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. 05, 1980
Filed:
Apr. 09, 1979
John C Miller, Algoma, WI (US);
C. A. Lawton Company, Depere, WI (US);
Abstract
A method and apparatus for linear and nonlinear control of a hydraulic press is provided with a feedback loop allowing the operation of a variable displacement pump to be selectively controlled with respect to either hydraulic pressure moving a piston in a cylinder, or the velocity of the piston. During controlled movement of the piston, a directional valve blocks a pump compensator so that the pump operates as a fixed displacement pump to provide fast response to feedback signals. Simultaneously, the directional valve connects a proportional pressure controller to a relief valve. During a period when the piston is maintained in fixed position, the directional valve is switched so that the proportional pressure controller now controls the pump compensator and the relief valve is blocked, so that energy consumption is substantially reduced. Zero or low piston velocity is obtained by means of a sequence valve which blocks hydraulic supply to the piston below a designated pressure to eliminate the influence of inherent system pressure which may cause piston movement in the absence of sufficient material pressure.