GB2221747A

GB2221747A - Producing motive power

Info

Publication number: GB2221747A
Application number: GB8818886A
Authority: GB
Inventors: Michael Sidney Russell
Original assignee: Kidde Graviner Ltd
Current assignee: Kidde Graviner Ltd
Priority date: 1988-08-09
Filing date: 1988-08-09
Publication date: 1990-02-14
Anticipated expiration: 2008-08-09
Also published as: GB2221747B; FR2635380B1; DE3924512A1; GB8818886D0; US4989465A; FR2635380A1

Abstract

A motive power generating unit, e.g. for spinning up a gyroscope rotor, contains a pyrotechnic gas-generating substance in the form of an azide composition 34. When electrically ignited, it produces nitrogen gas which is filtered at 40 and exits as a jet through orifice 26 to impact on buckets in the periphery of the rotor and spin it up to speed. The composition 34 may include transition metal oxides or alkali metal perchlorates as an oxidising agent. …<IMAGE>…

Description

1 2221747 APPARATUS AND METHODS FOR PRODUCING MOTIVE POWER The invention

relates to apparatus and methods of producing motive power.

According to the invention, there is provided motive power generating apparatus, comprising a pyrotechnic gas-generating substance in the form of an azide composition, actuating means for igniting the composition, and means responsive to the gas generated for producing a jet of gas acting in a predetermined direction.

According to the invention, there is further provided a gyroscope rotor assembly, comprising a gyroscope rotor. having its periphery formed with surface interruptions of predetermined form, means mounting the rotor for rotation, a container containing a pyrotechnic gas-generating azide composition, activating means for activating the gas generating composition to generate nitrogen gas, filtering means for filtering the generated gas, and gas jet directing means for directing a jet of the gas in such direction onto the surface interruptions in the periphery of the rotor as to rotate the rotor.

2 According to the invention, there is still further provided a method of generating motive power. comprising the steps of - activating a pyrotechnic azide-containing gas-generating composition so as to generate nitrogen gas, filtering the gas, producing a jet - of the generated gas, and directing the gas in such direction in relation to a mechanically movable member as to cause, directly or indirectly, movement in the said member.

A gyroscope rotor assembly embodying the invention, and methods according to the invention for producing motive power, will now be described, by w ay of example only, with reference to the accompanying diagrammatic drawings in which:

Figure 1 is a diagrammatic, partly sectioned, end view of the gyroscope rotor assembly taken on line I-I of Figure 3; Figure 2 is a cross-section on the line II-II of Figure Figure 3 is a diagrammatic side view of the gyroscope rotor assembly showing a motive power generating unit; 3 Figure 4 is a cross-section through the motive power generating unit of Fig. 3, taken on the line IV-1V of Figure 5; and Figure 5 is a section on the line V-V of Figure 4 Figure 1 shows a gyroscope rotor 10 mounted for rotation about an axis A in bearings 12 in a gimbal ring 13. Ring 13 is mounted for rotation, about an axis B, in a gimbal frame 14, by means of bearings 15. Gimbal frame 14 is mounted for rotation about an axis C by means of bearings in a gimbal frame 17 which is itself mounted for rotation in side walls 18 by means of bearings in the side walls. Walls 18 are upstanding from a base 20 and support a cover 21. The mounting arrangement for the rotor, allowing it freedom of movement about three orthogonal axes, is conventional. The mounting arrangement for the rotor is purely diagrammatic, and for the purpose of illustrating the operating principles to be described below.

In the specific example being considered, the gyroscope rotor is required to be placed into operation (that is, is required to be running at relatively high speed) in a relatively short period of time. This application therefore requires - the rotor to be run up to high speed 4 rapidly, from which speed it decelerates only slowly (because of its high inertia).

Figure 2 illustrates the gyroscope rotor 10 in cross-section. As shown, it is formed with peripheral "buckets" 22.

