DEVICE FOR DIRECTING THE FLOW OF AIR WITHIN A PNEUMATIC SYSTEM

Abstract: An aircraft pneumatic de-icing system distributor valve for controlling the inflation and deflation of pneumatic de-icer boots. Two independent pistons (13) are configured with opposing faces and arranged to move along the same axis causing their respective annulus of holes to become covered from or exposed to a pneumatic supply and thus directing air from a concentric inlet manifold (7) to one or more concentric outlet manifolds (10). A dual jet pump assembly (8) is attached to the valve body and configured so as to receive air from the inlet manifold and evacuate air from the outlet manifolds.

Description: DESCRIPTION Title : Device for Directing the Flow of Air within a Pneumatic System. Technical Field This invention relates to a pneumatic distributor valve used to control the inflation and deflation of the de-icer boots within an aircraft pneumatic de-icing system. It is a requirement for most modern aircraft to operate in adverse weather conditions. Supercooled water droplets may exist in clouds at ambient temperatures far below freezing point. When the droplets are disturbed by an aircraft flying through them, the droplets will impinge and may freeze upon the aerofoil surfaces. Ice accretions on the aerofoils can affect flight safety by increasing drag and weight and thus adversely affecting stability. Some means therefore must be provided to prevent large ice build-ups on critical areas. Various methods have been developed for ice protection of aerofoil surfaces. Fluid systems have been used, this method uses glycol or alcohol pumped in a thin film over the surface to be protected ,thus lowering the freezing point and either preventing the formation of ice ( anti-icing ) or removing ice which has already accreted ( de-icing ). Another method is Thermal Ice Protection ( anti-icing or de-icing ). Either hot air or electrical systems are available . Hot Air , using either heated ram air or compressor bleed air, passing through passages integral with the surfaces requiring protection .Electrical Resistance Heating , using elements embedded below the surfaces to be protected. One other method is Aircraft Pneumatic De-icing . This is a method of airframe de-icing which utilizes inflatable pneumatic de-icer boots which are stuck to the leading edge surfaces of the aerofoils which require protection. When inflated they break the bond between the ice and the surface, thus allowing aerodynamic forces to blow the ice away. Background Art Existing aircraft pneumatic de-icing systems have directional flow control valves with one inlet port and either one or two outlet ports. The type of valves which have one outlet port are commonly termed Ejector Flow Control Valves ( EFCV ) . The type of valves which have two outlet ports are commonly termed Distributor Valves. Existing Ejector Flow Valves are solenoid actuated ' shuttle valve ' designs. Existing Distributor Valves are ' solenoid pilot ' operated ' poppet valve ' designs. The existing distributor valve designs have many disadvantages when compared to the design of a distributor valve device of this invention. The main disadvantages of existing distributor valve designs are as follows ; They are heavy and are of a design which limits the locations and the attitude in which they can be installed on the airframe. These valves are also prone to malfunction due to the freezing of airborne moisture in their numerous small internal air channels. They have many component parts and are expensive to manufacture and assemble. They do not have non-return valve capabilities and are limited to being installed in a conventional de-icing system layout. These valves have high pressure drop characteristics and require an accurately regulated low pressure pneumatic supply to operate. The combination of the last two disadvantages results in these valves having poor operational performance, that is, giving slow inflation and deflation rates of the de-icer boots. Disclosure of the Invention One of the essential features of a distributor valve device of this invention is that unlike the existing Distributor Valve designs which are "poppet" type valves, a distributor valve device of the invention utilizes a "piston" or "plug" type mechanism. Use of this piston ( plug ) type operating mechanism has permitted distinct design improvements to be made when compared to the conventional poppet type distributor valves. These design improvements are described in the following text. This piston type operating mechanism allows the distributor valve device of the invention , to be capable of operating with much higher pneumatic supply pressures than those with which existing directional flow control valve operating mechanisms are capable of operating. The piston mechanism permits an axial valve design layout to be implemented. This gives the advantages of a symmetrical, concentric and compact valve design , allowing an annulus of holes in the cylinder through which air can be discharged when the valve is energized. Using an annulus of holes allows a large discharge area to be achieved with relatively little piston movement. This in turn results in the valve having a low pressure loss