ythrough the front end of said lever and pivotally connected at said front end to said hinge member; coacting means on said hinge member and lever to limit relative angular movement therebetween; a plunger axially slidably mounted in said lever rearwardly of said hinge member and having a cross-sectional configuration dissimilar to the cross-sectional configuration of the interior of said lever to provide air passage clearance space between said plunger and said lever; resilient means interposed between said plunger and said lever to yieldably urges said plunger forwardly toward said hinge member; and a cam means interposed between the rear of said hinge member and the front end of said plunger, said cam means, said hinge member and said plunger being normally held in coaxial alignment with said lever by the force of said resilient means and said resilient means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge member and said lever within the limits of said coacting means, said cam means translating said excessive force into said relative angular movement and into yielding of said resilient means.

18. A torque wrench as set forth in claim 17 in which said lever is of cylindrical configuration and said plunger is of polygonal configuration.

19. A torque wrench, comprising: a head member formed with load-engaging means and having a rearwardly extending hinge member; a tubular lever coaxially receiving said hinge member through the forward end of said lever and pivotally connected at its forward end to said hinge member; coacting means on said hinge member and said lever to limit relative angular movement therebetween; a plunger axially movably mounted within said lever rearwardly of said hinge member; spring means within said lever rearwardly of said plunger and interposed between said plunger and said lever to yieldably urge said plunger forwardly towards said hinge member; a cam means interposed between the rear end of said hinge member and the front end of said plunger, said cam means, said hinge member and said plunger being' normally held in coaxial alignment with said lever by the force of said spring means and adapted to translate an excessive force applied to said lever into relative an gular movement of said lever and hinge member and into yielding of said spring means; a tubular handheld telescopically mounted on the rear end of said lever; a drive member coaxially mounted within the rear end of said lever to abut the rear end of said spring means and rotatably drivingly engaged by said handheld; an adjustment nut threadedly engaged with the interior of said lever for axial adjustment along said lever and adapted to coaxially receive the forward end of said drive member; and means rotatably drivingly interconnecting said adjustment nut and said drive member and having a universal joint connection with said drive member whereby rotation of said handhold axially moves said nut and drive member to vary the force exerted by said spring, said universal joint connection serving to retain said drive member in axial alignment with said lever.

20. A wrench as set forth in claim 19 in which a disc is interposed between the rear end of said spring means and the front end of said drive member and said drive member is formed on its front end with a small central crown rotatably abutting the center of said disc, whereby actuation of said adjustment means is prevented from rotating said spring means by rotation of said crown on said disc.

21. In a torque wrench having spring means and means to adjust the force of said spring means, a locking mechanism for said adjustment means including: a cylindrical lever; a cylindrical handhold telescopically mounted on said lever; a drive means threadedly engage with said lever and drivingly engaged by said handheld and adapted to vary the force of said spring means in response to rotation of said handhold; a locking ball carried by a bore formed in the wall of said handhold and having a diameter greater than the wall thickness of said handhold; and a lock member mounted on said handhold for movement over said ball between locked and unlocked positions thereof, said lock member on its inner face having a cam surface that forces said ball to rotrude inwardiy beyond said handhold when said lock member is in locked position, whereby said ball is wedgingly seated by said lock member in one of a plurality of longitudinally extending grooves formed in said lever, said cam surface when said lock member is in unlocked position permitting said lock ball to be cammed out of said groove by the walls of said grooves.

22. A locking mechanism as set forth in claim 2l in which said lock member comprises a sleevelike ring axially slidably mounted on said handhold and said cam surface is defined by the bottom of a longitudinally disposed slot formed in the inner surface of said ring.

23. A locking mechanism as set forth in claim 22 in which said ring is formed with an internal annular groove intersecting said slot and a snap ring of lesser thickness than the depth of said slot is carried in said slot, and said handheld is formed with a pair of circumferentially extending grooves of lesser depth than one half the thickness of said snap ring and into which said snap ring is selectively releasably receivable by movement of said lock ring to said locked and unlocked positions corresponding with engagement of said snap ring with one or the other of said grooves.

