I had the privilege of being awarded two US patents while working with Eaton Corporation.
Based on 555 timer IC to conserve space.
Space too small for conventional switches. |
Contoured switches with insert molded graphics for durability.
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Printed circuit inserted from below, dome switch PCB and rockers on top.
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Life tester designed for use in a thermal chamber.
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The motivation behind this effort was the difficulty in obtaining properly made contactors.
The part is made using 4 slide tooling. On the non-contact end is a hairpin spring formed to slip over the fiber carrier, and s small lanced barb to catch the fiber board. Bending that hair pin was an ongoing problem. The functional issue was that if the hairpin was too loose, or if it took a permanent set (also loose) when attached to the carrier, then the contact force would be very low, as the carrier would rotate farther allowing the main spring to extend too far.
Even the measuring of it and getting agreement with the supplier was hard for all concerned. We experimented with heat treated beryllium copper which is much harder than the hardened copper we had specified, and also tried an aluminum bronze (Olin product); both would have had greater strength. However, simply eliminating the spring seemed to make more sense. The changed design was very unambiguous from a dimensional control, and quality assurance point of view.
The new design eliminates the root cause of the trouble - it gets rid of the hairpin spring. There is more scrap in the forming process (which is of course recycled). The making of the part no longer requires a 4 slide machine.
Life testing under load for one million cycles demonstrated the design was sufficient for the application.
The part is made using 4 slide tooling. On the non-contact end is a hairpin spring formed to slip over the fiber carrier, and s small lanced barb to catch the fiber board. Bending that hair pin was an ongoing problem. The functional issue was that if the hairpin was too loose, or if it took a permanent set (also loose) when attached to the carrier, then the contact force would be very low, as the carrier would rotate farther allowing the main spring to extend too far.
Even the measuring of it and getting agreement with the supplier was hard for all concerned. We experimented with heat treated beryllium copper which is much harder than the hardened copper we had specified, and also tried an aluminum bronze (Olin product); both would have had greater strength. However, simply eliminating the spring seemed to make more sense. The changed design was very unambiguous from a dimensional control, and quality assurance point of view.
The new design eliminates the root cause of the trouble - it gets rid of the hairpin spring. There is more scrap in the forming process (which is of course recycled). The making of the part no longer requires a 4 slide machine.
Life testing under load for one million cycles demonstrated the design was sufficient for the application.