characteristic and fast response time when energized , hence improving the overall operational performance of the valve. The piston mechanism also allows the distributor valve device of the invention to be easily adapted to operate with ' non-return valve ' capabilities. The advantage of this is that two or more outlet ports from one or more distributor valves can be connected within the pneumatic airframe de-icing system , so as to allow the simultaneous supply of pneumatic pressure to the same de-icer boot or the same circuit of de-icer boots. Thus the rate at which air is supplied to inflate and deflate the de-icer boots is increased and the system reliability is improved by having more than one supply source. The concentric design allows the valve body to be cylindrical and more suitable to withstanding the pressure induced stresses. This in turn permits a thinner wall thickness to be used giving a substantial reduction in valve body weight. The concentric and symmetrical valve design lends itself to simple manufacturing and machining operations hence reducing production costs. The low number of valve component parts also helps to reduce the manufacturing costs. The compact design allows this valve to have a much smaller space envelope than any of the existing distributor valve designs, making it easier to install on the airframe. The valve symmetry and concentricity allows it to have good installational flexibility. Figure 9 shows how a distributor valve device of this invention can be configured with numerous inlet ports and outlet ports and also how the attachment brackets may be orientated in many different ways to suit different airframe installations. These are just some of the advantages permitted with a piston type mechanism. Others are in areas such as improved reliability, less likelihood of freezing, resilience to in-service vibrational and shock loads, ease of maintenance and repair. According to the present invention there is provided a distributor valve for directing the flow of air within a pneumatic system such as an aircraft pneumatic de-icing system, wherein the distributor valve is provided with one or two pistons configured so as to move axially, each within a cylinder, characterized in that the cylinder has an annulus of holes through which air can be discharged and means are provided for actuating the piston to move in one direction or another, covering or uncovering the annulus of holes to the pneumatic supply. Preferably the device of the invention is configured so that the pneumatic air supply can be directed from a concentric inlet manifold to one or more concentric outlet manifolds. Preferably the device of the invention can have one or more inlet or outlet ports on the inlet or outlet manifolds. The means of actuating each piston preferably comprises a pilot solenoid, configured to vent a control chamber, a control orifice in the piston face and a piston return spring. Preferably the device of the invention has an integral non-return mechanism which acts to prevent the reverse flow of air through the valve. A preferred non-return mechanism comprises an annular seal which seats in a perforated groove within each piston, configured so that when the upstream pneumatic pressure exceeds the downstream pneumatic pressure, the seal prevents air from passing through the perforations and when the downstream pneumatic pressure exceeds the upstream pneumatic pressure air is allowed to pass through the perforations. Preferably the device of the invention has a dual jet pump assembly attached to the valve body and configured so as to receive a pneumatic supply from the inlet manifold and to evacuate air from the outlet manifolds. A preferred configuration utilizes a vent block to support the dual jet pump assembly and provide the necessary channels for the pneumatic supply and the evacuation of the outlet manifolds. Preferably the vent block is provided with a means of being heated, for example , by using electrical resistance heater elements embedded within the vent block body. This will prevent the freezing of moisture within the vent channels, the adjacent valve body and the dual jet pump assembly. Preferably the device of the invention is configured with a relief valve mechanism located at one or more of the outlet ports. The preferred outlet port relief valve mechanism will operate at a pre-determined pressure setting, to prevent an excessive pneumatic pressure in the downstream de-icer boot or circuits of de-icer boots. The preferred outlet port relief valve will have an integral electrical switch mechanism, configured so as to open or close the switch contacts when the relief valve mechanism actuates. Preferably the electrical switch mechanism is included as part of the electrical power supply circuit for the related pilot solenoid and configured so that when the relief valve actuates the electrical power supply is switched off from the pilot solenoid. Preferably a pneumatic airframe de-icing system fitted with one or more devices of the invention may be configured so that two or more outlet ports can simultaneously supply pneumatic pressure to the same de-icer boot or circuits of de-icer boots. Preferably a pneumatic airframe de-icing system fitted with