Surgery – Antigravational systems
Reexamination Certificate
1999-02-26
2001-05-08
Michalsky, Gerald A. (Department: 3753)
Surgery
Antigravational systems
C137S596170, C137S627500
Reexamination Certificate
active
06228019
ABSTRACT:
DESCRIPTION OF INVENTION
This invention relates to a valve assembly and more particularly but not exclusively to a valve assembly for use in controlling a parameter such as gas pressure or flow, in a life support system for a member of an aircrew of a high performance aircraft.
In a life support system for a pilot, one or more control valves are required to enable pressurised gas to be delivered to and from the G-suit, and the breathing means from a gas supply. The gas for the breathing means at least, may be supplied from an oxygen concentrating system or from a ceramic or other oxygen generating system. The gas for the G-suit is usually pressurised air.
In each case, it is highly desirable that gas is efficiently used.
DESCRIPTION OF PRIOR ART
Valve arrangements are known which include one or more valve members which selectively connect the breathing system i.e. breathing mask and counterpressure garment, or G-suit, to either a gas supply or to a vent means to allow inflation and deflation of the counterpressure garment/G-suit. However, due to design inadequacies, some known valve arrangements for this purpose, can during change over from inflation to deflation of the compensating garment, momentarily connect the gas supply to vent, thus wasting gas.
SUMMARY OF THE INVENTION
According to the invention we provide a valve assembly comprising an actuator and a valve, the valve comprising a valve body having first and second ports and a valve seat between the first and second ports, a valve member carried on a valve stem and the valve stem being moveable to move the valve member at least one of into or out of engagement with the valve seat to prevent or permit communication between the first and second ports wherein the actuator comprises a stepper motor the rotational movement of which is converted to linear movement of the valve stem by a transmission means, the transmission means being adapted to maintain the valve stem in a position to which it is moved by the operation of the actuator whereby the transmission means is a non back-driveable transmission.
For example, the stepper motor may comprise an output shaft having a threaded region, and the transmission means including a female threaded member carried on the shaft and moveable along the shaft as the shaft is rotated, and the transmission means further comprising means to couple the female threaded member to the valve stem.
If desired, the valve member may be moveable relative to the valve stem and biasing means, such as a spring, may be provided to bias the valve member into or out of engagement with the valve seat.
Although most conveniently, the biasing means comprises a spring although any other suitable means, mechanical or otherwise for applying a biasing force to the valve member may alternatively be provided.
The valve stem may carry a stop element which moves the valve member against the biasing means out of or into engagement with the valve seat respectively when the valve stem is moved by the stepper motor.
Thus the valve member may “float” on the valve stem. Any tendency there may be for the valve member to remain in the position to which it is biased by the biasing means is positively overcome as the stop element positively moves the valve member against the force of the biasing means when the actuator is operated. Any tendency there may be for the valve member to remain in the position to which it is moved by the stop element when the stop element is removed, can be overcome by providing for the biasing means to act between a reaction member carried on the valve stem, and the valve member, so that further movement of the valve stem will cause an increasing biasing force to be exerted on the valve member.
The valve member is preferably slideable relative to the valve stem and the valve stem may be moveable bi-directionally by the actuator.
So that the actuator does not have to exert any force against the fluid pressure within the valve, but only against the biasing means, the valve member may be mounted by or integral with a diaphragm or piston which is provided to close a chamber within the valve body, with the fluid pressure at one of the first and second ports being communicated to the chamber. Thus the valve is substantially pressure balanced by equal fluid pressure on each side of the diaphragm or piston.
Whereas the valve may be a simple open/closed type valve, if desired a third port may be provided and a second valve seat may be provided between the second and third ports, there being a second valve member engageable with the second valve seat to prevent communication between the second and third ports, and means to move the second valve member out of engagement with the valve seat to permit communication between the second and third ports, the second valve member being carried on and being moveable relative to a valve stem, and biasing means being provided to bias the second valve member into or out of engagement with the second valve seat. The stem may carry a stop element which moves the second valve member against the biasing means out of or into engagement with the second valve seat respectively when the valve stem is moved by an actuator.
If desired, the valve stems on which the first and second valve members are carried may be independently moveable by respective actuators, but preferably a less expensive and more compact arrangement is that the valve stems on which the first and second valve members are carried are connected or are integrally provided and moved by a common actuator.
Thus the valve stems may be moveable to a position in which both of the first and second valve members are urged into engagement with their respective first and second valve seats by the biasing means so that the first, second and third ports are all isolated from each other, and when the actuator moves the valve stems, only one of the first and second valve members is moved out of engagement with its respective valve seat depending upon the direction of movement of the valve stems to permit of communication between the first or third port and the second port, whilst the other of the valve members is maintained in engagement with its respective valve seat by its respective biasing means to maintain the third or first port respectively isolated from the first or third, and second ports.
When the actuator is operated to move the valve stems in an opposite direction, the first or second valve member may thus be moved by its respective biasing means back into engagement with its respective first or second valve seat to isolate the first or third port from the second port before the second or first valve member is moved by the stop element against the force of its respective biasing means out of engagement with the respective third or first port.
Again, to prevent the actuator having to move the valve stems against fluid pressure in the valve, desirably each of the first and second valve members is mounted by or is integral with a diaphragm or valve which is provided to close a respective chamber within the valve body, and the fluid pressure at the second port being communicated to each of the respective chambers.
The valve body may be arranged so that the first and third ports are arranged generally at one side of the valve body and the second port is arranged at an opposite side of the body although other arrangements are no doubt possible.
The valve assembly of the invention may be a control valve assembly adapted to control fluid pressure or flow in a system e.g. which requires to be pressurised and depressurised, wherein the first port is connected to a supply of pressurised gas, the second port to the system and the third port to a vent, whereby when the first and second ports are in communication the system is pressurised, and when the second and third ports are in communication the system is vented, and the valve preventing communication between the first and third ports.
One application for the valve assembly is in a system comprising a G-suit of a life support system for an aircrew member and/or a breathing
Phillips Robert John
Stuckey Christopher John
Marshall O'Toole Gerstein Murray & Borun
Michalsky Gerald A.
Normalair-Garret (Holdings) Limited
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