US3612725A

US3612725A - Hydraulic apparatus

Info

Publication number: US3612725A
Application number: US690369A
Authority: US
Inventors: Peter Spence
Original assignee: Dowty Technical Developments Ltd
Current assignee: Dowty Technical Developments Ltd
Priority date: 1966-12-14
Filing date: 1967-12-08
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12
Also published as: DE1653417B2; GB1200180A; JPS5212402B1; DE1653417A1

Abstract

A swashplate pump comprising a rotary cylinder block having cylinders disposed parallel or inclined to the rotation axis, valve means cooperating with the cylinder block during rotation, swashplate means located adjacent to one end of the cylinder block for causing reciprocation of pistons in the cylinders during block rotation, passages or vanes or other hydrokinetic pumping means formed in or on the cylinder block, a casing surrounding the swashplate means and the cylinder block at least in part and a hydraulic inlet to the casing such that during rotation of the cylinder block liquid is kinetically pumped by the kinetic pumping means on the cylinder block to pass initially over the swashplate and then to and through the kinetic pumping means for delivery to the valve inlet for pumping by the pistons in the cylinder block.

Description

United States Patent [54] HYDRAULIC APPARATUS 6 Claims, 1 Drawing Fig.

[52] US. Cl 417/203 [51] lnt.Cl .F04b 23/12 [50] Field of Search... 230/208,

[56] References Cited UNITED STATES PATENTS 1,866,398 7/1932 Craig 103/202 X 2,453,266 1 H1948 Rockwell 103/162 2,858,771 11/1958 Cornelius 103/202 2,392,543 1/1946 Mercier... 103/5 2,608,159 8/1952 Born 103/162 2,646,754 7/1953 Overbeke 103/161 Primary Examiner-William L. Freeh AttorneyChristensen & Sanbom ABSTRACT: A swashplate pump comprising a rotary cylinder block having cylinders disposed parallel or inclined to the rotation axis, valve means cooperating with the cylinder block during rotation, swashplate means located adjacent to one end of the cylinder block for causing reciprocation of pistons in the cylinders during block rotation, passages or vanes or other hydrokinetic pumping means formed in or on the cylinder block, a casing surrounding the swashplate means and the cylinder block at least in part and a hydraulic inlet to the casing such that during rotation of the cylinder block liquid is kinetically pumped by the kinetic pumping means on the cylinder block to pass initially over the swashplate and then to and through the kinetic pumping means for delivery to the valve inlet for pumping by the pistons in the cylinder block.

PATENTEUUET 1 2 IEWI INVLN1OR ATTORNEY HYDRAULIC APPARATUS FIELD OF THE INVENTION This invention relates to hydraulic pumps of the kind comprising a rotary cylinder block having cylinders disposed parallel or inclined to the rotation axis, valve means cooperating with the cylinder block during rotation, and swashplate means located adjacent to one end of the cylinder block for causing reciprocation of pistons in the cylinders during block rotation. This kind of pump will hereinafter be referred to as a swashplate pump.

DESCRIPTION OF THE PRIOR ART It has been proposed in swashplate pumps to arrange that the cylinder block includes kinetic pumping passages to give kinetic pumping to some or all of the liquid entering the cylinders in the cylinder block. However in these prior art proposals the kinetic pumping effected by the cylinder block operates on the liquid before the liquid makes contact with the swashplate. The kinetic pumping action causes temperature rise of the pumped liquid which then may not effect efficient cooling and lubrication of the swashplate.

SUMMARY OF THE INVENTION In accordance with the present invention a swashplate pump includes a casing surrounding the swashplate means and the cylinder block, hydrokinetic pumping means formed on or in the cylinder block, a liquid inlet to the casing arranged so that liquid entering through the inlet will flow over the swashplate means to and through the said hydrokinetic pumping means into a delivery region from which liquid enters the said valve means.

The hydrokinetic pumping means may comprise passages formed within the cylinder block.

The passages may include radial and/or skewed surfaces so that hydrokinetic pumping is either by centrifugal flow or axial flow or a combination of both.

A bearing around the block may locate the block for rotation in the casing and the bearing may conveniently form a seal acting to isolate at least in part the delivery region from the inlet.

