GB2117114A - Gyroscope - Google Patents

Abstract

A gyroscope assembly comprises a rotor mounted on a gimbal and run- up means to accelerate the rotor, wherein the run-up means comprises a shaft (40) axially movable between a rotor-engaging drive disposition and a rotor non-engaging free disposition, biasing means (48) to urge the shaft into the free disposition, a turbine disc (43) fixedly mounted on the shaft and having on its periphery vanes to be acted upon by an incident flow of fluid, and means e.g. a shearable pin (49) to hold the shaft in the drive disposition, against the action of the biasing means prior to said incident flow of fluid. During the pendency of said incident flow of fluid the pressure of the fluid flow holds the shaft in the rotor-engaging disposition against the biasing means. <IMAGE>

Description

SPECIFICATION Gyroscope This invention relates to a gyroscope and more particularly, but not exclusively, to a free gyroscope intended for installation in a guided missile.

It has previously been proposed to provide a free, otherwise called displacement, gyroscope in an aerial missile for the purpose of providing a reference against which the position of the missile in roll can be determined. See, for example, Proc.

Instn. Mech. Engrs. 1964-65, Vol. 179 Pt.3E, Paper 14, pp. 120-128. For reasons given in that Paper, a gyroscope having a cordite charge within its rotor was proposed, to operate upon the principle of the reaction wheel.

The present invention stems from a need to develop a roll reference gyroscope smaller than those described in the Paper referred to above.

Contrary to what is stated in the Paper, it has now been found that the use of the principle of the impulse turbine rather than of the reaction wheel may be better adapted to the goal of further miniaturisation.

In accordance with the present invention there is provided a gyroscope assembly comprising a rotor mounted on a gimbal and run-up means to accelerate the rotor, wherein the run-up means comprises a shaft axially movabie between a rotor-engaging drive disposition and rotor nonengaging free disposition, biasing means to urge the shaft into the free disposition, a turbine disc fixedly mounted on the shaft and having on its periphery vanes to be acted upon by an incident flow of fluid and means to hold the shaft in the drive disposition, against the action of the biasing means, prior to said incident flow of fluid and during the pendency of said incident flow of fluid, but not after the incident flow of fluid has ceased to cause any acceleration of the rotor of the gyroscope.

Usually, the gimbal is an inner gimbal of an inner and outer gimbal pair and, where the gyroscope is a displacement gyroscope for roll reference of a missile the rotational axis of the outer gimbal will usually be in line with the longitudinal axis of the missile.

The invention has particular application to guided sub-missiles carried by a larger guided missile. In such an application, a gyroscope of the smallest possible size is required.

The shaft is held in engagement with the gyroscope rotor prior to acceleration thereof by a shear pin connecting the disc and its housing, the pin being fractured upon the first impact of the accelerating jet of fluid on the disc periphery. The shaft is held in engagement during acceleration of the rotor by for example so shaping the vanes on the periphery of the disc that the incidence of the fluid jet thereon urges the disc to move axially, in a direction against the spring bias. Preferably, the rotor is caged by the said shaft.

For a better understanding of the invention, and to show more clearly how the same may be carried into effect, reference will now be made by way of example, to the accompanying drawings, in which: Fig. 1 is a view of an aerial guided missile, taken from one side of the missile, and with the missile skin partly cut away to reveal a roll reference gyroscope of the missile; Fig. 2 is a diametral section of that part of the missile which includes the said gyroscope, and of means external to the missile for accelerating the rotor of the gyroscope; Fig. 3 is a transverse section of the missle, through the centre of the rotor; and Fig. 4 is a section through the line IV--IV of Fig.

2.

Referring first to Fig. 1, a guided missile 10 carries a gyroscope 11 for the purpose of providing a reference against which the angle of the missile in roll can be measured. The gyroscope 11 has a rotor 12 which spins on an inner gimbal (not visible) about an axis which is, in Fig. 1, vertical and in the plane of the drawing. The inner gimbal is mounted to an outer gimbal 1 3 which pivots about an axis in line with the longitudinal axis of the missile.

In flight of the missile, with the rotor of the gyroscope spinning at high speed, a change of the roll angle of the missile will lead to an identical change of angle between the outer gimbal and the structure in which it pivots. The change of angle may be measured by potentiometer means.

Fig. 2 shows in more detail how the roll angle is measured. The outer gimbal 13 has a pair of aligned spigots on which it pivots within ball bearings, namely, an aft spigot 14 within an aft bearing 1 5 in an aft bulkhead 1 6 and a forward spigot 1 7 within a forward bearing 18 in a forward bulkhead 19.

The forward spigot 1 7 projects through the bulkhead 19 and provides a spindle 20 of the potentiometer device 21 in which a thin finger 22 wipes an annular stator 23 of the potentiometer.

Information from the potentiometer is fed to the navigation and steering apparatus of the missile by leads not shown in the drawings.

