Abstract:
An improved hydraulic wrench including a one-piece housing in which one end of the housing forms internally a cylinder for hydraulically reciprocating power and the second end of the housing includes an opening in which a torque arm/ratchet mechanism can be pivotally connected by, for example, a square shaft. There is further included a piston shaft which has a fixed piston on the first end and the second end includes an elongated slot which provides a flat wall at 90 degrees of the reciprocating power source. The wall in the elongated slot allows the drive pin which connects the ratchet mechanism to the piston shaft to roll up and down during cycling of the tool, and provides a non-pivoting reciprocating power source as the piston shaft moves backward and forward during operation. There is included a ratchet wheel fixed to a square shaft for rotation therewith, a ratchet pawl on the drive lever and engaging the ratchet wheel to rotate the square shaft upon reciprocation of the piston shaft in the cylinder.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not applicable 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable 
   REFERENCE TO A “MICROFICHE APPENDIX” 
   Not applicable 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to torquing systems. More particularly, the present invention relates to an improved torque hydraulic torque wrench system which includes various improvements for extended life and control of applied torque. 
   2. General Background of the Invention 
   Hydraulic torque wrenches are wrenches which are utilized in numerous industries requiring the tightening down of nuts with a very high torque in the magnitude of as high as 50,000 foot pounds. A particular line of wrenches, known as torque wrenches, have been developed, which are usually hydraulically controlled, and incorporate a ratcheting mechanism where the wrench can be hydraulically operated in order to achieve the high torque, yet operate as a ratcheting wrench in a more confined area. 
   U.S. Pat. No. 5,097,730, entitled “Inline Ratcheting Tool,” incorporated herein by reference, explains the operation of a hydraulic torque wrench. U.S. Pat. No. 4,201,099 issued to Junkers, entitled “Hydraulic Wrench”, incorporated herein by reference, discloses a piston type hydraulic wrench comprising a housing having a first portion and an elongated second portion integral with the first portion and forming a cylinder. Shown is a piston reciprocable in the cylinder, and a shaft having an axis extending transverse to the cylinder and mounted in the first housing portion with an end portion of the shaft projecting outwardly from the housing, and a piston shaft connected at one end to the piston, and at least one drive lever mounted in the region of one end turnable about the axis of the shaft means and connected at the other end of the piston shaft. This connection operates a ratchet wheel during operation. A review of the &#39;099 patent as seen particularly in  FIG. 4 , indicates that during operation the piston shaft must move from its position transverse to the axis of the ratchet member. During such movement, a change occurs in the 90 degree relationship between the rod and the axis of the ratchet adversely impacting the wrench&#39;s torquing power and leading to a shortened wrench life. 
   Various problems exist with prior art wrenches. One problem includes the tendency of the drive pin, connecting the piston shaft to the ratchet member, to wear against the body of the torque wrench requiring replacement/refurbishing of the body portion. 
   Another problem includes the drive pin being deformed during use (by the high forces) required by operating conditions. 
   Another problem includes the drive pin being contacted by a relatively small surface area and increasing irregular localized deformation. 
   Another problem includes excessive variations in the applied torque during piston stroke. 
   BRIEF SUMMARY OF THE INVENTION 
   The apparatus of the present invention solves the shortcomings in the art in a simple and straight forward manner. 
   In one embodiment is provided an improved hydraulic wrench where wear on the body by the drive pin is lowered or minimized. 
   In one embodiment the drive plates resist movement of the drive pin to prevent the pin from wearing or scratching the body. 
   In one embodiment the drive pin and plates are configured to resist movement of the drive pin so that wear on the body is lowered or minimized. 
   In another embodiment is provided an improved hydraulic wrench where distortion of the drive pin is minimized by support from the drive pawl. 
   In another embodiment is provided an improved hydraulic wrench where localized stresses between the piston and drive pin are reduced or minimized by increasing the contact area between the piston and drive pin. 
   In another embodiment is provided an improved hydraulic wrench where variances in the torque during the stroke of the piston are reduced or minimized. 
   While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.” 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
       FIG. 1  is an overall perspective of a preferred embodiment shown in loosening a nut or bolt; 
       FIG. 1A  is a top view of the wrench in  FIG. 1 ; 
