wrist-plate

Century Dictionary and Cyclopedia

1. n. A plate which oscillates on a central pivot, and from the face of which project one or more crank-pins or -wrists for the connection of rods or pitmans.
2. n. Specifically, a plate used in some kinds of automatic cut-off engines. It has a reciprocating rotary motion on a central pivot, and is actuated through a limited arc by the rod of an eccentric on the crank-shaft of the engine. From its face project four crank-wrists, which give it its name. Two of these wrists are respectively connected with rods that actuate the rocker-arms of two separate oscillating plug-valves, for introducing steam into the cylinder on opposite sides of the piston alternately. The other two wrists are similarly connected to independently operating exhaust-valves.