Inline tandem pump

[0002] This invention relates to hydraulic pumps.

[0003] A dual tandem pump having an input shaft that is separate from the pump input shafts is disclosed herein. The details of this invention are set forth below in connection with the detailed description of the embodiments.

[0004] FIG. 1 is an external side view of a tandem pump in accordance with one embodiment of this invention.

[0005] FIG. 2 is a cross-sectional view along the lines 2—2 in FIG. 1.

[0006] FIG. 3 is a cross-sectional side view along the lines 3—3 in FIG. 2.

[0007] FIG. 4 is a schematic of the hydraulic circuit of the embodiment of this invention shown in FIG. 1.

[0008] FIG. 5 is a cross-sectional side view of a second embodiment of this invention.

[0009] FIG. 6 is a schematic of the hydraulic circuit of the embodiment of this invention shown in FIG. 5.

[0010] FIG. 7 is a cross-sectional side view of a third embodiment of this invention.

[0011] FIG. 8 is a schematic of the hydraulic circuit of the embodiment of this invention shown in FIG. 7.

[0012] FIG. 9 is a side view of a fourth embodiment of this invention.

[0013] FIG. 10 is a cross-section side view of a fifth embodiment of this invention.

[0014] FIG. 11 is a cross-sectional view of the fifth embodiment of the pump apparatus shown along the lines 11—11 in FIG. 10.

[0015] FIG. 12 is a cross-sectional view of an end cap of the fifth embodiment of this invention shown along the lines 12—12 in FIG. 10.

[0016] FIG. 13 is a schematic showing the embodiment of FIGS. 10-12.

[0017] FIG. 14 is a cross-sectional side view of a sixth embodiment of the present invention.

[0018] One embodiment of this invention is shown in FIGS. 1, 2, 3 and 4, which depict a pump apparatus 10 having a unitary housing 12. In the embodiment described below, two generally identical pumps 11aand 11bare disclosed within unitary housing 12, and identical numerals with the letters a and b are used to reference identical parts. It will be understood by one of skill in the art that the two pumps 11aand 11bneed not be identical and that substantial variations are possible to one or the other within the scope of this invention. Pumps 11aand 11bare shown as the rotating axial piston type, although other designs could be used with minor modifications within the scope of this invention. For convenience, only certain elements of pump 11aand its related structure are described in detail herein. It will be understood that the corresponding structure of pump 11bis identical in the embodiments depicted and need not be similarly described.

[0019] Housing 12 forms two generally identical pump chambers or cavities 29aand 29band a gear chamber or cavity 30 formed therebetween, thus providing an integral housing for the two pumps 11aand 11b. A pair of end caps 16aand 16bare mounted on opposite ends of housing 12 and act to seal pump chambers 29aand 29b, and may be secured thereto by screws 22 or another means. A cover 23 is secured to the bottom of housing 12 to close gear chamber 30.

[0020] With regard to pump 11aon the left hand side of FIGS. 1, 2 and 3, it can be seen that a pump cylinder block 31acomprising a plurality of axial pistons 38ais mounted on running plate 37a, which may be used for additional strength and durability. Cylinder block 31acould also run directly on a surface formed on end cap 16a. The porting in end caps 16aand 16bcan be of the design shown in e.g., U.S. Pat. No. 6,332,393, the terms of which are incorporated by reference.

[0021] End cap 16aincludes hydraulic porting 26afor the hydraulic fluid. System ports 41aand 42bare formed on the external surface thereof. In the view shown in FIG. 1, plugs 43 are used to seal system ports 41a, 41b, 42band 42bfor shipping; in use the system ports would be connected to hoses or the like. As shown in the schematic depicted in FIG. 4, ports 41aand 42aare connected to motor 40awhile ports 41band 42bare connected to motor 40b. Motors 40aand 40bcould be wheel motors in a typical zero turn vehicle design; they could also be replaced with other hydraulic devices in other applications. A bypass 66aand 66bis provided for each pump 11aand 11bto permit, e.g., movement of the vehicle when it is not under power.