       FIG. 2  is an exploded view of the embodiment shown in  FIG. 1 ; 
       FIG. 3  is a sectional view of the embodiment shown in  FIG. 1  with the piston at beginning stroke; 
       FIG. 4  is a sectional view of the embodiment shown in  FIG. 1  with the piston at intermediate stroke; 
       FIG. 5  is a sectional view of the embodiment shown in  FIG. 1  with the piston at full stroke; 
       FIG. 6  is a partial perspective view of the pin, pawl, and drive plates; 
       FIG. 7  is a partial perspective view of the pin, pawl, and a single drive plate; 
       FIG. 8  is a perspective view of a drive plate shown from the top; 
       FIG. 9  is a perspective view of the drive plate of  FIG. 8  shown from the bottom; 
       FIG. 10  is a side view of the drive plate shown in  FIG. 8 ; 
       FIG. 11  is a perspective view of a pawl; 
       FIG. 12  is a top view of the pawl shown in  FIG. 11 ; 
       FIG. 13  is a side view of the pawl shown in  FIG. 11 ; 
       FIG. 14  is a rear view of the pawl shown in  FIG. 11   
       FIG. 15  is a perspective view of a pin; 
       FIG. 16  is a top view of the pin shown in  FIG. 15 ; 
       FIG. 17  is a side view of the pin shown in  FIG. 15 ; 
       FIG. 18  is a rear sectional view of the pin shown in  FIG. 15 , but taken along the lines  18 — 18  of  FIG. 17 ; 
       FIG. 19  is a right side view of the body of the wrench shown in  FIG. 1 ; 
       FIG. 20  is a left side view of the body of the wrench shown in  FIG. 1 ; 
       FIG. 21  is a rear view of the wrench shown in  FIG. 1 ; 
       FIG. 22  is a perspective view of a reaction bar; 
       FIG. 23  is a top view of the reaction bar shown in  FIG. 22 ; 
       FIG. 24  is a side view of the reaction bar shown in  FIG. 22 ; 
       FIG. 25  is a drawing illustrating movement of the drive pin about the center line of the piston; 
       FIG. 26  is a perspective view of a piston; 
     FIGS.  27 A, 27 B, 27 C are respectively perspective, side, and top views of a seal. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Detailed descriptions of one or more preferred embodiments are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in any appropriate system, structure or manner. 
     FIG. 1  is an overall perspective of a preferred embodiment for torque wrench  10  shown loosening a nut or bolt  850 . Hydraulic fluid source  20  is shown powering torque wrench  10 . Controller  22  can be used to control hydraulic fluid source  20 . On/off switch  26  can turn hydraulic power to fluid source  20  on and off. When power is on and toggle switch  23  is not depressed fluid can be pumped in line  28  in the direction of arrow  25  (with fluid returning via line  27  in the direction of arrow  24 ). When toggle switch  23  is depressed fluid flow is switched with fluid flowing into line  27  in the opposite direction of arrow  24  and fluid returning in line  28  in the opposite direction of arrow  25 . Shaft  170  will be turned in the direction of arrow  870  causing socket  15  to turn threaded fastener  850 . In this process a reaction torque will be generated tending to rotate wrench  10  in the opposite direction of arrow  870 . To oppose this reaction torque reaction bar  800  will contact threaded fastener  852 .  FIG. 1A  is a top view of torque wrench  10  tightening threaded fastener  850 . 
     FIG. 2  shows an exploded view of a preferred embodiment for torque wrench  10 . Torque wrench  10  can comprise body  30 , body  30  including a cylinder  500  for hydraulically reciprocating a piston  640 . The piston  640  being operably connected to a driver  160 . The connection between the piston  640  and driver  160  can be a ratcheting mechanism comprising a drive gear  360 . Torque wrench  10  can include a reaction bar  800  which provides a reacting force in opposition to the torque applied by driver  160  on threaded fastener  850 . Driver  160  can be operably connected to a drive shaft  170  which can be a square shaft detachably connectable to a socket  15  (not shown in this Figure) which itself connects to threaded fastener  850 . There can be further included exchangeable sockets mountable on driver  160  for engaging a head of a threaded fastener  850 , such as a bolt or nut. 
   Cylinder  500  can be integrally formed in body  30 . One end of body  30  can include piston stopper  560  which is threadably connected to body  30  to receive hydraulic cylinder  500  parts such as piston  540 , and the other end body  30  has an opening  45  to receive driver  160  parts, such as drive gear  360 . Piston rod  650  includes slot  700  and maintains a perpendicular force in relation to drive shaft  170  during the entire stroke of piston  640 . 
