Page:The Kinematics of Machinery.djvu/391

 COCHRANJ2, MINARI, STOCKER. 369

connection with rotary engines and pumps, and which the hitherto existing notions of Machine Kinematics have been powerless to prevent.

PL XXI. Fig. 1 shows another creation of the inventive talent of Lord Cochrane,* intended for a rotary steam-engine. It will be seen that this time he has given us a reduced chain. The link c of the arrangement in Fig. 11 is omitted, the mechanism being therefore (O^'P- 1 -)*- c, and the pairing of Fig. 269 is used, which leaves little hope that the joint will be steam-tight.

The same untiring nobleman, not contented with the series of com- binations we have already mentioned, arranged the same mechanism also in the form shown in Fig. 2 of Plate XXI., which was intended for a pump.-)- Here again the chain is reduced b}^ c, but b takes the place of a as the chamber, so that we have (F=t)=c?, b. If we compare the mechanism shown in PL XVII. Fig. 4 with that of the figure before us, we see that, apart from the arrangement of the ports, the one is simply an inversion of the other.

In order to make the matter clearer I add in Fig. 3, PL XXI.. an arrangement of the same mechanism with the link c restored ; it will be seen that it is an inversion of Knott's pump, Fig. 3, PL XVII.

We mentioned in considering PL XX. Fig. 2, a peculiarity connected with the use of multiple turning-block trains, namely, the enlargement and contraction of the space between the revolving pistons. This principle is applied in the mechanism shown in Fig. 4, PL XXI., which is so arranged that the space mentioned alternately almost disappears and becomes a maximum. It is a combination of two chains of the form (C^PJ-)*, with d as piston and a as chamber. This reduction of the space between the pistons to zero is effected by causing them (the two sectors d), to cover a suitable angle. The slide d with couplers and blocks is placed out- side the chamber. Minari,J 1838, applied the chain (OJP- 1 -)* in a three-fold form ; Stocker, 1872, used a double train only, as in our figure both intended their machines as steam-engines. In this case d would be the driving-link, which would be b if the machine

t Propagation Industrielle^ as above. t Propagation Industrielle, vol. iii., 1868, p. 276. g Bdierisches Industrie -und Gcwerbeblatt, 1872, p. 167. K H B
 * Propagation Industrielle, as above,