GB1599242A

GB1599242A - Device for establishing a rolling reference in projectiles

Info

Publication number: GB1599242A
Application number: GB16119/78A
Authority: GB
Original assignee: SERAT; Airbus Group SAS
Current assignee: SERAT; Airbus Group SAS
Priority date: 1977-04-26
Filing date: 1978-04-24
Publication date: 1981-09-30
Also published as: IT7849069A0; IT1102193B; FR2389092A1; DE2816079C2; DE2816079A1; FR2389092B1; DE2857448C2

Description

(54) DEVICE FOR ESTABLISHING A ROLLING REFERENCE IN PROJECTILES (71) We, SOCIETE D'ETUDES, DE REAL ISATIONS ET D'APPLICATIONS TECHNIQUES, a French Company, of 134, Boulevard Haussmann, 75008 Paris, France, and SOCIETE NATIONALE INDUSTRIELLE AEROSPATIALE, a French Company, of 37 Boulevard de Montmorency. 75016 Paris, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to inertial devices used in projectiles such as missiles and rockets to establish a rolling reference, by which is meant a reference operable to indicate the angular position of a projectile, rotating about its longitudinal axis, in relation to a system of axes located on the ground.

Among the known means designed to carry out this function, mention may be made of gyroscopes and accelerometric systems, for example. These devices are complicated and costly, and they comprise delicate mechanisms or components which render them unsuitable for withstanding very great accelerations such as those to which a projectile, fired from a cannon for example, is subjected.

The present invention seeks to provide a simple and inexpensive device for establishing an angular reference, which device also offers the advantage of being able to function under very great acceleration imposed upon firing as well as that occurring during flight due. for example, to the guiding action or vibration of the projectile.

According to the invention there is provided a device for establishing a rolling reference in projectiles, said device comprising a fly-wheel, the inertia of which acts to oppose its own rotation and whose axis is parallel to the longitudinal axis of the projectile. means for rotatably mounting the flywheel on the body of the projectile said mounting means having a very low coefficient of friction and opposing any lateral acceleration to which the fly-wheel may be subjected, means for opposing the effect on the flywheel of high longitudinal acceleration occurring upon launching of the projectile, and detector means operable to determine the angular position of the fly-wheel with respect to the body of the projectile.

The invention applies the inertia system to a fly-wheel so as to obtain angular stability in the projectile with respect to the reference system on the ground. The angular position of the projectile relative to the fly-wheel is indicated, for example, by picking up evenly spaced graduations on the fly-wheel with the aid of a photo-diode. The fly-wheel is guided in rotation about an axis which is parallel to and preferably coaxial with the axis about which the rolling movement of the projectile takes place; the mass of the fly-wheel creates an inertial force which opposes the rotary drive transmitted via the frictional forces inherent in the fly-wheel mounting means.

The precision of the device depends upon the relationship between the force of inertia and upon the frictional forces. Since the force of inertia is due to the moment of inertia, i.e. to the mass and diameter of the fly-wheel, it is limited by the mass and the space requirement permissible in the projectile.

In a first embodiment of the invention, the means for mounting the fly-wheel comprises a spindle centred in a bearing by the pressure applied by a fluid which is passed into the gap formed between the bearing and the spindle through a set of spaced ducts which extend into the bearing to centre the spindle therein.

In order to establish a substantially constant delivery rate through the ducts, they are preferably supplied at a high pressure by way of means such as for example capillary diaphragms or porous plugs which result in a very high pressure-loss as compared with those occurring in the bearing itself. Consequently, the variation in pressure-loss due to eccentricity of the spindle will result in a change in delivery of only the second order approximately, so that delivery can therefore be regarded as substantially constant.

