Electrical igniting unit having spiral resistance coil

Abstract

An electrical igniting unit for cigar lighters, engine ignitor plugs, and the like comprising a wound spiral of resistance ribbon which is carried in a shallow metal cup to span the mouth thereof. The inner end of the ribbon is secured to a metal stud as by crimping and/or welding it in a slotted head thereof. The outer coil convolution is secured to the rim of the cup by forming inward the rim edge into a tight curl which is laid over on the end portion of the coil convolution. A relatively large area of the coil end is thus tightly and securely pinched under continual pressure, to establish a low-resistance effective mechanical and electrical connection between the cup and the coil. The metal cup is made of steel, and in order to solve the problems of destructive cracking of the cup wall or peeling of plating, as well as rusting and pitting of the wall where it engages the cooperable electrical contacts, the cups are mass heat treated by a low-temperature nitriding process which causes a shallow penetration of from 0.0002 inch to roughly 0.0006 inch. Such nitriding does not impair the ability of the cup wall to be inwardly curled without destructive cracking while at the same time it provides a protective coating which is resistant to abrasion, corrosion and the like, although still retaining satisfactory electrical conducting characteristics. satisfactory