GB2062106A

GB2062106A - Rotary Positive-displacement Fluid-machines

Info

Publication number: GB2062106A
Application number: GB8032311A
Authority: GB
Original assignee: LONGSTAFE BC
Current assignee: LONGSTAFE BC
Priority date: 1979-10-08
Filing date: 1980-10-07
Publication date: 1981-05-20
Also published as: GB2062106B

Abstract

A pump or motor comprises a roller (12') rotatable in a fluid-tight casing and defining with the casing axially-extending chamber (13'). At least one second roller (18') rotatable about a parallel axis is in rolling contact with the first roller (12') to constrain fluid to flow axially along the chamber (13'). A vane (14') helically circumscribes the first roller (12') and is received in a helical groove (26') in the second roller (18'). The vane (14') is in fluid-tight sealing relationship with the exterior surface of the chamber (13') and with the groove (26') to minimise axial leakage of fluid past the vane. <IMAGE>

Description

SPECIFICATION Fluid Pumps and Motors This invention relates to fluid pumps and motors.

It is known that substances can be conveyed by means of the Archimedian screw principle, screw conveyors being typically used to convey particulate materials such as powders. However, if similar conveyors are used to convey (i.e. pump) fluids, e.g. liquids and gases, the problem arises that back-pressure can cause the fluid to rotate with the screw whereby the fluid is not conveyed efficiently or is even not conveyed at all. One form of screw conveyor that has been used to convey fluid is known as a "screw pump". One known form of screw pump comprises a fluid-tight casing having intermeshing screws. In use, fluid is swept along the spaces between the threads of the meshing screws by rotation of the screws. The threads generally resemble that of a machine screw in that their axial dimension is equal to half their pitch.Consequently, the spaces between the threads define a small swept volume whereby the known form of screw pump is essentially a low delivery rate device.

According to the present invention there is provided a fluid pump or motor comprising a fluidtight casing, a first roller rotatable in the casing and defining with the casing an axially-extending chamber having an annular cross-section, at least one second roller rotatable in the casing about an axis parallel to the axis of rotation of the first roller and substantially in rolling contact with the first roller so as substantially to constrain fluid to flow axially along the chamber in use of the pump or motor, and at least one vane helically circumscribing the first roller and received in a helical groove in the or at least one of the second rollers, the or each vane being in substantially fluid-tight sealing relationship with the exterior surface of said chamber, and the vane(s) and groove(s) being so configured as to provide a seal against axial passage of fluid past the or each vane where the or each vane is received in a groove or grooves.

A device in accordance with the invention may be used as a pump, in which case the rollers are rotated and a fluid is fed to the chamber. Rotation of the vanes drives the fluid along the chamber.

The rolling contact between the first and second rollers and the sealing between the vane(s) and the chamber, on the one hand, and the vane(s) and groove(s), on the other hand, ensures that the bulk of the fluid is delivered rather than leaking axially past the vanes or rotating with the first roller, whereby the pumping efficiency is high.

A device in accordance with the invention may also be used as a fluid motor, in which case a fluid under pressure is fed to the chamber and rotates the rollers as it passes along the chamber by pressing against the vane(s) and thereby imparting angular momentum to the first roller.

The rolling contact between the first and second rollers and the sealing between the vane(s) and the chamber, on the one hand and the vane(s) and groove(s), on the other hand, ensures that only a minimum of fluid leaks past the vanes or rotates with the first roller, whereby the efficiency is high.

The invention will now be further described, by way of illustrative and non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a partial perspective view of a first fluid pump embodying the invention with part of a casing thereof broken away; Figure 2 is a sectional view of the pump taken along line Il-Il in Figure 1; Figures 3 and 4 are side views of first and second rollers, respectively, of a second fluid pump embodying the invention; Figure 5 is an exploded side view of the second pump with the rollers removed; and Figure 6 is a sectional view of the second pump taken along line VI--VI in Figure 5.

The fluid pump shown in Figures 1 and 2 comprises a tubular fluid-tight casing 10. A first roller 12 is rotatably mounted in the casing 10 and defines therewith an axially-extending chamber 1 3 having an annular cross-section. A pair of vanes 14, 1 6 are integral with the roller 12 and helically circumscribe it, tips or apices of the vanes being closely adjacent to and therefore in substantially fluid-tight sealing relationship with the inside surface of the casing 10, i.e. with the exterior surface of the chamber 1 3.

