Abstract:
In a variable displacement hydraulic pump having a housing with a multiplicity of interconnected surfaces, including opposed end surfaces and intermediate side surfaces, the improvement comprising the location of at least one case drain orifice in each of a plurality of differing ones of the surfaces in a manner such that at least one of the orifices is located in the vicinity of the top surface of the housing in any spatial orientation of the housing.

Description:
CROSS-REFERENCE TO RELATED CASES  
       [0001]    The present application claims the benefit of the filing date of U. S. Provisional Application Serial No. 60/458,109; filed Mar. 26, 2003, the disclosure of which is expressly incorporated herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a housing for a variable displacement hydraulic pump and particularly to the case drain orifices in the housing of a light duty pump.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates to hydraulic pumps, and in particular to light duty pumps. Light duty pumps are typically used in hydrostatic transmissions for turf equipment propulsion systems.  
           [0004]    Pumps, both conventional and light duty, have numerous ports for receiving connectors of fluid lines that link with the motor, reservoir, and components. One of these ports is the case drain port which connects with the case drain line that leads to the reservoir. Typically this fluid line is inflexible and is routed to mate with the pump in a designated area. When the pump does not have a port in the designated area, an adapter and extra conduit is needed to reach this other location. This is an obstacle for the mechanic when connecting the lines.  
           [0005]    Also, it is preferable to have the port connection located in an area that is easy to access. Typically this is the top side of the pump. Port connections located in side and bottom surfaces can be difficult to access due to the limited space available. Access is needed since the pump has to be removed from the equipment when it undergoes routine maintenance or when it needs to be replaced. It is an obstacle when the port connection is located in a difficult to reach location.  
           [0006]    Most prior art conventional pumps use one case drain port on one surface of the pump housing. An example of such a pump is shown in prior art reference U.S. Pat. No. 3,810,715 to Week et al. Conventional pumps are typically installed in a fixed direction with its shaft directed horizontally. Other prior art conventional pumps have two case drain orifices located on the top and bottom surfaces of the pump housing. This design provides more flexibility with routing to the case drain port for pumps that have the shaft directed horizontally.  
           [0007]    Light duty pumps are less heavy than conventional pumps and can have multiple orientations. Unlike the conventional pumps, light duty pumps can have its shaft positioned upwards and downwards. For case drain line routing purposes it is advantageous to have a port accessible in each routing. Certain prior art light duty pumps have multiple ports, but these are located in the endcap of the pump. Examples of these pumps are shown in U.S. Pat. No. 6,332,393 B1 to Trimble and U.S. Pat. No. 6,494,686 B1 to Ward. The disadvantage with these style pumps is that when the pump shaft is directed upwards, the endcap and case drain orifice is on the bottom of the pump and difficult to access.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides a housing for a variable displacement hydraulic pump having a total of six side portions comprised of an open first longitudinal end, a spaced, open second longitudinal end, and four adjoining radial sides connecting the longitudinal ends. The housing further has a porting system with at least one case drain orifice in at least two differing ones of the six side portions. A further feature of the present invention has the variable displacement pump being of a light duty variety.  
           [0009]    Another feature of the noted housing has one of the at least one case drain orifice located in an upwardly-directed generally horizontal surface position, regardless of the spatial orientation of the housing. A further feature of the noted housing has one of the at least one case drain orifice located at an upper-most section of the housing in any spatial orientation of the housing. Still a further feature of the noted housing has one of the at least one case drain orifice located at a front-most section of the housing in any spatial orientation of the housing. Yet another feature of the noted housing has one of the at least one case drain orifice located at the rear-most section of the housing in any spatial orientation of the housing. A further feature of the noted housing has one of the at least one case drain orifice located at a bottom-most section of the housing in any spatial orientation of the housing. Further features and advantages of the present invention will become apparent to those skilled in the art upon review of the following specification in conjunction with the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 shows an isometric view of a pump according to the present invention located in a first spatial orientation.  
         [0011]    [0011]FIG. 2 shows an isometric view of the pump according to the present invention located in a second spatial orientation.  
         [0012]    [0012]FIG. 3 shows an isometric view of the pump according to the present invention located in a third spatial orientation.  
         [0013]    [0013]FIG. 4 shows an isometric view of the pump according to the present invention located in a fourth spatial orientation.  
         [0014]    [0014]FIG. 5 shows an isometric view of the pump according to the present invention located in a fifth spatial orientation.  