   During operation a reaction torque (or force) equivalent to the torque applied by torque wrench  10  will be generated when removing threaded connector  850 . This reaction torque must be compensated for, such as by having reaction bar  800  transmit such torque to the structure which threaded connected  850  is located. When drive shaft  170  is first operably connected to threaded connector  850  (such as through a socket head), reaction bar  800  may not be in contact with the structure. Torque wrench  10  should be rotated until reaction bar  800  contacts the structure. Otherwise body  30  of torque wrench  10  will rotate until contacting the structure possibly causing injury if hands or fingers are caught in between the structure and body  30 . During the application of force to turn threaded connector  850  in a first direction, a reaction force will be generated in a second direction tending to turn body  30  in the opposite direction in which threaded connector  850  is being turned. Reaction bar  800  can be used to contact the adjacent structure and provide a reacting force so that a user is not required to manually apply the reacting force which can be as high as 50,000 foot pounds. 
   As shown in  FIGS. 3 and 26  piston  640  can comprise a rod  650  having a tip  660  with the tip  660  having an elongated slot  700 . On the end opposing tip  660  can be connected base  670 . 
   Body  30  can include base section  50 , interior  40 , cylinder  500 , and front section  70 . Base section  50  can include hexagonal section  60  for incorporating reaction bar  800 . Front section  70  can operate drive  160 . Front section  70  can include first and second plates  70 , 80  which respectively can include first and second bores  100 , 110 . Hydraulic ports  520 , 530  can be used for introducing hydraulic fluid into cylinder  500  during operation. 
   Driver  160  can comprise drive shaft  170 , drive gear  360 , first and second drive plates  180 , 190 , and drive pawl  240 . Drive gear  360  can be rotatably connected to first and second drive plates  180 , 190 . Drive pawl  240  can be operably connected to drive gear  360  through a plurality of teeth  365  located on drive gear  360 . Tip  250  of drive pawl can ratchet with respect to the plurality of teeth  365 . 
   Cylinder  500  can comprise cylinder chamber  510 , rear wall  540 , front wall  550 , piston stopper  560 , and end cap  570 . A reciprocating piston  640  can included in cylinder chamber  510  and can move in the direction of arrows  860 , 870  depending on the direction of fluid flow in cylinder chamber  510  from hydraulic ports  520 , 530 . 
   Reciprocating piston  640  can comprise piston rod  650 , tip  660 , and base  670 . Tip  660  can comprise slot  700  for operably connecting piston  640  to driver  160 . Base  670  can include groove  720  for installing a seal  730  which seals base  670  to the walls of cylinder chamber  510  during operation. 
   Reciprocating piston  640  can be operably connected to driver  160  though a connection between drive pawl  240  and tip  660 . Pin  440  can extend through bores  280 , 290  in first and second plates  260 , 270  for drive pawl  240 . Tip  660  can connect to pin  440  through slot  700 . 
   Piston rod  640  can be attached to piston rod tip  660  which is operably connected to drive pin  440  through slot  700 . Drive pin  440  is operably connected to drive pawl  240  and first and second drive plates  340 , 350 . First and second drive plates  340 , 350  are pivotally connected to drive pin  440  through bores  280 , 290  ( FIG. 2 ). Drive pawl  240  is operatively connected to drive gear  360  by a plurality of angular gear teeth  365  and drive pawl spring  242 . Drive plate extension  342  biases spring  242  against drive pawl  240  and drive pawl  240  against plurality of angular teeth  365 . Drive gear  360  is connected to drive shaft  170  through opening  367 . Drive gear  360  is rotatably connected to wrench body  30  through bores  100 , 110 . Extension of piston rod  640  rotates first and second drive plates  340 , 350 ; thereby moving drive pin  440  and rotating drive pawl  240  engaging drive gear  360 , and turning drive shaft  170 , and finally engaging nut or bolt  850 . Drive bushings  950 , 960  can be operatively connected to drive gear  360 . Drive bushings  950 ,  960  can fit into  100 , 110  of wrench body  30  and can reduce friction and act as a bearing surface during rotation of drive shaft  170 . During retraction of piston rod  640  inside hydraulic cylinder  500 , piston rod  640  pulls drive pin  440 , and drive plates  340 , 350  which, in turn pulls drive pawl  240 . However, during retraction, drive pawl  240  ratchets over drive gear  340  without moving such gear. 
   Reaction bar  800  can be connected to wrench body  30  and will be in contact with a structural component and provide a reaction force to compensate for the torque generated by the torque wrench  10 . As shown in  FIGS. 22 through 24 , reaction bar  800  can comprise arm  810 , base  820 , a plurality of splines  825 , and opening  830 . Plurality of splines  825  can be fitted on for engaging hexagonal section  60  of torque wrench  10 . There can be included a set screw hole for fixing base  820  onto hexagonal section  60 . 
