Title of Invention	AN ADJUSTABLE TORQUE WRENCH
Abstract	An adjustable torque wrench capable of pre-setting specified torque values is disclosed which comprises an elongated housing and an output drive shaft. Pivotally secured to and located within the housing are a plurality of levers. A first lever is journalled to the output shaft for rotation therewith and the remaining levers are pivotally secured to the housing adjacent their first ends at spaced intervals along the longitudinal center line of the housing and, with the exception of the last of these levers, have second ends, which engage the first end of the next, adjacent lever whereby pivoting of the first lever results in pivoting of each of the levers through their interconnections. Further included is a torque value setting assembly which acts between the housing and at least one of the levers to apply a force to the lever which must be overcome in order for that lever to pivot. The torque value setting assembly is readily adjustable to alter the pivoting resistance by varying the position along the length of the lever upon which the device acts. The torque wrench includes an indicating arrangement which provides an audible indication when the torque value set by the torque value setting assembly has been reached.

Title of Invention

AN ADJUSTABLE TORQUE WRENCH

Abstract

An adjustable torque wrench capable of pre-setting specified torque values is disclosed which comprises an elongated housing and an output drive shaft. Pivotally secured to and located within the housing are a plurality of levers. A first lever is journalled to the output shaft for rotation therewith and the remaining levers are pivotally secured to the housing adjacent their first ends at spaced intervals along the longitudinal center line of the housing and, with the exception of the last of these levers, have second ends, which engage the first end of the next, adjacent lever whereby pivoting of the first lever results in pivoting of each of the levers through their interconnections. Further included is a torque value setting assembly which acts between the housing and at least one of the levers to apply a force to the lever which must be overcome in order for that lever to pivot. The torque value setting assembly is readily adjustable to alter the pivoting resistance by varying the position along the length of the lever upon which the device acts. The torque wrench includes an indicating arrangement which provides an audible indication when the torque value set by the torque value setting assembly has been reached.

