GB2234786A

GB2234786A - Pump with two rotary cylinder blocks

Info

Publication number: GB2234786A
Application number: GB8913235A
Authority: GB
Inventors: Alexander Grant; Calder Bain
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-06-08
Filing date: 1989-06-08
Publication date: 1991-02-13
Also published as: GB8913235D0

Abstract

A pump comprises first and second barrels (14, 16) rotatably mounted in first and second bushings (10, 12), the barrels each having a plurality of bores (28, 30) formed therein. A corresponding plurality of angled piston members (36) each have a first limb located in one bore of one of the barrels and a second limb located in one bore of the other barrel. Contrarotation of the barrels causes the pistons to reciprocate in the bores. Inlet and outlet means (50, 52) may be provided on one or both of the bushings and communicate alternately with each of the bores. Where four or more pistons are used only one of the barrels need be positively driven, the other being rotated by the motion of the pistons. With fewer pistons, each barrel is preferably driven by an electric motor. It is particularly preferred that switched reluctance motors are employed, making the pump susceptible to full electronic control. <IMAGE>

Description

ROTARY VALVE CYLINDER PUMP The present invention relates to fluid pumps and is particularly concerned with a double ended, rotary valve cylinder pump for pumping liquids and/or gases, and suitable for use as a compressor pump in a freezer, among other applications.

Existing compressor pumps are of generally complex construction, having a relatively large number of different parts which are expensive to manufacture and assemble. It is an object of the present invention to obviate or mitigate this disadvantage by providing a pump having relatively few different parts. A further object of the invention is to provide a pump which is highly efficient in use, and still another object is to provide a pump which is susceptible of direct electronic control.

Accordingly, the invention provides a pump comprising: first and second cylindrical barrels rotatably mounted in first and second cylindrical bushings, said barrels being disposed at an angle to one another such that their axes of rotation intersect; each barrel having at least one cylindrical bore formed therein, said bores being parallel to and spaced from the axis of rotation of their respective barrels; at least one angled piston member having a first cylindrical limb slidably located in the bore of the first barrel and a second cylindrical limb slidably located in the bore of the second barrel, said first and second limbs being disposed at an angle to one another equal to the angle between the axes of the first and second barrels; and drive means adapted to rotate said first and second barrels in opposite directions in a synchronised manner such that said first and second limbs of said piston member reciprocate within their respective bores as the barrels rotate; at least one of said barrels having inlet and outlet means associated therewith, said inlet being adapted to communicate with the end of the bore remote from that in which the piston member is inserted during a first portion of each revolution of the barrel, and said outlet being adapted to communicate with said end of the bore during a second portion of each zrevolution.

Preferably, each barrel is provided with inlet and outlet means such that the pump is double ended.

Preferably also, the barrels and bushings are identical, and disposed symmetrically about the bisector of the angle between their axes of rotation. It is particularly preferred that the axes of rotation intersect substantially at right angles.

In the preferred embodiment of the invention, a single piston member and a single pair of bores is provided.

Alternatively, a plurality of piston members and a corresponding plurality of bores, equidistant from the axis of rotation of each barrel, may be used.

It is further preferred that each cylinder is rotated by means of a drive shaft extending along its axis rotation, each shaft preferably being connected to a separate electric motor. It is particularly preferred that the electric motors are of the switched reluctance type.

Alternatively, where four or more pistons are employed, only one barrel need be provided with a drive shaft, again preferably driven by a switched reluctance motor, the other barrel being rotated by the motion of the pistons.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a sectional side view of a pump embodying the invention; Fig. 2 is a schematic sectional view on line X-X of Fig.l; Fig. 3 is an end view of an alternative embodiment of the invention; and Fig. 4 is a sectional view on line Y-Y of Fig. 3.

Referring now to Figs. 1 and 2 of the drawings, a preferred embodiment of the invention comprises first and second cylindrical bushings 10 and 12, each having a cylindrical barrel 14 and 16 rotatably mounted therein.

