Air Pump valve, Flexible Type, mounted on board

Air Pump valve, Flexible Type, mounted on board

As mineral oil has a solvent action on india-rubber, its introduction has led to the disuse of that material (see No. 261) for air pump valves. Flexible metal clacks held by set screws along one edge were introduced in 1848 by Edward Humphrys, but had a tendency to break along the line of flexure. This is avoided by the use of the curved guard shown which at the same time holds the clack along a diameter as patented in 1878 by Mr. J. G. Kinghorn and Mr. W. J. Coe. The clack is of copper or phosphor-bronze sheet, often elliptical in shape, as shown, and rests on a suitable grating. In the other form of valve shown, known as the " Multiplex," there are several thin discs of the same metal of decreasing diameters loose on a central stud and lifting against a flat guard. Each disc except the topmost one has some small holes through it and acts as a seating for the one above it. They close on a grating successively and independently, so reducing the shock.