Laminating method

A laminating machine and the method incorporated therein includes a pair of opposing and substantially parallel cylindrical steel rollers defining a continuous pressure line between the outer cylindrical surfaces thereof. A sheet is fed between the rollers in a first direction substantially transverse to the pressure line, and a film to be laminated is fed onto the sheet surface and with the sheet in the first direction. A fluid pressure cylinder-lever arm arrangement is provided with one of the rollers for applying relative pressure between the two rollers along the pressure line during passage of the film-sheet combination therebetween, the pressure being in an amount sufficient to compress the sheet to effect complete bonding of the film to the sheet surface, but in an amount less than that which causes structural damage to the sheet. The outer surface of one of the rollers is heated during the laminating process.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
The present invention relates to machines and methods for laminating thin 
decorative films onto sheet material. 
2. Description of the Prior Art 
Furniture products having a wood-grain exterior appearance are highly 
accepted by the purchasing public. However, the cost of manufacturing such 
furniture from wood has become prohibitively expensive. 
An entire industry has developed around the manufacture and use of thin 
polyester carrier sheets adhered to a film having a wood-grain appearance 
printed thereon and provided with an adhesive. The film is laminated to 
the surface of the sheet of material which is a cheap substitute for wood, 
such as fiberboard, hardboard, particle board, plastic, cheaper woods and 
in some cases, even metal. 
The ability to laminate these films onto large sheets, on the order of two 
feet in width or greater, has proven to be less than satisfactory. These 
efforts have also been unsuccessful especially where such attempts have 
been coupled with large volume manufacturing techniques employing a 
plurality of conventional rubber roller pairs using relatively low 
pressures of less than 50 lbs. per lineal inch, in order to prevent 
compression damage to the sheet material being laminated. 
Of course, it will be understood that decorative patterns other than 
wood-grain are often employed with the film lamination techniques used in 
the prior art. 
SUMMARY OF THE INVENTION 
The present invention is based in part upon the realization that heated, 
incompressible pressure members operating at high pressure levels may be 
employed to laminate the thin decorative film to a sheet while the sheet 
is under compression. 
Apparatus in accordance with the present invention, and the method 
incorporated therein, contemplates a pair of opposing members, each member 
disposed so as to define a continuous pressure line therebetween. Means 
are provided for moving one of the members toward and away from the other 
member so as to permit variation of the space between the two members. 
Means are also provided for feeding the film to be laminated and the sheet 
into the space between the two pressure members in a first direction which 
is substantially transverse to the pressure line, and with the film onto 
the surface to which it is to be laminated. Means are further provided for 
applying pressure between the two members in an amount substantially above 
50 lbs. per linear inch along the pressure line and against the film-sheet 
combination, in order to effect the desired bonding of the film to the 
sheet without destroying the sheet. Further means are also provided for 
heating the film-sheet combination while between the members. 
In a preferred embodiment of the present invention, the pressure members 
comprise a pair of cylindrical parallel rollers having a hardness which is 
substantially equal to that of steel. Suitably, the rollers are hollow, 
and the heating means comprises means for circulating a heating fluid in 
at least one of the hollow rollers to heat the periphery thereof, in order 
to heat the adhesive along the polyester sheet - decorative film 
combination film to effect a complete bonding and lamination of the film 
to the sheet. 
In a facile construction of the apparatus in accordance with the present 
invention, pressure is applied to the rollers by the use of a pair of 
lever arms, with one of the rollers being rotatably supported by the lever 
arms. The other roller is mounted on a frame, to which the pair of lever 
arms is rotatably pinned. The other end of the lever arms are moved toward 
and away from the frame by the use of a fluid pressure cylinder 
arrangement.

DETAILED DESCRIPTION 
A preferred embodiment of the present invention will now be described with 
reference to FIGS. 1 and 2. Apparatus in accordance with the present 
invention, referred to generally as 10, includes a pair of parallel 
cylindrical steel rollers 12, 14, disposed so as to define a continuous 
pressure line 13 therebetween. 
