The Charles Machine Works, Inc.

George E Strecker

Joe Glenn Worlow

Donald J Keating

Michael T Teiga

A hydraulic circuit (10) is disclosed for use in controlling a horizontal boring machine which requires hydraulic fluid under pressure for rotating a drill bit or backreamer through a rotation circuit and hydraulic fluid under pressure for thrusting the drill bit or backreamer within the bore hole through a thrust circuit. Pressures from both the thrust circuit and control circuit are combined through restrictors in a mixing zone or area (26). The control port of a diversion valve (32) is connected to mixing zone (26). When the combined pressure in the mixing zone exceeds the adjustable spring bias on the diversion valve, the diversion valve will open, diverting fluid from the thrust circuit to a low pressure zone. This will cause a reduction in the pressure in the rotation circuit as well. The reduction of both pressures will reduce the combined pressure in the mixing zone (26), causing the diversion valve to close and the pressures to increase. The hydraulic circuit maintains a constant maximum output for both circuits for a given horsepower input to the boring machine and productivity is enhanced due to reduced operator fatigue.

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Edmond, OK, United States of America

George E Strecker