GB562183A - Improvements in or relating to methods of and apparatus for making artificial dentures and like dental articles - Google Patents

Abstract

562,183. Electric heating. WOODHAM, C. H., and REMY, M. W. Nov. 23, 1942, Nos. 16576/42, 18277/42 and 4936/43. [Class 39 (iii)] [Also in Groups V, XXX and XXXII] A dental flask or other two-part mould is closed by automatically-applied graduallyincreasing pressure, and is opened by effecting relative movement without tilting between each part of the flask and its contents. Fig. 1 shows one form of pressure-applying means comprising a vessel 32 which is gradually filled with water, mercury, sand, &c. from a vessel 42. The weight of the vessel 32, acting through cable 33 and levers 36, 30 operates a hydraulic ram 25 to raise the plunger 26 thereof and press a column of four flasks, Fig. 6, upwardly against a stationary head 22. Lever 30 is initially hand-operated to engage plunger 26 with a plate 24 which supports the flasks, and is later coupled to lever 36 by a sleeve 38. During pressing, the flasks are disposed within an openwork cage 17 having a base 16, and the cage-flask assembly is immersed in hot water (e.g. to polymerize methyl-methacrylate monomer) in a vessel 14 heated by an electric immersion heater. The vessel 14 rests on the plate 24 and is centred thereon by a spigot 28 (on the plunger 26) which enters a recess 29 in the base of the vessel. When the lever 36 has moved counterclockwise from the chain-line position to line A, it is returned by hand to the chain-line position, and another stroke is given to the ram, and so on. After moulding has been completed, the vessel 14 is emptied of hot water and filled with cold water. Subsequently the cold water is drained off, the pressure is removed, the cage of flasks is taken out of the vessel, and the flasks are removed from the cage. In a modified construction, Figs. 13-16 (not shown), (a) the head 22 may tilt to allow for constructional inaccuracies in the flasks, (b) the lever 36 is of the second order, is adjustable in length, is horizontally disposed, and has spaced holes for the attachment of the water vessel, whereby the leverage may be 'varied, and (c) a dashpot, Fig. 16, is provided to obviate shocks to the flasks. This dashpot comprises a spring-urged disc 68 covering passages 67 in a piston 66, return passages 69, and a needle valve 70. Opening a flask.-The lower part of the flask has lugs 19 received between and projecting above lugs 20 on the upper part. Each part has a central hole 48. The plate 24 is raised until sleeves 13 on pillars 12, Fig. 9, abut plate 11, and locked by screws 50. The flask is held between plunger 26 and plate 24, and plunger 26 is raised by operation of hand-lever 30, whereupon spigot 28 enters hole 48, engages plate 49 in the flask, and pushes the plaster and upper part away from the lower part (the lower part being held down by engagement of lugs 19 with plates 46 depending from plate 24). The lower part is removed, the flask turned upside down, and the operation repeated.