ROTARY INTERNAL COMBUSTION ENGINE OR PUMP

The present invention relates to a rotor and chamber assembly for a rotary internal combustion engine or a pump, which may be gas compressor, of the kind having a chamber containing a rotor which maintains contact with the chamber walls and divides the chamber into compartments which vary in volume periodically on rotation of the rotor. In particular, the invention relates to a rotary internal combustion engine of the kind having a chamber containing a rotor which maintains contact with the chamber walls and divides the chamber into compartments which vary in volume periodically on rotation of the rotor so as to allow for decompression, air and fuel intake, compression, combustion and exhaust phases of an internal combustion cycle. The invention further relates to a pump for fluids (which may be a compressor) of the kind having a chamber containing a rotor which maintains contact with the chamber walls and divides the chamber into compartments which vary in volume periodically on rotation of the rotor so as to allow fluid intake, and fluid ejection phases of a fluid pumping cycle.

Various designs for rotary internal combustion engines have been proposed in the past, the best known being that of the Wankel engine currently in production.

Wankel type engines however employ an eccentrically mounted rotary piston rotating in a chamber which is shaped as an epitrochoid.

There is therefore a considerable mass rotating eccentrically and giving rise to out of balance forces acting upon the housing of the engine. Furthermore, the rotary piston is conventionally mounted so that an internal concentric gearing engages a fixed gear wheel connected to the housing and rolls there over during engine operation. This potentially poses problems of tooth wear.

An alternative form of rotary engine is described in United States Patent Specification No. 3,614,277 and 3,782,110. In engines of this type, a rotor equipped with radially extending vanes rotate in an elliptical chamber, the vanes being biased outwardly to contact the chamber walls by a central non-circular cam or cam structure.

Whilst such engines avoid the above disadvantages of engines of the Wankel type, problems remain outstanding. The Wankel type engines fail to produce acceptable torque

and their fuel efficiency remain poor. Also engines of the type described in US Patent Specifications afore mentioned using oval or elliptic shaped housings fail to produce adequate compression and all the moving parts pose a problem of wear and sealing during sustained operation. The present invention provides a rotor and chamber assembly for use in a rotary internal combustion engine or a rotary fluid pump, which assembly comprises a chamber having an interior wall, a fixed cam member within said chamber having an outwardly facing cam surface, a circular rotor surrounding said cam member and mounted for rotation with respect to said cam member about a fixed axis in the chamber, a plurality of radially displaceable sealing members angularly spaced about said axis and each passing through and travelling with said rotor, outward portions of the sealing members sweeping over the interior wall of the chamber inward portions of said sealing members sweeping over the cam surface of the cam member, the cross section of the chamber perpendicular to said axis being a continuous circular curve with two opposite extending arc shaped bulges each defining a space between the rotor and the chamber, and the shape of the cam member mirroring that of the chamber so that the radial distance between the cam surface of the cam member and the interior wall of the chamber is a constant, and such that the rotation of the rotor is accompanied by radial displacement of the sealing members through said rotor by the cam member to maintain contact between the sealing members and the chamber wall, whereby each sealing member periodically sweeps through each space between the rotor and the chamber, so dividing the said space into an expanding portion and a shrinking portion as the sealing member moves therethrough, and at least one inlet for fluid flow into said expanding portion of a said space between the chamber and the rotor, and at least one outlet for fluid flow out of the shrinking portion of a said space between the chamber and the rotor.

The present invention provides in a first subsidiary aspect, a rotor and chamber assembly for use in a rotary internal combustion engine, which assembly comprises a chamber having an interior wall, a fixed cam member within said chamber having an outwardly facing cam surface, a circular rotor surrounding said cam member and mounted for rotation with respect to said cam member about a fixed axis in the chamber, a plurality of radially displaceable sealing members angularly spaced about said axis and

each passing through and traveling with said rotor, outward portions of the sealing members sweeping over the interior wall of the chamber and inward portions of said sealing members sweeping over the cam surface of the cam member, the cross section of the chamber perpendicular to said axis being a continuous circular curve with two diametrically opposed arc shaped bulges each defining a space between the rotor and the chamber, and the shape of the cam member following that of the chamber so that the radial distance between the cam surface of the cam member and the interior wall of the chamber is substantially constant, and such that the rotation of the rotor is accompanied by radial displacement of the sealing members through said rotor by the cam member to maintain contact between the sealing members and the chamber wall, whereby each sealing member periodically sweeps through each space between the rotor and the chamber, so dividing the said space into an expanding portion and a shrinking portion as the sealing member moves therethrough, and at least one inlet for gas flow into said expanding portion of a first said space between the chamber and the rotor, and at least one outlet for gas flow out of the shrinking portion of a second said space between the chamber and the rotor.

