US3460483A

US3460483A - Port plates for hydraulic reciprocating pumps and motors

Info

Publication number: US3460483A
Application number: US667902A
Authority: US
Inventors: Harry Simister Bottoms
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1967-09-15
Filing date: 1967-09-15
Publication date: 1969-08-12
Anticipated expiration: 1986-08-12

Description

Aug. 12, 1969 H s. BOTTOMS PORT PLATES FOR HYDRAULIC RECIPROCATING PUMPS AND MOTORS Filed Sept. 15, 1967 2 Sheets-Sheet 1 A g 1969 H. s. BOTTOMS 3,460,433

- PORT PLATES FOR HYDRAULIC RECIPROGATING PUMPS AND MOTORS Filed Sept. 15, 1967 2 Sheets-Sheet 2 FIG. 2

United States Patent 3,460,483 PORT PLATES FOR HYDRAULIC RECIPROCAT- ING PUMPS AND MOTORS Harry Simister Bottoms, Solihull, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England, a British company Filed Sept. 15, 1967, Ser. No. 667,902 Int. Cl. F04d 1/ 00 US. Cl. 103--162 5 Claims ABSTRACT OF THE DISCLOSURE In an hydraulic swash plate type pump or motor there is a port plate having straight inserts disposed in straight grooves in its surface, said inserts defining a closed regular and symmetrically disposed figure about the ports in the port plate.

This invention is applicable to hydraulic pumps and motors of the kind comprising a body having an inlet and an outlet for liquid, a rotor mounted in the body containing a plurality of reciprocatory pistons in respective bores therein, means for reciprocating the pistons as the rotor rotates, and a port plate disposed between the rotor and the part of the body through which the inlet and outlet extend. Such a pump or motor will be referred to as being of the kind specified.

The face of the port plate against which the rotor engages has been provided with one or more inserts of material such as carbon to provide good bearing surfaces and also to sustain the loads applied thereto and it has been proposed to form these inserts as rings. However, some materials such as, for example, carbon, are so brittle that it has been found diflicult to machine relatively large rings without cracking occurring.

The object of this invention is to provide a port plate for a pump or motor of the kind specified in which this problem is overcome or reduced.

The present invention resides in the provision of a port plate for a pump or motor of the kind specified having, in its face intended to be disposed adjacent to the rotor, a plurality of straight slots containing straight inserts respectively, the inserts defining a closed regular figure surrounding the ports in the plate, and being symmetrical about the axis of rotation of the rotor.

The invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 is a cross-sectional side elevation view of a pump or motor incorporating the present invention, and

FIGURE 2 is an end elevation view of a port plate for use in the pump or motor of FIGURE 1.

The pump or motor to which this invention is applied comprises a body in which is rotatably mounted a rotor 11 having a plurality of bores 12 containing respective reciprocatory pistons 13. The body 10 has at one end, an inlet 14 and an outlet 15 for liquid, and at the opposite end of the rotor 11 is disposed an inclined swashplate 16, the angularity of which can be varied, and against which the pistons 13 are urged by respective springs 17 in the bores 12 in the rotor 11. Between the end of the rotor 11 remote from the swash plate 16 and the end of the body 10 in which the inlet 14 and outlet 15 are formed, is disposed a port plate 18 which is held against angular movement relatively to the body, and in which are formed two kidney shaped ports 19, 20 communicating with the inlet 14 and with the outlet 15 respectively, and affording communication between the inlet 14 and the outlet 15 and the bores 12 in the rotor 11 in turn as the rotor rotates within the body 10.

3,460,483 Patented Aug. 12, 1969 The port plate 18 has its kidney shaped ports 19, 20 disposed symmetrically about the axis of rotation of the rotor 11. The face of the port plate 18 which is illustrated in FIGURE 2, is that which is intended to be disposed adjacent to the rotor end face. To provide bearing surfaces against which the rotor end face engages there are a plurality of inserts formed, for example, from a material such as vitreous carbon. There is an inner ring like insert 21 inside the inner margins of the ports 19, 20 and mounted in an annular groove. Surrounding the ports 19, 20 are a plurality of further inserts 22, in the form of straight strips of carbon disposed in appropriately shaped slots 23 respectively, formed in the face of the port plate 18, the inserts 22 defining in the example illustrated, a closed regular hexagonal figure. The slot lengths exceed those of the strip inserts 22 and, as illustrated, the inserts 22 are arranged to butt, one against the next, one end of each being inclined for this purpose. The direction of rotation of the rotor relatively to the port plate 18 is indicated by the arrow 24, this relative rotation tending to hold the inserts 22 in close contact with one another at the appropriate end thereof.

The annular groove for the insert 21 and the straight slots 23 for the straight inserts 22 are conveniently machined. The straight inserts 22 are preferably disposed in grooves 23 which, as illustrated, are longer than the inserts 22 themselves. These grooves 23 may be formed by milling or other machining operations.

Between the ends of the ports 19, 20 and extending near radially are further straight inserts 25 in respective slots 26. These further inserts 25 extend between the outer surface of the ring 21 and the inwardly presented surfaces of the inserts 22.

All the

inserts

21, 22 and 25 extend above the adjacent surface of the port plate 18 itself.

In an alternative construction, however, the surfaces of the inserts are only slightly proud of the port plate surface and the inserts 25 may be omitted in this form of the invention. An example of the projection of the inserts with respect to the surface of the port plate is 0.002 inch.

It is to be understood that the inserts 22 can define any regular closed figure enclosing the ports 19, 20 in the port plate 18, but this figure should be symmetrical about the axis of rotation of the rotor relatively to the port plate 18.

It has been found that the manufacture of straight strips of materials such as carbon, which are brittle, can be more readily accomplished without cracking than the manufacture of relatively large size rings, and the invention therefore offers substantial manufacturing advantage.

The width of the inserts 22 must be calculated to correspond with the desired pressure balance between the rotor and valve plate.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A port plate for an hydraulic machine having two kidney shaped symmetrically arranged ports, and having, in its face, a plurality of straight slots containing straight inserts respectively, the inserts defining a closed regular figure surrounding the ports in the plate, and being symmetrical about the centre of the plate, the inserts being formed from vitreous carbon.

2. A port plate as claimed in claim 1 in which a further insert of ring like form is disposed inside the inner margins of the ports.

3. A port plate as claimed in claim 2 in which there are further straight inserts in respective slots disposed between the ends of the ports and extending generally radially between the external surface of the ring-like insert and the inwardly presented surfaces of the straight inserts.

4. A port plate as claimed in claim 3 in Which the inserts extend above the adjacent surface of the port plate.

5. An hydraulic machine comprising a body having an inlet and an outlet for liquid, a rotor mounted Within the body, a plurality of pistons disposed within respective bores in the rotor, means for reciprocating the pistons as the rotor rotates, and a port plate disposed between the rotor and that part of the body through which the inlet and outlet extend, the port plate having two kidney shaped symmetrically arranged ports and having in its face, a plurality of straight slots containing straight inserts respectively, the inserts defining a closed regular figure surrounding the ports in the plate, and being sym- References Cited FOREIGN PATENTS 8 /1965 Canada.

ROBERT M. WALKER, Primary Examiner metrical about the centre of the plate, the inserts being 15 0' 9 formed from vitreous carbon.

U.S. Cl. X.R.