The first roller 12 is rotatably supported by a frame member 16, the roller 
12 including a bearing 18 on opposing sides of the roller, it being 
understood that a corresponding frame 16 on the side opposing the side 
shown in FIG. 1 is used to rotatably support the roller 12 in a 
conventional manner. As will be understood below with the description of 
the second roller 14 as shown in FIG. 2, both rollers 12, 14 are hollow to 
permit a heating fluid to be injected therein for purposes of heating the 
cylindrical periphery thereof. To this end, the roller 12 is provided with 
a heating fluid port 20 extending through the bearing 18. It will be 
understood that a corresponding port on the opposing side of the roller 12 
is provided to permit flow through that roller. The cylindrical roller 12 
is driven by a motor 24 via a chain 22 in a conventional manner. 
The second roller 14 is supported above the first roller 12 in a manner 
which permits the space between the two rollers to be controlled, while 
maintaining relative pressure between those two rollers. To accomplish 
this, the apparatus 10 is provided with a riser 26 extending integrally 
from the frame 16. With continued reference to both FIGS. 1 and 2, the 
apparatus 10 further includes a pair of lever arms 28 which are pivotably 
coupled to the frame 16 by way of a pivot arm 30, the pivot arm being 
pivotably coupled at 34 to the respective lever arm 28 and to a bracket 
coupled to the riser 26, and thus, to the frame 16. 
The second roller 14 is further provided with a pair of bearings 38 each on 
an opposing end thereof, and each bearing 38 being supported by a bearing 
block 36 which is coupled to the underside of a corresponding one of the 
lever arms 28. As with the roller 12, the roller 14 is provided with 
heating fluid ports 40. The roller 14 is adapted to be driven by the motor 
24 via a chain 42. 
Noting the upper right-hand portion of FIG. 1, the apparatus 10 is provided 
with a fluid pressure cylinder, for example an air cylinder 44 having a 
piston 46 which is adapted to be driven out of the cylinder 44 under fluid 
pressure in a conventional manner. The extremity of the piston 46 is 
coupled by a pivot 48 to each of the lever arms 28 in order to permit 
changes in the spacing between the rollers 12, 14 and to determine the 
relative pressure between those two rollers along the pressure line 13 
therebetween, as will be described in greater detail below. 
Referring now to FIG. 2, the apparatus 10 includes a fluid heater 50 and a 
feed and return line 52 coupled between the fluid heater ports 40 on the 
respective sides of each of the rollers 12, 14 in order to permit the flow 
of a heating fluid into each hollow roller 12, 14 in a continuous flow so 
as to permit heating of the outer cylindrical surface thereof. 
Referring again to FIG. 1, the apparatus 10 is provided with a sheet 
feeding table 54, 56 which permits the feeding of the sheet material 64 
into the space between the rollers 12, 14 in a conventional manner. 
Likewise, the apparatus 10 is provided with a laminate film feeding 
arrangement, which includes a film supply roller 58, and a pair of guide 
rollers 60, 62 which allow the film to pass across one of the heated 
rollers 14 and thereafter into the space between the two rollers and 
across the surface of the sheet material 64 to which the film 66 is to be 
laminated. The polyester carrier sheet 67 is carried away in a 
conventional manner. 
Use of the apparatus 10 in accordance with the present invention will now 
be described. 
As noted previously, the rollers 12, 14 are a substantially incompressible 
material and preferably comprise steel. Initially, the rollers 12, 14 are 
separated a distance which is slightly less than the thickness of the 
sheet material 64 to which the film 66 is to be laminated. Thereafter, the 
sheet material 64 is fed into the space between the rollers 12, 14 while 
the rollers are being heated by the fluid from the heater 50 and while the 
rollers 12, 14 are being rotated by operation of the motor 24. 
