Abstract:
A hydraulic pump apparatus having an internal sump formed by a housing having an internal portion and an end cap secured to the housing. A rotatable cylinder block is located in the sump and driven by an input shaft extending into the housing. The pump apparatus also has a system of hydraulic porting in fluid communication with the cylinder block. The porting includes a pair of system ports located on a first side of the hydraulic pump apparatus, a fluid inlet on a second side of the hydraulic pump apparatus, opposite the first side, and a bypass valve positioned on the second side adjacent to the fluid inlet. A case drain may also be formed on a third side of the pump apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This patent application is a continuation of application Ser. No. 11/041,781 filed on Jan. 24, 2005, which is a continuation of application Ser. No. 10/644,520 filed on Aug. 20, 2003, now U.S. Pat. No. 6,889,595, which is a continuation of Ser. No. 10/330,939 filed Dec. 27, 2002, now U.S. Pat. No. 6,694,729, which is a continuation of application Ser. No. 09/798,392, filed Mar. 1, 2001, now U.S. Pat. No. 6,502,394, which is a continuation of U.S. patent Ser. No. 09/354,850 filed Jul. 16, 1999, now U.S. Pat. No. 6,332,393. All of these prior applications and patents are incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to hydraulic pumps, although other uses will be apparent from the teachings disclosed herein. In particular, the present invention relates to Bantam Duty Pumps (BDP) which can be combined with motors and other remotely-located units. When used in this manner, these BDP units provide an infinitely variable flow rate between zero and maximum in both forward and reverse modes of operation. 
   Pumps discussed herein are of the axial piston design which utilize spherical-nosed pistons, although variations within the spirit of this invention will be apparent to those with skill in the art and the invention should not be read as being limited to such pumps. One such prior art pump is shown in  FIG. 1 . The pump is a variable displacement pump  10  designed for vehicle applications. A compression spring  12  located inside each piston  14  holds the nose  16  of the piston  14  against a thrust-bearing  18 . A plurality of such pistons positioned about the center of the cylinder  20  forms a cylinder block kit  22 . The variable displacement pump  10  features a cradle mounted swashplate  24  with direct-proportional displacement control. Tilt of swashplate  24  causes oil to flow from pump  10 ; reversing the direction of tilt of the swashplate  24  reverses the flow of oil from the pump  10 . The pump is fluidly connected with a motor to form a pump-motor circuit having a high pressure side and a low pressure side through which the oil flows. See generally  FIG. 4C . Controlling the oil flow direction, i.e. changing the high and low pressure sides, controls the motor output rotation. Tilt of the swashplate  24  is controlled through operation of a swashplate control shaft  26  (also referred to herein as trunnion arm). The trunnion arm is connected to a slide which connects with the swashplate. Generally, movement of the trunnion arm  26  produces a proportional swashplate movement and change in pump flow and/or direction. This direct-proportional displacement control (DPC) provides a simple method of control. 
   A fixed displacement gerotor charge pump  28  is generally provided in BDP units. Oil from an external reservoir (such as reservoir  200  in  FIG. 4C ) and filter is pumped into the low pressure side by the charge pump  28 . Fluid not required to replenish the closed loop flows either into the pump housing  30  through a cooling orifice or back to the charge pump  28  inlet through the charge pressure relief valve. Charge check valves  32  are included in the pump  10  and end cap  34  (cap  34 ) to control the makeup of oil flow of the system. A screw type bypass valve  36  is utilized in the pump  10  to permit movement of the machine (tractor, vehicle, etc.) and allow the machine to be pushed or towed. Opening a passage way between fluid ports with bypass valve  36  allows oil to flow, thereby opening the pump-motor circuit, which allows the motor to turn with little resistance because the vehicle wheels will not back drive pump  10 . 
   While such pumps are useful, they have the disadvantage of having a preferred alignment direction. More particularly, the housing  30  has a preferred alignment with the end cap. This preferred alignment direction is created by the hose coupling, or connections, between the motor  38  and the pump end cap  34  (see  FIGS. 2 and 3 ). The placement of the system ports  40  determines the preferred alignment of the housing  30 . This is particularly troublesome when one desires to control a hydraulically powered vehicle with pumps positioned on either side of the vehicle and where the control arms for the individual pumps also must be mounted to the outer sides thereof. A control arm for the left pump  10 L ( FIG. 2 ), for instance, can be conveniently connected to the trunnion arm  26  to provide control of the swashplate from the left. However, to connect a control arm to the right pump  10 R, for instance, the pump must be rotated to place the trunnion arm  26  nearer to the right side of the vehicle. Costly hose fittings are then required to connect the hoses  44  to the pump  10 R. Alternatively a cumbersome and costly U-shaped control linkage  46  may be connected to the trunnion arm  26  while maintaining the pump end cap in its preferred orientation, as shown in  FIG. 3 . 
