Abstract:
A wrench is disclosed which provides a hydraulically powered ratchet wrench within a compact footprint. One hydraulically powered piston operates to tighten a fastener, while a second hydraulic piston is operable to reset the first piston in preparation for a subsequent tightening operation. An intermediary torque multiplying device may be placed between the driven pistons and the object being acted upon by the pistons. Fluid supply hoses may be coupled to the wrench assembly using a two-axis swivel to facilitate insertion of the wrench assembly into areas that are difficult to access.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The disclosure of U.S. Pat. No. 6,260,443, to Spirer, issued Jul. 17, 2001, is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     Hydraulically powered wrenches are known in the art. In one existing system, a linear hydraulic piston turns a link plate, which in turn causes a lever arm having a spring-loaded pawl thereon to rotate and thereby impart torque to a fastener having teeth that engage the pawl. Spring action may then be used to transmit force through the drive train of the apparatus to reset the position of the piston. Thus, hydraulic force to the piston may be released, whereupon a spring may force the link plate and lever arm to retrace the motion undertaken during the piston stroke. During the spring-forced movement of the link plate and lever arm, the pawl reverses its motion with respect to the teeth on the driven member using a conventional ratcheting function. Once the spring driven stroke is complete, the entire mechanism is ready for the next piston power stroke to turn the driven member again. The above cycle may be repeated as many times as needed to complete a tightening function or any other desired operation. 
     A problem with the above approach is that spring-driven repositioning systems tend to be slow. Moreover, the piston-repositioning spring may weaken over time. Once this occurs, the repositioning spring may become incapable of properly repositioning the linkage to be powered by the piston, thus rendering the overall apparatus inoperable. Moreover, repairing or replacing the spring is expensive and time consuming. 
     Another approach to using hydraulic power for high-torque wrenches involves providing two fluid inputs to a cylinder, one on either side of the piston. A first fluid inlet at a proximal end of the cylinder is used to force the piston in a first direction to deliver tightening force through the linkage (discussed above) to a driven member. The equipment is moved in the reverse direction to reset the pawl and the position of the piston by providing pressurized fluid to a second fluid inlet to the cylinder at the distal end of the cylinder to force the piston into a retracted position. 
     However, this approach also presents drawbacks. Providing and servicing the described second fluid inlet to the cylinder is cumbersome and expensive. Moreover, when operating within a confined space, extending pressurized fluid tubes to the second fluid inlet tends to be cumbersome and to inhibit optimal operation of a hydraulic wrench under such demanding circumstances. Further, to provide an opening into the area at the distal end of the cylinder typically requires a bore be drilled through an outer and inner cylinder, so that the outer cylinder can be plugged, causing the fluid to flow from the space between the two, into the inner cylinder. In many instances, the high pressure of the hydraulic fluid causes the plug to pop out of the outer cylinder, which in turn causes hydraulic fluid to leak, and the device to become essentially inoperable. 
     Accordingly, there is a need in the art for an improved system and method for restoring a hydraulic piston to an initial position. 
     SUMMARY OF THE INVENTION 
     According to one aspect, the invention is directed to a hydraulic wrench that may include a cylinder assembly disposed within a housing including first and second cylinders therein; first and second supply hoses, extending from a fluid supply, and carrying fluid therein; a swivel coupling the first and second hoses to the to the cylinder assembly; a first piston, within the first cylinder, coupled to the first hose and to a drive train, the first piston operable to transmit force through the drive train to transmit torque to a fastener to be driven by the wrench upon extending out of the first cylinder; and a second piston, within the second cylinder, coupled to the second hose and to the drive train, and operable, upon extending out of the second cylinder, to transmit force through the drive train to force the first piston into a refracted position. 
     Other aspects, features, advantages, etc. will become apparent to one skilled in the art when the description of the preferred embodiments of the invention herein is taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For the purposes of illustrating the various aspects of the invention, there are shown in the drawings forms that are presently preferred, it being understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. 