one or more devices of the invention will be able to operate from an unregulated pneumatic supply, or from a pneumatic supply with a wide or varying regulation band. Preferably a pneumatic airframe de-icing system fitted with one or more devices of the invention may operate from a pneumatic supply which exceeds the normal working pressure of the de-icer boots which are being supplied. This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a standard distributor valve device of the invention, configured with one inlet port and two outlet ports. Figure 2 shows a schematic diagram of the operating mechanism of a distributor valve device of the invention, in the de-energized condition. Figure 3 shows a schematic diagram of the operating mechanism of a distributor valve device of the invention, in the energized condition. Figure 4 shows a distributor valve configured with outlet port relief switches. Figure 5 shows a typical wiring diagram applicable to a standard distributor valve configuration. Figure 6 shows a wiring diagram applicable to a distributor valve device of the invention configured with outlet port relief switches. Figure 7 shows a schematic block diagram of a conventional ( existing ) type pneumatic airframe de-icing system fitted with conventional ( existing ) type distributor valves. Figure 8 shows a schematic block diagram of a pneumatic airframe de-icing system fitted with distributor valve devices of the invention. Figure 9 shows a distributor valve configured with one inlet port and four outlet ports. Referring to the accompanying drawings, Figures 2 and 3 show schematic diagrams of the piston type operating mechanism , of the distributor valve devices of the invention. Figure 2 shows this mechanism in the de-energized condition and Figure 3 in the energized condition. Due to valve symmetry the valve has been drawn energized port 'A' only, energized port 'B' being a mirror image and operating by the same principle. A distributor valve device of the invention has a cylindrical outer body ( 1 ) with vented end caps ( 2 ) between the caps and the body are supported the attachment brackets ( 3) . The standard distributor valve configuration has one inlet port ( 4 ) and two outlet ports, Port 'A' ( 5 ) and port 'B' ( 6 ). In the de-energized state, pressure regulated air passes through the inlet port and into the inlet manifold ( 7 ) . From the inlet manifold air is fed to the dual jet pump assembly ( 8 ), via the hollow connecting rod ( 9 ) . The throats of the dual jet pump assembly are connected to the outlet manifolds ( 10 ) via the secondary flow channels ( 11 ). Air is also fed from the inlet manifold through the control orifices ( 12 ), which are located in the faces of the 'A' and 'B' pistons ( 13 ), and then into the 'A' and 'B' piston control chambers ( 14 ). The piston control chambers are bounded by the pilot solenoids 'A' ( 15 ) and 'B' ( 16 ), the cylinders ( 17 ), the pistons ( 13 ) and the piston seals ( 18 ). The piston seals ensure that there is no leakage of air from the inlet manifold or the piston control chambers to the outlet manifolds via the annulus of discharge holes ( 19 ) located in the cylinders. The return springs ( 20 ) are in compression and exert a force on the piston in the closing direction. Supporting the dual jet pump assembly and providing the secondary flow channels is the vent block ( 21 ) which may have an integral cartridge type heater element to help prevent valve freezing. In the event that the pilot solenoid 'A' is energized, the control chamber air is vented to ambient via the vent chamber ( 22 ) and the vented end cap ( 2 ). This reduces the control chamber air pressure in relation to the inlet manifold pressure. The resulting imbalance of forces across the piston face causes the piston to travel into the control cylinder, when this occurs the piston compresses the spring and uncovers the annulus of discharge holes in the cylinder. Pressure regulated air can then enter the outlet manifold to discharge through port 'A'. When pilot solenoid 'A' is de-energized it seals the control cylinder from venting to the ambient. In this condition the air pressure in the control cylinder increases. The resultant effect of the larger piston area and the compressed spring, is a force which causes the piston to travel towards the inlet manifold. In so doing it closes off the annulus of discharge holes. This prevents any more pressure regulated air from entering the outlet manifold. Meanwhile the constant running jet pump evacuates the residual air in the outlet manifold and the de-icer circuit connected downstream of port 'A'. Depending upon the configuration of the de-icing system, it may be necessary for the distributor valve to function as a non-return valve and prevent any possible flow of air in the reverse direction, that is from the outlet manifold to the inlet manifold. In order to achieve this the pistons ( 13 ) must be adapted with non-return seals ( 23 ) which are seated in perforated grooves ( 24 ) which are integral to the pistons. In the event that the pressure in the inlet manifold exceeds the pressure in the outlet manifold, the control chamber pressure will be greater than the outlet manifold pressure. This will cause