   An improvement on the earlier pumps having preferred alignment is shown in  FIG. 4C ; the corresponding end cap  156  is shown in  FIG. 14A .  FIGS. 4C and 14A  disclose a prior art pump wherein the end cap  156  may be connected to the housing in one of two orientations. Specifically, end cap  156  is rotatable 180° with respect to the housing. This permits the trunnion arm  26  to be placed on opposing sides. This improved “symmetric pump” has shortcomings however which the present invention overcomes. The advantages of a symmetric pump according to the present invention over the prior art “symmetric pump” will be apparent to those with skill in the art from the teachings herein. 
   SUMMARY OF THE INVENTION 
   The present invention overcomes these and other problems by providing a pump which does not have a preferred mounting alignment. One object of the present invention is to provide a new and improved pump. A further object is to provide a symmetric pump having a symmetric housing and a symmetric end cap. 
   Another object of the present invention is to provide an improved hydrostatic vehicle. Another object of the present invention is to provide means for utilizing a hydraulic pump in multiple directions without the cost of expensive fittings and accessories. 
   Accordingly, the present invention includes a pump having a housing and an end cap. The housing includes a pump shaft rotatably supported therein. The end cap may be connected to the housing in either a first position or a second position rotated relative to the housing from the first position about an axis through the pump shaft. 
   Another embodiment of the invention includes a pump comprising an end cap and a housing connectible to the end cap in either a first position relative to the end cap or a second position rotated relative to the first position. The second position is rotated relative to the end cap (and the first position) about an axis through the housing and the end cap. The housing is connected to the end cap in one of the first or second positions. 
   Another embodiment of the invention includes a pump comprising a housing and a swashplate rotatably supported in the housing. A pump shaft is supported by the housing and extends through the swashplate. A trunnion arm is extended from the housing and positioned to vary or act upon the operation of the swashplate. An end cap is connected to the housing. The end cap has a system port opening external thereto in a first orientation. The pump further comprises connection means for connecting the housing to the end cap in one of a first position and a second position such that the trunnion arm extends in a first direction and the system port opens in the first orientation when the housing is connected to the end cap in the first position. The connection means also provides connection such that the trunnion arm extends in a second direction and the system port opens in the first orientation when the housing is connected to the end cap in the second position. 
   The invention includes an end cap for a hydraulic pump, wherein the pump  10  includes a housing adapted to connect to the end cap. 
   The end cap comprises a first edge and a second edge separated by a third edge. A first check plug and a first case drain are positioned in the first edge. A second check plug and a second case drain are positioned in the second edge. A pair of system ports are positioned in the third edge. 
   The invention also provides a control device for a hydraulic pump having a housing and a swashplate operably supported therein and a trunnion arm engaging the swashplate. The control device comprises a control arm attached to the trunnion arm and a stud mounted in and extending from the housing a spaced distance from the trunnion arm. The stud is positioned parallel to the trunnion arm. Structure is attached to the stud and engages the control arm to restrict rotation of the control arm. 
   A symmetric pump comprising structure to restrict movement of the control arm is also provided. The present invention also provides a method of securing a swashplate in a neutral position for shipment and attachment to a vehicle. 
   Other objects and advantages of the present invention will be apparent from the following detailed discussion of exemplary embodiments with reference to the attached drawings and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows an exploded isometric view of a prior art pump having a preferred alignment. 
       FIG. 2  is a schematic plan view of a prior art arrangement of two pumps respectively connected to two motors. 
       FIG. 3  shows a schematic plan view of an alternate prior art method of connecting two pumps respectively to two motors including a U-shaped control linkage with alignment bearing connected to one of the pumps. 
       FIG. 4  is a plan partial view of two pumps positioned in a hydraulic vehicle according to the present invention. The pump housings are rotated relative to the respective end caps to provide access to the trunnion arms. 
