Hydraulic lift device for battery operated industrial trucks or the like

US5505043A · kind A · utility

Assignee

• Jungheinrich AG · DE

Inventors

• Ralf Baginski · Bleckede, DE
• Hans Claussen · Berlin, DE
• Andreas Klatt
• Hans-Joachim Doss · Hamburg, DE
• Jochen Körner · Viernheim, DE

Key dates

• Filing date: May 27, 1994
• Grant date: Apr 9, 1996
• Expiry date: May 27, 2014

Classification

• Technology area (CPC B): Performing Operations; Transporting
• CPC primary: B66F9/20
• WIPO field: Handling
• WIPO sector: Mechanical engineering

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 c…