Power plants – Pressure fluid source and motor – With control means for structure storing work driving energy
Patent
1991-03-07
1992-10-06
Denion, Thomas E.
Power plants
Pressure fluid source and motor
With control means for structure storing work driving energy
91446, 1375961, F16D 3102
Patent
active
051521423
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention generally relates to negative load controls and more particularly relates to compensated negative load controls, which divert, during control of negative load, the energy of such load to perform useful work in a hydraulic system, without the energy of the negative load being converted into heat by throttling.
BACKGROUND ART
Without exception all of the hydraulic controls of the present art are based on the principle of throttling, which converts the energy of flow and pressure into heat.
In this specification a negative type load means an aiding type load, while a positive type load means a resistive type load that is a load which absorbs energy supplied from the pump to perform useful work.
During control of positive load, depending on the type of hydraulic system and especially on the type of pump used in the system, various amounts of throttling take place. The less the amount of throttling used in control of a positive load the more efficient the fluid power and control system.
The amount of throttling in control of positive type loads was greatly reduced by the introduction of load responsive, or load sensing systems, in which only a relatively small amount of throttling takes place such as, U.S. Pat. No. 3,470,694, issued Oct. 7, 1969 to T. Budzich.
Through application of the principle of variable pressure differential to such a load responsive system, the efficiency of such system can be still further increased by further reduction in throttling and the already high quality of the control of such a load responsive system and its valves can be further increased. Such a system is shown in U.S. Pat. No. 4,285,195, issue Aug. 25, 1981 to T. Budzich. However, those increases in efficiency and reduction in throttling of these load responsive systems only applies to the control of positive load, while the control of negative load, in all known compensated systems of the present art is done by totally converting, by the throttling process, the pressure-flow energy directly into heat. A typical system is shown in U.S. Pat. No. 3,744,517, issued July 10, 1973 to T. Budzich. Various negative load controls of the present art have this common feature. The only difference between those controls being the quality of the control, which for example was greatly improved through application of the concept of compensation.
Generation of heat, by throttling the fluid, not only represents a reduction in the efficiency of the system, but also introduces other parasitic effects, like for example an increase in temperature of the working fluid, necessitating the use of heat exchangers of various types and generally reducing the useful life of the fluid. Like, for example, the hydraulic oil and increasing the hazard to the operators of such systems.
DISCLOSURE OF THE INVENTION
In one aspect of the present invention a fluid power and control system is provided having a valve assembly interposed between an outlet port of a fluid motor which controls a negative type load and subjected to negative load pressure, fluid exhaust means maintained at a relatively low pressure level and absorbing means maintained at a relatively high variable pressure level during control of the negative load. The valve assembly comprises flow control means operative to control the velocity of fluid flow from the fluid motor in response to an external control signal so that the velocity of the fluid motor can be controlled at a relatively constant level proportional to the magnitude of the external control signal and independent of the magnitude of the negative load pressure. The flow control means includes flow sensing means for sensing the magnitude of the fluid flow from the fluid motor, fully throttling means for directing fluid flow from the fluid motor to the exhaust means, and recovery means for diverting on a priority basis fluid flow from the fluid motor to the absorbing means. The recovery means is operatively responsive to the flow sensing means.
It is therefore a principal object of this invention to u
REFERENCES:
patent: 3470694 (1969-10-01), Budzich
patent: 4147178 (1979-04-01), Budzich
patent: 4180098 (1979-12-01), Budzich
patent: 4249570 (1981-02-01), Budzich
patent: 4285195 (1981-08-01), Budzich
patent: 4330991 (1982-05-01), Budzich
patent: 4437307 (1984-03-01), Budzich
patent: 4674280 (1987-06-01), Stuhr
patent: 4741248 (1988-05-01), Budzich
patent: 4799420 (1989-01-01), Budzich
Burrows J. W.
Caterpillar Inc.
Denion Thomas E.
Lopez F. Daniel
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