       FIG. 4A  shows an elevation view of the vehicle shown in  FIG. 4 . The pumps are shown forward of the seat, but are typically positioned under the vehicle&#39;s seat. 
       FIG. 4B  shows a plan view of two pumps according to the present invention connecting in a closed loop to a hydraulic fluid reservoir. Case drains and charge inlet lines are arranged to provide a clean simple hydraulic connection. 
       FIG. 4C  shows a plan view of two prior art pumps connected to a hydraulic reservoir. A more complicated case drain and charge inlet line arrangement, as compared with the arrangement of  FIG. 4B , is required to connect the pumps with the reservoir in a closed loop system. 
       FIG. 5  shows an exploded isometric view of a pump according to the present invention. 
       FIG. 5A  shows an auxiliary charge pump attached to the pump of  FIG. 5 . 
       FIG. 5B  is an enlarged view of the symmetric housing and symmetric end cap shown in  FIG. 5 . 
       FIG. 6  shows a side view of the pump of  FIG. 5  assembled. The trunnion arm extends out of the page. 
       FIG. 7  shows the pump side opposite the view depicted in  FIG. 6 . 
       FIG. 8  shows the pump in  FIG. 6  with the trunnion arm rotated to extend downward. 
       FIG. 9  shows an end view of the pump of  FIG. 8  looking down the pump shaft. 
       FIG. 10  shows a partial cut-away view of the pump depicted in  FIG. 9  from the opposing direction. 
       FIG. 11  depicts the pump shown in  FIG. 8  with the housing rotated 180° relative to the end cap. 
       FIG. 12  shows the pump of  FIG. 9  with the housing rotated 180° relative to the end cap. 
       FIG. 13  shows the pump shown in  FIG. 10  with the housing rotated 180° relative to the end cap. 
       FIG. 14  shows a section view of the pump shown in  FIG. 10  looking toward the housing. 
     The section view is through the end cap and more clearly shows a symmetrical porting system. 
       FIG. 14A  shows a section view through a prior art end cap. 
       FIG. 15  is a section view of the end cap shown in  FIG. 14  looking away from the housing. 
       FIG. 16  is a section view through section line  16 — 16  of the pump shown in  FIG. 13 . 
       FIG. 17  is similar to the pump shown in  FIG. 7  with the addition of an auxiliary pump. 
       FIG. 18  depicts the pump shown in  FIG. 17  rotated 45° about the pump shaft. 
       FIG. 19  is an end view of the pump shown in  FIG. 18 . The view is looking toward the auxiliary pump with the housing projecting into the page. 
       FIG. 20  shows the pump depicted in  FIG. 19  with the housing rotated 180° relative to the end cap. 
       FIG. 21  shows a section view of the pump shown in  FIG. 18 . The view is rotated to match the view shown in  FIG. 16 . 
       FIG. 22  shows a pump similar to the pump shown in  FIG. 16  and  FIG. 21 . The pump shown is of a through-shaft design. 
       FIG. 23  depicts a section view through the pump shown in  FIG. 22  rotated 90° about the pump shaft. 
       FIG. 24  shows a side view of a pump similar to a pump shown in  FIG. 6  further including a control device.  FIGS. 24–27  show different views of this pump. 
       FIG. 25  is a view of the pump of  FIG. 24  rotated 90° about the pump shaft. A control device including a friction pack is attached to the housing. 
       FIG. 26  is a view of the pump of  FIG. 25  rotated about an axis through the trunnion arm and then rotated about an axis through the pump shaft. The view looks down the pump shaft. 
       FIG. 27  is a view of the pump of  FIG. 26  looking toward the end cap. 
       FIG. 28  is a side view of a pump similar to the pump shown  FIG. 24 , this pump includes a lock-down element. 
       FIG. 29  shows a view similar to the pump of  FIG. 25 . The control device shown includes a lock-down element. 
       FIG. 30  shows a view of the pump of  FIG. 29  rotated about an axis through the trunnion arm and then rotated about an axis through the pump shaft. 
       FIG. 31  shows a view of the opposite end of the pump shown in  FIG. 30 , looking toward the end cap. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   The present invention is discussed in relation to a hydraulic pump, and in particular, a bantam duty variable displacement pump; other uses will be apparent from the teachings disclosed herein. The present invention will be best understood from the following detailed description of exemplary embodiments with reference to the attached drawings, wherein like reference numerals and characters refer to like parts, and by reference to the following claims. 