When the device is fitted in a projectile subjected to very high acceleration upon launching, then in one embodiment of the invention and for the purpose of obtaining fluid under high pressure, said acceleration is used to create the force and energy necessary for compressing an elastic system which pressurizes the fluid necessary for supplying the bearing. Preferably, this is achieved by storing the required energy by compressing a quantity of gas by means of a piston which is displaced by inertia under the effect of the acceleration. A locking device immobilizes the piston on completion of its stroke so as to keep the gas under compression, and thereafter the gas, during its entire decompression phase, acts on the fluid to provide the required pressure and delivery rate.

In a preferred embodiment of the invention, one means for achieving the above comprises a gas-filled deformable envelope closed off by a flexible wall in contact with the fluid which is enclosed in a reservoir which communicates with the ducts which extend into the bearing. The deformable envelope is fitted in a cylinder below a piston formed by the end-face of the structure that comprises a bearing unit and supports the fly-wheel. Under the effect of acceleration, the piston flattens the gas-filled envelope against the bottom of the cylinder so that the envelope is heavily compressed. After the piston has been immobilized in the cylinder, the flexible wall, which separates the fluid from the compressed gas, transmits the forces which create the pressure and cause the fluid to be expelled so as to supply liquid to the bearing.

The manner in which the fly-wheel is rotatably mounted on the projectile body provides a very low frictional torque, since only the viscosity of the liquid is involved in the movement. The use of, for example, very fluid silicone oil enables precision devices to be provided because of the small change in viscosity with temperature and the low chemical inertia of this material, and the devices so obtained can be used over a wide temperature range. Furthermore, extended storage does not adversely affect their performance.

The means for opposing the effect of longitudinal acceleration may be formed by a hydraulic stop which consists of a piston against which the fly-wheel bears; the piston is displaceable in a cylinder containing liquid identical to that used for supplying to the bearing. The forces applied to the fly-wheel due to acceleration of the projectile are transmitted to the liquid in the cylinder by the piston which thus performs the function of a brake, and no friction, other than that due to the viscosity of the fluid, occurs. To limit the pressure in the fluid, particularly when acceleration is high, the diameter of the piston is greater than that of the bearing, and the opposing cylindrical surfaces of the piston and cylinder and consequently the friction increases in the same proportions.

Since this friction is likely to affect the precision of the device if it persists throughout the duration of the flight of the projectile.

means are preferably provided for disengaging the piston from the fly-wheel when the high launching acceleration ceases, so that friction is consequently limited to that due to the bearing.

In order that the invention may be better understood, several embodiments thereof will now be describedby way of example only and with reference to the accompanying drawings in which: Figure 1 is a sectional view of the device of the invention prior to its becoming functional; Figure 2 is an enlarged transverse section of part of the device of Figure 1: Figures 3 to 5 are diagrammatic vertical sections through the device of Figure 1, shown in various operative positions; Figures 6, 7, 6a and 7a are vertical sections through a further embodiment of the device of the invention. illustrated in various operative positions, and Figures 8 and 9 illustrate a still further embodiment in vertical section.

Reference will first be made to Figure 1, which shows one embodiment of a device according to the invention. The device is of generally frusto-conical shape to enable it to be fitted in, for example, the tapered end of a projectile.

The device comprises a fly-wheel 10 provided with a collar 12 which bears against a piston 14, and with a spindle 16 rotatably mounted in a bearing 18 formed in a support 20. The spindle 16 is centred in the bearing 18 by the action of pressure applied by a fluid which is passed into the gap formed between the bearing and the spindle as will be explained hereinunder with reference to Figure 2.

In the plane of Figure I a duct 22 is provided which extends into the bearing 18 and which is supplied with pressurized fluid 24 via a pipe 26. A pressure reducer in the form of a porous plug 28 made of a sintered metallic powder is provided at the entrance to pipe 26.

The pressurized fluid is delivered through three evenly spaced ducts such as that shown at 22, 22' and is collected through two channels 30. connected to discharge ducts, not shown, after it has passed through the gap between the spindle 16 and the bearing 18.

