IE861945L - Electromagnetic reciprocating-piston pump - Google Patents

Description

1£ 4 8 The invention relates to an electromagnetic reciprocating-piston pump, in which a working reciprocating piston is moved to and fro in a cylindrical tube made of non-magnetic material by means of at least one 5 coil arranged on the outside of the cylindrical tube, and in which electromagnetically actuated valves periodically close the inlets and outlets.

In most reciprocating-piston pumps, the piston is forced into a cylindrical cavity closed on one side 10 (to generate excess pressure) or pulled out of this cavity (to generate a vacuum) by means of a connecting rod, Inlet and outlet connections, the valves of which are opened or closed at appropriate moments, open into this cavity. However, there are also already known 15 reciprocating-piston pumps, in which the pumping energy is supplied by coils which are arranged on the outside of the non-magnetic cylinder and which push the piston acting as a soft-iron core to and fro inside the cylinder. Such pumps are particularly suitable for gas 20 analysis purposes, since the entire working volume is closed off hermetically from the environment in every piston position. Consequently, foreign gases which, in manually actuated pumps, can penetrate into the pumping space along the piston wall no longer occur and cannot 25 impair the analysis result.

Where sensitive measurements are concerned. however, it has emerged that foreign gases or oil vapours can also penetrate via the valves located in the inlet and outlet connections, but these could be prevented if these valves were also actuated electromagneti-cally, by accommodating a switching member similar to a dry-reed relay in a non-magnetic valve body. However, such relays are expensive and susceptible to faults.

The object of the invention is to provide a reciprocating-piston pump which is characterized by a simple construction, vacuum tightness, simple maintenance and high operating reliability and which is suitable for very sensitive gas analyses.

According to the invention there is provided an electromagnetic reciprocating - piston pump, in which a reciprocating piston is moved to and fro in a cylindrical tube made of non-magnetic material by means of at least one coil arranged on the outside of the cylindrical tube, and in which electromagnetically actuated valves periodically close the inlets and outlets, three straight cylindrical tubes being arranged parallel to one another between two collectors, each tube containing a reciprocating piston which is at least partially made of soft iron, and carrying outer coils for moving the pistons, and two of these cylindrical tubes being each provided , in the central zone between the collectors, with a connection piece which acts as an inlet or .outlet, wherein the pistons in these cylindrical tubes, the 60-called valve pistons, depending on their position, either close the connection piece or put it in communication with one collector or the other. n 4 V In a preferred embodiment of the invention, two coils are arranged on each of the cylindrical tubes on either side of the central zone and an elastic limit stop is provided in alignment with each piston in each collector. Preferably also, the pistons in the two 5 cylindrical tubes carrying the connection pieces, the so-called valve pistons, have coaxial bores in the two end faces, and the side walls of these pistons have holes in the region of this axial bore. In a further preferred embodiment, the three cylindrical tubes lie next to one another in one plane, and the collectors are 10 likewise designed as tubes.

The invention is explained in more detail below with reference to a preferred exemplary embodiment by means of the drawing which shows a section through a reciprocating- t £ piston pump according to the invention.

Three brass tubes 1, 2, 3 are arranged parallel to one another and open at each of their ends into a respective collector 4, 5. The brass tubes serve as t / S pumping cylinders and each contain a reciprocating p i s- I ton 6, 7 and 8 made of soft iron. Located on each of the tubes 1 to 3, in the centre between the two collectors 4 and 5, is a brass ring 9, 10 and 11, on each of the two sides of which a coil 12, 13; 14, 15 and 16, 17 10 is attached to the tube. Two of the tubes, in particular the tubes 2 and 3, are equipped, in the region of the brass ring 10 and 11, with a nozzle 18, 19, of which one forms the delivery side and the other the suction side of the pump.. The pistons 7 and 8 in the two tubes 15 2 and 3 equipped with connections form valve pistons and have axial bores in their end faces, and the cylindrical surface in the region of this bore is provided with a plurality of holes, e.g. 20. The best possible valve dynamics can be achieved by selecting a suitable 20 size and distribution of these holes.

The two collectors 4 and 5 consist of brass ' tubes of larger cross-section than the cylindrical tubes .] 1 to 3. In alignment with each piston, the collectors have bores, e.g. 21, which are closed by means of screw 25 plugs, e.g. 22. The end face of each plug is provided with an elastic limit stop 23, against which a piston can butt without damage in the event of a fault. Normally, however, a suitable control of the coils 12 to 17 6 \ ensures that the pistons advance no further in the direction of the collectors 4 and S than is shown in the Figure.