BRIEF DESCRIPTION OF THE DRAWING One embodiment of the invention will be described with referenceto the accompanying cross-sectional drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT In this drawing the casing l is conveniently secured by bolt or other means to a valve block 2. The casing surrounds a rotary cylinder block 3 which is mounted for rotation by means of a large diameter plain bearing 4 which engages between the block and the interior of the casing l. The location of the bearing 4 is at the end of the cylinder block remote from the valve block 2. Within the cylinder block 3 a number of cylinders 5 are provided each parallel to the axis of block rotation and equally spaced around the rotation axis. In the illustrated embodiment there are five cylinders but in practice any number greater than three may be used. Each cylinder 5 contains a piston 6 and spring 7 which acts on the piston to urge it outwardly from the cylinder. The surface 8 of the cylinder block is a plane surface set at right angles to the block rotation axis and it includes a port 9 for each of the cylinders 5. The surface 8 cooperates with a flat surface 10 of a valve plate 11 mounted on the valve block 2. The valve plate 11 includes a pair of kidney-shaped ports 12 and 13 with which the cylinder ports 9 cooperate during cylinder block rotation. The port 12 is the inlet port and the port 13 is the pressure delivery port. Port 13 is connected within the valve block 2 to a screw connection 14 by which pressure liquid leaves the pump. The port 12 is formed by a cutaway portion of the valve plate extending inwardly from its periphery, this cutaway portion being located over a recess 30 in the valve block which opens to the interior of the casing l. The valve plate 11 may be retained in its operative position by a plurality of dowel pins 20.

The inlet 15 for the pump is formed in the casing at the end thereof remote from the valve block 2. This may be a screw connection or the whole end of the casing may be open where the pump is intended for operation submerged in liquid in a reservoir. I

The casing 1 also surrounds a swashplate 16 which is mounted in an open chamber in the remote end portion of the casing, on suitable trunnions for adjustment about an axis 17 which extends perpendicularly to the plane of the drawing. Angular adjustment of the swashplate may be effected by any conventional means. The swashplate 16 has a plane swash surface 18 facing the cylinder block. A slipper I9 is fitted by a ball joint 21 to the end of each piston 6 for engagement with the swash surface 18. The slippers 19 may be fed with hydraulic liquid in conventional manner from the associated cylinders in order to provide a hydrostatic bearing between the slipper and the swash surface. Within a central bore 21 in the cylinder block a spring 22 is located which presses outwardly through a ball 23 onto a retainer plate 24 suitably recessed to v engage against the slippers 19 to hold them in contact with the swash surface 18. The principal function served by spring 22 and retainer plate 24 is to urge the pistons outwardly from their cylinders during one-half of each cylinder block revolution. The spring within each cylinder will also help to urge the pistons outwardly. v

A pair of

adjustable stops

25 and 26 within the casing I are provided to engage the swashplate 16 to determine its limits of angular adjustment about the axis 17.

A plurality of passages 27 are provided within the cylinder block, one between each adjacent pair of cylinders. These passages open into the end of the cylinder block adjacent the swashplate l8 and extend back to open at the side of the cylinder block, into an annular space 28 defined between the casing, the cylinder block, the bearing 4 and the valve block. This space is the delivery region. A vane 39 formed on the interior surface of the casing projects in the space 28 to reduce rotary flow of liquid around the space 28. The walls of the passages 27 form kinetic pumping surfaces which have radial portions to pump liquid by centrifugal action from the inlet 15 over the swashplate l6 and into the space 28. It is equally within the scope of this invention that the passages 27 could be skewed relatively to the axis of block rotation to effect axial flow kinetic pumping.

Rotational drive is supplied to the cylinder block 3 through the medium of a drive shaft 29 having a splined connection 31 within the block 3. The shaft 29 is supported within a sleeve 32 carried within

bearings

33 and 34 in the valve block 2. A seal 35 cooperates with the sleeve 32 to prevent escape of liquid. A hollow space 36 is formed around the sleeve 32 and this is connected by a passage 37 with the recess 30. The passage 37 will ensure that high-pressure liquid escaping from the inner edge of the surfaces 8 and 11 is fed back to the inlet port 12 thus preventing any substantial pressure from acting on the seal 35. Such liquid will also have access to the

bearings

33 and 34 and ensure that they are adequately lubricated.

