Method and apparatus for embossing plastic film

Claim 2

In an apparatus for heating thermoplastic film, the combination comprising: a. a pair of opposed heated air supply ovens defining therebetween a vertically extending, enclosed heating zone adapted to heat said film to its softening point as it passes through said zone, each of said heated air supply ovens including, i. a horizontally extending, elongated, heated air inlet chamber provided with a wall having perforations therein, ii. a horizontally extending, elongated, heated air return chamber provided with a wall having perforations therein mounted below said heated air inlet chamber, iii. a downwardly directed heated air supply duct defined by the space between an upper air deflector structure having its upper end attached to the top of said perforated wall of said heated air inlet chamber, and an intermediate air deflector structure having its upper end attached between the lower end of said heated air supply chamber and the upper end of said heated air return chamber, iv. a downwardly directed return air duct defined by the space between a lower air deflector structure having its upper end attached to the lower end of said perforated wall on said heated air return chamber and said intermediate air deflector structure; b. a common end wall attached to each end of the two ovens; and c. a common top wall attached to the tops of both ovens, said top wall having an opening therein to receive said film.

Claim 3

In the apparatus of claim 1 wherein said heated air inlet duct terminates in a narrow, horizontally extending, rectangular slot.

Claim 4

In the apparatus of claim 1 wherein each of said perforated walls of said inlet and said outlet chambers are provided with a plurality of spaced apart, vertically extending louvers.

Claim 5

In the apparatus of claim 3 wherein an adjustable baffle plate is spaced from each of said perforated walls on the side opposite said louvers.

Claim 6

In an apparatus for embossing thermoplastic film, the combination comprising: a. means for guiding and moving a continuous, vertically extending, preformed length of said film into a vertically extending heating zone; b. a pair of opposed, heated air supply ovens defining therebetween said heating zone for heating said film to a temperature above its softening point, each of said ovens including an elongated, heated air inlet chamber terminating in a narrow, rectangular, horizontally extending heated air exit slot, and an elongated return air chamber terminating in a narrow, rectangular, horizontally extending return air gap, said return air gap being positioned below and adjacent to said heated air exit slot; c. conduit means outside of each of said air supply ovens connecting said return air chamber to said heated air inlet chamber; d. circulating means outside of said supply ovens in each of said conduit means for circulating heated air through each one of said supply ovens; e. heating means in said conduit means for heating said air; f. a pair of opposed, counter-rotating, film-contacting, embossing rolls positioned immediately adjacent to said heated air exit slot and said return air gap of each of said supply ovens so that air is blown against said film immediately before said film contacts said embossing rolls, said embossing rolls receiving said heated film for embossing a pattern thereon and for deflecting air from said heated air exit slot to said return air gap for each of said supply ovens; and g. means to Cool said film substantially below its softening point to fix said embossed pattern in said film.

Claim 7

In an apparatus for embossing thermoplastic film, the combination comprising: a. means for guiding and moving a continuous, vertically extending, preformed length of said film into a vertically extending heating zone; b. a pair of opposed, heated air supply ovens defining therebetween said heating zone for heating said film to a temperature above its softening point, each of said ovens including an elongated, heated air inlet chamber terminating in a narrow, rectangular, horizontally extending heated air exit slot, and an elongated return air chamber terminating in a narrow, rectangular, horizontally extending return air gap, said return air gap being positioned below and adjacent to said heated air exit slot; c. conduit means outside of each of said air supply ovens connecting said return air chamber to said heated air inlet chamber; d. circulating means outside of said supply ovens in each of said conduit means for circulating heated air through each one of said supply ovens; e. heating means in said conduit means for heating said air; f. a pair of opposed, counter-rotating, film-contacting, embossing rolls positioned immediately adjacent to said heated air exit slot and said return air gap of each of said supply ovens so that air is blown against said film immediately before said film contacts said embossing rolls, said embossing rolls receiving said heated film for embossing a pattern thereon and for deflecting air from said heated air exit slot to said return air gap for each of said supply ovens; and g. means to Cool said film substantially below its softening point to fix said embossed pattern in said film.

Claim 8

In the apparatus of claim 5, wherein means for enclosing said heating zone are provided, said enclosing means having openings at its top and bottom for entry and exit of said film to and from said heating zone.

Claim 9

In the apparatus of claim 6 wherein said means of subparagraph a) includes a pair of normally contacting pull rolls and means to drive said rolls.

Claim 10

In the apparatus of claim 7 wherein said enclosing means includes a housing positioned adjacent at least one of said pull rolls and providing the opening for the entry of said film into said heating zone.

Claim 11

In the apparatus of claim 5, wherein at least one of said embossing rolls is hollow and said means to cool said film includes means for supplying a flow of cooling fluid to said at least one of said embossing rolls.

Claim 12

In the apparatus of claim 5, wherein said means of subparagraph c) includes a fan for each of said heated air supply ovens.

Claim 13

In the apparatus of claim 5 wherein said heating means includes at least one electrically powered heating element.

Claim 14

In the apparatus of claim 5 wherein each of said heated air supply ovens is provided with adjustable means for diffusing the heated air supplied to said heating zone.

Claim 15

In the apparatus of claim 12 wherein said diffusing means includes a plurality of vertically extending louvers are mounted adjacent a wall provided with a plurality of openings therein.

Claim 16

In the apparatus of claim 13 wherein an adjustable baffle is spaced from said wall on the side opposite said louvers.