TANDEM AXIAL PISTON PUMP WITH SHARED CYLINDER BLOCK
A tandem axial piston pump having a common cylinder block. A first axial piston pump includes a first set of pistons arranged in a parallel, circular array and configured to reciprocate in response to rotation about a central axis. A second axial piston pump includes a second set of pistons arranged in a parallel, circular array and configured to reciprocate as they rotate about the central axis. A common drive shaft extends along the central axis, both the first and second sets of pistons being configured to rotate with the common drive shaft. Both the first and second sets of pistons are configured to reciprocate within corresponding separate first and second sets of cylinder bores of the common cylinder block.
The present invention relates to axial piston pumps. More particularly, the invention relates to tandem axial piston pumps. Such hydraulic pumps can be found in the traction drive systems of skid steer construction vehicles and the like. The tandem axial piston pump will include two independently operable axial piston pump assemblies enclosed within a common housing.
SUMMARYIn one aspect, the invention provides a tandem axial piston pump. A first axial piston pump includes a first set of pistons arranged in a parallel, circular array and configured to reciprocate in response to rotation about a central axis. A second axial piston pump includes a second set of pistons arranged in a parallel, circular array and configured to reciprocate as they rotate about the central axis. A common drive shaft extends along the central axis, both the first and second sets of pistons being configured to rotate with the common drive shaft. Both the first and second sets of pistons are configured to reciprocate within corresponding separate first and second sets of cylinder bores of a common cylinder block.
In another aspect, the invention provides a tandem axial piston pump. A drive shaft defines an axis. A first set of pistons are arranged in parallel with the axis in a circular array and rotatable about the axis by the drive shaft. A second set of pistons are arranged in parallel with the axis in a circular array and rotatable about the axis by the drive shaft. A first swash plate is coupled to a base end of each of the pistons of the first set. The first swash plate defines a cam angle with respect to the axis, and the cam angle defines a stoke distance through which each of the pistons of the first set travels back-and-forth upon a rotation about the axis. A second swash plate is coupled to a base end of each of the pistons of the second set. The second swash plate defines a cam angle with respect to the axis, and the cam angle defines a stoke distance through which each of the pistons of the second set travels back-and-forth upon a rotation about the axis. A cylinder block has a first set of cylinder bores receiving the first set of pistons from a first end of the cylinder block and a second set of cylinder bores receiving the second set of pistons from a second end of the cylinder block, opposite the first end.
Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways.
Each piston 24 has an inner working end facing the central plane P and an outer drive end. The drive end of each piston 24 has a rounded shape received in a corresponding piston shoe 60. The piston shoes 60 of each set of pistons 24 are collectively retained by a shoe plate 62 to maintain the parallel spaced arrangement of the pistons 24 within each set. Directly outside the piston shoes 60 in the axial direction on each pump unit is a swash plate 66. The swash plates 66 are movable to tilt relative to the central axis A in order to vary the stroke of the corresponding pistons 24. The swash plates 66 are illustrated in a zero or neutral state in which the swash plates 66 are each arranged exactly perpendicular to the central axis A such that the pistons 24 do not stroke at all when the pistons 24 and the cylinder block 28 are rotated about the central axis A. When one of the swash plates 66 is angled away from the neutral state, each piston 24 of the corresponding pump unit reciprocates to complete one back-and-forth pumping stroke within the corresponding bore 30 upon each full rotation of the cylinder block 28 about the central axis A. The linear stroke of the pistons 24 of a particular set is varied by varying the angle of the corresponding swash plate 66. The independence of the displacement between the two pump units, which rotate together, is achieved by independent control of the two swash plates 66.
A radial bore 70 or connector port is provided through an outer cylindrical surface 72 of the cylinder block 28 for each of the cylinder bores 30 of each of the two sets. Each radial bore 70 extends inward from the outer cylindrical surface 72 to intersect with the corresponding cylinder bore 30 to establish fluid communication therewith. The radial bores 70 provide fluid communication with the port block 48 via one or more distribution rings 76 as discussed further below. Although shown as two separate components in the illustrated construction, the features of the two distribution rings 76 can alternately be incorporated into a single distribution ring. Each of the distribution rings 76 is fixed to the bore 50 in the port block 48. For example, the distribution rings 76 can be press-fit into the bore 50. The cylinder block 28, particularly the outer cylindrical surface 72, is provided in tight sliding relationship with the interior of each of the distribution rings 76. Thus, as the cylinder block 28 rotates within the distribution rings 76, the radial bores 70 are brought into and out of fluid communication with a pair of slots 80, 82 provided in each distribution ring 76. The two slots 80, 82 in each distribution ring 76 are circumferentially spaced apart, and may be diametrically opposed. Each of the slots 80, 82 may be about 90 arc degrees long, or more. The first slot 80 is a pickup or inlet slot which is in permanent fluid communication with a corresponding inlet port 86 of the port block 48, via a connecting passage through the port block 48. The second slot 82 is a distribution or outlet slot which is in permanent fluid communication with a corresponding outlet port 88 of the port block 48, via a connecting passage through the port block 48. Because the pump 20 includes two pump units, the port block 48 includes two separate pairs of the inlet and outlet ports 86, 88 corresponding to the two pump units.