24. In a torque wrench having spring means and means to adjust the force of said spring means, a locking mechanism for said adjustment means including: a cylindrical lever; a cylindrical handhold telescopically mounted on said lever; a drive means threadedly engaged with said lever and drivingly engaged by said handhold and adapted to vary the force of said spring means in response to rotation of said handhold; a locking button radially movable through a bore formed in the wall of said handhold, said button when inwardly depressed engaging one of a plurality of longitudinally extending grooves formed in said lever to prevent relative rotation of said lever and said handhold; a spring finger having one of its ends retained by said handhold and adapted to carry said button at its other end and formed with an outwardly pointing dimple intermediate the ends of said finger; and a lock ring journaled on said handhold over said spring finger and formed on its inner face with a pocket of greater circumferential length than said finger and in which said finger is enclosed, said pocket at one end having an enlarged recess within which said button is outwardly movable out of engagement with said grooves of said lever when Said ring is in an unlocked position, said pocket intermediate its ends having a shoulder for overriding said dimple of said finger and also having a cavity adapted to register with and receive said dimple when said ring is in a locked position to yieldably retain said ring in said locked position, said pocket having a depth to prevent movement of said button out of said grooves of said lever when said ring is in a position other than unlocked, said handheld under said finger being relieved to permit depression of said finger in response to said overriding engagement of said shoulder and said dimple.

25. In a torque wrench the combination, comprising: a head member having a load-engaging means; a hinge member hingedly connected to said head member and extending rearwardly from said head member, said members having coacting means to limit relative angular movement therebetween; a lever pivotally connected at its forward end to said hinge member, said lever and hinge member having coasting means to limit relative angular movement therebetween; a plunger axially movably mounted in said lever rearwardly of said hinge member and yieldably biased toward said hinge member; and a torque-limiting means between adjacent ends of said hinge member and said plunger for depressing said plunger when an excessive torque is applied to said load-engaging means.

26. ln a torque wrench the combination comprising: a head member having a load-engaging means; a hinge member hingedly connected to said head member on a hinge axis parallel to the axis of said load-engaging means, said hinge member extending rearwardly from said head member, said members having coacting means to limit relative angular movement therebetween; a lever pivotally connected at its forward end to said hinge member on a pivot axis in alignment with the axis of said load-engaging means, said lever and hinge member having coacting means to limit relative angular movement therebetween; a plunger axially movably mounted in said lever rearwardly of said hinge member and yieldably biased towards said hinge member; and a torque-limiting means between adjacent ends of said hinge member and plunger for depressing said plunger when an excessive torque is applied to said load-engaging means.

27. ln a torque wrench the combination comprising: a head member formed with a passage therethrough and having a load-engaging means whose axis is normal to the axis of said passage; a hinge member having its forward end receivable in said passage and hingedly connected to said head member on a hinge axis parallel to the axis of said load-engaging member, said hinge axis being spaced forwardly from the axis of said loadengaging member, said hinge member extending rearwardly from said head member, said members having coacting surfaces to limit relative angular movement therebetween; a tubular lever within whose forward end the rearwardly extending portion of said hinge member is received, said lever being pivotally connected at its forward end to said hinge member on a pivot axis in alignment with the axis of said load-engaging member, said lever and said hinge member having coacting means to limit relative angular movement therebetween; a plunger axially movably mounted within the rear end of said lever rearwardly of said hinge member and yieldably biased towards said hinge member; and a torque-limiting cam means interposed between and having opposite ends faces abutting the rear of said hinge member and the front end of said plunger, said cam means, said hinge member and said plunger being normally held in coaxial align* ment with said lever by said yieldably biased plunger.

28. In a torque wrench the combination comprising: a head member formed with a load-engaging means and having a rearwardly extending hinge member through which a torque can be applied to said load-engaging means; a tubular lever within whose front end the rearwardly extending portion of said hinge member is receivable, said lever being pivotally connected at its forward end to said hinge member, said lever and hinge member having Contact only through a ball and socket means defined on the interior surface of said lever and exterior surface of said hinge member in the region of the pivot axis of said hinge member and lever; coacting means on said hinge member and said lever to limit relative angular movement therebetween; a plunger axially movably mounted in said lever rearwardly of said hinge member; yieldable means in said lever to urge said plunger forwardly toward said hinge member; and a cam means interposed between the rear of said hinge member and the front end of said plunger, said cam means, said hinge :member and said plunger being normally held in coaxial alignment with said lever by the force of said yieldable means, said yieldable means yielding to an excessive force applied to said lever to permit relative angular movement of said hinge member and said lever within the limits of said coacting means, said cam means translating said excessive force into said relative movement to cause said yielding.

(References on following page) References Cited in the le of this patent 2,732,747 Livermont an. 31, 1956 2,743,638 Woods May 1, 1956 UNITED STATES PATENTS 2,789,454 Woods Apr. 23, 1957 2,686,446 Livermont Aug. 17, 1954 2,792,733 Walraven et a1. May 21, 1957 2,704,472 Booth Mar. 22, 1955 5 2,887,919 Aijala May 26, 1959 2,731,865 Woods Jau 24, 1956 2,837,921 Livermont May 26, 1959