WO2004033914A1

WO2004033914A1 - Rotary sliding vane compressor

Info

Publication number: WO2004033914A1
Application number: PCT/GB2003/004354
Authority: WO
Inventors: Edward Boller
Original assignee: Compair Uk Limited
Priority date: 2002-10-10
Filing date: 2003-10-08
Publication date: 2004-04-22
Also published as: GB0223530D0; AU2003300505A1; GB2394005A

Abstract

The present invention relates to a positive displacement rotary gas, e.g. air, compressor of the eccentric rotor sliding vane type and particularly, but not exclusively, to a compressor wherein the rotor is mounted on an extended shaft of an electric motor. The compressor comprises a cylindrical rotor provided with a plurality of radially extending grooves each defined by a radially extending inner most grove bottom and first and second parallel groove walls extending outwardly therefrom wherein at least the first groove wall is joined to the groove bottom by a first radius portion.

Description

ROTARY SLIDING VANE COMPRESSOR

The present invention relates to a positive displacement rotary gas, e.g. air, compressor of the eccentric rotor sliding vane type and particularly, but not exclusively, to a compressor wherein the rotor is mounted on an extended shaft of an electric motor.

Shown in Figure 1 is a diagrammatic illustration of a conventional rotary vane compressor comprising a cylindrical rotor (1) driven by an electric motor (not shown) and mounted eccentrically within the cylindrical bore of a stator (2). Formed in the rotor (1) is a plurality of radially extending grooves or slots (9) each of which accommodates a freely slideable blade or vane (5). During rotation R of the rotor by the electric motor each vane (5) is thrown outwards by centrifugal force so that its outer edge sweeps the internal cylindrical surface of the stator (2). The free space between adjacent vanes is thus divided into closed cells (7,8). Air or other gas taken in at inlet (I) through port (3) is thus compressed as the free space in each cell diminishes as the rotor turns and the compressed air is output at (O) via outlet port (4). The compressor further compris.es oil injection means via inlet (6) to provide lubrication and sealing between the outer edges of the vanes and the inner surface of the stator.

Accordingly in operation of a rotary vane compressor the closed cells to either side of any particular vane are at significantly different pressures as the vane passes from the inlet port to the outlet port. In Figure 1 , for example, the closed cell 8 is at a significantly higher pressure than the adjacent closed cell 7. This pressure differential acting on the interposed vane 10 produces a resultant force which has damaging implications for both the vane itself and the groove, and particularly stress damage to the interior portion of the rotor in the region of the radially inner end of each groove. The likelihood of stress related damage resulting from the differential pressure acting on the vane is increased in the case of a compressor in which the rotor has a central bore by which it is mounted on the extended shaft of the driving electric motor, in contrast to a conventional rotor having a solid centre. This increased risk arises because of the presence of the central bore through the longitudinal axis of the cylindrical rotor said bore being in relatively close proximity to the radially inner bases of the grooves.

It is an object of the present invention to eliminate or at least mitigate possible stress related damage in the region of the radially inner groove ends of the rotor of an eccentric rotor sliding vane compressor.

According to one aspect of the present invention a rotary sliding vane compressor comprises a cylindrical rotor provided with a plurality of radially extending grooves each defined by a radially inner most groove bottom and two parallel groove walls extending outwardly therefrom wherein at least one of the groove walls is joined to the groove bottom by a radius portion.

In another of its aspects the present invention teaches that the groove comprises a pair of planar confronting surfaces one of which extends further radially .inwards than the other.

Preferably the radius portion is associated with the groove wall on the low pressure side of the blade or vane, i.e. associated with the trailing groove wall in the direction of rotation of the rotor.

The groove side wall opposite said at least one of the groove walls may also be joined to the groove bottom by a chamfered portion or by a radius portion. Where both portions are radius portions preferably the radius portion joining the groove side wall on the low pressure side preferably has a greater radius of curvature than that of the radius portion on the other side. More preferably the radius of curvature of the portion on the high pressure side is between 0.5 and 1.0 mm and the radius of curvature of the portion on the low pressure side is equal to the width of the groove less the radius of curvature of the portion on the high pressure side.

The bottom portion, i.e. the radially innermost portion, of the compressor blade or vane may also have a similar or identical shape profile to that of the radially inner part of the groove so that the bottom of the blade is able to sit fully in the groove bottom.

Further aspects of the present invention will become apparent from the following description given, by way of example only, of an embodiment of the invention in conjunction with the following diagrams in which: -

Figure 2 shows a schematic diagram of a cross section of a rotor of a compressor in accordance with the present invention, the cross section being taken perpendicularly to the rotational axis of the rotor; and

Figure 3 shows in more detail the radially inner end of one of the grooves in the rotor in Figure 2; and

Figure 4 a diagrammatic cross section of a vane or blade of a compressor of the present invention; and

Figure 5 show further detail of the radially inward end of the blade of Figure 4.