Full Text	The invention relates to an adjustable torque wrench which is capable of being preset to specific torque values and which includes a means for indicating when the specified torque is reached J and a means to prevent over torturing. Torque wrenches which can be set to desired torque values are known in the art. Such torque wrenches substantially reduce the time and effort for setting a specific torque when tightening bolts, nuts, spark plugs, etc. In one known type of prior art arrangement, an externally threaded shaft is received within an internally threaded tube for the purpose of setting the torque value. Over time, wear and tear will occur on the threads between the shaft and tube which results in a reduction in the accuracy of the torque setting system. It is also known in the art of torque wrenches to have a torque release connection between a manually engageable handle and a torque applying member. In these types of wrenches, represented by U.S. Pat.Nos. 2,996,940 and 3,355,970, the torque setting value of the wrench can be adjusted by varying the mechanical advantage of the level-type connection between the wrench handle and the torque applying member. When a preset torque value has been reached, the releasable connection between the member and the handle prevents further torque application through the torque-applying member. The release of this connection provides an abrupt indication that the desired, preset torque limit has been reached. Therefore, based on the above discussed prior art. there exists a need for a torque wrench having an adjustable torque setting which requires no recalibration and which will not loose its accuracy over a long period of time. There also exists a need for an adjustable torque wrench which can provide a readily determinable, non-abrupt indication when the preset torque value has been reached. It is therefore the object of the present invention to provide an adjustable torque wrench having a readily and accurately adjustable torque value setting mechanism in the form of a spring based slide assembly and a means for indicating, preferably audible, when the preset torque value has been reached and a means for preventing over torquing. The present invention relates to a torque wrench capable of pre-setting specific torque values. The torque wrench comprises an elongated housing which rotatably supports an output drive shaft. The torque on the output drive shaft is transmitted through a plurality of levers which are pivotally mounted within the housing. One of the levers is corralled to the output drive shaft for rotation therewith and the remaining levers are pivotaliy secured to the housing adjacent first ends thereof along the longitudinal center line of the housing. In the preferred embodiment, three such levers are utilized. The second end of each of the three levers are engaged with the first end of the next, adjacent lever for the transmission of torque. Adjustably secured within a longitudinal slot of the housing is a spring accessibly for setting the desired torque value of the wrench. This torque value setting assembly acts between the housing and at least one of the levers to apply a force to the lever, which must be overcome in order for the lever to pivot. The pivoting force of the lever is directly proportional to the torque exerted on or Fay the wrench. The torque value setting device is easily adjustable longitudinally on the housing to vary the distance between the pivot point of the lever upon which it acts and the housing. Means for indicating is secured to the housing and engaged to the third lever to prevent over torquing when the torque value set by the torque value setting assembly has been reached. In the preferred embodiment these arrangements constitute a leaf spring pack and a striking pin. The former is arranged in such a way that when the torque value reaches the preset value the spring buckles and prevents over torquing. At this time the striking pin which relates to the spring pack strikes the inner surface of the third lever and makes an audible sound indicating that the preset torque value is reached. Accordingly the present invention an adjustable torque wrench capable of pre-setting specified torque values comprising : an elongated hollow housing having first and second ends; an output drive shaft rotatably supported by said housing adjacent said first end, said output drive shaft having a drive extension protruding from said housing substantially perpendicular to the length of said housing; a plurality of levers pivotally mounted within said housing; a first of said plurality of levers being joumalled to said output drive shaft for rotation therewith, the remaining levers having first and second ends and being pivotally secured to said housing adjacent their first ends at spaced intervals along the longitudinal centering of said housing, and with the exception of the last of said plurality of levers, the second end of each of said remaining levers being engaged with the first end of the next, adjacent lever; torque value setting means extending substantially transversely between said housing and at least one said plurality of levers and having biasing means for developing and applying a force to said at least one lever which said at least one lever must overcome in order to pivot, said torque value setting means being selectively, adjustably mounted relative to said housing to alter the pivoting resistance by varying the position along the length of said at least one lever upon which said biasing means acts; and characterized in that the said torque value setting means comprises a spring pack assembly having a spring pack holder, leaf spring pack and a screw, said spring pack assembly having sliding legs engaged to the last one of said plurality of levers by fixing means, said spring pack holder capable of holding a plurality of said leaf spring pack fixed to a lower mounting plate of the housing; and means for indicating and preventing over torquing when the torque value set by the torque value setting means has been reached. Therefore, the present invention provides an adjustable torque wrench which has an easily adjustable torque value setting device and a means for readily ascertaining when the preset torque value has been reached and means for preventing over torquing. These and other aspects of the invention will become more readily apparent by reference to the following detailed description of a preferred embodiment shown in the accompanying drawings. FIG. 1 is a cross-sectional view showing the torque wrench of the invention in a non-torqued state; FIG. 2 shows the same cross section as FIG. 1 but wherein the wrench has been torqued to its preset value; FIG. 3 shows a cross-sectional view of the mounting of the output drive shaft within the housing of the torque wrench; FIG. 4 shows an enlarged top view of one of the levers shown in FIG"s 1 arid 2; FIG. 5 is a cross-sectional view taken along line X-X in FIG. 4; FIG. 6 shows an enlarged cross-sectional view of