For the purpose of spinning the rotor up to speed, a motive power generating unit 24 is mounted adjacent to the rotor 10 as shown in Figure 3. The unit 24 will be described in detail below. However, when activated, it produces a jet of gas which is emitted via a jet orifice 26 (Figure 3) and strikes the periphery of the rotor 10 in approximately the direction of the arrow X of Figure 2. The impinging jet of gas thus impinges in the buckets 2@ and rapidly spins the rotor up to speed.

As shown in Figure 4, the unit 24 comprises an outer cylinder 30 in which is eccentrically mounted an inner cylinder 32. Cylinder 32 contains a pyrotechnic composition 34, to be described below, in its base. Adjacent the material 34 is mounted an electrically actuatable ignition arrangement 36 which is activated by electrical energisation of wires 38. A filter arrangement 40 is mounted in cylinder 32 next to the ignition unit 36.

The left hand end of the outer cylinder 30 is closed off by a cover 42 which thus covers the head space 43. The eccentric mounting of the cylinder 32 within the cylinder 30 provides a passageway 44 leading to the jet orifice 26.

In operation, electrical energisation of the wires 38 causes the ignition unit 36 to ignite the pyrotechnic composition 34. This burns rapidly and emits gas which passes through the filter arrangement 40, impinges on the underside of the cover 42 and passes down the passageway 44 and exits, in a jet, through the orifice 26 - and then impinges on the periphery of the gyroscope rotor 10 in the manner already explained.

The pyrotechnic composition 34 comprises an azide composition which thus generates nitrogen as the emitted gas.

Azide compositions which can be used comprise one or more alkali metal or alkine earth metal azides, usually including sodium azide as a major component, together with an oxidising agent. When heated above 600K sodium azide decomposes producing nitrogen gas and sodium metal:

6 2NaN 3 = 2Na+3N 2 Because of the low melting point of sodium metal, it presence is undesirable from a safety viewpoint. Various substances, such as one or more metal oxides, particularly transition metal oxides or alkali metal perchlorates, have been proposed for use as the oxidising agent to be combined with the sodium azide in order to react with the sodium and produce inert compounds which will not contaminate the nitrogen. For example, the sodium azide may be combined with ferric oxide to produce a reaction as follows:

2 1 6NaN 3 +Fe 2 0 3=2Fe+3Na 20+9N 2 A doped ferric oxide may instead be used to produce a reaction similar to that referred to above.

Another possibility is to use chromium chloride producing a reaction as follows:

6NaN 3 +2CrCl 3 =2Cr+6NaCl+9N 2 Cobalt oxide may instead be used which produces a reaction as follows:

7 6NaN3+C020 3 =2Co+3Na 20 +9N 2 Another possibility is to use nickel oxide producing a reaction as follows:

4NaN 3+2M0=2Ni+2Na 20+6N2 Certain metal oxides are also added to the basic compositions in order to provide a flux which binds the residual solids together and reduces smoke formation. Typical of such additives are silica, titanium dioxide, aluminium oxide, and boric oxide. An example of such a composition is as follows:

sodium azide 64% ferric oxide 26% silica 10% Additives may also be incorporated in the composition for the purpose of producing a purer evolved gas. Thus, for example, the silica in the above composition may be replaced, in whole or in part, by powdered activated molecular sieve. Certain additional transition metal oxides may also be used 'for this purpose, e.g. Cr2 0 3' C0304,Fe 304 and the like.

8 The filter arrangement 40 can be of any suitable type but is designed to remove impurities or other substances which could be -disadvantageous in various ways - such as, for example, by blocking the jet orifice 26. The filter can consist of a number of layers of metal gauzes or baffles or, for example, be a porous sintered metal filter. Further filtering action is obtained by the provision of the head space 43 above the filter 40 and by the arrangement by which the emitted gas impacts on the hard underside of the cover 42. Such impaction helps to separate out solid impurities. Instead of impacting the gas on the hard underside of the cover 42, the latter may be covered with a pad of compacted glass wool which retains the solid impurities.

