US2713768A - Power gas generating assemblies - Google Patents

Description

July 26, 1955 2,713,768

R. LIVINGSTON ET AL POWER GAS GENERATING ASSEMBLIES Filed March 3, 1950 2 SheetEwShGe'L l Invenlora ROBERT LIVINGSTON ALEXANDER CANTLAY HUTCHISON M 4a, v

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y 1955 R. LIVINGSTON ET AL 2,

POWER GAS GENERATING ASSEMBLIES Filed March a, 1950 2 Sheets-Sheet 2 I I I I I I I I l2 7 8a a s I F164. F/GS. 2 F/66 I nventors ROBERT LIVIN GSTON ALEXANDER CANTL AY HUTCHISON I torney:

United States Patent POWER GAS GENERATING ASSEMBLIES Robert Livingston, Prestwick, and Alexander Cantlay Hutchison, Saltcoats, Scotland, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain Application March 3, 1950, Serial No. 147,412

Claims priority, application Great Britain April 14, 1949 4 Claims. (Cl. 6035.6)

The present invention relates to a new or improved power gas-generating assembly of separable construction and of the kind including a compact charge of a solid composition of the kind which when its thermal decomposition is initiated sustains said decomposition exothermically into gaseous products without detonation, independently of the surrounding atmosphere. The new or improved power gas-generating assemblies include for instance rocket propulsion assemblies or assemblies capable of delivering a stream of the power gases under pressure to a prime mover such as a reciprocating engine or turbine.

In power gas-generating units for operating mechanical devices and some forms of rocket devices it is well known for the construction to comprise a reaction chamber into which the solid gas-generating charge is introduced and in which it is enclosed by the closure of a breech member or the like, this chamber being a permanent part of the structure and, except in the case of projectiles, intended to be recharged by the insertion of another expendable charge of the solid gas-generating composition. The expendable charge thus inserted into the chamber frequently comprises in addition to the compact solid composition an associated envelope or sheath which may serve to protect it from moisture or to influence the manner in which the decomposition propagates itself, for instance by affording protection against the propagation of the decomposition over some portion of the surface of the compact composition. Usually such envelope or sheath associated with the compact gas-generating composition is of a destructible nature, and if a portion of it is of such a nature as to remain undestroyed after the composition has been consumed this is Withdrawn from the interior of the reaction chamber before the next charge is inserted.

The object of the present invention is to produce an easily assembled power gas-generating assembly by providing a non-expandable frame-work portion for gripping within it a simple expendable gas-generating portion comprising a gas-generating charge capable of generating for a few seconds of a stream of gas at a predetermined pressure, which may be of the order of at least atmospheres, when initiated in said non-expendable frame-work portion but which provides no propulsive effect if agcidentally ignited when not in said frame-work portion.

A power gas-regenerating assembly according to the present invention comprises an expendable portion within a non-expendable frame-work portion wherein said expendable portion comprises an annular solid gas-generating charge having a tubular metal envelope or sheath extending beyond said charge and open at both ends and wherein said non-expendable frame-work portion comprises in separable combination a safety disc end plate wall member, a nozzle end wall member, and spacing rod members adapted to hold said end wall members at a predetermined adjustable distance apart to grip said expendable portion longitudinally.

Preferably the said annular solid gas-generating charge 2,713,?63 Patented July 26, 1955 "ice is protected from decomposition along its longitudinal surface by a sheath of heat insulating material interposed between it and the said metal tube.

It is also preferred that ignition means for initiating the decomposition of the said annular solid gasgenerating charge should be accommodated in the metal tube. Furthermore it is also desirable that the said ignition means should be situated at the end of said expendable portion intended to face the safety disc end plate wall member of said non-expendable frame-work portion.

In the preferred form of the power gas-generating assembly it is desirable that the ends of the metal tube of the expendable portion should be parallel and accurately squared and that the said end wall members of said non-expendable frame-work portion should be grooved so as to enable gas-tight joints to be formed with the ends of the metal tube of the expendable portion.

The expendable portion in the gas-generating assembly is either clamped between the two end wall members by the spacing rod members taking the form of adjustable bolts or by having the two ends wall members kept at a fixed distance apart by fixed spacing rod members and one of the said end wall members so constructed that the portion which is to abut the expendable portion is capable of being moved towards said expendable portion by means of a threaded ring in said wall member.

The rechargeable expendable portion of the assembly may be provided for storage purposes with end caps to protect the charge of compact composition therein from moisture and from mechanical damage.