the non-return seal ( 23 ) to be forced into the groove ( 24 ), thus sealing off the perforations and maintaining the piston in the closed position. In the event that the pressure in the outlet manifold exceeds the pressure in the inlet manifold, the control chamber pressure will initially be less than the outlet manifold pressure. This will cause the seal to uncover the perforations in the seal groove and allow air to pass into the control chamber, thus increasing its pressure with respect to the inlet manifold pressure. This increased differential pressure will maintain the piston in the closed position. Under these conditions the distributor valve device of the invention will be acting as a non-return valve. Figure 4 shows a sketch of the distributor valve device of the invention fitted with outlet port pressure relief switches ( 25 ). A pressure relief switch is a pressure relief valve, with an integral electrical switch mechanism. These are configured so that the switch contacts open or close when the relief valve mechanism activates. A distributor valve device of the invention configured with outlet port pressure relief switches allows the system pressure to be relieved between the distributor valve and the de-icer boots. This gives the advantage that in addition to being able to operate from a conventional low pressure regulated pneumatic supply, it can also be successfully operated from an unregulated pneumatic supply, a pneumatic supply with a wide regulation tolerance band or from a high pressure regulated pneumatic supply, for example. A distributor valve device of the invention so configured, will ensure that under all supply pressure conditions, the rubber de-icer boots do not exceed their safe working pressure. Additionally a distributor valve device of the invention configured with outlet port pressure relief switches, may be adapted so that the electrical switch mechanisms are included as part of the electrical power supply circuit for the related pilot solenoid. For example, outlet port pressure relief switch 'A' and pilot solenoid 'A' may be electrically connected, so that when the relief valve mechanism actuates, the electrical power supply is switched off from that pilot solenoid. This will cause the piston in the distributor valve to close and the de-icer boot will begin to deflate. As the system pressure falls, the relief valve will return to the closed position, the switch contacts will close and power will again be restored to the pilot solenoid. With power restored to the pilot solenoid the piston in the distributor valve will open and the above cycle of events will be repeated. A distributor valve device of the invention configured with outlet port pressure relief switches can be adapted to cycle in the above manner, either for the entire duty cycle of the related pilot solenoid, or once per pilot solenoid duty cycle. The advantages of this type of electrical circuit configuration are as follows. It can improve the de-icing performance of the system by automatically causing cyclic pressure pulsations within the pneumatic de-icer boot or de-icer boot circuits. These pressure pulsations will assist in breaking the bond between the ice and the de-icer boot surface. It minimizes the amount of pneumatic supply air which is relieved to the ambient environment. It provides an additional safety feature which will prevent that part of the distributor valve from being operated in the event that the relief valve mechanism fails in the open position. Operating from higher feed pressures results in much faster de-icer boot inflation and deflation rates, leading to improved de-icing performance. Operation at these higher system pressures also allows smaller bore supply pipes to be used, reducing the overall system weight and facilitating system installation. Higher feed pressures also gives improved jet pump performance. Whether a distributor valve device of this invention is configured with or without outlet port relief switches it will require an electrical receptacle device (26) with which to interface with the aircraft's electrical system. The system configuration shown in figure 8 offers the following advantages over that shown in figure 7. There will be improved operational performance resulting in faster de-icer boot inflation and deflation rates. There will be a reduction in the overall system cost and weight resulting from the reduction in the number of components required in the system. There will also be an improvement in the system redundancy and reliability because of the increased number of pneumatic supply sources feeding each de-icer boot circuit. With reference to figures 7 and 8, there are pneumatic sources (27), pressure regulating valves (28), pressure relief valves (29), check valves (30), water separators (31), pressure switches (32), wing de-icer boots (33), tailplane de-icer boots (34), existing type distributor valves (35) and a distributor valve devices of the invention (36). Figure 9 shows how the design of the distributor valve device of the invention can be adapted to have numerous inlet and outlet ports, and how the attachment brackets can be positioned in any radial orientation to facilitate the unit's installation to the airframe.

