GB372989A - Improvements in and in the manufacture of grid leaks and like high electrical resistances - Google Patents

Abstract

372,989. Resistances. LISSEN, Ltd. and WALKER, W., Worple Road, Isleworth, Middlesex. June 25, 1931, No. 18407. [Class 37.] A grid leak or like high resistance for small currents is made from a strip of prepared paper 2 wound helically on a core 1 of cord or string and has metal tags 3 at its ends embracing both strip and cord. The cord or string is impregnated with insulating composition, for instance by immersion for ten minutes in wax at 150‹ C., the wax comprising equal parts of heel ball and resin, with a little paraffin wax. A narrow strip of paper 2, such as that described in Specification 252,759, [Class 37, Electricity, Measuring &c.], is wound on the cord, and T-shaped metal tags 3 are attached by wrapping the broad limb round the cord. One tag is clinched tight and the second adjusted until the resistance has the desired value, and is then clinched. The cord is then cut off and the resistance unit immersed for an instant in paraffin wax at 85 to 95‹ C. The resistance is then inserted in a tube 4, Fig. 3, of varnished impregnated paper and the ends of the tags are bent round the ends of the tube, metal caps 5 being then pushed on. To prevent the tags from being dragged along the resistance by the caps 5, the tag stems may be slit as shown, one part being doubled inside the tube and the other part folded over the edge of the tube Alternatively the tag stem may be of greater width up to the ends of the tube than in the projecting part, so as to form a shoulder. A length of impregnated cord may be stretched between uprights, wrapped with paper and fitted with tags in pairs at the required intervals, the cord then being cut between adjacent tags, or the impregnated cord may be drawn forwards continuously and wrapped from a rotating roll of resistant paper.