CATALOG OF THE MECHANICAL COLLECTIONS g5 



The model represents a conical plug valve, connected to a valve 

 gear, which gives it two distinct motions. The first motion is a slight 

 one parallel with the axis of the cone and directed toward its larger 

 end ; the other is in a direction tending to rotate the valve. Because 

 the valve and valve seat are conical, the first motion effects a very 

 slight separation of the valve from its seat and permits the rotary 

 motion to be given without friction upon those parts. 



WIEGAND VARIABLE ECCENTRIC, 1857 



U.S.N. M. no. 308659; original patent model; transferred from the United States 

 Patent Office ; not illustrated. 



This model was submitted with the application for the patent 

 issued to S. Lloyd Wiegand, of Philadelphia, Pa., September 29, 

 1857, no. 18311. 



The model represents an eccentric for operating the valves of a 

 steam engine. It is carried on a section of the engine shaft, which 

 is oblique to the axis of the shaft and free to slide along the shaft. 

 The eccentric is held so as not to move along the shaft, but the 

 oblique slide passes through the eccentric disk. The position of the 

 slide on the shaft determines the amount of "throw" that will be 

 given to the eccentric and, correspondingly, the length of stroke of 

 the valve. 



ALLEN CUT-OFF VALVE GEAR, 1857 



U.S.N.M. no. 308657 ; original patent model ; transferred from the United States 

 Patent OflSce; not illustrated. 



This model w^as submitted with the application for the patent 

 issued to Horatio Allen, of New York, N. Y., December 15, 1857, 

 no. 18837. 



The model represents a valve gear in which the steam valve is 

 raised by means of a loose toe on a rock shaft and returned to its 

 seat by lowering or by tripping the loose toe. This particular inven- 

 tion is an improvement on the valve gears of this type patented 

 February 6, 1849, by Horatio Allen and December 10, 1850, by 

 Samuel H. Gilman. It provides a piston or plunger in a chamber 

 containing oil or water connected to the loose toe to control its fall. 



The model shows a vertical valve rod tappet raised and lowered 

 by a loose toe on a rock shaft located below the tappet. The toe is 

 raised by a latch that engages with an arm fixed to the rock shaft so 

 that the motion of the toe is the same as if it were keyed to the shaft. 

 An adjustable disengaging lug is provided that may be set to trip the 

 latch so that the toe will swing freely on the rock shaft and fall, 

 permitting the valve to close. This lug is set by a screw and hand 

 wheel to provide cut-off at any point. Attached to the loose toe is a 

 plunger that operates to force a fluid through an adjustable orifice in 

 a dash pot w^hereby the fall of the loose toe is controlled. 