Claims: CLAIMS 1. An aircraft pneumatic de-icing system distributor valve for directing the flow of air within an aircraft pneumatic de-icing system, wherein the valve is provided with two independent pistons arranged so as to move along the same axis either within the same cylinder or within separate cylinders. The pistons being configured with opposing faces and having a respective annulus of holes in the cylinder wall through which air can be discharged and the means provided to independently actuate the pistons to move in one direction or another causing the respective annulus of holes to become covered from or exposed to a pneumatic supply. 2. An aircraft pneumatic de-icing system distributor valve as claimed in claim 1 wherein the means provided to actuate each piston comprises a pilot solenoid configured to vent a control chamber, a control orifice in the piston face and a piston return spring. 3. An aircraft pneumatic de-icing system distributor valve as claimed in claim 1 wherein the pneumatic supply can be directed from a concentric inlet manifold to one or more concentric outlet manifolds. 4. An aircraft pneumatic de-icing system distributor valve as claimed in claim 3 wherein the inlet or outlet manifolds can have one or more inlet or outlet ports. 5. An aircraft pneumatic de-icing system distributor valve as claimed in claim 1 wherein there is an integral non-return mechanism which acts to prevent the reverse flow of air through the valve. 6. An aircraft pneumatic de-icing system distributor valve as claimed in claim 5 wherein the non-return mechanism comprises an annular seal which seats in a perforated groove within each piston, configured so that when the upstream pneumatic pressure exceeds the downstream pneumatic pressure the seal prevents air from passing through the perforations and when the downstream pneumatic pressure exceeds the upstream pneumatic pressure air is allowed to pass through the perforations. 7. An aircraft pneumatic de-icing system distributor valve as claimed in claim 3 wherein a dual jet pump assembly is attached to the valve body and configured so as to receive a pneumatic supply from the inlet manifold and to evacuate air from the outlet manifolds. 8. An aircraft pneumatic de-icing system distributor valve as claimed in claim 7 wherein a vent block is used to support the dual jet pump assembly and provide the necessary channels for the pneumatic supply and the evacuation of air from the outlet manifolds. 9. An aircraft pneumatic de-icing system distributor valve as claimed in claim 8 wherein the vent block can be heated to prevent the freezing of moisture within the vent channels, the adjacent valve body and the dual jet pump assembly. 10. An aircraft pneumatic de-icing system distributor valve as claimed in claim 9 wherein the method of heating the vent block is achieved using electrical resistance heater elements embedded within the vent block structure. 11. An aircraft pneumatic de-icing system configured with one or more aircraft pneumatic de-icing system distributor valves as claimed in claim 5 wherein two or more distributor valve outlet ports can be connected so as to allow the simultaneous supply of pneumatic pressure to the same inflatable de-icer boot or circuit of inflatable de-icer boots. 12. An aircraft pneumatic de-icing system distributor valve as claimed in claim 4 wherein one or more of the outlet ports are each configured with a relief valve mechanism which operates at a predetermined pressure setting, to prevent an excessive pneumatic pressure in the downstream de-icer boot or circuits of de-icer boots. 13. An aircraft pneumatic de-icing system distributor valve as claimed in claim 12 wherein one or more of the outlet port relief valve mechanisms have an integral electrical switch mechanism, configured so as to open or close the switch contacts when the relief valve mechanism activates. 14. An aircraft pneumatic de-icing system distributor valve as claimed in claim 13 wherein the electrical switch mechanism is included as part of the electrical power supply circuit for the related pilot solenoid and configured so that when the relief valve actuates the electrical power supply is switched off from that pilot solenoid. 15. An aircraft pneumatic de-icing system configured with a distributor valve as claimed in claim 12 wherein the pneumatic supply to the valve does not need to be pressure regulated or may be pressure regulated within a wide regulation tolerance band. 16. An aircraft pneumatic de-icing system configured with a distributor valve as claimed in claim 12 wherein the pneumatic supply pressure to the distributor valve in normal operation can exceed the normal working pressure of the de-icer boots which are supplied by that distributor valve.

Inventors: BOLAM ROBERT CAMERON, BOLAM, ROBERT, CAMERON
Applicants: BOLAM ROBERT CAMERON, BOLAM, ROBERT, CAMERON
Application year: 1998
Main classification: B64D15
IPC codes: B64D15