When the swash plate 66 of one of the pump units is angled from the illustrated neutral position, each piston 24 of the corresponding pump unit moves in a retracting direction with respect to the corresponding cylinder bore 30 over a rotational range in which the corresponding radial bore 70 is in communication with the corresponding inlet slot 80, and thereby, the inlet port 86. As such, fluid is drawn into the cylinder bore 30 through the inlet port 86, the inlet slot 80, and the radial bore 70. Further rotation of the cylinder block 28 causes fluid communication to cease between the cylinder bore 30 and the inlet slot 80, and even further rotation of the cylinder block 28 causes fluid communication to be established between the cylinder bore 30 and the outlet slot 82. Due to the angle of the swash plate 66, the piston 24 extends into the cylinder bore 30 over a rotational range in which the corresponding radial bore 70 is in communication with the outlet slot 82. As such, the fluid previously drawn into the cylinder bore 30 from the inlet port 86 is pumped out of the pump 20 from the cylinder bore 30 through the radial bore 70, the outlet slot 82, and the outlet port 88. Each sequential piston 24 of the given pump unit follows the same sequence during rotation of the cylinder block 28, and if the swash plate 66 of the other pump unit is angled, a similar pumping method occurs with the other set of pistons 24. Although not shown in the drawings, a separate mechanism (e.g., a servo motor) may be coupled to the respective swash plates 66 to control the swash angles and thus, the pump displacement. While not necessarily limited to one fixed speed, the drive shaft 34 may be rotated by a separate drive element (e.g., an electric motor) at a constant speed during operation of the pump 20.
Rather than having separate housings and end flanges on each end, the pump 120 is provided with a two-piece case consisting of a first case portion 143A and a second case portion 143B. The case portions 143A, 143B can be mated to one another (e.g., by a plurality of fasteners or other means, not shown) in a direction parallel to the axis A. Both case portions 143A, 143B generally have a cup shape which surrounds at least a portion of the pump internals both radially and on one axial end. Furthermore, each case portion 143A, 143B includes a control bore 145A, 145B for receiving a servo piston or stroking piston (not shown) which manipulates the corresponding swash plate 166A, 166B, a drive portion 167 of which is positioned in the corresponding control bore 145A, 145B. Similar to the pump 20 of
The tandem axial piston pump 120 also does without a separate central port block, instead providing both the inlet ports 186 and the outlet ports 188 for both pump units in the second case portion 143B. The inlet ports 186 for both pump units can be located on a first side of the second case portion 143B and the outlet ports 188 for both pump units can be located on a second opposite side of the second case portion 143B, although other arrangements are optional.
In order to further limit an axial length of the cylinder block 128 to reduce the overall packaging size of the tandem axial piston pump 120, the arrangement of the cylinder bores 130 (and thus, the corresponding pistons 124) is altered from that of the pump 20 of
Similar to the pump 20 of
Various features and advantages of the invention are set forth in the following claims.
Claims
1. A tandem axial piston pump comprising:
- a first axial piston pump including a first set of pistons arranged in a parallel, circular array and configured to reciprocate in response to rotation about a central axis;
- a second axial piston pump including a second set of pistons arranged in a parallel, circular array and configured to reciprocate as they rotate about the central axis; and
- a common drive shaft extending along the central axis, wherein both the first and second sets of pistons are configured to rotate with the common drive shaft;
- wherein both the first and second sets of pistons are configured to reciprocate within corresponding separate first and second sets of cylinder bores of a common cylinder block.
2. The tandem axial piston pump of claim 1, wherein the corresponding sets of cylinder bores include a first set of cylinder bores extending from a first axial end of the cylinder block and a second set of cylinder bores extending from a second axial end of the cylinder block.
3. The tandem axial piston pump of claim 2, further comprising
- a first swash plate coupled to a base end of each of the pistons of the first set, the first swash plate defining a cam angle with respect to the central axis, the cam angle defining a stoke distance through which each of the pistons of the first set travels back-and-forth upon a rotation about the central axis; and
- a second swash plate coupled to a base end of each of the pistons of the second set, the second swash plate defining a cam angle with respect to the central axis, the cam angle defining a stoke distance through which each of the pistons of the second set travels back-and-forth upon a rotation about the central axis.
4. The tandem axial piston pump of claim 1, wherein the cylinder block has an outer cylindrical surface including a respective radial port corresponding to and establishing fluid communication with each of the cylinder bores of the first and second sets through a side wall of each corresponding cylinder bore, wherein all of the radial ports corresponding to the cylinder bores of the first set are arranged at a first axial position, and all of the radial ports corresponding to the cylinder bores of the second set are arranged at a second axial position.
