The Works Of Messrs. Schneider And Co.

XXXI. -CONCENTRIC-THREADED BREECH-BLOCKS. TN a distinctive dass of breech mechanism adaptecl to --L the Schneider-Canet quick-firing guns, the block is made with concentric threads. The main feature of this new type consista in the adaptation to the gun of a block with a spherically-shaped face, the two. sides having parallel plane surfaces, with the rear hollowed out. The block thus formed fits in a suit- able socket cut in the rear of the gun. By this arrange- ment, it will be seen that a rotary motion opens or closes the bore by a single action ; in this respect the arrange- ment fulfils in the simplest manner the conditions required of breeeh mechanism. The displacement of the breech- block is etfected round a centre line, wliich may be set at any desired angle. A series of concentric threads, of equal section, cut in the breech-block cheeks, fit into correspond- ing grooves made in the seating, and insure the close con- nection of the block with the gun in the varions positions the former is required to take. Figs. ^719 to 721, Plate CXXIL, show the principle of this dass of breeeh-blocks. Besides the principal characteristie of this type, there are special points connected with the particular arrange- ments adopted for its manipulation, firing, &c. We shall review in the following descriptions the varions types that have been put into service, those for small and medium- calibre guns and those for large guns, first giving a descrip- tion of the Schneider-Canet splierical breech-block, from which the concentric-threaded type has been evolved. Schneider-Canet Spherical Breech-Block for Quick- Firing- Guns (Figs. 711 to 715, Plate CXXIL).—This type consista of a complété sphere made to turn in a spherical seat in the enlarged rear of the gun. It is held in position by a screwed ring at the back of the block, and the arrangement is completed by special mechanism for firing and extraction. In the centre of the sphere a hole is drilled, of the same diameter as the bore of the gun, so that the charge can be easily introduced. When the breech is open, the bore in the sphere corresponds exactly with that of the gun, while to close the breech it is sufficient to turn the block through 90 deg. : that is to say, into a vertical position (see Fig. 713). The device consists mainly of the following parts : Ça) the breech-block, with threaded ring in the rear ; (6) the working lever, in which part of the firing mechanism is fitted ; (c) the extractor. The ring, which bears against the back of the block, is of hardened steel, and is screwed into the rear end of the gun, the threads on the ring being either continuons or interrupted, as in ordinary breech-blocks. The spherical block is maintained in position by the smaller arm of the working lever, which contains a cylindrical extension form- ing a trunnion. When the lever is fitted in the breech- block, the latter can only turn round the axis of this trunnion, the rotary travel being limited by a stop pro- vided in the swell of the gun, and by the smaller brauch of the extractor, which the block meets when the opening motion is complété. The working lever is the only mechanism visible when the breech is fitted up ready for service, either when the breech is open or closed (see Figs. 711 and 712). Firing is obtained by a striker that acts direct on the fuse ; it is worked by a two-armed lever that oscillâtes in the body of the spherical block. One of the arms of this lever is go vern ed by a hammer and a spring fitted to a cylinder placed in the centre line of the smaller arm of the working lever, which is grooved out to receive it. When the hammer is drawn back, the firing spring is pressed clown by a cam trigger of the same type as that described for the one-motion breech-blocks for 6-in. quick-firing guns. The trigger is fitted completely in tlie thickness of the working lever. To cause the fuse to act, it is sufficient to pull, by means of the firing line, on the lever fitted with the cam, until the latter escapes the corresponding tooth fitted to the hammer ; when the hammer is freed, it returns with a shock and acts on the two-armed lever that drives the striker against the fuse. The extractor consists of a round horizontal rod guided in a groove cut in the bore, and on which are jointed two clutches thai act on the cartridge-case flange. The case is ejected when the horizontal rod is driven forward by the spherical block, as the opening action is completed ; the extractor Works as a lever, and the clutches are driven backwards and draw out the case, the extractor resuming its position on the introduction of a cartridge-case. Its operation is insured by a stud that forms the head of a spring fitted in the thickness of the block, and wliich cornes in contact with the horizontal rod, thus skifting it when the opening motion is complétée! and clearing it immediately afterwards. To prevent accidentai opening of the breech, the working lever is provided »with a movable handle fitted with a spring, and in the continuation of which is a lateral catch ; when the breech is closed and the gunner releases the handle, the catch is driven into a projection on the gun, and the breech-block is thus held in position. Until the breech is completely closed, the striker, which moves with the spherical block, is not opposite the