     FIG. 4  depicts a simplified pump and motor arrangement for a hydraulically powered vehicle  48 . More generally the hydraulically powered vehicle  48  is a hydraulically powered apparatus. In most applications, the hydraulically powered vehicle  48  is a wide-area walk behind, zero-turn commercial mower, or the like. Symmetric hydraulic pumps  50  are respectively connected to hydraulic motors  38 ; and motors  38  are respectively connected to the wheels  52 . The symmetric hydraulic pumps  50  (also referred to more generally as pumps  50 ) are connected to motors  38  via hoses  44 . Preferably hoses  44  are high pressure hoses. Each symmetric pump  50  includes a symmetric housing  54  and a symmetric end cap  56 . The housings  54  are rotated relative to the respective end caps  56  to position control arms  58  conveniently about either side of the seat  60 . 
     FIG. 4A  shows a simplified elevated side view in which pump  50  is positioned under seat  60 . The seat  60  is supported on the vehicle frame  62 . 
   Other hydraulic vehicle  48  arrangements in keeping with the scope of the present invention will be apparent to those with skill in the art. Furthermore, use of the term “symmetric” does not imply identical structural symmetry, but rather implies functional symmetry. The end cap should be sufficiently functionally symmetric to connect to the housing in one of at least two positions, wherein the other positions are rotated relative to the one position. In a like manner, a symmetric pump is sufficiently symmetric to achieve an objective, whether fit with an end cap, a vehicle, or the like. 
     FIG. 4B  depicts a symmetrical pump  50  connected to a fluid reservoir  200 . A T-connection  201  connects hydraulic case drain hoses  202 ,  203 , and  204 . Positioning the case drain openings (discussed in more detail below) to open generally facing each other provides for a simple clean uncomplicated connection. By contrast, see  FIG. 4C , wherein the case drain hose  203  is required to wind around one of the pumps  50  to connect to the reservoir  200 . 
     FIG. 14  shows an end cap according to the present invention and should be contrasted with  FIG. 14A  which shows an end cap according to the prior art. The prior art pump allows the end cap to be connected to the housing in one of two orientations. The prior art pump, however, contains only one case drain, thus requiring a more complicated closed system loop connection. 
   Also of interest, and shown more clearly in  FIGS. 14 and 14A , is the positioning of the bypass valve  84 , also referred to as a bypass spool. The bypass valve of the present invention is positioned generally opposite one of the system ports to provide easier access to the bypass valve to and a cleaner closed loop connection. Other advantages of the present invention over the prior art will be apparent from the teachings disclosed herein. 
     FIG. 5  shows an exploded isometric view of a pump  50  according to the present invention. The hydraulic pump  50  comprises a symmetric housing  54  rotatably supporting a pump shaft  64 . A symmetric end cap  56  is attached to the symmetric housing  54 . The symmetric end cap  56  includes a porting system  66 , as shown in more detail in  FIGS. 14 and 15 . A valve plate  57  connects the cylinder  20  and the end cap  56 . In a preferred embodiment the end cap porting system  66  is symmetric. The porting system includes a pair of system ports  68  and  70  opening external to the end cap  56 . The pair of kidney ports  72  and  74  are in fluid communication with the system ports  68  and  70 . The valve plate  57  has a pair of ports conforming to the kidney ports  72  and  74 . The porting system preferably includes a pair of check orifice assemblies  76  and  78  opening externally and internally to the end cap  156 . The porting system  66  may also include a pair of case drain orifices (ports)  80  and  82  opening external to the end cap  56 . 
   The case drains  80  and  82  are drains or connections that divert excessive fluid (e.g. leakage fluid from the pistons) to the reservoir  200 , thereby reducing pressure in the pump housing  54 . Case drain plugs  81  are preferably of a metal material if they are intended to be of a more permanent element or fixture;  FIG. 17  shows a metal plug  81  and  FIG. 14  shows a plastic plug  81 . Note the hex tool attachment for the metal plugs  81  rather than the slot tool attachment for the plastic drain plugs  81 . Plastic plugs are useful, for economic reasons, if the plugs are intended to be replaced, such as when they serve as shipping plugs which will be removed by a customer or vehicle manufacturer. Line fittings are then connected to the case drains  80  and  82  to attach the pump to the reservoir or other components. For some applications, only one case port is machined; then the one machined case port is generally case port  80 . When two ports are machined, one plastic cap and one metal cap are used in the respective ports. 
