GB2456809A

GB2456809A - Compressor

Info

Publication number: GB2456809A
Application number: GB0801320A
Authority: GB
Inventors: Tom Oswald
Original assignee: OSMATIC SYSTEMS Ltd
Current assignee: OSMATIC SYSTEMS Ltd
Priority date: 2008-01-24
Filing date: 2008-01-24
Publication date: 2009-07-29
Also published as: GB0801320D0

Abstract

A compressor 1 comprising a rotating body 2 , a cylinder 3 formed in said rotating body 2, a piston 4 disposed in the cylinder 3, and a cam ring 5, in which the rotating body 2 is adapted to rotate on a first axis A-A, in which the axis B-B of the cylinder 3 is radially arranged about the first axis A-A such that the piston 4 is urged away from the first axis A-A by a centrifugal force, in which the cam ring 5 comprises a stationary guide surface 6 adapted to act against the piston 4 such that it follows an eccentric path about the first axis A-A and travels up and down the cylinder 3 at least once in every 360 degrees of rotation of the rotating body 2. Either piston return or working stroke may be due to centrifugal force.

Description

COMPRESSOR

This invention relates to a compressor, for use particularly, but not exclusively, to compress gases to 10 Bar (150 psi).

Compressed gas is used in many different industrial applications, however considerable energy is required to compress gas, which makes it expensive to produce and to purchase. Further the large amount of energy required has an impact on the environment in the form of carbon emissions.

Many processes also comprise a gas compression stage, In which a gas at a certain pressure is compressed to a higher pressure for a particular purpose. In such situations it is important that the work rate of the compressor remains constant when the output pressure increases. However, with most known compressors this is not the case. For example, the work rate of a standard 10 cfm (16.99 cmph) compressor drops to just 3 cfm (5.1 cmph) when the output pressure is 10 Bar. In other words, the higher the work load the slower the compressor operates. As such, when 10 cfm of gas has to be compressed to 10 Bar a large capacity compressor is required which is capable of compressing far more than 10 cfm of gas at atmospheric pressure. As such, for some of the time the capacity of the compressor might be redundant.

Part of the reason for the relative inefficiency of known compressor designs is their complexity and excess of moving parts. For example, where the compressor comprises a piston which moves in a reciprocal action inside a cylinder, energy is lost through the movement of a crank and con rod, and the reciprocal action is inherently inefficient because energy is required to slow and stop the piston at each end of its stroke.

One further problem with some known compressors is that they use lubricating oil exposure to which can perish certain fluids.

The present invention is intended to overcome some of the above problems by providing a novel approach.

Therefore, according to the present invention a compressor comprises a rotating body, a cytinder formed in said rotating body, a piston disposed in the cylinder, and a cam ring, in which the rotating body is adapted to rotate on a first axis, in which the axis of the cylinder is radially arranged about the first axis such that the piston is urged away from the first axis by a centrifugal force, in which the cam ring comprises a stationary guide surface adapted to act against the piston such that it follows an eccentric path about the first axis and travels up and down the cylinder at least once in every 360 degrees of rotation of the rotating body.

Therefore, the compressor of the invention utilises a generated centrifugal force to drive a piston up and down a cylinder to perform a compression function.

This arrangement is advantageous because while the motion of the piston inside the cylinder is reciprocal, this motion Is facilitated by the rotation of the cylinder about the first axis, so there are none of the mechanical drawbacks usually associated with generating a reciprocating action. In particular, no energy is lost through the movement of a crank or a con rod, as these parts are dispensed with, and there is no energy drain associated with stopping the piston dead at each end of its stroke in order to send it in the opposite direction. The compressor of the invention can also operate without any lubricating oil.

The invention can be performed in various ways, and in one embodiment the cylinder can be arranged with its compression chamber radially outside the piston.

With this arrangement the generated centrifugal force urges the piston to the head of the cylinder, and the guide surface can act against the piston to drive it to the bottom of the cylinder against the centrifugal force. With such a configuration a linkage of some sort must be provided between the guide surface and the piston, because the cam ring cannot enter the compression chamber to allow the guide surface to act against the piston directly.

Therefore, in a preferred arrangement the compression chamber of the cylinder can be arranged between the first axis and the piston. As such the generated centrifugal force urges the piston to the bottom of the cylinder, and the guide surface can act against the piston to drive it to the head of the cylinder against the centrifugal force.

