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E39 cap fastened by the G.E. "Crimp-Shell" technique.

E39 cap fastened by the G.E. "Crimp-Shell" technique.

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This patented technique was one of the first "cementless" techniques used for attaching the bases to lamps and developed by G.E. in the late 1930's or early 1940's I it has been around a while.

Basically it involves pushing a four-fingered sub-shell onto the specially molded bulb-neck where domes on each finger snap into dimples molded into the neck. Once this is done, one lead-in wire is spot-welded to the sub-shell to make the electrical connection. Lastly the E39 cap is screwed-on over the threaded part of the sub-shell and three rectangular holes a punched through the sides by a special triangular tool that curls burrs in at the top and bottom edges of each hole, this crimps the cap in place...AND hence the name, "Crimp-Shell"

For a lamp collector, these details are important. because, although two lamps may bear the same type number and be functionally the same with regards to the desires of the end-user, differences like base attachment allow the lamp to be provided with a precise providence and chronology of development.

In a serious lamp database, one should provide a field for such details.

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Filename:Crimp Shell Composite m.jpg
Album name:Globe Collector / Miscelaneous Lamp related stuff
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Date added:Feb 11, 2019
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Feb 19, 2019 at 03:16 PM Author: James
This is actually quite an old design, developed by GE in 1929 - see US Patent 1,832,751. It is cheap and easy and does not easily come loose, but the stresses placed on the glass are not always desirable - the glass has to be quite thick and may still crack. A generally better solution is the mix of green and white striped capping cements used by some other manufacturers, with two different cement kinds having different thermal and mechanical properties.
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