the third lever and torque value setting assembly shown in FIG"s 1 and 2; FIG. 7 shows a cross-sectional view of the torque value setting assembly taken along line Y-Y in FIG. 6; and FIG. 8 is a top view of the torque value setting asseably showing its mounting within the torque wrench housing. FIG. 9 illustrates the connection of the spring pack with the spring holder. DESCRIPTION OF THE PREFERRED EMBODIMEHT The torque wrench of the present invention, generally indicated at (1> in FIG"s 1 and 2, comprises an elongated housing (2) which as depicted in FIG. 1, is rectangular in cross-section. Fixedly secured to elongated housing (2) by means of a rivet (3> is a handle adapter (4) having a first end (5) which is rectangular in cross-section and is received within housing (2) and secured thereto by the rivet (3). The other end (6) of h&ndle adapter (4) is circular in cross section and is adapted to receive a handle (7). Handle is releasably secured within handle adapter (4) by means of a removable pin (8) or the like. By removal of pin , handle (7) can be readily withdrawn from handle adapter (4) such that the torque wrench (1) may be stored in a more compact configuration. Housing (2) of torque wrench (1> also includes a longitudinal slot (9) which will be explained more fully below. As shown best in FIG"s 1-3, torque wrench (1) includes an output drive shaft (10) having a drive shaft extension (11). Output drive shaft (10) is a square in cross section and is totatably secured to housing (2) by neans of a clip (12). Drive shaft extension (11) is adapted to receive various size sockets as is known in the art. With reference to FIG"s 1 and 2, located within housing (2) are a plurality of levers (13), (15), (21). First lever (13) has one end journalled to output drive shaft (10) and a second free end (14). Second lever (15) includes first and second ends (16), (17) respectively and is pivotally secured to housing (2) by means of pivot pin (18) located adjacent to first end (16). With reference to FIG"s (4) and (5), fitted into a bore foraed in first end (16) of second lever (15) is a rolling pin (19). The bore in first end (16) does not extend entirely through second lever (15) so that rolling pin (19) is retained within second lever (15) in both the longitudinal and lateral direction of torque wrench (1), as depicted, sinoe second lever (15) extends around greater than 50% of the circumference of rolling pin (19). The bore in first end (16) does not extend entirely through second lever (15) so that rolling pin (19) is retained within second lever (15) into and out of the page as depicted in FIG. 4 by housing (2) and second lever (15). Second end (17) of second lever (15) also includes a rolling pin (20) mounted in a similar fashion. As clearly shown in FIG"s 1 and 2, rolling pin (19) engages second end (14) of first lever (13) while rolling pin (20) engages a third lever (21) as will be more fully explained below. Third lever (21) includes a first end (22) and a second end (23) and is pivotally secured within housing (2) by means of pivot pin (24), The first end (22) of lever (21) includes a ledge portion (25) and a sloped portion (26). Ledge portion (25) is engaged by rolling pin (20) of second lever (15). The first end (22) of third lever (21) is provided with slope portion (26) to ensure no interference between first end (22) and housing (2) when third lever (21) pivots about pivot pin (24). Mounted to third lever (21), adjacent second end (23), is a pin, the function of which will be explained more fully below. It should be noted that each of three levers (13), (16)> (21) are pivotable about axes substantially lying along the longitudinal centerline of housing (2). Due to the interconnections of the first and second ends of the levers, rotation of first lever (13) will be transmitted to first end (16) of second lever (15) through roiling pin (19) causing second lever (15) to pivot, in the clockwise direction as depicted in FIG"S 1 and 2, about pivot pin (18). Pivoting of second lever (15) will cause pivoting of third lever (21) in a counterclockwise direction due to the engagement of roller pin (20) on second end (17) of second lever (15) with ledge portion (25) of third lever (21). When a predetermined torque value has been reached, which is set in a manner which will be more fully explained below, a striking pin (39) engaged to third lever (21) will hit inside surface portion (28) of the third lever (21) thereby making an audible noise which can be used by the operator of the torque wrench (1) as an indication that the desired torque value has been reached. The specific manner in which the desired torque value can be set will now be explained in detail with reference to FIG"s 6 to 8. The torque value setting assembly of the present invention is generally indicated at (27). The leaf spring pack (38) which comprises a number of leaf springs is engaged while torquing to third lever (21) through two sliding legs (42). These sliding legs are connected to the leaf spring pack (38) through two screws (40). A spring holder (37) consisting a striking pin (39) is attached to the lower mounting plate (30). The spring pack (38) is attached to the spring holder (37) through a screw (45). The leaf springs used in the spring pack may be curved or bent. The spring rating can be varied by either increasing the number of springs in the spring pack or by increasing the curvature/bend or by varying spring thickness. The torque is applied on the spring pack (38) in a direction perpendicular to the pack. This torque can be varied by the changing distance between the Pivot pin (24) in the third lever (21) and the position of torque set assembly (27). Once force on spring overcomes the spring rating, the spring pack (38) buckles immediately. The striking pin (39) strikes the inner surface (28) of third lever (21) giving a ringing noise indicating that the set torque is achieved. As soon as the spring pack (38) buckles and strikes the innner surface (28) of third lever (21), the force on the spring pack becomes less and this prevents over torquing. The torque value setting assembly (27) acts between base surface portion (28) of third lever (21) and housing (2). As previously stated, housing (2) includes a slot (33). An upper mounting plate (29) is provided above slot (33) on housing (2) and a lower mounting plate (30) is provided below slot (33) on housing (2). Upper and lower mounting plates (29) and (30) are secured to housing (2) and each other by means of any fasteners (32) known in the art such as screws, rivets, etc. Lower mounting plate (30) includes a slot (31) extending in the longitudinal direction of housing (2). Slots (31), (33) are narrower than a slot (9) on the upper mounting plate (29). Torque value setting assembly (27) includes a slide member (34) adapted to slide within slot (9) of upper mounting plate (29). Slide member (34) is formed with a central bore (35) which receives screw (36). Screw (36) in turn extends through slots (31) & (33). Depending upon