US3626816A

US3626816A - Hydraulic apparatus

Info

Publication number: US3626816A
Application number: US694717A
Authority: US
Inventors: Kenneth R Boydell
Original assignee: Dowty Technical Developments Ltd
Current assignee: Dowty Technical Developments Ltd
Priority date: 1967-02-23
Filing date: 1967-12-29
Publication date: 1971-12-14
Anticipated expiration: 1988-12-14
Also published as: GB1213662A

Abstract

A swashplate pump or motor comprising a rotary cylinder block having cylinders either parallel to or inclined to the rotation axis, a valve on which the block is arranged to rotate, an inclined or inclinable swashplate located adjacent to one end of the cylinder block and engageable by pistons in the cylinders either directly or through the medium of slippers whereby the pistons are reciprocated as the block rotates and a structural member formed in one piece and having a flat valve surface forming the valve on which the cylinder block is arranged to rotate, a cylindrical bearing surface surrounding part of the cylinder block to locate it for rotation and apertures to support one or more transverse shafts which locate the swashplate in position.

Description

United States Patent Kenneth R. Boydell Primary Examiner-William L. Freeh Attorney-Christensen, Sanborn & Matthews ABSTRACT: A swashplate pump or motor comprising a rotary cylinder block having cylinders either parallel to or inclined to the rotation axis, a valve on which the block is arranged to rotate, an inclined or inclinable swashplate located adjacent to one end of the cylinder block and engageable by pistons in the cylinders either directly or through the medium of slippers whereby the pistons are reciprocated as the block rotates and a structural member formed in one piece and having a flat valve surface forming the valve on which the cylinder block is arranged to rotate, a cylindrical bearing surface surrounding part of the cylinder block to locate it for rotation and apertures to support one or more transverse shafts which locate the swashplate in position.

[72] inventor Bredons Harwlck, Near Tewkesbury,

England [21] Appl. No. 694,717 [22] Filed Dec. 29, 1967 [45] Patented Dec. 14, 1971 [73] Assignee Dowty Technical Developments Limited Gloucester, England [32] Priorities Feb. 23, 1967 [33] Great Britain l I 8,709/67;

Sept. 26, 1967, Great Britain, No. 43,716/67 [54] HYDRAULIC APPARATUS 10 Claims, 2 Drawing Figs.

[52] U.S. Cl 91/504 [51] int. Cl F0lb 3/00, F04b 1/02, F04b 23/12 [50] Field of Search 103/162; 230/186; 91/504-506 [56] References Cited UNITED STATES PATENTS 2,875,701 3/1959 Ebert 103/162 Patented 1582; 14, 1911 sgsmgw" 2 Sheets-Sheet a FIG. 2.

INVLNIOR WW1 QZIW *mmu ATTORNEY HYDRAULIC APPARATUS FIELD OF THE INVENTION A reciprocating piston pump or motor having multiple pistons located in cylinders in a rotary cylinder block, the cylinders being either parallel to or inclined to the rotation axis.

DESCRIPTION OF PRIOR ART In a swashplate device it is known to mount the rotary cylinder block on a valve surface and to provide a cylindrical bearing around the cylinder block to locate it for rotation. It is conventional practice to arrange that the structural support arrangement which mounts the valve, the cylinder block, and the swashplate in their operational positions is formed in at least two parts detachably secured together, one of these parts being a valve block and the other a casing. The object of the present invention is to provide a simple construction of swashplate device in which the cost of manufacture and assembly is reduced to a minimum whilst at the same time ensuring an adequate working life for the device.

SUMMARY OF THE INVENTION In accordance with the present invention a swashplate device includes a structural member formed in one piece and having:

a. a flat valve surface on which the cylinder block is arranged to rotate b. a cylindrical bearing surface surrounding part of the cylinder block to locate it for rotation, and

c. apertures to support one or more transverse shafts which locate the swashplate.

A transverse shaft may extend completely across the casing between the apertures or may extend only partially across the casing from one or other aperture.

Within the scope of the invention the transverse shafts may comprise short shafts each of which passes through an aperture and engages the swashplate. A pair of such short shafts may pass through coaxial apertures such that the swashplate is inclinable about the common axis of the apertures.

Where only one shaft is inserted through the said apertures, the arrangement may be such that the swashplate is inclinable about the shaft to vary piston stroke.

The apertures may locate this shaft in an offset position relative to the cylinder block axis in order to ensure that the pistons exert a unidirectional moment on the swashplate.

The cylindrical bearing surface may be located adjacent to the swashplate so that the line of action of the side thrust acting on the pistons from the swashplate passes through the bearing.

The structural member may include a central aperture which extends through the valve surface to accommodate a drive shaft for the cylinder block.

The structural member may include fixing means by which the swashplate device is secured in operative position.