   Preferably a bypass valve  84  is provided in fluid communication with the porting system  66  to allow the vehicle  48  to be moved short distances without engaging the engine. The pair of system ports  68  and  70  may be capped with shipping plugs  86  which are preferably of a plastic material. Check plugs  88  use check springs  90  to secure check orifice valves  92  in the pair of check orifices  76  and  78 . In  FIG. 5 , charge pump housing  122  covers the gerotor  28 . 
     FIG. 5A  depicts an exploded isometric view of pump  50  shown in  FIG. 5  further including an auxiliary charge pump  93  having an auxiliary charge manifold pump  94  operating in conjunction with a gerotor  96 . The auxiliary charge manifold  94  and gerotor  96  are in fluid communication with kidney ports  71  and  73 . The auxiliary pump is typically used to supply pressurized fluid to additional remote locations. The charge manifold  94  and gerotor  96  may be in fluid communication with external devices, such as deck lifts, power steering units and the like. The auxiliary charge pump  93  further includes a filter cover  124  connecting a filter to the auxiliary charge manifold  94 .  FIG. 5B  shows an enlarged view of the symmetric housing  54  and the symmetric end cap  56 . Kidney ports  71  and  73  are also shown in  FIG. 5   b  connected with geroter  28 ; see also  FIG. 23 . 
     FIGS. 6–10  show views of the pump  50  with the end cap  56  connected in a first position.  FIGS. 11–15  show the pump  50  end cap  56  in a second position. Specifically,  FIGS. 8 ,  9 , and  10  show views of pump  50  positioned in the first position  105 ; and  FIGS. 11 ,  12  and  13  show corresponding views of the pump  50  positioned in the second position  107 . 
     FIG. 6  shows a side view of the pump  50  assembled, where trunnion arm  26  extends out of the page.  FIG. 7  shows pump  50  of  FIG. 6  rotated 180° about pump shaft  64 . Drain case orifice  82  is shown without a drain plug in  FIG. 6 .  FIG. 7  shows a steel case drain plug  81  in case drain port  80 .  FIG. 8  depicts pump  50  shown in  FIGS. 6 and 7  rotated about the pump shaft  64  to an orientation between those shown in  FIGS. 6 and 7 . The view looks down system ports  68  and  70 .  FIG. 9  shows pump  50  of  FIG. 8  rotated about the axis of trunnion arm  26  and then about pump shaft  64 . The view looks down the axis of pump shaft  64 .  FIG. 10  is a view of pump  50  of  FIG. 9  looking toward gerotor cover  122  and the end cap  56 . 
   Accordingly, the present invention includes a hydraulic pump  50  wherein the end cap  56  is connected to the housing  54  in a first position and connectible to the housing  54  in a second position, i.e., the end cap  56  is connected in either the first position  105  or the second position  107 , but not both simultaneously. The second position is rotated relative to the housing  54  about an axis  98  (see  FIG. 5 ) through the pump shaft  64 . Referring to  FIGS. 8 and 11 , the housing  54  is rotated 180° relative to the end cap  56  from the first position  105  shown in  FIG. 8  to the second position  107  shown in  FIG. 11 . Because the end cap  56  can be maintained in one position, or preferred alignment or orientation, conventional hose fittings and shorter less costly hoses may be used to attach motor connection hoses  44  to the end cap  56 . The need for expensive fittings and control arm connectors is eliminated by rotating the housing  54  while maintaining the end cap  56  in a fixed orientation. 
   In a preferred embodiment, the second position  107  is rotated 180° relative to the end cap  56  as compared to the first position  105 . This allows the end cap  56  to be maintained in a fixed orientation. Rotating the housing  54  provides convenient access to the trunnion arm  26 . The trunnion arm  26  is positioned to affect the tilt of the swashplate, and thus to control direction of the pump output and operation of the vehicle. 
     FIGS. 14 and 15  show section views through end cap  56 .  FIG. 14  looks down the pump shaft in the direction of the housing  54 .  FIG. 15  shows the direction view of  FIG. 14  from the opposite direction, looking away from the pump housing. 
   In one embodiment, pump shaft  64  axis  98  lies in a plane  100  and the porting system  66  is symmetric with respect to the plane  100 , which is shown in  FIG. 14 .  FIG. 14  also shows a charge diagnostic port  102  lying in plane  100  perpendicular to pump shaft  64 . A cooling orifice  104  is disposed in the charge diagnostic port  102 . 
