Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1992-10-15
1995-03-07
Look, Edward K.
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60459, 91511, 91459, F16D 3102, F15B 1100
Patent
active
053946960
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a hydraulic system for feeding hydraulic fluid to a plurality of loads from a common pump.
U.S. Pat. No. 3,987,622 discloses a hydraulic system of the described type wherein the pressure extant at the pump as well as the highest load pressure are applied to a control valve. When the pump cannot furnish the volume flow required by the control valves and their associated consumers, the pressure difference between the pressure of the pump and the highest load pressure is reduced. As a result, the control valve reduces its supply to control pressure transducers by means of which the valves associated with the consumers are actuated. As a result, the flow through the valves is restricted. This restriction, however, becomes effective only when an excess demand already exists. When this restriction becomes effective, the consumers can no longer be controlled by means of their control valves.
In the system known from U.S. Pat. No. 4,856,278, the electrical control signals of the actuated multipleway valves are added. The volume flow which corresponds to the sum of the control signals is compared with the highest possible pump flow. When the sum of the control signals exceeds the possible pump flow, the control signals are reduced. In this system, it is necessary to evaluate all the control signals. Furthermore, it is necessary by means of a computer to take into consideration the dependence of the valve flows on the control signals.
It is the object of the invention to configure the hydraulic systems so that it is not subject to fluctuations, and that, moreover, it becomes possible to effect a desired weighting or apportioning and adjustment of the individual consumer flows relative to the operating parameters of the pump.
SUMMARY OF THE INVENTION
The above object is achieved with the present invention, which provides the advantage that in contrast to existing hydraulic systems, the operational condition of the pump is determined directly. Therefore, it is possible effectively to control fluctuations of the operational condition.
When the sum of the consumer flows, as determined by the setting of the valves associated with the consumers, rises above the highest quantity which the pump can deliver, the actuating or control signals of the valves will be reduced. By measuring the pump flow it can always be determined, whether the supply of the individual consumers is ensured. An undersupply is thereby avoided. The reduction of the consumer flows may occur proportionately. However, a reduction by priorities is also possible, for example, when a particular consumer should not reduce its speed relative to other consumers.
However, this entails adjustment of the control circuit which is the subject matter of this invention in exceptional cases only, and then only when the deliverable pump flow is insufficient to satisfy the consumer flows set by the respective valves, the total consumer flows constituting the actually delivered quantity. In this event, the actually delivered quantity will be lowered by reducing the respectively supplied consumer flows.
To measure the quantity actually delivered by the pump, standard measuring instruments are available. In particular, it is possible to measure the actually delivered quantity by mounting a throttle or diaphragm into the main output line of the pump (overall supply line), ahead of any consumer lines branch off leading to the valves associated with individual consumers, and to measure any pressure drop at such diaphragm. The actually delivered quantity, related to the predetermined possible delivery at a predetermined speed, however, can also be determined by the other embodiments as disclosed herein.
The adjustment of the consumer flows relative to the predetermined deliverable pump flow is accomplished by adjusting the valves associated with the consumers. In principal, it may be assumed that these valves are adjusted from the outside, that is by hand or electromagnetically or hydraulically by external input
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Eich Otwin
Salz Franz-Peter
Barmag AG
Look Edward K.
Nguyen Hoang
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