Hydraulic control system

US4072169A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Joachim Heiser · Stuttgart, DE
• Rainer Hoheisel
• Heinz Flaschar
• Heinz Gand
• Heinz Kleinschmidt · Ditzingen, DE
• Konrad Braunlinger
• Klaus Sopha
• Roland Schempp · Leinfelden, DE
• Hermann Sanzenbacher · Schwieberdingen, DE

Key dates

• Filing date: Jul 6, 1976
• Grant date: Feb 7, 1978
• Expiry date: Jul 6, 1996

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T137/87185
• WIPO field: Mechanical elements
• WIPO sector: Mechanical engineering

Abstract

A hydraulic control system has a three-position valve which in its central position disconnects the high-pressure and low-pressure sides of a pressure source from outlet lines but connects these sides of the source together through a low-pressure valve. Moved to either of its end positions the valve is disconnected from between the sides of the pressure source and the output lines are connected to the high-pressure and low-pressure source sides. A pressure-limiting valve is connected between the sides of the source. In addition, the high-pressure side is connected via pressure-reducing valve and a restriction to a pair of pilot valves which are in turn connected to the low-pressure side. These pilot valves are also connected to opposite chambers of a pilot cylinder that controls the valve body. The pressure-reducing valve between the pilot valves and the high-pressure side maintains a medium-pressure level in the system when the valves move from its central position.