The fluid used for the bearing, which for example may be silicone oil, is contained in a cavity 24 acting as a reservoir formed in the base 40 of the support 20. The fluid is enclosed within the cavity 24 by a flexible wall 32 of light-alloy material. The wall 32 also acts to enclose a deformable metallic capsule 34 containing air at atmospheric pressure.

The base 40 of the support 20 performs the function of a piston. Under the effect of an internal acceleration y, a blocking means, which is designed to hold the various elements forming the above described device in the position illustrated in Figure 1, and which is formed by a retaining ring 36, is retracted and only moves into the blocking position again when the retaining ring 36 moves to a position opposite a channel 38 machined in the base 40.

The, by this time, highly compressed air in the capsule 34 applies thrust to the flexible wall 32 to provide the fluid pressure necessary for the correct functioning of the bearing.

The base 40 is secured in the projectile in such a way that the axis of rotation of the fly-wheel 10 is coincident with the axis about which the rolling action occurs.

A hydraulic brake designed to oppose the effects of longitudinal acceleration is formed by the piston 14 which bears against silicone oil 42' contained in a cylinder 42. As will be seen later, a circular magnet 44 secured to the support 20 and having a longitudinal field enables the hydraulic brake to be disengaged from the fly-wheel. Ths magnet is made of rare earth material of the samarium-cobalt type, which enables very strong magnetic forces to be obtained. An armature 46 is formed by silicon-steel discs secured by a force-fit on the median portion of the fly-wheel 10, the creation of Foucault currents thus being prevented. By way of example, the position occupied by the fly-wheel may be monitored by an optical-electronic detector 48 which generates an impulse each time a graduation mark 50 passes before it.

Particular reference will now be made to Figure 2 which shows, in section, the spindle 16 of the fly-wheel, and its guide bearing 18.

The spindle 16 is centred in its bearing by the action of the pressure of a fluid which is passetl into the gap formed between the bearing and the spindle, by way of ducts 22 and 22'. For the purpose of simplifying the drawing, only two ducts, supplied with fluid under pressure, are shown. In practice it is necessary to provide at least three ducts to achieve two-directional centring.

The spindle is shown as being off-centre, by an amount d, in relation to the bearing, and this off-centre position results in a peripheral gap consisting of two portions S 1 and S2 of different section. Assuming a constant delivery rate through the ducts, there results a different pressure loss as between the portions S1 and S2, the loss of pressure in portion S1 being greater than that in portion S2. These different pressures result in a force F which is applied to the spindle in a direction which tends to reduce and thereby cancel out the eccentricity d.

Reference will now be made to Figures 3, 4, and 5 in order to explain the relationship between the magnet 44, the piston 14 and the armature 46. It will be noted that these Figures illustrate diagrammatically only those parts of the device with which the following description is concerned.

The inertia fly-wheel 10 is made of nonmagnetic material, and the piston 14 and armature 46 are made of a non-remanent ferro-magnetic material. Figure 3 illustrates the device in the stored position. The attractive force of the magnet 44 acts on the two ferro-magnetic components 14 and 46, but mainly to the piston 46 which is nearer to the magnet. The resultant of the magnetic forces causes the piston 14 to be urged towards the magnet 44 thus causing the collar- 12 to be trapped between the piston 14 and the magnet. The movable components are thus held in the position shown in Figure 3. In this position, the collar acts as a seal to prevent fluid from leaking from the cylinder 42 during storage of the device.

As soon as acceleration occurs, the assembly consisting of the fly-wheel and the piston, subjected to a very much greater force than that provided by the magnet, moves backward rapidly until the piston comes into contact with the fluid in the cylinder 42.

Figure 4 shows the position of the movable components during acceleration. The piston 14 has moved down in the cylinder due to leakage of fluid past the piston. The armature 46 has moved to a position below the median plane of the magnet 44. During this movement the piston performs the function of a hydraulic brake.

Figure 5 illustrates the position of the movable components after acceleration.

