Apparatus for longitudinally stretching film

Claim 1

In an apparatus for longitudinally stretching continuous, organic polymeric, thermoplastic film moving along a predetermined path, an improved film softening arrangement comprising: a. a pair of mirror-finished rotatable rollers of a width at least substantially equal to the film width arranged in parallel adjacent non-contacting relation, said rollers being sufficiently close together that mutually facing arcuate peripheral portions thereof define a convex-sided V, said film path passing in generally planar fashion over the open top end of said V in at least tangential contact with the roller peripheries at the respective ends of said V, whereby radiation passing through said film path into said V is reflected by the arcuate sides thereof backwardly toward said film path, b. an elongated infrared heater disposed on the opposite side from said rollers of said film path over the open end of said V and in close proximity to said film path to direct infrared radiation over substantially the entire film width, said heater having its axis parallel to the film path plane at a locus approximately equidistant from the axes of said rollers, c. means independent from said elongated heater for heating the upstream roller and means for cooling the downstream roller, and d. means for advancing said film along said path so that the film is stretched while passing across the top of said V and said second roller turns at a higher peripheral speed than said first roller.