Motors: expansible chamber type – With motive fluid valve – Relatively movable serial valves
Reexamination Certificate
1998-12-07
2001-02-13
Ryznic, John E. (Department: 3745)
Motors: expansible chamber type
With motive fluid valve
Relatively movable serial valves
C091S536000, C137S625660, C137S625600
Reexamination Certificate
active
06186045
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to fluid control systems, and more particularly multiplexed hydraulic control systems.
BACKGROUND OF THE INVENTION
In the art of hydraulic control systems for control of engines, the trend is toward control over more mechanical variables in the engine to attempt an increase in engine efficiency and/or performance. Mechanical variables can include air and fuel valves, variable stator vanes, engine variable geometry, and the like. In prior engines, the common approach of controlling these mechanical variables has been to provide a dedicated hydraulic control for each mechanical variable. However, with the increased number of hydraulic controls has come undesirable increases in weight and size of the overall engine and a decrease in reliability. Such increases in weight and size also decrease the fuel efficiency of engines, particularly for gas turbine aircraft engines.
The concept of multiplexing a single hydraulic or pneumatic control to a plurality of channels is known as exemplified by Leeson et al., U.S. Pat. No. 4,984,505, the disclosure of which is hereby incorporated by reference. Multiplexed systems eliminate or reduce the need for several separate hydraulic controls while increasing overall reliability. Leeson illustrates such a multiplexing configuration in which a selectively positioned modulating valve moves linearly with respect to a rotating and multiplexing sleeve. The multiplexing sleeve periodically or sequentially delivers a modulated flow to individual output ports. In other multiplexing schemes, the multiplexer comprises a linearly moving valve as exemplified by McLevige et al., U.S. Pat. No. 5,048,394, the disclosure of which is also hereby incorporated by reference. In both rotary and linear multiplexing configurations, an intermediate second stage valve may be interposed between each multiplexer output and each actuator to integrate and/or amplify the signal to the actuator.
While these multiplexing systems reduce the number of hydraulic controls and increase reliability, a drawback with these prior hydraulic multiplexing configurations is that the modulating valve and multiplexer are frequently modulating flow to the second stage valves to correct for error and/or to maintain the last position of the intermediate second stage valves. Such frequent modulated flow may be necessary, for example, to correct for gradual fluid seepage from the control chamber of the second stage valve, which can cause the second stage to fall out of the desired position. These frequent modulations may cause fatigue and wear on the components of the system which may in turn reduce the life-span of the system. Such frequent modulations also can require a large quantity of electrical power.
There are also known attempts to configure a multiplexing scheme with latching valves that do not need updating to hold the last valve position. Such a configuration is exemplified in Veilleux, Jr. et al., U.S. Pat. No. 5,551,478. In Veilleux, a plurality of latching second stage valves switch between two positions by application of high pressure signals to one of two control ports corresponding with the two valve positions to change fluid flow to a corresponding actuator. A high pressure pulse on one port switches the valve from a first to a second position and the application of a high pressure pulse to the second port switches the valve back to its first position. The latching valves use internal ports and switches to low and high pressure inputs and an internal spring biasing mechanism to latch the valves in the current position until the appropriate high pressure pulse is delivered to the appropriate control port. However, a problem with this prior latching valve multiplexing system is its size, weight, and complexity, which are a disadvantage in aircraft systems and other systems where smaller size and weight is highly desired. In particular, Veilleux requires a 4-way multiplexing valve that has two control ports for each second stage latching valve. Each latching valve likewise has two control chambers and ports connected by separate conduits to the multiplexing valve. Furthermore, each latching valve requires two high pressure inputs and two low pressure inputs to maintain the latched position and produce an output to an actuator. The numerous ports increase the number of connecting conduits, the overall length or size of the multiplexing and latching valves, and therefore the complexity and weight of the system. Yet another problem with Veilleux is that the disclosed multiplexed fluid control system only provides positive high pressure pulses, and therefore it is not compatible with other variably positioned second stage valves which operate on positive and negative fluid signals. Such variably positioned second stage valves offer better control over mechanical variables which prefer more accurate control.
SUMMARY OF THE INVENTION
It is a general aim of the present invention to overcome these and other deficiencies existing in the art.
It is another general aim of the present invention to provide a practical and reliable multiplexed fluid control system that utilizes latching type valves.
It is therefore an object of the present invention to reduce the complexity and size of a latching valve for use in multiplexed fluid control systems.
In that regard, it is another object of the present invention to reduce the number of ports and connections necessary to latch a second stage valve.
It is another object to provide a latching valve that operates on negative and positive fluid signals from a 3-way multiplexing valve that alternatively pressures or exhausts a single port.
It is therefore a feature of the present invention to provide a latching valve in a channel of a multiplexed fluid control system that derives a holding or latching force from the working output pressure or flow between the latching valve and a corresponding actuator. The latching valve produces a working output flow that is determined by the current state of the valve. The current state of the valve is determined by the last fluid signal received in the channel and is held by the latching force.
It is another feature of the present invention to provide a simplified latching valve in a multiplexed fluid control system. The latching valve provides a control chamber for receiving fluid signals from the multiplexing and modulating means. The latching valve is switchable between two states by receipt of fluid signals in the control chamber. The state of the latching valve controls a working output fluid flow to an associated actuator. The latching valve further has a bleed conduit which connects the working output flow to the control chamber to maintain the fluid pressure in the control chamber and thereby latch the valve in its current state.
It is an aspect of the present invention that the bleed conduit has a restricted size to limit the flow rate through the bleed conduit so that fluid signals from the multiplexing valve cause the valves to switch states.
It is another feature of the present invention to provide a latching valve for a fluid control system that has a movable valve operator translatable between two positions within a valve body for regulating working fluid flow to a corresponding actuator. The valve body defines an inlet, an outlet, a control chamber, and a working output. The valve operator has a first position, which connects the inlet to the working output, and a second position, which connects the outlet to the working output. The position of the latching valve is controlled by fluid pressure in the control chamber. The latching valve also includes a bleed conduit connecting the working output to the control chamber for latching the valve in its current position.
It is another feature of the present invention that the latching valve is adapted to use positive or high-pressure fluid signals and negative or lower pressure fluid signals of a 3-way multiplexing valve. The latching valve may therefore be used in a multiplexed control system wit
Leydig , Voit & Mayer, Ltd.
Ryznic John E.
Woodward Governor Company
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