The steps of assembly of the swashplate device may comprise inserting the cylinder block through the cylindrical bearing surface to engage the valve surface, inserting the pistons into the cylinders, inserting the swashplate into position in the structural member to face the pistons and the cylinder block, and inserting a shaft or shafts through the apertures in the structural member to hold the swashplate in its operative position.

The or each shaft may be retained by a spring-clip device. Preferably the structural member is formed of an aluminum alloy and the cylinder block is formed of cast iron.

BRIEF DESCRIPTION OF THE DRAWINGS A pump in accordance with one embodiment of the invention will now be particularly described with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal cross section through the embodiment and FIG. 2 is a cross section taken on the line II--lI of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, the structural member of the pump is an aluminum alloy casting and comprises two integrally formed parts indicated as the valve 1 and the casing 7. The valve 1 has a flat valve surface 2 which contains a main high-pressure delivery port 3 of conventional kidney shape. A high-pressure screw connection 4 is provided in the valve 1 extending from the main port 3 for attachment of a suitable pipe connection. A plurality of screw-threaded apertures (not shown) extend from a face 6 of the valve opposite to the surface 2. These screw-threaded apertures form the means by which the whole pump may be secured by bolts to the wall of a liquid reservoir or other suitable mounting.

The hollow casing 7 is open ended at the end thereof opposite to the valve.

Within the casing 7 a cylinder block 8 of cast iron is located for rotation about the rotation axis AA. The cylinder block 8 includes a surface 9 resting on the valve surface 2. Within the block 8 there are five regularly spaced cylinders 11 all of whose axes are parallel to the rotation axis AA of the block. Each cylinder 1 1 includes a port 12 opening into the surface 9, the ports 12 being arranged to cooperate with the main port 3 during rotation of the cylinder block 8 about the axis AA. The ports 12 are arcuate in shape and each is arranged so that its center of pressure coincides effectively with the central axis of its cylinder 11. At a position remote from the surface 9, the cylinder block 8 is of enlarged diameter to support a cylindrical bearing surface 13 surrounding the cylinder block. The bearing surface 13 closely engages within a cooperating cylindrical bearing surface 14 formed in the interior of the casing 7.

Five passages 15 are formed within the cylinder block, one between each adjacent pair of cylinders. Each passage opens from the surface of the block remote from the valve surface 9 into an annular channel 16 defined between the casing 7, the cylinder block 8 and the

bearing surfaces

13 and 14. A recess 17 is formed in the valve surface 2, the inner portion of this recess cooperating with the cylinder ports 12 so as to form an inlet port whilst the outer part of this recess opens into the annular channel 16.

The casing 7 remote from the valve 1 includes a pair of integral lugs 18 each of which is bored transversely, thus producing a pair of spaced apertures 20. A cylindrical shaft 19 is fitted through the apertures 20. Between the lugs 18 a swash plate 21 is mounted on the shaft 19 by means of a cylindrical bore 22 extending through it. The swashplate 21 includes a flat swash surface 24 facing the cylinder block 8.

Within each cylinder 11 a piston 25 and a compression spring 26 are located, the spring acting to urge the piston outwardly from the cylinder. Each spring 26 reacts against a washer located in a recess 22 at the end of the cylinder adjacent to the surface 9. At its outer end each piston 25 is formed with a spherical socket 27 into which ball 28 is secured. The ball 28 is integrally connected to a slipper 29 engaging against the swash surface 24. A hydraulic passage 31 within the piston gives access to the socket 27 for lubrication and also connects to a passage in the ball which feeds liquid at pressure through a restrictor to a recess in the slipper surface in contact with the swash surface 24. The recess is of such size that the pressure loading applied to the slipper by the piston is almost completely balanced. Any other conventional system of hydraulic lubrication and/or balancing for the slipper may be employed.

A retaining plate 36 includes five apertures 37 engaged one on each slipper 29. Centrally, the retaining plate 36 reacts against a ball 39 carried by a pad 41 slidably mounted in a central bore 32 in the cylinder block. Within the bore 32 a compression spring 43 is located which reacts from a shoulder 44 in the block to urge the pad 41, the ball 39 and the plate 36 towards the swashplate. The spring thus serves to retain the slippers 29 in contact with the swash surface 24. The force exerted by the spring on the shoulder 44 will also serve to hold the cylinder block 8 against the valve surface 2 to ensure initial engagement.

A splined aperture 45 is provided centrally within the cylinder block to open into a comparatively large aperture 46 extending centrally through the valve 1. A drive shaft (not shown) may be inserted through the aperture 46 to engage the splined aperture 45 to drive the cylinder block. The engagement of the shaft in the splined aperture 45 should be loose to ensure that it can exert no side thrust on the block.

