GB508189A - Improvements in tight watch cases with unbreakable glasses and process of their manufacture - Google Patents

Abstract

508,189. Moulding watch glasses. MARTI, F. Dec. 9, 1938, Nos. 36001 and 36002. Convention dates, Dec. 29, 1937, and July 16, 1938. [Class 87 (ii)] [Also in Group XVIII] An unbreakable crystal 5 is permanently fixed to the part 4 of the watch case adapted to carry it by warming the crystal and pressing it into position. In Fig. 1, the crystal 5 is attached to the movement ring 4 with back 3 inside a separate outer case 1, 2. The preheated ring 4, Fig. 2, is placed in a mould 8 together with a core 9 and the unbreakable crystal leaf 10 is softened by heat and pressed by a die 11 so as to flow into groove 6 of ring 4 and to form an internal shoulder 7. The die remains in position until the parts are cool. Instead of die 11, a cylinder 12 may be lowered on to the softened leaf 10 and the moulding achieved by compressed air. In Fig. 3, the crystal is moulded to the front 14 of a single two-part casing. Various modified shapes are illustrated in Figs. 4-9 (not shown), for the inter-engaging section 15 of the crystal and case. In the modified construction of Fig. 11, the unbreakable crystal 18 is the full depth of the metal ring 17 and is attached thereto as described above. The back edges of parts 17 and 18 are shaped to form a groove in which a ring 27 of elastic material is pressed by the edge 26 of the back 19. A spring leaf 21, housed in a groove 20 of the back 19 has parts 24 which snap into recesses 25 of the case 16 so that the back 19 is held against the ring 27 and the glass 18 against the forward edge of case 16.