The distance between the cam surface and the interior wall of the chamber is constant or is substantially constant so that contact can be maintained with both by sealing members of fixed radial length or of variable length. Where the said distance is not constant, it preferably does not vary by more than 20mm, preferably by not more than 10mm, e.g. not by more than 5mm. Alternatively, the variation is not more than 15% of the minimum distance, more preferably not more than 10% , more preferably not more than 5%, e.g. not more than 2%.

In a second aspect, the invention provides a rotary internal combustion engine which comprises a rotor and chamber assembly as described above, said at least one inlet serving as an inlet for at least combustion air, and said at least one outlet serving as an outlet for combustion gases.

In such a rotary internal combustion engine inward portions of said sealing members may extend through opposed interior spaces between the rotor and the cam member, whereby each sealing member periodically sweeps through each space between the rotor and the cam member, so dividing the said space into an expanding portion and a

shrinking portion as the sealing member moves therethrough, said interior spaces serving as reservoirs for lubricating fluid, there being a flow path for the lubricating fluid from at least one shrinking portion of a said interior space between the rotor and the cam member, and a return flow path for the lubricating fluid to at least one expanding portion of a said interior space for the lubricating fluid.

Said flow path for lubricating fluid and said return flow path may be connected via a lubricating oil fluid cooler, and/or a lubricating fluid filter. Branch or subsidiary flow paths may be provided for conveying lubricating fluid from said shrinking portion of the interior space to bearings and/or other moving parts of the engine. The motor may include means to cool the lubricating fluid, thus cooling the interior elements of the engine, and means to cool the housing, such as a built in cooling water circuit cast in the engine housing.

Preferably, chamber cross-section has a circular portion that occupies two opposed arcs each subtending from 45 to 135 degrees, e.g. 75 to 100 degrees, most preferably from 85 to 95 degrees, especially about 90 degrees. The remainder of the chamber cross-section is of course divided between the two opposed bulges. Thus, preferably, said pair of diametrically opposed arc-shaped outward bulges cover one quarter of the circumference of the chamber each (i.e. each subtend about 90 degrees), one serving as an air- fuel intake and compression chamber and the other as a combustion and expansion chamber.

The radial depth of said bulges may for instance be from 5 to 20%, more preferably from 10 to 16%, of the radius of the rotor, e.g. from 12 to 14%. Alternatively, the radial depth of said bulges may for instance be from 5 to 20%, more preferably from 10 to 16%, of the diameter of the rotor, e.g. from 12 to 14%. The chamber may be shaped such that each opposite bulge has a circular cross sectional shape of a radius less than that of the said circular portion and has a centre lying on a diameter of the said circular portion to one side of the centre of said circular portion but displaced by a selected distance from said centre. The shape is thereby built up from a central larger diameter circular portion and two flanking smaller diameter circular portions.

The rotor preferably fits exactly the cylindrical portion of the housing or chamber and maintains sliding contact with the chamber walls, said rotor having at least one circumferentially running groove providing a path for compressed gas. Alternatively, a gas flow path could be provided by other means communicating between the shrinking gas space ahead of one sealing member and a combustion zone immediately behind the next rotationally more advanced sealing member, which might include a conduit for gas flow circumferentially within the rotor with communication to the rotor surface at least just ahead of said one sealing member.

The engine may comprise four said sealing members, each being radially extensible, such sealing members being disposed at right angles to one another, thus dividing the chamber into four symmetrical compartments.

Optionally, rotationally immediately behind each sealing member there is provided a depression in said rotor defining a combustion chamber. The choice of the size of this depression, together with the volume occupied by the gas flow path referred to above will dictate the minimum volume (at maximum compression) of the fuel/air charge, and hence together with the volume of the spaces between the rotor and the chamber wall provided by the said bulges will control the compression ratio. This is preferably greater than 5:1, preferably greater than 8:1. e.g. from 5:1 to 15: 1, or from 8:1 to 12: 1, particularly for spark induced ignition engines. Thus, the size of these depressions is a function of the desired compression ratio in respect to the volume of the intake compartment.

