Fig. 1150. A uniform intermittent rotary motion in opposite directions is given to the bevel-gears A and B by means of the mutilated bevel-gear C.

Fig. 1151. Reciprocating rectilinear motion of the rod C transmits an intermittent circular motion to the wheel A, by means of the pawl B at the end of the vibrating bar D.

Fig. 1152 is another contrivance for registering or counting revolutions. A tappet B, supported on the fixed pivot C, is struck at every revolution of the large wheel (partly represented) by a stud D attached to the said wheel. This causes the end of the tappet next the ratchet-wheel A to be lifted, and to turn the wheel the distance of one tooth. The tappet returns by its own weight to its original position after the stud D has passed, the end being jointed to permit it to pass the teeth of the ratchet-wheel.

Fig. 1153. The vibration of the lever C on the centre or fulcrum A produces a rotary movement of the wheel B, by means of the two pawls, which act alternately. This is almost a continuous movement.

Fig. 1154. A modification of Fig. 1153.

Fig. 1155. Reciprocating rectilinear motion of the rod B produces a nearly continuous rotary movement of the ratchet-faced wheel A, by the pawls attached to the extremities of the vibrating radial arms C C.

Fig. 1156. Rectilinear motion is imparted to the slotted bar A by the vibration of the lever C through the agency of the two hooked pawls, which drop alternately into the teeth of the slotted rack-bar A.

Fig. 1157. Alternate rectilinear motion is given to the rack-rod B by the continuous revolution of the mutilated spur-gear A, the spiral spring C forcing the rod back to its original position on the teeth of the gear A quitting the rack.

Fig. 1158. On motion being given to the two treadles D a nearly continuous motion is imparted, through the vibrating arms B and their attached pawls, to the ratchet-wheel A. A chain or strap attached to each treadle passes over the pulley C, and as one treadle is depressed the other is raised.

Fig. 1159, A nearly continuous rotary motion is given to the wheel D by two ratchet-toothed arcs C, one operating on each side of the ratchet-wheel D. These arcs (only one of which is shown) are fast on the same rock-shaft B, and have their teeth set opposite ways. The rock-shaft is worked by giving a reciprocating rectilinear motion to the rod A. The arcs should have springs applied to them, so that each may be capable of rising to allow its teeth to slide over those of the wheel in moving one way.

Fig. 1160. The double-rack frame B is suspended from the rod A. Continuous rotary motion is given to the cam D. When the shaft of the cam is midway between the two racks, the cam acts upon neither of them; but by raising or lowering the rod A either the lower or upper rack is brought within range of the cam, and the rack-frame moved to the left or right. This movement has been used in connection with the governor of an engine, the rod A being connected with the governor, and the rack-frame with the throttle or regulating valve.

Fig. 1161. Uniform circular motion into reciprocating rectilinear motion, by means of mutilated pinion, which drives alternately the top and bottom rack.

Fig. 1162. Circular motion into alternate rectilinear motion. Motion is transmitted through pulley at the left upon the worm-shaft. Worm slides upon shaft, but is made to turn with it by means of a groove cut in shaft, and a key in hub of worm. Worm is carried by a small traversing frame, which slides upon a horizontal bur of the frame, and the traversing frame also carries the toothed wheel into which the worm gears. One end of a connecting rod is attached to fixed frame at the right and the other end to a wrist secured in toothed wheel. On turning worm-shaft rotary motion is transmitted by worm to wheel, which, as it revolves, is forced by connecting rod to make an alternating traverse motion.

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Fig. 1163. Continuous circular into continuous but much slower rectilinear motion. The worm on the upper shaft, acting on the toothed wheel on the screw-shaft, causes the right- and left-hand screw-threads to move the nuts upon them toward or from each other according to the direction of rotation.

Fig. 1164. Scroll-gears for obtaining a gradually increasing speed.

Fig. 1165. What is called a "mangle-rack." A continuous rotation of the pinion will give a reciprocating motion to the square frame. The pinion-shaft must be free to rise and fall, to pass round the guides at the ends of the rack. This motion may be modified as follows : - If the square frame be fixed, and the pinion be fixed upon a shaft made with a universal joint, the end of the shaft will describe a line, similar to that shown in the drawing, around the rack.

Fig. 1166. A mode of obtaining two different speeds on the same shaft from one driving wheel.

Fig. 1167. A continual rotation of the pinion (obtained through the irregular-shaped gear at the left) gives a variable vibrating movement to the horizontal arm, and a variable reciprocating movement to the rod A.

Fig. 1168. Worm or endless screw and worm-wheel. Used when steadiness or great power is required.

Fig. 1169. Variable circular motion by crown-wheel and pinion. The crown-wheel is placed eccentrically to the shaft, therefore the relative radius changes.