A pair of second rollers 18, 20 are rotatable in the casing 10 about respective axes parallel to the axis of rotation of the shaft 11. The rollers 18, 20 are received in axially-extending recesses 21,22 which communicate with the chamber 13 and comprise internal surfaces of part-tubular protuberances 23, 24, respectively, of the casing 10. As can best be seen from Figure 2, each recess 21, 22 is of arcuate cross-section and has a radius substantially equal to (in-practice slightly larger than) the radius of the roller 18, 20 received therein, the arc defining the crosssection being greater than 1800.

The rollers 1 8, 20 have therein helical grooves 26, 28, respectively, which each receive the vanes 14, 16.

The relative diameters of the roller 12 and rollers 18, 20 can be chosen at will, provided that the distance around each roller 18, 20 from centre to centre of the grooves (or groove-see later) is the same as the distance on the circumference of the roller 12 from centre to centre of the vanes.

Means, not shown, is provided for rotatably driving the roller 12 and the rollers 18, 20 in the directions shown by arrows. Such means may drive only the roller 12, whereby the rollers 18, 20 are also caused to rotate by virtue of engagement of the vanes 14, 16 within the grooves 26, 28. Alternatively, the roller 12 and the rollers 1 8, 20 may all be driven, for instance by a common drive mechanism such as a motor and a gearing arrangement operative to ensure that the three rollers rotate in synchronism. When the rollers rotate, the roller 12 is in rolling contact with each of the rollers 18,20.

In use of the pump, the first roller 12 and the rollers 18, 20 are rotated and a fluid, e.g. a liquid, is introduced into the chamber 13. The rotating vanes 14, 16 drive the liquid along the chamber 13. Due to the nature of the driving force the liquid has a tendency to helically rotate about the roller 1 2 as well as to travel along the chamber 13. Helical rotation of the liquid is largely obviated by the rolling contact of each of the rollers 18, 20 with the roller 12, the nip between each of the rollers 18, 20 and the roller 12 acting as a fluidtight seal to constrain fluid to flow axially along the chamber 13. In fact, since in this embodiment there are two second rollers 18, 20, the axiallyextending chamber 13 is sub-divided into two axial flow passageways 30, 32 (Figure 2).

The liquid also has a tendency to leak axially past the vanes 14, 1 6 rather than being pushed along the channel 13. Over those parts of the vanes 14, 16 not within the grooves 26, 28, any such axial leakage is largely obviated by the substantially fluid-tight seal provided by the apices or tips of the vanes being disposed closely adjacent the inside surface of the casing 10. Over these parts of the vanes 14, 16 in the grooves 26, 28, any such axial leakage is largely obviated by substantially fluid-tight sealing between the vanes and grooves provided as follows.

The height of the vanes 14, 16 and the configuration of the cooperating grooves 26, 28 is chosen to be such that a particular point along the apex of each vane, as it rotates, sweeps along and in contact with the surface of the groove to provide sealing between the vane and groove In other words, the cross-section of the groove is such as to conform to the locus of the apex or tip of the vane as it 'passes through' the associated roller.

Preferably, the flanks of each vane 14, 1 6 are so configured as to provide additional sealing, in that they conform to the loci of the two edges of the groove as they pass over the vane. This feature can be more clearly envisaged by considering Figure 2 and imagining the shaft 12 and rollers 18, 20 rotated by a few degrees from the position shown. The apex of one of the vanes will be in contact with the surface of one of the grooves, between its edges, since the configuration of the groove conforms to the locus of movement of the apex of the vane.

Furthermore, each edge of such groove will be in sealing relationship with a respective one of the flanks of the vane, since the cross-section of the vane is governed by the loci of the groove edges.

Accordingly, sealing will be provided at three points.

The pump as described above may be used as a motor if high-pressure fluid is fed into the flow passageways 30, 32. The fluid flows along the passageways 30, 32 and rotates the roller 12 and the rollers 18, 20 as it passes therealong by pushing against the vanes 14, 16. The various sealing features described above ensure that the fluid rotates the roller 12 as it travels along the passageways 30, 32, rather than simply flowing along the passageways or around the roller 12 without imparting substantial angular momentum to the roller 12.

The invention can, of course, be embodied in other ways than that described above by way of example. For instance, there may be only one ot more than two rollers and there may be only one vane or more than two vanes. In the simplest case, as will now be described with reference to Figures 3 to 6, there will be a single vane and a single roller.

