GB992882A - Method of making taper leaf springs - Google Patents

Abstract

992,882. Making leaf springs; bending; rolling; altering physical structure by mechanical treatment; working at specified temperatures. ROCKWELL-STANDARD CORPORATION. Aug. 26, 1963 [June 12, 1963], No. 33732/63. Headings B3A, B3E, B3M and B3V. In the manufacture of a leaf spring by taper rolling a blank and stress relieving the tension side, the latter is ground to remove surface imperfections, scale and oxide before stress relieving. For making a single or dual leaf vehicle spring, a flat steel blank 40, Fig. 1, is first ground on its tension side 44 by a grinding belt 46 or discs to provide a smooth flat surface. The compression side may also be ground or shot blasted. Blank 40 is then heated to 1200-2250‹ F. in an induction furnace having an inert atmosphere containing lithium vapour which sticks to the blank to prevent oxidation and also acts as a lubricant during taper rolling. This is effected in a die 58, Fig. 3, by a roll 62 pressed downwardly by a cam 64 which has longitudinal movement; the die may have a longitudinal cavity for preventing lateral spread. Both ends of the spring are rolled successively or two rolls may act simultaneously on both ends. In an alternative process the blank may be ground after heating and before rolling. Further grinding may also be performed after rolling. The rolled blank has a central hole formed by drilling or piercing, Fig. 4 (not shown), its two ends are heated simultaneously in gas furnaces 102, 104, Fig. 6 (not shown), and attachment eyes 108, Fig. 7, are then formed by rolls 110. After heating in a furnace to austenitizing temperature, the blank 65 is pressed between dies 74, 72, Fig. 9, and whilst under pressure immersed in quenching oil which produces a high percentage of martensitic structure. The blank is then tempered and afterwards peened under a stress of at least 75% of its yield stress by clamping it on a flat surface and throwing shot from wheels 77, 78 (Fig. 11) or from air nozzles. Reverse bending over a former, Fig. 12 (not shown) is then effected for presetting the spring after which it is inspected and checked for thickness, Fig. 13 (not shown) and immersed in a bath to provide a corrosion resistant coating, Fig. 14 (not shown). Specification 921,393 is referred to.