Continuous laminating system

A continuous laminating system is disclosed wherein a pair of rotating laminating rollers are provided which form a laminating nip through which a product to be laminated together with sheets of laminating film are fed and pressed. A pair of rearwardly positioned pull rollers pull the laminating film through the laminating rollers together with the product. Adjacent each laminating roller a shoe-type heating member is provided which has a concave surface adjacent the respective laminating roller and a convex heating surface positioned so that the laminating film from each of the supply rollers slides over the heating surface and is heated prior to entry into the laminating nip. A Teflon-coated fiberglass layer is provided at least over portions of the convex heating surface over which the laminating film slides. Problems of scratching of the laminating film and squealing during processing are solved according to the invention.

BACKGROUND OF THE INVENTION 
In large scale laminating systems, it is known to provide upper and lower 
feed rollers for continuously supplying a strip or sheet of laminating 
film which has a heat sensitive adhesive on a product-facing surface 
thereof. Such laminating films are well known in the art as polyethylene 
films which are transparent and which have a heat sensitive adhesive 
thereon which joins to the product to be laminated and also to the 
opposite facing thin film so as to form a packet. In the large scale 
laminating systems, the laminating film is fed continuously and after the 
laminating of a continuous product, the product is slit transversely to 
the running direction of the laminated product and/or along the direction 
of travel so as to cut the laminated product into individual units such as 
I.D. cards. 
With such systems, it is also known to provide a heating shoe or member 
positioned adjacent each of the laminating rollers such that the 
continuous rolls of film being supplied from the supply rollers pass over 
a heating surface of the shoe just prior to entering a nip between the 
upper and lower laminating rollers. These shoes heat the laminating film 
to a desired temperature just prior to the pressure laminating in the nip 
between the two laminating rollers. 
Previously, as the film is dragged over the hot shoe, miniscule 
irregularities in the shoe surface would scratch the film and introduced 
obvious marking to the detriment of ultimate use. While the functional use 
of the finished laminate was not greatly affected, the aesthetics were 
such that the commercial viability of such large scale laminating systems 
was impaired. 
In addition to the scratching problem, the dragging of the film over the 
shoes especially at high speed and elevated temperatures consistently 
produces a high pitched squeal. This squeal at times becomes intolerable. 
Attempts have been made to solve the squealing problem by altering the 
tension on the webs or dampening. Neither approach was successful. 
SUMMARY OF THE INVENTION 
It is an object of this invention to prevent scratching of laminating film 
in large scale laminators and at the same time to eliminate a high pitched 
squeal caused by the dragging of the laminating film over the heat shoes. 
In accordance with the invention, on a heat shoe having a concave inner 
surface adjacent to a laminating roller and a convex heating surface over 
which the laminating film slides, a layer of Teflon-coated fiberglass is 
provided which covers at least all portions of the convex heating surface 
directly over which the laminating film would otherwise slide. Preferably 
the Teflon-coated fiberglass is preferably of a material known by the 
registered trademark TEMP-R-GLAS, a product of the Conneticut Hard Rubber 
Company (CHR). 
Preferably the layer of Teflon-coated fiberglass is clamped to non-heating 
surfaces of the heating member but is not directly secured to portions of 
the convex heating surface. 
Previous to the discovery of this invention, it was thought that sheets of 
material applied to the heating surfaces could never solve the problems of 
scratching and squealing since such separate layers would greatly reduce 
the heat transfer between the laminating film and the heat shoe. 
Furthermore, Teflon layers directly applied to the heating shoe surface or 
applied after roughening of the heating surface, were tried and rejected 
since either the scratching problem was partially corrected without 
correcting the squealing problem or the squealing problem was partially 
corrected without correcting the scratching problem. 
Upon wrapping a sheet or layer of the Teflon-coated fiberglass over the 
heating surfaces of the heating shoes it was unexpectedly discovered that 
heat transfer was not adversely affected and both the squealing and 
scratching problems were virtually completely eliminated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The improved laminating system of the invention is generally shown at 10 in 
FIG. 1. An upper freely movable, driven laminating roller 11 is positioned 
adjacent and in contact with a lower freely movable driven laminating 
roller 12 so as to form a pressure nip between the two rollers for 
laminating. An upper heater member 13 typically known as a "heating shoe" 
is provided adjacent the upper roller 11. Similarly a lower heating member 
14 is provided. Each of these heating members has respective concave inner 
surfaces adjacent to and of a curvature similar to the respective 
laminating rollers and also having convex heating surfaces 13a and 14a 
over which respective upper and lower laminating films 16 and 17 slide. 
