Patent GB-721541-A (GB)
Title: Improvements in or relating to safety devices for apparatus containing substances capable of generating pressure by the combustion thereof
Inventor: CONWAY HUGH GRAHAM
IPC: F42B15/00
Filed: 1951-08-31
Abstract: 721,541. Safety devices for rocket motors. BRITISH MESSIER, Ltd. Aug. 26, 1952 [Aug. 31, 1951], No. 20655/51. Classes 9(1) and 9(2). A rocket motor or similar device for generating combustion products under pressure is provided with a safety plug which can be blown out when in the "storage " position but is fast in the " armed " position, the plug being secured to the forward end of the motor by means of a spring collet connection. This connection will yield to allow the plug to be withdrawn but may be locked by engagement with an annular face on a locking member movable longitudinally into or out of engagement with the collet, as described in Specification 527,225, [Group XXXIII]. The propellant chamber 11 of the rocket motor is provided with a hemispherical forward end on to which is fitted a conical nose 13 of thin metal. Welded to the chamber 11  is a pressure release ring 14 whose bore is coaxial with the chamber. A steel plug 16 secured by a flange 33 to the nose 13 fits within the ring 14 and carries flexible steel claws 17 passing through the ring into the chamber 11. Heads 18 on the claws have inclined faces which overlap correspondingly inclined faces 19 at the inner end of the ring 14. Should the propellant be accidentally ignited during storage the collet-like assembly of prongs 17 and heads 18 are free to contract under the pressure developed, the heads 18 then slide out of engagement with the surfaces 19 and out of the ring 14 as the ring is driven outwards. To lock the plug in position, a ring 20 is provided which can fit within the claws to prevent their collapse. This locking ring 20 is formed on the edge of a disc 21 held in position by a sliding rod 22 passing through the plug 16. Fitted over the inner end of the ring 14 is a bridge 23 carrying a fuze and a shield 24 holds the propellant in position. The sliding rod 22 is actuated to move the locking ring 20 into the " armed " position, Fig. 1, or out of contact with the spring arms of the collet, the " storage " position, by means of a pivoted cam 25 integral with a release trigger 26. A spring 27 tends to hold the cam in the " armed " position until pulled across the axis of the cam pivot, when it holds the trigger open in the safety position. The trigger is then projecting through the casing and thus indicates that the rocket is not " armed " A roller 37 may be provided on the end of the trigger so that as the rocket is pushed into the firing position on the launching platform, the roller comes into contact with a fixed catch on the platform, which catch forces the trigger backwards into the " armed " position. In Fig. 4, the locking ring 20 forms part of a sleeve 30 fitting within a sleeve 31 which carries the collet prongs 17. The sleeve 30 is movable longitudinally relative to the prongs 17 and is fastened to the projectile nose-tip 32. By pushing the tip 32 inwards the locking ring 20 is moved into the locking position. For storage the tip is held by a split pin 35 passing through the sleeves 30, 31. In another construction, the locking ring 20 is connected by the sliding rod 22 and a rocking lever to a slidable member within the nose 13. The slidable member is connected to the tip of the projectile which is secured to the nose 13 by a split pin. On withdrawal of the pin the nose-tip can be moved outwards to operate the rocking lever and unlock the ring 20. The locking ring may carry micro-switches operated when the locking ring is moved to set in action other parts of the rocket mechanism. Specification 612,998 also is referred to.