I found the patent again. Turns out I already had it. This shows the La Hiff variable main spring on a Lightening Bug type key. It is USP 2187351 at: https://patentimages.storage.googleapis.com/31/d1/c8/b34c68f33be536/US2187351.pdf -- Richard Knoppow 1oldlens1 at ix.netcom.com WB6KBL