GB2334760A

GB2334760A - Vane pumps or motors

Info

Publication number: GB2334760A
Application number: GB9822081A
Authority: GB
Inventors: David Bostock-Smith
Original assignee: KIT SYSTEMS Ltd
Current assignee: KIT SYSTEMS Ltd
Priority date: 1997-10-16
Filing date: 1998-10-12
Publication date: 1999-09-01
Also published as: GB9721816D0; DE19848307A1; GB9822081D0

Abstract

A motor or pump includes a central housing 11 containing a chamber 17 having inlet and outlet ports 23 and 24. A rotor 18 is contained within the chamber 17 for rotation about an axis 22. The rotor 18 comprises a rotor body having a cylindrical outer surface. Radially extending vanes or blades 21 are contained in slots 20 in the rotor body 19 and engage the wall of the chamber 17. The wall of the chamber 17 includes a first portion 26 which has the same radius of curvature as the outer surface of the rotor body and is struck from the axis 22. The wall of the chamber 17 also includes a second portion 27, which is opposite to the first portion 26 and has a radius of curvature greater than that of the first portion 26 and is struck from the same axis 22.

Description

MOTORS AND PUMPS Field of the Invention This invention relates to motors and pumps and, although it has been developed in relation to pneumatically operated motors, it is also applicable to hydraulic motors and to both hydraulic and pneumatic pumps, including vacuum pumps.

Pneumatic vane motors are well known. These comprise a vaned rotor arranged for rotation within a chamber with the vanes in the form of blades which are arranged for radial movement relative to the rotor so as to maintain sealing engagement with the wall of the chamber. The chamber has inlet and outlet ports and is normally of true cylindrical form with the rotor arranged for rotation about an axis offset from the axis of the cylinder.

Such motors normally operate reliably but, because of the considerable loads to which the vanes or blades can be subjected, substantial wear of the vanes or blades often occurs, resulting in significant maintenance costs.

It is accordingly an object of the present invention to provide an improved form of motor or pump, particularly an improved form of pneumatic vane motor.

Summarv of the Invention According to the present invention there is provided a motor or pump which comprises: a) a housing containing a chamber having inlet and outlet ports, and b) a rotor arranged for rotation within the chamber about a primary axis, c) said rotor comprising a rotor body having a cylindrical outer surface and a plurality of vanes or blades which are located in slots in the rotor and movable radially relative to said primary axis, and said chamber having a wall which is engaged by the radially outer ends of the vanes or blades and includes a first wall portion which has substantially the same radius of curvature as the cylindrical outer surface of the rotor and is struck from said primary axis so as to provide a seal between the inlet and outlet ports, e) said wall of the chamber also including a second wall portion corresponding to the "power" part of a cycle of rotation of the rotor, which second wall portion has a radius of curvature greater than that of said first wall portion and is also struck from said primary axis.

The first wall portion preferably extends to either side of that part of the wall of the chamber corresponding to the top dead centre position of the rotor. The vanes or blades will thus be moved into their radially innermost positions by the time that the rotor reaches a position prior to its top dead centre position and will remain in their innermost positions through a predetermined part of a cycle of the rotor. This part of the cycle of the rotor may extend, for example, through 15 to either side of the top dead centre position.

The second wall portion preferably extends to either side of the position corresponding to the bottom dead centre position of the rotor, for example, through 60 to either side of the bottom dead centre position of the rotor. The fact that said second wall portion is also centred on the primary axis, i.e. the axis of rotation of the rotor, means that there will be no sliding of the vanes or blades in their mounting slots in the rotor when the rotor moves through this part of its cycle to either side of its bottom dead centre position and the degree of wear of the tip and flank of each vane or blade will be substantially reduced.

Because the vanes or blades are not required to slide when under the load which is applied to them during the "power" part of a cycle, higher bending moments are practicable. This means that the vanes or blades can be made thinner or of more flexible materials than has heretofore been possible. Alternatively, larger throws may be achieved without the danger of excessive wear of the vanes or blades, giving an increased swept volume and hence an increased power to weight ratio.

This arrangement further ensures that the relative geometry between the tip of each vane or blade remains constant during the "power" part of a cycle of rotation of the motor. The oil film which both lubricates and assists sealing will thus be less liable to disturbance and breakdown than would otherwise be the case. In addition, the output torque obtained using a pneumatic or hydraulic motor will be more constant than with existing designs using eccentric cylinders.

There are preferably third and fourth portions of the wall of the chamber to either side of the top dead centre portion, said third and fourth portions each being struck off a common axis spaced downwardly from said primary axis and having a radius of curvature intermediate that of the top dead centre wall portion and the bottom dead centre wall portion, said third and fourth wall portions merging smoothly will the top dead centre and the bottom dead centre wall portions.