     FIGS. 3 through 5  schematically illustrate stroking of torque wrench  10 .  FIG. 3  is a sectional view of torque wrench  10  with piston  640  at beginning stroke.  FIG. 4  is a sectional view torque wrench  10  with piston  640  at intermediate stroke.  FIG. 5  is a sectional view of torque wrench  10  with piston  640  at full stroke. Movement of piston  640  is controlled by the flow of hydraulic fluid through ports  520 , 530 .  FIG. 4  shows piston  640  moving in the direction of arrows  890 , 900 . For movement in this direction hydraulic fluid enters cylinder through port  520 . This hydraulic fluid pushes against first area  680  of piston base  670 . A pushing force is created which is equal to the pressure of the hydraulic fluid from port  520  multiplied by the size first area  680 . Such force cause piston  640  to move in the direction of arrow  880 . At the same time hydraulic fluid inside of cylinder chamber  510 , but on the side of second area  690  will exit through port  530 . As piston moves in the direction of arrow  900  pin  400  and drive pawl  250  operably engage the plurality of angular teeth  365  causing drive gear  360  to rotate in the direction of arrow  870 . As additional hydraulic fluid is pumped through port  520  piston  640  will continue to move in the direction of arrows  880 , 900  until second face  690  contacts front wall  550  (or piston stopper  560 ). At this point drive gear  360  has seen the maximum rotation in the direction of arrow  870  for this piston stroke. Now piston  690  can be returned to its beginning stroke position. 
   To return piston  690  to the beginning stroke position hydraulic fluid is pumped into port  530  and pushes against second area  690  of piston base  670 . A pushing force is created which is equal to the pressure of the hydraulic fluid from port  520  multiplied by the size second area  690 . Such force will cause piston  640  to move in the direction of arrow  890 . At the same time hydraulic fluid inside of cylinder chamber  510 , but on the side of first area  680  will exit through port  520 . As piston moves in the direction of arrow  890 , drive pawl  250  will slip over the plurality of angular teeth  365  by rotating in the direction of arrow  920 . Drive gear  360  will be prevented from rotating in a direction opposite arrow  870  by arm  820  operably engaging plurality of angular teeth  365 . As additional hydraulic fluid is pumped through port  530  piston  640  will continue to move in the direction of arrows  890  until first face  680  comes to the initial stroke position. At this point piston  690  is ready for a second stroke. 
   The above movement can be described as a ratcheting movement. To reverse rotation of drive shaft  170 , torque wrench  10  must be removed from nut or bolt  850 , body  30  turned over and again fastened to nut or bolt  850 . Drive shaft  170  is slidably connected to drive gear  360  to allow shaft  170  to protrude from the side of body  30  on which nut or bolt  850  is to be tightened or loosened. One side of body  30  drive shaft  170  will rotate clockwise and the other side of body  30  will rotate counterclockwise. 
   Fluid flows enters the rear of cylinder chamber  510  (through hydraulic port  520 ) causing piston  640 , piston rod  650 , and tip  660  to extend. Piston  640  is driven forward by the fluid pressure, and piston rod tip  660  engages driver  160  to impart high-torque rotation to threaded fastener  850 . Fluid exits cylinder chamber  510  through hydraulic port  530  returning to hydraulic fluid source  20 . Once piston  640  extends fully forward, the fluid flow is manually switched. Fluid now enters cylinder chamber  510  through hydraulic port  530  and exits through port  520  moving piston  640  toward rear wall  540 . The fluid between piston  640  and rear wall  54  is forced out through port  520  and returning to fluid source  20 . Once piston  640  retracts fully inward, fluid flow is again manually switched back to the flow directions for forward movement. This process is repeated until threaded fastener  850  has been completely tightened to the required high torque, and torque wrench  10  can be applied to another threaded fastener. 
   Should one wish to loosen a torqued threaded fastener, such as nut or bolt  850 , torque wrench  10  is simply “flipped over” and the opposite end of drive shaft  170  is operably connected to threaded fastener  850 . Flipping over wrench  10  will cause drive shaft  170  to rotate in a counter-clockwise direction thereby loosening threaded fastener  850 . As described above hydraulic fluid is manually controlled to extend and retract piston  640 . Retraction of piston  640  as described above is accomplished by manually switching the direction of fluid flow into and out of hydraulic ports  520 , 530  from hydraulic fluid source  20 . Also as described above the direction of fluid flow into and out of hydraulic ports  520 , 530  from hydraulic fluid source  20  is manually switched to cause piston  640  to extend. 
   The wrench can also include a neutral release lever wherein a neutral position the wrench would free wheel with the lever release disengaged drive pawl of the drive mechanism and the lever release is positioned between the drive mechanism and the reciprocating power source. The neutral release lever may be fixed or attachable. The lever extends to a position in which on total reaction, the drive pawl is disengaged. 
