GB2144181A

GB2144181A - Gas compressors

Info

Publication number: GB2144181A
Application number: GB08320239A
Authority: GB
Inventors: David Keith Andrews; Michael William Smart
Original assignee: Dowty Fuel Systems Ltd
Current assignee: Dowty Fuel Systems Ltd
Priority date: 1983-07-27
Filing date: 1983-07-27
Publication date: 1985-02-27
Also published as: GB2144181B; GB8320239D0; IT8448612A0; FR2549906A1; DE3427051A1; IT1177920B; FR2549906B1

Abstract

A gas compressor comprising a non-rotatable cylinder barrel 1, at least three cylinders in the barrel, progressively reducing in diameter from one, 8, of largest diameter to one of smallest diameter, a piston 9 slidable in each cylinder, and a wobble plate 4 co-operable with the pistons for causing them to reciprocate in their cylinders. A valve-controlled gas inlet is provided to the largest diameter cylinder and a valve-controlled gas outlet is provided from the smallest diameter cylinder. A gas receiver 13 is disposed intermediate each pair of successive cylinders. Outlet valve means is provided between a cylinder and an associated receiver and an inlet valve means is provided between a cylinder and another associated receiver. <IMAGE>

Description

SPECIFICATION Gas compressors This invention relates to gas compressors.

According to this invention a gas compressor comprises (i) a non-rotatable cylinder barrel, (ii) at least three cylinders in the barrel, progressively reducing in diameter from one of largest diameter to one of smallest diameter, (iii) a piston slidable in each cylinder, (iv) a wobble plate co-operable with the pistons for causing the pistons to reciprocate in their cylinders, (v) a valve-controlled gas inlet to the largest diameter cylinder, (vi) a valve-controlled gas outlet from the smallest diameter cylinder, (vii) a gas receiver intermediate each pair of successive cylinders, (viii) outlet valve means between a cylinder and an associated receiver, and (ix) inlet valve means between a cylinder and another associated receiver.

The end of the piston which reciprocates within the cylinder of largest diameter may be so associated with the wobble plate as substantially to prevent relative rotation between the wobble 2 plate and the piston as the wobble plate moves to cause the pistons to reciprocate in their associated cylinders.

The valve controlling the inlet to the cylinder of largest diameter may be a reed-type valve. The outlet valve between the cylinder of largest diameter and its associated receiver may also be a reedtype valve.

The remaining valves may be plate-type valves.

Each piston may have a sealing device engaging with its associated cylinder substantially to prevent leakage of gas. The space surrounding the wobble plate may contain lubricating liquid and each piston may have a further sealing device, spaced apart from the aforementioned sealing device, substantially to prevent leakage of lubricating liquid. A drain means may be provided between two such sealing devices on a piston to remove any gas or liquid which may have leaked past a seal. The wobble plate may be supported on low-friction bearings.

Gas compressors in accordance with the invention have many advantages.

In particular, one gas compressor in accordance 3 with one embodiment of the invention is capable of providing a very low mass flow, for example 7.5 x 10-3 to 30 x 10-3 gramme per second, at a highpressure ratio, say greater than 200:1.

This compressor can operate for a long period of time at a low speed with high efficiency and supply a device with compressed gas at a very low mass flow.

Such a compressor because of the manner of its operation, can use low-leakage sealing devices of the kind conventionally used in low-speed pneumatic devices, e.g. pneumatic rams, to provide high-operating efficiency, rather than high leakage piston rings, and its parts are made in accordance with conventional machining techniques.

One such low-leakage sealing device is a p.t.f.e.

ring energised by a rubber inner ring.

A gas compressor in accordance with one embodiment of the invention is illustrated in the accompanying drawings. This illustrated gas compressor is shown by way of example of the invention and not by way of limitation thereof. In the drawings: Figure 1 is a side view of the gas compressor, and Figure 2 is an enlarged scrap view of an interstage receiver.

Referring to the drawings, the gas compressor includes a cylinder barrel 1 which, in use, is stationary and a cover 2 within which is supported, by means of low-friction bearings, a head 3. The head 3, in use, will be caused to rotate by a shaft (not shown). Against the head is disposed a wobble plate 4. The wobble plate is held against the head 3 by a ball 5 and retaining plate 6, which are together spring-urged in the direction away from the cylinder barrel 1, the plate 6 bearing against the wobble plate through the intermediary of slippers, one of which is shown at 7.

The cylinder barrel has three axially-aligned cylinders 8, only one of which is visible in Figure 1.

