Gas operated ejection system

A gas operated release or ejection system which compensates for changes in pressure applied to a load being ejected. The pressure regulator compensates for decreases in pressure through a pressure regulating valve, and compensates for increases in pressure through a pressure relief valve.

BACKGROUND OF THE INVENTION 
The present invention relates to gas operated ejection or release systems, 
and particularly though not exclusively to a system for ejecting loads 
from an aircraft. 
It is an object of the present invention to provide a gas-operated release 
or ejection system in which changes in output pressure due to temperature 
and supply pressure variations are reduced. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a gas operated 
release or ejection system comprising a pressure vessel arranged to 
discharge along a pathway including a pressure regulating valve, a 
pressure relief valve and a control valve to a release or ejection 
mechanism. The ejection mechanism may conveniently comprise an ejection 
piston, the speed of travel of which is related to the speed at which the 
load is ejected. 
Conveniently, the control valve may be solenoid actuated to move between a 
closed position and an open position on receipt of an electrical signal. 
It is desirable for a control valve member to have to move only a small 
distance between the closed and open positions, but for this movement to 
create a large effective aperture in the pathway to the ejection mechanism 
in the open position. This is because it is necessary to allow a large 
volume of gas to pass in a very short period in which only a relatively 
small movement of the valve member is practicable. 
To prevent leakage through the pressure regulating valve increasing the 
pressure excessively on the downstream side, the pressure regulating valve 
may have a compliant or resilient seal, for example a compliant or 
resilient valve seat. Suitable material would be a polyimide, such as the 
material known as Vespel (Trade Mark). This has an acceptably low creep 
rate. 
The control valve may comprise a valve body and pressure responsive means 
at least partially defining first and second chambers, having first and 
second inlet ports, respectively, defined in the valve body; a valve 
assembly to open with and to control fluid flow from the first inlet port, 
the valve assembly being actuated in response to movement of the pressure 
responsive means; and an auxiliary valve operable to communicate the 
pressure at the first inlet port to the second inlet port to move the 
pressure responsive element to open the valve assembly. 
The pressure responsive means could be any arrangement which reacts to a 
change in pressure by movement. For example, the pressure responsive means 
are preferably a piston and cylinder arrangement. As an alternative, the 
pressure responsive means could be a bellows arrangement by which one 
chamber is isolated from the other. 
As, in use, the control pressure is applied at the inlet port, it maintains 
the pressure responsive means in a position in which the control valve is 
closed. To achieve this, the pressure applied to the pressure responsive 
means acts on a area that is greater than the area of the control valve 
exposed to the same pressure. Thus, once the same pressure is applied to 
the second inlet port, it neutralises the force applied by the same 
pressure in the first chamber as it acts on an equivalent area. In this 
condition the pressure on the second chamber is able to open the control 
valve in the absence of any net counteracting force acting on the piston 
or other pressure responsive means. 
Preferably, the valve assembly includes a valve member and a valve seat, 
the valve member engaging the valve seat by means of an engaging region 
that faces in the opposite direction to the control flow of fluid through 
the valve. 
The valve seat is preferably an annular ridge which defines an outlet from 
the valve. Alternatively, the valve arrangement could be a flat valve. 
However, in the context of the systems described, it is desirable to 
achieve an optimum flow rate of gas in a very short space of time (a 
matter of milliseconds). Thus, the obstruction presented by a flat valve 
may be unsuited to some situations. 
The pressure regulating valve and the pressure relief valve may be combined 
into a single assembly. In this regard, a suitable combination of a 
pressure regulating valve and a downstream relief valve comprises a valve 
body defining an inlet port communicating with an inlet chamber upstream 
of a regulating valve assembly which includes a valve member and an 
associated valve seat, an outlet port communicating with an outlet chamber 
downstream of the valve assembly, the combination further including a 
regulating mechanism having a movable member responsive to changes in 
pressure at the outlet port for actuating the valve assembly to regulate 
the outlet pressure, and a relief valve associated with a regulating 
mechanism and communicating with the outlet chamber, which relief valve is 
actuable, by movement of the movable member of the regulating mechanism, 
to open when the pressure at the outlet exceeds a predetermined magnitude. 
