IE780495L

IE780495L - Reciprocating pump with rotating cylinders

Info

Publication number: IE780495L
Application number: IE780495A
Authority: IE
Original assignee: Siemens Ag
Priority date: 1977-03-11
Filing date: 1978-03-10
Publication date: 1978-09-11
Also published as: ATA153278A; IT1092884B; GB1566687A; BE864757A; FR2383331B1; DE2710734C3; AT355703B; DK83278A; JPS53113310A; DE2710734A1; SE7802192L; DE2710734B2; NL7800273A; DK146662B; DK146662C; IE46251B1; FR2383331A1; CH627527A5; IT7820659A0; SE437067B

Description

4 6 1 This invention relates to a pump.

According to the present invention there is provided a pump unit comprising a pump and a motor for driving the pump, the pump comprising a cylinder block 5 which is mounted for rotation on a first shaft and which is provided with cylinders in which pistons are received for movement towards and away from the axis of the first shaft, a piston control member being provided having a piston control surface which extends lO around the axis of the first shaft for controlling the movement of the pistons in the cylinders, the piston control member being mounted for rotation about a second shaft which is connected eccentrically to the first shaft, and valve means being provided for 15 controlling the flow of fluid to and from the cylinders, the motor comprising a rotor, which is rigidly connected to the cylinder block, and a stator, which is secured to the first shaft.

In a construction in accordance with the present 20 invention, the piston control member and the cylinder block are disposed in their eccentric positions relative to one another by means of a single structural part, namely the first shaft and the second shaft connected to it. Thus the cumulative tolerance in 25 the setting of these parts is simply the manufacturing tolerances of the two shafts. 46251 The transfer of internal forces to housing parts of a pump is avoided by the securing of the stator to the first shaft and by the connection of the rotor to the cylinder block. The first shaft thus becomes the 5 central part of the pump to which all forces are transmitted. Presumably the rotor is mounted externally of the stator.

Regulation of the delivery quantity and pressure can be achieved if the valve means includes an inlet 10 control port in the form of a slot the effective length of which is adjustable so that it can be extended beyond the angular position corresponding to top dead centre of the pistons. Extension of the control slot results in part of the fluid sucked into 15 the piston chamber being expelled again without being compressed. Thus the delivery can always be adapted to the particular requirement without varying the motor speed, producing improved partial load efficiency of the pump. Extension of the control slot may be 20 implemented by means of a slide; alternatively inlet openings may be provided which communicate with the control slot and are closable by electrically or mechanically operable closure elements.

The delivery pressure of the pump can also be 25 regulated if the valve means comprises an outlet control port and a plurality of outlet openings extending in a row away from the outlet control port in a direction opposite the direction of rotation of the cylinder block. The outlet openings communicate 30 with the outlet control port through non-return valves which may be adjustable. At each outlet opening, if the desired compression pressure is 4 6 £ 5 1 reached, the corresponding non-return valve opens and thus allows delivery of the fluid.

For a better understanding of the present invention, and to show how it may be carried into 5 effect, reference will now be made, by way of example only, to the accompanying drawings, in which: Figure 1 shows a cross-section through a pump unit; and Figure 2 shows a partial section taken along line 10 II-II in Figure 1.

The pump unit shown in Figure 1 is intended to operate as a gas compressor. A rotor 4 of a drive motor 5 is mounted on a fixed first shaft 1 by means of first and second ball bearings 2 and 3. The rotor 15 4 is mounted externally of the stator 14 and is connected with a cylinder block 6 which is supported by the second ball bearing 3. Formed in the cylinder block 6 are several cylinders 7, which are equally spaced from one another. In each of the cylinders 7 20 there is a spherical ball 8 acting as a piston.

Each ball 8 is supported by a support ring 9 which fits in the appropriate cylinder 7. A cup-shaped piston control member 10 has a piston control surface for controlling the movement of the balls 8 in the 25 cylinders 7. The piston control member 10 has a cylindrical bearing attachment 11. Disposed in the bearing attachment 11 are two further ball bearings 12 by which the piston control member 10 is rotatably mounted on a second shaft 13 which is connected to the 30 first shaft 1 . The second shaft 13 is connected with its axis parallel to that of the first shaft 1 but offset from it. The stator 14 of the drive motor 5 A625 1 is also securely fixed to the first shaft 1. A cover ring 15 is fitted to the piston control member 10.

In the embodiment represented, the part of the first shaft 1 connected to the second shaft 13 com-5 prises valve means in the form of a cone-shaped valve body. This part of the first shaft could, however, be constructed in some other rotationally symmetrical form, such as cylindrical. Provided within the second shaft 13 and connected to the valve body are lO an inlet duct 16 and an outlet duct 17. Passages 18 run in the cylinder block 6 from each cylinder 7 to positions in which they are intermittently placed in communication with inlet and outlet control ports as the cylinder block 6 is rotated.

The inlet control port 19 and the outlet control port 20 are formed in the conical surface of the valve body. The inlet control port 19 is formed as a slot and communicates with the inlet duct 16, and the outlet control port 20 communicates with the outlet 20 duct 17. Several (in this embodiment, three) inlet openings 21 also communicate with the duct 16 and are closable by valves which are not represented in the drawing. Part of the outlet control port 20 is subdivided into several outlet openings 22. The 25 openings 22 are provided with adjustable non-return valves which are also not represented in the drawing. The individual openings 22 are connected to the outlet duct 17.

