Method and apparatus for assembling a watch case having improved structure for installing a battery cell
AssigneeETA SA Fabriques d'Ebauches
InventorsJacques Muller, Elmar Mock
Life of this patent
Estimating the term…
Abstract
A cover 20 for a cell cavity 7 in a plastic watch case 2 is provided on its periphery with three lugs 28. The back surface 4 of the case is provided with three recesses 12 into which the lugs can enter freely. With the aid of a tool 38, the cover is rotated while ultrasonic or thermal energy is applied to the lugs. Thanks to this energy, the lugs themselves deform and move into the thermoplastic material in order thereby to form three undercuts. A bayonet joint closure assembly is thus formed. See FIG. 5.
Claims13
A method of installing a battery cell in an outwardly opening cavity provided in a watch case made of thermoplastic material, comprising the steps of:
- providing a closure having a plurality of radially extending lugs, said closure being sized to close said cavity;
- providing around the opening of said cavity a corresponding plurality of radially extended, circumferentially spaced, outwardly opening recesses sized to receive said lugs when said closure is placed in said opening;
- positioning a cell in said cavity;
- positioning said closure at said opening with said lugs extending into said recesses;
- rotating said closure while applying energy to said lugs;
- and
- causing each of said lugs to engage a side wall of its respective recess, whereby said thermoplastic material softens sufficiently to permit said lugs at least partly to enter the portions of said watch case between said recesses as said closure is rotated, to form undercuts in which said lugs remain when said rotating ceases, thereby ensuring the secure installation of said closure.
Apparatus for installing a closure at an outwardly opening cavity for a battery cell, said cavity being provided in a watch case made of thermoplastic material, said apparatus comprising:
- a plurality of radially extended, circumferentially spaced, outwardly opening recesses positioned around the opening of said cavity;
- a corresponding plurality of radially extending lugs provided on said closure, said lugs being sized to be received by said recesses when said closure is positioned at said opening;
- and
- means for forming a corresponding plurality of undercuts in a side wall of each recess by rotating said closure while applying energy to each of said lugs, whereby said thermoplastic material is softened sufficiently to permit said lugs at least partly to enter and engage the portions of said watch case between said recesses as said closure is rotated, thereby ensuring the secure installation of said closure.
Dependencies are inferred from the claim text.