[0022] Pump 11ais of the cradle mounted swash plate design; as shown in FIG. 3, swash plate 32bis mounted in pump chamber 29aon cradle bearings 46amounted on the inner wall of housing 12. Pistons 38arun against swash bearing 33amounted in swash plate 32a. Trunnion arm 21ais engaged to a control block 45athat is engaged to swash plate 32a, so that rotation of trunnion arm 21acauses movement of swash plate 32bto the various stroked forward or reverse positions, or to the neutral position. While trunnion arms 21aand 21bare shown extending out of housing 12 on the same side as and thus parallel to input shaft 14, it will be understood that trunnion arms 21aand 21bcould be mounted on any side of housing 12, possibly requiring a corresponding change in the orientation of swash plates 32band 32b, respectively, and also possibly requiring a change in the orientation of end caps 16aand 16b, respectively. Trunnion arms 21aand 21bneed not be on the same side of housing 12. By way of example, if trunnion arm 21ais rotated 180° from the orientation shown, housing 12 would need to be modified, but the orientation of end cap 16awould not need to be changed. If, however, trunnion arm 21awas rotated 90° from the orientation shown, end cap 16awould also need to be similarly rotated, along with the proper housing modifications. It will also be understood that other types of swash plates 32band 32b, such as a trunnion mounted swash plate, could also be used.

[0023] A shown in FIG. 4, an external reservoir 68 is used for storing hydraulic fluid. The hydraulic fluid is pulled from reservoir 68 through filter 65 into charge inlets 47aand 47b, and hence to charge pumps 18aand 18b, respectively. Charged fluid is driven into charge gallery 49aand then to the porting in end cap 16a, and a charge relief 75ais provided to keep pressures within the normal operating range. Since in this embodiment pump chambers 29aand 29bare sealed from one another, a plurality of case drains 69aand 69bare provided to remove oil from pump chambers 29aand 29b, respectively. The separate case drains 69aand 69bmay be located in a variety of locations, such as end caps 16aand 16b. Check valves 67aand 67bare used to maintain the proper hydraulic flow within the end caps 16aand 16b. A pair of charge pressure relief valves 75aand 75bare connected to the porting for charge pumps 18aand 18b, respectively.

[0024] Input shaft 14 extends into housing 12; it can be driven by a prime mover (not shown) through a pulley, such as pulley 51 shown in FIG. 2, or some other means. Bevel gear 36 is mounted on input shaft 14 inside gear chamber 30 and is drivingly engaged to a second bevel gear 35 mounted on first pump shaft 27. Pump shaft 27 extends from gear chamber 30 into first pump chamber 29aand is engaged to and drivingly rotates pump cylinder block 31a. Bearing 44aprovides support within housing 12. Pump shaft 27 is joined to and drives shaft 28 through coupler 34, which may be of a known design using a powdered metal part with splines to interlock the two shafts 27 and 28, or a cut steel part with a broached inner diameter to form the interlock, or a similar design. Pump shaft 28 also extends from gear chamber 30 into pump chamber 29bwhere it engages and drivingly rotates pump cylinder block 31bin a similar manner. As shown in, e.g., FIG. 3, input shaft 14 is generally perpendicular to pump shafts 27 and 28 and extends out the side of housing 12 as opposed to the ends thereof, which provides the user with flexibility in the application.

[0025] As shown in, e.g., FIG. 3, input shaft 27 extends through end cap 16ainto charge housing 20ato drive charge pump 18a, which can be a gerotor style such as is shown or some other style of charge pump, such as a vane pump, geroller, gear pump or any other known design. End cap 16amay be secured to housing 12 by means of screws 24 or the like. The location of input shaft 14 on the side of housing 12 permits the location of charge pumps 18aand 18bon opposite ends of housing 12. Specifically, charge pump 18ais located within charge pump housing 20amounted on end cap 16a. A similar charge pump 18bmay be mounted in a similar manner in charge pump housing 20bon the other end of apparatus 10. It is possible that only one of the charge pumps would be required, depending on the application for which the pump apparatus 10 is to be used. Similarly, the output of one charge pump mounted on one end cap could be attached by means of internal or external hoses or integral passages to provide charge pressure to the other pump associated with the other end cap.

