Sensor diaphragm

1. A sensor diaphragm comprising a plurality of diaphragm layers which are arranged in a mutually superposed relationship and which include a conveyor diaphragm ( 1 ), a first electrically conductive diaphragm layer ( 2 ) arranged therebeneath, an electrically insulating diaphragm layer ( 3 ) arranged therebeneath and a second electrically conductive diaphragm layer ( 4 ) arranged therebeneath, wherein the first and second conductive diaphragm layers ( 2 , 4 ) are separated from each other and electrically insulated by the electrically insulating diaphragm layer ( 3 ) and the second electrically conductive diaphragm layer ( 4 ) has through portions ( 7 ) which engage through openings ( 5 ) in the electrically insulating diaphragm layer ( 3 ) and through openings ( 6 ) in the first electrically conductive diaphragm layer ( 2 ) and the electrically insulating diaphragm layer ( 3 ) has portions ( 12 ) which engage through the openings ( 5 ) in the first conductive diaphragm layer.

2. A sensor diaphragm according to claim 1 wherein the conveyor diaphragm ( 1 ) is made from a flexible, chemically inert plastic material.

3. A sensor diaphragm according to claim 2 wherein the plastic material is polytetrafluoroethylene (PTFE).

4. A sensor diaphragm according to claim 1 wherein the electrically conductive ( 2 , 4 ) and electrically insulating ( 3 ) diaphragm layers comprise a rubber material.

5. A sensor diaphragm according to claim 2 wherein the electrically conductive ( 2 , 4 ) and electrically insulating ( 3 ) diaphragm layers comprise a rubber material.

6. The sensor diaphragm of claim 4 wherein the rubber material is an EPDM (ethylene-propylene terpolymer reinforced with plastic fibers.

7. A sensor diaphragm according to claim 4 wherein the electrically conductive diaphragm layers ( 2 , 4 ) of rubber include an admixture of carbon particles in an amount such that the diaphragm layers are electrically conductive.

8. A sensor diaphragm according to claim 5 wherein the electrically conductive diaphragm layers ( 2 , 4 ) of rubber include an admixture of carbon particles in an amount such that the diaphragm layers are electrically conductive.

9. A sensor diaphragm according to claim 6 wherein the electrically conductive diaphragm layers ( 2 , 4 ) of rubber include an admixture of carbon particles in an amount such that the diaphragm layers are electrically conductive.

10. A sensor diaphragm according to claim 1 wherein the through portions are arranged in a proximity of diaphragm regions which are flexed in a diaphragm stroke movement.

11. A sensor diaphragm according to claim 4 wherein the through portions are arranged in a proximity of diaphragm regions which are flexed in a diaphragm stroke movement.

12. A sensor diaphragm according to claim 1 wherein the diaphragm is substantially in the shape of a circular disc.

13. A sensor diaphragm according to claim 1 wherein the diaphragm layers are of substantially the same diameter.

14. A sensor diaphragm according to claim 1 wherein the through portions through the first electrically conductive diaphragm layer ( 2 ) are of a circular, circular segment-shaped, kidney-shaped, square or oval form.

15. A sensor diaphragm according to claim 4 wherein the through portions through the first electrically conductive diaphragm layer ( 2 ) are of a circular, circular segment-shaped, kidney-shaped, square or oval form.

16. A sensor diaphragm according to claim 1 wherein the through portions are arranged symmetrically around the center point of the diaphragm.

17. A sensor diaphragm according to claim 1 wherein a through portion is arranged at the center point of the diaphragm.

18. A sensor diaphragm according to claim 4 wherein a through portion is arranged at the center point of the diaphragm.

19. A sensor diaphragm according to claim 10 wherein a through portion is arranged at the center point of the diaphragm.

20. A sensor diaphragm according to claim 1 wherein between 4 and 20 through portions are arranged symmetrically around a center point of the diaphragm.

21. A sensor diaphragm according to claim 1 wherein the through portions through the first electrically conductive diaphragm layer ( 2 ) form concentric circles around a center point of the diaphragm.

22. A sensor diaphragm according to claim 1 wherein the conveyor diaphragm ( 1 ) has at least one sealing ridge ( 8 ) which extends concentrically around a center point of the diaphragm and which is arranged in a clamping region ( 9 ) of the diaphragm.

23. A sensor diaphragm according to claim 1 wherein the diaphragm has a diaphragm core ( 10 ) which is arranged beneath the second conductive diaphragm layer ( 4 ) symmetrically with respect to a center point of the diaphragm.

24. A sensor diaphragm according to claim 1 wherein the sensor diaphragm has a further electrically insulating diaphragm layer ( 11 ) of rubber between the second conductive diaphragm layer ( 4 ) and the diaphragm core ( 10 ), which is positively connected to the diaphragm core ( 10 ).

25. A sensor diaphragm according to claim 24 wherein layers ( 1 , 2 , 3 , 4 , 11 ) of the diaphragm are sealed together.

26. A sensor diaphragm according to claim 1 wherein the electrically conductive diaphragm layers ( 2 , 4 ) are connected to two terminals of an electrical measuring device.

27. A sensor diaphragm according to claim 1 wherein the conductive diaphragm layers ( 2 , 4 ) are contacted by means of metallic contact pins ( 13 , 14 ), wherein the pin ( 13 ) contacts the first conductive diaphragm layer ( 2 ) and engages through the second conductive diaphragm layer ( 4 ) and through the insulating diaphragm layer ( 3 ) and is insulated from the second conductive diaphragm layer ( 4 ).

28. The sensor diaphragm of claim 27 wherein pin 13 is insulated from second diaphragm layer ( 4 ) with material of insulating diaphragm layer ( 3 ).

29. A diaphragm pump comprising a sensor diaphragm according to claim 1 .