A continuous product 15 to be laminated is fed toward the nip between the 
laminating rollers 11 and 12 together with the laminating films 16 and 17 
above and below the product 15. 
The laminating film 16 or 17 is typically a polyethylene sheet or strip of 
film suitable for laminating, as is well known. On this sheet or film a 
layer of heat activatable adhesive 16a or 17a is applied on the surface 
away from the heating member surfaces 13a and 14a but facing the product 
15 to be laminated. The films 16 and 17 respectively ride over 
de-wrinkling rollers 18 or 19 respectively, and respective idler rollers 
20 and 21. Film supply rolls 22 and 23 feed a continuous supply of the 
respective laminating films 16 or 17. 
Rearwardly or downstream of the laminating rollers 11 and 12 cooling fans 
24 and 25 above and below the laminated product may be provided to enhance 
cooling. Thereafter, a slitter 26 is provided for slitting the product in 
the running direction thereof. The slit product preferably enters upper 
and lower pull rollers 27 and 28 which are driven and therefore pull the 
product through the freely movable upper and lower laminating rollers 11 
and 12. A static eliminator 29 may be provided downstream of the pull 
rollers together with a cross or transverse cutting member 30 which cuts 
the individual products after lamination is completed. 
Over the respective heating member heating surfaces 13a and 14a a layer or 
sheet of Teflon-coated fiberglass 31 or 32, (Teflon being a trademark of 
DuPont) is tightly wrapped as most clearly shown in FIG. 2. In a preferred 
embodiment of the invention, the Teflon-coated fiberglass is a material 
sold under the trademark TEMP-R-GLAS of the Conneticut Hard Rubber Company 
(CHR). 
The Teflon-coated fiberglass employed in the invention has a preferable 
thickness between 0.003 and 0.010 inches, but in any case no greater than 
0.030 inches. Greater thicknesses cannot be employed since they adversely 
effect heat transfer. Also the fiberglass material employed should 
function efficiently through a temperature range of room temperature to a 
least 200.degree. F. Furthermore the material has a "slippery" quality 
sufficient to substantially prevent squealing and scratching during 
lamination. 
As shown in FIG. 2, the lower shoe or heating member 14 is closely aligned 
adjacent the lower laminating roller 12. The convex heating surface 14a 
has the Teflon-coated fiberglass 32 pulled thereover and the concave inner 
surface 14b is aligned directly adjacent the outer periphery of the roller 
12. 
The heating member 14 has its convex and concave surfaces 14a and 14b 
terminating in one end at a flat wall 42 substantially perpendicular to 
the adjacent portions of the concave and convex surfaces. One end of the 
sheet 32 is bent over into contact with this wall 42 where it is clamped 
by use of a retaining plate 35 more clearly shown in the end view of FIG. 
2A. This retaining plate 35 traps the end of the sheet 32 between itself 
and the end wall 42 by use of two flathead screws 33a, b received in 
threaded bores 34a, b of the heating element. A lip 35a is provided on the 
retaining plate 35 which cooperates with a depression 36 in the heating 
member for the purpose of more securely fastening the end of the sheet 32 
to the end wall 42. 
At the opposite end of the heating member 14 the convex and concave 
surfaces 14a and 14b intersect along an edge 43. The other end or edge of 
the Teflon-coated fiberglass sheet 32 is folded over and around the 
leading edge 43 so that its edge portion lies on a portion of the concave 
surface 14b. Here it is fastened again by use of a retaining plate 38 
having a lip 38a which cooperates with a depression 40 in the heating 
member. A threaded bore 39 receives an undercut flathead screw 37 which 
retains the plate to the concave inner surface 14b. As shown, a portion of 
the concave surface 14b may be carved out so as to allow sufficient 
clearance between the head of the screw 37 and the outer periphery of the 
roller 12. 
With this system of attachment, the Teflon-coated fiberglass sheet is not 
directly contacted to any portion of the heat transfer surface 14a but 
only at ends of the sheet 32. 
As shown in FIG. 3, the width of the sheet 32 is at least as great as the 
width of the laminating film 17 but need be no wider than a width of the 
heating member 14. 
The heating member 14 may employ various types of heating elements. In one 
preferred embodiment, a pocket 41 is provided for receiving a heating 
element 44. Alternatively, rod type heating elements or flat sheet type 
heating elements may also be applied to the heating member 14. 
Although various minor modifications may be suggested by those versed in 
the art, it should be understood that I wish to embody within the scope of 
the patent warrented hereon, all such embodiments as reasonably and 
properly come within the scope of my contribution to the art.