         [0015]    [0015]FIG. 6 shows an isometric view of the pump according to the present invention located in a sixth spatial orientation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The present invention relates to a hydraulic pump, and in particular to a light duty pump  10  used, for example, in a hydrostatic transmission. Pump  10  is of the axial piston design and combines with a motor, not shown, and other accessories to comprise the hydrostatic transmission. Pump  10  is a variable displacement pump and is typically used in turf equipment propulsion systems. As is well known in the art, a variable displacement pump enables the equipment to smoothly transition from neutral to forward or reverse.  
         [0017]    Referring to FIG. 1, pump  10  has a housing  15  and an affixed endcap  17 . Endcap  17  is sealingly affixed to a first longitudinal end  22  of housing  15 . A pump shaft  24  extends axially from a second longitudinal end  23  of housing  15 . Endcap  17  not only seals one end of pump  10 , but also houses components for controlling the fluid system and provides connection orifices for the motor (not shown). Specifically, endcap  17  includes an end cap first side surface  25  having a first system port  32  and a second system port  33  that provide connections with lines that fluidly interface with the motor. A diagnostic port  38  is located between ports  32 ,  33 . Diagnostic port  38  leads to the outlet of the charge pump, not shown. It should be noted that cap first side surface  25  which contains ports  32 ,  33 ,  38  is basically an extension or continuation of a pump first side portion  30 , i.e. cap first side  25  and pump first side portion  30  are substantially coplanar.  
         [0018]    Endcap  17  further has a third system port  34  and a check valve orifice  41  located in an end cap second side surface  26  adjacent to one end of pump first side portion  30  at first port  32 . Third system port  34  provides an alternative location for a connection with the motor if the pump is oriented in such a way that makes the fluid line routing more convenient. Third system port  34  would replace either first or second port  32 ,  33  depending on which side third system port is located. An endcap, or steel plug  36  is shown closing third port  34 . Check valve orifice  41  leads to a bore that houses a check valve for controlling the charge pump make-up flow for the hydrostatic (closed-loop) transmission. Again, it should be noted that cap second side surface  26 , which contains port  34  and check valve orifice  41 , is substantially co-planar with a pump second side portion  50 .  
         [0019]    Referring now to FIG. 3, contained in an end cap fourth side surface  28 , adjacent to another end of pump first side portion  30  at second port  33  is a second check valve orifice  42 . Second check valve orifice  42  leads to a bore that houses a check valve for controlling the charge pump make-up flow. Yet again, it should be noted that cap fourth side surface  28 , which contains second valve orifice  42  is substantially co-planar with a pump fourth side portion  70 .  
         [0020]    Referring back to FIG. 2, a bypass valve orifice  45  and a charge pump inlet port  47  are located in an endcap third side surface  27  adjacent to one end of pump fourth side surface  28 , remote from second check valve orifice  42 . This side of endcap  36  is directly opposite first and second system ports  32 ,  33 . Bypass valve orifice  45  houses bypass valve  49  which is used to divert fluid from flowing through the pump in order to move the vehicle a short distance without engaging the engine. Charge pump inlet port  47  receives a fluid line from the system reservoir, not shown. Finally, it should be noted that cap third side surface  27 , which contains bypass valve  49  and charge pump inlet orifice  47 , is substantially co-planar with a pump third side portion  60 . Advancing now to FIG. 4, this view basically details the intersection of adjacent pump second and third portions  50  and  60  as well as the intersections of adjacent end cap second and third side surfaces  26 ,  27 .  
         [0021]    Referring to FIGS. 1-4, pump housing  15  has six side portions. The axial ends are comprised of first and second longitudinal housing ends  22 ,  23 . Located between these two ends  22 ,  23  are the four radial side portions  30 ,  50 ,  60  and  70 . As discussed above, pump first side portion  30  is located on the same radial side as end cap first and second system ports  32 ,  33  in end cap first side surface  25 . Adjacent first side portion  30  is second side portion  50  which is on the same radial side as end cap third system port  34  and first check valve orifice  41  in end cap second side surface  26 . Adjacent pump second side portion  50  and opposite pump first side portion  30  is pump third side portion  60 . Pump third side portion  60  is on the same radial side as end cap bypass valve orifice  45  and charge pump inlet port  47  in end cap third side surface  27 . Adjacent pump third side portion  60  and directly opposite pump second side portion  50  is pump fourth side portion  70 . Fourth side portion  70  is on the same radial side as end cap second check valve orifice  42  in end cap fourth side surface  28 .  