         FIG. 1  is a perspective view of a hydraulic wrench in accordance with an embodiment of the present invention; 
         FIG. 2A  is a plan view of the top of the hydraulic wrench of  FIG. 1  showing one axis of rotation of a swivel assembly; 
         FIG. 2B  is a side view of the hydraulic wrench of  FIG. 1  showing another axis of rotation of the swivel assembly; 
         FIG. 3A  is a plan view of the hydraulic wrench of  FIG. 1  showing a piston assembly and a drive train thereof in accordance with an embodiment of the invention; 
         FIG. 3B  is a side view of the hydraulic wrench of  FIG. 3A  showing the motion of the swivel assembly about a first axis; and 
         FIG. 4  is a more detailed plan view of the hydraulic wrench of  FIG. 1  showing the piston assembly, the drive train, and drive member of the hydraulic wrench of  FIG. 1  in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one having ordinary skill in the art that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the present invention. Furthermore, reference in the specification to phrases such as “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of phrases such as “in one embodiment” or “in an embodiment” in various places in the specification do not necessarily all refer to the same embodiment. 
       FIG. 1  is a perspective view of a hydraulic wrench  10  in accordance with an embodiment of the present invention.  FIG. 1  shows hoses  210  and  220  (collectively hoses  200 ), housing  100  and swivel  250  (also referred to herein as a “swivel assembly”). 
       FIG. 2A  is a plan view of the top of the hydraulic wrench  10  of  FIG. 1  showing axis of rotation  252  of swivel assembly  250 . Herein, axis  252  may be referred to as the “yaw” axis or the “lateral axis” given the relation between axis  252  and the longitudinal axis of housing  100  of wrench  10 .  FIG. 2B  is a side view of the hydraulic wrench of  FIG. 1  showing axis of rotation  254  of swivel assembly  250 . Herein, axis  254  is also referred to as the “pitch axis” or “tilt axis” of rotation given the relation between axis  254  and the longitudinal axis of housing  100  of wrench  10 . 
       FIG. 3A  is a plan view of the hydraulic wrench  10  of  FIG. 1  showing a piston assembly  300  and a drive train  400  (also referred to herein as the power train) in accordance with an embodiment of the invention.  FIG. 3B  is a side view of the hydraulic wrench of  FIG. 3A  showing the articulation of the swivel assembly about the pitch axis  254 . 
       FIG. 3A  shows a bisecting line “A” extending along the longitudinal axis of housing  100  of wrench  10 . Preferably, in the embodiment of  FIG. 3A , dimensions A 1  and A 2  on opposite sides of bisecting line A are at least substantially equal. Moreover, in addition to being substantially equal in width, the portions of housing  100  having widths A 1  and A 2 , respectively, are preferably substantially symmetrical. More specifically, the weight and of distribution of equipment is either the same or very close to the same on both sides of the bisecting line. For instance, input drive center piece  410  and drive plate  420  preferably operate substantially symmetrically about the bisecting line A. Moreover, cylinders  310  and  320  are preferably positioned symmetrically with respect to bisecting line A. A further aspect of this embodiment is that the input hoses  200  ( FIG. 1 ), the swivel assembly  250 , and the member  430  to be driven by hydraulic wrench  10  are preferably all located on a common axis. Preferably, swivel axle  240  pivots within two distinct cylinders without a need for pressure plugs. 
       FIG. 4  is a more detailed plan view of the hydraulic wrench of  FIG. 1  showing the piston assembly  300 , the drive train  400 , and driven member  430  (which may be a fastener) of the hydraulic wrench of  FIG. 1  in accordance with an embodiment of the present invention. 
     The features discussed below enable wrench  10  to be placed into tightly spaced areas with limited access and still deliver a high level of torque needed for various applications. The swivel feature preferably enables high pressure fluid to be provided to a point near the proximal end of housing  100  (i.e. the end of the housing at which the swivel assembly is located) even if the length of the hoses leading up to housing  100  need to be held at awkward angles with respect to the longitudinal axis of housing  100 . 
     Moreover, the deployment of two single-acting pistons preferably obviates the need to provide pressurized fluid to distal ends (the leftmost ends of the cylinders in the views of  FIGS. 3A and 4 ) of cylinders  310  and  320 , thereby further increasing the ability to position housing  10  in tightly spaced surroundings in which delivery of pressurized fluid to distal ends of cylinders  310 ,  320  would be difficult. In the following, the parts and connections of the apparatus are discussed, followed by a discussion of the operation of a preferred embodiment of wrench  10 . 
