Section 79.—SLIDE AND OTHER VALVE GEAR.
(See also [p. 172].)
[2462]. Cut-off gear. Two cut-off valves similar to [No. 1456], regulated by an external hand wheel forming the valve spindle guide bush.
[2463]. Duplex motion for a valve, to operate it by either rod, using the other as a fulcrum.
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[2464]. Valve gear, with single eccentric, and variable travel, adjustable by hand wheel. The eccentric drives a block to and fro in a slot, the angle of which in respect of the slide valve centre line is variable by a rocking motion controlled by a hand wheel.
[2465]. Newall’s high speed engine, single-acting. In this engine the connecting rod trunk centre and the piston are made to distribute the steam as shown.
[2466]. Reversing movement for a valve, where the power will only move the valve to the half stroke or mid position, as in a slide valve hydraulic engine (see [No. 1026]), the rolling weight then completes the movement (see also [No. 1740]).
[2467]. Automatic or governor cut-off gear. The governor operates the sleeve, which has a screw movement on the pin fixed to the crank shaft; a parallel feather on the sleeve revolves the cut-off eccentric, and varies the travel of the cut-off valve. The slide valves are of the form of [No. 1456].
[2468]. Eccentric motion to operate two slide valves.
[2469]. Crank shaft governor. The centrifugal gear acts on an outside crank to which the eccentric rod is attached, instead of a sheave and strap. A spring is applied to return the crank to full gear.
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[2470]. Single eccentric adjustable cut off for a “Fink” link gear; plain D valve gives equal distribution of steam at any cut-off; the travel of the valve is regulated by the hand wheel.
[2471]. Cam-bar movement for operating two valves used for hydraulic starting valves.
[2472]. Crank shaft governor cut-off gear. Two hinged centrifugal weights are coupled by links to the cut-off eccentric sheave, and returned to the full open position by springs.
[2473]. Joy’s locomotive valve gear operated by the connecting rod; the rod A is connected to the starting lever to reverse, vary, or stop the distribution of steam by the slide valve, as in the ordinary link motion.
[2474]. Lever and T crosshead to open a valve by either motion of the lever to right or left. See also [No. 2463].
[2475]. Crank shaft governor (Prof. Sweet’s), cut-off gear to vary the throw of a cut-off eccentric.
[2476]. Reversing link motion, with single eccentric; the slot link is hinged to the reversing lever.
[2477]. Sleeve and eccentric motion for governor cut-off. The inner (longest) sleeve has a longitudinal movement from the governor along a straight feather groove in the shaft, and has a spiral groove in its periphery into which projects a pin or feather on the eccentric sleeve, so that the longitudinal motion of the inner sleeve revolves the eccentric and alters the travel of the cut-off slide.
[2478]. The Walschaerts valve gear, one eccentric. The slotted link is hung at its centre to a fixed hinge pin, and the reversing gear shifts the link block up or down the slot link.
Slide valves may be worked by rack and pinion on the back or side flanges of the valve, or by a screw and nut; the nut being let into the body of the valve in a recess.