the longitudinal distance between torque value setting assembly (27) and pivot pin (24) of third lever (21), the torque which must be exerted in order to pivot levers (13), (15) and (21) is varied. Therefore, after torque wrench (1) is calibrated, which can be narked by the use of a calibration label such as that indicated at (46), the user of torque wrench (1) can simply adjust the position of torque value setting assembly (27) within slots (9), (31) and (33) to thereby adjust the torque required to pivot lever (21) to the point where striking pin (39) will come into engagement with inside surface portion (28) of third lever (21). When this engagement occurs, an audible signal will be produced which can indicate to the user that the desired or preset torque value has been reached. It should be noted that the torque value setting assembly (27) and the audible signalling is arranged to work when torque wrench (1) is used for tightening purposes. Torque wrench (1) is free to operate without the successive pivoting of the levers when used to loosen objects. A dustguard (41) is provided to prevent the internal mechanisms of the toraue wrench from dust. To prevent dust entering through slots (31), (33) a sliding dustguard (41) is sandwiched between spring holder (37) and lower mounting plate (30). Another improvement of the system is the provision of slot (43) on upper mounting plate (29). The spring nay lose a small portion of its rating over a period of time due to usage. The slot (43) helps the usef to reposition the upper mounting plate (29). So this would serve as a useful and quick means for recalibration within specified limits. Once the extreme limits of slot (43) are used the upper mounting plate (29) may be replaced and remarked with the help of a master calibrator. This design would ensure the life of wrench can be extended thereby making it a very cost effective design. Another feature of the invention is the output drive shaft (10) can be redesigned by a suitable means to facilitate ratcheting. This would ensure torquing on one side and free wheeling on the opposite direction. Thus the wrench would be more easy tc the user. With the ratchet design the output shaft (10), will be extended on the opposite side of the extension (11) to facilitate loosening of right hand threads and torquing of left hand threads. Another advantage compared to conventional wrenches using coil springs, in this design the leaf springs are not under stress while not in use. This improves the life and accuracy. Although disclosed with respect to a particular embodiment, it can readily be seen that various changes and/or modifications can be made without departing from the spirit or scope of the .pa present invention. In general, any changes and/or modifications may be made without departing from the spirit or scope of the present invention as defined by the following claims. I CLAIM : 1. An adjustable torque wrench capable of pre-setting specified torque values comprising: an elongated hollow housing (2) having first and second ends; an output drive shaft (10) rotatably supported by said housing adjacent said first end, said output drive shaft (10) having a drive extension (11) protruding from said house a plurality of levers (13, 15, 21) pivotally mounted within said housing (2); a first of said plurality of levers (13) being joumalled to said output drive shaft (10) for rotation therewith, the remaining levers (15, 21) having first and second ends and being pivotally secured to said housing (2) adjacent their first ends at spaced intervals along the longitudinal centerline of said housing, and with the exception of the last of said plurality of levers, the second end of each of said remaining levers being engaged with the first end of the next, adjacent lever; torque value setting means (27) extending substantially transversely between said housing (2) and at least one said plurality of levers and having biasing means for developing and applying a force to said at least one lever which said at least one lever must overcome in order to pivot, said torque value setting means being selectively, adjustably mounted relative to said housing to alter the pivoting resistance by varying the position along the length of said at least one lever upon which said biasing means acts; and characterized in that the said torque value setting means (27) comprises a spring pack assembly having a spring pack holder (37), leaf spring pack (38) and a screw (45), said spring pack assembly having sliding legs (42) engaged to the last one of said plurality of levers by fixing means (36, 34), said spring pack holder (37) capable of holding a plurality of said leaf spring pack (38) fixed to a lower mounting plate (30) of the housing (2); and means for indicating and preventing over torturing when the torque value set by the torque value setting means has been reached. 2. An adjustable torque wrench as claimed in Claim 1, wherein said means for indicating when the set torque value has been reached comprises a striking pin (39) attached to said spring pack holder (37) and is adapted to make a sound by hitting the inside surface portion (28) of the said third lever (21). 3. An adjustable torque wrench as claimed in Claim 1, wherein said housing (2) has a longitudinally extending slot (33) intermediate said first and second ends, said torque value setting means (27) being located within said housing (2) so as to be adjustable within said slot (33). 4. An adjustable torque wrench as claimed in Claim 3, wherein means for releasably securing said torque value setting means (27) is within said slot (33). 5. An adjustable torque wrench as claimed in Claim 4, wherein said torque wrench (1) has at least three levers pivotally mounted within said housing (2). 6. An adjustable torque wrench as claimed in Claim 5, wherein the second lever (15) has roller bearing means (19, 20) at each of said first and second ends (16, 17) which are engaged with the second end (14) of said first lever (13) and the first end (22) of the third lever (21) respectively. 7. An adjustable torque wrench as claimed in Claim 6, wherein said torque value setting means (27) acts between said housing (2) and the third lever (21). 8. An adjustable torque wrench as claimed in Claim 7, wherein each of said levers pivot about axes lying substantially along the longitudinally centerline of said housing (2). 9. An adjustable torque wrench as claimed in Claim 1, wherein a handle (7) having a handle adapter (4) is secured to the second end of said housing (2). 10. An adjustable torque wrench as claimed in Claim 9, wherein a calibration label (46) is attached to said housing (2) above said slot (33). 11. An adjustable torque wrench as claimed in Claim 10, wherein the calibration label (46) is attached to said housing (2) by fixing means (32) with a provision for longitudinal adjustment of the calibration label (46). 12. An adjustable torque wrench substantially as described hereinabove and illustrated with reference to the accompanying drawings.

