US 4,024,710 A · Load sensing hydraulic circuit having power matching means

Abstract

A load sensitive hydraulic circuit for material handling equipment is energized by a prime mover. The hydraulic circuit includes variable displacement pumps coupled to the prime mover and having pressure and flow compensating control means for varying the volumetric output. Each pump is connected to a valve bank which controls various hydraulic actuators of the material handling equipment. Load pressure feedback is provided to the pump compensators for establishing pump flows to operate the actuators at a fixed pressure differential in excess of load pressure. The valve banks contain pressure compensated valves for providing desired fluid flow rates and speeds in the hydraulic actuators. Means are provided to sense reductions in the prime mover speed resulting from excessive hydraulic loads. The means is connected to the pump compensators for simultaneously adjusting the volumetric output of the hydraulic pumps at the preselected pressure differential over the load pressure and power demands on the prime mover so that demands on the prime mover are matched to its available power output.

Claims18

Dependent claims

A hydraulic circuit for operating a plurality of hydraulic actuators connected to loads, the circuit being powered by a prime mover engine and comprising:

variable displacement hydraulic pump means drivable by the engine;
signal responsive pump displacement control means operatively associated with the hydraulic pump means for controlling the volumetric output of the pump means;
a valve means connected to the pump means and having a plurality of valve sections operatively associated with the hydraulic actuators for controlling flow to energize the actuators to drive the loads;
means coupled to each of the valve sections and to the pump displacement control means for providing a load pressure signal to the displacement control means for causing the latter to adjust the volumetric output from the pump means to a quantity sufficient to provide a pump means output pressure having a preselected pressure differential over the load pressure;
and
speed sensing means operatively associated with the engine for providing a signal indicative of the engine speed, the speed sensing means being operatively associated with the displacement control means for simultaneously adjusting the volumetric output of the pump means at the preselected pressure differential over the load pressure and the power demand on the engine responsive to a change in engine speed.

3 more elements

A hydraulic circuit for operating a plurality of hydraulic actuators connected to loads, the circuit being driven by a prime mover engine and comprising:

first and second variable displacement hydraulic pumps coupled to the engine;
first and second signal responsive pump displacement control means operatively associated with the first and second pumps, respectively, for controlling the volumetric output of the pumps;
first and second valve banks connected to the first and second pumps, respectively, each of the valve banks having a plurality of pressure compensated valve sections operatively connected with the hydraulic actuators for energizing the actuators to drive the loads;
means coupled to each of the valve sections and to the pump displacement control means of the corresponding pump for providing a load pressure signal to the displacement control means for adjusting the volumetric output from the pumps to a quantity sufficient to provide a pump output pressure having a preselected differential over the load pressure;
and
speed sensing means operatively associated with the engine for providing a signal indicative of the engine speed, the speed sensing means being operatively associated with the displacement control means for simultaneously adjusting the volumetric output of both of the pumps at the preselected pressure differential over the load pressure and the power demand on the engine responsive to a change in engine speed.

3 more elements

Dependencies are inferred from the claim text.

Load sensing hydraulic circuit having power matching means

Life of this patent

Load sensing hydraulic circuit having power matching means

Life of this patent

Abstract

Claims18