Patent GB-784702-A (GB)
Title: Improvements in or relating to moulded or cast products and the making of moulds therefor
Inventor: DAVIS FREDERICK LEWIS
IPC: B22C9/04
Filed: 1954-11-25
Abstract: A mould is made by forming a thin flexible envelope having the shape of the desired mould cavity, filling the envelope with an easily-removable filling material, applying plaster or other material to the exterior of the envelope to form the mould, and removing the filling material with or without the envelope, to leave a cavity in the mould.  In a modified method of making the mould the filling material has a low melting-point and is poured into the envelope in liquid condition and allowed to solidify, the envelope than being stripped off before the plaster &c. is applied and the material being melted out of the plaster &c. mould.  The articles that are moulded or cast in the plaster &c. moulds may be resin or metal formers for making gloves by dipping.  Such a former having a roughened surface, may be produced as follows:  Method A.  (1) A rubber glove having its external surface roughened is turned inside out and filled with a fine powder.  (2) A plaster mould is formed around the filled glove, preferably in three or more pieces so as to be readily removable. (3) The powder is removed from the glove, which is left in the mould. (4) Thermosetting material such as liquid ureaformaldehyde resin is poured into the glovelined mould cavity and hardened to constitute the former.  (5) The mould is parted and the glove is stripped from the former.  This former has a roughened surface, and if it is dipped into latex to form a glove, the glove may be turned inside out to present a glove having the roughened external surface of the glove that was originally used to form the mould.  Method B.  As in Method A, except that neither the original glove nor the final glove need be turned inside out.  Method C.  (1) A divided plaster mould is produced as in Method A, but with the glove having its roughened side outwards.  (2) The glove-lined cavity is filled with wax, which is allowed to solidify.  (3) The wax-filled glove is removed from the plaster mould and a second, undivided plaster mould is formed therearound.  (4) The wax is melted out of the glove, the glove is removed from the mould and a metal former is cast in the mould. Method D.  (1) A glove having a roughened external surface is turned inside out and filled with wax.  (2) The glove is stripped off the wax and a plaster mould is formed around the wax.  (3) The wax is melted out of the mould and a metal former cast in the mould.  Method E.  (1) A glove having a roughened external surface is turned inside out and filled with powder or easily melted material.  (2) A mould is made by building up a stiff rubber envelope on the filled glove and removing the filling.  (3) Thermoplastic material is poured into the mould to constitute a former.  In some of the methods the former has the external dimensions of the original glove, so that a glove made by dipping from that former will be slightly larger than the original glove, and for this reason the original glove may be slightly smaller than the gloves to be finally produced.  Specification 784,703 is referred to.