The bushings 10 and 12 are each closed at their uppermost ends (as seen in the drawing) by ported plates 18 and 20 (incorporating inlet and outlet ports described in more detail below), and the barrels 14 and 16 are retained in place by annular plates 22 and 24 attached to the lower ends of the bushings 10 and 12. The bushings 10 and 12 are themselves mounted on a casting 26, disposed relative to one another such that the axes of rotation of the barrels 14 and 16 intersect, in this case at a right angle D at point P.

Each of the barrels 14 and 16 is provided with a bore 28 and 30, extending therethrough parallel to and spaced equidistantly from the barrel axes. Located within the bores 28 and 30 are respective first and second cylindrical limbs 32 and 34 of a right-angled pistonmember 36, the limbs 32 and 34 being slidable and rotatable within the bores 28 and 30. The dimensions of the piston member 36 are selected such that when the bores 28 and 30 are located at their closest points to one another (as shown in Fig.

1), the limbs 32 and 34 extend substantially the full length thereof.

The barrels 14 and 16 are each further provided with a drive shaft 38 and 40 extending axially through the ported plates 18 and 20 and connected to the rotors 42 and 44 of respective electric motors 46 and 48. The motors 46 and 48 are preferably of the switched reluctance (also,known as pulse-interrupted) type, whose operation will be discussed in more detail below.

The ported plates 18 and 20 also include inlet and outlet ports 50 and 52 respectively, extending inwardly from opposite lateral edges of the plates 18 and 20 (or, alternatively, downwardly from the top surface thereof) to communicate with respective part-circular grooves 54 and 56 (best seen in Fig. 2), formed in the bottom surface of the plates 18 and 20 and each extending around a portion of the circular path traced by the bores 28 and 30 as the barrels 14 and 16 rotate.

The pump operates by rotating the barrels 14 and 16 in opposite directions and in a synchronised manner, as indicated by arrows A and B. As the barrels 14 and 16 rotate through one half revolution, the limbs 32 and 34 slide out of the bores 28 and 30 from their innermost, top dead-centre position (as illustrated) to an outermost, bottom dead-centre position, indicated in Figs. 1 and 2 by broken lines and with the bores 28, 30, limbs 32, 34 and piston member 36 designated 28', 30', 32', 34' and 36' respectively. As the barrels 14 and 16 continue to rotate the limbs 32 and 34 slide inwardly and return to their innermost position. The bores 28 and 30 thus communicate with their respective inlet grooves 54 during a first portion of each revolution and with their respective outlet grooves 56 during a second portion.

The synchronised contra-rotation of the barrels 14 and 16 could be achieve by mechanical means however it is particularly preferred that they are driven directly by switched reluctance motors 46 and 48, whereby synchronisation may be accomplished electronically.

Switched reluctance motors utilise a plurality of stator windings, and a rotating magnetic field is produced in the stator by electronically switching the power supply between the various windings using MOS power transistors. In the present case, the rotation of the two motors 46 and 48 may be synchronised by using a common control signal to control the switching of the windings. This also provides the possibility of direct electronic control of the operation of the pump for special applications. The arrangement is illustrated schematically in Fig. 1 by the connection of a control circuit 58 between the power supply 60 and the windings (not shown) of stators 62 and 64 of the motors 46 and 48.

The piston 36 is provided with helical grooves 66, adapted to force oil down the bores 28 and 30 so as to provide lubrication and to help create a fluid seal between the bores 28 and 30 and the piston limbs 32 and 34. Oil may be fed to the grooves by means of a sump (not shown) disposed at the bottom of the pump into which the piston member 36 may dip at the bottom of its stroke, or via axial bores formed in one or both of the drive shafts 38 and 40.

Such arrangements are well known in the art and thus are not described or illustrated in greater detail herein.

Similarly, it will be understood that the inlet and outlet ports 50 and 52 may be connected to such valves or the like as may be required for a particular application.