The complete compressor is installed in a sheet 30 metal housing 23. As this sheet metal housing 23 does not have to absorb any significant internal forces, there are no great strength requirements for 4 (i!25i it. The housing may therefore be made a light-weight construction. The sheet metal housing 23 contains some lubricating oil 24 which, in operation, is drawn in by suction through a slot 25 which communicates 5 with the inlet duct 16. To prevent the oil 24 from escaping from the inlet duct 16 while the compressor is stationary, a stop valve, not represented in the drawing, is disposed in the slot 25, or alternatively the inlet duct 16 is directed upwards in the manner of 10 a siphon.

The compressor operates as follows: The cylinder block 6 is driven by the rotor 4. The balls 8 disposed in the cylinders 7 are pressed by centrifugal force against the piston control 15 surface of the cup-shaped piston control member 10. Since the piston control member 10 is disposed eccentrically relative to the cylinder block 6, the balls 8 are moved to and fro in the cylinders 7. The medium to be compressed is sucked by the balls 8 20 through the inlet duct 16 and is then compressed during the further revolution of the cylinder block 6 and expelled again through the outlet duct 17.

The piston control member 10 is entrained by the friction existing between the balls 8 and the 25 piston control surface. Between the balls 8 and the piston control surface the only relative movement is, in practice, that caused by the eccentricity. Since the balls 8 are rotationally mobile in all directions there are no specific roller bodies as is required in 30 a known compressor. As a result of the coriolis forces and the eccentric arrangement of the cylinder block 6 and the piston control member 10, considerable 4623 1 transverse forces are applied by the balls 8 to the side walls of the cylinders 7. To reduce the resulting surface pressure the support rings 9 are provided which enlarge the contact surface of the balls 8- Each 5 support ring 9 has a chamfer or a rounding off on its side facing its ball 8 and so the support ring 9 projects into the space between its ball 8 and the wall of the cylinder 7. The support rings 9 are pressed into this space by centrifugal force, with the result that they 10 largely absorb the transverse forces of the balls 8. To keep the forces due to inertia small, it is an advantage if the balls 8 are manufactured from a light, but resistant material, such as sintered aluminium oxide ceramics. It is also possible to use hollow 15 balls.

As already mentioned, the delivery volume of the compressor can be controlled by extending the effective length of the slot 19 connected to the inlet duct 16 by control of the openings 21. If the maximum delivery 20 flow of the compressor is not required, one or several of the openings 21 may be opened by the valves coordinated with the openings. This results in part of the medium drawn in by suction being expelled again through the open openings 21 without being compressed. 25 The compression operation thus starts later. This improves the part load efficiency of the compressor.

By subdividing the outlet control port 20 connected to the outlet duct 17 into several openings 22 each provided with an adjustable valve, an even 30 delivery pressure of the compressor is achieved.

The particular opening 22 at which the desired compression pressure is reached opens to permit delivery. -46251 When the medium is drawn in by suction through the inlet duct 16, some oil is also drawn in through the slot 25 at the same time. The oil sucked in disperses as a result of centrifugal force in the 5 cylinders 7 and onto the balls 8. The oil also disperses onto the walls of the cylinders 7 and thus seals the gaps between the balls and the walls of the cylinders 7. At the same time these surfaces are lubricated. Furthermore, excess oil is forced out lO when compression takes place through the control port 20 connected to the outlet duct 17. The oil also penetrates between the cylinder block 6 and the conical surface of the valve body. The oil seals gaps present here too and simultaneously lubricates 15 the surfaces of the cylinder block 6 and the valve body which slide on one another. 4 6 2 51

Claims

CLAIMS:-

1. A pump unit comprising a pump and a motor for driving the pump, the pump comprising a cylinder block ■which is mounted for rotation on a first shaft and 5 which is provided with cylinders in which pistons are received for movement towards and away from the axis of the first shaft, a piston control member being provided having a piston control surface which extends around the axis of the first shaft for controlling the 10 movement of the pistons in the cylinders, the piston control member being mounted for rotation about a second shaft which is connected eccentrically to the first shaft, and valve means being provided for controlling the flow of fluid to and from the cylinders, the 15 motor comprising a rotor, which is rigidly connected to the cylinder block, and a stator, which is secured to the first shaft.

2. A pump unit as claimed in claim 1, in which the rotor of the drive motor is mounted externally 20 of the stator.

3. A pump unit as claimed in claim 1 or 2, in which the valve means comprises a valve body which is fixed to the first shaft, the valve body having inlet and outlet control ports for intermittent communication 25 with the cylinders during rotation of the cylinder block,

4. A pump unit as claimed in claim 3, in which the inlet control port comprises a slot of which the effective length is adjustable. 30

5. A pump unit as claimed in claim 4, in which the effective length of the slot is adjustable by means of a slide. 4 6 2 5 1 - 10 -

6. A pump unit as claimed in claim 4, in which inlet openings are provided which are in communication with the slot and which are closable by electrically or mechanically operable closure elements to adjust 5 the effective length of the slot.

7. A pump unit as claimed in any one of claims 3 to 6, in which a plurality of outlet openings, which communicate with the outlet control port through nonreturn valves, are disposed in a row extending away 10 from the outlet control port in a direction opposite to the intended operative direction of rotation of the cylinder block.

8. A pump unit as claimed in claim 7, in which the non-return valves are adjustable. 15

9. A pump unit substantially as described herein with reference to the accompanying drawings. P. R. KELLY & CO., AGENTS FOR THE APPLICANTS.