Adaptive valve control system for an impact device

In a stroke control system for an impact device having a frame supporting at least one cylinder, a piston within said cylinder and means connecting said piston to a ram such that said ram is repeatedly movable relative to said frame from a retracted position to impact position, a driving fluid system, including a fluid supply and valve means connecting said fluid supply to a port into said at least one cylinder at a position in the cylinder to cause the fluid to drive said ram into impact position, and operating means for controlling said valve means, an improvement whereby the valve means is opened consistently when the piston in the ram driving stroke has just uncovered said port so that each successive blow of the ram is of consistent energy, comprising:

• signal generating means producing a distinctive signal when the ram, in its return stroke, reaches each of a plurality of pre-selected positions, each defining the beginning of a time zone;
• timing means connected to said signal generating means and responding to the respective signals to initiate time counting, measuring time from first generation of the distinctive signals that are produced;
• and
• logic means connecting to and responding to the timing means and signal generating means to actuate said operating means if predetermined times in each zone are reached.