Although the apparatus has been described for the purpose of spinning a gyroscope rotor up to speed, it will be appreciated that it could be modified for the purpose of providing motive power (not necessarily rotative) for any other suitable purpose.

The use of azide compositions for producing motive power in the manner described is advantageous over other gas sources. For example, gas sources comprising reservoirs storing gas under high pressure are large, 11 9 heavy and susceptible to leakage and unsuitable for many purposes because of these reasons. Gas sources using double-based propellant materials, such as cordites, are disadvantageous for a number of reasons.

The gas output of a cordite source is acrid and acidic and this is disadvantageous for many mechanical applications. For example, it may damage the bearings of gyroscope rotors. The chemical reaction taking place in cordite sources takes place partially in the gas phase. In other words, the gas is still burning when emitted. Its temperature may be damaging.

in certain applications, the resultant infra-red "signature" of the emitted gas may be disadvantageous because it renders the presence of the gas source detectable by suitable infra-red detectors. The emitted gas is also toxic to humans which may be disadvantageous in certain circumstances.

Furthermore

Claims

1. Motive power generating apparatus, comprising a pyrotechnic gasgenerating substance in the form of an azide composition, a ctivating means for igniting the composition, and means responsive to the gas generated for producing a jet of gas acting in a predetermined direction.

2. Apparatus according to claim 1, in combination with mechanically movable means positioned to receive and to react movably to the jet of gas.

3. Apparatus according to claim 1 or 2, including filtering means for filtering the gas before it is emitted.

4. A gyroscope rotor assembly, comprising a gyroscope rotor having its periphery formed with surface interruptions of predetermined form, means mounting the rotor for rotation, a container containing a pyrotechnic gasgenerating azide composition, activating means for activating the gas generating composition to generate nitrogen gas, filtering means for filtering the generated gas, and gas jet directing means for directing a jet of the gas in such direction 1 1 11 onto the surface interruptions in the periphery of the rotor as to rotate the rotor.

5. Apparatus according to claim 3 or 4, in which the filtering means comprises means for abruptly altering the direction of the generated gas by impacting it on a hard surface.

6. Apparatus according to any preceding claim, in which the said composition comprises a mixture of one or more alkaline metal or alkaline earth metal azides combined with an oxidising agent.

7. Apparatus according to claim 6, wherein the oxidising agent comprises one or a mixture of two or more metal oxides or alkaline metal perchlorates.

8. Apparatus according to claim 6 or 7, in which the azide is sodium azide.

9. Apparatus according to any one of claims 6 to 8, in which the oxidising agent is a transition metal oxide.

10. Apparatus according to claim 9, in which the transition metal oxide is ferric oxide.

12

11. Apparatus according to any preceding claim, in which the composition further includes at least one or more of silica, titanium oxide, boric oxide and aluminium oxide.

12. Apparatus according to any one of claims 1 to 5, in which the gas generating composition is a mixture of sodium azide, ferric oxide and silica.

13. Apparatus according to any preceding claim, in which the activating means comprises percussion means.

14. Apparatus according to any one of claims 1 to 12, in which the activating means comprises electrical ignition means.

15. A method of generating motive power, comprising the steps of activating a pyrotechnic az ide -containing gas-generating composition so as to generate nitrogen gas, filtering the gas, producing a jet of the generated gas, and directing the gas in such direction in relation to a mechanically movable member as to cause, directly or indirectly, movement in the said member.

16. A method according to claim 15, i 1 in which the filtering step includes the step of abruptly altering the direction of the gas by impacting it on a hard surface.

17. Motive power generating apparatus, substantially as described with reference to the accompanying drawings.

18. A motive power generating method, substantially as described with reference to the accompanying drawings.

0337S Published 1990 at The Patent Office. State House, 6671 High Holborn. London WC1R4TP. Further copies maybe obtamedfrom Thent=ce Sa3es Branch. St Mary Cray. Orpingtor. Nex.t BR5 3RD- Prired by Ml-jl.iplex techniques ltd. St Mary Cray, Kent,ton, 1'87