It is not an essential feature of the invention that the guide surface acts directly against the piston, as it is possible to have some kind if linkage between these components if required for any reason, but in a preferred embodiment the guide surface can be disposed in the rotational path of the cylinder and can be adapted to act directly against the back of the piston.

It is theoretically possible for the first axis to pass through the compression chamber, provided that more than half of the weight of the piston is always disposed on one side of the first axis so the piston is always urged away from the first axis.

However, preferably the cylinder can be spaced apart from the first axis such that it follows an orbital path about the first axis.

This configuration is advantageous because it allows for two or more cylinders to be provided in the rotating body, and in a preferred construction this is so. Each of the two or more cylinders can be provided with a piston, and the two or more cylinders can be radially arranged about the first axis and can follow the same orbital path about it. Further, the cam ring can be adapted to act against the two or more pistons such that they follow the same eccentric path about the first axis and travel non-synchronously up and down their corresponding cylinder at feast once in every 360 degrees of rotation. With this arrangement the compressor can provide a constant output, because one or more cylinders can be performing an exhaust stroke while others can be performing an inlet stroke. In addition, this arrangement allows for the energy used to turn the rotating body to be utilised as efficiently as possible.

The rotating body can comprise a common inlet chamber arranged on said first axis, and a separate inlet aperture can lead from the common inlet chamber into each of the two or more cylinders. Further, the rotating body can comprise a common outlet chamber, and a separate outlet aperture can lead from each of the two or more cylinders into the outlet chamber. A non-return inlet valve can be disposed in each of the inlet apertures, and a non-return outlet valve can be disposed in each of the outlet apertures.

In one version of the invention the non-return inlet valves can each comprise a valve body radially movable in relation to the first axis, and urged away from the first axis by the centrifugal force, and the compressor can comprise a valve cam ring comprising a stationary valve guide surface adapted to act against the valve bodies such that they follow an eccentric path about the first axis and open their inlet valve when the corresponding piston performs an inlet stroke, and close their inlet valve when the corresponding piston performs an exhaust stroke.

As such, the movement of the valve bodies can be controlled in the same way as the movement of the pistons. As with the pistons, it is possible for the valve cam ring to act directly against the valve bodies, however, in a preferred construction the valve cam ring can be disposed radially outside of the rotational path of the inlet valves, and a push rod can be disposed between the valve guide surface and each of the valve bodies.

However, in an alternative and more simple construction the non-return inlet va'ves can each comprise a spring loaded ball valve.

It is possible for the non-return outlet valves to also comprise valve bodies which are urged away from the first axis by the centrifugal force and which are forced to travel along an eccentric path by a valve cam ring, however, in a preferred construction the non-return outlet valves each comprise a spring loaded ball valve.

The cylinders can be provided with a ceramic surface, such that as little heat is built up during operation as possible. The pistons can have a clearance in the cylinder of 0.5 thousandths of an inch (1.27 thousandths of a cm), which ensures adequate compression.

Preferably each piston can be provided with a domed back adapted to bare against the guide surface. This ensures that the contact area between the piston and the guide surface is as large as possible to prevent the build up of heat and pressure.

In a preferred construction the cam ring can be adapted to act against each piston such that it travels up and down its corresponding cylinder twice in every 360 degrees of rotation of the rotating body.

In terms of the number of pistons provided, this can in theory be any number, but it has been found that 12 or eight cylinders works well. Preferably eight cylinders can be provided, each one disposed at 45 degrees to the next. With this configuration two pairs of cylinders will be at different exhaust states while the other two pairs of cylinders will be at different inlet states, ensuring the compressor provides a smooth constant output.

The compression ration of the compressor is preferably 10:1, so air drawn from atmosphere can be compressed to 10 Bar. It will be appreciated that the compression ratio can be altered by changing the size or number of cylinders, and the rotation speed of the rotating body.

The compressor can comprise an outer body comprising a rotation chamber therein. The rotating body can be supported for rotation inside the rotation chamber by one or more bearings, and the cam ring can be mounted to a surface of the rotation chamber. When a valve cam ring is provided it too can be mounted to the surface of the rotation chamber.