Full Text

The invention relates to an adjustable torque wrench which is capable of being preset to specific torque values and which includes a means for indicating when the specified torque is reached J and a means to prevent over torturing.
Torque wrenches which can be set to desired torque values are known in the art. Such torque wrenches substantially reduce the time and effort for setting a specific torque when tightening bolts, nuts, spark plugs, etc. In one known type of prior art arrangement, an externally threaded shaft is received within an internally threaded tube for the purpose of setting the torque value. Over time, wear and tear will occur on the threads between the shaft and tube which results in a reduction in the accuracy of the torque setting system.
It is also known in the art of torque wrenches to have a torque release connection between a manually engageable handle and a torque applying member. In these types of wrenches, represented by U.S. Pat.Nos. 2,996,940 and 3,355,970, the torque setting value of the wrench can be adjusted by varying the mechanical advantage of the level-type connection between the wrench handle and the torque applying member. When a preset torque value has been reached, the releasable connection between

the member and the handle prevents further torque application
through the torque-applying member. The release of this
connection provides an abrupt indication that the desired, preset
torque limit has been reached.
Therefore, based on the above discussed prior art. there exists a need for a torque wrench having an adjustable torque setting which requires no recalibration and which will not loose its accuracy over a long period of time. There also exists a need for an adjustable torque wrench which can provide a readily determinable, non-abrupt indication when the preset torque value has been reached.
It is therefore the object of the present invention to provide an adjustable torque wrench having a readily and accurately adjustable torque value setting mechanism in the form of a spring based slide assembly and a means for indicating, preferably audible, when the preset torque value has been reached and a means for preventing over torquing.
The present invention relates to a torque wrench capable of pre-setting specific torque values. The torque wrench comprises an elongated housing which rotatably supports an output drive shaft. The torque on the output drive shaft is transmitted through a plurality of levers which are pivotally mounted within

the housing. One of the levers is corralled to the output drive shaft for rotation therewith and the remaining levers are pivotaliy secured to the housing adjacent first ends thereof along the longitudinal center line of the housing. In the preferred embodiment, three such levers are utilized. The second end of each of the three levers are engaged with the first end of the next, adjacent lever for the transmission of torque.
Adjustably secured within a longitudinal slot of the housing is a spring accessibly for setting the desired torque value of the wrench. This torque value setting assembly acts between the housing and at least one of the levers to apply a force to the lever, which must be overcome in order for the lever to pivot. The pivoting force of the lever is directly proportional to the torque exerted on or Fay the wrench. The torque value setting device is easily adjustable longitudinally on the housing to vary the distance between the pivot point of the lever upon which it acts and the housing.
Means for indicating is secured to the housing and engaged to the third lever to prevent over torquing when the torque value set by the torque value setting assembly has been reached. In the preferred embodiment these arrangements constitute a leaf spring pack and a striking pin. The former is arranged in such a way that when the torque value reaches the preset value

the spring buckles and prevents over torquing. At this time the striking pin which relates to the spring pack strikes the inner surface of the third lever and makes an audible sound indicating that the preset torque value is reached.
Accordingly the present invention an adjustable torque wrench capable of pre-setting specified torque values comprising : an elongated hollow housing having first and second ends; an output drive shaft rotatably supported by said housing adjacent said first end, said output drive shaft having a drive extension protruding from said housing substantially perpendicular to the length of said housing; a plurality of levers pivotally mounted within said housing; a first of said plurality of levers being joumalled to said output drive shaft for rotation therewith, the remaining levers having first and second ends and being pivotally secured to said housing adjacent their first ends at spaced intervals along the longitudinal centering of said housing, and with the exception of the last of said plurality of levers, the second end of each of said remaining levers being engaged with the first end of the next, adjacent lever; torque value setting means extending substantially transversely between said housing and at least one said plurality of levers and having biasing means for developing and applying a force to said at least one lever which said at least one lever must overcome in order to pivot, said torque value setting means being selectively, adjustably mounted relative to said housing to alter the pivoting resistance by varying the position along the length of said at least one lever upon which said biasing means acts; and characterized in that the said torque value setting means comprises a spring pack assembly having a spring pack holder, leaf spring pack and a screw, said spring pack assembly having sliding legs engaged to the last one of said plurality of levers by fixing means, said spring pack holder capable of holding a plurality of said leaf spring pack fixed to a lower mounting plate of the housing; and means for indicating and preventing over torquing when the torque value set by the torque value setting means has been reached.