The axes of the cylinders are spaced apart at 1200 intervals. One of the cylinders (that visible in the drawing) has the largest diameter, one has the smallest diameter, and the third has an intermediate diameter.

In each cylinder there is disposed a piston 9 (only one of which is shown in Figure 1) and each piston has a piston rod 10 engageable through the intermediary of a respective slipper 7 with the wobble plate 4. Thus, as the plate 4 is caused to wobble backwards and forwards as a consequence of rotation of the head 3, the pistons are caused to reciprocate within their cylinders the one in suitable phase relationship with the others to provide the necessary compression of gas.

The piston rod 10 of the piston associated with the cylinder of largest diameter is secured directly to its slipper 7 which in turn is suitably located at 11 in retaining plate 6 so that substantially no rotational movement of the retaining plate occurs as head 3 rotates.

The cylinder of largest diameter is connected by means of an inlet valve to a suitable gas inlet port in the cylinder barrel 1 The inlet valve may, conveniently, be of the reed-type.

As the piston is moved in the cylinder of largest diameter to increase the volume of the cylinder, gas is drawn into the cylinder through the inlet valve. As the piston subsequently is moved back within that cylinder to decrease the volume of that cylinder, the gas is compressed, and will open an outlet valve 12 (see Figure 2), which may also be a reed-type valve, to a first compressed gas receiver 13 formed in the cylinder barrel 1.

The first compressed-gas receiver 13 is connected by way of an inlet valve 14 (see Figure 2), which may be a plate-type valve, to the cylinder of intermediate diameter.

As the piston within the cylinder of intermediate diameter is caused to move by subsequent movement of the wobble plate to increase the volume of that cylinder, inlet valve 14 will open and compressed gas will pass from the first receiver 13 into the cylinder of intermediate diameter. As the piston is subsequently moved back into the cylinder to reduce its volume, the gas in that cylinder will be further compressed. Eventually that further compressed gas will cause an outlet valve, which may be a plate-type valve, to open to permit the gas to flow into a second compressed gas receiver, formed in the cylinder barrel.

The second compressed-gas receiver is connected, by way of an inlet valve (similar to valve 14), to the cylinder of smallest diameter.

As the piston within the cylinder of smallest diameter is caused to move, by further movement of the wobble plate, to increase the volume of 7 that cylinder, the inlet valve will open and compressed gas will pass from the second compressed-gas receiver into the cylinder of smallest diameter.

As the piston is subsequen tly moved back into the cylinder to reduce its volume, the gas in that cylinder will be even more compressed. Eventually the compressed gas will cause an outlet valve, which may be a plate type valve, to open and connect the cylinder of smallest diameter to a compressed gas outlet port in the cylinder barrel.

Each piston may have a seal 15, substantially to prevent leakage of gas from a cylinder.

The space within the cover 2 may include lubricating liquid, and the piston may have another seal 16, spaced apart from the seal 15, substantially to prevent leakage of liquid.

The space between the two seals 15 and 16 may be connected to a drain channel.

Claims

1. A gas compressor comprising (i) a non-rotatable cylinder barrel, (ii) at least three cylinders in the barrel, progressively reducing in diameter from one of largest diameter to one of smallest diameter, (iii) a piston slidable in each cylinder, (iv) a wobble plate co-operable wirh the pistons for causing the pistons to reciprocate in their cylinders, (v) a valve-controlled gas inlet to the largest diameter cylinder, (vi) a valve-controlled gas outlet from the smallest diameter cylinder, (vii) a gas receiver intermediate each pair of successive cylinders, (viii) outlet valve means between a cylinder and an associated receiver, and (ix).inlet valve means between a cylinder and another associated receiver.

2. A gas compressor as claimed in claim 1 in which the end of the piston which reciprocates within the cylinder of largest diameter is so associated with the wobble plate as substantially to prevent relative rotation between the wobble plate and the piston as the wobble plate moves to cause the pistons to reciprocate in their associated cylinders.

3. A gas compressor as claimed in claim 1 or in claim 2 having three cylinders.

4. A gas compressor as claimed in any one of claims 1 to 3 having reed-type valves associated with the inlet to and the outlet from the cylinder of largest diameter.

5. A gas compressor as claimed in claim 4 in which plate-type valves are associated with the inlet to and outlet from each of the remaining cylinders.

6. A gas compressor as claimed in any one of the preceding claims having, associated with each piston, a pair of spaced-apart sealing devices, and drain means between each pair of sealing devices.

7. A gas oompressor substantially as hereinbefore described and with reference to the accompanying drawings.