     FIG. 14  showing an end cap  56  according to the present invention should be contrasted with the  FIG. 14A  showing an end cap  156  according to the prior art. The prior art contains only one case drain  80  whereas the present invention end cap  56  contains two or more case drains  80  and  82 . Also note the positioning of the bypass spool valve  84 . The bypass valve of the present invention is preferably positioned opposite one of the system ports  68  or  70 . Modifications in keeping with the spirit of this invention will be apparent to those with skill in the art. The advantages over the prior art end cap  156  will be apparent from the comparison of  FIGS. 4B and 4C . 
   In the embodiment shown in  FIGS. 5 and 14 , trunnion arm  26  extends from the housing  54  perpendicular to the plane  100  shown in  FIG. 14 . As will be apparent from  FIGS. 14 and 15  the end cap need only comprise a portion sufficiently symmetric to allow the housing to be connected in either the first position  105  or the second position  107 . Generally the manufacturer of the pump will assemble the pump with the housing in either the first or second position relative to the end cap  56 . However, vehicle/apparatus manufacturers can simply modify the housing orientation by removing flange bolts  120  and rotating the end cap  56  relative to the housing  54 . Preferably the symmetric portion includes the pair of system ports  68  and  70  and the pair of check orifices  76  and  78  which are respectively fluidly communicating with the pair of system ports  68  and  70 . 
   The trunnion arm  26  extends from the housing  54  in a first direction  106  when the housing  54  is attached to the end cap  56  in a first position, as shown in  FIG. 8 . The first position is designated generally by reference number  105 .  FIG. 11  shows the housing  54  attached to the end cap  56  in a second position which is designated generally by reference number  107 . The trunnion arm  26  is shown extending from the housing  54  in a second direction  108  when the housing is attached to the end cap  56  in the second position  107 . 
   Generally, the invention comprises connection means  110  ( FIGS. 5 and 14 ) for connecting the housing  54  to the end cap  56  in one of a first position  105  and a second position  107  (See  FIGS. 8 and 11 ). The connections are such that the trunnion arm  26  extends in a first direction  106  and the system port  68  opens in a first orientation  112  (shown in  FIG. 14 ) when the housing  54  is connected to the end cap  56  in the first position  105 . The connections are also such that the trunnion arm  26  extends in a second direction  108  and the system port  68  opens in the first orientation  112  when the housing  54  is connected to the end cap  56  in the second position  107 . 
   In  FIGS. 8 and 11  the first orientation  112  is out of the pages. Preferably the connection means  110  (shown in  FIG. 5 ) comprises the symmetric porting system  66  to allow the end cap  56  to interface with the housing  54  in two different orientations ( 105  and  107 ). 
   The end cap  56  shown in  FIG. 14  includes a first edge  114  and a second edge  116  opposing each other and separated by a third edge  118 . The first check orifice  76  and the first case drain  80  are positioned in the first edge  114 . The second check orifice  78  and the second case drain  82  are positioned in the second edge  116 . A pair of system ports  68  and  70  are positioned in the third edge  118 . Preferably, the first check orifice  76  and the first case drain  80  are shown arranged symmetric with the second check orifice  78  and the second case drain  82 . The third edge  118  generally includes the charge diagnostic port  102 . 
     FIG. 16  shows a section view related to pump  50  shown in  FIG. 11 . Slot guide  126  interfaces with the trunnion arm  26  and the swashplate  24 . 
     FIG. 17  shows a side view of the pump shown in  FIG. 7  further including an auxiliary pump  94 .  FIG. 18  is the pump of  FIG. 17  rotated 45° about the pump shaft  64  (i.e. about axis  98 ).  FIG. 19  is an end view of the pump  50  looking toward the filter cover  124 . The housing is shown in the first position  105 .  FIG. 20  is the pump  50  of  FIG. 19  wherein the housing  54  is rotated to the second position  107 . The end cap  56  is maintained in a fixed orientation. 
     FIG. 21  shows a section view through the pump  50  having an auxiliary pump  94 . The view is similar to the section view shown in  FIG. 16 .  FIG. 22  shows a section view cut, lengthwise through a through-shaft design of the pump shown in  FIG. 16 .  FIG. 23  shows a section view through the pump  50  shown in  FIG. 22  rotated 90° about the pump shaft. 
