LOCKING UNIT FOR A MOVABLE DISTANCE DEVICE

Abstract: The invention refers to a locking unit for a movable dis­ tance device (3) used together with a projectile, which dis­ tance device is locked by a backwardly converging conical surface and a number of balls (11) so that the distance device (3) at the acceleration of the projectile is pinched to the con­ ical surface when the balls (11) are moving backwards in the formed wedge-shaped chamber (10).

Description: Locking unit for a movable distance device TECHNICAL FIELD: The present invention refers to distance devices, which are used together with shells, principally of the hollow charge type, in order to achieve a certain distance (stand-off) between the point where the ignition of the explosive charge is effected and the target. When using shells of the burster type the distance aims at achieving detonation before hitting the ground or before striking the target. When using shells of the hollow charge type the distance aims at achieving a fully developed hollow charge jet. BACKGROUND ART: Accordingly when using hollow charged shells it is important that the hollow charge jet is given the opportunity to be fully developed in order to attain an optimal effect in the target. This is achieved by causing the charge to ignite at a certain distance before the shell reaches the target. The theoretical optimum of the distance is 6-8 calibres which at a calibre of 15 cm should correspond to a distance of maximum 120 cm. From a ballistic point of view one can not tolerate distance devices that long, but the choice of their length is chosen with respect to the practical use, the ballistical properties and the optimal development of the hollow charge jet. The ignition system is preferably electromechanic which causes that parts of the electric ignition system must be placed a short distance in front of the charge, i.e. in the front end of the distance device. A disadvantage about existing distance fuse devices is that they can not be made long enough without being practically cumbrous in the field. Is has previously been suggested that a distance device should be designed telescopically so that the device should be protruded in several sections to its full length just as the shell has left the barrel. The disadvantages of such a layout are that the design is to heavy in consideration of its function and practice. Besides, this construction is too complicated concerning the locking of the sections and the layout of the electrical system in the distance device. THE PURPOSE OF THE INVENTION: The purpose of the present invention is to eliminate the disadvantages previously mentioned and to produce a locking mechanism influenced by acceleration for a movable distance device for the fuse of a shell e.g. of the hollow charge type. SUMMARY OF THE INVENTION: The purpose mentioned above is achieved by the characteristics of the device as presented in the attached claims. In the following,a distance device means the device arranged in front of and in connection with the front casing or the cover of the shell possibly as a part of the fuse of the shell. According to the invention the distance device is shaped as a cylindrical tube which can be inserted in the outer casing of the shell in order to minimize the total length of the shell during transport. When the shell is being primed the tube is pulled out of the outer casing and is locked to the outer casing. The locking mechanism according to the invention is based upon the desirability when using a movable distance device together with a fuse, of preventing the distance device to move considerably in relation to the rest of the body of the shelL. The present invention consequently concerns a mechanism to ensure that after the moment of ejection the distance device will not move towards the body of the shell a longer distance than what is acceptable in consideration of function and safety. BRIEF DESCRIPTION OF THE DRAWINGS: The invention will now be further described by working examples with numerals referring to the relevant parts of the drawings. Figure 1 shows a cross section through an electromechanic fuse provided with an axially movable distance device in its elongated position in a hollow charge shell. Figure 2 shows an embodiment of the locking mechanism according to the invention. DESCRIPTION OF THE INVENTION: The fuse according to figure 1 is built up by an outer casing 1 in which a guide tube 2 is arranged. In the front end of the guide tube 2 a conical ring sleeve 4 is arranged. In an annular inner cavity 8 in the conical ring sleeve 4 a wedge ring 5 is arranged around the distance device 3. The cavity 8 could also be made directly in the front part of the guide tube 2. The wedge ring 5 is influenced forwards by a compression spring 6, i.e. forces the wedge ring 5 to slide forwards along the distance device 3 towards a collar 7 in the conical ring sleeve 4. The collar 7 is formed by the front limiting surface of the annular inner cavity 8 of the conical ring sleeve 4. Furthermore in the cavity 8, between the wedge ring 5 and the conical ring sleeve 4 an internally conically backwards converging conical ring 9 is arranged, which conical ring 9 is intended to achieve a wedge-shaped chamber 10 in the cavity 8. In this backwardly tapering wedge-shaped chamber 10 a number of balls 11 are mounted. Each ball 11 in its unlocked position is in contact with the front camfered surface 12 of the wedge ring 5. This camfered surface 12 forces the balls 11 out of contact with the distance device 3 when the wedge ring 5 is moving forwards. In this position the distance device 3 can consequently be moved either forwards or backwards. Each ball 11 is furthermore in contact with the collar 7 of the conical ring sleeve 4 and wi*h the front part of the conical surface of the conical ring 9. The way this locking mechanism functions is that the distance device 3 is manually pulled out before the loading of the shell. At the ejection moment the parts of the shell is influenced by a powerful acceleration whereby the forces of inertia cause the distance device 3 and the wedge ring 5 to move backwards in relation to the remaining parts of the shell. When the wedge ring 5 compresses the compression spring 6, the balls 11 are released whereby these too are pressed backwards by the forces of inertia in the converging wedge shaped chamber 10. The wedge ring 5 does not any longer lift the balls 11 out of contact with the distance device 3. Consequently the balls 11 are pressed backwards in the converging wedge shaped chamber 10 until the balls 11 are wedged between the distance device 3 and the conical ring 9. Consequently the diameter of the balls 11 is smaller than the wedge shaped chamber 10 in the front part of the chamber and the diameter of the balls 11 is greater than the wedge shaped chamber 10 in the rear part of the chamber. Thereby the distance device 3 is locked by the balls 11 and the conical ring 9 to the conical ring sleeve 4. Hereby the distance device can be made of a material softer than the balls, whereby a certain penetration of the balls into the distance device is made. The conical ring too can be made of a material softer than the balls whereby a penetration of the balls is also obtained in the conical ring. An advantage of this embodiment is that an irreversible locking can be obtained of the distance tube in relation to the conical ring sleeve and thereby the remaining parts of the shell. An other embodiment is obtained by removing the wedge ring 5 with its compression spring from the first embodiment described so that the balls 11 even in an unlocked position are in contact with the distance device 3. The cavity 8 is hereby being made smaller and is used only for containing the conical ring 9 and the balls 11. In this embodiment the distance device can not be pushed back into the fuse after elongation as the balls 11 then will lock the distance device 3. An other embodiment can be obtained by providing the guide tube with an internally conically converging surface in order to eliminate the need of both a separately used conical ring and a conical ring sleeve. Further embodiments can be made by varying the design of the conical ring sleeve 4 and the guide tube 2. For example the guide tube 2 and the conical ring sleeve 4 can be one element in which the conical ring 9 and the wedge ring 5 are locked in its position by a check nut or the like at the front part of the element.

