HYDRAULIC CIRCUIT

Abstract

A hydraulic circuit arrangement with a fixed displacement pump driven by an electric motor, a lifting cylinder, a load-holding valve arranged in the line between pump and lifting cylinder, a priority valve, which is acted upon by the pump, being arranged between pump and load-holding valve and distributing the volumetric flow flowing from the pump to the lifting cylinder, on the one hand, and to at least one further consumer of a load-sensing system, on the other hand. In the first of its two extreme positions, the priority valve connects both the lifting cylinder and the at least one further consumer in each case to the pump and, in the second of its two extreme positions, only connects the at least one further consumer to the pump while the lifting cylinder is completely cut off.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a circuit arrangement for a battery-driven forklift truck;

FIG. 2 is a schematic of a circuit arrangement;

FIG. 3 is a schematic of an alternative circuit arrangement; and

FIG. 4 is a schematic of an alternative circuit arrangement.

Claims

1. Hydraulic circuit arrangement with a fixed displacement pump (P) driven by an electric motor (M), and a lifting cylinder (HZ), where, in order to recuperate energy, the electric motor CM) can be operated as a generator (G) and the pump (P) can be operated as a hydraulic motor in order to recuperate potential energy of the lifting cylinder (HZ), and with a load-holding valve (LHV) arranged in the line between pump (P) and lifting cylinder (HZ), characterized in that a priority valve (PRV) which is acted upon by the pump (P) is arranged between pump (P) and load-holding valve (LHV) and distributes the volumetric flow flowing from the pump (P) to the lifting cylinder (HZ), on the one hand, and to at least one further consumer of a load-sensing system (LSS), on the other hand,in that, in the first of its two extreme positions, the priority valve (PRV) connects both the lifting cylinder (HZ) and the at least one further consumer in each case to the pump (P), andin that, in the second of its two extreme positions, the priority valve (PRV) only connects the at least one further consumer to the pump (P) while the lifting cylinder (HZ) is completely cut off.

2. Hydraulic circuit arrangement according to claim 1, in which the priority valve can be acted upon in one direction by the pressure of the pump (P) and in the other direction by the maximum load pressure in the load-sensing system (LSS) via the shuttle valve (WV) thereof.

3. Hydraulic circuit arrangement according to claim 1, in which a switching-off valve (ASV) is provided with which the priority valve (PRV) can be switched into the second extreme position.

4. Hydraulic circuit arrangement according to claim 1, in which, when the lifting cylinder (HZ) is lowered, its load pressure is tapped off for the purpose of controlling the priority valve (PRV).

5. Hydraulic circuit arrangement according to claim 4, in which the load-holding valve (LHV) is designed for tapping off the load pressure of the lifting cylinder (HZ).

6. Hydraulic circuit arrangement according to claim 1, in which switching means are provided which permit small loads to be lowered when the pressure of consumers connected in the load-sensing system (LSS) predominates over that of the lifting cylinder (HZ).

7. Hydraulic circuit arrangement according to claim 6, in which the switching means for lowering small loads have a position switch (PS) which recognizes the switching position of the priority valve (PRV).

8. Hydraulic circuit arrangement according to claim 6, in which the switching means for lowering small loads have pressure sensors which measure the pressures in the lifting cylinder (HZ) and the load pressure in the load-sensing system (LSS).

9. Hydraulic switching arrangement according to claim 8, in which one of the pressure sensors measures the maximum load pressure in the load-sensing system (LSS).

10. Hydraulic circuit according to claim 6, in which the switching means for lowering small loads have a load-lowering valve (LSV) which, on the basis of the position signal output by the position switch or of the signals output by the pressure sensors, permits a lowering of the lifting cylinder without recuperating energy.