Preferably, the valve assembly comprises a valve seat, defining a passage 
between the inlet and outlet chambers, and a valve member arranged to 
close by engaging the valve seat by its movement in the direction of fluid 
flow to the outlet chamber, the valve member having a projecting nose 
extending through the aperture which is operably connected with the 
regulating mechanism. The valve member is preferably biased to the closed 
position, for example, by a spring. Alternatively, or additionally the 
said valve member may have a hollow axially projecting piston extending in 
a direction opposite to that of the nose defining, with a surrounding 
cylinder, a chamber exposed to the regulated outlet pressure to bias the 
valve member into the closed position. 
The regulating mechanism may be a piston and cylinder device communicating 
with the outlet chamber in which the piston is biased to maintain the 
regulating valve assembly open. Alternatively, the regulating mechanism 
could be a diaphragm arrangement or any other suitable assembly by which a 
change in pressure is transduced into movement of an element. 
The relief valve is effectively slaved to the regulating valve according to 
the invention. In one desirable form, the relief valve is mounted for 
movement with the movable member. The relief valve may also include a 
projection which is fixed relative to the valve body and is arranged to 
open the valve by engagement with a component thereof when the pressure at 
the outlet exceeds the predetermined magnitude. Desirably, the spacing 
between the projection and the said component for a given outlet pressure 
is adjustable. 
Preferably, the relief valve comprises a relief valve member and a relief 
valve seat, one of which is operably connected with the movable member of 
the pressure responsive mechanism for movement relative to the projection 
and engagement thereby to open the relief valve. 
When the regulating mechanism comprises a piston and cylinder device, it 
preferably includes a hollow shaft extending away from the device to which 
is mounted the relief valve which is in communication with the outlet 
chamber by means of the hollow shaft. In this form the piston of the 
device is biassed by means of a helical spring acting between a collar 
formed on the said piston and a surface fixed relative to the valve body. 
The collar also usefully defines the limit of movement in one direction of 
the piston in the cylinder of the device. 
If it is desired to be able to release more than one load, a manifold could 
be provided to supply pressure on the downstream side of the pressure 
regulating valve to a plurality of control valves, each arranged to 
control actuation of its own release or ejection mechanism. In this way, 
the vessel, the pressure regulating and the pressure relief valves can be 
common to a plurality of different pathways and thus to a plurality of 
ejection mechanisms. 
Means may also be provided on the high pressure (unregulated) side of the 
pressure regulating valve for charging the pressure vessel, and for 
determining the pressure on the high pressure side. There may also be 
pressure relief means on the high pressure, or upstream, side of the 
pressure regulating valve, for instance a burst disc or a further pressure 
relief valve, and a vent valve on the downstream side of the regulator. 
Thus, both the upstream and downstream sides can be depressurised. 
The invention also extends to a control valve per se and to a combined 
pressure regulating and relief valve per se.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The ejection system of the illustrated embodiment comprises a pressure 
vessel 10 arranged to discharge via an outlet line 12 to a pressure 
regulating and relief valve 14 and thus to a manifold 16 supplying a 
plurality of ejection and release units 18, only one of which is shown. 
Gas entering each ejection release unit 18 via a line 20 passes to a 
solenoid actuated control valve 22 and then to one side of an ejection 
piston 24. Each of these components will now be described in greater 
detail. 
The pressure vessel 10 is a standard two-part steel forged vessel suitable 
for pressures in the region of 3000 psi. A charging valve 26 in the outlet 
line 12 enables the vessel to be recharged as necessary. The stored 
pressure is indicated on a pressure gauge 28, preferably of the Bourdon 
type, and over-pressure protection on the high pressure side of the 
pressure regulating and relief valve 14 is provided by a burst disc 30. 
The disc 30 is arranged to rupture at a pressure greater than the design 
pressure of the system, but lower than the pressure the system is designed 
to be capable of withstanding without damage. If desired, the burst disc 
30 could be replaced with a further suitable pressure relief valve (not 
shown). 