The sealing members may be divided into radially inner and radially outer portions and means may then be provided urging said portions radially apart in use. This can compensate for variations in the distance between the cam surface and the chamber wall either designed in or generated by tolerances or wear. Springs, e.g. coil springs, may be provided to urge radial separation of said portions so as to keep tight contact with the chamber wall and the cam member, thus providing adequate seal, and also compensating for wear of the vane tips caused by sustained operation.

Preferably the sealing members are each a vane mounted slidingly in a respective axially running slot in the rotor. Thus, each sealing member may be an axially running vane divided between its radially separated ends into male and female portions.

The engine may work by fuel suction but may alternatively be provided with fuel injection means. Also, the engine may be worked by ignition being triggered by spark ignition means angularly spaced around the path of the rotor to provide ignition at a suitably timed moment after the compression phase. Alternatively, engines may be constructed which operate by compression ignition. Air flow may be aspirated or induced by compression by a supercharger or turbocharger.

The present invention provides in a second subsidiary aspect, a rotor and chamber assembly for use in a rotary pump for fluids including both liquids and gasses, which assembly comprises a chamber having an interior wall, a fixed cam member within said chamber having an outwardly facing cam surface, a circular rotor surrounding said cam member and mounted for rotation with respect to said cam member about a fixed axis in the chamber, a plurality of radially displaceable sealing members angularly spaced about said axis and each passing through and traveling with said rotor, outward portions of the sealing members sweeping over the interior wall of the chamber and inward portions of said sealing members sweeping over the cam surface of the cam member, the cross section of the chamber perpendicular to said axis being a continuous circular curve with two diametrically opposed arc shaped bulges each defining a space between the rotor and the chamber, and the shape of the cam member following that of the chamber so that the radial distance between the cam surface of the cam member and the interior wall of the chamber is substantially constant, and such that the rotation of the rotor is accompanied by radial displacement of the sealing members through said rotor by the cam member to maintain contact between the sealing members and the chamber wall, whereby each sealing member periodically sweeps through each space between the rotor and the chamber, so dividing the said space into an expanding portion and a shrinking portion as the sealing member moves therethrough, and at least one inlet for intake fluid flow into said expanding portion of a first said space between the chamber and the rotor, and at least one outlet for fluid flow out of the shrinking portion of a second said space between the chamber and the rotor. When operating with gas as the fluid and operating against a back pressure, the device will operate of course as a gas compressor. There may be a second said inlet for intake fluid flow into said expanding portion of said second space between the chamber and the rotor and a second said outlet for fluid

flow out of the shrinking portion of said first said space between the chamber and the rotor.

The invention includes in a further aspect a rotary fluid pump, e.g. gas/air compressor, which comprises an assembly as described above. Preferably, inward portions of said sealing members extend through opposed interior spaces between the rotor and the cam member, whereby each sealing member periodically sweeps through each space between the rotor and the cam member, so dividing the said space into an expanding portion and a shrinking portion as the sealing member moves therethrough, said interior spaces serving as reservoirs for lubricating fluid, there being a flow path for the lubricating fluid from at least one shrinking portion of a said interior space between the rotor and the cam member, and a return flow path for the lubricating fluid to at least one expanding portion of a said interior space for the lubricating fluid. Optionally, said flow path for lubricating fluid and said return flow path are connected via a lubricating oil fluid cooler, and/or a lubricating fluid filter. Branch or subsidiary flow paths may be provided for conveying lubricating fluid from said shrinking portion of the interior space to bearings and/or other moving parts of the pump/compressor.

Preferably, chamber cross-section has a circular portion that occupies two opposed arcs each subtending from 45 to 135 degrees, e.g. 75 to 100 degrees, most preferably from 85 to 95 degrees, especially about 90 degrees. The remainder of the chamber cross-section is of course divided between the two opposed bulges. Thus, preferably, said pair of diametrically opposed arc -shaped outward bulges cover one quarter of the circumference of the chamber each (i.e. each subtend about 90 degrees), one serving as an air- fuel intake and compression chamber and the other as a combustion and expansion chamber.

