MACHINE FOR COATING PLATES.
In coating plates by machinery, the ap paratus invented by B. J. Edwards, and patented June 5th, 1SS-1, is still used, with only slight modifications. This apparatus is shown in Fig. 147. It consists of a trough dish, into which pour sufficient spirit to well cover the plate. If a half-plate is used with a half-plate dish, about 6 oz. will be required ; while larger dishes will require a proportionate amount. Entire absence of dust is essential, so that the spirit should be carefully filtered before use. It is a good plan to pour the spirit each time after use back to the jar through a funnel, in the neck of which has been loosely placed a small tuft of cotton wool. Where several plates have to be dried in A for holding the emulsion. The trough is silver-plated, and is supported between two uprights, as shown, and in it revolves a roller a carrying around with it a coat ing of the emulsion, which flows into the trough from the tap in the reservoir x fitted above. At c is fixed a movable scraper, which is so arranged as to take off a layer of emulsion from the roller. This scraper is carried by the pivoted frame D. It is made to press against the roller by means of two springs s, and can be placed at any desired angle. Its width must bc: the same as that of the plates to be coated.
The emulsion thus scraped off the roller flows down it on to the glass plate r, the thickness of the coating being controlled by the speed at which the plates travel past. The scraper may be placed at diff erent heights to accommodate glasses of different thickness, and this is effected automatically by two side rollers. A guid ing roller E brings the plate into exact position below the scraper. The plates are moved along below the scraper by means of an endless travelling band F, which is carried by the rollers G. Another endless band L passes around the two rollers G and carries the plates through a cooling chamber M, a tunnel-shaped com partment, open only at each end, which may be supplied with cold air. These bands are so arranged that in travelling from band F to band L the plates are separ ated slightly as shown. This is effected by the band L being made to travel at a slightly greater speed than the band F. Beneath L, or immediately under the plates, is a cold slab N ; o is a metal tray in which the slab rests, which may be filled with ice-water. By a similar ice-tank R, just above the plates, the air in the cham ber M is kept perfectly cool. An ingenious arrangement is shown in the centre of the illustration for