US2187863A

US2187863A - Watch crystal for watertight watches

Info

Publication number: US2187863A
Application number: US124495A
Authority: US
Inventors: Morf Ernest
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-05-11
Filing date: 1937-02-06
Publication date: 1940-01-23
Anticipated expiration: 1957-01-23

Description

Patented Jan. 23, 1940 UNITED STATES 2,187,868 ws'rcn cars-ran roa warn-anon WATC Ernest mm, La Chaux-de-Fonds, swam-nus Application February 8, 1937, Serial No. 124,495 In Switserland May 11, 1936 3 Claims.

| water pass into their inside to cause corrosion of the metallic parts or to form a damp vapor which is deposited on the crystal and hinders the reading of the dial. Such leakage is all due to an inefficient tight joint between bezel, crystal and 10 case band the water penetrating through said joint when the temperature of the interior of the watch contracts the air therein enclosed.

-'----- Packings;-have-be'en used for overcoming said These packings must besomewhat resilient and must therefore have a certain thickness, which determines also the depth of the groove. Now since this groove must on no account extend into the hole of the winding stem it becomes necessary to keep the case band somewhat thickened when said packings are used. g

The object of this invention is a crystal which may be put in without the above-mentioned inconveniences. The invention consists in providing a crystal having atleast partly compressible If the crystal is made, for instance, of a transparent artificial resin, like that known by the name of "Ple'xiglass", which is a synthetic resin obtained by a polymerization of lactic acid, the edges of such a crystal, after being thinned, could be covered with a'molliiled band of the same resin. which, as is known, can be produced with a consistency varying from a pasty mass, to an elastic sheet and finally, according to its treatment, to a colourless horny plate which will break only after being bent at a very sharp angle. This bandconsists of a permanently soft synthetic resin material which remains soft at room temperatures. Such a'crystal can be pressed between besel and case band to form an absolutely tight joint which will prevent entry of humidity into the watch.

Another manner of proceeding consists in mollifying the edges of the watch crystal, made of resin, after having given it the desired form. either by a thermal or by a chemical treatment. andinclampingitbetweenthebezelandthecase band so that it forms a permanently soft packing closely applied to said two members. This softened edge remains soft at room temperatures. The annexed drawing shows as examples some embodiments of the invention.

Fig. 1 shows partly in plane square watchcrystal.

Fig. 2 is a sectional view on line lI-II of Fig. 1. Fig. 3 is a sectional view on line III-HI of the crystal shown in Fig. 4.

Fig. 4 is a plan view of a circular crystal. Fig. 5 is a sectional view of a circular watch crystal having edges prepared according to the invention.

In the crystal according to Figs. 1 and 2 the edges a have been thinned. They have been coated with a layer b of a mass which consists in a small band of resin having a permanently soft consistencywhich remains so at room temperatures. when the crystal is clamped against the case band this kind of packing is perfectly flsht.

InthecascofFigs.8and-itheinclinededge a of the synthetic resin crystal has been softened throughout its thickness by means of .a thermal process applied before the crystal was curved. By

7 this softening a pasty and resilient consistence has been given to the crystal which is characteristic for such artificial resins and which imparts to a watch crystal the qualification of an unsurpassed hermetic packing.

In the caseof Pig. 5, the softened layerb hasbeenattachedtotheumrsurfaceofthe edge a. Besides this the same conditions exist here for attaching and tight keeping as in the Figs. 1 and 2.

What I claim is:

1. A watch crystal of resilient transparent synthetic resin having edges, one surface of said edges comprising a permanently soft synthetic resin material.

2. A watch crystal of resilient transparent synthetic resin having edges and a separate superposed layer of permanently soft synthetic resin material on said ed!!!- 8. A watch crystal of resilient t synthetic resin havina integral edges consisting of-a soft synthetic resin material.

ERNEST MORE.