The radial depth of said bulges may for instance be from 5 to 20%, more preferably from 10 to 16%, of the radius of the rotor, e.g. from 12 to 14%. More preferably the radial depth of said bulges may for instance be from 5 to 20%, more preferably from 10 to 16%, of the diameter of the rotor, e.g. from 12 to 14%. The chamber may be shaped such that each opposite bulge has a circular cross sectional shape of a radius less than that of the said circular portion and has a centre lying

on a diameter of the said circular portion to one side of the centre of said circular portion but displaced by a selected distance from said centre. The shape is thereby built up from a central larger diameter circular portion and two flanking smaller diameter circular portions. Preferably, the rotor fits exactly the cylindrical portion of the housing or chamber and maintains sliding contact with the chamber walls, said rotor having at least one circumferentially running groove providing a path for displaced fluid, e.g. compressed gas.

There may be four said sealing members, each being radially extensible, such sealing members being disposed at right angles to one another, thus dividing the chamber into four symmetrical compartments.

At least in the case of a gas compressor, rotationally immediately behind each sealing member there is preferably provided a depression in said rotor defining a gas accumulation chamber. The choice of the size of this depression, together with the volume occupied by the gas flow path referred to above will dictate the minimum volume (at maximum compression) of the gas charge, and hence together with the volume of the spaces between the rotor and the chamber wall provided by the said bulges will control the compression ratio when operating against a barrier to gas flow. This is preferably greater than 5:1 , preferably greater than 8:1. e.g. from 5:1 to 15:1, or from 8: 1 to 12:1. Thus, the size of these depressions is a function of the desired compression ratio in respect to the volume of the intake compartment.

The sealing members may be divided into radially inner and radially outer portions and means may be provided urging said portions radially apart in use. Preferably, each is a vane mounted slidingly in a respective axially running slot in the rotor. Each sealing member may thus be an axially running vane divided between its radially separated ends into male and female portions. Springs, e.g. coil springs, are provided to urge radial separation of said portions so as to keep tight contact with the chamber wall and the cam member, thus providing adequate seal, and also compensating for wear of the vane tips caused by sustained operation. In connection with either the internal combustion engine or pump/compressor aspects of the invention, more than two arc shaped bulges may be provided, with

corresponding cam lobes, for instance four such bulges, thus allowing in an engine two combustions per rotation.

The invention may includes means to cool the lubricating fluid, thus cooling the interior elements of the compressor, and means to cool the housing, such as a built in cooling water circuit cast in the compressor housing.

The invention also includes a motor vehicle or a stationary compressor installation including such a compressor as described herein.

The invention also includes a motor vehicle or a stationary engine installation including such an engine as is described herein. The invention will be illustrated by the following description of a preferred example of an engine according to the invention with reference to the accompanying drawings in which :

Figure 1 is a cross section through a said engine on a line perpendicular to its rotor axis (the line I-I of Figure 2). Figure 1 a is a similar cross section through the engine of Figure 1 , with the rotor at a second rotational position;

Figure Ib is a similar cross section through the engine of Figure 1 and Figure Ia with the vanes shown in positions corresponding to a succession of positions of the rotor; and Figure 2 shows a section through the engine along the rotor axis on the line A-A of

Figure 1.

Figure 3 is a cross section through a compressor perpendicular to the rotor axis on the line I-I of figure 4.

Figure 3 a is a similar cross section through the compressor of Figure 3 on the line I-I of Figure 4 but with the rotor moved on by 45 degrees ; and

Figure 4 shows a section through the compressor along the rotor axis on the line A-A of Figures 3 and 3 a.

As shown , an engine according to the invention comprises an engine housing 1 defining a chamber containing a circular cylindrical rotor 3. Rotor 3 is fixed to a power take off shaft 28 for the engine defining an axis of rotation. Four axially running sealing

vanes 5 pass through radial slots 6 in the rotor into a hollow interior 7 of the rotor. Within the rotor there is fixed a cam member 8 having an external cam surface, stationary with respect to the housing, against which cam member abuts one end of each of the vanes 5. Cam member 8 is so shaped that the radial distance from the cam member to the interior wall of the chamber defined by the inside of the housing 1 is constant all around.

