The arm stop itself is defined by the striking of the two front faces against each other. Nevertheless, spring hinges have been widely used, because they protect the parts which produce the swivelling movement from overloading when the spectacles are opened too far. A confortable seating of the spectacles also results when the spectacles have to be moved beyond the normal angle of the arm; if, for example, the spectacles are placed on the forehead instead of the nose, or the spectacles are played with, etc.
The spring hinges known up to now are expensive, are composed of several parts, can be provided only on the inside of the stay bar/spectacle arm section, are too cumbersome to be able to be used in elegant metal spectacles, are conspicuous, require the use of special hinges and require the springs to have certain shapes and certain settings, which result in very variable specific stress.
USPTO Backgrounds
USPTO Backgrounds