Therefore, the present invention provides an adjustable torque wrench which has an easily adjustable torque value setting device and a means for readily ascertaining when the preset torque value has been reached and means for preventing over torquing. These and other aspects of the invention will become more readily apparent by reference to the following detailed description of a preferred embodiment shown in the accompanying drawings.
FIG. 1 is a cross-sectional view showing the torque wrench of the invention in a non-torqued state;
FIG. 2 shows the same cross section as FIG. 1 but wherein the wrench has been torqued to its preset value;
FIG. 3 shows a cross-sectional view of the mounting of the output drive shaft within the housing of the torque wrench;
FIG. 4 shows an enlarged top view of one of the levers shown in FIG"s 1 arid 2;
FIG. 5 is a cross-sectional view taken along line X-X in FIG. 4;
FIG. 6 shows an enlarged cross-sectional view of the third lever and torque value setting assembly shown in FIG"s 1 and 2;

FIG. 7 shows a cross-sectional view of the torque value setting assembly taken along line Y-Y in FIG. 6; and
FIG. 8 is a top view of the torque value setting asseably showing its mounting within the torque wrench housing.
FIG. 9 illustrates the connection of the spring pack with the spring holder.
DESCRIPTION OF THE PREFERRED EMBODIMEHT
The torque wrench of the present invention, generally indicated at (1> in FIG"s 1 and 2, comprises an elongated housing (2) which as depicted in FIG. 1, is rectangular in cross-section. Fixedly secured to elongated housing (2) by means of a rivet (3> is a handle adapter (4) having a first end (5) which is rectangular in cross-section and is received within housing (2) and secured thereto by the rivet (3). The other end (6) of h&ndle adapter (4) is circular in cross section and is adapted to receive a handle (7). Handle is releasably secured within handle adapter (4) by means of a removable pin (8) or the like. By removal of pin , handle (7) can be readily withdrawn from handle adapter (4) such that the torque wrench (1) may be stored in a more compact configuration. Housing (2) of torque wrench (1> also includes a longitudinal slot (9) which will be explained more fully below.

As shown best in FIG"s 1-3, torque wrench (1) includes an output drive shaft (10) having a drive shaft extension (11). Output drive shaft (10) is a square in cross section and is totatably secured to housing (2) by neans of a clip (12). Drive shaft extension (11) is adapted to receive various size sockets as is known in the art.
With reference to FIG"s 1 and 2, located within housing (2) are a plurality of levers (13), (15), (21). First lever (13) has one end journalled to output drive shaft (10) and a second free end (14). Second lever (15) includes first and second ends (16), (17) respectively and is pivotally secured to housing (2) by means of pivot pin (18) located adjacent to first end (16). With reference to FIG"s (4) and (5), fitted into a bore foraed in first end (16) of second lever (15) is a rolling pin (19). The bore in first end (16) does not extend entirely through second lever (15) so that rolling pin (19) is retained within second lever (15) in both the longitudinal and lateral direction of torque wrench (1), as depicted, sinoe second lever (15) extends around greater than 50% of the circumference of rolling pin (19). The bore in first end (16) does not extend entirely through second lever (15) so that rolling pin (19) is retained within second lever (15) into and out of the page as depicted in FIG. 4 by housing (2) and second lever (15). Second end (17) of second lever (15) also includes a rolling pin (20) mounted in a similar fashion. As clearly shown in FIG"s 1

and 2, rolling pin (19) engages second end (14) of first lever (13) while rolling pin (20) engages a third lever (21) as will be more fully explained below.
Third lever (21) includes a first end (22) and a second end (23) and is pivotally secured within housing (2) by means of pivot pin (24), The first end (22) of lever (21) includes a ledge portion (25) and a sloped portion (26). Ledge portion (25) is engaged by rolling pin (20) of second lever (15). The first end (22) of third lever (21) is provided with slope portion (26) to ensure no interference between first end (22) and housing (2) when third lever (21) pivots about pivot pin (24). Mounted to third lever (21), adjacent second end (23), is a pin, the function of which will be explained more fully below.
It should be noted that each of three levers (13), (16)> (21) are pivotable about axes substantially lying along the longitudinal centerline of housing (2). Due to the interconnections of the first and second ends of the levers, rotation of first lever (13) will be transmitted to first end (16) of second lever (15) through roiling pin (19) causing second lever (15) to pivot, in the clockwise direction as depicted in FIG"S 1 and 2, about pivot pin (18). Pivoting of second lever (15) will cause pivoting of third lever (21) in a counterclockwise direction due to the engagement of roller pin