The chamber defined by the housing 1 is shaped so that the cross section of the chamber perpendicular to said axis is a continuous circular curve with two diametrically opposed arc shaped bulges each defining a space 2, 4 between the rotor and the chamber, and the shape of the cam member follows that of the chamber so that the radial distance between the cam surface of the cam member and the interior wall of the chamber is a constant. Rotation of the rotor is therefore accompanied by radial displacement of the sealing members through said rotor by the cam member to maintain contact between the sealing members and the chamber wall.

As the rotor turns, each sealing member periodically sweeps through each space 2, 4 between the rotor and the chamber, so dividing the said space into a rotationally upstream expanding portion (rotationally behind the sealing member) and a rotationally downstream shrinking portion (rotationally ahead of the sealing member) as the sealing member moves through the space 2 or 4 respectively.

At least one circumferentially extending groove 13 passes around the whole circumference of the rotor. This provides a gas flow communication allowing equilibration of pressure within compartments defined between successive sealing members as the rotor turns.

Rotationally immediately behind each sealing member 5 is a depression 14 in the outer surface of the rotor 3. This defines a combustion chamber in which combustion is initiated and the size of the depression can be chosen according to the desired compression ratio of the engine.

Angularly spaced around the chamber are an exhaust port 9, fuel/air inlet 10, and a spark ignition means 12. Exhaust port 9 is positioned at the rotationally upstream end of the combustion/expansion space 4. Air inlet 10 is positioned at the rotationally upstream end of the inlet/compression space 2. Spark ignition means 12 is provided at the rotationally upstream end of the combustion/expansion space 2.

Naturally, separate air and fuel inlets may also be provided where fuel is injected directly into the inlet/compression space 2 of the chamber. Fuel/air inlet 10 may have a spiral or other turbulence creating inner surface to provide mixing of the fuel/air charge. Within the rotor, are opposed interior spaces 7 defined between the rotor and the cam member. As the rotor turns, the interior ends of the sealing members pass through the spaces 7 dividing them into rotationally upstream expanding portions and rotationally downstream shrinking portions.

The housing may include channels for cooling fluid circulation and/or may be surrounded by a cooling jacket. Cooling fluid, such as the lubrication oil, may also be passed through channels 11 in the interior of the rotor via feed channels leading to the hollow space 7 inside the rotor. Also, the oil in the interior space 7 is circulated out for cooling, e.g. to a radiator, and for filtering.

To this end, the cam is provided with a plurality of oil outlet channels 21 (Figure 2) and inlet channels 22 forming a flow path for lubricating oil from the interior space 7 of the rotor. A lubricating oil filter and a lubricating oil cooler may be provided between the lubricating oil outlet channels 21 and the lubricating oil inlet channels 22. Additionally, lubricating oil flow path branches may be provided for directing filtered oil under pressure to bearings and the like of the engine with suitable return paths being provided to return the oil to the interior 7. As best seen in Figure 2, the housing 1 is built up and comprises a pair of end plates 23, 24 and an annular wall member 25, suitable gaskets 26 are provided between the end plates and the wall member 25 and the whole assembly is tightened together by bolts 27 extending between the end plates 23 and 24 in slots in the outer surface of the wall member 25. The cam member 8 is bolted to plate 23 in a central region thereof by a plurality of bolts 27, power take-off shaft 28 extends through a central bore in the cam member 8 and is supported by main bearing 29 for rotation with the rotor. Shaft 28 carries a toothed flywheel 30 outside the engine unit.

Annular sealing rings 31 are provided facing inwardly in the end plates 23 , in inward facing annular slots. The sealing rings 31 are urged against the rotor 3 by means of suitable springs 32. Similar sealing rings are provided in end plate 24.

The rotor 3 is generally cup-shaped and is fixed centrally to the shaft 28, the cam member 8 being received within the cup of the rotor.

As best seen in Figure 3, the rotor 3 is provided with axially running through slots 6 within each of which is received a respective sealing vane 5, contacting at one end the interior of the chamber containing the rotor and at the other radially inwardly directed end contacting the exterior of the cam 8.

