Patent GB-165879-A (GB)
Title: Improvements in or relating to the manufacture of dental rubber plates, and to apparatus therefor
IPC: A61C13/00
Filed: 1919-12-31
Abstract: 165,879. Joannides, C. Dec. 31, 1919. Teeth, artificial.-Relates to apparatus for the production of vulcanite, celluloid, or like dentures of the type in which the plastic material is forcibly injected into a dental flask whilst the latter is under stem pressure in a boiler and comprises, inter alia, the provision of a flask adapted to contain a one-piece mould and formed with inlet and outlet openings corresponding with those of the flask, and of means whereby the following operations may be carried out with the flask within the boiler under steam pressure and without opening the boiler or allowing escape of steam, namely-forcibly scouring out the wax model by steam or hot water, injecting the rubber or other plastic material by means of a cylinder and piston, controlling and indicating the filling of the flask from outside the boiler, removing the injector cylinder from the apparatus, closing the inlet and outlet openings of the flask, and, if desired, increasing the temperature so as to effect vulcanization of the denture. Pink rubber to form the gum portion of the denture may be applied in strip form to the teeth and wax model before flasking, the base rubber only being injected by means of the apparatus described. In the form shown in Figs. 1, 2, and 3, the flask comprises a D-shaped casing a having a removable base a<x>, and a detachable cover a' having a flange a<2> extending downwards on one side of the flask and held in place by screw-hooks a<7> passing through projections a<9> on the body of the flask which fit into slots in the edge of the cover. The flask is provided with an inlet a<3> and an outlet a<4> each controlled by a plug valve a<5> adapted to be closed when the flask is removed from the boiler for vulcanization or provided with means to operate them from the outside whilst the flask is under pressure in the boiler b. The plug valves a<5> may, however, be omitted. The boiler inlet is fitted with an injection cylinder f and a surrounding casing f<4> provided with concentric nozzles f<3>, f<5> each adapted to make close contact with the inlet to the flask. A spring f<9> surrounding the casing f<4> holds the outlet a<4> of the flask in contact with the tubular outlet plug g at the opposite side of the boiler so that if the plug g be slacked back the flask is moved away from the nozzles f<3>, f<5> and steam or hot water from the boiler enters the flask and forcibly scours out through the plug g the wax of the model and of the wires or rods connecting the model to the inlet and outlet openings of the flask. On again screwing up the plug g the flask inlet a' is brought into contact with the nozzle f<3> and base rubber may be forced into the mould from the cylinder f by operation of the screw plunger f<2> working in a pivoted yoke f<7>. The piston f<1> is free to turn on the plunger f<2>. A plug e in the boiler outlet g works through an adjustable stuffing-box e<2> and serves, by movement from its innermost position to that shown, to indicate when the mould is full and, by its resistance, to control the pressure under which the mould is charged. During vulcanization, the plug e is held in its innermost position by a set-screw or otherwise so as to close the outlet a<4> of the flask. When vulcanization is to take place in the same boiler b, the charging cylinder f is replaced by a screw plug; escape of steam being prevented during this operation by the casing f<4> the nozzle f<5> of which makes close contact with the flask. The boiler is fitted with an internal strip b<5> to assist in positioning the flask and with a safetyvalve. The lid b<1> carrying a packing-ring b<4> is hinged to the boiler at c and is secured by a loop d hinged to the lid at d<1> and carrying a cam lever d<3> bearing against a screw pin b<2> adjustable in a flange on the body of the boiler. The hinge-pin c works in slots c<2> in a bracket on the boiler casing and is adjustable therein by means of a screw c'. In the modification shown in Fig. 4, the charging cylinder f and outlet plug g are carried by the lid of the boiler and communicate with apertures a<3>, a<4> in the lid a<1> of the flask which slides in dovetail grooves in the body of the flask. The outlet q is integral with the lid of the boiler and carries an adjustable packing-ring g<5>. The wax wires h forming the inlet and outlet passages of the plaster mould are secured to a metal strip h<1> laid on the plaster and formed with holes registering with those in the lid a<1>. An indicator and control plug e similar to that shown in Figs. 1 and 2 may be held in its innermost position bv a screw e<8> engaging a curved slot e<7>. In a further modification, otherwise similar to that shown in Fig. 4, the outlet arrangements are similar to those shown in Figs. 1 and 2, and the lid of the flask, which is held in position by the pressure of the. inlet and outlet nozzles, may be guided into position by pins, the dovetail grooves being dispensed with. In any of the modifications the cylinder plunger may be operated by a lever in place of a screw, and thermometers may be laid in grooves in the lid of the boiler. The flask may be constructed for two or more cases arranged in series or parallel between the single inlet and outlet to be treated simultaneouslv. Specification 161,507 is referred to. According to one Provisional Specification, the apparatus may be provided with two or more charging cylinders arranged in the cover or round the casing of the boiler.