(20) on second end (17) of second lever (15) with ledge portion (25) of third lever (21).
When a predetermined torque value has been reached, which is set in a manner which will be more fully explained below, a striking pin (39) engaged to third lever (21) will hit inside surface portion (28) of the third lever (21) thereby making an audible noise which can be used by the operator of the torque wrench (1) as an indication that the desired torque value has been reached.
The specific manner in which the desired torque value can be set will now be explained in detail with reference to FIG"s 6 to 8. The torque value setting assembly of the present invention is
generally indicated at (27).
The leaf spring pack (38) which comprises a number of leaf
springs is engaged while torquing to third lever (21) through
two sliding legs (42). These sliding legs are connected to the
leaf spring pack (38) through two screws (40). A spring holder
(37) consisting a striking pin (39) is attached to the lower
mounting plate (30). The spring pack (38) is attached to the
spring holder (37) through a screw (45).
The leaf springs used in the spring pack may be

curved or bent. The spring rating can be varied by either increasing the number of springs in the spring pack or by increasing the curvature/bend or by varying spring thickness. The torque is applied on the spring pack (38) in a direction perpendicular to the pack. This torque can be varied by the changing distance between the Pivot pin (24) in the third lever (21) and the position of torque set assembly (27).
Once force on spring overcomes the spring rating, the spring pack (38) buckles immediately. The striking pin (39) strikes the inner surface (28) of third lever (21) giving a ringing noise indicating that the set torque is achieved. As soon as the spring pack (38) buckles and strikes the innner surface (28) of third lever (21), the force on the spring pack becomes less and this prevents over torquing.
The torque value setting assembly (27) acts between base surface portion (28) of third lever (21) and housing (2). As previously stated, housing (2) includes a slot (33). An upper mounting plate (29) is provided above slot (33) on housing (2) and a lower mounting plate (30) is provided below slot (33) on housing (2). Upper and lower mounting plates (29) and (30) are secured to housing (2) and each other by means of any fasteners (32) known in the art such as screws, rivets, etc. Lower

mounting plate (30) includes a slot (31) extending in the longitudinal direction of housing (2). Slots (31), (33) are narrower than a slot (9) on the upper mounting plate (29). Torque value setting assembly (27) includes a slide member (34) adapted to slide within slot (9) of upper mounting plate (29). Slide member (34) is formed with a central bore (35) which receives screw (36). Screw (36) in turn extends through slots (31) & (33). Depending upon the longitudinal distance between torque value setting assembly (27) and pivot pin (24) of third lever (21), the torque which must be exerted in order to pivot levers (13), (15) and (21) is varied. Therefore, after torque wrench (1) is calibrated, which can be narked by the use of a calibration label such as that indicated at (46), the user of torque wrench (1) can simply adjust the position of torque value setting assembly (27) within slots (9), (31) and (33) to thereby adjust the torque required to pivot lever (21) to the point where striking pin (39) will come into engagement with inside surface portion (28) of third lever (21). When this engagement occurs, an audible signal will be produced which can indicate to the user that the desired or preset torque value has been reached.
It should be noted that the torque value setting assembly (27) and the audible signalling is arranged to work when torque wrench (1) is used for tightening purposes. Torque wrench (1) is free to operate without the successive pivoting of the levers

when used to loosen objects.
A dustguard (41) is provided to prevent the internal mechanisms of the toraue wrench from dust. To prevent dust entering through slots (31), (33) a sliding dustguard (41) is sandwiched between spring holder (37) and lower mounting plate (30).
Another improvement of the system is the provision of slot (43) on upper mounting plate (29). The spring nay lose a small portion of its rating over a period of time due to usage. The slot (43) helps the usef to reposition the upper mounting plate (29). So this would serve as a useful and quick means for recalibration within specified limits.
Once the extreme limits of slot (43) are used the upper mounting plate (29) may be replaced and remarked with the help of a master calibrator. This design would ensure the life of wrench can be extended thereby making it a very cost effective design.
Another feature of the invention is the output drive shaft (10) can be redesigned by a suitable means to facilitate ratcheting. This would ensure torquing on one side and free wheeling on the opposite direction. Thus the wrench would be more easy tc the user. With the ratchet design the output shaft

(10), will be extended on the opposite side of the extension (11) to facilitate loosening of right hand threads and torquing of left hand threads.
Another advantage compared to conventional wrenches using coil springs, in this design the leaf springs are not under stress while not in use. This improves the life and accuracy.
Although disclosed with respect to a particular embodiment, it can readily be seen that various changes and/or modifications can be made without departing from the spirit or scope of the .pa present invention. In general, any changes and/or modifications may be made without departing from the spirit or scope of the present invention as defined by the following claims.

