Chapter CXLV: 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.

=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.

=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.