The rotating body can comprise an outer portion which extends beyond the rotation chamber, and the common Inlet chamber can be formed inside the rotating body and can extend into said outer portion. Further, a plurality of outer inlet apertures can be provided in the outer portion which are radially arranged about the first axis.

In one version of the invention the rotating body can comprise an inlet fan adapted to direct fluid into the outer inlet apertures. Such a feature can be provided if the action of the compressor does not draw sufficient fluid in through the outer inlet apertures.

Preferably the rotating body can be adapted to be rotated on the first axis by a motor, and can be provided with suitable linkages and so on. The motor can be adapted to rotate the rotating body at substantially 3000 revolutions per minute.

When there are eight cylinders each performing four strokes per revolution as described above, this results in 800 strokes per second. As such, a compressor of the invention is very high speed very high pressure compressor which is small in size in relation to known compressors of a comparable output.

The present invention can be performed in various ways, but two embodiments will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional side view of a first compressor according to the present invention; Figure 2 is a cross-sectional end view of the compressor as shown in Figure 1; Figure 3 is a cross-sectional partial side view of the compressor shown in Figure 1 in a first condition; Figure 4 Is a cross-sectional partial side view of the compressor shown in Figure 1 in a second condition; Figure 5 is a cross-sectional partial side view of the compressor shown in Figure 1 in a third condition: and Figure 6 is a cross-sectional side view of a second compressor according to the present invention.

Therefore, as shown in Figure 1 a compressor 1 comprises a rotating body 2, a cylinder 3 formed in said rotating body 2, a piston 4 disposed in the cylinder 3, and a cam ring 5. The rotating body 2 is adapted to rotate on a first axis A-A, and the axis of the cylinder B-B is radially arranged about the first axis A-A such that the piston 4 is urged away from the first axis A-A by a centrifugal force. The cam ring 5 comprises a stationary guide surface 6 adapted to act against the piston 4 such that it follows an eccentric path about the first axis A-A and travels up and down the cylinder 3 at least once in every 360 degrees of rotation of the rotating body 2.

The compressor 1 actually comprises eight cylinders 3, 7-13, which are radially arranged about the first axis A-A at 45 degree intervals, as shown in Figure 2.

(Each of the cylinders 3, 7-13 is identical, so the same reference numerals are used herein for like components and features.) As is also clear from Figure 2, the cylinders 3, 7-13 are arranged with their compression chambers 14 arranged between the first axis A-A and their pistons 4. As such, the centrifugal force generated when the rotating body 2 is rotated urges the pistons 4 to the bottom 15 of the cylinders 3, 7-13, and the guide surface 6 acts against the pistons 4 to drive them to the head 16 of the cylinders 3, 7-13 against the centrifugal force. The cylinders 3, 7-13 are spaced apart from the first axis A-A, such that they each follow the same orbital path about it when the rotating body 2 is rotated.

The guide surface 6 acts directly against the back 17 of the pistons 4, which are domed so as to provide the greatest contact area between the piStons 4 and the guide surface 6 as the pistons 4 rotate. In particular, referring to Figure 2, the piston 4 in cylinder 3 is squarely aligned against guide surface 6, and a top section of the dome shape Is in contact with the guide surface 6. However, piston 4 in cylinder 7 is aligned at an oblique angle against the guide surface 6, and a right hand side section of the dome shape is in contact with the guide surface 6. Piston 4 in cylinder 8 is squarely aligned against the guide surface 6, however the curvature of the guide surface 6 at that point is shallower than at the top, so a smaller portion of the top section of the dome shape is in contact with the guide surface 6. Piston 4 in cylinder 9 is aligned at an oblique angle against the guide surface 6, so a left hand side section of the dome shape is in contact with the guide surface 6. Piston 4 in cylinder is in the same position as piston 4 in cylinder 3. Therefore, as the pistons 4 rotate, the contact area between their backs 17 and the guide surface 6 changes, but most importantly, as the backs 17 are dome shaped there are no hot spots, which would occur if the backs 17 were squared off.

The cylinders 3, 7-13 are provided with a ceramic surface lining 18, such that as little heat is built up during operation as possible. (The ceramic surface lining 18 is not shown in Figures 1 and 3 to 6, but it is present.) The pistons 4 have a clearance in the cylinders 3, 7-13 of 0.5 thousands of an inch, which ensures adequate compression.

