Page:The Kinematics of Machinery.djvu/385

 COCURANE, BE ALE, DA VIES. 363

circular groove shown in the figure to pair with the pin 2 of the link c. He has used the mechanism for several purposes, among others for a water meter.

Fig. 4, PL XVIII. Steam-engine designed by Lord Cochrane,* 1834. Here again the block c is the piston, this time, however, the turning link b is made the chamber. The steam distribution takes place through the centre 1 by means of a passage (shown dotted) in the piston c. There is a higher pairing between the link d and the chamber.

Fig. 1, PI. XIX., represents the well known gas exhauster of Beale.f It consists of two turning-blocks, having d as their driving- link. Its special formula is therefore 2(C7J P- 1 -)^. The fixed link a is the chamber, and c the piston ; the coupler I appears as a circular sector (see 71, Fig. 240, &c.) which works in a corresponding groove, 2 in a, and is made of sufficient length to prevent any leakage of gas through the groove.

Fig. 2, PL XIX. Eotary steam-engine patented by DaviesJ in England in 1867. There are here three mechanisms of the form (OgP- 1 -)* united, c is the piston and driving-link, a the chamber. The coupler has become a cylindrical bar flattened upon one side, the flat side being simply a portion of the cylinder 2 which is con- axial with the chamber a, it corresponds, that is, to the crank-pin in the mechanism (C^P-^. In consequence of the incomplete form in which the pair 2 is thus used the coupler is not fully constrained. For its closure Davies used a circular groove (dotted in the figure) in which a pin connected with the block c can work, he employs a higher pairing, that is, between c and a. This closure, however, is not exact, for if the projections upon c are cylindrical their envelope in a, that is, the groove, will not be circular, or if the groove be made circular the projections should be portions of cylinders con- axial with 3.

Fig. 3, PL XIX., shows a very old rotary pump, that of


 * Propagation Industrielle, vol. iii., 1868, p. 180.

t Clegg, Manufacture of Coal Gas, 5th Ed. 1868, p. 180, Schilling Gas-fdbrika- tion, 1866, p. 204. It will be noticed that the block c is in two pieces, which overlap each other in the middle of the drum d. The two pieces are connected separately to the two sectors b, shaded in the figure. A later form of Beale's exhauster is illustrated in The Engineer, May, 27, 1870, p. 329.

Propagation Industrielle, vol. iv., 1869, p. 276.