GB565005A - Improvements in or relating to patterns for casting - Google Patents

Abstract

565,005. Casting. HYDRAULIC BRAKE CO. Jan. 2, 1943, No. 99. Convention date, Dec. 1, 1941. [Class 83 (i)] Patterns; moulding processes.- Matched foundry patterns, for use with a moulding flask, are made from a master model by casting about portions of the model an alloy which will not injure its surface and forming, from these alloy negatives, positives which are non-fusible in use. A wooden, cast or other model 10, of the article it is desired to cast, enlarged to allow for shrinkage of said article if necessary, is partly embedded in clay, dental-plaster or the like support 32, Fig. 5, which is fashioned with a free face to a parting line on the model which will allow a negative 38 cast thereon, and also the support 32, to be drawn without damage. The bottom board 30, on which the support 32 is carried, has locators 36 which form corresponding holes in the negative 38. This may be of " Woods Metal," or of one of the alloys known under the Registered Trade Marks " Cerromatrix," " Cerrobase," and " Cerrobend," which will harden without alteration in volume. A negative 44, Fig. 7, of the other side of the model 10, supported by the negative 38, is then cast similarly and finally positives 56, Fig. 9, and 58, Fig. 11, of sand, gypsum, &c., are made from these two negatives without the model. These positives 56, 58, Fig. 14, are mounted on separate plates or on opposite sides of one plate 60, dowel pins 68, 70 being provided to locate the flasks F. To facilitate correct mounting of the positives they are first aligned relatively by means of their projections 36 and recesses 136 and their edges are finished off while so held, these edges being then used to align the positives on their plate or plates. When a stripper plate is required to facilitate long drawing, e.g. as in the formation of patterns for making aircraft-engine cylinders with closely spaced fins, a negative 138, Fig. 19, is formed from a half model 110, Fig. 18, mounted directly on a bottom board 130, embedding material 32 not being required. The half model is withdrawn and a stripper plate 121, Figs. 21, 23, is applied to the negative 138. From this a positive 156 is made, it is machined flush with the stripper plate 121, secured to a guided plate 139 and withdrawn by means of the plate 139 from the negative 138 and plate 121. This is replaced on the pattern 156 for use in making the sand moulds. If cores are required, the necessary core prints may be provided on the model. To avoid any risk of the cast negative adhering to the model, or the embedding material 32 &c., a parting substance may be used.