US2851054A

US2851054A - Flutter valves

Info

Publication number: US2851054A
Application number: US624611A
Authority: US
Inventors: Lawrence F Campbell; Ralph C Taylor
Original assignee: Individual
Current assignee: Individual
Priority date: 1945-10-25
Filing date: 1945-10-25
Publication date: 1958-09-09
Anticipated expiration: 1975-09-09

Description

P 9, 1958 L. F.-CAMPBELL ETAL 2,851,054

FLUTTER VALVES Filed Oct. 25, 1945 WW W tat

FLUTTER VALVES Lawrence F. Campbell, Silver Spring, Md., and Ralph C. Taylor, Washington, D. C.

This invention relates to valves, and more particularly to flutter valves for gas pulsator type motors.

Essentially, a gas pulsator motor is atubular structure comprising an air scoop at the leading end, a valve system associated with the air scoop for controlling the flow of air, a combustion chamber to the rear of the valve system and a discharge tail pipe or resonating duct. As the name implies, the jet is intermittent in character and the operation of the whole unit is cyclical instead of continuous.

' The pressure for the acceleration of the exhaust gases is the result of several superimposed phenomena. A small amount of ram compression is obtained due to the forward flight velocity and an additional pressure rise is obtained as a result of the pressure wave due to the resonance of the tail pipe, but the major portion of the compression is the result of the rapid combustion of the fuel. This rapid combustion increases the temperature of the gases within the combustion chamber which results in a'rapid rise in pressure. The rate of combustion must be rapid, otherwise the increased temperature will result in a slow flow of gases through the tail pipe without developing any significant thrust. The valve system enables a high pressure to be generated by the combustion and causes the thrust thereof to be delivered rearwardly.

In one type of gas pulsator type motor, in order to direct the thrust from the motor, a valve system comprising a large member of resilient vanes is mounted at the forward end of the motor and when an explosion occurs, the vanes are forced into closed position thus causing the force of the explosion to be exerted out the opposite or rear end of the motor. Thereafter the pressure of the air against the outer sides of valves, or flutter valves as they are often termed, resulting from the forward motion of the motor, causes the flutter valves to open and to admit air into the firing chamber. The explosions occur very rapidly, being in some cases on the order of fifty explosions per second, and consequently the flutter valves must respond rapidly to changes in the direction of the pressure. For this reason thin, metal vanes are employed which are made of a resilient material and are fixed along their leading edge to a suitable support. Normally, the trailing edges of the vanes flare outwardly slightly so that when an explosion occurs, they will be forced further outward and caused to close the entrance orifice of the tube.

In practice it has been found that the considerable heat applied to the valves by the combustion of the fuel and the rapidity and force of the explosions cause a rapid deterioration of the metal vanes. Thus, heretofore, the useful life of the flutter valves has been extremely short.

An object of the present invention is to provide a new and improved valve for gas pulsator type motors.

A further object of the present invention is to provide a protective covering for the vanes of the flutter valves used with the gas pulsator type motor to increase the useful life of the valves.

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In accordance with one embodiment of this invention the vanes of the flutter valve are encased in a sheath of thin, flexible material having suitable characteristics to protect the metal vanes against impact, shock, and vibration and against the heat of combustion;

Other objects and advantages of the present invention will be apparent from the following drawing, wherein:

Fig. 1 is a side, elevational view of a flutter valve provided with a protective covering in accordance with this invention; and,

Fig. 2 is a vertical sectional view taken substantially along the line 2-2 of Fig. 1. 1

Referring now to the drawings it will be seen that a long, rectangular, metal plate 5 is there shown having apertures 6 formed through the midportion of either end thereof for mounting the plate in the gas pulsator motor. In the motor the vane supporting plate would be mounted with the upper edge thereof serving as the leading edge, and ordinarily a large number of these plates would be employed. A plurality of pairs of thin, resilient, metal vanes 7 are fixed to the upper edge of the vane supporting plate 5, as by the rivets 8 shown which extend transversely through the upper portion of the plate 5. It will be understood that any suitable means may be employed for attaching the vanes to the supporting plate and that while at the present time it seems most desirable to employ resilient vanes, pivotally supported, rigid vanes may also be employed. The lower portions of the metal vanes 7 are flared slightly outwardly and since the vanes are made of resilient material, the current of air moving downward, with respect to the position of the flutter valve as shown in these drawings, will tend to cause the vanes to be pressed against the sides of the vane supporting plate 5, thus permitting the freest possible flow of air. Upon occurrence of an explosion in the firing chamber of the motor, the gases resulting from the explosion tend to move both against the flow of air and out the opposite end of the motor. This reversal in direction of pressure initially permits the vanes to spread outwardly clue to their resilience and then, as the pressure increases, to bear against the valve supporting grid 11, thus momentarily sealing the inlet orifice of the motor and causing the force of the explosion to be exerted primarily rearwardly. The impact shock resulting from the explosion and the heat resulting from the combustion of the fuel has been found to cause deterioration of the metal vanes at such a rapid rate that the useful life of the valves heretofore has been extremely short.