Since both sides of the pump are identical, it can be seen that relatively few different components are required for its construction; namely the casting 26, piston member 36, and two each of the bushings 10, 12 barrels 14, 16, ported plates 18, 20, annular plates 22, 24 and motors 46, 48. Production costs are thus significantly reduced in comparison with conventional pumps. the pump is also highly efficient due to the fact that it is naturally double ended (although it will be appreciated that only one end need be used for pumping if desired), so that the piston member 36 performs useful work throughout its cycle, and further due to the inherently high efficiency of switched reluctance motors.

The pump of Fig. 1 utilises a single piston member 36, however the number of such members, and corresponding pairs of bores, may be increased if desired. When the number of piston members is four or greater, it is found that the mechanical coupling provided thereby between the two rotating barrels is such that only one of the barrels need be driven, with the other barrel being rotated by the piston members themselves. The reliability of operation in such cases increases as the number of piston members is increased. Figs. 3 and 4 illustrate such an embodiment having four piston members spaced symmetrically around the barrels. Parts corresponding to those of Figs. 1 and 2 are designated by the same numerals, the piston members (which are identical to one another) being designated 36A, 36B, 36C and 36D, and the bores 28A, 30A etc. As can be seen, only one barrel 14 is provided with a drive shaft 38 for coupling to a suitable motor (not shown, again preferably a switched reluctance motor). The use of a dual drive, as in Fig. 1, is particularly preferred, however, since it is more energy-efficient.

The double ended nature of the pump allows the two ends to pump different fluids (whether liquid or gas) in any combination, and if both ends are used for pumping the same fluid then its output is double that of conventional pumps of the same bore, stroke etc. Finally, it will be appreciated that the angle D, and the corresponding angles of the piston members, need not be a right angle.

Claims

1. A pump comprising: first and second barrels rotatably mounted in first and second bushings, the barrels being disposed at an angle to one another such that their axes of rotation intersect; each barrel having at least one bore formed therein, said at least one bore being parallel to and spaced from the axis of rotation of the barrel in which it is formed; at least one angled piston member having a first limb slidably located in said at least one bore of the first barrel and a second limb slidably located in said at least one bore of the second barrel, the first and second limbs being disposed at an angle to one another equal to the angle between the axes of the first and second barrels; and drive means adapted to rotate said first and second barrels in opposite directions in a synchronised manner such that the first and second limbs of said at least one piston member reciprocate within their respective bores as the barrels rotate; at least one of the barrels having inlet and outlet means associated therewith, the inlet being adapted to communicate with the end of said at least one bore remote from that in which the piston member is inserted during a first portion of each revolution of the barrel, and the outlet being adapted to communicate with the end of said at least one bore during a second portion of each revolution.

2. A pump as claimed in claim 1 wherein each barrel is provided with inlet and outlet means such that the pump is double ended.

3. A pump as claimed in claim 1 or claim 2 wherein the barrels and bushings are identical, and disposed symmetrically about the bisector of the angle between their axes of rotation.

4. A pump as claimed in any preceding claim wherein the axes of rotation of the barrels intersect substantially at right angles.

5. A pump as claimed in any preceding claim wherein at least one of said barrels is rotated by means of a drive shaft extending along its axis of rotation, said shaft being driven by an electric motor.

6. A pump as claimed in claim 5 wherein each of said barrels is rotated by a drive shaft driven by an electric motor.

7. A pump as claimed in claim 5 or claim 6 wherein the or each electric motor is of the switched reluctance type.

8. A pump as claimed in any of claims 1 to 5 or claim 7 when dependent upon claim 5 wherein there are provided at least four piston members and corresponding bores.

9. A pump as claimed in claim 8 wherein one barrel is provided with a drive shaft driven by an electric motor, the other barrel being contra rotated by the motion of the pistons, in use.

10 A pump as claimed in claim 9 wherein the electric motor is a switched reluctance motor.

11. A pump substantially as hereinbefore described with reference to figures 1 to 4.