Each vane 5 is formed as male and female halves joined by a tongue and groove joint 33 constituted by appropriate male and female portions. Within an axially running slot extending radially in the tongue of the joint are positioned coil springs 34 serving to urge the two halves of each vane apart so as to maintain contact with the cam member and the interior wall of the chamber defined by the housing. Running the length of each vane and positioned on each side thereof are sealing strips 35 each contained in an axially running groove opening into the through slot 6 and each biased toward the vane by suitable coil springs 36. Finally, the housing 1 defining the chamber containing the rotor and cam member has in a wall portion adjacent the spark ignition plug 12, a connected series of passages 37 connected to the exhaust outlet 9. Exhaust gases passing through the channels 37 serve to warm the charge in the compression/combustion chamber.

It can be seen that the vanes 5 at any moment divide the chamber into four compartments which in the position illustrated in Figure 1 are such that each is of the same volume as the one opposite, with maximally large compartments following minimally small ones. Upon clockwise rotation of the rotor, it can be seen that the compartment momentarily adjacent the spark ignition is of very small volume compared to the immediately downstream adjacent compartment which at this stage embraces the whole of the space 4. It has of course a volume equal to that of the opposite compartment immediately upstream of the air/fuel inlet 10. Accordingly, it can be seen that the compartments each follow a cycle in which commencing from the position of the compartment opposite the spark ignition means in the drawing, the compartment proceeds from a minimum volume position to a maximum volume position as it passes the air and fuel inlet and therefore the negative pressure produced draws in air and fuel mixture or draws in air and has fuel injected into it. It then passes back to a position of

minimum volume but this time adjacent the spark ignition means thus compressing the fuel air charge for ignition and combustion. As the air/fαel charge is compressed, it flows around the rotor via the circumferential groove or grooves 13. This allows the air/fuel charge displaced rotationally forward from space 2 to move into the depression 14. Following ignition, the compartment is then driven by the expansion of the combustion products and the elevated pressure to a second position of maximum volume whereupon it uncovers the exhaust port and the exhaust gases are exhausted from the chamber as the compartment moves back to initial position of minimum volume. In this last step, the combustion/explosion produces the force, the lever arm of the said force being the distance between the center of the combustion compartment and the center of rotation of the rotor, thus producing an elevated torque value.

Total evacuation of the exhaust products may not be achieved but this may have a beneficial result in preheating the air and fuel charge for the next cycle.

The engine illustrated is capable of four combustions per rotation of the rotary piston (rotor 3).

The extension and retraction of the sealing vanes to maintain them in contact with the interior of the chamber is brought about by the inner ends of the sealing vanes riding over the fixed cam membert 8. In addition, or as an alternative, the halves of the vanes are urged apart by the springs 34. The resiliency in the vanes allows for any tolerance errors in the size and shape of the cam member 8 with respect to the interior of the chamber and for wear of the cam member, vanes and chamber wall.

The materials employed for the actual seal between the vanes and the chamber wall may be similar to those employed conventionally in Wankel engines.

An engine according to the invention may comprise a plurality of chambers as illustrated, arranged axially one behind the other. Naturally, each chamber will be provided with means sealing the front and rear faces of the chamber against the rotary piston. The power of the engine may be varied by providing ignition selectively to more or fewer of such connected units as a partial or total replacement for the normal throttle control. Because of the number and size of the sealing elements 31 and 35 which may be accommodated and the low velocity of movement of the vanes compared to pistons in conventional engines, the life of the sealing elements is expected to be much greater than

that of the piston rings. Wear in the vanes themselves is compensated by the spring structure of the vanes. Accordingly, high compression ratios may be obtained and may be maintained over prolonged use.

The engine illustrated provides smooth engine rotation with essentially total balance because the rotation of the rotor is concentric about a fixed center and the extension and retraction of the sealing vanes is entirely symmetrical. The engine according to the invention may be expected to produce substantially greater torque and power and hence fuel economy, compared to existing internal combustion engines together with saving in volume and weight. Setting the ignition timing of the engine will be simpler than in conventional engines in view of the direct connection between the rotor and the power output shaft.

