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:
[0001]    CROSS REFERENCE TO RELATED APPLICATION  
         [0002]    This application is based upon and claims the benefit of provisional application No. 60/299,534 filed Jun. 20, 2001. The entire contents of this provisional application are incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0003]    The present invention relates to power tools and particularly to hydraulic torque wrenches.  
         BACKGROUND OF THE INVENTION  
         [0004]    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.  
           [0005]    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  
         [0006]    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.  
           [0007]    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.  
           [0008]    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.  
           [0009]    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.  
           [0010]    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.  
           [0011]    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.  
           [0012]    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.  
           [0013]    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.  
           [0014]    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.  
           [0015]    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.  
           [0016]    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  
       [0017]    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:  
         [0018]    [0018]FIG. 1 is a side view drawing of a compact torque wrench of the current invention.  
         [0019]    [0019]FIG. 2 is a rear view drawing of the torque wrench shown in FIG. 1.  
         [0020]    [0020]FIG. 3 is a top view drawing of the torque wrench shown in FIG. 1 showing the housing only.  
         [0021]    [0021]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.  
         [0022]    [0022]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.  
         [0023]    [0023]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.  
         [0024]    [0024]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.  
         [0025]    [0025]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.  
         [0026]    [0026]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.  
         [0027]    [0027]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.  
         [0028]    [0028]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.  
         [0029]    [0029]FIG. 12 shows the orientation of the brake assembly with the output drive gear.  
         [0030]    [0030]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. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    Glossary of Terms  
         [0032]    a)  100  hydraulic torque wrench general  
         [0033]    b)  110  housing  
         [0034]    i)  120  side arms  
         [0035]    [0035] 130  aperture for the output drive  
         [0036]    [0036] 140  lip for mounting the clutch system  
         [0037]    [0037] 150  aperture for reaction arm  
         [0038]    [0038] 160  keyway for mounting back wall of housing  
         [0039]    [0039] 162  threaded passages in side arms as alternative  
         [0040]    [0040] 164  stress securing back wall to housing  
         [0041]    ii)  170  cylinder  
         [0042]    [0042] 180  walls  
         [0043]    [0043] 190  end  
         [0044]    [0044] 200  shoulder  
         [0045]    iii) Inlets  
         [0046]    [0046] 220  front inlet  
         [0047]    [0047] 230  top inlet  
         [0048]    [0048] 240  hydraulic connection  
         [0049]    iv)  250  back wall of housing  
         [0050]    [0050] 260  closure of pressure plate for back wall of housing  
         [0051]    [0051] 270  recess for seating spring  
         [0052]    c)  260  piston  
         [0053]    i)  270  shaft  
         [0054]    [0054] 280  top surface  
         [0055]    [0055] 290  seal  
         [0056]    [0056] 300  spring guide shaft or cylinder within the piston  
         [0057]    ii)  310  arms  
         [0058]    iii)  320  apertures for piston pins  
         [0059]    [0059] 210  piston  
         [0060]    iv)  330  piston pins  
         [0061]    d)  340  return spring  
         [0062]    e)  350  output arm or output plate  
         [0063]    i)  360  wings of output plate  
         [0064]    [0064] 362  elongated slots  
         [0065]    ii)  370  circular opening for output drive gear  
         [0066]    iii)  380  opening for mounting pawl  
         [0067]    iv)  390  access opening for set screw in output drive  
         [0068]    f)  400  output drive  
         [0069]    i)  410  ratchet gear  
         [0070]    ii)  420  pawl in output arm  
         [0071]    iii)  430  threaded passages for cover screws  
         [0072]    iv)  440  cover for ratchet gear  
         [0073]    [0073] 450  brake assembly for ratchet gear  
         [0074]    [0074] 452  O ring in cover for ratchet  
         [0075]    [0075] 454  screw in cover for squeezing O ring against lip  140   
         [0076]    v)  460  set screw to hold output socket or output wrench  
         [0077]    vi)  470  output socket  
         [0078]    vii)  480  output wrench (alternate)  
         [0079]    g)  490  reaction arm  
         [0080]    h)  500  foot of reaction arm  
         [0081]    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.  
         [0082]    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.  
         [0083]    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.  
         [0084]    The output drive arm or output plate as shown in FIGS. 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.  
         [0085]    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.  
         [0086]    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.  
         [0087]    As shown in FIG. 4 there is also a cover for the other side of the output ratchet gear.  
         [0088]    More specifically, the elements and coaction of the invention can be described as follows.  
         [0089]    As shown in the figures, the hydraulic torque wrench of the present invention comprises as generally indicated at  100  and comprises a housing  110  having a front end and having side arms  120 . Apertures  130  exist in the side arms for mounting of an output drive. The apertures  130  have a lip  140  for mounting of a clutch or braking system which will be used to control the movement of the reaction arm. There is an aperture  150  in the front of the housing which is used for mounting of a reaction arm.  
         [0090]    A keyway  160  is formed in the rear arms of the housing for a rear wall to be slid into place to close the housing. Alternatively, threaded passages can be formed in the rear of the arms of the housing and the back wall. Threaded passages being designated at  162  which can then be used to secure the back wall to close the housing. A cylinder  170  is formed within the formed the housing cylindrical wall  180  and a forward end  190 . A shoulder  200  opens the cylinder to the rear of the housing.  
         [0091]    Hydraulic inlets  220  on the front and  230  on the top provide access to hydraulic fluid to the cylinder.  
         [0092]    The back wall of the housing  250  has a closure  260  for the back wall of the housing which covers a recess  270  which forms a seat for a return spring  340 . A piston  260  is located within the cylinder of the housing. It is has an end or top surface  280  and an external piston seal along its outside surface. The piston has a spring guide shaft  300  machined inside the piston for positioning of a return spring to act against movement of the piston. The piston 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 to the rear of the housing. The arms of the piston have apertures  320  in which piston pins 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. The elongated slots allow the piston to move horizontally and to pivot the output plate without placing a non-axial stress on the piston. In other words, the piston will not be cocked as it moves rearward because of the coaction between the slots in one of the either piston arms or the arms of the output plate.  
         [0093]    The return spring  340  extends into the shaft of the piston and into the recess  270  in the back wall  250  of the housing. The output plate  350  has a circular opening  370  located in the bottom on the plate and an opening  380  for mounting of a pawl which will coact with a ratchet gear  410  formed on the circumference of an output drive  400  which is seated in the opening of the output plate  370 .  
         [0094]    The output drive has threaded passages for screws to mount the cover of the output drive so that the drive will remain within the output plate. A brake assembly for the output drive is formed by an O ring positioned in the cover for the output drive which then coacts with the lip in the aperture of the housing so that tightening screws  454  will cause the cover  440  to squeeze the O ring against the lip and therefore retard the action of the output drive relative to the output plate.  
         [0095]    An output socket can be formed in the output drive as indicated  470 . Alternatively, an output wrench  480  can be inserted into the output drive. A reaction arm  490  is positioned within the aperture in the housing  150 , and a foot  500  can be placed on the reaction arm.  
         [0096]    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.  
         [0097]    While the invention has been described in its preferred embodiment, 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.