GB2074653A - Rotary positive-displacement Pumps - Google Patents

Abstract

In a two-stage liquid pump a rotor 15 is furnished with both a plunger(s) 19 and a sliding vane(s) 28, which displace liquid in a radial bore(s) 18 and a space between the rotor and an eccentric cam ring 20, respectively, the rate of displacement of the vane(s) being greater than that of the plunger(s). The outlet port (30), Fig. 3 (not shown), communicating with said space is connected e.g. by way of an electrically-operated valve 33, to an inlet port 26 associated with the bore(s). A spring-loaded cheek-plate (23), Fig. 1 (not shown), may abut one side of the rotor, the pressure in said space being regulated by this plate. The cam ring may be mounted on rollers (21). <IMAGE>

Description

SPECIFICATION Liquid Pumps This invention relates to pumps for delivering liquid at a high pressure and of the kind comprising a plunger slidably mounted within a bore formed in a rotor and means engaging with the outer end of the plunger for effecting movement of the plunger in a direction to displace fuel from the bore to an outlet.

In a known form of such a pump the plunger is arranged in a radial bore in the rotor, the rotor being provided with an axially extending cylindrical cavity in which is located a port block which contains the afore-said outlet and also an inlet. The rotor is surrounded by an annular member the inner surface of which is engaged with the outer end of the plunger, the axis of the inner surface of the annular member being eccentrically disposed relative to the axis of rotation of the rotor. With such a construction it is necessary to supply liquid under pressure to the inlet in order to move the plunger in the bore to fill the bore with liquid. This requires an additional pump together with the associated drive arrangement.

The object of the present invention is to provide a pump of the kind specified in a simple and convenient form wherein no additional pump is required.

According to the invention in a pump of the kind specified the rotor mounts an outwardly extending slidable vane which co-operates with the internal surface of an annular member surrounding the rotor, the axis of the internal surface of said member being eccentrically disposed relative to the axis of rotation of the rotor, said surface also being engaged by the plunger, the vane forming part of a vane pump having a greater displacement than the pump formed by the plunger and also having an inlet for liquid and an outlet and passage means for conveying liquid from said outlet to an inlet which is brought into communication with said bore as the rotor rotates.

An example of a pump in accordance with the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of the pump; Figure 2 is a section on the line A-A of Figure 1; Figure 3 is a section on the line B-B of Figure 1.

Referring to the drawings the pump comprises a multi-part body generally indicated at 10 and which includes a first portion 11 formed with a cylindrical port block 12 extending beyond one face thereof. In the opposite end face there is located a chamber 13 which communicates with a high pressure liquid outlet 14.

Surrounding the port block is a cup shaped rotor 15, the rotor being provided with an axially extending cylindrical cavity. Moreover, the rotor has an extension 1 6 which extends to the exterior of the body, the extension being supported by means of bearings in the base wall of a cup shaped portion 17 of the body, the cup shaped portion 17 being engaged about a reduced portion of the part 11 of the body.

The rotor 1 5 is provided with, in the particular example, four radially extending equiangularly spaced bores 18 in which are located plungers 1 9 respectively. The peripheral surface of the rotor is of cylindrical form and the rotor is surrounded in spaced relationship, by an annular ring member 20 the internal peripheral surface of which is engaged by the outer ends of the plungers. The ring member 20 is supported on rollers 21, only a few of which are shown, within a further ring member 22 which is fixed within the cup shaped portion 17 of the body.The ring members 20 and 22 together with the rotor, are biassed towards the end face of the body portion 11 by means of a side plate 23 which engages the ring members and the rotor, the side plate being biassed by compression springs 24 located in suitable recesses in the cup shaped portion of the body.

The axis of the internal surface of the ring member is eccentrically disposed relative to the axis of rotation of the rotor and so also therefore if the internal surface of the ring 20.