In operation of the described embodiment rotary driving power is supplied to the shaft 29 to rotate the cylinder block 3. During such rotation the slippers will be held in contact with the swashplate l8 and thus the pistons will be forced to reciprocate within their cylinders. The driving direction is such that when the pistons are moving out of their cylinders the associated cylinder ports 9 are in connection with the inlet port 12. When the pistons are moving into their cylinders the associated cylinder ports 9 are in connection with the delivery port 13. The cross section through the valve block 2 has been deliberately taken on a plane at right angles to the cross section through the cylinder block and swashplate in order that the ports 12 and 13 may be shown in the drawings. Liquid enters the pump through the inlet 15 and rotation of the cylinder block and the passages 27 gives a small pressure rise from the inlet 15 into the delivery space 28. The vane 39 reduces flow of liquid around the delivery space and will help to increase the small presure rise generated within the space 28. From the space 28 liquid has direct access into the inlet port 12 both through its opening in the edge of plate 11 and through the recess 30 and thus to flow into the cylinders whose pistons are moving outwardly. The flow of liquid induced by the passages 27 will pass over the swashplate at the temperature at which it enters the inlet 15 and will ensure adequate lubrication and cooling of the slippers and swashplate. The bearing 4 around the end of the cylinder block 3 remote from the valve block 2 is so positioned that the side thrust exerted by the slippers on the pistons will pass substantially directly through the bearing 4 and thus will not generate any substantial tipping moment on the cylinder block 3. The bearing 4 forms a seal between the inlet 15 and the space 28.

It will be appreciated that many other constructions are possible within the scope of the present invention. For example it is possible for the cylinder barrel to be completely supported for rotation by a shaft extending through the barrel and located in bearings at either end of the barrel. In such a case appropriate sealing means would be provided around the periphery of the cylinder block to isolate the space from the inlet 15. In the described embodiment the pumping surfaces are formed by the walls of passages 27 passing through the cylinder block. It is within the scope of the invention for example that such pumping surfaces should be formed as the surfaces of vanes located around the periphery of the cylinder block. In the previously mentioned modification in which the cylinder block is completely supported on a shaft such vanes could rotate in closely spaced relation with the interior of the casing l to fonn effectively a seal with the casing to isolate the delivery space from the inlet 15. Where vanes are provided around the cylinder block they will preferably be skewed relative to the block rotation axis so that kinetic pumping is axial flow pumping rather than centrifugal pumping.

lclaim:

1. In a swashplate pump comprising a rotary cylinder block having cylinders disposed parallel or inclined to the rotation .axis, pistons in the cylinders, valve means cooperating with the cylinder block during rotation, and swashplate means located adjacent to one end of the cylinder block for causing reciprocation of the pistons in the cylinders during block rotation, the improvement comprising a casing surrounding the swashplate means and the cylinder block, and means for supplying liquid to the valve means including hydrokinetic pumping means fonned on or in the cylinder block, and a liquid inlet into the casing arranged so that liquid entering through the inlet flows over the swashplate means en route to and through the said hydrokinetic pumping means, into a delivery region from which liquid enters the said valve means.

2. A swashplate pump as claimed in claim 1 including a bearing around the cylinder block to locate the cylinder block for rotation in the casing, the said bearing acting to isolate at least in part the delivery region from the inlet.

3. A swashplate pump as claimed in claim 2 wherein the bearing is located to resist substantially all side thrust exerted on the cylinder block by the swashplate means.

4. A swashplate pump as claimed in claim 2 wherein the delivery region is defined between the interior of the casing, the periphery of the cylinder block, and the bearing around the cylinder block.

5. The swashplate pump according to claim 1 wherein the casing has a chamber in one end portion thereof, which is in open communication with the liquid inlet, and the swashplate means is mounted in the chamber so as to be directly exposed to the liquid flowing into the chamber from the inlet.

6. The swashplate pump according to claim 5 wherein the valve means has a port therein for supplying liquid to the cylinders during block rotation, and the hydrokinetic pumping means includes a passage which interconnects the aforesaid liquid supply port with the chamber, at a point on the opposite side of the swashplate means from the liquid inlet, so that the liquid from the inlet flows directly into the passage, and thence to the supply port, after flowing over the swashplate means.

Claims

1. In a swashplate pump comprising a rotary cylinder block having cylinders disposed parallel or inclined to the rotation axis, pistons in the cylinders, valve means cooperating with the cylinder block during rotation, and swashplate mEans located adjacent to one end of the cylinder block for causing reciprocation of the pistons in the cylinders during block rotation, the improvement comprising a casing surrounding the swashplate means and the cylinder block, and means for supplying liquid to the valve means including hydrokinetic pumping means formed on or in the cylinder block, and a liquid inlet into the casing arranged so that liquid entering through the inlet flows over the swashplate means en route to and through the said hydrokinetic pumping means, into a delivery region from which liquid enters the said valve means.