     FIG. 25  graphically illustrates the changes in torque during a full stroke of piston  640 . During each stroke piston  640  travels along a straight line which is indicated by center line  732  through the longitudinal center of piston  640 . However, drive pin  440  moves through an arc  910 , which arc forms part of a circle having a radius equal to the distance between center of drive gear  360  (and also center of bore  370  of first drive plate  340 ) and the center  485  of drive pin  440  (and also the center of recessed are  345  of first drive plate  340 ). That is, first drive plate  340  controls the radial position of drive pin  440  as pin  440  moves about drive gear  360 . Dimensional line  930  graphically represents the vertical distance between the center  485  of drive pin  440  and the center  366  of drive gear  360 . The torque applied to drive gear  360  at any given instant is equal to the hydraulic force applied on piston  640  multiplied times the vertical distance  930 . The hydraulic force applied to piston  640  can remain constant during strokes of piston  640 . However, because torque equals force times length, the torque applied to drive gear  360  will vary according to the variance of the vertical distance  930 . In embodiment, piston  640  is positioned where its centerline  732  falls in the middle  990  of the vertical movement of drive pin  440 . When located in middle  990  the deviation in torque applied to drive gear  360  during a given stroke of piston  640  will be minimized because the deviation in vertical distance  930  will be minimized. Prior art torque wrenches line up center line  732  of piston  640  with position  940 . In these prior art wrenches the deviation in vertical distance  930  will be equal to vertical travel  980 . With the instant embodiment the deviation in vertical distance  930  will be one half of vertical travel  980  as distance  960  will be equal to distance  970 . Such a construction will minimize variances in torque during any given stroke. Another method of minimizing deviations of torque is to vary hydraulic pressure on piston  640  in relation to the vertical distance  930 . That is, as vertical distance  930  increases during a stroke, hydraulic pressure can be reduced to maintain a constant torque. Further, when vertical distance  930  decreases during a stroke, hydraulic pressure can be increased to maintain a constant torque. The change in pressure can be calculated based on the change in vertical distance  930 . However, with this embodiment the position of piston  640  (or angular position of drive plate  340 ) would probably have to be known to calculate the change in vertical distance  930 . 
   The other problem addressed by centering centerline  732  in the middle of arc  910  is reducing any reverse torque on piston  640 . Whenever center  445  of drive pin  440  moves away from centerline  732  of piston  640  a reverse torque will be applied to piston  640  equal to the vertical distance  1000  multiplied by the hydraulic force on piston  640 . This reverse torque tends to rotate piston  640  in relation to cylinder  500  and this tendency to rotate can cause premature seal failure along with wear between piston  640  and cylinder  500 . Placing centerline  732  of piston  640  in the middle of arc  910  will minimize vertical distance  1000  and therefore minimize the amount of reverse torque for any given hydraulic force. The delta in  FIG. 3  schematically illustrates the vertical distance  1000 . Arrow  1010  shows the reverse torque being applied to piston  640 . In other embodiments centerline  732  is placed between about 0 and 50 percent from the centerline to maximum vertical movement of drive pin  440 ; more preferably between about 0 and 35 percent; more preferably between about 0 and 25 percent; and most preferably between about 0 and 10 percent. 
   In one embodiment hydraulic cylinder  500  can include spaced apart wear rings  620 ,  630  respectively located in grooves  600 , 610 . Wear rings  620 , 630  can be used to prevent wear between piston  640  and hydraulic cylinder  500 , such as the walls of chamber  510 . During the stroke piston  640  can contact wear rings  620 , 630  and not the walls of chamber  510 . Accordingly, the walls of chamber  510  will not scratch or scar the surface of piston  640 . Additionally, piston  640  will not scratch or scar the walls of chamber  510 . Spacing apart wear rings  620 , 630  also helps the rings absorb the reverse torque discussed above. The reverse torque discussed above can be absorbed by seal  730  (and piston base  670 ), along with wear rings  620 , 630 . 
   It has been found that a v-cut shape for seal  730  provides a longer seal life. Seal  590  for end cap  560  can also be a v-cut. 
     FIGS. 11 through 14  show a preferred drive pawl  240 . Drive pawl  240  can include support area  300 .  FIG. 11  is a perspective view of drive pawl  240 .  FIG. 12  is a top view of drive pawl  240 .  FIG. 13  is a side view of drive pawl  240 .  FIG. 14  is a rear view of drive pawl  240 .  FIG. 7  is a perspective view showing drive pin  440  mounted in drive pawl  240  and also mounted in second drive plate  350 . One of the problems with prior art torque wrenches is bending or failure of drive pin  440 . Typically, drive pin  440  is supported by first and second plates  260 , 270 . However, with large forces drive pin  440  can deflect/bend between plates  260 , 270  causing fatigue and other problems. In one embodiment drive pawl  240  can include support area  300 . Support area  300  can provide intermediate support (between plates  260 , 270 ) to drive pin  440  and resist bending of drive pin  440 . Support area  300  can extend from plate  260  to plate  270 . In an alternative embodiment support area does extend from plate  260  to plate  270 . In another alternative embodiment support area  300  comprises a support post. In another embodiment support area  300  substantially follows the curvature of drive pin  440 . 