It will be appreciated that whilst the invention has been described with reference to specific characteristics of the illustrated embodiment, many variations and modifications of the invention are possible within the scope of the invention. For instance, the rotor may be provided with more or fewer than four vanes, preferably symmetrically disposed, to provide more or fewer combustions per rotation. The shape of the rotor 3 and the combustion chamber may be varied in order to affect the compression ratio of the engine and the shape of the combustion chamber as a whole may be other than the shape illustrated. The split vanes may be urged apart other than by springs, e.g. by a feed of pressurized fluid.

Instead of being built up as shown, the housing defining the chamber may be cast in one piece.

As shown, a compressor according to the invention comprises a compressor housing 201 defining a chamber containing a circular cylindrical rotor 203. Rotor 203 is fixed to a shaft driven by an external rotation power source such as an internal combustion engine or an electric motor. Four axially running sealing vanes 205 pass through slots 206 in the rotor into a hollow interior 207 of the rotor. Within the rotor there is fixed a cam member 208 stationary with respect to the housing against which cam member abuts one end of each of the vanes 205. Cam member 208 is so shaped that the radial distance from the cam member to the inside of the housing 201 is constant all

around. Angularly spaced around the chamber are two gas/air inlets 210 and two compressed gas/air outlets 209.

The chamber defined by the housing 201 is shaped so that the cross section of the chamber perpendicular to said axis is a continuous circular curve with two diametrically opposed arc shaped bulges each defining a space 202 between the rotor and the chamber, and the shape of the cam member follows that of the chamber so that the radial distance between the cam surface of the cam member and the interior wall of the chamber is a constant. Rotation of the rotor is therefore accompanied by radial displacement of the sealing members through said rotor by the cam member to maintain contact between the sealing members and the chamber wall.

As the rotor turns, each sealing member periodically sweeps through each space 202 between the rotor and the chamber, so dividing the said space into a rotationally upstream expanding portion (rotationally behind the sealing member) and a rotationally downstream shrinking portion (rotationally ahead of the sealing member) as the sealing member moves through each space 202.

At least one circumferentially extending groove 213 passes around the whole circumference of the rotor. This provides a gas flow communication allowing equilibration of pressure within compartments defined between successive sealing members as the rotor turns. Rotationally immediately behind each sealing member 205 is a depression 214 in the outer surface of the rotor 203. This defines a gas accumulation chamber in which gas is accumulated as it is compressed and the size of the depression can be chosen according to the desired compression ratio of the compressor.

The housing may include channels for cooling fluid circulation and/or may be surrounded by a cooling jacket. Cooling fluid, such as the lubrication oil, may also be passed through channels 211 in the interior of the rotor via feed channels leading to the hollow space 207 inside the rotor. Also, the oil in the interior space 207 is circulated out for cooling, e.g. to a radiator, and for filtering.

To this end, the cam is provided with a plurality of oil outlet channels 221 and inlet channels 222 forming a flow path for lubricating oil from the interior space 207 of the rotor. A lubricating oil filter and a lubricating oil cooler may be provided between the

lubricating oil outlet channels 221 and the lubricating oil inlet channels 222. Additionally, lubricating oil flow path branches may be provided for directing filtered oil under pressure to bearings and the like of the compressor with suitable return paths being provided to return the oil to the interior 207. As best seen in Figure 4, the housing 201 is built up and comprises a pair of end plates 223, 224 and an annular wall member 225, suitable gaskets 226 are provided between the end plates and the wall member 225 and the whole assembly is tightened together by bolts 227 extending between the end plates 223 and 224 in slots in the outer surface of the wall member 225. The cam member 208 is bolted to plate 223 in a central region thereof by a plurality of bolts 227, a power input shaft 228 extends through a central bore in the cam 208 and is supported by main bearing 29 for rotation with the rotor.

Annular sealing rings 231 are provided facing inwardly in the end plates 223, in inward facing annular slots. The sealing rings 231 are urged against the rotor 203 by means of suitable springs 232. Similar sealing rings are provided in end plate 224.

The rotor 203 is generally cup-shaped and is fixed centrally to the shaft 228, the cam member 208 being received within the cup of the rotor.

As best seen in Figure 4, the rotor 203 is provided with axially running through slots 6 within each of which is received a respective sealing vane 205, contacting at one end the interior of the chamber containing the rotor and at the other radially inwardly directed end contacting the exterior of the cam 208.