The pressure regulating and relief valve 14 is illustrated in FIG. 2. The 
main body of the valve is made of aluminium alloy. In the regulating valve 
portion, a circular section chamber 40 communicates with a high pressure 
inlet port 42 through an air filter 44. The filter is designed to prevent 
the passage of particles having a dimension greater than about one 
thousandth of an inch. The chamber comprises a main compartment 46, the 
axial extent of which is defined at one end by an annular ledge leading to 
a narrower compartment 48, and, at the other end, by a valve seat 50 
axially aligned with the chamber 40. A poppet valve member 52 has a hollow 
shank 54, which extends through the chamber 40 and a hollow nose 56 which 
projects through an aperture defined in the valve seat component 50. The 
two bores are connected through an interjacent frusto-conical valve seat 
engaging portion 58. The larger diameter end of the valve seat engaging 
portion 58 is formed with a radially projecting collar 60. A compression 
spring 62 is located between the annular ledge and the facing surface of 
the collar 60. The valve seat 50 has a tapered valve surface with which 
the poppet valve 52 cooperates. 
The function of the compression spring is to urge the poppet valve 52 into 
engagement with the valve seat 50. This is assisted by a space on the side 
of the shank 54 opposite the valve seat engaging portion 58 which is also 
exposed to the pressure of the downstream side of the regulating valve 
through the bores in the poppet valve member. The shank is a tolerance fit 
in the narrower compartment 48 so that it acts as a piston in the cylinder 
of that compartment such that an increase in downstream pressure tends to 
assist in urging the valve to a closed position. The main operating 
surface upon which the regulated pressure acts is defined by a hollow 
shaft 64 sealingly engaged within a bore 66 by means of a seal ring 68. 
The shaft has a radiused nose 70 which is engaged by the end of the nose 
56 projecting through the valve seat component 50. 
Beyond the seal ring 68 the shaft has a radially projecting flange 72 which 
engages a ledge formed by an axial end surface of an insert 74 in the 
valve body, in which insert the seal 68 is located and through which the 
shaft 64 extends. The insert also defines an outlet port 76 for the gas at 
the regulated outlet pressure. 
The length of the hollow shaft 64 below the collar 72 depends from the 
collar 72 within a chamber 77. The hollow shaft 64 has a pressure relief 
valve 78 venting into the chamber 77. A square section helical compression 
spring 80 extends between the collar 72 and a base 82 of the chamber. On 
assembly the base is screwed into the valve body. A roller thrust bearing 
race 83 is interposed between the spring 80 and the base 82 to minimise 
distortion of the spring which would influence the force it exerted by the 
tendency of the spring to be rotated as the base 82 is screwed into 
position. 
The relief valve 78 has a needle valve member 84, having a conical end 
face, and a valve compartment 86 defining an aperture in which the conical 
end face is urged to sit to engage the corner of the surrounding wall of 
the compartment 86 by means of a compression spring 88. The compartment is 
in communication with the hollow centre of the shaft 64. An adjustable 
relief pin 90 is mounted in the base projecting up towards the aperture of 
the compartment 86. 
The pressure at the inlet port 42 is applied to the area of the hollow 
shaft 64, sealed against atmosphere by the relief valve 78, on the inlet 
port side of the seal ring 68. An increase in pressure at the inlet port 
42 will cause compression of the spring 80 and movement of the shaft 64 
away from the inlet port 42. The movement of the shaft allows the valve 
member 52 to move towards its valve seat 50 until the pressure at the 
outlet port 76 is eventually isolated from the inlet when the valve is 
seated. In this way, the pressure at the outlet port 76 is regulated by 
the regulator valve. 
The pressure at the outlet port 76 is communicated to the area surrounding 
the hollow nose 56 of the hollow shaft 64. As the pressure at the outlet 
port 76 rises, the hollow shaft 64 continues to move away from the outlet 
port 76. 
In the event that the pressure at the outlet port 76 exceeds a 
predetermined acceptable upper limit, the shaft 64 will be moved so far as 
to cause engagement between the conical end of the relief valve member 84 
and the stationary pin 90. Contact between the pin 90 and the valve member 
84 causes the valve member 84 to move away from the compartment 86. This 
allows the gas in the outlet port to vent to atmosphere through the relief 
valve. As one of ordinary skill in the art will appreciate, a gap between 
the lower end of the shaft 64 and the surrounding bush provides fluid 
communication to the chamber 77. The portion of the valve body defining 
the chamber 77 is vented to atmosphere by a passage 92 in the body. After 
the relief valve has opened, the pressure in the outlet port 76 will drop 
and allow the shaft 64 to move and the relief valve to reseat itself. 