Once the acceleration drops to a sufficiently low value the attractive force of the magnet 44 draws the armature 46 into the equilibrium position in which a minimum air-gap occurs between the magnet and the armature. At this position the piston 14 and the fly-wheel 10 are disengaged from each other and the magnet applies maximum attractive force to the armature 46. This force prevents further axial displacement of the fly-wheel under the effect of any slight longitudinal acceleration which may occur during the flight of the projectile.

The ferro-magnetic armature 46 is laminated to prevent it from giving rise to Foucault currents likely to interfere with the freedom of movement of the fly-wheel.

In an alternative embodiment of the invention, the fly-wheel for providing a rolling reference includes a cable which is stretched between the inertia fly-wheel and the body of the projectile under the effect of the initial acceleration. Optionally, at least one of the ends of said cable is freed during rolling upon cessation of the acceleration occurring during launching, this end preferably being that in contact with the inertia fly-wheel.

Figures 6, 6a, 7 and 7a illustrate a further embodiment of the invention in which this feature is used.

Figure 6 illustrates the device in the position occupied during high longitudinal acceleration. The fly-wheel 10, centred about a hollow spindle 54 by means of two ballbearing units 52, bears on a part 56 by way of two lugs. The part 56 is retained by a multistrand cable 58 which is secured at its other end A to a structural part 60.

During longitudinal acceleration, rotary movement of the projectile is transmitted directly to the end A of the cable. The movement of the part 56, secured to the other end of the cable, depends upon the inertia of the fly-wheel and upon how the cable is constituted. It will be seen that the greater the inertia of the fly-wheel and the greater the length of the cable, the lesser will be the movement of the fly-wheel.

It is also possible to arrange that, when acceleration ceases, rotation of the fly-wheel is zero, or its angular velocity is zero, or its direction is opposite to that of the projectile.

For this, all that is necessary is to impart to the cable, when at rest, a twist in the direction corresponding to that in which the projectile rotates. Thus, when acceleration starts to take place, the cable tends to resume its position of equilibrium wherein the twist is zero. This untwisting transmits to the flywheel a movement in the direction opposite to that of the projectile. This arrangement renders it possible to compensate for the main part of the effect of rolling drive caused by friction during launching and flight, so that drift of the fly-wheel is greatly reduced.

Figure 7 illustrates the same device after acceleration has ceased. A spring 62 has applied thrust to the assembly consisting of the fly-wheel and the rolling bearings of the shock-absorbing unit thus separating the flywheel from that end of the cable which supported it during launching. The fly-wheel is therefore driven only by virtue of the frictional torque of the rolling bearings.

These bearings may be of very small dimensions since they have been protected by the cable during the considerable launching acceleration. Subsequently, only a slight driving action is applied to the fly-wheel, at least over quite short periods.

Figures 6a and 7a provide, on a larger scale, a view of that part ofthejust-described embodiment that is concerned with engagement and disengagement caused respectively by acceleration on launching and then by the cessation of this acceleration.

Figures 8 and 9 illustrate a third embodiment comprising an arrangement intermediate the two previous ones.

Figure 8 shows an inertia fly-wheel guided by two bearing units as in the previous embodiment. When high acceleration occurs the fly-wheel is applied against a hydraulic brake 66, the mode of operation of which is similar to that described above in relation to the hydraulic brake of Figures 1 to 5. Figure 9 illustrates the fly-wheel after acceleration has ceased, and the system described in connection with Figure 7 applies.

In Figures 6 to 9, the optical-electronic detector is illustrated diagrammatically under reference 64; this detector may be of the same design as the detector 48 described above with reference to Figure 1.

WHAT WE CLAIM IS: 1. A device for establishing a rolling reference in projectiles, said device comprising a fly-wheel, the inertia of which acts to oppose its own rotation and whose axis is parallel to the longitudinal axis of the projectile, means for rotatably mounting the flywheel on the body of the projectile said mounting means having a very low coefficient of friction and opposing any lateral acceleration to which the fly-wheel may be subjected, means for opposing the effect on the flywheel of high longitudinal acceleration occurring upon launching of the projectile, and detector means operable to determine the angular position of the fly-wheel with respect to the body of the projectile.

