Buckles – buttons – clasps – etc. – Having magnetic fastener
Patent
1995-11-06
1997-12-30
Cuomo, Peter M.
Buckles, buttons, clasps, etc.
Having magnetic fastener
335285, 24265WS, A44B 1125
Patent
active
057016402
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention lies in the field of closures for wrist straps, in particular for straps of wrist watches. The most commonly used closures are currently buckle closures. They guarantee secure closure of the two strap ends, are easy to adapt to the wrist size of the watch wearer and are also inexpensive to manufacture.
BACKGROUND OF THE INVENTION
The buckle closure is however somewhat awkward to position around the wrist, both during fastening and during unfastening. It requires a relatively stiff watch strap on account of the holes, which have to absorb the tensile forces effective in the strap. The material used is almost exclusively leather or plastic. Woven textile straps would, in terms of pattern and color, admittedly be more suitable as watch straps but they may not be satisfactorily combined with the buckle closure.
Mechanical closures are also being used instead of buckles, although mainly for metal watch straps. With such closures, however, adaptation to the size of the wrist is critical and the mechanical closure parts, e.g. the springs, impose fairly high quality requirements during manufacture.
Numerous solutions for closures are known which utilize the force of attraction of permanent magnets. The German patent specification DE 2 855 708 C2 held by Kodama discloses a magnetic closure, in which a permanent magnet in a magnetic circuit attracts a second closure piece. Here, a separating force of around 4N (newtons) is attained, with there being no provision for an additional mechanical lock, e.g. by the positive engagement of one part behind another. This solution however calls for relatively strong magnetic fields and there is therefore still no reliable guarantee that the closure will not be torn off or accidentally opened.
Other solutions likewise involve the attraction of the two closure parts connected to the strap ends by means of permanent magnets, although in the end position a mechanical lock is additionally provided so that the tensile force acting upon the two closure parts is absorbed, not by the magnetic adherence force, but by a mechanical catch.
In U.S. Pat. No. 4,622,726, Nakamura discloses a solution in which, in the attracted state of the two closure parts, one part, as a result of being rotated slightly about its own axis relative to the other part, is moved into a mechanical notch which is capable of withstanding even high tensile forces. The drawback of said solution is that locking does not occur automatically but requires an additional specific manual movement.
Up until now, however, such closures having permanent magnets have not been able to gain acceptance in the field of watch straps, for various reasons.
One important reason is certainly the fact that the accuracy of all timepieces is impaired to a greater or lesser extent by strong magnetic fields. Timepieces may admittedly be protected by special ("anti-magnetic") measures against magnetic fields but this entails considerable extra cost.
The quartz watches with an analogue display which are currently dominating the watch market are based on a stepper motor, which contains a rotating magnet and is therefore very sensitive to magnetic interference fields. If, when the wrist watch is taken off, the closure part fitted with a permanent magnet comes near to the clockwork mechanism, its accuracy is impaired to an unacceptable extent.
The currently available magnetic closures obviously do not satisfy the requirements regarding the leakage field intensity when the closure is open so that their use, at least with quartz watches, is still largely precluded.
SUMMARY OF THE INVENTION
The invention relates to a device for a magnetic closure for wrist straps, in particular for wrist watches, having two closure parts and having permanent magnets which connect the two closure parts by means of a magnetic latching force.
The object of the present invention is to indicate a magnetic closure for wrist watches which, even in the open state, in the event of accidental contact with the clockwork mechan
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patent: 4622726 (1986-11-01), Nakamura
patent: 4779314 (1988-10-01), Aoki
patent: 5191685 (1993-03-01), Aoki et al.
patent: 5249338 (1993-10-01), Aoki
patent: 5274889 (1994-01-01), Morita
patent: 5317789 (1994-06-01), Levy
Cuomo Peter M.
Vu Stephen
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