Patent ID: 6877930

Claim:
A method of working a concrete surface with a water jet, said method comprising the steps of: providing a trolley ( 23 ) carrying a nozzle holder ( 30 ) having a water jet nozzle ( 31 ) at an end of the nozzle holder; moving the trolley ( 23 ) to and fro along a guide between turning positions, and moving the nozzle holder and water jet nozzle in working sweeps with the water jet nozzle in a predetermined angle of attack; swinging the nozzle holder into a position to provide the water jet nozzle with an angle of attack that it will maintain in the next subsequent sweep at the end of a preceding sweep while the trolley continues to move, and stepping forward the guide with the trolley and the nozzle holder between sweeps; and continuing to move the trolley along said guide towards a turning position at the end of a sweep as the water jet reaches an end position of said sweep at the same time during which said nozzle holder is swung into said position in which said water jet nozzle assumes the angle of attack it will maintain during the subsequent sweep.