Each vane 205 is formed as male and female halves joined by a tongue and groove joint 33 constituted by appropriate male and female portions. Within an axially running slot extending radially in the tongue of the joint are positioned coil springs 234 serving to urge the two halves of each vane apart so as to maintain contact with the cam member and the interior wall of the chamber defined by the housing. Running the length of each vane and positioned on each side thereof are sealing strips 235 each contained in an axially running groove opening into the through slot 206 and each biased toward the vane by suitable coil springs 236. It can be seen that the vanes 205 divide the chamber into four compartments which in the position illustrated in Figure 3 are such that each is of the same volume as

the one opposite, with maximally large compartments following minimally small ones. Upon clockwise rotation of the rotor, it can be seen that the compartment momentarily adjacent a gas outlet port 209 is of very small volume compared to the immediately downstream adjacent compartment which at this stage embraces the whole of the space 202. It has of course a volume equal to that of the opposite compartment immediately upstream of the other compressed gas outlet 209. Accordingly, it can be seen that the compartments each follow a cycle in which commencing from the position of the compartment opposite either gas outlet port in the drawing, the compartment proceeds from a minimum volume position to a maximum volume position as it passes the gas inlet and therefore the negative pressure produced draws in gas. It then passes back to a position of minimum volume but this time adjacent the gas outlet thus compressing the gas charge. As the gas charge is compressed, it flows around the rotor via the circumferential groove or grooves 213. This allows the gas charge displaced rotationally forward from a space 2 to move into the next upstream depression 214. Following discharge of compressed gas, the compartment is then driven further on to lie under the next bulge in the chamber wall so as to draw gas in through the gas inlet 210 to the space 202.

The compressor illustrated is capable of two compressions per rotation of the rotary piston. The position of the outlets 209 is not critical and in particular can be further on in the direction of rotation than shown.

The extension and retraction of the sealing vanes to maintain them in contact with the interior of the chamber is brought about by the inner ends of the sealing vanes riding over the fixed cam 208. In addition, or as an alternative, the halves of the vanes are urged apart by the springs 234. The resiliency in the vanes allows for any tolerance errors in the size and shape of the cam member 8 with respect to the interior of the chamber and for wear of the cam member, vanes and chamber wall.

A compressor according to the invention may comprise a plurality of chambers as illustrated, arranged one behind the other. Naturally, each chamber will be provided with means sealing the front and rear faces of the chamber against the rotary piston. Because of the number and size of the sealing elements 231 and 235 which may

be accommodated and the low velocity of movement of the vanes compared to pistons in conventional piston compressors, the life of the sealing elements is expected to be much greater than that of the piston rings. Wear in the vanes themselves is compensated by the spring structure of the vanes. Accordingly, high compression ratios may be obtained and may be maintained over prolonged use.

The compressor illustrated provides smooth rotation with essentially total balance because the rotation of the rotor is concentric about a fixed center and the extension and retraction of the sealing vanes is entirely symmetrical. The compressor according to the invention may be expected to produce substantially greater compression values and power efficiency compared to existing piston or radial compressors and a substantial reduction of the emitted noise level.

It will be appreciated that whilst the invention has been described with reference to specific characteristics of the illustrated embodiment, many variations and modifications of the invention are possible within the scope of the invention. For instance, the rotor may be provided with more or fewer than four vanes, preferably symmetrically disposed, to provide more or fewer compressions per rotation. The shape of the rotor 203 and the chamber may be varied in order to affect the compression ratio of the compressor and the shape of the compression chamber as a whole may be other than the shape illustrated. The split vanes may be urged apart other than by springs, e.g. by a feed of pressurized fluid.

Instead of being built up as shown, the housing defining the chamber may be cast in one piece.

The device described and illustrated above as compressor with reference to Figures 3 onwards will act as a pump for gas or liquid.

In this specification, unless expressly otherwise indicated, the word 'or' is used in the sense of an operator that returns a true value when either or both of the stated conditions is met, as opposed to the operator 'exclusive or' which requires that only one of the conditions is met. The word 'comprising' is used in the sense of 'including' rather than in to mean 'consisting of. All prior teachings acknowledged above are hereby incorporated by reference. No acknowledgement of any prior published document herein

should be taken to be an admission or representation that the teaching thereof was common general knowledge in Australia or elsewhere at the date hereof.