Patent GB-724020-A (GB)
Title: Improvements in or relating to the treatment of articles by vapour deposition in a vacuum
IPC: C23C14/56
Filed: 1952-07-21
Abstract: 724,020. Coating by vapour deposition. VOGT, A. July 21, 1952 [July 23, 1951], No. 18379/52. Class 82 (2). In a process for the treatment by deposition thereon of a solid coating from the vapour phase, of a plurality of articles arranged within a closed chamber at various levels thereof, and there subjected to and held continuously under a vacuum throughout the treatment, the articles are in succession passed transversely through a stream of vapour until all have been treated The substances deposited may consist of dielectrics or metals, or component layers of both, and the articles treated may be, e.g., spectacles, lenses or articles of mica, quartz or synthetic resins. As shown, a vacuum chamber 1 rests on a base plate 4 which has an aperture communicating with a diffusion pump 7, a backing pump 8 producing the necessary preliminary vacuum, and lead-in tubes for the conductors 9 and 10 through which current is passed to heat one or more shuttles of high melting-point materials containing the substance 11 or substances to be vaporized, which may be, e.g., silicon monoxide or magnetite and may be deposited simultaneously or in succession. The articles to be treated are situated on the under sides of a stack of plates 12, which rest on retaining rings 13 mounted on anti-friction bearings, the central hub 14, the height of which is adjustable vertically by two hollow rods 16 and 17, passing through vacuum-tight ducts 19, 20 in the top end wall of an enclosed central column 18. A coolant may be circulated through the rods 16, 17. The column 18 carries a guide pin 22 which enters apertures in the plates 12 carrying articles awaiting treatment, and a depending pin 23 for engaging the said apertures after treatment, there being a gap between the ends of the pins 22 and 23 which permits the plate 12 undergoing treatment to be rotated by a member 24 on a drum 25, which is mounted on a shaft 26 passing through a vacuum-tight seal 31 in the end wall of the column 18, driven through sprockets 34, 35 and a chain, and a gearbox 36, by a motor 37. Each plate 12 has a peripheral aperture 28, these being in vertical register when the plates are arrested by the pins 22 or 23, thus permitting the vapour to reach the plate undergoing treatment, and a further aperture 29 which permits inspection thereof through sight glasses 5 and 6. The rods 16, 17 carrying the hub 14 are mounted on a crosspiece 33 which is subjected to the action of a lever 39, pivoted at 38, and acted upon to lift or lower the plates by a hand-wheel 21, or by a ratchet mechanism (not shown) operated by a push rod 43, actuated by a cam 42 on the shaft 26. In operation, after removal of the chamber 1, the drum 25, the holder 48 carrying the pin 23 and the plates 12 used in the preceding treatment, plates 12, carrying the articles to be treated, are loaded into the apparatus, and the various parts replaced, the lug 24 entering a recess 46 on the uppermost plate. The chamber is now evacuated by the pumps 7 and 8, the evaporation process is started by passing an electric current through the shuttle, then the motor 37 is started, causing the uppermost plate 12 to rotate so that the articles carried thereon are contacted by the vapour rising through the registering apertures 28. When the plate 12 has completed a rotation, the rods 16 and 17 move upwardly by the height of a plate, causing the uppermost plate to be caught and held by the pin 23. The next plate assumes the place thus vacated, and is caused to rotate by the projection 24, and so on until all the plates have been treated. The plates 12 may be replaced by other forms of holders ; the drum 25 may be replaced by radial arms or other gripping means, and a separate hood or the like provided to prevent ingress of foreign matter; and different forms of coupling means may be employed.