GB606972A - Improvements in the moulding of keys for typewriters or calculating machines from thermoplastic material, having inlays of different colour from the surface of the articles - Google Patents

Abstract

606,972. Moulding keys for typewriters &c. LANDIS & GYR SOC. ANON. Oct. 16, 1945, No. 27048. Convention date, Oct. 28, 1944. [Class 87(ii)] Keys of thermoplastic material, for typewriters or calculating machines, having inlays of a different colour from the body of the keys are moulded in a set of moulds comprising one or two base members and two interchangeable upper members, a central feed passage and radiating feed channels of one of the upper members being larger than those of the other, so that after the body of the keys have been moulded, using the upper member with the smaller feed channels and a base member, and then replacing it by the other upper members, the inlay material may be injected between the old sprue and the walls of the larger feed channels of the second upper member. As shown in Figs. 1 and 3, two base members 1, 11 are used. Plastic material is injected through the feed passage 9 and radiating channels 10 into the mould cavities 3. Interchangeable members 6 having ribs 7 to form hollows in the keys for the inlays are positioned above the cavities 3. When the material has set, the upper member 2 is removed, the moulding remaining in the member 1 due to the tapering stud 8a formed in a recess 8. The moulding is then removed by an injector 4, the stud being partly deformed, and it is then placed in the second base member 11 which is identical with the member 1 except for the recess 12, which is slightly larger than the recess 8, and for feed channels 18 which connect the recess 12 with the feed channels in a second upper member 13. The member 13 has a passage 9a and channels 14 larger than the corresponding passage 9 and channels 10. The inlay material is injected through the channels formed between the old sprue 5a and the channels 14 and is distributed by ribs 16 on members 17 into a moulding space 15 which includes the hollows formed by the ribs 7. At the same time material passes through the channels 18 to form a new stud around the old stud 8a, to allow the upper member 13 to be broken away from the moulding. After ejection by means of an ejector 4a, the surfaces of the keys are turned to remove the surplus inlay material. Specification 566,518 is referred to.