   It has been found that in prior art wrenches the sides of the drive pin touch the interior of the wrench body during motion. This can cause wear, scratching, gouging, and premature failure of bodies along with drive pins. During torque wrench operation drive pins can shift to one side until contacting the interior of the wrench bodies. Because of the large forces placed on drive pins during operation the drive pins will tend to flex and their sides extending outward even further. As the drive pins are moved through an arc around the drive gears, the side of the drive pin contacting the interior of the drive body can wear, gouge, scratch, scar, or otherwise impair the interior of the drive body. This mechanism can continue (as the drive pin can move over even more where a groove appears in the wall of the body) until the drive body needs repair or replacement. In one embodiment first and second ends  460 , 470  of drive pin  440  are restricted from touching the interior  40  of body  30 . In one embodiment first and second plates  340 , 350  can respectively include recessed areas  345 , 355 , instead of bores therethrough. Recessed areas  345 , 355  will prevent either first or second end  460 , 470  from contacting interior  40  of body  30  and wearing interior  40  of body  30 . In another embodiment first and second ends  460 , 470  of drive pin  440  have their movement restricted past first and second drive plates  340 , 350 . Instead of recessed areas  345 , 355 , bars/restrictors can be placed in bores which replaced recessed areas  345 , 355 . In another embodiment, a wear plate can be placed on interior  40  of body  30 —which wear plate tracks the movement of drive pin  440 . In another embodiment interior  40  of body  30  can be coated with a material to resist wear from first and second ends  460 , 470  of drive pin  440 . In another embodiment the hardness of interior  40  of body  30  can be made harder than the hardness of drive pin  440 . Because drive pin  440  is softer in this embodiment, drive pin  440  will wear instead of interior  40  of body  30 . 
   In another embodiment drive pin  440  and drive plates  340 , 350  can be configured to resist side to side movement of drive pin  440 . This can be accomplished by a variety of means, such as by beveling first and second ends  460 , 470  of drive pin  440  to mate with openings in first and second drive plates  340 , 350 . In another embodiment the center  445  of drive pin  440  can have a larger cross section than the first and second ends  460 , 470 . The larger drive pin  440  cross section in the center  445  would resist movement of drive pin  440  from side to side beyond first and second drive plates  340 , 350  and resist contact by drive pin  440  with body  30 . In another embodiment a restriction can be placed on drive pin  440  to restrict side to side movement of drive pin  440  past drive plates  340 , 350 . Such a restriction could include a projection from drive pin  440  on either or both sides of drive pin  440 . The projections can include one or more annular rings, set screws, rods, spikes, arms, or other projections. In another embodiment drive plates  340 , 350  can be mechanically linked with drive pin  440  to prevent side to side or lateral movement of drive pin  440 . Such mechanical linkage can include set screws, snap rings, or other linkages. For example, snap rings can be placed on either side of drive pin  440 , but on the inside of drive plates  340 , 350  and these snap rings would resist side to side movement of drive pin  440 . As another example, set screws could be used between drive plates  340 , 350  and first and second ends  460 , 470  of drive pin  440  mechanically connecting the plates to the drive pin. However, this use of set screws is not preferred because it would resist relative rotation of drive pin  440  and drive plates  340 , 350 . In another embodiment drive pin  440  can be fastened to drive plates  340 , 350  by welding or an adhesive. 
   Recessed area of pin  440  can be used to reduce localized contact stresses in drive pin  440 . Prior art wrenches include pins of uniform circular cross sections. In prior art wrenches it has been found that piston rod tips contact drive pins in only small localized areas and generate high localized areas of stress and deformation. In a preferred embodiment of wrench  10 , drive pin  440  includes recessed area  480  which is flat and increases the area of contact to reduce/minimize localized areas of high stress. Edges  482 , 484  are shown at 90 degrees relative to flat area  480 . However, to reduce stress concentration, edges  482 , 483  can be at 45 degrees or lower or can even be curved, such as parabolic or elliptical curves. 
   
