Method and apparatus for removal of surface material

Apparatus for removing material from a work surface and for use in association with a source of water at a pressure within the range of from about 10,000 to about 25,000 psi, which apparatus comprises:

• a support structure adapted to be stationarily disposed on a supporting surface;
• extendible arm means mounted on said support structure for movement along a first linear path in only a first direction generally parallel to the work surface and away from and toward said support structure with said support structure stationarily disposed on the supporting surface;
• power operated extension means attached to said support structure and to said arm means and operable to extend and retract said arm means relative to said support structure along said first linear path;
• nozzle support means secured to said arm means at a position spaced apart from said support structure and in such a manner that said nozzle support means is retained in a fixed position relative to said arm means on operation of said extension means, and said nozzle support means extending angularly to said arm means in a second direction angularly oriented with respect to said first direction;
• a rotatable nozzle means mounted on said nozzle support means for rotation about a nozzle axis angularly disposed with respect to the work surface and for movement along said nozzle support means in said second direction, at least one discharge orifice being provided in said nozzle means for the discharge of water under pressure therefrom in a direction angularly disposed with respect to said nozzle axis whereby water, on discharge from said nozzle means and on rotation of said nozzle means about said nozzle axis, defines an expanding cone-shaped configuration for impingement on the work surface;
• a nozzle drive means attached to said rotatable nozzle means and to said nozzle support means and adapted to move said rotatable nozzle means in both directions along a second linear path in said second direction generally parallel to the work surface with said nozzle means in spaced apart disposition relative to the work surface and with said support structure stationarily disposed on the supporting surface;
• spacing means for maintaining said nozzle means at a desired separation from the work surface on operation of both said extension means and said nozzle drive means;
• and
• control means operatively associated with said extension means and said nozzle drive means to cause said nozzle drive means to move said rotatable nozzle means alternately in opposite directions along said second linear path and to move said arm means along said first linear path so that water discharging from said nozzle means impinges the work surface in sequential bands.