Modern Gasworks Practice

THE MECHANICAL HANDLING OF MATERIALS 287 machines introduced and comprises many commendable features. The simplicity of the entire arrangement is its chief recommendation. The machine consists of a pusher constituted of an outer cylinder containing two telescopic lams of sufficient, length to extend through, a 20-foot retort. Each. ram is provided with a stopper at its rear end, and on the smaller solid ram a pusher plate, similar in shape to the Fig. 204.— The Williams-MacPhee Pusher. retort but slightly smaller, is fitted. The ram is extended by admitting hydraulic pressure at the back of the cylinder, and by means of a special automatic return valve the pusher is withdrawn when the füll extent of its stroke has been reached. Withdrawal is effected by a chain, attached to the pusher head, which passes around a pulley connected to a subsidiary hydraulic ram. This withdrawing ram is pulled into its cylinder by the tension of the chain during the outward stroke. The automatic return is arranged for by introducing a tappet rod connected by a lever to