This device serves as an automatic closure and insures a tight joint irrespective of wear. Moreover, it presents the advantage that, at the moment of opening, it distributes the fuel evenly in the generator; but on the other hand, it has the drawback of not allowing the fuel to be examined or shaken through the charging-box. In apparatus provided with this kind of valve, it is therefore advisable to furnish the upper part of the generator with agitating holes closed by an air-tight slide.
Slide-Valve.—The slide-valve closure consists of a smooth-finished metallic plate movable below the charging-box proper. Operated as it is from the outside, it is evident that the slightest play, the wearing of the pivot, or the weight of the charge, will form spaces between the plate and its seat through which air may rush in.
Furthermore, the manipulation of the slide-valve may be interfered with if too much fuel is put in the generator.
The valve or damper may move parallel to itself or swing about the operating axis. The Taylor apparatus
(Fig. 94) and the Bénier apparatus (Fig. 104) are provided with such valves.
The Pintsch generator (Fig. 96) is provided with a device which, properly speaking, is not a damper, but which consists of two boxes movable about a vertical axis and arranged to be displaced alternately above the shaft to effect the charging. This system effects only a single closure, but explosions are scarcely to be feared with an apparatus of this kind, owing to the considerable height of fuel contained between the charging opening and the gas-producing zone.
Cock.—The cock is applied particularly in the modern apparatus of the Otto Deutz Co. (Fig. 106) and the Pierson generator (Fig. 101). It consists of a large cast-iron cone, having an operating handle and an opening. The cone moves in a sleeve formed by the charging-box.
This arrangement appears to be preferable to the others on account of its simplicity and of the ease with which it can be taken apart for cleaning. Moreover, the fuel can be poked directly through the feed-hopper. In apparatus provided with a cock, it is advisable to place on the outside cover a mica pane through which the condition of the fuel may be examined without danger.
Feed-Hopper.—Below the charging-box is arranged, as a rule, a hopper tapered conically downward. This part of the generator should serve only as a storage chamber for fuel. It can therefore be made of cast-iron, and has the advantage of being removable, easily
replaced, and of allowing ready access to the retort for the purposes of examination and repair.