Abstract:
A spring loaded device assembly includes a spring loaded device for use with hydraulic systems, the spring loaded device including: a spring mechanism disposed in an outer tubular member; an inner tubular member movably disposed in one end of the outer tubular member; an adjustment rod movably disposed in the inner tubular member; a clevis attached to a distal end of the adjustment rod for attachment to a hydraulic system; and a rigid mounting member having two ends, a first end being attached to another end of the outer tubular member, and a second end being attached to the hydraulic system to prevent swivel of the spring loaded device.

Description:
The present invention relates to a spring loaded device assembly for centering controls on hydrostatic transmissions and non-detented hydraulic valves used in vehicles. 
   BACKGROUND OF THE INVENTION 
   Previous spring loaded devices, as shown in  FIG. 1 , include self-centering mechanisms  100  for push-pull control cables  101 , which are especially useful for centering controls on hydrostatic and non-detented hydraulic valves used in vehicles. 
   The spring loaded device of  FIG. 1  is a push-pull coaxial cable control mechanism  100 , and in particular, a self-centering apparatus that is mounted directly on standard control cables  101  or as part of a new control cable for imparting spring return force to cable members  101  in response to relative movement thereof, out of a predetermined intermediate or neutral position. The conventional spring loaded devices were designed to eliminate bulky dual-spring systems and extra brackets and levers. 
   In particular, a conventional self-centering spring mechanism is described in detail in U.S. Pat. No. 4,223,564 to Fawcett, the entire contents of which are herein incorporated by reference. 
   In Fawcett, the self-centering spring mechanism  200  is applied to a push-pull coaxial cable mounted on the end assembly of a control cable  201 . The cable  201  terminates in a mounting fixture  202  threaded over a portion of its length to receive jamb nuts  203 ,  204  designed to clamp against opposite sides of a support such as a mounting panel  205  through which the fixture  202  passes. 
   The self-centering device  200  includes outer and inner elongated tubular members  206 ,  207  forming an annular space between them in which an elongated helical spring  208  is received. The spring  208  is partially compressed in the neutral or centered position of the parts. 
   Actuator rod  209  is threaded over a portion of its projecting length to engage in the threaded socket of a connecting clevis  210  linked by pivot pin  211  to the transmission actuator arm. A jamb nut  212  on the rod  209  bears against the end of the clevis  210  to tighten the connection. 
   In this conventional cable assembly and its conventional connection by way of the clevis  210  to the transmission shifter arm (not shown) of a hydrostatic drive transmission, relative longitudinal movement of the cable members are effected at a remote point (see  103 ,  FIG. 1 ), such as in the truck cab, and causes the shifter arm to be moved between its neutral setting (N) and either of the forward (F) and reverse (R) gear positions (see  FIG. 2 ). The stationary mounting panel  205  to which the mounting fixture  202  is secured, takes the reaction force attending forced movement of the shifter arm. 
   Thus, the self-centering spring device  200  imposes a substantial return force on the shifter arm in response to appreciable displacement of the arm out of position (N), and the force increases as a function of the displacement regardless of the direction in which it occurs. 
   However, in conventional systems, the spring device  200  is too large in diameter to fit well to the frame of a hydraulic system. Further, the larger end  102  of the spring loaded device  100  (see  FIG. 1 ) has a swivel integrated into it. The cable  101  passes through this swivel into the spring loaded device  100 . However, when the spring loaded device  100  is mounted with the smaller end attached to the pedal shaft  103 , and the spring cycled, the swivel allows the spring loaded device  100  to collapse when the system causes the inner spring  208  to compress. In other words, the system would work if the spring  208  was extended, but not when the spring  208  was compressed. 
   Accordingly, a self-centering spring mechanism which would overcome these disadvantages and which would provide a stable and reliable system for centering controls on hydrostatic transmissions and non-detented hydraulic valves, is desired. 
   SUMMARY OF THE INVENTION 
   The present invention relates to improvements in conventional spring loaded devices which prevents swivel of the spring loaded device when attached to a hydraulic system. 
   In one embodiment consistent with the present invention, a spring loaded device assembly includes a spring loaded device for use with hydraulic systems, the spring loaded device including: a spring mechanism disposed in an outer tubular member; an inner tubular member movably disposed in one end of the outer tubular member; an adjustment rod movably disposed in the inner tubular member; a clevis attached to a distal end of the adjustment rod for attachment to a hydraulic system; and a rigid mounting member having two ends, a first end being attached to another end of the outer tubular member, and a second end being attached to the hydraulic system to prevent swivel of the spring loaded device. 
   In another embodiment consistent with the present invention, the mounting member includes a threaded hole through which a bolt is threaded into the other end of the outer tubular member. 
   In yet another embodiment consistent with the present invention, the hydraulic system is a bi-directional piston pump. 
   In yet another embodiment consistent with the present invention, the spring loaded device starts the hydraulic system from only in the neutral position. 