     
       
             
           
             
             
           
             
             
           
         
             
                 
             
             
               LIST OF REFERENCE NUMERALS: 
             
             
               The following is a list of reference numerals used in this application: 
             
           
        
         
             
               Reference No. 
               Description 
             
             
                 
             
           
        
         
             
               10 
               Torque Wrench 
             
             
               15 
               Socket 
             
             
               20 
               Hydraulic Fluid Source 
             
             
               22 
               Controller 
             
             
               23 
               Switch 
             
             
               24 
               Arrow 
             
             
               25 
               Arrow 
             
             
               26 
               Switch 
             
             
               27 
               Line 
             
             
               28 
               Line 
             
             
               30 
               Body 
             
             
               40 
               Interior of Body 
             
             
               45 
               Opening 
             
             
               50 
               Base 
             
             
               60 
               Hexagon Section 
             
             
               70 
               Front Section 
             
             
               80 
               First Plate 
             
             
               90 
               Second Plate 
             
             
               100 
               Bore in First Plate 
             
             
               110 
               Bore in Second Plate 
             
             
               130 
               Threaded Section 
             
             
               140 
               End Cap 
             
             
               150 
               Threads 
             
             
               160 
               Driver 
             
             
               170 
               Drive Shaft 
             
             
               180 
               First Drive Plate 
             
             
               190 
               Second Drive Plate 
             
             
               200 
               Bore In First Drive Plate For Piston Rod Tip 
             
             
               210 
               Bore In Second Drive Plate For Piston Rod Tip 
             
             
               220 
               Cover for bore 
             
             
               230 
               Cover for bore 
             
             
               240 
               Drive Pawl 
             
             
               242 
               Spring 
             
             
               250 
               Tip for Drive Pawl 
             
             
               260 
               First Plate for Drive Pawl 
             
             
               270 
               Second Plate for Drive Pawl 
             
             
               280 
               Bore In First Drive Plate For Drive Pawl 
             
             
               290 
               Bore In Second Drive Plate For Drive Pawl 
             
             
               300 
               Support Area for Drive Pawl 
             
             
               310 
               Recessed Area for Drive Pawl Spring 
             
             
               320 
               Drive Pawl Spring 
             
             
               330 
               Drive Plate Spacer 
             
             
               340 
               First Drive Plate 
             
             
               342 
               Catch for Spring 
             
             
               345 
               Recessed Area of first drive plate 
             
             
               350 
               Second Drive Plate 
             
             
               355 
               Recessed Area of second drive plate 
             
             
               360 
               Drive Gear 
             
             
               365 
               Plurality of Angular teeth 
             
             
               366 
               Center of Drive Gear 
             
             
               367 
               Opening 
             
             
               370 
               Bore In First Drive Plate For Drive Gear 
             
             
               380 
               Bore In Second Drive Plate For Drive Gear 
             
             
               390 
               Bore In Drive Gear For Drive Pin 
             
             
               410 
               Drive Bushings 
             
             
               420 
               Bores In Drive Bushings For Drive Pin 
             
             
               430 
               Drive Bearings 
             
             
               440 
               Drive Pin 
             
             
               445 
               Center 
             
             
               450 
               Cylindrical Section 
             
             
               460 
               First End of Drive Pin 
             
             
               470 
               Second End of Drive Pin 
             
             
               480 
               Flat Area of Drive Pin 
             
             
               482 
               Edge 
             
             
               484 
               Edge 
             
             
               485 
               Center of Drive Pin 
             
             
               490 
               Bore In Wrench Body 
             
             
               500 
               Hydraulic Cylinder 
             
             
               510 
               Cylinder Chamber 
             
             
               520 
               hydraulic port 
             
             
               530 