I CLAIM :
1. An adjustable torque wrench capable of pre-setting specified torque values comprising:
an elongated hollow housing (2) having first and second ends;
an output drive shaft (10) rotatably supported by said housing adjacent said first end, said output drive shaft (10) having a drive extension (11) protruding from said house
a plurality of levers (13, 15, 21) pivotally mounted within said housing
(2);
a first of said plurality of levers (13) being joumalled to said output drive shaft (10) for rotation therewith, the remaining levers (15, 21) having first and second ends and being pivotally secured to said housing (2) adjacent their first ends at spaced intervals along the longitudinal centerline of said housing, and with the exception of the last of said plurality of levers, the second end of each of said remaining levers being engaged with the first end of the next, adjacent lever;
torque value setting means (27) extending substantially transversely between said housing (2) and at least one said plurality of levers and having biasing means for developing and applying a force to said at least one lever which said at least one lever must overcome in order to pivot, said torque value setting means being selectively, adjustably mounted relative to said housing to alter the pivoting resistance by varying the position along the length of said at least one lever upon which said biasing means acts;

and characterized in that the said torque value setting means (27) comprises a spring pack assembly having a spring pack holder (37), leaf spring pack (38) and a screw (45), said spring pack assembly having sliding legs (42) engaged to the last one of said plurality of levers by fixing means (36, 34), said spring pack holder (37) capable of holding a plurality of said leaf spring pack
(38) fixed to a lower mounting plate (30) of the housing (2);
and means for indicating and preventing over torturing when the torque value set by the torque value setting means has been reached.
2. An adjustable torque wrench as claimed in Claim 1, wherein said means for
indicating when the set torque value has been reached comprises a striking pin
(39) attached to said spring pack holder (37) and is adapted to make a sound by
hitting the inside surface portion (28) of the said third lever (21).
3. An adjustable torque wrench as claimed in Claim 1, wherein said housing (2) has a longitudinally extending slot (33) intermediate said first and second ends, said torque value setting means (27) being located within said housing (2) so as to be adjustable within said slot (33).
4. An adjustable torque wrench as claimed in Claim 3, wherein means for releasably securing said torque value setting means (27) is within said slot (33).
5. An adjustable torque wrench as claimed in Claim 4, wherein said torque wrench (1) has at least three levers pivotally mounted within said housing (2).
6. An adjustable torque wrench as claimed in Claim 5, wherein the second
lever (15) has roller bearing means (19, 20) at each of said first and second ends
(16, 17) which are engaged with the second end (14) of said first lever (13) and
the first end (22) of the third lever (21) respectively.

7. An adjustable torque wrench as claimed in Claim 6, wherein said torque
value setting means (27) acts between said housing (2) and the third lever (21).
8. An adjustable torque wrench as claimed in Claim 7, wherein each of said
levers pivot about axes lying substantially along the longitudinally centerline of
said housing (2).
9. An adjustable torque wrench as claimed in Claim 1, wherein a handle (7)
having a handle adapter (4) is secured to the second end of said housing (2).
10. An adjustable torque wrench as claimed in Claim 9, wherein a calibration
label (46) is attached to said housing (2) above said slot (33).
11. An adjustable torque wrench as claimed in Claim 10, wherein the
calibration label (46) is attached to said housing (2) by fixing means (32) with a
provision for longitudinal adjustment of the calibration label (46).
12. An adjustable torque wrench substantially as described hereinabove and
illustrated with reference to the accompanying drawings.

Documents:

0551-mas-1999 abstract-duplicate.pdf

0551-mas-1999 abstract.pdf

0551-mas-1999 claims-duplicate.pdf

0551-mas-1999 claims.pdf

0551-mas-1999 correspondence-others.pdf

0551-mas-1999 correspondence-po.pdf

0551-mas-1999 description (complete)-duplicate.pdf

0551-mas-1999 description (complete).pdf

0551-mas-1999 drawings-duplicate.pdf

0551-mas-1999 form-1.pdf

0551-mas-1999 form-19.pdf

0551-mas-1999 form-26.pdf

0551-mas-1999 form-4.pdf

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Patent Number

216659

Indian Patent Application Number

551/MAS/1999

PG Journal Number

17/2008

Publication Date

25-Apr-2008

Grant Date

17-Mar-2008

Date of Filing

12-May-1999

Name of Patentee

PILLAPALAYAM NARASIMHACHARI MURALIDHARAN

Applicant Address

36-A,4 TH MAIN ROAD, KOTTUR GARDENS, CHENNAI-600 085,

Inventors:

#	Inventor's Name	Inventor's Address
1	PILLAPALAYAM NARASIMHACHARI MURALIDHARAN	36-A,4 TH MAIN ROAD, KOTTUR GARDENS, CHENNAI-600 085,

PCT International Classification Number

B25B 23/14

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA