Abstract:
A compact hydraulic torque wrench which has an efficient design enabling it to be relatively small in size. The arrangement of the return spring for the hydraulic cylinder provides increased strength and reduces the size of the unit. The device is constructed to enable the drive arm to go through the entire travel without change in alignment. Additionally, the device includes a braking system for the reaction arm to ensure that a ratcheting effect occurs and that the proper return of the hydraulic piston can be accomplished by means of a return spring without the necessity for a hydraulic return of the piston.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims the benefit of application Ser. No. 10/175,524 filed Jun. 19, 2002, now abandoned, which in turn is based upon and claims the benefit of provisional application No. 60/299,534 filed Jun. 20, 2001, incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present application pertains to power tools and particularly to hydraulic torque wrenches.  
       BACKGROUND OF THE INVENTION  
       [0003]     Hydraulic torque wrenches are often large and awkward to use. They are difficult to reach into small places, they are heavy, and they are relatively complex devices.  
         [0004]     Additionally, the device often will hang up, and will not operate because of misalignment of the piston due to changes in the angle of the drive arm as the wrench goes through the cycle of travel.  
       OBJECTS AND SUMMARY OF THE INVENTION  
       [0005]     The present invention sets forth a compact hydraulic torque wrench which has an efficient design enabling it to be relatively small in size. The arrangement of the return spring for the hydraulic cylinder provides increased strength which reduces the size of the unit. The device is constructed in such a way to enable the drive arm go through its entire travel without change in alignment.  
         [0006]     Additionally, the device includes a braking system for the reaction arm to ensure that a ratcheting effect occurs and that the proper return of the hydraulic piston can be accomplished by means of a return spring without the necessity for a hydraulic return of the piston.  
         [0007]     Accordingly, it is an object of the present invention to provide a compact hydraulic torque wrench in which the return spring is disposed within the piston to reduce the length and diameter required for the piston assembly.  
         [0008]     It is another object of the present invention to provide a compact hydraulic torque wrench in which the return spring can be heavier than normal return springs because of its disposition within the piston rather than encircling the piston.  
         [0009]     It is another object of the present invention to provide a compact hydraulic torque wrench which does not produce any side loads on the piston during the normal travel of the piston.  
         [0010]     It is another object of the present invention to provide a compact hydraulic torque wrench in which the piston is guided throughout its entire length of travel.  
         [0011]     It is another object of the present invention to provide a compact hydraulic torque wrench in which the pitch angle of the drive arm never changes as the arm moves along its entire path of travel.  
         [0012]     It is another object of the present invention to provide a compact hydraulic torque wrench which can have access to the hydraulic cylinder from either the top or the front.  
         [0013]     Another object of the present invention to provide a compact hydraulic torque wrench which has provisions for a reaction arm to fit within the housing to provide a wide flexibility of operation for the wrench.  
         [0014]     It is still another object of the present invention is to provide a compact hydraulic torque wrench which has a brake system from which is enabled the braking of the hydraulic arm to overcome the ratchet action in the drive arm.  
         [0015]     Other objects of the present invention are to provide a compact hydraulic torque wrench is relatively small in size, relatively light, which has relatively few moving parts, which is relatively simple to manufacture, which is relatively durable, which is relatively inexpensive to produce and which is relatively flexible and easy to use. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]     For a more complete understanding of the present invention reference may be had to the following drawing taken in connection with the description of the preferred embodiments, of which:  
         [0017]      FIG. 1  is a side view drawing of a compact torque wrench of the current invention.  
         [0018]      FIG. 2  is a rear view drawing of the torque wrench shown in  FIG. 1 .  
         [0019]      FIG. 3  is a top view drawing of the torque wrench shown in  FIG. 1  showing the housing only.  
         [0020]      FIG. 4  is an exploded view of the components of a compact torque wrench built in accordance with the teachings of the current invention but of slightly different embodiment with respect to the mounting of the closure plate on the back of the housing.  
         [0021]      FIG. 5  is a perspective view of the housing from the rear showing the arms of the housing and the holes for the output drive.  
         [0022]      FIG. 6  is a rear perspective view of the housing showing the cylinder and the step in the cylinder for coaction with the piston to limit the travel of the piston.  
         [0023]      FIG. 7  is a view showing the components of the piston and return spring, the drive arm and the output drive and the braking mechanism for the output drive mounted to the housing.  
         [0024]      FIG. 8  is a perspective view showing the piston, the piston arms, the spring guide cylinder within the piston, and the seal at the front of the piston.  
         [0025]      FIG. 9  is a view of the piston showing the return spring in the spring guide cylinder of the piston and showing the drive arm mounted within the arms of the piston, with the output drive mounted in the drive arm.  
         [0026]      FIG. 10  is a perspective view of the drive arm showing the elongated slots for mounting to the piston and showing the output drive ratchet in place and also showing the passage in the drive arm for a set screw in the output ratchet gear socket.  
         [0027]      FIG. 11  shows an access hole at the bottom of the output arm which is used to gain access to the set screw mounted in the output ratchet gear so that a wrench rod can be placed into the socket to make a positive wrench as well as a socket.  
         [0028]      FIG. 12  shows the orientation of the brake assembly with the output drive gear.  
         [0029]      FIG. 13  is a perspective view from the lower rear of the hydraulic torque wrench of the present invention with the drive arm positioned on the right.  
         [0030]      FIG. 14  is an assembly view showing the components of a further embodiment of the hydraulic torque wrench of the invention.  
         [0031]      FIG. 15A  is a front view of the drive arm or drive place shown in  FIG. 14 .  
         [0032]      FIG. 15B  is a right elevational view of the drive arm or drive plate shown in  FIG. 15A .  
         [0033]      FIG. 16A  is a front view of the piston shown in  FIG. 14 .  
         [0034]      FIG. 16B  is a view of the piston shown in  FIG. 14  from the left side.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [heading-0035]     Glossary of Terms  
         [none]    
       
          a)  100  hydraulic torque wrench general  
          b)  110  housing 
        i)  115  front end 
             120  side arms      130  aperture for the output drive      140  lip for mounting the clutch system      150  aperture for reaction arm      160  keyway for mounting back wall of housing      162  threaded passages in side arms as alternative      164  stress securing back wall to housing    
            ii)  170  cylinder 
             180  cylindrical wall      190  forward end      200  shoulder      210  ramp at end of piston    
            iii) Inlets 
             220  front inlet      230  top inlet      240  hydraulic connection    
            iv)  250  back wall of housing 
             262  closure or pressure plate for back wall of housing      265  recess which forms a seat for return spring  340     
           
     
          c)  260  piston 
        i)  270  shaft 
             280  front end or top surface      290  seal      300  spring guide bore within the piston    
            ii)  310  arms     iii)  320  apertures for piston pins 
             210  piston    
            iv)  330  piston pins    
     
          d)  340  return spring  
          e)  350  output plate 
        i)  360  arms of output plate 
             362  elongated slots    
            ii)  370  circular opening for output drive gear     iii)  380  opening for pawl     iv)  390  access opening for set screw in output drive    
     
          f)  400  output drive 
        i)  410  ratchet gear     ii)  420  pawl in output arm     iii)  430  threaded passages for cover screws     iv)  440  cover for ratchet gear 
             450  brake assembly for ratchet gear      452   0  ring in cover for ratchet      454  screw in cover for squeezing O ring against lip  140     
            v)  460  set screw to hold output socket or output wrench     vi)  470  output socket     vii)  480  output wrench (alternate)    
     
          g)  490  reaction arm  
          h)  500  foot for reaction arm  
       
     
         [0087]     With reference to the drawings, we can see that the torque wrench has a housing with side arms and passages for mounting the output drive gear. The housing has a cylinder inside it which is used for guiding and coacting with the piston and the cylinder walls have a step in them which coacts with a step in the piston to limit the travel forward of the piston. There are multiple inlets at the front of the housing, one from the front and one from the top so that hydraulic connections can be made either from the top or the front to increase the flexibility of the device by allowing it to be used in various locations and attitudes which would not normally be possible because of the hydraulic input lines.  
         [0088]     The piston has a conventional top surface and a shaft with a seal mounted on it. The piston shaft which then opens up into two arms as can be seen in  FIG. 8 . It also shows that there is a spring guide shaft cylinder within the piston shaft to accommodate the return spring. This enables the return spring to be thicker, and stronger and occupy much less room then the usual return spring for a piston. Normally the return spring would have to be wound around the outside of the piston shaft where it would have to have a larger area for dead ending the piston and would take up substantially more room. Here, the spring fits inside the piston spring guide cylinder and the other end acts against the back wall of the housing. The arrangement of the spring in the piston shaft with the output arm is shown best in  FIG. 9 .  
         [0089]     Note that the output arm as shown in  FIG. 10  has elongated slots at the upper end for joining to the piston so that movement of the output arm as the piston moves backward in its travel will not produce a force tending to cock the piston. Instead the arm itself will be able to slide relative to the piston, so the piston will always be working without interfering with the cylinder wall or housing.  
         [0090]     The output drive arm or output plate as shown in  FIG. 9  and  12  is provided with an output drive which has a ratchet gear with a square socket opening or which can have a square piece of stock put into the socket and held by a set screw shown in  FIGS. 11 and 13 . Access to the set screw is through the passage hole in the bottom of the output arm.  
         [0091]     When the hydraulic fluid is placed into the assembled hydraulic torque wrench, the piston will move back against the action of the spring. As it moves back, the change in height of the output arm will be compensated for by the slots in the top of the arm. The output drive will rotate with the action arm because the pawl will hold it stationary with respect to the output arm as the output arm rotates.  
         [0092]     When the output arm reaches the end of its travel as determined by the ramp in the piston, the hydraulic pressure will be released and the spring will act to return the piston to its initial starting position. The pawl will allow the output ratchet gear to slide. The cover for the output gear as shown in  FIG. 12  will be mounted so that the O-ring is within the housing and will coact with the lip of the aperture in the housing arm shown in  FIG. 5  to act as a braking system to prevent too rapid a return of the arm. The braking force can be adjusted by means of adjusting the screws as shown in  FIG. 12  which will then squeeze the O-ring appropriately against the housing as the output gear rotates.  
         [0093]     As shown in  FIG. 4  there is also a cover for the other side of the output ratchet gear.  
         [0094]     More specifically, the elements and coaction of the invention can be described as follows.  
         [0095]     As shown in the figures, the hydraulic torque wrench of the present invention as generally indicated at  100  comprises a housing  110  having a front end  115  and having side arms  120 . Apertures  130  exist in the side arms  120  for mounting of an output drive  400 . The apertures  130  have a lip  140  for mounting of a clutch or braking system  450  which will be used to control the movement of the reaction arm  490 . There is an aperture  150  near the front end  115  of the housing  110  which is used for mounting of a reaction arm  490 .  
         [0096]     A keyway  160  is formed in the rear of side arms  120  of the housing  110  for a back wall  250  to be slid into place to close the housing  110 . Alternatively, threaded passages  162  can be formed in the rear of the side arms  120  of the housing  110  and the back wall  250 . Threaded passages  162  can then be used to secure the back wall  250  to close the housing  110 . A cylinder  170  is formed within the housing  110  having a cylindrical wall  180  and a forward end  190 . A shoulder  200  opens the cylinder  170  to the rear of the housing  110 .  
         [0097]     Hydraulic inlets  220  on the front end  115  of the housing  110  and hydraulic inlet  230  on the top of the housing  110  provide access for hydraulic fluid to the cylinder.  