     With reference to  FIGS. 3A and 4 , wrench  10  may include swivel assembly  250  (also referred to herein as “swivel”  250 ), piston assembly  300 , drive train  400 , and driven member  430  (such as a fastener). Swivel assembly  250  preferably includes hinges and/or linkage suitable for providing a yaw axis of rotation  252  (rotation within a plane parallel to the top surface of housing  100 ) and a pitch axis (which corresponds to rotation along a “tilt” angle) axis of rotation  254  (see  FIG. 2 ). Piston assembly  300  may include cylinder  310  and associated piston  312 , and cylinder  320  and associated piston  322 . 
     Drive train  400  may include input drive center piece  410  which may pivot about pivot point  414 , drive plate  420  which may pivot about pivot point  424 , pawl  422 , ratchet  432 , and reaction pawl  426 . Drive train  400  may be operable to turn driven member  430 , which may be a fastener. 
     The operation of wrench  10  is now discussed with reference to  FIGS. 3A and 4 . With reference to  FIG. 4 , when wrench  10  is ready to impart torque to, and perform a tightening operation on, driven member  430 , a suitable switch (not shown) is activated to allow pressurized fluid into fluid port  314  of cylinder  310 , which operates to force piston  312  outward (i.e. leftward in the view of  FIG. 4 ). This begins the transfer of force through the drive train  400  during what is referred to herein as the “power stroke.” 
     As piston  312  advances out of cylinder  310 , linkage coupling piston  312  and drive center piece  410  turns input drive center piece  410  clockwise about pivot point  414 . The rotation of drive center piece  410  in turn causes drive plate  420  to rotate counter-clockwise by virtue of the junction between parts  410  and  420  at pin  418 . Pawl  422  is preferably rigidly attached to drive plate  420  and thus rotates with plate  420 . In doing so, pawl  422  forces the teeth on ratchet  432  to rotate counter-clockwise about pivot point  424  in conjunction with the movement of drive plate  420 . The movement of ratchet  432  causes driven member  430  to move counter-clockwise. In the above-described manner, the release of pressurized fluid into cylinder  310  transmits force and torque through drive train  400  to thereby impart torque and rotational motion to driven member  430 . 
     Having discussed the forward stroke of piston  312  within cylinder  310 , it remains to describe the operation of the reset stroke which forces piston  312  back into a retracted position (which corresponds to the rightmost position of piston  312  in the view of  FIG. 4 ). By way of illustration,  FIG. 3A  shows piston  312  fully retracted within cylinder  310 . In brief, the reset stroke is executed by implementing a forward stroke of piston  322  within cylinder  320 , and using drive train  400  to force piston  312  back into a fully refracted position within cylinder  310 . 
     When wrench  10  is ready for the reset stroke to begin, the fluid connection for fluid port  314  of cylinder  310  is preferably shifted from a supply of pressurized fluid to a receiver of exhausted fluid. Once this shift has taken place, piston  312  is preferably not being forced in either direction until the reset action of piston  322  gets under way. 
     Thereafter, the reverse shift is preferably performed for fluid port  324  of cylinder  320 . Specifically, the fluid connection for fluid port  324  is preferably shifted from a receiver of exhausted fluid (which would have been needed for piston  322  to retract during the power stroke of piston  312 ) to a supply of pressurized fluid. Thus, pressurized fluid is allowed into inlet  324  of cylinder  320  causing piston  322  to extend outward (i.e. leftward in the view of  FIG. 4 ). As piston  322  extends leftward, input drive center piece  410  is forced to rotate counter-clockwise (CCW), around pivot point  414 , by virtue of the linkage coupling piston  322  with drive center piece  410 . The CCW motion of drive center piece  410  causes drive plate  420  to rotate clockwise, thereby moving pawl  422  over the teeth of ratchet  432  without moving driven member  430 . This ratcheting function is enabled by the provision of teeth within pawl  422  that are spring-loaded in the direction of engagement with ratchet  432 . Thus, as pawl  422  retracts toward a reset position with respect to ratchet  432 , the teeth of pawl  422  preferably ride over the teeth of ratchet  432  without imparting any significant torque thereto. At the same time, reaction pawl  426  preferably operates to block clockwise motion by driven member  430  and ratchet  432 . Reaction pawl  426  can be disengaged using screw  500 . 
