GB582987A - Improvements in non-metallic springs and ducts and methods of making the same - Google Patents

Abstract

A coiled spring comprises a textile strand, e.g. of yarn, string, cord, &c. or a strand of asbestos or spun glass, heavily coated with resinous material and set in the form of a plurality of helical coils, the coating forming a hard continuous jacket of substantial thickness and rigidity. The resin may be applied as a liquid or a resin solution or emulsion and may be of the thermoplastic or thermosetting types, such as phenol-formaldehyde resins, polyhydric alcohol-polybasic acid resins (i.e. those known under the Registered Trade Mark "Glyptal"), urea-formaldehyde, polyvinyl chloride, vinyl chloride and vinyl acetate copolymer, polystyrene, or polymerized ethyl acrylate. The spring is made by applying the resin to the textile strand, subjecting the wet-coated strand to a drying operation so that it partly sets, winding the strand helically around a mandrel with the coils spaced from each other and thereafter solidifying the coating, e.g. by heat, while the strand is on the mandrel. If the spring is not to be exposed to high temperatures, the coating may be a fusible resin, e.g. the linear superpolyamides, applied in molten condition and solidified by cooling, whereas if the spring is to be exposed to high temperatures, the strand is of non-combustible material, e.g. asbestos, and the coating may be a heat-hardened infusible material such as a solution of the material known under the Registered Trade Mark "Bakelite." A textile strand having a reinforcing core strand of fine metallic wire may be employed if magnetic disturbance by the spring is of no consequence.