The block 12 has a pair of ports defined in its peripheral surface, one of these referenced 25, constitutes the outlet port for the pump constituted by the plungers, and it is connected to the chamber 13. The other port referenced 26, constitutes the inlet for the plunger pump and it is connected to a recess 27 on the periphery of the body portion 11. The rotor rotates in the clockwise direction as seen in Figure 2 and the centre of the internal surface of the ring 22 is offset towards the right relative to the axis of rotation of the rotor again as seen in Figure 2. As a result when the inner ends of the bores 18 are brought into communication with the port 26, liquid under pressure, as will be explained, is supplied to the inner end of the bore to effect outward movement of the plunger.This movement continues through substantially 1 80C and during continued rotation, the plungers then start to move inwardly during which time the inner ends of the bores communicate with the outlet groove 25. As a result liquid is displaced to the chamber 13.

Alternately disposed relative to the bores 18, are radially disposed slots 27A having blind ends spaced outwardly from the internal peripheral surface of the rotor. The slots extend to the periphery of the rotor and mount vanes 28 respectively. Moreover, formed in the end surface of the body portion 11 which is engaged by the rings 20, 22 and the rotor, is a pair of arcuate ports 29, 30. Port 29 constitutes the inlet port for the vane pump constituted by the vanes and it is connected to a liquid inlet 31 on the exterior of the body. Port 30 constitutes the outlet port for the vane pump and it is connected to a recess 32 formed next to the recess 27.Assuming for the moment that the two recesses 27 and 32 are placed in communication with each other, then as the rotor rotates the vanes act as a pump to draw liquid from the inlet 31 and to displace it to the inlet port 26 of the plunger pump. It is arranged that the displacement of the vane pump is greater than the displacement of the plunger pump and the output pressure of the vane pump is controlled by the action of the springs 24 which bias the plate 23. In the event that the pressure rises above a predetermined value, then the plate 23 will be displaced axially against the action of the springs 24 and the output pressure of the vane pump will be controlled.

The amount of liquid at high pressure flows through the outlet 14 is controlled Dy a valve generally indicated at 33 and which controls the communication between the recesses 27 and 32.

Conveniently the valve is electromagnetically controlled. If the outlet 14 is connected to an accumulator, the pressure within the accumulator can be controlled by varying the current flowing in the winding of the actuator. It is convenient to include a non-return valve between the outlet and the accumulator.

Claims (8)

Claims

1. A pump for delivering-liquid at high pressure comprising a body, a rotor rotatable within the body, a bore formed in the rotor and a plunger therein, an annular member surrounding the rotor, the internal surface of said member being eccentrically disposed relative to the axis of rotation of the rotor, the outer end of said plunger engaging said surface, a liquid outlet in the body, an inlet in the body for communication with said bore, port means operable upon rotation of said rotor for placing the inner end of said bore in communication with the liquid outlet and said inlet in turn, an outwardly extending slidable vane carried by the rotor, the outer end of said vane engaging said surface an outlet port to receive liquid displaced by said vane upon rotation of said rotor, an inlet port connected to a liquid inlet in the body, liquid during rotation of the rotor, flowing through said inlet port for displacement by the vane and passage means connecting said outlet port with said inlet whereby liquid delivered by the pump defined by said vane is supplied to said bore through said inlet, the displacement of the pump defined by said vane being greater than the pump defined by said plunger.

2. A pump according to claim 1 including means operable to limit the pressure of liquid at said inlet.

3. A pump according to claim 2 including valve means operable to control the flow of liquid through said passage means.

4. A pump according to claim 1 in which said rotor is rotatably mounted about a cylindrical port block defined by the body, said port block defining a pair of ports communicating with said liquid outlet and said inlet respectively, the inner end of said bore communicating in turn with said pair of ports.

5. A pump according to claim 4 in which said body defines an end surface against which one end face of the rotor is urged, said inlet port and said outlet port being of arcuate form and being formed in said end surface.

6. A pump according to claim 5 including an annular plato located against the other end face of the rotor and resilient means biassing said annular plate into engagement with said other end face, said annular plate being moved in use away from said other end face against the action of said resilient means to control the fluid pressure at said outlet port.

7. A pump according to claim 6 in which said annular member is supported in rollers within a further annular member mounted in the body.

8. A pump for delivering liquid at high pressure comprising the combination and arrangement of parts substantially as hereinbefore described with reference to the accompanying drawings.