Fig. 920. Rotary motion of the bevelled disc cam gives a reciprocating rectilinear motion to the rod bearing on its circumference.

Fig. 921. Rectilinear into rectilinear motion. When the rods A and B are brought together, the rods C and D are thrust farther apart, and the reverse.

Fig. 922. An engine governor. The rise and fall of the balls K are guided by the parabolic curved arms B, on which the anti-friction wheels L run. The rods F, connecting the wheels L with the sleeve, move it up and down the spindle C, D.

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Fig. 923. Continuous rotary motion of the cam gives a reciprocating rectilinear motion to the bar. The cam is of equal diameter in every direction measured across its centre.

Fig. 924. Colt's invention for obtaining the movement of the cylinder of a revolving fire-arm by the act of cocking the hammer. As the hammer is drawn back to cock it, the dog a, attached to the tumbler, acts on the ratchet b, on the back of the cylinder. The dog is held up to the ratchet by a spring c.

Fig. 925. C. R. Otis's safety-stop for the platform of a hoisting apparatus. A are the stationary uprights, and B is the upper part of the platform working between them. The rope a, by which the platform is hoisted, is attached by a pin b and spring c, and the pin is connected by 2 elbow-levers with 2 pawls d, which work in ratchets secured to the uprights A. The weight of the platform and the tension of the rope, keep the pawls out of gear from the ratchets in hoisting or lowering the platform, but, in case of the breakage of rope, the spring c presses down the pin b and the attached ends of the levers, and so presses the pawls into the ratchets and stops the descent of the platform.

Fig. 926. Crank and slotted cross-head, with Clayton's sliding journal-box applied to the crank-wrist. This box consists of 2 taper lining pieces and 2 taper jibs adjustable by screws, which serve at the same time to tighten the box on the wrist, and to set it out to the slot in the cross-head as the box and wrist wear.

Fig. 927. Pickering's governor. The balls are attached to springs, the upper end of each of which is attached to a collar fixed on the spindle, and the lower end to a collar on the sliding sleeve. The springs yield in a proper degree to the centrifugal force of the balls, and raise the sleeve; and as the centrifugal force diminishes, they draw the balls toward the spindle and depress the sleeve.

Fig. 928. A mode of working a windlass. By the alternating motion of the long hand-lever to the right, motion is communicated to the short lever, the end of which is in immediate contact with the rim of the wheel. The short lever has a very limited motion upon a pin, which is fixed in a block of cast iron, which is made with 2 jaws, each having a flange projecting inward in contact with the inner surface of the rim of the wheel. By the upward motion of the outward end of the short lever, the rim of the wheel is jammed between the end of the lever and the flanges of the block, so as to cause friction sufficient to turn the wheel by the further upward movement of the lever. The backward movement of the wheel is prevented by a common ratchet-wheel and pawls; as the short lever is pushed down it frees the wheel and slides freely over it.

Fig. 929. The revolution of the disc causes the lever at the right to vibrate, by the pin moving in the groove in the face of the disc.

Fig. 930. By the revolution of the disc, in which is fixed a pin working in a slot in the upright bar which turns on a centre near the bottom, both ends of the bar are made to traverse, the tooth sector producing alternate rectilinear motion in the horizontal bar at the bottom, and also alternate perpendicular motion of the weight.

Fig. 931. By a vibrating motion of the handle, motion is communicated by the pinion to the racks. This is used in working small air-pumps for scientific experiments.

Fig. 932 represents a feeding apparatus for the bed of a sawing machine. By the revolution of the crank at the lower part of the figure, alternate motion is communicated to the horizontal arm of the bell-crank lever, whose fulcrum is at a, near the top left-hand corner of the figure. By this means, motion is communicated to the catch attached to the vertical arm of the lever, and the said catch communicates motion to the ratchet-wheel, upon the shaft of which is a toothed pinion, working in the rack attached to the side of the carriage. The feed is varied by a screw in the bell-crank lever.