Hydraulic circuit with load sensing feature
AssigneeCase Corporation
InventorPatrick M. Lourigan
Life of this patent
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Abstract
A hydraulic circuit has a first PV pump connected to a valve group for powering a plurality of hydraulic mechanisms connected to the group, and a second PF pump connected in the circuit. In the improvement, a hydraulic line extends between the second pump and the valve group and there is a conductor sensing a mechanism load pressure. A valve network directs flow from the second pump to the valve group when the difference between the pressure in the hydraulic line and the load pressure declines below a predetermined value. Such decline "signals" that the mechanisms require more fluid than is available from the first pump alone. A new method for supplementing the flow of a first pump with that of a second pump is also disclosed.
Claims13
In a hydraulic circuit having (a) a first pump connected to a valve group for powering a plurality of hydraulic mechanisms connected to the group, and (b) a second pump connected in the circuit, the improvement comprising:
- a hydraulic line extending between the second pump and the valve group;
- a conductor sensing a mechanism load pressure;
- and wherein:
- the valve group includes at least two control valves, each controlling a separate hydraulic mechanism;
- and
- the conductor is at a load pressure when both control valves are actuated;
- the circuit includes a valve network directing flow from the second pump to the valve group when the difference between the pressure in the hydraulic line and the load pressure declines below a predetermined value,
- whereby the flow from the second pump supplements the flow from the first pump.
In combination, a machine and a hydraulic circuit having (a) a first pump connected to a valve group for powering a plurality of hydraulic mechanisms connected to the group, and (b) a second pump connected in the hydraulic circuit, the improvement wherein:
- the second pump is connected to a branch circuit having a first line connecting the second pump to the valve group and a second line connecting the second pump to a circuit device;
- the second line includes a diverter valve having primary and secondary input ports for sensing primary and secondary pilot pressure, respectively;
- the primary input port is at the load pressure of one of the mechanisms and the secondary input port is at the pressure in the second line;
- the diverter valve directs the flow of the second pump to the first line when the difference between the pressure at the secondary input port and that at the primary input port is less than a predetermined value;
- and
- the machine includes an accessory valve connected to the first line in parallel with the valve group.
A method for supplementing flow in a hydraulic circuit having (a) a first pump connected to a valve group for powering a plurality of hydraulic mechanisms connected to the group, the valve group including at least two control valves each controlling a separate hydraulic mechanism, and (b) a second pump connected in the circuit, the method comprising the steps of:
- sensing the pressure in a hydraulic line extending between the second pump and the valve group;
- sensing a mechanism load pressure;
- actuating the two control valves;
- and
- directing flow from the second pump to the valve group when the difference between the pressure in the hydraulic line and the load pressure declines below a predetermined value,
- thereby using the flow from the second pump to supplement the flow from the first pump.
Dependencies are inferred from the claim text.