The pump as described is mounted for use on the wall of a liquid reservoir by means of screw-threaded bolts extending into the screw-threaded apertures in the valve. The drive shaft is arranged to extend vertically downwards through the wall of the reservoir to engage in the splines of aperture 45. An electric motor or other suitable driving means is located on the outside of the reservoir. Preferably the whole pump is located below liquid level in the reservoir. If the shaft passes through the wall of the reservoir below liquid level, a suitable seal is used.

The electric motor or other driving means normally provides a bearing to locate its drive shaft and in the present instance this bearing is sufficient to locate the drive shaft which extends into the aperture 45. In other words there is no need under most conditions to supply a special bearing housing for the shaft within the valve or other parts of the pump.

In operation, the cylinder block is driven by the drive shaft and the rotation of the block will cause reciprocation of the pistons in their cylinder by virtue of the fact that the slippers are held against the swash plate 24. As shown in the drawings the section through the valve is located at 90 to the section through the remainder of the pump in order to show the main port 3 and the recess 17. During rotation, liquid enters the pump through the open end of the casing and flows around and over the swashplate. This inlet liquid in the passages is induced by a centrifugal pumping action to flow to the annular channel 16 where slight pressure is generated. From channel 16 liquid enters the recess 17 and has access to the cylinder ports 12 during the periods when their pistons are moving outwardly from their cylinders. A vane may be provided internally of the casing in the channel 16 to interrupt rotary flow of liquid and thus to increase the pressure within the channel. The recess 17 may be made of gradually increasing depth in the direction of rotation of the cylinder block further to induce liquid to enter the recess 17. When cylinders connect with the main port 3 during block rotation and the pistons are urged into the cylinders, liquid is delivered at high pressure from the connection 4.

The fact that the swashplate is inclined causes considerable side thrust to be exerted on the cylinder block by the pistons being urged under pressure into their cylinders. For each piston undeR pressure the effective point at which the side thrust operates is the center of the ball joint. It is preferably arranged that the axial extent of the bearing surfaces is such that the lines of action of the lateral forces exerted through the ball joints may pass directly through the bearing surfaces without creating tilting movement on the cylinder block.

In assembly of the pump described, the cylinder block is initially entered into the open end of the casing to pass through the bearing surface 14 to engage the valve surface 2. The pistons and slippers are then entered into the cylinders and the swashplate 12 is held between the lugs whilst the shaft 19 is retained in position by spring clips 47 which engage in the grooves in the shaft 19 to act against washer 48 in turn engaging against lugs 18. Since, in use, the endwise thrust exerted on the shaft 19 is negligible, the spring clips are adequate to ensure that the shaft will remain in position. In order to adjust the angular displacement of the swashplate 18 about the shaft 19 a lever is attached in any convenient manner to the swashplate to extend to a control device.

In the assembly of the pump no screw-threaded locking devices need to be used thus reducing the cost of manufacture of the pump.

Whilst the pump described is intended to be capable of variable displacement by adjusting the angular setting of the swashplate 21, it is within the scope of the present invention to arrange that the swashplate 21 is of fixed inclination. This may be accomplished by forming the casing with stops to engage the swashplate after insertion of the shaft 19. Alternatively, a pair of shafts could extend transversely through two pairs of apertures in the casing to hold the swashplate at a fixed inclination.

The illustrated pump is intended for displacement adjustment from zero to maximum in one direction only so that discharge is always through the main port 3. The rotation axis of shaft 19 is offset from the rotation axis A-A to ensure that the control force exerted on the swashplate to retain it in its operative position is unidirectional.

The grade of aluminum allow selected for the structural member forming the casing and valve is so chosen that the easing is of substantial strength to cater for the intended operating pressures of the pump. The cast iron of the block and the aluminum of the structural member together form a good bearing combination and the valve surface 2 and the cylindrical bearing surface 14 will both have a good working life.

Within the broad scope of the invention the materials of which the cylinder block and structural member are formed may be of any metals or alloys having suitable bearing properties and adequate structural strength.

Whilst the described embodiment is a pump, a motor is also within the scope of the invention. For use as a motor, the illustrated embodiment would be modified by arranging that the high-pressure inlet is the connection 4 and preferably by arranging that liquid from the recess 17 can leave the casing by means other than passages 15.