Cam means are preferably provided for biasing each of the vanes or blades radially outwardly to the required extent throughout a cycle of rotation of the rotor. Pneumatic means may alternatively or additionally be provided for effecting radially outward biasing of the vanes or blades. Of course, when the rate of rotation of the rotor is significant, radially outward displacement of the vanes or motors will be effected by centrifugal action. An advantage of this arrangement is that the vanes or blades cannot fall back into their slots under the action of gravity, for example, thus making starting difficult and/or seriously reducing the starting torque. There is also no requirement for the provision of spring action to maintain the tips of the vanes or blades in contact with the wall of the chamber.

There is thus a reduction in the likelihood of adhesion of an edge of a vane or blade to the wall of the chamber should there be any local corrosion or any chemical reaction take place when the motor has been stationary for some time. Consequent starting problems are thus avoided.

The housing is preferably formed from three main components, i.e. a centre member of generally cylindrical form of which the internal surface provides the chamber wall having the configuration referred to above and a pair of end members which have inwardly facing surfaces shaped to provide the cam means which engage the radially inner ends of the vanes or blades and at least one of which is provided with a generally kidney-shaped air supply port for the provision of air under pressure to achieve the required radially outward displacement of the vanes or blades. The end members of the housing will preferably also include recesses in which bearing assemblies are located for providing effective support of the rotor.

Brief Descrintilon of the Drawings Figure 1 is a longitudinal sectional view of a motor, Figure 2 is a transverse sectional view of the motor, Figure 3 is a side view of the motor rotor, Figure 4 is an end view of the motor cylinder, i.e. the central member of the motor housing, Figure 5 is a sectional view of one end member of the motor housing, and Figure 6 is an inside view of the end member shown in Figure 5.

Descrintion of the Preferred Embodiment As shown in Figure 1, a motor housing 10 comprises three main components, namely a central generally cylindrical member 11 and a pair of end members 12 and 13. Sealing members 14 and 15 are located between the abutting faces of the end members 12 and 13 and the central member 11, and the components of the housing 10 are held together by means of bolts 16.

The central member 11 contains a chamber 17, the detailed configuration of which is described below, and a rotor 18, the configuration of which is shown in Figure 3, is arranged for rotation relative to the housing 10. The rotor 18 includes a main body portion 19, which is formed with four equi-angularly spaced, radially extending slots 20 in which radially movable vanes or blades 21W, 21X, 21Y and 21Z are mounted. The main body portion 19 of the rotor 18 has a cylindrical outer surface having a central axis 22 and the rotor 18 is rotatable about this central axis 22.

The chamber 17 has inlet and outlet connections 23 and 24, to one of which air is supplied under pressure and from the other of which air is exhausted. It will be appreciated that either connection 23, 24 can be the inlet connection, while the other connection will be the outlet connection depending on the direction in which it is desired to drive the rotor 18.

As shown in the drawings, the rotor 18 is rotatable relative to the housing 19 passing through a top dead centre position (as shown in Figure 1) in which one of the vanes or blades 21 extends vertically, in either direction depending on which of the two connections 23 and 24 is the inlet. It will be assumed, for the purpose of the following description that connection 23 is the inlet connection and that it is desired to drive the rotor 18 in the clockwise direction as viewed in Figure 2.

The internal configuration of the chamber 17 can best be seen from Figure 4, which shows the axis of rotation 22 of the rotor 18. The top dead centre position of the chamber is indicated at 25, and is located directly above the axis 22. The internal wall of the chamber 17 is afforded by four wall portions 26, 27, 28 and 29. The first wall portion 26 has its axis coinciding with the axis 22 and has a radius of curvature R1, which corresponds to, i.e. is the same as, the radius of curvature of the outer surface of the rotor 18. The first wall portion 26 extends through 15 to either side of the top dead centre position 25, i.e. the first wall portion 26 has a total angular extent of 30".

The second wall portion 27 also has its axis coinciding with the axis 22 and has a radius of curvature R2, which is greater than R1. The second wall portion 27 extends through 60 to either side of the bottom dead centre position, i.e. it has a total angular extent of 1200.

The first wall portion 26 is connected to the second wall portion 27 by the third and fourth wall portions 28 and 29, which have their axis of curvature at a point 30 immediately below axis 22.

The radius of curvature of each of the third and fourth wall portions 28 and 29 is R3, which is intermediate R1 and R2 and is such that the third and fourth wall portions 28 and 29 merge smoothly into the first and second wall portions 26 and 27.

If one considers the space between vanes 21X and 21Y, as shown in Figure 2, which space is connected to the inlet 23 and is thus supplied with compressed air, it can readily be seen that the vane 21X projects further from its slot 20 than the vane 21Y and is thus subject to a greater force, i.e. pressure times area exposed to the pressure, than vane 21Y. The rotor 18 will thus be caused to rotate in the clockwise direction as viewed in Figure 2.

