362 KINEMATICS OF MACHINERY.
block slider-crank, (C'^P^. It has two turning links, the slide d and the coupler I, and one link which both turns and swings, the block c, so that all the moving links have rotary motions. In the ceaseless attempts at rotary engine design all three have been used as piston in turn. In the first ten of our examples c is the piston ; in the seven next it is d, and in the last three figures I.
Fig. 1, PL XVIII. represents a form of steam-engine used by Ward* in 1821 to drive a paddle steamer, and afterwards by Moulinef (1847), and by Schneider J 1862 for factory purposes.
The chamber and piston are formed respectively from d and c, so that the machine is a direct inversion of that of Fig. 1, PL XIV. The steam distribution is managed by trunnion valves, which can be conveniently arranged in connection with the centre 1. The fly-wheel is placed upon &, which is the piece whose velocity is required to be as uniform as possible.
Fig. 2, PL XVIII. Steam-engine used by S. Morey for a paddle-steamer in 1819, by Cramer, in 1834 as a three cylinder engine J | and again in 1862 by Schneider for driving machine- tools. The difference between this arrangement and the last is that here the link d is the one to which the uniform rotary motion is given. Morey, Ward and Schneider are all Americans ; the idea once sown in their country seems to have extended itself rapidly. These arrangements have the obvious advantage that all their moving parts have rotary motion ; they therefore permit of the use of a number of different constructive forms.
Fig. 3, PL XVIII. Emery's PurnpIT (America). This is a combination of four turning-blocks, and so has for its general formula 4((7gP- L )*. The fixed link a is the chamber, the four blocks c the pistons. Between the latter and the sides of the chamber there is higher pairing. An arrangement of stops, not shown in the figure, prevents either the formation of a vacuum or the con- finement of liquid in the two lower quadrants. The link d is the driving link. In his later machines Emery omits the coupler b, i.e., reduces each chain by that link, and employs instead of it the
- Severin's Abhandlungen, p. 114. Dingler's Journal, vol. ix., p. 291.
t Batailleet Jullien, Machine a Vapeur, 1847, vol. ii., p. 241.
Polytech. Journal, 1862, p. 401.
Severin's A bhandlungen, p. 110.
II Newton, London Journal of Arts, &c. Conjoined series, vol. xx. (1842), p. 454.
U Propagation Indusirielle, vol. iv., 1869, p. 335.