               hydraulic port 
             
             
               540 
               Rear Wall Of Cylinder Chamber 
             
             
               550 
               Front Wall of Cylinder Chamber 
             
             
               560 
               Piston Stopper 
             
             
               570 
               End Cap to cylinder chamber 
             
             
               580 
               seal groove 
             
             
               590 
               seal 
             
             
               600 
               Wear Ring Groove 
             
             
               610 
               Wear Ring Goove 
             
             
               620 
               Wear Ring 
             
             
               630 
               Wear Ring 
             
             
               640 
               Piston 
             
             
               650 
               Piston Rod 
             
             
               660 
               Piston Rod Tip 
             
             
               670 
               Piston Rod Base 
             
             
               675 
               Bolt 
             
             
               680 
               First Area for Base 
             
             
               690 
               Second Area for Base 
             
             
               700 
               Slot in Tip 
             
             
               710 
               Flattened Area of Slot 
             
             
               720 
               Seal groove 
             
             
               725 
               Lower edge 
             
             
               726 
               Outer edge 
             
             
               727 
               Upper edge 
             
             
               728 
               Top 
             
             
               729 
               Interior 
             
             
               730 
               Seal 
             
             
               732 
               Center Line for Piston Rod 
             
             
               735 
               Stroke 
             
             
               740 
               Anti-reverse mechanism 
             
             
               750 
               Lever for anti-reverse mechanism 
             
             
               760 
               Shaft 
             
             
               770 
               Lock for anti-reverse mechanism 
             
             
               780 
               Spring 
             
             
               790 
               Bearing 
             
             
               800 
               Reaction Bar 
             
             
               810 
               Arm 
             
             
               812 
               Boot for arm 
             
             
               820 
               Base 
             
             
               825 
               Spline 
             
             
               830 
               Opening 
             
             
               840 
               Prong 
             
             
               850 
               Threaded Fastener such as nut or bolt 
             
             
               852 
               Threaded Fastener such as nut or bolt 
             
             
               860 
               Arrow 
             
             
               870 
               Arrow 
             
             
               880 
               Arrow 
             
             
               890 
               Arrow 
             
             
               900 
               Arrow 
             
             
               910 
               Arc for Center Line of Drive Pin 
             
             
               920 
               Distance from Center of Drive Gear to Center of Drive 
             
             
                 
               Pin 
             
             
               922 
               Arrow 
             
             
               930 
               Vertical Distance from Center of Drive Gear to Center of 
             
             
                 
               Drive Pin 
             
             
               940 
               Position at Beginning of Stroke 
             
             
               950 
               Position at End of Stroke 
             
             
               960 
               Distance from Center of Piston to Center of Drive Pin 
             
             
               970 
               Distance from Center of Piston to Center of Drive Pin 
             
             
               980 
               Maximum Vertical Travel of Drive Pin 
             
             
               990 
               Middle 
             
             
               1000 
               Vertical distance 
             
             
               1010 
               Arrow 
             
             
                 
             
           
        
       
     
   
   Below are listed the preferred materials for various items of wrench  10 . Body  30 , reaction bar  800 , piston rod base  670 , piston stopper  560 , and lever  750  can be comprised of aluminum 7075 T6. Drive pawl  240  can be comprised of 4340 carbon steel having a rockwell hardness of between 42–44. Drive gear  360  can be comprised of 4340 carbon steel having a rockwell hardness of between 42–44. Drive pin  440  can be comprised of 4340 carbon steel having a rockwell hardness of between 50–52. Piston rod  640  can be comprised of 4340 carbon steel having a rockwell hardness of between 55–57. Drive shaft  170  can be comprised of 4340 carbon steel having a rockwell hardness of between 50–52. Drive plates  260 , 270  can be comprised of AR400 steel having a rockwell hardness of between 44–45. Reaction boot  812  can be comprised of 4140 stainless steel having a rockwell hardness of between 42–44. 
   Seals  590 ,  730  can be Neoprene having a hardness of V90. Wear rings  620 , 630  can be molygard. 
   All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
   It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims. 
   The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.