The movement of the valve member is under the influence of the light spring 
62. To assist its movement towards the valve seat component, the pressure 
at the inlet port is communicated to the chamber 48 above the shank 54 as 
has been stated above, the shank 54 is a close tolerance fit within its 
bore and acts as a piston in a cylinder to the inlet pressure, assisting 
movement of the valve member towards its seat when the shaft moves towards 
the relief valve. 
To prevent gradual leakage from the high pressure to the low pressure side 
of the pressure regulating valve, the pressure regulating valve seat is of 
resilient or compliant material such as a polyimide such as Vespel (Trade 
Mark). This material is resilient enough to effect a good seal and yet 
rigid and stable enough to resist creep. The presence of creep will alter 
the valve opening characteristics and thus distort the operating 
pressures. This could affect the valve's performance adversely. 
Rather than making use of a combined pressure regulating and relief valve 
14, it would be possible to separate the two valves. Of course, in either 
arrangement the pressure relief valve will always be on the low pressure 
(regulated) side of the pressure regulating valve. 
FIG. 3 illustrates the body for the solenoid actuated control valve 22. 
When the solenoid actuator is energised, it supplies gas to the control 
valve 22 to actuate the ejection mechanism 24. 
Dealing firstly with the function of the solenoid valve shown in FIG. 4: an 
outer yoke 100 is mounted on an aluminium alloy base 102. An annular 
solenoid winding sleeve 104 is held in the yoke 100 surrounding fixed and 
moving circular section poles 106 and 108, respectively. The fixed pole 
106 is screwed into an aperture in the end face of the yoke 100. The 
moving pole 108 is constrained to axial movement by a thin sleeve 109 
between the pole and the winding sleeve 104. The poles are formed with 
opposed axial recesses 110 and 112. A helical compression spring 114 is 
mounted in the recesses to urge the poles apart. The recess 110 in the 
fixed pole 106 communicates with atmosphere through a narrow passage 116. 
A seat 118 for a vent needle valve 120 is located in the base of the 
recess 110 against which the spring 114 is braced. 
The needle valve 120 has a conical end which is axially movable to engage 
the valve seat. The stem of the needle valve extends past the fixed pole 
106 into the recess 112 in the moving pole 108. The end 126 of the stem is 
enlarged to position the stem axially in the recesses. The enlarged 
portion also acts as a surface on which the spring 114 bears. A screw 128 
is received in a threaded passage in the end of the moving pole 108 
adjacent the base of the recess 112. 
The end of the adjustment screw projects into a gallery 130 and abuts the 
blunt end of a pilot needle valve 132. The conical end of the pilot needle 
valve is mounted in a pilot valve seat 134 which also defines a guide 
sleeve for the needle valve having channels (not shown) along its axial 
length for the passage of gas. 
Gas at the controlled pressure is prevented from passing the normally 
closed needle valve 132 by its engagement with the pilot valve seat 134. 
In this de-energised state the poles 106 and 108 are spaced apart by the 
spring 114 a distance of about 1 mm allowing the gallery and the outlet 
from the pilot valve to be exposed to atmospheric pressure through the 
unseated vent needle valve 120. When an energising current is applied to 
the solenoid winding 104, the moving pole 108 is brought towards the fixed 
pole 110 until the vent valve 120 seals shut. The distance moved is around 
0.7 mm. This movement also allows the pilot needle valve 132 to be moved 
away from its seat 134 to allow gas to pressurise the interior of the 
solenoid yoke and an outlet (not shown) for actuation of the ejection 
mechanism, as will be described below. 
