Motors: expansible chamber type – With motive fluid valve – Pilot valve
Patent
1998-06-15
2000-03-21
Nguyen, Hoang
Motors: expansible chamber type
With motive fluid valve
Pilot valve
1376256, 251 35, F15B 1108
Patent
active
060389575
DESCRIPTION:
BRIEF SUMMARY
This invention relates to control valves and relates more particularly but not exclusively to flow-amplifying hydraulic control valves.
In the field of hydraulic control valves intended to pass controllably variable flow rates (as distinct from valves which are simply "open/shut" valves), it is generally easier to provide precise control of small flow rates whereas the loads require high flow rates. In principle, a solution to this requirement is the provision of a flow amplifier, but a flow amplifier requires to be capable of accurately tracking a variable control input. A flow amplifier should also desirably avoid undue complexity and cost, be reliable, and easily adjustable to compensate for performance variations due, for example, to tolerance limitations in manufacture.
According to a first aspect of the present invention there is provided a control valve for controlling the flow of fluid through the valve in proportional dependence upon a variable control input, the control valve comprising flow control means providing a controllably variable fluid throughput in use of the control valve, said throughput being controlled in dependence upon pressure in a control chamber fed with fluid tapped from the upstream side of the valve via a control element, fluid being drained from the chamber under external control to vary pressurisation of the chamber as the control input to the control valve, the control element being coupled to the flow control means to vary the feed to the control chamber in dependence upon the fluid throughput and in a sense providing negative feedback.
The fluid whose flow is to be controlled by the control valve is preferably a hydraulic fluid.
The control element is preferably a variable flow restriction disposed to provide a flow restriction which reduces with increased fluid throughput through the flow control means of the valve, the flow restriction conversely increasing with reduced fluid throughput through the flow control means of the valve.
According to a second aspect of the present invention there is provided a flow-amplifying hydraulic control valve for controlling the flow of fluid through the valve in proportional dependence upon a variable control flow which is volumetrically small relative to the controlled throughflow, the control valve comprising a valve housing having a fluid inlet and a fluid outlet mutually joined by an internal fluid passage, a valve seat bounding the internal fluid passage, a bore in the valve housing, the bore intersecting the fluid passage in the region of the valve seat, an obturator controllably movable along the bore towards and away from the valve seat respectively to reduce and to increase the flow of fluid through the valve in use of the control valve, the obturator and the valve seat being shaped and dimensioned such that a forward pressure differential across the valve arising from the fluid pressure in the fluid inlet instantaneously exceeding the fluid pressure in the fluid outlet tends to increase displacement of the obturator from the valve seat and thereby tends to increase fluid throughput, the end of the obturator remote from the valve seat and that end of the bore together defining a variable-volume control chamber, pressurisation of the control chamber tending to decrease displacement of the obturator from the valve seat thereby to tend to decrease fluid throughput, a fluid conduit tapping the internal fluid passage between the fluid inlet and the valve seat, the fluid conduit feeding tapped fluid to the control chamber, a variable flow restriction means in the fluid conduit to provide variable restriction of fluid being fed to the control chamber, the variable flow restriction means being coupled to the obturator such that increased displacement of the obturator from the valve seat causes the flow restriction means to present a reduced restriction to flow of fluid into the control chamber and, conversely, such that decreased displacement of the obturator from the valve seat causes the flow restriction means to present an increa
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patent: 4955283 (1990-09-01), Hidaka et al.
patent: 4958553 (1990-09-01), Ueno
patent: 5170692 (1992-12-01), Lonnemo
patent: 5207059 (1993-05-01), Schexnayder
Hydraulic "Transistor", Machine Design, vol. 64, No. 11, p. 70, Jun. 11, 1992.
Ertmann Alexander Gareth
Sadler Mark
Commercial Intertech Limited
Nguyen Hoang
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