Corliss Steam Engine - Corliss Engine Mechanisms

Corliss Engine Mechanisms

Corliss engines have four valves for each cylinder, with steam and exhaust valves located at each end. Corliss engines incorporate distinct refinements in both the valves themselves and in the valve gear, that is, the system of linkages that operate the valves.

The use of separate valves for admission and exhaust means that neither the valves nor the steam passages between cylinders and valves need to change temperature during the power and exhaust cycle, and it means that the timing of the admission and exhaust valves can be independently controlled. In contrast, conventional steam engines have a slide valve or piston valve that alternately feeds and exhausts through passages to each end of the cylinder. These passages are exposed to wide temperature swings during engine operation, and there are high temperature gradients within the valve mechanism itself.

Clark (1891) commented that the Corliss gear 'is essentially a combination of elements previously known and used separately, affecting the cylinder and the valve-gear'. The origins of the Corliss gear with regard to previous steam valve gear was traced by Inglis (1868).