The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 12, 1980
Filed:
Jun. 22, 1979
Karlmann Hamma, Tettnang, DE;
Zahnradfabrik Friedrichshafen AG, Friedrichshafen, DE;
Abstract
A drive system has an engine that operates a control pump and a hydraulic variable-displacement drive pump having a control element and connected to a hydraulic motor. A servocylinder operates the control element of the drive pump and is pressurized through a control line connected to the control-pump output. A control valve is connected between the control line and the sump of the system and is connected to the hydraulic line between the motor and the drive pump to reduce pressure in the control line when the higher pressure of the line between the drive pump and the motor rises within a predetermined range. Thus it is possible with a substantially constant engine speed to produce a substantially constant output torque, with only the displacement of the pump and pressure in the lines between the pump and the motor varying by appropriate control of the control-line pressure.