Section 40.—GEARING, VARIOUS DEVICES IN (not otherwise classed).

[711]. Conical rotatory gear. Applied to reaping machines. See also Pan Screen, [No. 1264].

[712]. Triangular eccentric, used to obtain a pause of one-third revolution at each end of the stroke.

[713]. Face plate worm gear.

[714]. Double rack and pinion gear.

[715]. Double gear wheels.

[Larger plate.]

[716]. Eccentric gearing; the wheel A being fixed on a crank pin in the driving wheel B, drives the dotted gear at a speed proportionate to the diameters of the wheels A and the driven wheel.

[717] & [718]. Forms of epicyclic or planet gear. Several modes of driving these may be employed by fixing one or other of the three wheels, the other two revolving. See Differential Gear, [Section 31].

[719]. Multiple trammel gear. The pinion is half the diameter of the wheel, and makes two revolutions to one of the wheel.

[720]. Trammel crank gear; the crank revolves once to two double strokes of the rod.

[721]. Knight’s noiseless gearing, for two shafts running in opposite directions. Each shaft has two equal cranks at right angles, which are coupled by links to rocking arms, which are also coupled in pairs.

[722]. Eccentric variable speed toothed gear.

[723]. Scroll bevil gear.

[724]. Segment reversing gear, to obtain two speeds in portions of one revolution, and in opposite directions. See Reversing Gear, [Section 74].

[725]. Snail wheel, or scroll ratchet.

[726]. Combined spur and bevil wheel.

[727]. Double screw gear, for steering gear, &c.

[728]. Angular ball-jointed crank motion.

[729]. Crank gearing between two shafts running in the same direction. See [No. 187]. The cranks should be similar to [Nos. 174] or [175].

[730]. Snail worm gear.

[731]. Diagonal engine or pump, with bevil gear revolving motion and three or more cylinders.

[732]. Angle coupling on Dr. Hooke’s principle. See [No. 292].

[733]. Worm and crown gear. Used in chaff machines; useful to obtain a slow feed on two shafts in opposite directions.

[Larger plate.]

[734]. Ball wheel, with limited angular traverse gearing into one or two pinions.

[735]. Scroll and rack.

[736]. Variable speed gear, from an elliptical or other irregular-shaped driving wheel, combined with a tied idle intermediate wheel.

[737]. Spring friction grip wheels.

[738]. Intermittent reversible feed motion. The pinion is of leather, and drives the segment till it runs out of gear; when the machine is reversed it travels an equal distance the opposite way.

Section 41.—GOVERNING AND REGULATING SPEED, POWER, &c.

[739]. Is a device for varying the opening of a main valve (connected to rod A) by the pressure on the small piston, which moves it against the tension of a spring.

[740], [741], [742], & [743]. Types of centrifugal governors, of which numerous varieties are in use.

Pumping engines may be governed by allowing the pressure of water in the rising main to accumulate in a stand pipe or equivalent device until it stops the engine by excess of pressure. To prevent such an engine running away a catch is used, kept open by the pressure of water; when the pressure falls below a certain point the catch is released and closes the throttle valve.

Steam engines may also be safeguarded in the same way by a catch which is released and closes the throttle valve when the governor becomes fully expanded.

[744]. Screw and nut device, to control the travel of any machine, such as a lift, by reversing the belt or throwing out a catch after any specified number of revolutions, the travel being adjusted by the stop nuts.

[745]. The cataract is one of the oldest governing devices. It consists essentially of a vessel which is filled with water by one stroke of the engine, and empties itself through an adjustable orifice during the return stroke, the valve motion being prevented from reversing till the water is all discharged.

[746]. Gas engine governor. Rod A has a reciprocating motion from the engine, and the spur on lever B strikes the end of the gas valve slide when brought in line with it by the motion of the governor, thus supplying gas only when the governor falls to a certain point.

Differential Governor. See [Nos. 556] and [557].