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:
Apr. 09, 1996
Filed:
May. 27, 1994
Ralf Baginski, Neetze, DE;
Hans-Peter Claussen, Norderstedt, DE;
Andreas Klatt, Hamburg, DE;
Hans-Joachim Doss, Hamburg, DE;
Jochen Korner, Hamburg, DE;
Jungheinrich Aktiengesellschaft, Hamburg, DE;
Abstract
A hydraulic lift device for battery operated industrial trucks comprising a hydraulic ram, a hydraulic machine operating as a pump in a load raising cycle and as a motor in a load lowering cycle, a separately excited DC machine operating as a motor in the load raising cycle and as a generator in the load lowering cycle, and energy recovering circuitry which is fed by the DC machine in the load lowering cycle. A load holding valve is disposed in the fluid path between the hydraulic ram and the hydraulic machine. Speed of the DC machine is set by a speed control. A separate field current control includes a desired value setting circuit for determining a desired value for the field current (I.sub.FSoll) from a predetermined relationship between the speed (n.sub.Ist) and the armature current (I.sub.ASoll). Power switches are associated with the field winding and the armature, and are actuated by the current control. The power switches are arranged and controlled such than the intensity and the direction of the current through the armature and field winding are defined. The current control comprises a directional setting control for the lowering and raising cycle generating signals to control the load holding valve.