The invention is illustrated with reference to the diagrammatic drawings accompanying the specification in which Fig. 1 is an isometric view of the complete assembly partly broken to show the internal construction of the expendable portion, this assembly being suitable for use as a rocket means for assisting the propulsion of a vehicle such as a motor bicycle; Fig. 2 is a similar view of part of the permanent frame-work portion of the assembly shown in Fig. 1; Fig. 3 is a longitudinal axial section of the assembly shown in Fig. 1; Fig. 4 is a longitudinal axial section of the expendable portion of the assembly illustrated in Fig. 1 and Fig. 3; Figs. 5 and 6 are end caps for the portion illustrated in Fig. 4; Fig. 8 is a detail of a nozzle bearing member constituting part of the retention means for the expendable portion of the apparatus, and Fig. 7 is a detail of a screw-threaded member cooperating with the nozzle bearing member of Fig. 8 intended to be inserted into a threaded channel visible in Fig. 2; Fig. 9 is a view of a broken portion of a gas delivery tube member intended to be used instead of the nozzle bearing member shown in Fig. 8 when the gases from the assembly are to be used for driving a prime mover such as a reciprocating engine or turbine.

In Figs. 1, 2 and 3 of the drawings 1 is a metal end plate member axially channelled and internally shouldered having an internal screw thread in the wider portion of its bore which is situated in a projecting portion 3, as is best seen in Figs. 2 and 3. 2 is a grooved end plate member having an axial bore 5, opening out at a shoulder into a wider and partly screw-threaded axial channel as is best seen in Fig. 2 and Fig. 3. When the device is assembled a diaphragm rupturable at a predetermined internal pressure interposed between gaskets 6a and 6b resting on the said shoulder is retained by an internally member shown in Fig. 8 has been broken to reveal a a similar gasketted groove 15. 12 is the wall of a gasdefiecting hood 9 retained on the remote side of the end plate member 2 by the nuts 11. 16 are shouldered spacing rods passing through the end plate member 2 and located in the end plate member 1 and arranged so as to hold the end plates 1 and 2 accurately parallel and at a fixed distance apart. These are also retained by the nuts 11. 17 is the cylindrical metal retaining wall of the expendable portion of the charge illustrated in Fig. 4, 18 is a layer of bonded asbestos sheeting and 19 is an annular charge of a pulverulent mixture comprising a nitrate of a nitrogen base and a sensitiser of the thermal decomposition thereof compacted by compression against said layer within said cylindrical metal wall and drilled out into annular form. The heat insulating composition 18 is tightly crushed between the compacted composition and the wall 17 so that the annular charge 19 is securely located in fixed position. The ends of the cylinder 17 are accurately squared and its thickness is such that it can enter the grooves 8 and 15. A space is left between the ends of the cylinder 17 and the ends of the asbestos sheeting 18 and the annular charge of compacted composition 19 sufiicient to ensure that when the assembly is put together no part will bear lengthwise on the latter. At one extremity of the channel 17 where the annular charge 19 and its insulation 13 are further curtailed there is also accommodated a cup 20 of easily deformable material such as rnillboard whose rim abuts the end of the insulation 18, this cup containing a pellet of gunpowder 21 to the end of which is attached an electric match-head 22 from which extend the short leads 2S and 24 having terminals 25 and 26 at their ends. The end caps and 6 are of relatively thin metal plate and are an easy push fit over the ends of the metal cylinder 17.

The nozzle member as is best seen in Fig. 8 embodies a metal disc 27 having a gasketted groove to which reference has already been made and has internally threaded channel into which a venturi 14 externally threaded at its narrow end is screwed to form a tight joint with the assistance of a gasket ring 28.

In the externally threaded retaining ring 13 illustrated in Fig. 7 and also seen in Figs. 1 and 3, 29 are slots enabling this ring to be screwed into threads 4 seen in Fig. 2 after insertion of the nozzle member illustrated in Fig. 8. 27' and 27" are lugs enabling the assembly to be attached to the frame of a vehicle.