         [0022]    Looking at the orientation of pump  10  in yet another way, and using longitudinal axis  29  of pump shaft  24  as a reference line, the pump four radial side portions  30 ,  50 ,  60  and  70  are progressively shown in an upper horizontal surface portion in FIGS. 1, 3,  2  and  4 , respectively, which represent successive 90° counterclockwise shifts, of pump  10 , respectively. The spatial orientation of pump  10  within a piece of equipment can vary based on the overall design of the hydrostatic transmission. For example, one manufacturer may position pump  10  with side portion  30  facing up or substantially horizontally, as shown in FIG. 1. Alternatively, another manufacturer may position pump  10  such that the first longitudinal end  22  of housing  15  is positioned upwardly or substantially vertically, as shown in FIG. 6. Since there are six side portions, it is possible for any of these portions to be facing a certain spatial direction. Numerous connections are therefore possible with pump  10  and a correct alignment of pump  10  is necessary to mate with these connections. For example, a conduit may need to serve as the conductor of fluid between the motor and pump  10  and may need to be connected with first system port  32 . It is most likely that the conduit is a hard plumbed pipe that ends in a fixed position. If pump  10  is not properly aligned so that first system port  32  mates with the conduit, then an adapter and excess conduit is needed for a connection. Each port on pump  10  requires this same precise alignment.  
         [0023]    As is well known in the art internal leakage within the pump, caused by high pressure and lubrication, flows directly into the pump case. This leaking fluid then flows from the pump case to low pressures case drain lines which serve as drains for diverting excess fluid to a reservoir in order to reduce pressure in the pump. Pump  10  has multiple case drain ports so that a convenient connection can be made with the drain line conduit in any spatial orientation of the pump. Although the case drain conduit line can be initially routed to mate with any side of pump  10 , once the case drain conduit line is set, it is important that the pump (and any subsequent replacement pump) have a mating port aligned with the case drain conduit line. The following discussion and related FIGS. 1-6 presume that the case drain conduit line is routed to mate with the top side of pump  10 .  
         [0024]    When pump  10  is oriented as shown in FIG. 1 with pump first side portion  30  upwardly directed, or in substantially horizontal position, a first case drain  75  is located at the top of pump  10  so that a convenient connection can be made. Likewise, when pump  10  is oriented as shown in FIG. 2 with pump third side portion  60  upwardly directed, a second case drain  77  is located at the top of pump  10 . Similarly, when pump  10  is oriented as shown in FIG. 3 with pump fourth side portion  70  upwardly directed, again first case drain  75  is located near the top of pump  10  so a convenient connection can again be made. Alternatively, when pump  10  is oriented as shown in FIG. 4 with pump second side portion  50  positioned upwardly, a third case drain  79  is located in the vicinity of the top of pump  10 . Case drain  77  could also be used when pump is oriented as shown in FIG. 4.  
         [0025]    If pump  10  is oriented as shown in FIG. 5 with pump shaft  24  positioned upwardly and second longitudinal end  23  in a vertically upper position, a fourth case drain  81  is located near the top of pump  10  for easy connection. When pump  10  is oriented as shown in FIG. 6 with pump shaft  24  positioned downwardly and first longitudinal end  22  in a vertically upper position, case drains  77  (not shown in that view),  79  and  75  can be used for the case drain conduit line connection. It should be noted that the generally vertical orientations shown in FIGS. 5 and 6 are limited to light duty pumps. Due to the weight of conventional pumps, they are typical installed horizontally, i.e. with the pump shaft in generally horizontally oriented axis, as shown in FIGS. 1-4.  
         [0026]    With the spatial arrangements of case drain ports ( 75 ,  77 ,  79 , and  81 ), the case drain conduit line does not have to be inconveniently redirected or lengthened since a port ( 75 ,  77 ,  79 , and  81 ) is in close proximity to the hard plumbed case drain conduit line. Although the above description discussed in regard to an example where the case drain conduit line is directed to mate with the top side of pump  10 , the same convenient mating occurs when the case drain conduit line is positioned on any side of pump  10 . However, it should be noted that linking the case drain conduit line to the a port on top of the housing will improve the lubrication of the internal rotary components of pump  10  and carry away any debris for better contamination control. This extends the endurance life of pump  10 .  
         [0027]    It should be noted that the present invention is not limited to the specified preferred embodiments and principles. Those skilled in the art to which this invention pertains may formulate modifications and alterations to the present invention. These changes, which rely upon the teachings by which this disclosure has advanced, are properly considered within the scope of this invention as defined by the appended claims.