This arrangement insures a uniform travel of piston under varying degrees of load. A momentary pause of the piston at each end of the stroke permits the water valves to seat quietly, without shock or jar, and the slow initial movement of the piston (whereby the water columns are started gradually) relieves the pump and piping of excessive strains.
To set the valve. Set the lever, A, plumb and the valve to cover all the ports equally.
THE DEAN BROS. PUMP.
The Dean Bros. pump is shown in [Figs. 295], [296] and [297].
Fig. 295.
The auxiliary valve, A, [Fig. 297], has in its face two diagonal exhaust cavities, B B1. The ports, C C1, and the exhaust port, D, are placed in a triangular position with one another, the diagonal cavities diverging so that the cavity B, when the valve is in place, connects the ports, C1 and D. Cavity B1 connects the ports C and D, when the valve, A, is at the end of the stroke. The three small cuts show relation of auxiliary valve to ports.
Fig. 296.