Pressure balanced rotation spool valve

1. A valve arrangement comprising:

a housing; and

a mainly cylindrical valve element arranged rotatable within the housing;

the housing comprising at least one supply port, at least one exhaust port and at least three sets of two outlet/inlet openings, the supply and exhaust ports being arranged at a distance from each other and the sets of outlet/inlet openings along a rotation axis of the valve element;

the valve element comprising at least two first bores arranged on opposite sides of the valve element, the first bores extending parallel to the rotation axis and connecting the supply port with a first set of outlet/inlet openings in a first position of the valve element;

the valve element further comprising at least two second bores arranged on opposite sides of the valve element, the second bores extending parallel to the rotation axis and connecting the exhaust port with a second set of outlet/inlet openings in the first position of the valve element;

wherein the first and second bores are separated from each other and are configured such that the first bores connect the supply port with the second set of outlet/inlet openings in a second position of the valve element and the second bores connect the exhaust port with the first set of outlet/inlet openings in the second position of the valve element;

wherein at least a third set of outlet/inlet openings is closed by the valve element in both the first and second positions of the valve element and is connected to either said first bores or said second bores in a third position of the valve element; and

wherein the valve arrangement comprises a first circumferential groove connecting the supply port with the first bores in every operational position of the valve element and a second circumferential groove connecting the exhaust port with the second bores in every operational position of the valve element.

2. The valve arrangement according to claim 1 , wherein the at least one set of outlet/inlet openings is arranged between the supply port and the exhaust port as seen along the rotation axis of the valve element.

3. The valve arrangement according to claim 1 , wherein the first and second bores are formed as grooves in an outer surface of the valve element.

4. The valve arrangement according to claim 1 , wherein the first and second circumferential grooves are formed in the valve element.

5. The valve arrangement according to claim 1 , wherein the first set of outlet/inlet openings is connectable to a first unit and the second set of outlet/inlet openings is connectable to a second unit, the first set of outlet/inlet openings being staggered around the housing in relation to the second set of outlet/inlet openings, thereby leading fluid towards the first unit in the first position of the valve element and then the second unit in the second position of the valve element.

6. The valve arrangement according to claim 1 , wherein the housing comprises one set of two supply ports and one set of two exhaust ports, and wherein the supply ports, the exhaust ports and the outlet/inlet openings of each of the at least three sets are arranged around the circumference of the valve element generally opposite each other.

7. The valve arrangement according to claim 1 , further comprising a ceramic liner arranged between the valve element and the valve housing.

8. A system for pressurizing a fluid with the use of a motive fluid, comprising:

a valve arrangement which includes a housing and a generally cylindrical valve element rotatably positioned in the housing;

the housing comprising at least one supply port, at least one exhaust port and at least three sets of two outlet/inlet openings, the supply and exhaust ports and the sets of outlet/inlet openings being axially spaced from each other;

the valve element comprising at least two longitudinal first bores which are located on opposite sides of the valve element and which connect the supply port with a first set of outlet/inlet openings in a first position of the valve element, and at least two longitudinal second bores which are located on opposite sides of the valve element and which connect the exhaust port with a second set of outlet/inlet openings in the first position of the valve element, the first and second bores being separated from each other and configured such that the first bores connect the supply port with the second set of outlet/inlet openings in a second position of the valve element and the second bores connect the exhaust port with the first set of outlet/inlet openings in the second position of the valve element;

wherein at least a third set of outlet/inlet openings is closed by the valve element in both the first and second positions of the valve element and is connected to either said first bores or said second bores in a third position of the valve element;

the valve arrangement further comprising a first circumferential groove connecting the supply port with the first bores in every operational position of the valve element and a second circumferential groove connecting the exhaust port with the second bores in every operational position of the valve element;

wherein the supply port is connectable to a source of the motive fluid and the exhaust port is connectable to a dumping space for the motive fluid; and

wherein at least one pressure transferring unit is connected to at least one set of outlet/inlet openings for transferring pressure from the motive fluid to the fluid to be pressurized.

9. The system according to claim 8 , wherein the pressure transferring unit is an accumulator.

10. The system according to claim 8 , wherein a respective pressure transferring unit is connected to each set of outlet/inlet openings.