The rotor 21 of the compressor of the present invention shown in Figure 2 has six equal sized and equi-spaced apart grooves 22 extending radially outwards from a groove bottom 25 to the cylindrical outer peripheral surface 27 of the rotor. Each of the grooves 22 is defined by two parallel groove walls 23, 24, groove wall 23 being the leading groove wall when the rotor turns around rotational axis C in the direction R as indicated. Accordingly the opposing groove wall 24 is the trailing groove wall. In the centre of the rotor 21 is a longitudinally extending circular hole 26 enabling the rotor 21 to be mounted on the extended shaft of an electric motor (not shown)

As shown in Figure 3 the junction of the trailing groove wall 24 with the groove bottom 25 is radiused to the extent that the concavely curved portion 29 extends beyond the centre line of the groove, i.e. beyond 50 percent of the width W of the groove. In accordance with the preferred aspect of the invention the radius of curvature RADG of the curved portion is between 50 percent and 90 percent of the width W of the groove. In this particular embodiment the value of rad is 76 percent of the width W.

As also shown in Figure 3 the portion 28 at the junction of the leading groove wall 23 with the groove base 25 is chamfered. In this particular embodiment the portion 28 is chamfered at an angle of 45 degrees but it may be of radiused with a radius of curvature preferably between 0.5 and 1.0 mm.

The curved portion 29 in a preferred configuration has, a radius of curvature RADG equal to the groove width W minus the radius of curvature of the portion 28 if portion 28 is curved, not chamfered with the centres of curvature positioned such that the curved portions 28,29 are tangential with their respective groove walls 24,23.

In this particular embodiment the radial length L of the groove is substantially three times as great as the distance D between the groove bottom 25 and the central hole 26. In accordance with the preferred aspects of the present invention the radius of curvature RADG of the curved portion 29 is between 20 and 30 percent of the distance D between the grooved bottom 25 and the central hole 26.

Shown in Figure 4 is a cross section of a blade or vane 30 of the present invention for use in conjunction with the rotor 21. In operation of the compressor the blade 30 is positioned within groove 22 such that the blade side 31 is the leading side whereas the opposite side 32 is the trailing side. Further details of the radially inner end of the blade 30 are shown in Figure 5 where it can be seen that the portion 34 at the junction of the trailing blade side 32 and the blade bottom 33 is convexly curved in a matching form to the concavely formed portion 29 adjacent groove bottom. Similarly the junction portion 35 between the leading blade side 31 and the blade bottom 33 is chamfered to conform with the chamfered portion 28 of the groove.

It will also be seen from Figures 4 and 5 that the side surfaces 31 , 32 are each substantially planar and that one surface 31 , when in situ, extends further radially inwards than the other side surface 32.

In a preferred embodiment of the present invention the configuration of the radially inner end of the blade is substantially identical to the radially inner end of the groove with the radius of curvature RADB of the curved portion 34 being the same as the radius RADG of the groove portion 29.

Such preferred embodiment may also have one or more shallow grooves formed on one side of the blade, these grooves extending radially outwardly from the radially inner blade bottom end to the radially outer blade top end in order to relieve pressure at the inner end of the blade. Preferably the groove or grooves are formed on one side only of the blade, and more preferably on the same side on each of the blades such that may provide a visual aid in the correct assembling of the blades in the rotor. Most preferably the groove or grooves are formed in the trailing side of the blade.

Claims

1. A rotary sliding vane compressor comprising a cylindrical rotor provided with a plurality of radially extending grooves each defined by a radially inner most groove bottom and first and second parallel groove walls extending outwardly therefrom wherein at least the first groove wall is joined to the groove bottom by a first radius portion.

2. A rotary sliding vane compressor in accordance with claim 1, wherein the first groove wall is the trailing groove wall in the direction of rotation of the rotor such that the first radius portion associated with said first groove wall is on the low pressure side of the sliding vane.

3. A rotary sliding vane compressor in accordance with either of claims 1 and 2, wherein the second groove side wall is joined to the groove bottom by a chamfered portion.

4. A rotary sliding vane compressor in accordance with either of claims 1 and 2, wherein the second groove side wall is joined to the groove bottom by a second radius portion.

5. A rotary sliding vane compressor in accordance with claim 4, wherein the first radius portion has a greater radius of curvature than that of the second radius portion.

6. A rotary sliding vane compressor in accordance with either of claims 4 and 5, wherein the second radius portion has a radius of curvature in the range of 0.5 and 1.0 mm.

7. A rotary sliding vane compressor in accordance with any of claims 4 to 6, wherein the radius of curvature of the first radius portion is equal to the width of the groove minus the radius of curvature of the second radius portion which is the radius portion on the high pressure side of the vane or blade.

8. A rotary sliding vane compressor in accordance with any of claims 1 to 7, wherein the radially innermost portion of a vane which slides within a groove has a substantially similar shape profile to that of the radially inner part of the groove such that the bottom of the vane is able to sit fully in the groove bottom.

9. A rotary sliding vane compressor comprising a cylindrical rotor provided with a plurality of radially extending grooves wherein each groove comprises a pair of planar confronting surfaces one of which is extends further radially inwardly than the other.

10. A rotary sliding vane compressor in accordance claim 9, wherein in use of the compressor the planar confronting surface of greatest radial extent is the leading surface of the pair in the direction of rotation of the rotor such that it is on the side of higher pressure.

11. A rotary sliding vane compressor in accordance with any one of the preceding claims wherein the rotor has a central bore.

12. A rotary sliding vane compressor as herein described and depicted in Figures 1 to 5.