The pump of Figures 3 to 6 is in many respects similar to that of Figures 1 and 2 and will only be described in so far as it differs therefrom. Items in Figures 3 to 6 which are the same as or similar to corresponding items in Figures 1 and 2 are designated by the same reference numerals, but with prime superscripts.

In the case of Figures 3 to 6, there is only one second roller 18' whereby the axially-extending chamber 13' is not divided into two axiallyextending flow passageways. However, the rollers 12' and 1 8' are in rolling contact to contrain fluid to flow along the chamber 13'.

Referring in particular to Figure 5, the fluidtight casing in this case comprises a block 50 having the chamber 13' and recess 21' bored therein, a pair of end plenums 52, 54 having respective fluid ports 56, 58 and a pair of plates 60, 62, the above items being relatively oriented as shown in Figure 5 and then secured together.

Prior to this, the rollers 12' and 18' are introduced into the block 50, axles 64, 66 of the rollers being received in holes 68, 70, respectively, in each of the plates 60, 62.

In use of the pump of Figures 3 to 6, the rollers 12' and 18' are rotated by driving one or both of them and fluid is drawn into one of the ports 56, 58 and expelled from the other. If the device is to be used as a pump, a fluid under pressure is supplied to one of the ports 56, 58 to cause rotation of the rollers 12', 18'. In either mode, operation is substantially as described above for the pump of Figures 1 and 2.

An important feature of each of the abovedescribed embodiments is that a minimum amount of the chamber 13 or 13' is occupied by the vane or vanes thereby maximising the swept volume and enabling the pump to have a higher output flow rate and therefore be more generally useful than the known form of screw pump mentioned above. More specifically, as can be most easily appreciated from a consideration of Figure 3, the ratio (w:J) between the mouth width (w) of the or each groove in the or each second roller and the spacing (/) between adjacent grooves or between adjacent turns of the same groove, as measured along a line extending along the surface of the roller parallel to the axis of the roller, is less than unity. The ratio (will is preferably less than or equal to 1 :2, and is more preferably still less than or equal to 1:5.

The pitch of the or each vane in each of the above embodiments may be varied in accordance with the application, for instance, in accordance with the viscosity of a liquid being pumped and the balance between pressure and volume delivered.

In each of the above embodiments, if an enhanced amount of sealing is required between the tip or apex of the or each vane and the interior of the casing and the groove or grooves, the tip of the or each vane may be provided with a resiliently radially outwardly biassed seal member.

Claims

1. A fluid pump or motor comprising a fluidtight casing, first roller rotatable in the casing and defining with the casing an axially-extending chamber having an annular cross-section, at least one second roller rotatable in the casing about an axis parallel to the axis of rotation of the first roller and substantially in rolling contact with the first roller so as substantially to constrain fluid to flow axially along the chamber in use of the pump or motor, and at least one vane helically circumscribing the first roller and received in a helical groove in the or at least one of the second rollers, the or each vane being in substantially fluid-tight sealing relationship with the exterior surface of said chamber, and the vane(s) and grooves(s) being so configured as to provide a seal against axial passage of fluid past the or each vane where the or each vane is received in a groove or grooves.

2. A fluid pump or motor according to Claim 1, wherein the ratio between the mouth width of the or each groove in the or each second roller and the spacing between adjacent grooves or between adjacent turns of the same groove, as measured along a line extending along the surface of the roller parallel to the axis of the roller, is less than unity.

3. A fluid pump or motor according to Claim 2, wherein said ratio is less than or equal to 1:2.

4. A fluid pump or motor according to Claim 3, wherein said ratio is less than or equal to 1:5.

5. A fluid pump or motor according to any one of the preceding claims, wherein the crosssection of the or each groove is such that a point on a tip of the associated vane, as it rotates, sweeps along and in contact with the surface of the groove.

6. A fluid pump or motor according to any one of the preceding claims, wherein flanks of the or each vane are so configured that they conform to the loci of two edges of an associated said groove as the edges pass over the vane.

7. A fluid pump or motor according to any one of the preceding claims, wherein the or each second roller is rotatably housed in an axiallyextending recess communicating with said chamber, the or each recess being of arcuate cross-section and having a radius which is substantially equal to the radius of the second roller housed therein.

8. A fluid pump or motor according to Claim 7, wherein the arc defining the cross-section of the or each said recess is greater than 1800.

9. A fluid pump or motor substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.

10. A fluid pump or motor substantially as herein described with reference to Figures 3 to 6 of the accompanying drawings.