Claims: Claims: 1. Locking unit for a movable distance device (3) used together with a projectile characterized In that the distance device (3) is cylindrically formed and axially movable in a guide tube (2) in the front part of the projectile and that the guide tube (2), directly or indirectly shows an annular cavity (8) facing the distance device (3) and that a backwardly converging conical surface facing the distance device (3) is arranged in the cavity (8) and that the cavity (8) in its front part is mounted with a number of balls (11) which when moving backwardly in the formed conically wedge-shaped chamber (10) lock the distance device (3) in relation to the guide tube (2). 2. Locking unit as in claim 1, characterized in that a wedge ring (5) is slidably mounted to the distance device and interposed in the cavity (8) and that the wedge ring (5) from a forwardly directed force effects the balls (10) out of contact with the distance device (3). 3. Locking unit as in claim 2, characterized in that the wedge ring (5) in order to bring the balls (11) out of contact with the distance device (3) is equipped with a camfered outer front surface (12) converging forwardly. 4. Locking unit as in any of the previous claims, characterized in that the diameter of the balls (11) is smaller than the wedge-shaped chamber (10) in the front part of the chamber and that the diameter of the balls (11) is greater than the wedge-shaped chamber (10) in the rear part of the chamber. 5. Locking unit as in any of the previous claims, characterized in that the wedge-shaped chamber (10) is formed by a conical ring (9) with its inner conical surface mounted in the cavity (8).

Inventors: SUNDVALL, KENNETH
Applicants: AFFARSVERKET FFV
Application year: 1986
Main classification: F42C1
IPC codes: F42B12, F16B7