A method and apparatus for impacting a surface with a desired kinetic impact energy wherein an impacting device which can apply a variable impact energy corresponding to the magnitude of an input control signal is provided and placed adjacent the surface to be impacted. Thereafter, an input control signal...http://www.google.co.uk/patents/US4711754?utm_source=gb-gplus-sharePatent US4711754 - Method and apparatus for impacting a surface with a controlled impact energy
