Method for compression molding of retroreflective sheeting and sheeting produced thereby

Claim 1

In a method for embossing synthetic plastic sheet material to generate precisely formed embossments on one surface thereof, the steps comprising: A. disposing one surface of an elongated strip of synthetic thermoplastic sheet material on an elongated member movable in a path providing a series of stations therealong; B. placing on the other surface of said synthetic plastic sheet material a series of embossing molds having the desired embossing pattern in their adjacent surfaces, said molds being closely spaced along the length of said sheet material; C. moving a clamping member against the first of said series of molds to apply clamping force to said first of said series of molds and said elongated member at the first of said series of stations to deform said sheet material therebetween and cause said synthetic plastic thereof to flow into said embossing pattern of said mold to effect embossment thereof; D. moving said clamping member away from said first of said series of molds to release said clamping force on said first of said series of molds and elongated member; E. advancing said first mold and the cooperating portions of said elongated member and sheet material to a second station and a second mold and cooperating portions of said elongated member and sheet material to said first station; F. moving a second clamping member against said first mold to apply a clamping force to said first mold and elongated member at said second station while simultaneously moving said first mentioned clamping member against said second mold at said first station to apply a clamping force to said second mold and said elongated member at the first station to effect embossment of said sheet material thereat; G. moving said clamping members away from said first and second molds to release said clamping force at said first and second stations and advancing the first and second molds and the cooperating portions of said elongated member and sheet material to the next stations while advancing a third mold into registry with said first station; H. moving said first and second clamping members against said molds registering therewith to apply a clamping force to said molds and elongated member at each of said stations; I. repeating the foregoing series of steps to advance said molds, elongated member and sheet material through said series of stations; J. controlling the temperature of said molds at at least some of said stations so that said synthetic resin of said sheet material is readily deformed into the embossing pattern of the mold at said first station and is cooled in its mold in subsequent stations; and K. stripping said embossed sheet material from said molds and elongated member after it has advanced through said series of stations.