I claim:

1. In a swashplate device comprising a rotary cylinder block having cylinders therein, pistons in the cylinders projecting from one end of the block, a tiltable swashplate adjacent to said one end of the block reacting on the pistons to cause reciprocation thereof during block rotation, trunnion means supporting the swashplate for tilting movement, a valve having a flat valve surface adapted to engage the opposite end surface of the block to the said one end, cylinder ports opening into the said opposite end surface, supply and return ports in said flat valve surface for cooperation with the cylinder ports during block rotation, and a radial thrust bearing surrounding the cylinder block to react the side thrust exerted on the block by the swashplate, the improvement comprising a structural member formed in one piece and having (a) the flat valve surface formed thereon, (b) an internal cylindrical surface formed therein forming said radial thrust bearing, (c) bearing apertures to engage the said trunnion means, and (d) an opening through which the cylinder block may be inserted to enter its operative position on the flat valve surface and within the said radial thrust bearing, the cylinder block including passages extending within the block between the said one end of the block and the periphery of the block intermediate the valve surface and the radial thrust bearing, and the structural member forming with the periphery of the cylinder block and the radial thrust bearing an annular channel to which the supply port is connected.

2. A swashplate device as claimed in claim 1, wherein the trunnions comprise a single shaft passing through the said bearing apertures and through an aperture in the swashplate, said shaft retaining the swashplate, cylinder block and pistons in their operative positions.

3. A swashplate device as claimed in claim 1, wherein the structural member includes a central aperture extending through the central portion of the valve surface and the cylinder block includes a splined central recess such that a driving shaft may extend through the central aperture into the recess.

4. A swashplate device as claimed in claim 1, wherein the structural member is formed of an aluminum alloy and the cylinder block is formed of iron.

5. A swashplate device as claimed in claim 2 and including spring means reacting between the cylinder block and the swashplate to hold the block against the valve surface.

6. A swashplate device as claimed in claim 5, wherein the spring means includes springs in the cylinders reacting through the pistons onto the swashplate.

7. In a pump or or motor, an open-ended tubular casing having a single, monolithic cast body construction from one end thereof to the other, and a swashplate device comprising a cylindrically surfaced, piston-equipped rotary cylinder block and a laterally trunnioned swashplate which are inserted into the casing in the aforesaid order through the one end thereof, and cooperatively tandemly arranged to cause reciprocation of the pistons when the block is rotated by a drive shaft inrerted into the casing through the other end thereof, said swashplate being openly exposed to the outside of the casing, in the one end opening thereof, and said casing having a stepped inner peripheral body contour defining: (l) a flat, ported, radially extending valve surface in operative sliding engagement with the forward end of the block, to supply and return fluid to and from the cylinders in the block during the rotation thereof, (2) a cylindrical, longitudinally extending bearing surface in operative sliding engagement with the cylindrical surface of the block, to react the side thrust exerted on the block by the swashplate, and (3) a pair of oppositely disposed recesses in the one end portion thereof, to support the swashplate trunnions therein.

8. The pump or motor according to claim 7 wherein the swashplate is transversely recessed to receive the trunnions, and the casing recesses take the form of apertures having the trunnions slidably inserted therethrough into the plate.

9. The pump or motor according to claim 7 wherein the block is spaced apart from the inner peripheral body surfaces of the casing between the aforesaid valve and bearing surfaces thereof, and there are passages in the casing and block interconnecting the aforesaid space with one port of the valve surface and the aforesaid one end opening of the casing, respectively, to feed the fluid to or from the cylinders in the block.

10. The pump or motor according to claim 7 wherein the forward end of the block has an axial recess therein which is openly exposed to the outside of the casing through the other end opening thereof, and detachably engageable by the drive shaft when the latter is inserted therein.

l l i i l UNITED STATES PATENT OFFICE CERTEFICATE OF CORRECTION 14 1971 Patent No. 3 Dated December I KENNETH R. BOYDELL Inventor(s) It is eertified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Specificatonf Col.- 3,, line 57, delete "undeR" and insert therefor -under-. Col. 3, line 67, after 'shaft 19'' insert thefollowing is passed through the trunnion bearings. As shown in FIG. 2

the shaft l9-.

Signed and sealed this 20th day of June 1972.

Attest:

EDWARD M.FLETCHER, JR. i 7 ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

7. In a pump or motor, an open-ended tubular casing having a single, monolithic cast body construction from one end thereof to the other, and a swashplate device comprising a cylindrically surfaced, piston-equipped rotary cylinder block and a laterally trunnioned swashplate which are inserted into the casing in the aforesaid order through the one end thereof, and cooperatively tandemly arranged to cause reciprocation of the pistons when the block is rotated by a drive shaft inserted into the casing through the other end thereof, said swashplate being openly exposed to the outside of the casing, in the one end opening thereof, and said casing having a stepped inner peripheral body contour defining: (1) a flat, ported, radially extending valve surface in operative sliding engagement with the forward end of the block, to supply and return fluid to and from the cylinders in the block during the rotation thereof, (2) a cylindrical, longitudinally extending bearing surface in operative sliding engagement with the cylindrical surface of the block, to react the side thrust exerted on the block by the swashplate, and (3) a pair of oppositely disposed recesses in the one end portion thereof, to support the swashplate trunnions therein.