Abstract: Provided is a protective member for coil springs, including a tube main body that covers a coil spring of a suspension, wherein the tube main body is made of thermoplastic polyurethane that includes a prepolymer and a chain extender, wherein the prepolymer includes diisocyanate and a polyol, wherein a molar ratio of the diisocyanate to a sum of the polyol and the chain extender (diisocyanate/(polyol+chain extender)) is 1.025 to 1.040 and a molar ratio of the chain extender to the polyol (chain extender/polyol) is 6 to 3.8.

Abstract: A laser marking system for coil springs includes: a support unit; a first fixing jig coupled to the support unit and contacting one surface of a coil spring; a second fixing jig located at a side facing the first fixing jig and contacting an surface opposite to the surface of the coil spring; a moving unit frame connected to the support unit and to which the second fixing jig is fixed; a moving unit servo motor connected to the moving ball screw; a marking unit frame connected to the moving unit frame and configured to move forwards and rearwards towards the coil spring to perform a marking operation on the coil spring; a marking unit ball screw connected to the marking unit frame; a marking unit servo motor connected to the marking unit ball screw; and a laser marker fixing to the marking unit frame.

Abstract: A marking system for springs comprises: an arranging apparatus for arranging a spring; and a marking apparatus for applying an identification mark on the spring. The marking apparatus comprises: a frame having a space for marking therein; a pad unit for applying a mark on the spring located in the frame; and an ink unit for supplying ink to the pad unit.