66 BULLETIN 173, U. S. NATIONAL MUSEUM 



WOODBURY VALVE GEAR, 1859 



U.S.N.M. no. 308644 ; original patent model ; transferred from the United States 

 Patent Office; not Illustrated. 



This model was submitted with the application for the patent issued 

 to D. A. Woodbury, of Rochester, N. Y., April 19, 1859, no. 23737. 



The model represents two rotary main steam valves permanently 

 connected to and operated with a regular movement by an eccentric 

 on the crankshaft. Between each steam valve and the steam chest is 

 a rotary cut-off valve operated by the same eccentric but fitted with a 

 sliding link by which the position of the cut-off valve relative to the 

 eccentric position may be varied without disengaging the valve gear 

 or stopping the engine. This link and with it the time of cut-off may 

 be changed by hand or by the operation of an engine governor. 



FRANCIS B. STEVENS CUT-OFF, 1861 

 Plate 17, Figuke 1 



U.S.N.M. no. 308644 ; original patent model ; transferred from the United States 

 Patent Office ; photograph no. 846A. 



This model was submitted with the application for the patent issued 

 to Francis B. Stevens, December 3, 1861, no. 33855. 



The valve gear represented is an improvement of the Robert L. 

 and Francis B. Stevens valve motion, which was patented January 

 25, 1841. It involves the introduction of adjustable hinged pieces on 

 the tops of the "long toe" tappets that operate the valves for the 

 purpose of rapidly opening the exhaust valves and for varying the 

 point at which the steam valves will be closed. 



The valve gear consists of a main rock shaft to which are keyed 

 four long, curved tappets each of which engages with a shoe or fol- 

 lower on a valve lift rod, which it raises and lowers as the rock shaft 

 is worked with a vibratory motion by an eccentric on the engine 

 crankshaft. The two tappets that work the lift rods of the exhaust 

 valves are the same length and attached to the shaft at the same angle 

 as those that operate the steam inlet valves, but the exhaust valves are 

 prevented from closing too soon and the steam valves are caused to 

 close whenever desired by the combination of hinged faces on the 

 tappets and a second hollow rock shaft fitted with lugs or small cams, 

 which raise the hinged pieces and change the movement of the fol- 

 lowers on the lift rods. The hinged pieces on the tappets are hinged 

 at the toes of the tappets and are lifted from the heels of the tappets 

 by the lugs on the hollow rock shaft, placed over the main rock shaft 

 and worked by another eccentric, which in the earlier Stevens gear 

 works the exhaust valves. 