It will also be seen that, when the rotor 18 is in the position shown in Figure 2, the vane 21X is in contact with the second wall portion 27 and will remain in contact with the second wall portion 27 at least until it reaches the position previously occupied by vane 21W at which it is communication with the outlet 24. Thus, during the part of the cycle of the rotor 18 for which a force is applied to rotor 18, vane 21X will not be moving radially. This part of the cycle corresponds to the "power" part of the cycle and this means that higher bending moments are practicable, with the consequent further advantages referred to above.

Looking next at the top dead centre position of the rotor 18, it will be seen from Figure 2 that, when the rotor turns from this position and the vane 21Z moves from the position shown in Figure2, the vane 21Z will be displaced radially inwardly until, by the time that it reaches the top dead centre position, it will be fully retracted. The contact of the rotor 18 and the tip of the vane 21Z with wall portion 26 will ensure that a positive seal is obtained preventing direct communication between the inlet and outlet ports 23 and 24. The fact that the vane 21Z does not move radially while it travels through the top dead centre position will enhance the effectiveness of the seal. Air bleed channels 30 and 31 are provided on either side of the top dead centre position of the chamber 17.

Bearing assemblies 32 and 33 are provided within the end members 12 and 13 for supporting the rotor 18 and for ensuring that it rotates about the axis 22. The end faces of the end members 12 and 13 are provided with cam formations 34 for engagement with the end portions of the vanes 21 to ensure that the vanes 21 are moved radially outwardly of their slots 20 into engagement with the second, third and fourth wall portions 27, 28 and 29.

An optional air ejection slot 35 may also be provided.

Although the invention has been described in detail above with reference to a compressed air motor, the invention is equally applicable to hydraulic motors and to pumps, either pneumatic or hydraulic pumps, in which the motor is driven and air or hydraulic fluid is drawn in through the inlet and discharged under pressure through the outlet.

Claims

Claims:

1. A motor or pump which comprises: a) a housing containing a chamber having inlet and outlet ports, and b) a rotor arranged for rotation within the chamber about a primary axis, c) said rotor comprising a rotor body having a cylindrical outer surface and a plurality of vanes or blades which are located in slots in the rotor and movable radially relative to said primary axis, and d) said chamber having a wall which is engaged by the radially outer ends of the vanes or blades and includes a first wall portion which has substantially the same radius of curvature as the cylindrical outer surface of the rotor and is struck from said primary axis so as to provide a seal between the inlet and outlet ports, e) said wall of the chamber also including a second wall portion corresponding to the "power" part of a cycle of rotation of the rotor, which second wall portion has a radius of curvature greater than that of said first wall portion and is also struck from said primary axis.

2. A motor or pump as claimed in Claim 1, in which the first wall portion extends to either side of that part of the wall of the chamber corresponding to the top dead centre position of the rotor.

3. A motor or pump as claimed in Claim 2, in which the first wall portion extends through 15 to either side of the top dead centre position of the rotor.

4. A motor orpump as claimed in Claim 1, in which the second wall portion extends to either side of the position corresponding to the bottom dead centre position of the rotor.

5. A motor or pump as claimed in Claim 4, in which the second wall portion extends through 60 to either side of the bottom dead centre position of the rotor.

6. A motor or pump as claimed in Claim 2, in which the wall of the chamber includes third and fourth portions located one on each side of the top dead centre position of the rotor, said third and fourth portions each being struck off a common axis spaced downwardly from said primary axis and having a radius of curvature intermediate that of the top dead centre wall portion and the bottom dead centre wall portion, said third and fourth wall portions merging smoothly with the top dead centre and the bottom dead centre wall portions.

7. A motor or pump as claimed in Claim 6, in which cam means are provided for biasing each of the vanes or blades outwardly to the required extent throughout a cycle of rotation of the rotor.

8. A motor or pump as claimed in Claim 1, in which pneumatic means are provided for effecting radially outward biasing of the vanes or rotors.

9. A motor or pump as claimed in Claim 7, in which the housing is formed from three main components, i. e. a centre member of generally cylindrical form of which the internal surface provides the chamber wall having said first, second, third and fourth portions, and a pair of end members which have inwardly facing surfaces shaped to provide the cam means which engage the radially inner ends of the vanes or blades.

10. A motor or pump as claimed in Claim 9, in which at least one of the end members is provided with a generally kidney-shaped air supply port for the provision of air under pressure to achieve the required radially outward displacement of the vanes or blades.

11. A motor or pump as claimed in Claim 9, in which the end members of the housing include recesses in which bearing assemblies are located for providing effective support of the rotor.

12. A motor or pump constructed and arranged to operate substantially as hereinbefore described with reference to and as shown in the accompanying drawings.