Charging-Box.—Like the other parts of the generator the construction of which has been discussed above, the charging-box should be absolutely air-tight.
On account of their greater security, preference should be given to double closure devices, which form a sort of preliminary chamber, owing to which the filling of the generator is made in two operations. The first operation consists in filling the preliminary chamber after opening the outer door. Upon closing this outer door, the second operation is performed, which consists in moving the inner door so as to cause the fuel in the preliminary chamber to drop into the generator. Stress has been laid on the greater safety of this type of charging-box for the reason that, with devices having a single charging-door, a sudden gust of air may rush in at the time of charging the furnace, and bring about an explosion very dangerous to the workman entrusted with stoking the furnace.
Fig. 109.—Door with refractory lining.
The closure is generally simply a removable cover, or may be a lid swinging about a hinge having a horizontal or vertical axis.
As regards the inner door, which is of great importance, in order to insure an air-tight joint, there are three chief types of closure:
- 1. The Lift-Valve.
- 2. The Slide-Valve.
- 3. The Cock.
The Lift-Valve.—The lift-valve is formed by a disk of conical or spherical shape moved up and down by means of a lever having a counter-weight for adjustment. The valve is used in the Winterthur (Fig. 92) and Bollinckx (Fig. 98) generators.