GB1253188A - - Google Patents

Abstract

1,253,188. Sheet forming. R. SCHEU. 28 May, 1970 [10 July, 1969; 13 Oct., 1969], No. 25870/70. Heading B5A. [Also in Division A5] Moulds, for use in casting dental crowns, stump caps or the like from metal, are made by filling a vessel 1 having a radially slotted rim 2 with a kneadable material 8, for example an asbestos dough, forming the material protruding above the rim into a conical configuration, partially embedding a tooth model 9 therein, locating the vessel by means of its rim upon an apertured support 4, provided with through holes in the area contacted by the rim, locating the support upon a sheetforming machine and finally blowing or sucking foil 20 into intimate contact with the protruding part of the model. The surface of the conical part of the material 8 is grooved, the grooves being aligned with the radial slots in the rim and the slots in the rim themselves cooperating with the through holes in the support. In this way complete evacuation of the air between the model and the foil is ensured and wrinkles in the drawn foil avoided. In a second embodiment (see Figs. 6 and 7, not shown), a plurality of vessels are carried by a single support and the regions of the support between the vessels may be upraised so as to initially support the sheet against sagging, which sagging causes wrinkling. In a third embodiment, see Fig. 8, the support comprises a lower vessel receiving half 12 and an upper sheet supporting half 16 mounted upon the lower half by springs 13. In use, pressure is applied to the sheet, the upper half is gradually forced downward to allow the sheet to be applied in a wrinklefree manner over the models. Apertures 14 in the sheet are chamfered at 15 to aid application of the sheet to models.