Model cataract governor applied to Cornish pumping engine

Model of Cataract Governor applied to Cornish Pumping Engine

This shows the hydraulic governor used for tripping the valve gear of a Cornish pumping engine, and by which the number of strokes per minute can be adjusted to the work to be done, owing to the alteration it permits in the interval of rest at the completion of each double stroke. In many engines, however, there are two cataract governors, so that there is a period of rest at the end of each stroke during which the pump valves return to their seats. The arrangement consists of a weighted plunger in a vertical cylinder arranged in a water cistern, from which, when the plunger is raised, water enters the cylinder through a non-return valve; upon the plunger being released it descends at a rate determined by the amount by which a valve at the side of the cylinder is opened. The plunger is raised by a lever moved by a tappet on the plug rod of the engine valve gear, and the subsequent descent of the plunger lifts the catches, and so releases the valve that controls the next stroke of the engine.