Patent ID: 8033641

Claim:
A method for moving a jet member ( 6 ) having a nozzle ( 14 ), comprising the steps of arranging said jet member ( 6 ) on a carriage ( 4 ) movable in a substantially rectilinear path and providing a base portion ( 5 ) to which said jet member ( 6 ) is pivotably connected, moving said carriage ( 4 ) and thereby the nozzle ( 14 ) of the jet member ( 6 ) in said rectilinear path over a layer to be treated by the jet and pivoting the jet member ( 6 ) with respect to said base portion ( 5 ) for changing the attack angle of the jet upon said layer, co-ordinating said movement in said rectilinear path and said pivoting for moving an impact point of the jet on said layer with a substantially constant speed over said layer, substantially continuously during movement of the carriage ( 4 ), carrying out measurements allowing establishment of the speed of the carriage ( 4 ), substantially continuously during pivoting of the jet member ( 6 ), carrying out measurements allowing establishment of the contribution of a pivoting movement of said jet member ( 6 ) to the speed of said impact point of the jet over said layer, calculating the total speed of said impact point of the jet over said layer through information about said two measurements, comparing the value of said total speed so calculated with a predetermined set speed value for determining a difference speed value, and controlling said movement in said rectilinear path and said pivoting movement to cancel out said difference value.