DOSING PUMP WITH DOSING DIAPHRAGM

Abstract

The present invention concerns a dosing pump comprising a dosing chamber, a working chamber and a dosing diaphragm, wherein the dosing chamber and the working chamber are separated from each other by the dosing diaphragm, wherein there is provided a device for reciprocating movement of the dosing diaphragm between a first position and a second position, wherein the volume of the dosing chamber is smaller in the first position than in the second position. To provide a dosing pump, the dosing diaphragm of which has an increased service life and which as far as possible can be hydraulically operated even at very low dosing fluid pressures at the suction side it is proposed according to the invention that there is provided a prestressing device which prestresses the dosing diaphragm in the direction of the first or second position.

Claims

1. A dosing pump comprising a dosing chamber, a working chamber, a dosing diaphragm comprising an elastic material and having edge regions, and a gripping device having two mutually corresponding contact surfaces, the gripping device holding the dosing diaphragm at the edge regions, wherein the dosing chamber and the working chamber are separated from each other by the dosing diaphragm, wherein there is provided a device for reciprocating movement of the dosing diaphragm between a first position and a second position, wherein the volume of the dosing chamber is smaller in the first position than in the second position, the gripping device prestressing the dosing diaphragm in the direction of the first or second position.

2. A dosing pump according to claim 1 characterised in that the gripping device prestresses the dosing diaphragm in the direction of the first position.

3. A dosing pump according to claim 1 characterised in that the device for reciprocating movement of the dosing diaphragm is a hydraulic device and a hydraulic fluid is arranged in the working chamber, wherein the hydraulic device is of a such a design configuration that it can act on the hydraulic fluid with a hydraulic pressure to move the dosing diaphragm in the direction of the first position.

4. A dosing pump according to claim 1 characterised in that the dosing diaphragm comprises metal.

5. A dosing pump according to claim 4 characterised in that the dosing diaphragm is a flat metal foil.

6. (canceled)

7. (canceled)

8. (canceled)

9. A dosing pump claim 1 characterised in that the corresponding contact surfaces are of a non-flat configuration.

10. A dosing pump according to claim 1 characterised in that the corresponding contact surfaces are of a curved configuration.

11. A dosing pump claim 1 characterised in that the corresponding contact surfaces are of a conical configuration having a cone angle.

12. A dosing pump according to claim 11 wherein the cone angle of the contact surfaces is between 0 degrees and 10 degrees.

13. A dosing pump according to claim 12 wherein the cone angle is between 2 degrees and 5 degrees.

Description

[0015] Further advantages, features and possible uses will be apparent from the description hereinafter of a preferred embodiment and the accompanying FIGURE in which:

[0016] FIG. 1 shows a diagrammatic cross-sectional view through the diaphragm and the gripping device according to a first embodiment of the invention.

[0017] The basic structure of the described dosing pumps is known to the man skilled in the art. FIG. 1 therefore only shows a cross-sectional view of a dosing diaphragm 5 which separates a dosing chamber 1 from a working chamber 2. The dosing diaphragm 5 is gripped at its edge regions between the gripping device 3, 4. The gripping device 3, 4 comprises two cylindrical elements 3, 4 with mutually facing contact surfaces, between which the edge regions of the dosing diaphragm 5 are clamped. As the contact surfaces are of a conical configuration with a cone angle α the dosing diaphragm 5 in the situation shown in FIG. 1 is curved towards the left when the two cylindrical elements 3, 4 of the gripping device are moved towards each other and the edge regions of the diaphragm are clamped. The dosing diaphragm is therefore prestressed towards the left in FIG. 1 by the gripping device.

[0018] In the preferred embodiment the working chamber 2 is filled with a hydraulic fluid which can be acted upon with a pressure by means of a suitable device like for example a driven piston. When the pressure in the working chamber 2 rises above the pressure in the dosing chamber 1 then the dosing diaphragm 5 is moved still further towards the left. That position is diagrammatically shown by the broken line 5′. When the pressure in the working chamber 2 is reduced the diaphragm moves back into the position again, that is shown by the solid line 5.

[0019] Alternate bending of the diaphragm is avoided by the prestressing of the diaphragm in accordance with the invention. In the case of the alternate bending loading which is usual in the state of the art microstructural changes occur, which lead to premature material fatigue. In the case of alternate bending a force-travel graph also does not exhibit the linear relationship usually to be expected for elastic materials (Hook's law) but shows hysteresis in the region of the bending alternation.

[0020] The alternate bending is prevented by the prestressing as now the movement of the diaphragm always takes place in the same direction.

LIST OF REFERENCES

[0021] 1 dosing chamber [0022] 2 working chamber [0023] 3 gripping device [0024] 4 gripping device [0025] 5 dosing diaphragm