Patent ID: 8086360

Claim:
A device for moving a jet member ( 8 ), which is arranged on a carriage ( 6 ) arranged on a vehicle for directing a high pressure jet of liquid against a material layer for material removing treatment of the material layer said carriage being movable to and fro along a guide ( 5 ) between two selectable extreme positions along the guide, said device comprising a hydraulic drive arrangement ( 26 ) having a hydraulic circuit ( 27 ) and being arranged to create the movement of the carriage along the guide, means ( 12 , 21 ′, 13 , 24 , 25 , 31 ) adapted to detect that the carriage has reached a selectable extreme position along the guide, where turning of the carriage is to take place, as well as a control unit ( 14 ) adapted to control the hydraulic drive arrangement and by that said movement of the carriage along the guide, wherein said means comprises a member ( 24 , 25 , 34 ) designed to form a mechanical resistance to a further movement of the carriage when the carriage reaches the respective said extreme position or a region close to said extreme position adapted to influence the flow of hydraulic liquid through said hydraulic circuit of the hydraulic drive arrangement, and a member ( 31 ) adapted to sense a parameter of the hydraulic liquid, the magnitude of which is dependent upon said flow, and send information about the magnitude of this parameter to the control unit ( 14 ), and the control unit is adapted to control the turning of the carriage on the basis of information about the magnitude of said parameter, and the control unit ( 14 ) is adapted to compare the magnitude of a change of said magnitude of said parameter with a predetermined value and determine that an extreme position has been reached responsive to the magnitude of the change exceeding said predetermined value and by that initiate the turning of the carriage ( 6 ).