Fig. 756. A method of working a reciprocating pump by rotary motion. A rope carrying the pump-rod is attached to the wheel A, which runs loosely upon the shaft. The shaft carries a cam C, and has a continuous rotary motion. At every revolution the cam seizes the hooked catch B, attached to the wheel, and drags it round, together with the wheel, and raises the rope until, on the extremity of the catch striking the stationary stop above, the catch is released, and the wheel is returned by the weight of the pump-bucket.

Fig. 757. Continuous rotary converted into intermittent rotary motion. The discwheel B, carrying the stops C, D, turns on a centre eccentric to the cam A. On continuous rotary motion being given to the cam A, intermittent rotary motion is imparted to the wheel B, the stops free themselves from the offset of the cam at every half revolution, the wheel B remaining at rest until the cam has completed its revolution, when the same motion is repeated.

Fig. 758. A contrivance for a self-reversing motion. The bevel-gear between the gears B and C is the driver. The gears B and C run loose upon the shaft, consequently motion is only communicated when one or other of them is engaged with the clutch-box D, which slides on a feather on the shaft, and is shown in gear with C. The wheel E at the right is driven by bevel-gearing from the shaft on which the gears B, C, and clutch are placed, and is about to strike the bell-crank G, and produce such a movement thereof as will cause the connecting rod to carry the weighted lever F beyond a perpendicular position, when the said lever will fall over suddenly to the left, and carry the clutch into gear with B, thereby reversing the motion of the shaft until the stud in the wheel E, coming round in the contrary direction, brings the weighted lever back past the perpendicular position, and again causes it to reverse the motion.

Fig. 759. An eccentric generally used on the crank-shaft for communicating the reciprocating rectilinear motion to the valves of steam engines, and sometimes used for pumping.

Fig. 760. A modification of the above; an elongated yoke being substituted for the circular strap to obviate the necessity for any vibrating motion of the rod, which works in fixed guides.

Fig. 761. Triangular eccentric, giving an intermittent reciprocating rectilinear motion, used in France for the valve-motion of steam engines.

Fig. 762. Ordinary crank-motion.

Fig. 763. Crank-motion, with the crank-wrist working in a slotted yoke, thereby dispensing with the oscillating connecting-rod or pitman.

Fig. 764. Variable crank, 2 circular plates revolving on the same centre. In one a spiral groove is cut; in the other a series of slots radiating from the centre. On turning one of these plates around its centre, the bolt shown near the bottom of the figure, and which passes through the spiral groove and radial slots, is caused to move toward or from the centre of the plates.

Fig. 765. On rotating the upright shaft, reciprocating rectilinear motion is imparted by the oblique disc to the upright rod resting upon its surface.

Fig. 766. A heart-cam. Uniform traversing motion is imparted to the horizontal bar by the rotation of the heart-shaped cam. The dotted lines show the mode of striking out the curve of the cam. The length of traverse is divided into any number of parts; and from the centre a series of concentric circles are described through these points. The outside circle is then divided into double the number of these divisions, and lines drawn to the centre. The curve is then drawn through the intersections of the concentric circles and the radiating lines.

Mechanical Movements Part 2 761Mechanical Movements Part 2 762Mechanical Movements Part 2 763Mechanical Movements Part 2 764Mechanical Movements Part 2 765Mechanical Movements Part 2 766Mechanical Movements Part 2 767Mechanical Movements Part 2 768Mechanical Movements Part 2 769Mechanical Movements Part 2 770Mechanical Movements Part 2 771Mechanical Movements Part 2 772Mechanical Movements Part 2 773Mechanical Movements Part 2 774Mechanical Movements Part 2 775Mechanical Movements Part 2 776Mechanical Movements Part 2 777Mechanical Movements Part 2 778Mechanical Movements Part 2 779Mechanical Movements Part 2 780Mechanical Movements Part 2 781Mechanical Movements Part 2 782Mechanical Movements Part 2 783Fig. 767. This is a heart cam. similar to Fig. 766. except that it is grooved.

Fig. 767. This is a heart-cam. similar to Fig. 766. except that it is grooved.

Pig. 768. Irregular vibrating motion is produced by the rotation of the circular disc, in which is fixed a crank-pin. working in an endless groove, cut in the vibrating arm.

Fig. 709. Spiral guide attached to the face of a disc; used for the feed-motion of a drilling machine.

Fig. 770. Quick return crank-motion, applicable to shaping machines.

Fig. 771. Rectilinear motion of horizontal bar. by means of vibrating slotted bar hung from the top.

Fig. 772. Common screw bolt and nut; rectilinear motion obtained from circular motion.

Figs. 773, 777. Uniform reciprocating rectilinear motion, produced by rotary motion of grooved cams.