As is also clear from Figure 2, the guide surface 6 is symmetrical, such that the pistons 4 travel up and down their corresponding cylinders 3, 7-13 twice In every 360 degrees of rotation of the rotating body 2. As such there are four pairs of cylinders which are opposite to one another and which are in the same state. In the position shown in Figure 2 the pistons 4 in cylinders 3 and 10 are both at the bottom of the cylinder, and the pistons 4 in cylinders 8 and 12 are both at the head 16 of the cylinder. If the rotating body 2 is rotating In a clockwise direction pIstons 4 in cylinders 7 and 11 are travelling towards the head 16 of the cylinder in an exhaust stroke, and the pistons 4 in cylinders 9 and 13 are travelling towards the bottom 15 of the cylinder in an inlet stroke. With this arrangement the compressor 1 provides a constant smooth output, because at all points of rotation at least two and usually four cylinders are performing an exhaust stroke.

Referring back to Figure 1, the rotating body 2 comprises a common inlet chamber 19 formed within it and arranged on said first axis A-A. Separate inlet apertures 20 lead from the common inlet chamber 19 into each of the cylinders 3, 7- 13. Further, the rotating body 2 comprises a common outlet chamber 21 formed within it and also arranged on said first axis A-A. Separate outlet apertures 22 lead from each of the cylinders 3, 7-13 into the outlet chamber 21. Non-return inlet valves 23 are disposed in each of the inlet apertures 20, and non-return outlet valves 24 are disposed in each of the outlet apertures 22.

The non-return inlet valves 23 comprise a valve body 25 which is radially movable in relation to the first axis A-A, and which is urged away from the first axis A-A by the centrifugal force. The valve bodies 25 are disposed in housings 26 provided between the first axis A-A and the inlet apertures 20. The housings 26 are aligned with each cylinder 3, 7- 13 so they are also radially arranged about the first axis A-A at degree intervals.

A valve cam ring 27 comprising a valve guide surface 28 acts against the valve bodies 25 Such that they follow a symmetrical eccentric-like path about the first axis A-A, similar to that followed by the pistons 4. However, the valve cam ring 27 is not shaped in a completely curve-linear fashion like cam ring 5, rather it has four distinct sections, each of which is generally circumferential about the first axis A-A.

This Is so the valve bodies 25 stay In the same position during parts of the rotation.

Curve-linear ramp sections link these four sections together. The valve cam ring 27 is shaped and orientated such that the valve bodies 25 are forced towards the first axis A-A and keep the inlet valves 23 open when the corresponding piston 4 is travelling down the cylinder in an inlet stroke, and are allowed to move away from the first axis A-A to keep the inlet valves 23 closed when the corresponding piston 4 is travelling up the cylinder in an exhaust stroke.

Unlike with the pistons 4, the valve guide surface 28 does not act directly against the valve bodies 25. rather push rods 29 are disposed therebetween to transmit the desired movement. In addition, the valve bodies 25 are spring loaded by springs 30 disposed in the housings 26. The sprIngs 30 ensure that the valve bodies do not lift off the push rods 29 when they are forced towards the first axis A-A in use, and that the inlet valves 23 remain closed when the rotating body 2 is stationary.

The non-return outlet valves 24 comprise spring loaded ball valves 31, which are forced open by the compression force generated when the pistons 4 travel up the cylinder in an exhaust stroke, and which are forced closed by the negative pressure generated when the pistons 4 travel down the cylinder in an inlet stroke, and by the springs 32.

The compressor 1 comprises an outer body 33 which comprises a rotation chamber 34 thereIn. The rotating body 2 Is supported for rotation inside the rotation chamber 34 by two roller bearings 35 and 36. Both the cam ring 5 and the valve cam ring 27 are mounted inside the rotation chamber 34. The cam ring 5 is mounted inside slot 37, and the valve cam ring 27 is mounted inside slot 38.

The rotating body 2 comprises an outer portion 39 which extends beyond the rotation chamber 34, and out of the outer body 33. The common inlet chamber 19 extends into said outer portion 39, and a plurality of outer inlet apertures 40 are provided in the outer portion 39, which are radially arranged about the first axis A-A.

The outer body 33 is provided with a annular inlet concavity 41 which is radially arranged outside of the outer portion 39, and which allows the passage of fluid from outside the compressor 1 into the outer outlet apertures 40.

