The eccentric in a special relation to the shaft and the engine crank
To compensate for the lap always formed on plain side valves, the slot is not formed across the center s of the eccentric, but is placed across the center t of the crank shaft e, away from the center a distance equal to the lap on one end of the valve, so that the eccentric, when in its central position, will move the valve just enough to compensate for the lap, while any change of position in the eccentric will cause the steam-ports to be opened and steam to be supplied to the piston during a part of the stroke corresponding to the extent of the eccentric's displacement from its central position.
To shift the eccentric while in motion, I employ a diagonally-grooved traveler, k, or key with inclined grooves 1 form, ed in its top, the key being fitted to the groove m or seat in the shaft e, and passing through suitable notches n, cut opposite the seat in the collars b and c. One side of the slot h, opposite the seat m, is formed with inclined teeth o, which fit, the groove's 1 in the traveler k, and any longitudinal movement of the traveler therefore causes a transverse movement of the eccentric between the collars b and c, any transverse movement of the traveler being prevented by the sides of seat m and by its fitting the notches in collars b and c.
A clutch ring, p, is fitted loosely to the shaft e, and secured by a screw or pin, q, to the end of the traveler, which projects from the collars b,c, and a groove, r, formed in the periphery of the ring, furnishes the means to move the traveler when the shaft e is in motion, as is usual with all revolving clutches.
The engine has a seven eight inch bore, 13/8 stroke. The fly wheel is 41/2 in diameter and 7/8' face. The crank shaft is one half inch in the bearing and nine sixteenth inch between the bearings. The governor is a dummy. The base is 9 inches long and 6 inches wide. He operated the engine on compressed air for demonstrating.
The Pipestone is interesting itself. It can be worked the same as iron and takes a high polish. It is kind of dark maroon color
By this construction the engine can be reversed without the use of any parts extraneous to the eccentric and the few fittings described, and the operation of the engine and its valve is equally per-feet in whichever direction it revolves, while the facility with which the stroke of the eccentric can be varied affords the most convenient means of changing the cut off point of the valve and adjusting- the supply of steam exactly to work the engine has to perform. This is especially desirable when the speed has to be greatly varied, as in the starting, stopping, and backing of steam vessels, or when the load upon the engine is frequently changed, as in hoisting, towing', etc.
It is evident that the operation of ray grooved traveler would be the same, whatever means are employed to afford the eccentric a transverse movement on the shaft, and as various devices, such as dovetailed and rectangular slides, are already in use for such purposes, I do not limit myself to the exclusive use of the ribs f and grooves g for that purpose; but
I claim the traveler and eccentric in the following manner:
1. The shifting- eccentric a, provided with toothed slot h, and applied on shaft e, between fixed collar b and adjustable collar c, so that its center s is distant from the center t of said shaft an amount sufficient to compensate equally for the lap of the slide valve, whether running the engine backward or forward, in combination with the rectilinear adjustable grooved traveler k and the clutch ring p, substantially as described.
2. Eccentric a, combined with the ad jus table collar c, fixed collar to, constructed and applied on shaft e substantially as described, and having combined there, with the traveler k, as set forth, and for the purpose described.
In testimony that I claim the foregoing I have hereto set my hand this 18th day of May, 1879, in presence of two witnesses.
William L,. Fish,
Thos. S. Crane.