In order to assemble the device the end caps are removed from the metal cylindrical wall 17 of one of the supply of expendable portions of the assembly and this portion of the assembly is then introduced into the portion illustrated in Fig. 2 through the threaded channel in the projection 3 which is sufliciently broad to enable one end of said expendable portion to be brought up against the end plate member 2. That end of the cylinder 17 near which ignition elements 21 and 22 are situated is then fitted carefully into the gasketted slots 8, and the portions of the leading wires with their terminals 25 and 26 external to the cup are brought through a narrow channel provided in the end plate member 2 to the exterior thereof. The narrow channel is then sealed by packing not shown. The nozzle member is then inserted through the channel 4 and the gasketted groove 15 carefully fitted on to the other end of the cylinder 17. The threaded ring 13 is then screwed into place so as to bring pressure to bear on the grooved ring 27 and thus provide a gas-tight joint between the end members and the cylindrical wall of the venturi-nozzle-vented reaction chamber thereby formed. The safety bursting disc 6 is adapted to rupture at a predetermined pressure in excess of the working pressure which it is desired to maintain in the reaction chamber. When the terminals and 26 are connected to a source of electric current the match-head 22 is ignited and this ignites the gunpowder pellet 21 which in turn ignites the exposed portion of the surface of the annular charge of compacted composition 19, so that the inner cylindrical surface thereof very rapidly becomes ignited by the hot gases passing through it and the gases escape under pressure through the venturi nozzle 14 delivering a thrust in the opposite direction. For the operation of a motor bicycle it may be desirable to have one or more of these devices on each side of the rear wheel and to have the open mouth of the gas-deflecting hood directed downwardly so that should the safety disc 6 become ruptured its remains and the hot gases thereby escaping through the channel 5 will be downwardly directed; and it will be understood that when two of the devices me arranged in this way the lugs 27' and 27" will be arranged in mirror image relationship with respect to the mouth of the gas-deflecting slot. When the device is one required for starting an engine or the like the grooved and gasketted end of the gas delivery pipe is brought to bear on the end of the metal cylinder 17 in a simliar manner to that employed in the case of the nozzle member illustrated in Fig. 8. After the charge has been consumed the retaining ring 13 is unscrewed, the nozzle member 14 removed and the tube 17 is removed. The remains of the ignition system may then be withdrawn from which ever side of the end plate 2 is convenient. As will be understood the tube 17 is undamaged and may be recharged, but there will usually be provided a plurality of charged expendable portions of the assembly. As will be understood the gaskets and safety disc may require to be replaced from time to time.

The advantages of the invention include the reduction in weight of the permanent portion of the apparatus, which is especially important in connection with vehicles for which rocket propulsion is only occasionally required. There is also an overall reduction in weight in that the cylinder 17 in conjunction with the small end caps provides the only container required for each charge of gas-generating composition. It is a further advantage that the rechargeable container is not in itself of the nature of a rocket, so that any accidental ignition of the composition will merely result in the light end caps being blown 011 and will not involve a heavy article flying away. A further and very important advantage in the case of rocket devices is that it facilitates the positioning of the igniting means so that the ignition is initiated from the end remote from the nozzle, whereby the ignition over all the exposed surface of the annular compact charge of gas-generating composition is assisted by the direction of the flow of the gases. The removal of the remains of the igniting elements is also rendered very easy since the withdrawal of the tubular wall from its seating leaves them exposed and accessible.

What we claim is:

1. A power gas-generating assembly comprising an expendable charge portion including an annular solid gasgenerating charge, a sheath of heat insulating material contingent with and surrounding said charge, and a metal tube contingent with and surrounding said sheath of insulating material, said metal tube extending beyond said charge and being open at both ends, a reusable rame portion for receiving successive expendable charge portions therein, said frame portion including a first end plate wall, a second end plate wall, rod means extending betwen said end plate walls for maintaining them in spaced relation, said second end plate wall having an opening therein of a size sufficient to permit said expendable charge portion to pass axially therethrough, a member having an exhaust outlet therein, and means for connecting said member with said second end plate wall and for moving said member axially into engagement with the adjacent open end of said metal tube until the opposite open end of the latter engages said first end plate wall, said member, said second end plate wall, and said metal tube forming a combustion chamber within which said gas-generating charge is expended.

2. A power gas-generating assembly as claimed in claim 1 wherein the said expendable charge portion is provided with ignition means for initiating the decomposition of the said annular solid gas-generating charge, said ignition means being disposed in the end of said expendable charge portion intended to face the first end plate wall of said reusable frame portion.

3. A power gas-generating assembly as claimed in claim 1 wherein the ends of said metal tube are parallel and accurately squared and said first end plate walls and member are grooved so as to enable gas-type joints to be formed with the ends of the metal tube of said expendable charge portion.

4. A power gas-generating assembly as claimed in claim 1 wherein said first end plate wall is provided with a safety disk adapted to burst at a predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS 196,019 Hooper Oct. 9, 1877 6 Emery Dec. 6, Vautin Sept. 16, de Ganahl Sept. 24, Rutishauser et a1. Aug. 26, Skinner Aug. 10, Lubbock et a1. Aug. 24, Mace et a1 Nov. 30, Parsons Oct. 11, Lauritsen Sept. 2, MacDonald Oct. 14,

FOREIGN PATENTS Germany Sept. 6, France June 3,

OTHER REFERENCES Astronautics (No. 33), March 1936, pages 8 and 11.

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