CATALOG OF THE MECHANICAL COLLECTIONS 77 



The two patents relating to this model refer to Patent no. 17423, 

 which is described above under U.S.N.M. no. 308722. 



Tliis model represents a radial arrangement of horizontal water 

 <;ylinders (185390) or air cylinders (190958) the pistons of which 

 act upon a common crank on a short vertical shaft. A horizontal 

 steam engine drives a vertical crankshaft, which is geared at its lower 

 end to the crankshaft of the radial cylinders. A horizontal flywheel 

 is attached to the engine shaft between the crank and the gear. The 

 improvement claimed is that the steam engine may operate rapidly 

 ^nd economically while the pump pistons are worked slowly. For 

 the air pump it is claimed that the arrangement of cylinders will per- 

 mit the pump to be located near and below the main engine cylinder 

 to take water freely from the condenser without the necessity of 

 (extending the engine framing. 



CORLISS VALVE GEAR 

 U.S.N.M. no. 309816; model; gift of Franklin Machine Co.; not Ulustrated. 



This is a finely made, crank-operated bronze model of an early 

 type of Corliss detachable rotary valve gear. It is accompanied by a 

 picture of a large engine installed at the New England Rolling Milld 

 in 1860, on which this type of gear was used. 



The valve stem terminates in a short lever by which the valve is 

 rotated. This lever is permanently connected to a plunger in a closed 

 <?ylinder or dash pot located below the valve. A hook or latch is op- 

 erated up and down in a position so that the hook engages with the 

 lever on its upstroke and rotates the valve to open it. A stiff flat 

 spring holds the hook against the lever, while a bearing pin is so lo- 

 cated that it will force the hook out of engagement with the valve 

 stem lever after the hook has raised it a determined amount. When 

 the lever is freed a spring closes the valve. The dash pot prevents 

 the too rapid closing of the valve. 



CORLISS EXHAUST-VALVE GEAR, 1876 



U.S.N.M. no. 308693 ; original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model was submitted with the application for the two patents 

 issued to George H. Corliss, May 9, 1876, nos. 177059 and 177099. 



The model represents the valve gear of a horizontal cylinder with 

 a separate rotary steam and exhaust valve at each end of the cyl- 

 inder. The valves are driven from one wrist plate, the steam valves 

 through disengaging hooks or catches, which are controlled by the 

 governor, the exhaust valves by a series of permanently connected 

 links designed to effect a quick closing of the exhaust valves. The 

 steam valves are closed by vacuum dash pots instead of by weights or 

 springs as in the earlier Corliss valve gears. 



