AU3200189A - Linear reciprocating compressor - Google Patents

Description

"LINEAR RECIPROCATING COMPRESSOR"

TECHNICAL FIELD

This invention relates to a linear reciprocating compressor and in particular to a compressor utilizing waste or solar heat as its primary source of energy.

BACKGROUND ART

Many systems which are presently used, for recovering waste heat or for the utilization of solar heat, require energy to be converted into electrical energy, i.e., electricity, and back again as in the case of steam generators and solar cells. Other systems convert the energy into linear energy which is then converted into circular motion and then back into linear motion again. Each of these changes uses up part of the available energy thus decreasing the overall efficiency of the systems.

DISCLOSURE OF INVENTION

Accordingly, the present invention provides a compressor comprising: a cylinder; a free floating piston dividing the cylinder into at least one compression chamber and at least one working chamber; and inlet and outlet valves for each chamber wherein the piston is arranged so that when a working fluid is introduced into the or each working chamber under the control of the inlet and outlet valves the piston is caused to reciprocate in the cylinder, acting directly on fluid admitted to the or each compression chamber. Preferably twα said working chambers are provided, ^: operable by way of the inlet and outlet valves to driver the s piston in both directions.

Preferably two said compression chambers are provided, " arranged such that the fluid in alternate chambers are compressed when the piston is moved in alternate directions.

Preferably, the cylinder has a reduced diameter central portion, and the piston is bobbin shaped with end flanges and a central portion of corresponding reduced diameter. Seals are formed between the piston's end flanges and the cylinder and between the piston's central portion and the cylinder's central portion, whereby the compression chambers are formed between the piston's end flanges and the ends of the cylinder and the working chambers are formed between the piston's end flanges and the cylinder's central portion.

Preferably one or more pumping chambers are formed within the piston.

Preferably two said pumping chambers are provided, arranged so that alternate chambers are pumped with movement of the piston in alternate directions.

Preferably, the pumping chambers are formed by an axial bore through the piston, divided into two portions by a floating-ball non-return valve connecting the pumping chambers to a pump outlet port, and co-operating with a stationary piston in the form of a spigot formed on, and axially protruding from, the ends of the cylinder, the respective spigots containing the inlet port and inlet valve for each respective pumping chamber.

Preferably, the pump outlet port comprises a bore through the central portion of the piston communicating with the floating-ball non-return valve and communicating with a bore through the central portion of the cylinder via an annular recess formed in the internal surface of the central portion of the cylinder.

BRIEF DESCRIPTION OF DRAWINGS

Notwithstanding any other forms that may fall within its scope, one preferred form of the invention will now be described, by way of example only, with reference to the accompanying drawings in which :

Figure 1 is a line diagram showing the interconnections between the linear reciprocating compressor and peripheral devices in a typical embodiment;

Figure 2 illustrates a sectional view through the compressor; and

Figure 3 is an end view of the compressor of Figure 2.

MODES FOR CARRYING OUT THE INVENTION

Figure 1 shows the compressor 10 of the preferred embodiment arranged in a typical connection. The compressor of the preferred embodiment, which will be described in more detail later, basically comprises a working chamber, a pumping chamber and a compression chamber although it should be realised that the compression chamber may be used for pumping operations and is termed "compression chamber" merely for ease of reference.

From the arrangement shown in Figure 1, the compressor 10 is connected to a boiler 11 which provides the working fluid. A condensor, 12 is provided for condensing the spent working fluid which is returned to the boiler via the pumping chamber. The energy spent by the working fluid is then available to the compressor chamber which in this arrangement is connected to a condensor 13 and evaporator 14 of a refrigeration system, although this system could be replaced by a number of alternatives including a simple pumping arrangement.

The principle of operation of the compressor is the Rankine Cycle, i.e., liquid is vaporised in a boiler, the vapor is used to do the work in the compressor, is condensed and then returned to the boiler for re-use. The energy spent by the working fluid is then available to the compressor for useful work to be done.

Referring to Figures 2 and 3, the preferred embodiment of the compressor will now be described in greater detail.