[0026] It will also be understood that these embodiments could include additional gear reduction. For example, in FIG. 3, a gear reduction could be used between bevel gear 36 on input shaft 14 and bevel gear 35 on pump 27. Furthermore, it will be understood that bevel gears 35 and 36 could be replaced with another means for creating a right angle turn of the rotational force, such as helical gears, a worm gear driving a spur gear and the like.

[0027] FIG. 5 shows a second embodiment of this invention, where like numerals indicate identical structure with previous figures. A pump apparatus 50 has a housing 52 which creates a gear chamber 56 and a first pump chamber 59aand a second pump chamber 59b. A case fluid passage 55ais formed in housing 52 to connect pump chamber 59aand gear chamber 56, and case fluid passage 55bsimilarly connects pump chamber 59bwith gear chamber 56, both to permit hydraulic oil to flow between the pump chambers 59aand 59band the gear chamber 56. Since both pump chambers 59aand 59band gear chamber 56 are hydraulically connected in this embodiment, a single case drain 69 to permit oil to flow to reservoir 68 can be formed anywhere in housing 52; if it is in the gear chamber 56, as shown in FIG. 6, it will assist in preventing contamination of pumps 11aand 11bwith debris from bevel gears 36, 35aand 35band assist in reduction of heat, as the warmer fluid from pumps 11aand 11bwill be carried to the center of the housing 52. It could, however, be formed elsewhere in the circuit depending on the application requirements. The use of a single case drain also reduces machining requirements and the number of fittings required.

[0028] In this second embodiment, input shaft 54 is driven by input pulley 51and extends through housing 52, and through cover 53, which includes bearing 57 therein to support shaft 54. Output pulley 58 may be attached to the end of shaft 54 to drive an auxiliary device such as a mower deck or other device. Cover 53 is strengthened to support bearing 57 used to rotatably support shaft 54 and the torque loads from output pulley 58.

[0029] It will be noted that using through shaft 54 as the input shaft precludes the use of a coupler to drive the two pump input shafts 63aand 63b. An alternative means of driving these shafts is shown in FIG. 5 where input shaft 54 has a first bevel gear 36 mounted thereon and drivingly engaged to a first driven bevel gear 35amounted on and driving first pump shaft 63aand a second driven bevel gear 35bwhich is similarly mounted on and driving second pump shaft 63b. Such an alternative arrangement could also be used with the first embodiment in place of coupler 34. A further benefit of this design is that pump shafts 63aand 63bcan be sized appropriately for the pumps; only input shaft 54 needs to be sized appropriately to handle the torque of both pumps 11aand 11bas well as the torque requirements of the auxiliary device attached to output pulley 58.

[0030] A third embodiment of this invention is shown in FIG. 7, which is similar in many ways to the embodiment as shown in FIG. 5. Pump apparatus 70 includes a housing 72 with cover 73 secured thereto. Input shaft 74 extends through housing 72 and cover 73, where it is supported by bearing 77, to extend out of the gear chamber 56 to drive auxiliary pump 78 through coupler 76, which also may be of the internal spline structure or other known structure. Auxiliary pump 78 could alternatively be driven directly by input shaft 74, thus eliminating the need for the coupler 76. Optional hardened washers 25 may be mounted adjacent to gears 35a, 35band 36 to provide support for such gears running against housing 72.

[0031] Auxiliary pump 78 is mounted in auxiliary pump housing 79 mounted on cover 73, and it can be used for driving external devices such as a deck lift or the like. The auxiliary out and auxiliary return are depicted schematically in FIG. 8. As with the embodiment depicted in FIG. 6, this embodiment requires only a single case drain 69 to reservoir 68.