     Moreover, as drive center piece  410  proceeds counter-clockwise, linkage coupling drive center piece  410  to piston  312  forces piston  312  toward a retracted position within cylinder  310 . Preferably, the forced retraction of piston  312  exhausts the fluid in cylinder  310  through fluid port  314  to a suitable container configured to receive exhausted fluid. In this manner, piston  312  preferably gets fully reset and ready to conduct another power stroke to impart torque to driven member  430  whenever desired. Moreover, pawl  422  is preferably also fully reset and suitably engaged with the teeth on ratchet  432  so that when drive plate  420  is again rotated counter-clockwise, pawl  422  will be suitably positioned to force driven member  430  counter-clockwise. 
     In a preferred embodiment, the diameter, length, and thus the force that can be applied by piston  312  in cylinder  310  may exceed the corresponding characteristics of piston  322  of cylinder  320 . This is because piston  312 , while urged forward with hydraulic pressure, performs the force-intensive task for imparting torque to driven member  430  to tighten driven member  430  against substantial resistance. The demands on piston  322  of cylinder  320  are considerably less demanding. For example, the force of piston  322  does not need to tighten, or loosen, driven member  430 . 
     Instead, the force of advancement of piston  322  is needed move the various parts of drive train  400  into a reset position to prepare the next power stroke by piston  312 . The resistance to this movement is minimal compared to that faced by piston  312 . Specifically, the advancement of piston  322  rotates drive plate  420  clockwise (which does not incur the force of rotating driven member  430 ) and in doing so moves pawl  422  over the teeth of ratchet  432 , which requires minimal torque. The advancement of piston  322  also rotates drive center piece  410  counter-clockwise about pivot point  414  and in so doing forces piston  312  back into a fully retracted position (i.e. all the way to the right, as shown in  FIG. 3A ). Forcing piston  312  into a retracted position requires exhausting fluid within cylinder  310  out of fluid port  314  through the hoses connected to swivel  250  and ultimately to a suitable container (not shown). 
     In an alternative embodiment, wrench  10  may be used as mechanical multiplier in which input C of input drive center piece  410  may be used as an input by a tool, which tool may be machine-driven or manually driven. The mechanical multiplier effect may arise because of the selection of dimensions for input drive center piece  410  and of drive plate  420 . More specifically, if the pin connection between drive center piece  410  and drive plate  420  is closer to the pivot point  414  of drive center piece  410  than to the center  424  of drive plate  420 , then a mechanical advantage is obtained by rotating drive center piece  410  with a tool (not shown) over attempting to directly rotate drive plate  420  with the same tool. 
     Various details regarding the operation of the driving elements, links, and pins connecting various elements of the drive train  400  in addition to discussions of various torque ratios relevant to the operation of the above are discussed in U.S. Pat. No. 6,260,443 which has been incorporated by reference herein in its entirety. 
     It is noted from  FIG. 4 , for example, the force used to apply the required torque and to return the piston  312  to its initial position within cylinder  310  is not generated by introducing hydraulic fluid through a second input within cylinder  310  at a distal end (leftmost in the views of  FIGS. 3A and 4 ) of piston  310 . Instead, piston  312  is restored to its initial position by flowing hydraulic fluid into cylinder  320  to extend piston  322  outward (i.e. leftward in  FIG. 3A ) and using the linkage forming part of drive train  400  to force piston  312  back into its initial position. This approach eliminates the need for the holes to be plugged as discussed above with respect to the prior art. This, in turn, avoids the possibility of the plug failing and leaking hydraulic fluid out. 
     It is noted that the term cylinder is used to denote the compartment within which the hydraulic fluid is pressurized to provide force, and that such term therefore refers to any such compartment, even if its shape is not cylindrical. That is, the “cylinder” could be rectangular, or of any other cross sectional shape. Moreover, while the present disclosure describes the application of the cylinder arrangement of  FIGS. 3A and 4  to a hydraulic wrench, it will be appreciated that the present invention is not limited to this application. Indeed, the cylinder arrangement disclosed herein may be employed with other types of hydraulically powered tools. 
     Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.