The compressor 10 has a cylinder 20 having end portions 21 and a central portion 22 of reduced diameter. Disposed within the cylinder is a free floating piston 30 which is bobbin shaped with end flanges 31 sized to fit within the cylinder and a central portion 32 sized to fit within the reduced diameter central portion of the cylinder 22. The working chamber is defined as that area between the piston flanges 31 and the central portion 22 of the cylinder. By this arrangement it can be seen that the working chamber is divided into two portions 41a and 41b separated by the central portion 22 of the cylinder. Within the central portion 22 there are disposed inlet valves 44 and outlet valves 45, in the form of poppet valves, to control the inlet and outlet of the working fluid into and from the working chamber 41. The working chamber inlet 23 is located in the central portion 22 of the cylinder and is opened and closed by the inlet poppet valve 44. The working chamber outlet 24 is also located within the central portion 22 of the cylinder and is controlled by the outlet poppet valve 45. Each poppet valve comprises two valve heads 47 interconnected by a valve stem 48, the valve heads 47 bearing against respective valve seats 46 to seal the working chamber. The inlet poppet valve 44 has an extension spigot 49 which is arranged to bear against the end flange 31 of the piston as the piston approaches the central portion 22 of the cylinder, thus shifting the valve from the closed postion to the open position as the piston nears the end of its stroke, simultaneously closing the inlet valve of the corresponding working chamber. At the same time the exhaust valve 45 is operated by contact with the piston flange thereby closing the exhaust valve and opening the exhaust valve of the corresponding working chamber, allowing the working fluid to be exhausted through the working chamber outlet 24. Thus it can be seen that the working chamber operates in a double action arrangement driving the piston in both directions alternately. Seals 50 are provided between the piston flanges 31 and the cylinder 20 and between the central portion 22 of the cylinder and the central portion 32 of the piston to seal the working chamber.

A pumping chamber is provided, formed as an axial bore 33 in the piston 30. The pumping chamber is divided into two portions 43a. and 43b_ by a non-return valve 34 located in the middle of the axial bore 33. The non-return valve 34 is preferably in the form of a floating ball as shown, however, any other form of suitable non-return valve may be used. The axial bore 33 co-operates with a spigot or stationary piston 38 formed on the end portion 21 of the cylinder. This stationary pistion co-operates with the movable piston 30 to pump the pumping chamber 33. Again, operation of the pumping chamber is a double action arrangement whereby the pumping chamber is pumped when the piston moves in either direction. The spigot 38 contains the pumping chamber inlet and non-return valve 27. A seal 50 is provided between the movable piston 30 and a stationary piston 38 to seal the pumping chamber.

The floating-ball non-return valve 34 is provided between the outlets from the axial bore 33 and is in turn connected to the pumping chamber outlet 28 which comprises a radial passage through the central portion 22 of the cylinder and a radial bore 35 through the central portion 32 of the piston. The outlet bore 35 communicates with the outlet port 28 via a recess 29 formed in the internal surface of the reduced diameter central portion 22 of the cylinder. This recess is in the form of an annulus intermediate the seals 50 sealing the working chamber between the central portion 22 of the cylinder and the central portion 32 of the piston and is sufficiently wide to enable the transfer of fluid between the outlet bore 35 and outlet port 28 over the entire stroke of the piston 30.

Two compression chambers 42a. and 42b_ are provided, comprising the volumes located between the end flanges 31 of the piston and the end portions 21 of the cylinder. The inlet and outlet to each compression chamber 42a/b is controlled by non-return inlet valves 25 and non-return outlet valves 26. The compressor chambers are arranged in a double acting arrangement so that movement of the piston in either direction causes one of the compression chambers to reduce in volume.

Operation of the compressor will now be summarised. Working fluid is introduced into working chamber 41b via the inlet port 23 via open poppet valve 47 and drives the piston 30 in one direction (left to right as seen in Fig. 2), the piston thus reduces the volume of compression chamber 42b_ and the pumping chamber portion 43b.. At the end of its stroke the piston mechanically contacts and operates the inlet and outlet poppet valves 44 and 45 and the working fluid is introduced into the corresponding working chamber

41ϋ driving the piston into the opposite direction (right to left as seen in Fig. 2) thereby reducing the volume of the corresponding pumping and compression chambers 43a., 42a., at the same time expanding the first mentioned pumping and compression chambers thereby drawing fresh fluid into these chambers. In a typical operation, boiler gas under pressure, for example, 90°C (400psi) enters the working chamber inlet manifold 23 and passes into the appropriate working cylinder via the inlet poppet valve 44. The working fluid causes the piston to move to the end of its stroke expanding the working chamber. The spent working fluid is then passed to the condensor 12 where the working fluid is condensed and in liquid form is pumped via the pumping chamber 43 to the boiler 11 where it is reheated to form a gas. As the pump is a positive action type pump, the liquid pressure is raised from approximately 150psi (condensor pressure) to 400psi (boiler pressure) and passes onto the boiler 11 via the pump outlet port 28. This process uses approximately 10% of the power output of the drive piston leaving up to 90% of power available for useful work in the compression chamber 42.

