DEQRAND, COCHRANE, COOK. 381
d as chamber and piston respectively, (F=t) = d, c, but fixed the piston and allowed the chamber to oscillate.
Degrand formed the piston c as a sector of a so-called cylindric ring ("globoid ring")* which worked through two stuffing-boxes in the chamber d, as in Fig. 3.f The construction of such a machine prevents obvious difficulties.
Fig. 4, PI. XXY. represents another rotary steam-engine of Lord Cochrane's.J The chain is here used quite differently, the crank a is made the piston and d the chamber. A doubled mechanism is used in order to prevent the steam passing away at wrong times. The coupler b has become a gun-metal packing piece, and the pins 2 (the crank pin) and 3 are not closed kinematically but only by the steam pressure or by some external load. The lever c forms a dia- phragm swinging in the chamber. On account of the force-closure of
b the formula will be 2 -I ( 6^) d - - [ , and we have also ( F) = a, d.
It will be remembered that the crank a has to work steam-tight both against the sides and the periphery of the chamber. The details of the packing are omitted in our figure.
Lord Cochrane has also used this train reduced, as in the case of Fig. 3. PL XX., the arrangement he adopted is shown in Fig. 1, PI. XXVI. Three mechanisms are here combined ; the coupler b is omitted, the lever c itself being held in contact with a by force- closure. The steam and exhaust ports are formed in the piston, and made to communicate with passages and openings in the shaft 1.
Cooke used the mechanism ( C^) d in the first place as a steam- engine || (1868) ; making a the piston, d the chamber, and forming c as a curved block sliding in and out through the wall of the chamber and having its end force-closed against the piston a, it became therefore ( C^) d b. Afterwards, however, he employed it as a blower in the form shown in Fig. 2, PI. XXVI.If The chain
- Gf. Berliner Verhandlungen, 1872, p. 248, note 3.
t Propagation Industrielle, vol. iii., 1868, p. 245. The French patent is dated 1837.
t Bataille et Jullien, Machines d Vapeur, vol. i., 1847, p. 445; Repertory of Patent Inventions. Enlarged series, vol. ii., 1843, p. 193.
Propagation Indmtrielle, vol. iii., 1868, p. 182. The patent dates from 1831.
|| Propagation Industrielle, vol. iv., 1869, p. 337.
f Proc. Inst. C.E., November, 1875 ; Engineering, vol. viii. (1869) p. 269.