The outer portion 39 is provided with connection means 42, which facilitates its connection to a motor (not shown), which rotates the rotating body 2 on the first axis A-A.

The compressor 1 can be used to compress any fluid, and it is provided with connection means (not shown) to connect it to a supply of fluid to be compressed, and to a reservoir to contain the resulting compressed fluid. However, in the following description the compressor 1 is used to compress air fl-am atmosphere to 10 Bar. As such, the annular inlet concavity 41 is exposed to atmosphere, and a reservoir is connected via an appropriate linkage to the common outiet chamber 21.

The motor (not shown) is adapted to rotate the rotating body 2 on the first axis at 3000 revolutions per minute, which is 50 revolutIons per second. As each piston 4 performs 4 strokes per revolution, and there are 8 cylinders 3, 7-13, the compressor 1 as a whole performs 800 strokes per second. As such, the compressor 1 is a very high speed and very high pressure compressor for its size.

As stated above, the compression ratio of the compressor I is 10:1, so the cylinders 3, 7-13 are sized to perform such compression when run at the above speed.

Therefore, the compressor 1 operates as follows. The motor (not Shown) Is operated and the rotating body 2 is rotated inside the rotation chamber 34 on the roller bearings 35 and 36. The motor (not shown) rotates the rotating body 2 at 3000 revs per minute, which generates a centrifugal force which urges the pistons 4 away from the first axis A-A and against the cam ring 5, so they follow the eccentric path of the guide surface 6.

Referring to Figure 2, in each full revolution each piston 4 in each of the cylinders 3, 7-13 performs four strokes. For example, from the position shown in Figure 2 piston 4 in cylinder 3 performs an exhaust stroke, an inlet stroke, an exhaust stroke and a further inlet stroke. This is as a result of the eccentric symmetrical shape of the cam ring 5, and the manner in which the guide surface 6 acts against the back 17 of the pistons 4. As the backs 17 of the pistons 4 are domed in shape the contact area between the pistons 4 and the guide ring 6 changes through the full revolution of the rotating body 2, but remains large so no hot spots are generated. The ceramic lining 18 provIdes an efficient bearing surface inside the cylinders 3, 7-13, and the pistons 4 move up and down without generating too much heat or friction.

As the rotating body 2 rotates the inlet valves 23 open and close in time with the strokes of the piston. In particular, the valve cam ring 27 acts against the valve bodies 25 such that the inlet valves 23 are open when the pistons 4 are performing an inlet stroke, and closed when the pistons 4 are performing an exhaust stroke.

Figure 3 shows cylinder 3 at a point a few degrees before its position in Figure 2. At this point the piston 4 is nearing its lowest point in the cylinder 3 because the guide surface 6 at that point of rotation is nearing its furthest point from the first axis A-A. As such, the piston 4 is nearing the end of an inlet stroke, where it is drawing air into the cylinder 3 from the common inlet chamber 19. At this point the inlet valve 23 is open because the valve guide surface 28 at that point of rotation comprises a section which is near the first axis A-A. As such the valve body 25 is pushed down into the housing 26 against the force of the spring 30, and the inlet aperture 20 Is open.

At this point the outlet valve 24 is closed because of the negative pressure generated by the inlet stroke of the piston 4, arid by the spring 32.

As the inlet aperture 20 is open, and the piston 4 is performing an inlet stroke, air is drawn into the cylinder 3 from the common inlet chamber 19. As such, air is also drawn into the common inlet chamber 19 from atmosphere through the outer inlet apertures 40. However, in addition to this piston generated suction, the rotation of the rotating body 2 at the above described speed also creates suction through the outer inlet apertures 40. They are shaped such that their high-speed rotation draws air therethrough. In addition to this, air inside the common inlet chamber 19 is rotated by tile motion of the rotating body 2, and is urged outwards by a centrifugal force, which urges it through the inlet apertures 20. Therefore, the compressor 1 is constructed such that the cylinders 3, 7- 13 are provided with a positive pressure of air for the pistons 4 to draw therein.