5. The tandem axial piston pump of claim 1, further comprising at least one distribution ring positioned around the cylinder block and having
- a first inlet slot at the first axial position,
- a first outlet slot at the first axial position and offset circumferentially from the first inlet slot,
- a second inlet slot at the second axial position, and
- a second outlet slot at the second axial position and offset circumferentially from the second inlet slot.
6. The tandem axial piston pump of claim 5, further comprising a port block having a bore receiving the at least one distribution ring, the port block configured to direct a fluid supply flow to the first and second axial piston pumps via the first and second inlet slots and to receive a pumped fluid flow from the first and second axial piston pumps via the first and second outlet slots.
7. The tandem axial piston pump of claim 6, wherein the at least one distribution ring is press-fit into the bore of the port block with the first and second inlet slots in fluid communication with at least one inlet port of the port block, and the first and second outlet slots in fluid communication with at least one outlet port of the port block.
8. The tandem axial piston pump of claim 7, wherein the port block includes separate inlet ports and separate outlet ports for each of the first and second inlet slots and each of the first and second outlet slots.
9. The tandem axial piston pump of claim 5, wherein the first inlet slot and the first outlet slot are formed in a first distribution ring, and the second inlet slot and the second outlet slot are formed in a separate second distribution ring.
10. The tandem axial piston pump of claim 1, wherein the cylinder block is integrally formed as a single, monolithic piece.
11. A tandem axial piston pump comprising:
- a drive shaft defining an axis;
- a first set of pistons arranged in parallel with the axis in a circular array and rotatable about the axis by the drive shaft;
- a second set of pistons arranged in parallel with the axis in a circular array and rotatable about the axis by the drive shaft;
- a first swash plate coupled to a base end of each of the pistons of the first set, the first swash plate defining a cam angle with respect to the axis, the cam angle defining a stoke distance through which each of the pistons of the first set travels back-and-forth upon a rotation about the axis;
- a second swash plate coupled to a base end of each of the pistons of the second set, the second swash plate defining a cam angle with respect to the axis, the cam angle defining a stoke distance through which each of the pistons of the second set travels back-and-forth upon a rotation about the axis; and
- a cylinder block having a first set of cylinder bores receiving the first set of pistons from a first end of the cylinder block and a second set of cylinder bores receiving the second set of pistons from a second end of the cylinder block opposite the first end.
12. The tandem axial piston pump of claim 11, wherein the first and second swash plates are operable to vary the respective cam angles independently of each other such that the first set of pistons along with the first set of cylinder bores define a first axial piston pump having a displacement variable independently of a second axial piston pump defined by the second set of pistons along with the second set of cylinder bores.
13. The tandem axial piston pump of claim 11, wherein the cylinder block has an outer cylindrical surface including a respective radial port corresponding to and establishing fluid communication with each of the cylinder bores of the first and second sets through a side wall of each corresponding cylinder bore, wherein all of the radial ports corresponding to the cylinder bores of the first set are arranged at a first axial position, and all of the radial ports corresponding to the cylinder bores of the second set are arranged at a second axial position.
14. The tandem axial piston pump of claim 11, further comprising at least one distribution ring positioned around the cylinder block and having
- a first inlet slot at the first axial position,
- a first outlet slot at the first axial position and offset circumferentially from the first inlet slot,
- a second inlet slot at the second axial position, and
- a second outlet slot at the second axial position and offset circumferentially from the second inlet slot.
15. The tandem axial piston pump of claim 14, further comprising a port block having a bore receiving the at least one distribution ring, the port block configured to direct a fluid supply flow to the first and second axial piston pumps via the first and second inlet slots and to receive a pumped fluid flow from the first and second axial piston pumps via the first and second outlet slots.
16. The tandem axial piston pump of claim 15, wherein the at least one distribution ring is press-fit into the bore of the port block with the first and second inlet slots in fluid communication with at least one inlet port of the port block, and the first and second outlet slots in fluid communication with at least one outlet port of the port block.
17. The tandem axial piston pump of claim 16, wherein the port block includes separate inlet ports and separate outlet ports for each of the first and second inlet slots and each of the first and second outlet slots.
18. The tandem axial piston pump of claim 14, wherein the first inlet slot and the first outlet slot are formed in a first distribution ring, and the second inlet slot and the second outlet slot are formed in a separate second distribution ring.
19. The tandem axial piston pump of claim 11, wherein the cylinder block is integrally formed as a single, monolithic piece.
Type: Application
Filed: Nov 6, 2014
Publication Date: May 12, 2016
Inventors: Michael Weathersbee (Ware Shoals, SC), Richard Kalocy (Mauldin, SC), Jonathan Stewart (Greenville, SC)
Application Number: 14/534,483