[0032] Yet another embodiment is depicted in FIG. 9, which is structurally substantially identical to the embodiment shown in FIG. 1. FIG. 9 shows a pump apparatus 80, where the key differences with FIG. 1 are that pump shafts 87 and 88 extend out of charge pump housings 82band 82b, respectively, and input shaft 84 extends out of cover 83. A plurality of cooling fans 81aand 81bare mounted on pump shafts 87 and 88 respectively, while fan 81cmay be mounted on input shaft 84. It is unlikely, though possible, that all three fans 81a-cwould be needed for a single application.

[0033] One or more of fans 81a-cmay be used depending on the application needs and if 81aand 81bare placed in the orientation shown in FIG. 9, so as to move air in the same direction, they may cooperate to generate a draft across housing 12 and reduce airflow turbulence. The use of such fans can in certain applications eliminate the need for an oil cooler. The most advantageous arrangement of the fans will depend on how apparatus 80 is located with respect to, e.g., a vehicle engine or the like.

[0034] A fifth embodiment of this invention is shown in FIGS. 10-13, where pump apparatus 90 has a housing 92. This embodiment is similar in many ways to the previous embodiments and in particular the embodiment shown in FIGS. 5 and 7 in terms of the arrangements of those items using identical numerals. The key difference in this embodiment is the use of a single charge pump 98 driven by input shaft 94 rather than a pair of charge pumps driven by pump shafts 93aand 93b. Charge pump 98 is mounted in a housing 99 secured to cover 95.

[0035] As will be understood, a described arrangement requires porting to be formed in both cover 95 and housing 92 to permit charge oil flow to pump cylinder blocks 31aand 31b. It would also be understood that such porting could be formed externally, e.g., through hoses and the requisite fitting connecting charge pump 98 to end caps 96aand 96b. Input shaft 94 extends through cover 95 to drive charge pump 98. The input shaft may be further supported by bearing 77. An additional bearing 97 may also be provided.

[0036] As shown most clearly in FIGS. 10 and 11, housing 92 and cover 95 include a port 102 having a first leg 102bextending into the left side of housing 92 and into end cap 96a, and a second leg 102bextending opposite thereto and through the right side of housing 92 and into second end cap 96b. Charge inlet 104 is formed in cover 95 and connects charge pump 98 to reservoir 68, as shown in the schematic shown in FIG. 13. In the exemplary embodiment illustrated in FIGS. 10 and 11, the bearing 77 also serves to divides the charge inlet 104 from the port 102. End caps 96aand 96b, which are secured to housing 92 by screws 22 or other fastening means may be generally identical and thus only one will be described.

[0037] End cap 96ahas a pair of system ports 105, each of which has a corresponding poppet valve 106 connecting the kidneys 107 to the system ports 105. A screw type bypass 108 can be used with a bypass port 109 connecting the two sides of the hydraulic circuit to enable the user to place the unit into bypass. The key distinction from the prior embodiments is the use of single charge port 103, which may be drilled into end cap 96a, and which connects to port 102bto provide charge fluid from charge pump 98 to the hydraulic circuit of pump 11a.

[0038] As can be seen most clearly in FIG. 12, a mounting flange 110 can be formed on housing 92 to provide a means for securing the pump apparatus to a vehicle or the like.

[0039] FIG. 14 shows an alternative embodiment similar to that shown in FIG. 10, except that charge pump 112 is mounted on the inside of cover 111, and thus inside the fluid sump formed inside housing 92. Cover 113 is formed to mount not only charge pump 112 but also bearing 77 for input shaft 114. Porting similar to that shown in FIG. 11 will be formed in cover 111 to connect to ports 102band 102b.

[0040] It is to be understood that the above description of the invention should not be used to limit the invention, as other embodiments will be obvious to one skilled in the art. This invention should be read as limited by the scope of its claims only.