Turning now to Fig. 3, the rotor 12 is seen as comprising a pair of inertial masses 24 and 25 fixedly mounted on a shaft 26 by a lock-nut 27 housed in a recess 28 of the mass 24. A recess 29 in the mass 25 houses a head portion 30 of the shaft 26. The masses 24 and 25 are made identical, for eas of assembly of the rotor.

The shaft 26 is carried in a pair of ball bearings 31 and 32 which are themselves mounted within a core element 33 of an inner gimbal of the gyroscope. The inner gimbal pivots about the axis I-I in Fig. 3, which axis is defined by a pair of threaded bores 34 in the outer gimbal 13. The bores 34 each receive a threaded axle pin 35 which engages with the inner race 36 of a ball bearing 37, the outer race 38 of which mates with a recess in the core element 33, whereby the core element 33, and so the rotor assembly 12, may rotate freely on the axle pins 35, while the rotor assembly 12 spins at high speed on the core element 33.

The rotor is accelerated to the high speed at which it rotates in use by an external run-up means 39 comprising a drive pin 40 which engages with a recess 41 in the head 30 of the rotor shaft 26 in the manner of a dog clutch. As seen in Fig. 2, the pin 40 projects through a small hole 42 in the missile skin, so that, during the period when the rotor 12 and the pin 40 are engaged, the rotor is effectively "caged" by the engagement.

The pin 40 is part of an axle of a turbine disc 43 which is rotatable on the pin 40 and a stub axle 44 in a chamber 45 defined by a housing 46 and end plate 47. Some axial movement of the disc 43 within the chamber is possible so that, with the housing 46 in contact with the skin of the missile 10, the pin 40 may move axially into and out of engagement with the rotor 1 2. A disc spring 48 which acts between the housing 46 and the turbine disc 43 provides a spring bias which urges the pin 40 out of engagement with the rotor 12. A shear pin 49 located within bores in the housing 46 and the turbine disc 43 holds the pin 40 in engagement with the rotor against the action of the disc spring 48.

As best seen in Fig. 4, the disc 43 has on its periphery a plurality of identical vanes 50, each canted so that when a jet of fluid flowing along a flow passage 51 which is in the plane of the disc 43 impinges on the vanes, the disc is given an impulse not only to rotate but also to move axially such as to compress the disc spring 48.

In use of the gyroscope, the missile 10 is one of a number of sub-missiles carried in a carrier missile on a rig which includes a run-up means 39 for each of the sub-missiles. Immediately prior to flight of the sub-missiles separate from the carrier missile, a flow of gas is provided by means not shown along each of the flow passages 51, at a velocity sufficient immediately to shear the pin 49 and accelerate the rotor 12 to its operational speed in a period of around 0.20 seconds. On termination of the flow of gas, the disc no longer receives an impulse from the gas flow to move it so as to compress the disc spring 48, and so the disc spring 48 acts to disengage the pin 40 from the rotor 12. Such disengagement uncages the rotor. During flight of the sub-missile the rotor is not driven but merely "coasts".For the short fiights which such missiles experience, and with the increased angular momentum obtained in the present invention, this is acceptable.

Although gas-driven means are shown in the drawings for accelerating the rotor, other external run-up means are possible, e.g. hydraulic or electromagnetic devices or a gas-driven reaction wheel rotor.

Although a potentiometer device is shown for providing a signal indicative of roll angle, any equivalent device may be used.

By providing the inner gimbal of the free gyroscope as a core or housing within the confines of the rotor, so that the rotor need be only so small as to fit within the outer gimbal, rather than a gimbal itself within the outer gimbal, a proportionately larger rotor can be used and this permits the use of roll displacment gyroscopes in missiles of smaller diameter than has hitherto been possible.

Claims (5)

1. A gyroscope assembly comprising a rotor mounted on a gimbal and run-up means to accelerate the rotor, wherein the run-up means comprises a shaft axially movable between a rotor-engaging drive disposition and rotor nonengaging free disposition, biasing means to urge the shaft into the free disposition, a turbine disc fixedly mounted on the shaft and having on its periphery vanes to be acted upon by an incident flow of fluid and means to hold the shaft in the drive disposition, against the action of the biasing means, prior to said incident flow of fluid and during the pendency of said incident flow of fluid, but not after the incident flow of fluid has ceased to cause any acceleration of the rotor of the gyroscope.

2. A gyroscope as claimed in claim 1, wherein the shaft, biasing means and turbine disc are mounted in a missile and the rotor and gimbal are mounted in a sub-missible carried by the missile.

3. A gyroscope as claimed in claim 1 or 2, wherein the means to hold the shaft in the drive disposition prior to said incident flow comprises a shear pin connecting the turbine disc with its housing and which is broken by the effect of the first impact of the flow of fluid on the turbine disc.

4. A gyroscope as claimed in any one of the preceding claims, wherein the means to hold the shaft in the drive disposition during the pendency of said incident flow of fluid is a plurality of said vanes so shaped that the incidence of the flow of fluid on the shaped vanes urges the turbine disc to move axially against the spring bias, to maintain the turbine disc in the drive disposition.

5. A gyroscope substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.