In the energised state of the solenoid, pressure at the outlet is applied, 
via a conduit 148 (see FIG. 5) to the auxiliary valve. This valve is 
located in another part of the body of the valve 22. It comprises a piston 
and valve assembly 150 which is mounted in a bore in the body. The 
assembly is shown in more detail in FIG. 6. The piston 152 rides in a 
first cylindrical portion 154 of the bore. A valve seat 156 of the 
assembly is mounted in a wider section of the bore adjacent the cylinder 
portion 154. 
The piston 152 itself is connected to a valve member 160 by means of an 
integral connecting rod 162. The rod 162 projects through a central 
aperture within the valve seat 156 and defines a set of three angularly 
spaced spacing members 164 which maintain the axial position of the valve 
160 relative to its valve seat 156. The region of contact on the valve 
member is defined by an annular insert 166 of a resilient material called 
Peek which faces the piston. The insert is arranged to engage an annular 
ridge 168 on the valve seat. 
Downstream of the valve seat 156 is an outlet port 170 which is in 
communication with the ejection mechanism 24. A main inlet conduit 172 is 
formed in the body by which the regulated pressure gas is applied to the 
piston skirt side of the piston 150. Thus, the regulated pressure forces 
the piston 152 away from the valve seat maintaining the valve seat 156 and 
the valve member 160 in sealing engagement. The net sealing force is the 
pressure multiplied by the difference in area between the piston 152 and 
the sealing surface defined by the annular ridge 168. When the solenoid is 
energised to allow an actuating charge of gas past the pilot needle valve 
132 and through its outlet port, it is fed via the conduit 148 to the 
chamber defined by the cylinder walls and the head of the piston 152. This 
pressure counteracts that acting on the other side of the piston so that 
the net force on the auxiliary valve is that acting on the valve member 
160 causing it to open and allow actuating air past the valve member to 
the ejection mechanism 24. 
The outlet pressure from the control valve 22 is supplied directly to the 
end surface of the ejection piston 24. Once the solenoid valve has been 
actuated and the piston 24 extended, the solenoid valve can then be 
deenergised and the piston returned to its closed position. The galleries 
in the valve are then communicated with the opened vent valve. To enable 
the piston 24 then to be moved back into its retracted position, as shown 
in FIG. 1, a leakage valve or vent (not shown) may be provided in the 
outlet 148 (see FIG. 1). 
The operation of the system will now be described with reference to its use 
in ejecting a load from an aircraft. Before the aircraft takes off, the 
load is positioned ready for ejection with the ejection piston 24 in the 
retracted position shown in FIG. 1. The vessel 10 is charged with clean 
dry gas, for example air, to a pressure of perhaps 3000 psi. After passing 
through the pressure regulating valve 14, this pressure is reduced to 
perhaps 1600 psi at 20.degree.. In common with most pressure regulating 
valves, however, there will be a tendency for the valve 14 to continue to 
pass gas at a very low rate even once the pressure on the downstream side 
has reached the nominal value of 1100 psi. Consequently, there will be a 
tendency for the downstream pressure gradually to creep upwards. 
Continually creeping downstream pressure is, however, prevented by means 
of the resilient seat on the pressure regulating valve, which ensures that 
the valve will `lock-up` (i.e. entirely cease to pass gas) at a pressure 
only slightly above the nominal regulated pressure. The lock-up pressure 
might be, for example, 1700 psi. 
The ejection mechanism is designed so that a desired ejection velocity of 
the load will be achieved by applying this lock-up pressure (1700 psi) to 
the ejection piston 24. Thus, when it is desired, in flight, to release 
the load the pilot actuates the solenoid valve 22 thereby applying the 
desired ejection pressure to the piston. 
In a typical aircraft environment there may however be very substantial 
changes in ambient temperature, for example from -60.degree. to 
+100.degree. C. While changes in the ambient temperature will considerably 
affect the pressure on the high pressure side of the gas regulating valve 
14, there will be much less impact on the low pressure side. Falling 
temperatures, and thus a tendency for the pressure on the low pressure 
side to fall, will be countered by more gas passing through the regulating 
valve 14; rising temperatures and a tendency for the pressure to rise will 
be countered by a release of gas to the atmosphere via the pressure relief 
valve. Thus, the pressure available for actuating the piston 24 can be 
maintained substantially constant, or at least maintained within given 
limits, regardless of external temperature or supply pressure changes.