Fig. 215.
This valve and valve seat are circular in form, and made of bronze, as shown in Fig. 216. The valve has a lift of from 1 to 2 inches, and an area sufficiently large to reduce the velocity of the water flowing through it to a few feet per second.
At the beginning of the stroke the valve opens automatically, controlled, however, by a very simple and effective mechanical device, and it remains open practically during the entire stroke. When near the end, it is positively closed at the proper moment by the controller.
This valve, [see Fig. 216], may be briefly described as follows. The seat, A, is turned to slip into its place in the pump and is made tight by a round rubber hydraulic packing, B, in a groove near the bottom. A spindle or stud, C, in the center of this seat supports and guides the valve, D, which is made tight by a leather seal, E. The rubber collar or buffer spring holds the valve above its seat, and this valve unlike ordinary pump valves, always remains open except when pressure is brought to bear to close it. The valve bonnet, G, also forms the bearing for the valve stem with fork, which spans the spindle, C, at one end and having the valve lever and pin, H, for operating at the other end. The valve stem is made tight by a stuffing-box and gland as shown. The operation of this valve is substantially as follows.
Fig. 216.
At the beginning of the suction stroke the valve is opened by the rubber spring, F, the pressure upon the collar being relieved by lifting of the valve fork arms through motion of the eccentric.
It will be observed from an inspection of Fig. 215 that both the suction valve and the discharge valve are controlled by an eccentric—rock arm—and valve levers similar to the motion of Corliss valves.