Figure 4 shows the cylinder 3 at a point a few degrees after its position in Figure 2. At this point the piston 4 has just begun travelling up the cylinder 3, because it has passed the point of the guide surface 6 which is furthest from the first axis A-A. As such, the piston 4 has begun an exhaust stroke, and it is pumping air from the cylinder 3 into the common outlet chamber 21. At this point the inlet valve 23 is closed because the valve guide surface 28 at that point of rotation comprises a section which is further away from the first axis A-A than the section shown in Figure 3. As such the valve body 25 has been allowed to travel radially away from the first axis A-A and it has done so as a result of the centrifugal force and the force of the spring 30. At this point the outlet valve 24 is open because of the pressure generated inside the cylinder 3 by the compression of the piston 4.

Figure 5 shows the cylinder 3 at a point 45 degrees after its position shown in Figure 2. At this point the guide surface 6 is at its nearest to the first axis A-A. so the piston 4 has completed its exhaust stroke, and is about to start an Inlet stroke. At this point the outlet valve 24 is still open as the last of the air inside tile cylinder 3 is travelling out of the outlet aperture 22 into the common outlet chamber 21. However, the inlet valve 23 has already begun to open because the valve guide surface 28 at that point of rotation comprises a ramo section between circumferential sections.

and the valve body 25 is travelling towards the first axis A-A. As such, as soon as the piston 4 begins to travel back down the cylinder 3 in an inlet stroke, air wilt be drawn through the inlet aperture 20 into the cylinder 3. It will be appreciated that the exact timing of the movement of the inlet valve 23 can be set to its optimum by the man skilled in the art by shaping the valve guide surface 28.

The same actions are performed by each piston 4 in each of the cylinders 3, 7-13 in turn as they rotate, and the compressor 1 compresses the air drawn from atmosphere to 10 Bar in a smooth and constant manner.

The above described embodiment can be altered without departing from the scope of Claim 1. In particular, in one alternative embodiment shown in Figure 6, a compressor 60 is the same as compressor 1 described above, except that the inlet valves 61 are spring loaded ball valves 62 instead of the valve body arrangement in compressor 1. As such, when the pistons 63 travel down the cylinders 64 in an inlet stroke the ball valves 62 are forced open by the generated negative pressure, and when the pistons 63 travel up the cylinders 64 in an exhaust stroke the ball valves 62 are forced closed by the generated pressure, and by the force of the springs 65.

This arrangement is obviously simpler than that Shown in Figure 1, and it has been found that it works well.

In another alternative embodiment (not shown) a compressor is the same as compressor 1 described above, except that the non-return outlet valves are similar in construction to the non-return inlet valves, and comprise valve bodies which are urged away from the first axis by the centrifugal force and which are forced to travel along an eccentric path by a valve cam ring, In another alternative embodiment (not shown) a compressor is the same as compressor 1 described above, except that the rotating body comprises an inlet fan on its outer portion which is arranged on the first axis, and is adapted to direct fluid into the outer inlet apertures when the rotating body rotates. This feature works like a mini supercharger to help to ensure that the cylinders are provided with sufficient quantities of air to operate effectively.

In one other alternative embodiment (not shown) a compressor can operate according to similar principals to those described above, but the cylinder or cylinders are arranged with the compression chamber radially outside the piston. As such, the centrifugal force urges the piston to the head of the cylinder, and the guide surface acts against the piston to drive it to the bottom of the cylinder against the centrifugal force.

Therefore, the invention provides a compressor which utilises a generated centrifugal force to drive pistons up and down a cylinder. As such a plurality of reciprocating pistons are continuously operated without many of the mechanical drawbacks usually associated with generating such actions. In particular, no energy is lost through the movement of a crank or a con rod, as these parts are dispensed with, and there is no energy drain associated with stopping the piston dead at each end of its stroke in order to send it in the opposite direction. As a result the compressor of the invention is capable of maintaining high flow rates when the output pressure increases. In particular, the compressor of the invention can maintain a 10 cfm flow rate with an output pressure of 10 Bar using far less driving energy than comparable known compressors. In addition to this above, the compressor of the invention can be used to compress substances which perish when exposed to exposed to oils, as it uses none.