     FIGS. 24–27  show varying views of one embodiment of a control device  130  for a hydraulic pump  50  having a housing  54  and a swashplate (not shown) operably supported therein. A trunnion  26  engages the swashplate.  FIG. 24  is similar to  FIG. 6 ,  FIG. 25  is similar to  FIG. 8 ,  FIG. 26  is similar to  FIG. 9 , and  FIG. 27  is similar to  FIG. 10 . The control device  130  comprises a control arm  132  attached to the trunnion arm  26 . A stud  134  is mounted in and extends from the housing  54  a spaced distance  136  from the trunnion arm  26  (see  FIG. 25 ). The stud  134  is parallel to the trunnion arm  26 . Structure  138  is attached to the stud  134  and engages the control arm  132  to restrict rotation of the trunnion arm  26 . The control device  130  may be used to improve operational control of the apparatus and provide cruise control. Thus, the cruise control force required may range from a “minimum force” to a “hands-free” level of input. Other forms of control arm stops will be apparent. 
   In the embodiment shown in  FIGS. 24–27  the control device  130  frictionally restricts movement of the control arm  132 . In this embodiment the structure  138  includes friction washers  140  and  141  engaging either side of the control arm  132  and a spring  142  positioned against the friction wash  141  to increase resistance of movement of the control arm  132 . The spring  142  is mounted on the stud  134  and pushes against the friction washer number  141  in a direction toward the control arm  132  such that friction washes  140  and  141  are compressed. A spacer  144 , typically of powdered metal (p.m.) material, is positioned in the spring  142 . Washers  146  and  148  abut the spring  142 . The invention provides a means for limiting control arm travel. This reduces the need for a vehicle manufacturer to provide a travel limiting device. 
     FIGS. 28–31  depict an embodiment of the control device  130  wherein the structure  138  includes a lock-down element  150  mounted on the stud  134 . Referring to  FIGS. 24 and 28 , the control arm  132  includes a surface  152  defining an opening  154  through which the stud  134  extends. In the embodiment shown the opening  154  is an elongated curve or arcuate opening. 
   The trunnion arm  26  rotation is limited as the ends of the arcuate member contact the fixed stud  134 . 
   From the foregoing it will be apparent that the present invention includes a symmetric pump  50  comprising a housing  54  including a trunnion arm  26  extending therefrom. A symmetric end cap  56  is attached to the housing  54 . A control arm  132  is attached to the trunnion arm  26 . Structure  138  is attached to the housing  54  and engages the control arm  132  to restrict movement of the trunnion arm  26 . In the embodiment shown in  FIGS. 24–27  the structure  138  comprises a friction pack  156  including a spring  142  engaging the control arm  132 . Both the lock-down structure  150  and the friction pack  156  typically include a nut  158  compressing the friction pack  156  components to restrict movement of the control arm  132  relative to the stud  134 . In the lock down  150  application shown, the nut  158  fixes the control arm  132  to the stud  134  to prevent rotation of the control arm  132 . Thus, movement of the swashplate is prevented. 
   From the foregoing it will also be apparent that the present invention comprises a method of providing a hydraulic pump, typically from the pump manufacturer to an assembler of hydraulic vehicles. The method includes positioning a swashplate in a housing of the pump in a neutral position. The swashplate is then locked into a neutral position for shipping. It will be understood that when the swashplate is in the neutral position it is not in a “forward” or a “reverse” position. Typically, when in the neutral position, the swashplate will not act to cause the pump to displace fluid. This is important for set-up and alignment in a vehicle. 
   The unit will typically be shipped to a predetermined location such as a vehicle assembler/manufacturer. The method may include attaching the locked-down unit to a vehicle in a predetermined orientation. Motor hoses are attached to the unit and the system is adjusted. The unit may be unlocked for later use or remain locked for shipment with the vehicle. Preferably the step of locking the swashplate comprises fixing the control arm, which is attached to a trunnion arm, to a stud extending from the housing. The lock-down feature, which may be simply “locking” the friction pack components by tightening the nut, provides a means for the vehicle manufacturer to attach linkages and adjust the linkage when the pump is in a “known” neutral position. This reduces uncertainty, improves reliability and thereby reduces labor costs as well as damage due to mis-alignment. 
   Thus, although there have been described particular embodiments of the present invention of a new and useful pump, it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.