Device and method for moving a jet member

A device for moving a jet member (6) having a nozzle, said device comprising

• a carriage (4) provided with a base portion (5) to which said jet member is connected,
• a guide member (3) along which said carriage is movable in a substantially rectilinear first path for moving the nozzle (14) of the jet member (6) over a layer to be treated by the jet,
• the connection of said jet member (6) to said base portion (5) providing movability of the jet member with respect to the base portion, said carriage comprising a first movability of the jet member (6) for moving an impact point of said jet in a second path perpendicularly to said first path,
• a driving arrangement (9, 10, 21) configured to move said carriage along said first path and said jet member with respect to said base portion of said carriage, and
• a control unit (15) configured to control said driving arrangement for controlling the movement of said impact point of said jet over said layer,
• wherein the control unit (15) is configured to control said driving arrangement to combine movement of said carriage along said guide member (3) and movement of said jet member (6) with respect to said base portion (5) of said carriage to make said impact point of said jet on said layer to travel with a constant speed over said layer,
• the control unit (15) is configured to control the driving arrangement to obtain a speed of the movement of said jet member (6) along said second path having a maximum in a mid-region along this path and decreasing towards end positions of said second path for increasing after returning from said end position and compensate a change of speed of said impact point along said second path caused thereby by a corresponding opposite change of speed of the impact point along said first path,
• said movability of the jet member (6) with respect to said base portion (5) of the carriage (4) comprises a second movability of the jet member along said first path, and the control unit (15) is configured to control said driving arrangement (21) to move the jet member with respect to said base portion (5) along said first path with a frequency being twice the frequency of a movement of the jet member with respect to the base portion along said second path and the jet member to be in a mid-region of the movement according to said second movability with a maximum speed of this movement and move in the direction of movement of said carriage (4) along said first path at said end positions of the movement of the let member according to said first movability,
• said first movability is a pivotability of the jet member (6) around a first axis (19) extending in parallel with said first path, and
• said second movability is a pivotability of the let member (6) around a second axis (20) extending perpendicularly to said first path.