Sealing arrangement for relatively movable parts and device including such a sealing arrangement

1. A sealing arrangement for two relatively movable first and second parts, including a sealing ring positioned in a sealing ring seat formed as a groove in a circumference of one of the parts for sealing contact against the other one of the parts, so as to separate a first side of the sealing ring from a second side of the sealing ring, said sealing arrangement comprising:

liquid supply means for supplying liquid under pressure to the second side of the sealing ring, and

means for balancing a pressure of the supplied liquid in a region of the sealing ring so that forces on the sealing ring resulting from the pressure prevailing on the first side of the sealing ring are counteracted and balanced in such a way that in operation the sealing ring is essentially free-floating in the groove,

said first and second parts being relatively reciprocating.

2. The arrangement according to claim 1 , further comprising a valve device set to balance the pressure of the supplied liquid in the area of the sealing ring.

3. The arrangement according to claim 2 , wherein the valve device is preset to limit the pressure of the supplied liquid.

4. The arrangement according to claim 3 , wherein the valve device is set to limit the pressure to about 80-100% of the pressure inside the pressure chamber.

5. The arrangement according to claim 2 , in that wherein the valve device includes a portion of the sealing ring in co-operation with the sealing ring seat.

6. The arrangement according to claim 5 , in that wherein said portion of the sealing ring is a ring surface directed from the first side which is arranged to co-operate with a surface of said seat.

7. The arrangement according to claim 5 , in that wherein said portion of the sealing ring is an edge portion or a separate sealing element directed radially from the element said portion is intended to seal against.

8. The arrangement according to claim 3 , in that wherein the valve device is a pressure controlled valve which is separate from the sealing ring.

9. The arrangement according to claim 1 , in further comprising a sealing device for sealing between the relatively movable parts in a position opposite to the sealing ring as seen from the position of the means for liquid supply.

10. The arrangement according to claim 9 , wherein said sealing device is formed by a first, high pressure seal member and a second, low pressure seal, and an intermediate space having a fluid outlet.

11. The arrangement according to claim 10 , wherein the fluid outlet is a low pressure outlet for eliminating pressure build-up in the intermediate space.

12. The arrangement according to claim 1 , wherein at least one of the parts includes at least one outlet channel for supplied liquid.

13. A reciprocating piston device including a cylinder and a relatively movable piston and a sealing ring which is positioned in a seat formed as a groove in the circumference of one of the piston and the cylinder for sealing contact between the piston and the cylinder, so as to separate a first side of the sealing ring from a second side of the sealing ring, said piston and cylinder forming a pressure chamber, said piston device comprising:

liquid supply means for supplying liquid under pressure to the second side of the sealing ring, and

means for balancing a pressure of the supplied liquid in a region of the sealing ring so that forces on the sealing ring resulting from the pressure prevailing on the first side of the sealing ring are counteracted and balanced in such a way that in operation the sealing ring is essentially free-floating in the groove.

14. The device according to claim 13 , wherein the liquid supply means includes an enlarged piston portion for co-operation with an enlarged cylinder portion.

15. The device according to claim 14 , wherein a working chamber which is formed by said piston and cylinder portions is ring-shaped.

16. The device according to claim 13 , wherein the liquid supply means includes an external pump having at least one supply conduit debouching in a cylinder wall.

17. The device according to claim 16 , wherein the liquid supply means includes a liquid pump selected from the group of a gear type pump, a reciprocating piston pump, an impeller pump, a screw pump or a rotary piston pump.

18. The device according to claim 13 , wherein the piston includes a valve device which is preset to balance the liquid pressure in the area of the sealing ring.

19. The device according to claim 18 , wherein the valve device is set to limit the pressure to about 80-100% of the pressure inside the pressure chamber.

20. The device according to claim 18 , wherein the valve device includes a portion of the sealing ring in co-operation with its seat.

21. The device according to claim 20 , wherein said portion of the sealing ring is a ring surface directed from the pressure chamber which is arranged to co-operate with a surface of said seat.

22. The device according to claim 20 , wherein said portion of the sealing ring is an edge portion directed radially from the element said portion is intended to seal against.

23. The device according to claim 13 , wherein the piston includes at least one outlet channel for liquid.

24. The device according to claim 13 , wherein the valve device is a pressure controlled valve which is separate from the sealing ring.

25. The device according to claim 13 , further comprising a sealing device for sealing between the piston and the cylinder in a position opposite to the sealing ring as seen from the position of liquid supply means.

26. The device according to claim 25 , wherein said sealing device is formed by a first, high pressure seal member and a second, low pressure seal, and an intermediate space having a fluid outlet.