Claims

Claims 1. A compressor comprising a rotating body, a cylinder formed in said rotating body, a piston disposed in the cylinder, and a cam ring, in which the rotating body is adapted to rotate on a first axis, in which the axis of the cylinder is radially arranged about the first axis Such that the piston is urged away from the first axis by a centrifugal force, in which the cam ring comprises a stationary guide surface adapted to act against the piston such that it follows an eccentric path about the first axis and travels up and down the cylinder at least once in every 360 degrees of rotation of the rotating body.
2. A compressor as claimed in Claim 1. in which a compression chamber of the cylinder is arranged between the first axis and the piston.
3. A compressor as claimed in Claim 2 in which the guide surface is disposed in the rotational path of the cylinder and is adapted to act directly against the piston.
4. A compressor as claimed in any of Claims 1 to 3 in which the cylinder is spaced apart from said first axis such that is follows an orbital path about the first axis.
5. A compressor as claimed in Claim 3 in which two or more cylinders are formed in the rotating body, each of which is provided with a piston, in which the two or more cylinders are radially arranged about the first axis and follow the same orbital path about the first axis, in which the cam ring is adapted to act against the two or more pistons such that they follow the same eccentric path about the first axis and travel non-synchronously up and down their corresponding cylinder at least once in every 360 degrees of rotation.
6. A compressor as claimed in Claim 5 in which the rotating body comprises a common inlet chamber arranged on said first axis, in which a separate inlet aperture leads from the common inlet chamber into each of the two or more cylinders, in which the rotating body comprises a common outlet chamber, and in which a separate outlet aperture leads from each of the two or more cylinders into the outlet chamber.
7. A compressor as claimed in Claim 6 in which a non-return inlet valve is disposed in each of the inlet apertures, and in which a non-return outlet valve is disposed in each of the outlet apertures.
8. A compressor as claimed in Claim 7 in which the non-return inlet valves each comprise a valve body radially movable in relation to the first axis, and urged away from the first axis by the centrifugal force, in which the compressor comprises a valve cam ring comprising a stationary valve guide surface adapted to act against the valve bodies such that they follow an eccentric path about the first axis and open their inlet valve when the corresponding piston performs an inlet stroke, and close their inlet valve when the corresponding piston performs an exhaust stroke.
9. A compressor as claimed in Claim 8 in which the valve cam ring is disposed radially outside of the rotational path of the inlet valves, and in which a push rod is disposed between the valve guide surface and each of the valve bodies.
10. A compressor as claimed in Claim 7 in which the non-return inlet valves each comprise a spring loaded ball valve.
11. A compressor as claimed in any of Claims 8 to 10 in which the non-return outlet valves each comprise a spring loaded ball valve.
12. A compressor as claimed in any of Claims 5 to 11 in which the two or more cylinders are provided with a ceramic surface.
13. A compressor as claimed in any of Claims 5 to 12 in which each piston is provided with a domed back adapted to bare against the guide surface.
14. A compressor as claimed in any of Claims 5 to 13 in which the cam ring is adapted to act against each piston such that it travels up and down its corresponding cylinder twice in every 360 degrees of rotation of the rotating body.
15. A compressor as claimed in Claim 14 in which eight cylinders are provided, each one disposed at 45 degrees to the next.
16. A compressor as claimed in any of the preceding Claims in which the compressor comprises an outer body comprising a rotation chamber therein, in which the rotating body is supported for rotation inside the rotation chamber by one or more bearings, and in which the cam ring is mounted to a surface of the rotation chamber.
17. A compressor as claimed in Claim 16 when dependent on Ctaim 8 or 9 in which the valve cam ring is mounted to said surface of the rotation chamber.
18. A compressor as claimed in Claim 16 or 17 when dependent on any of Claims 6 to 11, or Claims 12 to 15 when dependent on any of Claims 6 to 11, in which the rotating body comprises an outer portion which extends beyond the rotation chamber, in which the common inlet chamber is formed inside the rotating body and extends into said outer portion, and in which a plurality of outer inlet apertures are provided in the outer portion which are radially arranged about the first axis.
19. A compressor as claimed in Claim 18 in which the rotating body comprises an inlet fan adapted to direct fluid into the outer inlet apertures.
20. A compressor as claimed in any of the preceding Claims in which the rotating body is adapted to be rotated on the first axis by a motor.
21. A compressor as claimed in Claim 20 in which the motor is adapted to rotate the rotating body at substantially 3000 revolutIons per minute.
22. A compressor substantially as described herein and as shown in the accompanying drawings.