Method for continuously forming a coating layer on unbonded pc steel bars

Abstract

Steel bars are continuously fed along an inclined path in a direction transverse to the bar axes, are separated one from another by a separator and are then supplied by a roller conveyor to an axial interval regulating station. From this station one steel bar after another is supplied in the axial direction with regular intervals between the bars by means of sets of pinch rollers which are provided at specific intervals and which can be separately dislocated out of the path of movement of the bars and by means of a rod and a spacer fitted to the tip of a swing rod pivotally connected to the rod. Steel bars are thus delivered at regular intervals to a coating station and thereat have the entire lengths thereof, except the threaded end portions thereof, coated with a coating layer of asphalt, epoxy resin or grease by a coating device including a fixed outer nozzle and a movable inner nozzle. Thereafter, the coated bars are sent to a taping station, whereat the entire lengths of the bars, including the coating layers, are tightly wrapped by a thermo-shrinking tape by means of a tape unwinder, a tape guide roller, a tape guide pipe and a welder. Then, with movement of the steel bars, the tubular tape portion is heated by a heater, whereupon the tubular tape shrinks, thereby closely fitting around the steel bar surface including the coating layer. Thus, plural steel bars are continuously axially connected and integrated by the tape. The thus axially connected steel bars are then moved to a cutting station by a special caterpillar whose grip distance can be adjusted to the diameter of the steel bar to be transported. At the cutting station a cutter which acts on a signal issued from a photoelectric detector cuts the hollow tubular tape portion between adjacent connected steel bars. The thus separated bars are supplied to a discharge station, whereat they are discharged from the axial path to a specified location.