2. A device according to claim 1 wherein the means for rotatably mounting the flywheel comprises a spindle centred and guided in a bearing, and wherein the device further comprises means for supplying a liquid under pressure to the bearing.

3. A device according to claim 2 wherein the liquid under pressure is passed into a gap formed between the bearing and the spindle through ducts extending into the bearing, so as to centralise the spindle in the bearing.

4. A device according to either one of claims 2 or 3 wherein, before the liquid under pressure reaches the bearing, it is passed through a pressure reducer which causes a greater loss of pressure than that occurring in the bearing.

5. A device according to claim 4 wherein the pressure reducer comprises porous plugs made of a sintered metallic powder.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. flight of the projectile. The ferro-magnetic armature 46 is laminated to prevent it from giving rise to Foucault currents likely to interfere with the freedom of movement of the fly-wheel. In an alternative embodiment of the invention, the fly-wheel for providing a rolling reference includes a cable which is stretched between the inertia fly-wheel and the body of the projectile under the effect of the initial acceleration. Optionally, at least one of the ends of said cable is freed during rolling upon cessation of the acceleration occurring during launching, this end preferably being that in contact with the inertia fly-wheel. Figures 6, 6a, 7 and 7a illustrate a further embodiment of the invention in which this feature is used. Figure 6 illustrates the device in the position occupied during high longitudinal acceleration. The fly-wheel 10, centred about a hollow spindle 54 by means of two ballbearing units 52, bears on a part 56 by way of two lugs. The part 56 is retained by a multistrand cable 58 which is secured at its other end A to a structural part 60. During longitudinal acceleration, rotary movement of the projectile is transmitted directly to the end A of the cable. The movement of the part 56, secured to the other end of the cable, depends upon the inertia of the fly-wheel and upon how the cable is constituted. It will be seen that the greater the inertia of the fly-wheel and the greater the length of the cable, the lesser will be the movement of the fly-wheel. It is also possible to arrange that, when acceleration ceases, rotation of the fly-wheel is zero, or its angular velocity is zero, or its direction is opposite to that of the projectile. For this, all that is necessary is to impart to the cable, when at rest, a twist in the direction corresponding to that in which the projectile rotates. Thus, when acceleration starts to take place, the cable tends to resume its position of equilibrium wherein the twist is zero. This untwisting transmits to the flywheel a movement in the direction opposite to that of the projectile. This arrangement renders it possible to compensate for the main part of the effect of rolling drive caused by friction during launching and flight, so that drift of the fly-wheel is greatly reduced. Figure 7 illustrates the same device after acceleration has ceased. A spring 62 has applied thrust to the assembly consisting of the fly-wheel and the rolling bearings of the shock-absorbing unit thus separating the flywheel from that end of the cable which supported it during launching. The fly-wheel is therefore driven only by virtue of the frictional torque of the rolling bearings. These bearings may be of very small dimensions since they have been protected by the cable during the considerable launching acceleration. Subsequently, only a slight driving action is applied to the fly-wheel, at least over quite short periods. Figures 6a and 7a provide, on a larger scale, a view of that part ofthejust-described embodiment that is concerned with engagement and disengagement caused respectively by acceleration on launching and then by the cessation of this acceleration. Figures 8 and 9 illustrate a third embodiment comprising an arrangement intermediate the two previous ones. Figure 8 shows an inertia fly-wheel guided by two bearing units as in the previous embodiment. When high acceleration occurs the fly-wheel is applied against a hydraulic brake 66, the mode of operation of which is similar to that described above in relation to the hydraulic brake of Figures 1 to 5. Figure 9 illustrates the fly-wheel after acceleration has ceased, and the system described in connection with Figure 7 applies. In Figures 6 to 9, the optical-electronic detector is illustrated diagrammatically under reference 64; this detector may be of the same design as the detector 48 described above with reference to Figure 1. WHAT WE CLAIM IS:

