The Works Of Messrs. Schneider And Co.

BREECH-MECHANISM FOR HEAVY GUNS. 209 the breech-screw, with obturator and movable head, the supporting bracket, with the working gear, and the firing device. The breech-block lias three threaded parts and three interruptions. The obturator consista of a plastic elastic dise placed between the niovable head and the front end of the breech-screw. The vent goes through the movable head-bar, the rear end being fitted with a brass bush, in which the fuse is placed. The supporting bracket consista of a curved plate, projections on which guide the breech-screw in its longi- tudinal travel. This plate is in one piece with the hinge that surrounds the vertical boit, round which the whole of the system is made to turn. The working gear consista of the mechanism which produces the unscrewing of the breech-block, and the swinging of the system to the side of the gun. The dise of the breech-block is extended, and forms a lever, at the end of which is fitted a set of tootheel gearing, working a pinion that engages a circular rack fitted to the rear end of the gun. The mechanism is operated by a handle keyed to the small pinion axle. A spring latch at the end of the lever blocks the mechanism, and holds the gearing fast as long as the breech-screw is not driven completely home ; this is to prevent any accidentai displacement of the breech-screw during the manœuvres which follow the unscrewing. To withdraw the breech-block when it is unscrewed, the gunner acts on the jointed hand-lever by raising its two arms. In so doing, a cam at the top part of the lever bears on the rear end of the breech, and facilitâtes the release of the obturator ; then, by pulling the whole of the system to the rear, the breech-block is withdrawn from the seat ; anti-friction rollers are placed on the guides to facilitate the movement of the block. The bracket is turned round to the side of. the gun by acting on the lower handle, which works a spindle passing under the bracket, the spindle being fitted with an endless screw that engages a hélicoïdal sector fixecl to the gun. A swinging latch unites the bracket to the breech-block and to the gun alternately. A latch bolt is used for percussion firing ; this contains a hammer worked by a spring, and which moves in a groove transversal to the breech-block disc. As soon as the opening motion is starteel, the end of the bolt which, when the breech is closed is situated in a slot cut in the rear surface of the gun, rises up the incline on the left-hand side of the slot, and travels in the circular groove with which the slot is connected; the hammer- spring is thus set, and the hammer is brought out of the centre of the vent. Prématuré firing is thus rendered impossible. To open the breech, the block is turned round 60 deg. by working the upper handle ; this disengages the threads, and the breech-block can be withdrawn by acting on the jointed handle; the obturator being previously released, the lower handle is then turned to cause the whole of the system to swing round to the side. For closing the breech, tbe above actions are repeated inversely. Figs. 699 to 702, Plates CXX. and CXXL, show the breech closed, the breech-block unscrewed, the breech-block withdrawn from the seating, and the breech completely open. Breech Screw with Percussion Firing- (Figs. 703 to 706, Plate CXXL).—This example has been chosen to illustrate the types of Schneider-Canet breech-blocks, the closing and opening of which are effeeted mechanically throughout, by turning the crank handle always in one I direction. The mechanism comprises the breech-block, its plastic obturator and movable head, the bracket with the working gear, and the firing device. The breech-block is made with four threaded parts and four interruptions. The obturator consista of a plastic elastic composite disc, specially shaped, and placed between the movable head and the front end of the breech-screw. On the rear end of the latter is fixed the tooth sector by which the block is turned. The bracket consista of the support and the breech mechanism. The support carries the breech-block as it is displaced, and is made to turn round a vertical hinge bolt. The breech mechanism comprises the crank that works the horizontal spindle of the driving screw ; the latter engages direct with a toothed wheel fitted to the vertical hinge bolt, and effects all the opening motions. The hinge bolt consists of an endless screw mounted in two Hearings on the rear end of the gun, and on which travels a rack made to slide, in the rear, in two vertical slots which prevent it from turning round. The rack is fitted at its lower part with a pinion which, when the breech-block is unscrewed, engages the threads of one of the toothed sectors, and effects the withdrawal of the breech-block from the seating. The percussion firing mechanism consists mainly of a hammer worked by a spring. When the opening action is started, the tenon fitted to the bolt (and which, when the breech is closed, lodges in a notch cut in the support), rises up the inelined plane to the left ; this sets the firing spring, and removes the hammer from the vent. At the same time, the safety key engages in its slot, and, driven by its spring, becomes fixed in a socket provided for it in the bolt. When the breech is closed, the rim of the breech-block cornes in contact with the support, the bolt key engages in its slot, and leaves the bolt free to slide in its groove. As the hammer cannot be set free, and as the striker is not opposite the vent, so long as the breech is not completely closed, all risk of accidentai firing is avoided. To open the breech by turning the crank, the vertical endless sci-ew is set in motion, the rack lises and engages the toothed sector fitted to the rear of the breech-block, the latter becoming unscrewed. When the rack is at the top of the endless screw it is made to revolve, the pinion with which it is fitted engages the threads of the breech-block, and brings this back until the bracket suides cause it to stop. On continuing to turn the crank, the whole system swings to the side of the gun. To