In accordance with the present invention in order to extend the useful life of the flutter valve assembly, the metal vanes are encased in a sheath 9. The sheath 9 may be formed from strips cut to have a width substantially equivalent to the width of a vane and a length substantially double the length of the vane. In assembling a vane on the vane supporting plate 5, a strip of fabric is folded to encase the lower end of the vane and so that the upper edges of the strip terminate substantially along the upper edges of the vane. Where rivets are employed to attach the vane to the supporting plate, the rivets are then driven through the assembly, as clearly shown in Fig. 2.

While a strip or sheet of the sheath material is simple to apply, it is also feasible to employ a plurality of such strips disposed side by side on each vane, or to use strands instead of strips. Where a fabric material is employed, it is desirable that the majority of strands are disposed longitudinally of the strip so that minimum frictional resistance is offered to the flow of air. 1

The material of which the fabric sheet 9 is formed mus be one which in addition to being thin and flexible so that it will not substantially interfere with the operation of the valve, will be substantially impervious to the heat whichis applied to the valve during combustion and in addition will serve to insulate the vanes from. the heat of combustion. Furthermore, the sheath material must be resilient as well as flexible so that no interference with the operation of the vanes will be incurred. The material must have a satisfactory impact strength so that it will be able toresist the shocks resulting from the rapid and recurrent applications of stresses during the operation of the motor. It hasbeen found that certain materials suchas glass, or glass cloth, which may be bonded with a plastic impregnant such as a silicone or polytetrafiuorethylene, both of these impregnant' materials having satisfactory heat resistant characteristics, are suitable sheath materials. Asbestos, bentonite and various ceramic ma,- terials possesssing the aforementioned qualities may also be employed. In general, the. sheath must be made thick enough on the one hand to afford adequate heat protection and cushioning and yet not so thick as to interfere with the operation of the valve. In a particular case the optimum thickness Will depend upon the size and type 'of vane.

In use it' has been found that the protective sheaths 9 serve to cushion the shock resulting from explosion so that the impact shock applied to the vanes is greatly softened and at the same time the sheaths protect the metal vanes from the heat of combustion. The result has been that the useful life of the flutter valves is extended many times that heretofore believed possible. A further advantage resides in the sealing action of the sheaths: as the vanes are pressed against the valve sides to close the orifice, the sheaths are compressed and act like gaskets preventing escape of pressure. Since any forward escape of pressure during combustion results in the hot gases moving nearer the valve, thus increasing the temperature in the area of the valve, preventing the escape of pressure forwardly through the valve is very effective in increasing the useful life of the valves.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or scope of the present invention.

The invention shown and described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1 A flutter valve structure for pulsator type gas motors comprising a valve seat, a thin flexible metallic vane having a leading edge and a trailing edge, cushioning heat insulating means carried by said vane in the form of a flexible sheathing of bonded glass fabric folded around the trailing edge of the vane over opposite sides of the vane and extending to near the leading edge of the vane, means securing said fabric to the vane at the leading edge, said sheathing providing protection for said vane against hot exploding gases and cushioning the vane against impact of the exploding gases along the vane and against mechanical impact against said valve seat, said sheathing being compressible to form a gasket seal against said valve seat to prevent escape of pressure fluid.

2. A flutter valve structure for pulsator type gas motors comprising a valve seat, a metallic supporting plate having a leading edge and a trailing edge, a thin flexible metallic vane having a leading edge and a trailing edge, cushioning heat insulating means carried by said vane in the form of a continuous sheathing of bonded glass fabric folded around the trailing edge of the vane over opposite sides of the vane and extending to near the leading edge, means securing said vane, sheathing and supporting plate together at their leading edges, said sheathing providing protection for said vane against hot exploding gases and cushioning the vane against impact of the exploding gases along the vane and against mechanical impact against said valve seat, said-sheathing being compressible to form a gasket seal against said valve seat to prevent escape of'pres'sure fluid.

3. A flutter valve structure as claimed in claim 2 in which the heat resistant fabric is a glass cloth impregnated with polytetrafluorethylene.

References Cited in the file of this patent UNITED STATES PATENTS 952,523 Hillegass Mar. 22, 1910 1,240,848 Hiscock Sept. 25, 1 917 1,995,727 Wetherbee Mar. 26, 1935 2,161,769 Trask June 6, 1939 2,402,208 Read June 18, 1946 2,408,056 Farmer Sept. 24, 1946 2,432,213 Rutishauser Dec. 9, 1947 2,505,757 Dunbar et a1. May 2, 1950