         [0098]     The back wall  250  of the housing  110  has a closure or pressure plate  262  for the back wall  250  of the housing  110  which covers a recess  265  which forms a seat for a return spring  340 . A piston  260  is located within the cylinder  170  of the housing  110 . It is has a front end or top surface  280  and an external piston seal  290  along its outside surface. The piston  260  has a spring guide bore  300  machined inside the piston for positioning of a return spring  340  to act against movement of the piston  260 . The piston  260  also has arms  310  which extend rearward from the forward part of the piston and are positioned so as not to interfere with the projection of the shaft  270  so that the return spring  340  can extend from within the shaft  270  to the rear of the housing  110 . The arms  310  of the piston  260  have apertures  320  in which piston pins  330  will be placed to register with elongated slots  362  in arms  360  of an output plate  350  which will respond to the movement of the piston  260 . The elongated slots  362  allow the piston  260  to move horizontally and to pivot the output plate  350  without placing a non-axial stress on the piston  260 . In other words, the piston  260  will not be cocked as it moves rearward because of the coaction between the slots  362  in one of either the piston arms  310  or the arms of the output plate  360 .  
         [0099]     The return spring  340  extends into the shaft  270  of the piston  260  and into the recess  265  in the back wall  250  of the housing. The output plate  350  has a circular opening  370  located in the bottom of the output plate  350  and an opening  380  for mounting of a pawl  420  which will coact with a ratchet gear  410  formed on the circumference of an output drive  400  which is seated in the opening  370  of the output plate  350 .  
         [0100]     The output drive  400  has threaded passages  430  for cover screws to mount the cover  440  of the output drive  400  so that the drive will remain within the output plate  350 . A brake assembly  450  for the output drive  400  is formed by an O ring  452  positioned in the cover  440  for the output drive  400  which then coacts with the lip  140  in the aperture  130  of the housing  110  so that tightening screws  454  will cause the cover  440  to squeeze the O ring  452  against the lip  140  and therefore retard the action of the output drive  400  relative to the output plate  350 .  
         [0101]     An output socket  470  can be formed in the output drive  400 . Alternatively, an output wrench  480  can be inserted into the output drive  400 . A reaction arm  490  is positioned within the aperture in the housing  150 , and a foot  500  can be placed on the reaction arm.  
         [0102]     In a further embodiment, as shown in  FIGS. 14 through 16 , the drive plate no longer has piston pins  330  that connect to the piston  260 A. Instead, the drive plate  350 A has an upper end  500  having a cam-shaped surface  510  formed to coact with a cut out portion of the piston  520  having a corresponding cam shape  525  that will allow the piston to contact the cam-shaped surface  510  at the upper end of the drive plate  350 A. Therefore, there is a much greater contact area between the drive plate or output plate  350 A and the piston  260 A than in the previous embodiment.  
         [0103]     Additionally, the piston  260 A is reconfigured to provide positive stops in coaction with the main housing  110 A. The piston  260 A has an enlarged shoulder  530  having a front face that bears against the shoulder  220 A in the housing  110 A. This provides a positive stop for the piston in the extended position of the spring  340 A under low pressure.  
         [0104]     The piston  260 A has a cutout portion forming a slot  540  in which a threaded stop  550  has a lower portion  560  that extends into slot  540  and an upper threaded portion  570  that is threaded into the wall of the housing  110 A. The end  580  of slot  540  is intended to coact with the engaging portion  560  of threaded stop  550  to provide a stop in the other limit of travel of the piston when the spring is most compressed.  
         [0105]     The threaded stop  550  coacting with the piston  260 A reduces the force that the spring  340 A exerts on the back cover  250 A of the housing  110 A. This therefore greatly relieves the stress on the fastening screws  164 A and on the rear of the housing  110 A and the back cover  250 A.  
         [0106]     From the above, it can be seen that the invention described above is a highly compact efficient, relatively lightweight, extremely versatile, compact torque wrench. Structural features of the design provide many novel advantages.  
         [0107]     While the invention has been described in its preferred embodiments, it is to be understood that the same is intended to be descriptive and not limiting and that changes may be made within the purview of the invention without departing from the true scope and spirit thereof.