   In yet another embodiment consistent with the present invention, a distal end of the clevis is attached to a swash plate shaft of the piston pump. 
   In yet another embodiment consistent with the present invention, the spring mechanism moves the clevis through positions corresponding to forward, reverse, and neutral gear positions. 
   In yet another embodiment consistent with the present invention, a spring loaded device assembly includes a spring loaded device for use with hydraulic systems, the spring loaded device including: a spring mechanism disposed in an outer tubular member; an inner tubular member movably disposed in one end of the outer tubular member; an adjustment rod movably disposed in the inner tubular member; a clevis attached to a distal end of the adjustment rod for attachment to a hydraulic system; and means for providing rigidity to the spring loaded device when attached to a hydraulic system. 
   In yet another embodiment consistent with the present invention, the rigidity means includes a mounting member having two ends, a first end being attached to another end of the outer tubular member, and a second end being attached to the hydraulic system to prevent swivel of the spring loaded device. 
   In yet another embodiment consistent with the present invention, a spring loaded device assembly includes a spring loaded device for use with hydraulic systems, the spring loaded device assembly including means for preventing swivel of the spring loaded device when attached to a hydraulic system. 
   In yet another embodiment consistent with the present invention, the swivel preventing means includes a rigid mounting member having two ends, a first end being attached to one end of the spring loaded device, and another end being attached to the hydraulic system. 
   In yet another embodiment consistent with the present invention, a spring loaded device assembly includes a spring loaded device for use with hydraulic systems, the spring loaded device assembly including a rigid mounting member having two ends, a first end being attached to one end of the spring loaded device, and a second end being attached to a hydraulic system to prevent swivel of the spring loaded device. 
   Finally, in yet another embodiment consistent with the present invention, the two ends of the mounting member are vertical portions connected by a horizontal portion. 
   There has thus been outlined, some features consistent with the present invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features consistent with the present invention that will be described below and which will form the subject matter of the claims appended hereto. 
   In this respect, before explaining at least one embodiment consistent with the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Methods and apparatuses consistent with the present invention are capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting. 
   As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the methods and apparatuses consistent with the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a perspective view of a conventional spring loaded device, connected to a push-pull coaxial cable assembly. 
       FIG. 2  shows a cross-sectional view of a conventional spring loaded device, in a reverse gear position. 
       FIG. 3  shows one side view of a spring loaded device assembly, according to one embodiment consistent with the present invention. 
       FIG. 4  shows one side view of the spring loaded device assembly of  FIG. 3 , connected to a bi-directional piston pump, according to one embodiment consistent with the present invention. 
       FIG. 5  shows a top view of the spring loaded device assembly of  FIG. 4 , in the neutral position, according to one embodiment consistent with the present invention. 
       FIG. 6  shows one top view of the spring loaded device assembly of  FIG. 4 , in the forward position, according to one embodiment consistent with the present invention. 
       FIG. 7  shows one top view of the spring loaded device assembly of  FIG. 4 , in the reverse position, according to one embodiment consistent with the present invention. 
       FIG. 8  shows one top view of the spring loaded device assembly of  FIG. 4 , connected to a pedal shaft. 
   

   DESCRIPTION OF THE INVENTION 
   One embodiment of the spring loaded device assembly  300 , consistent with the present invention, is shown in  FIG. 3 . The inner structure of the spring loaded device  300 A contains similar features as those described in U.S. Pat. No., 4,223,564 to Fawcett, as previously generally described. 
   As shown in  FIG. 3 , one embodiment of the spring loaded device assembly  300  includes an outer tubular structure  301 , which has one end  302  fastened to a vertical portion  303   a  of a mounting bracket  303  via a threaded bolt  304  to provide rigidity to the spring loaded device  300 A and assembly  300 . The threaded bolt  304  is internally threaded into the spring loaded device  300 A similar to that shown in  FIG. 2 , for example. Further, the spring loaded device assembly  300  can be bolted in any position  360  degrees around the threaded bolt (see  FIG. 8 , for example). 
   In one embodiment consistent with the present invention, the mounting bracket  303  includes a horizontal portion  303   b , which runs parallel to the outer tubular member  301 , and a second vertical portion  303   c  at the other end  305  of the mounting bracket  303 . For additional stability, the second vertical portion  303   c  may include a horizontal portion  303   d  which extends from vertical portion  303   c . However, the mounting bracket  303  can be in any shape (i.e., vertical, horizontal) necessary to attach to any structure. 
   Vertical portion  303   c , and in one embodiment, horizontal portion  303   d , at end  305  of the mounting bracket  303 , may be used to mount spring loaded device  300 A to a bi-directional piston pump  400 , for example (see  FIG. 4 ), in order to prevent movement of the spring loaded device  300 A and to provide rigidity and stability. Further, a direct attachment of the spring loaded device assembly  300  to the bi-directional piston pump  400 , for example, adds a higher level of safety to the entire machine. For example, in conventional spring loaded device assemblies, the cable system  101  could sieze or jam, thus, causing the vehicle to take off. By having the spring loaded device assembly  300  attached directly to the pump  400 , if the controls fail, the vehicle will return to neutral and stop. 
