SUMMARY OF THE INVENTION In accordance with the present invention, there is provided a compressor or expansion device for use with compressive fluid and comprising a flexible hose connected between a pair of ports and against which a pair of spaced apart, adjacent contact elements bear whereby a portion of said hose is substantially occluded at both ends thereby entrapping a quantity of compressive fluid therewithin; said pair of contact elements being displaceable along said hose from an inlet port of said pair of ports to an outlet port thereof so as to provide a flow of compressive fluid therebetween; said hose substantially tapering between said pair of ports such that said quantity of compressive fluid is respectively entrapped in a first volume Vi proximal said inlet port and a second volume V2 proximal said outlet port whereby a ratio of pressures Pl/P2 at said pair of ports is proportional to a ratio of said volumes V2/Vi in accordance with the general equation: where k is the adiabatic power for the compressive fluid.

The compressor or expansion device of the present invention essentially makes use of the construction and operation of a peristaltic pump, for example, as described and illustrated in US Patent 4,540,350. However, in the device of the present invention, a hose tapers such that a pair of spaced apart, adjacent contact elements travelling therealong entraps a quantity of compressive fluid within a first volume Vl proximal an inlet port and a second volume2 proximal an outlet port. As a consequence of such a change in volume, there is a proportional change in the pressures Pl and P2 of the same entrapped quantity of compressive fluid respectively at the inlet and outlet ports in accordance with the general equation: where the adiabatic power k: z1.4 for air. Thus, for compression purposes, a hose tapers from its inlet port to its outlet port i. e. it is converging in the direction of flow of compressive fluid whilst for expansion purposes, a hose tapers from its outlet port to its inlet port i. e. it is diverging in the direction of flow of compressive fluid.

The device of the present invention is preferably constructed to provide a high coefficient of performance. To this end, the device is preferably constructed as a sealed housing containing a rotatable carousel of rollers constituting contact elements and a pair of flexible hoses tapering in opposite senses and through which circulates a flow of lubricating liquid. In this arrangement, one of the flexible hoses tapers in the same sense as the direction of rotation of the carousel whilst the other tapers in the opposite sense whereby the expansion of the flow of compressive fluid through the latter hose partly offsets the work required for the compression of the flow of compressive fluid in the former hose.

In addition, a hose preferably has a normally flat construction adapted to be expanded to a substantially elliptical cross section in a transverse direction to its length so as to minimize energy losses due to its repeated deformation. A further advantage provided for by this construction resides in that a hose's walls subtend an angle of less than 90° therebetween when expanded which lends to a longer hose life due to reduced material stresses.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention and to show how the same may be carried out in practice, by way of a non-limiting example, reference will now be made to the accompanying drawings, in which: Fig. 1 is an exploded view of a combined compressor cum expansion device of the present invention; Fig. 2 is a transverse cross section view of a hose of the device of Figure 1; Fig. 3 is a longitudinal cross section view of the device of Figure 1 along line III-III; Fig. 4 is a schematic view of a refrigeration heat exchange system including the combined compressor cum expansion device of Figure 1; and Figs. 5A-5C are transverse cross section views of an entrapped compression hose portion of the system of Figure 4 respectively along lines A-A, B-B and C-C in Figure 3.

DETAILED DESCRIPTION OF DRAWINGS With reference now to Figures 1-3, there is provided a right cylindrical housing 1 having an interior surface 1A and a longitudinal axis 2. The housing 1 is sealed by front and rear cover plates 3 and 4, thereby defining a housing interior 1B whose pressure is under the control of a pump (not shown).

The housing 1 is provided with two pairs of ports 5A and 5B and 6A

and 6B between which are respectively connected flexible hoses 8 and 9 laid end-to-end so as to substantially circumscribe a full circle. The hose 8 tapers from port 5A to port 5B whilst the hose 9 tapers from the port 6B to the port 6A i. e. they taper in opposite senses.

The housing 1 is provided with a further pair of ports 7A and 7B via which a flow of lubricating liquid is circulated therethrough.

The hoses 8 and 9 have a normally flat construction and are adapted to be expanded to a substantially elliptical cross section (see Figure 2). As shown, the hoses 8 and 9 have a three-ply construction including an outer anti-friction hard rubber sleeve 10 to diminish friction loss and to prevent leakage of compressive fluid, an intermediate fabric sleeve 11 to provide strength and an inner soft rubber sleeve 12 to prevent leakage of compressive fluid from a hose portion delimited by a pair of adjacent rollers as described below.

A carousel 13 of equiangularly spaced five rollers 14A, 14B, 14C, 14D and 14E is driven about the longitudinal axis 2 by a motor (not shown) in a direction of rotation A. Each roller 14 is freely rotatable about an axis of rotation parallel to the longitudinal axis 2 and is adapted to bear against the hoses 8 and 9 so as to deform same against the housing's interior surface 1A whereby pair of rollers (14A, 14B), (14C, 14D) and (14D, 14E) respectively define therebetween hose portions 8A, 9A and 9B.

As described above, by virtue of its tapering in the same sense as the direction of rotation A, the ports 5A and 5B respectively constitute inlet and outlet ports for the hose 8 which acts as a compressor whilst by virtue of its tapering in an opposite sense to the direction of rotation A, the ports 6A and 6B respectively constitute inlet and outlet ports for the hose 9 which acts as an expansion device.

The operation of the peristaltic device is now described with reference to Figure 4 which schematically shows the housing 1 constituting part of a

refrigeration heat exchange system 15 which includes a hot high pressure heat exchanger 16 connected between the ports 5B and 6A and a cold low pressure heat exchanger 17 connected between the ports 6B and 5A. For operation of the system 15, the pressure in the housing interior 1B is reduced so as to be less than the pressure of the incoming flow of refrigerant through inlet port 5A and the carousel 13 is rotated in the direction of rotation A.

As the carousel 13 rotates, the volume of the hose portion 8A entrapped by the rollers 14A and 14B monotonically decreases from a maximum volume Vl proximal the inlet port 5A i. e. at line A-A to a minimum volume2 proximal the outlet port 5B i. e. at line C-C so the pressure P2 at the outlet port 5B <BR> <BR> <BR> <BR> increases relative to the pressure Pi at the inlet port 5A. For example, for k; 1.4 for air, the device can achieve a compression from Pi = 3 bar to P2 = 6.16 bar due to a decrease in volume from Vil=0.0001 in to V2=0.00006 m3. Against this, in a similar and opposite manner, the pressure at the outlet port 6B is less than that at the inlet port 6A.

While the invention has been described with respect to a limited number of embodiments, it will be appreciated that many variations, modifications and other applications of the invention may be made. For example, a compressor or expansion device of the present invention can be employed in air conditioning systems, commercial production of solar energy, and the like. In addition, a device installed in a sealed housing may be operated in an open cycle mode when the prevailing pressure within the housing is less than about 0.8 Atm in which case the device no longer requires a cold low pressure heat exchanger instead of which the ambient air acts as a refrigerant.