The energy source for operation of this compressor can be any source of heat including waste heat and solar heat as long as the temperature maintained is sufficiently above ambient (or condensor) temperature to remain effective, e.g., 80°C is ample where ambient is 30°C and 60°C is ample where ambient is 15°C. Therefore solar energy can be utilised even in the cooler latitudes without the need to concentrate heat in a solar collector. If waste or solar heat is being used, the cost of the energy source is nil.

The compression chamber may be used for a number of different functions and its function may be either as a compressor or as a pump as previously mentioned. A number of alternative uses for the compression chamber is illustrated by way of example only and includes the following, although, of course, other uses are possible.

(1) First usage is as a refrigeration compressor in which the sweep volume would be approximately 1.5 times the sweep volume of the drive cylinders. Operation would be as a normal reciprocating compressor and the refrigerant used could be the same refrigerant as used in the drive process. In this arrangement it is possible to use the same (or at least interconnected) condensers as per Figure l.The compressor unit could then be hermetically sealed to prevent any leakage to atmosphere.

(2) Another use is as an airconditioning compressor for motor vehicles. Evaporator pressures would be higher and would therefore allow a sweep volume greater than 1.5 times the sweep volume of the drive piston. This use is basically a variation of (1) .

(3) The compressor may be used as a fluid pump, (e.g. water pump for bore applications) in which case the cylinders could be designed for:

(a) low pressure/high volume, or

(b) high pressure/low volume applications according to sweep volume. However, in this type of use the unit could not be hermetically sealed.

(4) Usage as an air compressor is also possible with maximum pressures dependant on the sweep volume although pressure ranges from 50 to 200psi can easily be envisaged. Hermetic sealing is not impossible in this type of usage.

As can be seen from this simple arrangement, the action of the piston is maintained in a linear fashion and directly acts upon the fluids to be compressed. Therefore no energy is lost in converting the linear motion of the piston to circular motion and back into linear motion, thus increasing the efficiency of the compressor. The motion need not be fast, therefore, maintenance will be minimal which is suitable for remote areas when coupled with solar heating, therefore offering a further advantage over machines operating at high speed which require more frequent maintenance and services.

Claims (11)

1. A compressor comprising: a cylinder; a free floating piston dividing the cylinder into at least one compression chamber and at least one working chamber; and inlet and outlet valves for each chamber; wherein, the piston is arranged so that when a working fluid is introduced into the or each working chamber under the control of the inlet and outlet valves the piston is caused to reciprocate in the cylinder, acting directly on the fluid admitted to the or each compression chamber.

2. A compressor as defined in claim 1 wherein two said working chambers are provided, operable by way of the inlet and outlet valves to drive the piston in both directions.

3. A compressor as defined in claim 1 or claim 2 wherein two said compression chambers are provided, arranged such that the fluid in alternate chambers is compressed when the piston is moved in alternate directions.

4. A compressor as defined an any one of the preceding claims wherein the valves controlling the working chamber are poppet valves which are operated by direct contact with the piston at or near the end of its stroke.

5. A compressor as defined in any one of the preceding claims, wherein; the cylinder has a reduced diameter central portion; the piston is bobbin shaped with end flanges and a central portion of corresponding reduced diameter; and seals are formed between the piston's end flanges and the cylinder and between the piston's central portion and the cylinder's central portion, whereby the compression chambers are formed between the piston's end flanges and the ends of the cylinder and the working chambers are formed between the piston's end flanges of the piston and the : central portion of the cylinder.

6. A compressor as defined in claim 5 wherein the flanges of the piston directly contact the poppet valves for operation thereof.

7. A compressor as defined in any one of the preceding claims further comprising one or more pumping chambers formed within the piston.

8. A compressor as defined in claim 7 wherein two said pumping chambers are provided, arranged so that alternate chambers are pumped with movement of the piston in alternate directions.

9. A compressor as defined in claim 8 wherein the pumping chambers are formed by an axial bore through the piston, divided into two portions by a floating-ball non-return valve connecting the pumping chamber to a pump outlet port, and co-operating with a stationary piston in the form of a spigot formed on, and axially protruding from, the ends of the cylinder, the respective spigots containing the inlet port and inlet valve for each pumping chamber.

10. A compressor as defined in claim 9 wherein the pump outlet port comprises a bore through the central portion of the piston communicating with the floating-ball non-return valve and communicating with a bore through the central portion of the cylinder via an annular recess formed in the internal surface of the central portion of the cylinder.

11. A compressor substantially as hereinbefore described with reference to the accompanying drawings.