   Mounting means may include at least one hole in vertical portion  303   c , or in horizontal portion  303   d , for example, for insertion of at least one nut  401  (see  FIG. 4 ). 
   However, one of ordinary skill in the art would realize that other means for providing rigidity to the ends  302 ,  305  of the spring loaded device  300 A may be used, such as a rod or a supporting mechanism which would rigidly support the spring loaded device  300 A to the piston pump  400  or other system. 
   In another embodiment consistent with the present invention, the smaller end  307  of the spring loaded device  300 A includes a clevis  308  (see  FIG. 3 ) which is attached to a swash plate shaft  402  (see  FIG. 4 ) of a bi-directional piston pump  400 , for example, via an attachment means. 
   In one embodiment consistent with the present invention, the attachment means includes a plate  403  (see  FIG. 4 ) bolted to the tip end of the clevis  308 , with a cotter pin  404  securing the plate  403  to the swash plate shaft  402 . However, other attachment means to the piston pump  400  can be used, such as a bolt, at the swash plate shaft  402 , etc., as would be readily apparent to one of ordinary skill in the art. 
   In one embodiment consistent with the present invention, the clevis  308  is attached to an all-threaded adjustment rod  309  (see  FIG. 3 ) having a jamb nut  310  and  311  at both ends of the rod  309 . The rod  309  is inserted into an inner tubular member  312 , which is disposed in the outer tubular member  301 . Similarly to the Fawcett spring loaded device, for example, the outer and inner tubular members  301 ,  312  form an annular space between them in which an elongated helical spring (not shown) is received. The spring is partially compressed in the neutral or centered position of the parts. 
   In one embodiment consistent with the present invention, a pedal shaft  500  (see  FIG. 8 ) attaches the clevis  308  of the spring loaded device assembly  300  to a pedal  501  which is operated by a user. 
   In operation, in one embodiment consistent with the present invention, when the user activates the pedal  501 , the system must be in the neutral (N) position to start. This is a safety feature, and the electrical connections would only allow the spring loaded device assembly  300  to activate the pump  400  in the neutral (N) position. 
   When started by the user activating the pedal  501 , the user then places the piston pump  400  or hydrostatic drive transmission into the forward (F) position from the neutral (N) start position (see  FIG. 8 ), and the pedal shaft mechanism  500  turns, moving the plate  403 , such that the plate  403  moves in a first direction in a horizontal plane. The adjustment rod  309  is moved such that it enters the outer tubular member  312  of the spring loaded device  300 A, compressing the spring within the outer tubular member  301 , and the clevis  308  moves from a centered or neutral position (N) (see  FIG. 5 ) in a horizontal direction toward the one end  305  of the spring loaded device  300 A to the forward (F) position (see  FIG. 6 ). 
   When the user activates the pedal  501  and places the piston pump  400  or hydrostatic drive transmission into the reverse (R) position (see  FIG. 7 ), the pedal shaft mechanism  500  turns, moving the plate  403 , such that the plate  403  moves in a second direction, opposite to the first direction, in a horizontal plane. The adjustment rod  309  is moved such that it extends from the outer tubular member  301  of the spring loaded device  300 A, decompressing the spring within the tubular member  301 , and the clevis  308  moves from a centered or neutral position (N) in a horizontal direction away from the end  305  of the spring loaded device  300 A to the reverse (R) position (see  FIG. 7 ). 
   To return to the neutral (N) position from forward (F) or reverse (R) gear positions, would require decompression or compression, respectively, of the spring in outer tubular member  301 , as described above. 
   Thus, the only external moveable parts of the embodiment described above of the present invention are the inner, smaller tubular member  312 , and the threaded adjustment rod  309  of the spring loaded device  300 A. Further, the spring loaded device  300 A of the present invention is made smaller in order to fit more easily with the bi-directional piston pump or other hydraulic devices. 
   Thus, the present invention removes the conventional cable assembly  101  (see  FIG. 1 ) which was previously attached to the one end of the conventional spring loaded device  100 . Further, with the addition of a mounting bracket  303  (see  FIG. 3 ), the spring loaded device assembly  300  of the present invention eliminates the swivel associated with the one end of the spring loaded device  100 , which caused the spring holder to essentially collapse when the inner spring was compressed. Thus, the cable assembly  101  of conventional systems is no longer necessary, and the spring loaded device  300 A is rigidly held to prevent any movement of the device  300 A that could cause collapse. 
   It should be emphasized that the above-described embodiments of the invention are merely possible examples of implementations set forth for a clear understanding of the principles of the invention. Variations and modifications may be made to the above-described embodiments of the invention without departing from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the invention and protected by the following claims.