The mode of operation of the gas anal/sis pump 5 according to the invention is as follows: 9 The actual working piston which carries out the pumping work is a solid piston 6 in the cylindrical tube 1 which has no pipe connection. This piston is pushed alternately to the left and right as a result of the 10 excitation of the coils 12 and 13. The two valve pistons 7 and 8 require substantially less energy to displace them, since they act as eIectromagnetica 11y actuated inlet and outlet valves. Depending on the phase relationship in which the pistons 7 and 8 are 15 controlled relative to the piston 6, a partial vacuum or an excess pressure is generated at the nozzle 18 in contrast to a constant pressure, e.g. atmospheric pressure, at the nozzle 19. Since the arrangement is completely symmetrical, the functions of the nozzles 20 18 and 19 can also be reversed.

In a production model of the pump according to ri the invention, the length of the brass tubes 1 to 3 bet- ' ween the collectors 4 and 5 was 20 cm, their diameter was 1-.8 cm and the wall thickness was 1.5 mm. At a 25 pumping frequency of 100 cycles per minute, it was possible to measure a differential pressure between the two nozzles 18 and 19 of approximately 25 h Pa for a delivery of approximately 3 litres per minute. It was possible, 1 without difficulty, to generate a vacuum of 10~^ Pa relative to the environment. Since foreign gases or vapours cannot penetrate into the pump either at the working piston 6 or at the valve pistons 7 and 8 , the 5 pump according to the invention is particularly suit-y able for sucking up gases to be analysed and conveying them towards an analyser.

A particularly notable feature of the pump according to the invention is the virtually identical 10 design of the working cylinder and of the valve cylinders, thereby improving the maintenance and operating reliability of the pump. Moreover, the gases to be pumped only come in contact with metals, but not with plastics or other vapourizable materials which could 15 falsify the analysis.

The invention is not restricted to the exemplary embodiment described in detail. Thus, within the scope of the invention, the pump could also be made more compact, if the three cylindrical tubes were arranged in a 20 circle round a centre axis of the pump.

Within the scope of the invention, there is also no need for the pistons themselves to be made of soft iron, but instead can contain only a soft-iron core in the centre, whilst they otherwise consist of non-25 magnetic material, e.g. brass or special steel. 8

Claims (6)

CLAIMS:

1. An electromagnetic reciprocating-piston pump, in which a reciprocating piston is moved to and fro in a cylindrical tube made of non-magnetic material by means of at least one coil arranged on the outside of the cylindrical tube, and in which electromagnetically actuated valves periodically close the inlets and outlets, three straight cylindrical tubes being arranged parallel to one another between two collectors, each tube containing a reciprocating piston which is at least partially made of soft iron, and carrying outer coils for moving the pistons, and two of these cylindrical tubes being each provided, in the central zone between the collectors, with a connection piece which acts as an inlet or outlet, wherein the pistons in these cylindrical tubes, the so-called valve pistons, depending on 9 their position, either close the connection piece or put it in communication with one collector or the other.

2. A reciprocating-piston pump according to Claim 1, wherein two coils are arranged on each of the 5 cylindrical. tubes on either side of the central zona.

3. A reciprocating-piston pump according to one of Claims 1 or 2, wherein an elastic limit stop is provided in alignment with each piston 10 in each collector.

4. A reciprocating-piston pump according to one of Claims 1 to 3, wherein the pistons in the two cylindrical tubes carrying the connection pieces, the so-called valve pistons, have coaxial bores 15 in the two end faces, and the side walls of these pistons have holes in the region of this axial bore.

5. A reciprocating-piston pump according to one of Claims 1 to 4, wherein the three cylindrical tubes lie next to one another in one 20 plane, and the collectors are likewise designed as tubes.

6. An electromagnetic reciprocating-piston pump as claimed in claim 1, substantially as hereinbefore described with reference to and as illustrated in the accompanying 25 drawing. Dated this the 22nd day of July, 1986 F. R. KELLY & CO. M^ EXECUTIVE f 27 <3|yde Rj*ad"7 Ballsbridge, Dublin 4 AGENTS FdR THE APPLICANTS