1. A device for establishing a rolling reference in projectiles, said device comprising a fly-wheel, the inertia of which acts to oppose its own rotation and whose axis is parallel to the longitudinal axis of the projectile, means for rotatably mounting the flywheel on the body of the projectile said mounting means having a very low coefficient of friction and opposing any lateral acceleration to which the fly-wheel may be subjected, means for opposing the effect on the flywheel of high longitudinal acceleration occurring upon launching of the projectile, and detector means operable to determine the angular position of the fly-wheel with respect to the body of the projectile.

6. A device accordinging to any one of

claims 2 to 5 wherein the pressure and delivery rate of the liquid supplied to the bearing are created by using the acceleration occurring on launching of the projectile.

7. A device according to claim 6 wherein the liquid supplying means comprises a piston which is displaced by the high acceleration upon launching of the projectile to thereby compress a quantity of gas contained in a deformable envelope, said envelope comprising a flexible wall contiguous with a reservoir containing the liquid.

8. A device according to claim 6 wherein the piston is formed by the support for the bearing.

9. A device according to any one of the preceding claims wherein the means for opposing the effects of longitudinal acceleration comprises a hydraulic brake.

10. A device according to claim 9 wherein the hydraulic brake comprises a piston against which said fly-wheel bears, this piston, coaxial with the fly-wheel, being displaceable in a cylinder containing a liquid under pressure.

I 1. A device according to claim 10 further comprising means for disengaging the piston from the fly-wheel upon cessation of launching acceleration.

12. A device according to claim 11 wherein said disengaging means comprises a magnet and an armature whose magnetic interaction separates the piston from the flywheel when launching acceleration ceases.

13. A device according to claim 12 wherein before use, the moveable parts of the device are positioned by the attractive force of said magnet.

14. A device according to claim 13 wherein, before use, the attractive force of the magnet urges the piston against a collar integral with the fly-wheel, which collar cooperates with the cylinder to prevent leakage of liquid from the cylinder when the device is not in use.

15. A device according to any one of claims 12, 13 or 14, wherein the magnet is made of a rare earth material of the samarium-cobalt type.

16. A device according to any one of claims 12 to 15 wherein the armature is of laminated construction.

17. A device according to claim 16 wherein the armature is formed by a stack of silicon steel discs mounted on a median portion of the fly-wheel by a force-fit.

18. A device according to claim 1 wherein the means for opposing the effect of longitudinal acceleration comprises a cable consisting of a plurality of strands which, under the effect of initial acceleration, are stretched between the fly-wheel and the body of the projectile in a direction parallel to the axis of the projectile,

19. A device according to claim 18 further including means operable, during rolling of the projectile, for separating the flywheel from that end of the cable which supported it during launching.

20. A device according to either one of claims 18 or 19 wherein the wire is pretwisted to compensate the main part of the rolling drive effect caused by friction during launching and flight of the projectile.

21. A device according to claim 1 wherein the means for opposing the effect of longitudinal acceleration comprises a hydraulic brake, and wherein the fly-wheel mounting means comprises a plurality of bearing units.

22. A device according to claims 18 wherein following launching acceleration the inertia fly-wheel is supported only by its bearing units.

23. A device according to claim 22 wherein the bearing units are of small dimensions and therefore involve little friction.

24. A device according to any one of the preceding claims wherein said detector means is an optical-electronic detector.

25. A device according to claim 24 wherein the fly-wheel carries at least one graduated scale which enables the opticalelectronic detector to detect the position of the fly-wheel with respect to the body of the projectile.

26. A device according to claim 25 wherein the detector means is operable to count impulses corresponding to the rate at which the graduations pass in front of the optical-electronic detector.

27. A device for establishing a rolling reference in projectiles, substantially as hereinbefore described with reference to the accompanying drawings.

28. A projectile when fitted with a device according to any one of the preceding claims.