piston knob (pistonnob)

Same as piston, 3. piston-packing (pis'ton-pak"ing), n. 1. Any material used to pack or make tight the space between the perimeter of a piston-head and the interior of the cylinder or-barrel in which it moves. Many different materials have been used for piston-packings, among which are hemp (usually in the form of a braided gasket), either by itself or saturated with tallow or mixtures of various oily or fatty materials, india rubber or compositions of which india-rubber is a principal ingredient, leather, metallic alloys, etc. Piston-packings are usually inserted in a groove or depre ion in the perimeter of the piston-head, and expanded by mechanical compre ion to make a steam-tight, air-tight, watertight, or gas-tight joint. 2. A mechanical device for packing pistons, in which the operation depends more upon the construction than upon the fibrous, plastic, or compre ible properties of the packing-material.-Piston-packing expander, a steel spring in a piston-head serving to expand the packing against the interior of the cylinder; a piston-spring. E. H. Knight. piston-pump (pis'ton-pump), п . A pump consisting of a pump-cylinder or -barrel in which a reciprocating piston works. It is provided with appliances for moving the piston, as a piston-rod or pumprod, and a hand-lever actuating the pump-rod, or the cro head of an engine attached to it; an induction-port or -ports covered with valves which permit a fluid to enter the pump-barrel, but prevent its return; and an eduction port or-ports provided with valves which permit efflux of the fluid from the pump-barrel, but prevent its return. These are the e ential features of piston-pumps. They usually also have induction or suction-pipes, and frequently eduction or discharge-pipes. See pump1 , lift pump , force - pump , plunger - pump , and suction - pump . piston-rod (pis'ton-rod), n. See piston , 1.-Piston-rod packing. (a) A material placed in the stuffing. box of a cylinder to make a steam-tight joint about the piston. (b) The stuffing-box of a piston. The piston of