Simultaneously, a pressure is exerted by the fluid pressure cylinder 44 in 
a sufficient amount to insure that the pressure applied between the 
rollers 12, 14 and against the film-sheet combination 66, 64 is in an 
amount which is substantially greater than 50 lbs. per lineal inch along 
the pressure line 13. However, it is likewise necessary to insure that the 
amount of pressure being exerted between the rollers 12, 14 along the 
prressure line 13 against the film-sheet combination 66, 64 is less than 
that which causes structural damage to the sheet 64; to this end, it has 
been found that maintaining the pressure at amounts less than 400 lbs. per 
lineal inch along the pressure line 13 will avoid any structural damage to 
the compressible sheet materials of the type described above. 
As is shown in FIG. 1, a slight compression of the sheet material 64 takes 
place along the pressure line 13 between the rollers 12, 14. It has been 
found that this slight compression of the sheet material 64 effects a more 
complete lamination of the film 66 to the surface of the sheet 64 than has 
heretofore been achieved with lower pressures and multiple rollers pairs 
constructed of compressible materials. While some compression deformation 
of the sheet 64 takes place during passage between the rollers 12, 14, so 
long as the amount of pressure exerted by the fluid pressure cylinder 44 
is controlled as described above to insure that no permanent structural 
deformation or destruction of the sheet material takes place, then the 
desired complete bonding in accordance with the present invention is 
obtained. 
An important aspect of the present invention is the realization of the 
complete lamination of the film 66 to the sheet 64 by utilizing a much 
simpler and less expensive machine than has heretofore been available. 
An alternate form of the present invention is shown in FIG. 3 and described 
with reference thereto. 
THe alternate embodiment, referred to generally as 110, includes a pair of 
parallel, opposed steel cylindrical rollers 112, 114 essentially identical 
to the rollers 12, 14 described above with reference to FIGS. 1 and 2. The 
rollers 112 and 114 are likewise heated in the manner previously 
described, and are driven so as to rotate in the directions indicated by 
arrows associated therewith. 
Another pair of opposing cylindrical steel rollers 116, 118 is provided 
upstream from the first pair of rollers 112, 114. As with the other 
rollers previously described, the rollers 116, 118 are driven in the 
manner shown by the associated arrows and are heated. Both pair of rollers 
112, 114 and 116, 118 are provided with a lever arm-fluid pressure 
cylinder arrangement like that associated with roller 14 of FIG. 1, in 
order to control the spacing between the roller pairs and to apply a 
pressure between about 50 to 400 lbs. per lineal inch along the pressure 
line between the adjacent rollers. 
In use, the machine 110 receives a sheet of material 124 between the first 
pair of rollers 116, 118. A glue reservoir 126 feeds glue onto the hot 
roller 118, which is then pressed evenly across the upper surface of the 
sheet material 124. It will be noted that a slight deformation of the 
sheet material 124 may take place between the rollers 116, 118. 
Thereafter, the sheet material 124 is fed between the second roller pair 
112, 114 while at the same time a laminating film 122 is fed from a supply 
roller 120 across the upper hot roller 114 and across the surface of the 
sheet material 124. Compression of the sheet material 124 takes place 
between the rollers 112, 114 in a manner similar to that described above 
with reference to the rollers 12, 14 of FIGS. 1 and 2, thus insuring a 
complete lamination of the film 122 to the sheet material 124. Thus, the 
laminating film 122 is completely bonded to the surface of the sheet 124 
as desired. 
While it has been described above that both of the rollers 12, 14 shown in 
FIG. 1 may be provided with means for heating the cylindrical surfaces 
thereof, it will be understood by those skilled in the art that where 
relatively thick sheet materials are to be laminated, it is sufficient to 
heat only the side to which the film 66 is to be laminated. On the other 
hand, when relatively thin sheets, such as metals, are to be laminated, 
then it is feasible to utilize both rollers 12, 14 in order to heat both 
sides of the sheet. In those cases where only one roller is to be heated, 
customarily the top roller 14 would be utilized. 
In order to accomplish the lamination of the film 66 as desired, it is 
preferred that the temperature of the surface of the cylindrical rollers 
12, 14 be elevated by the fluid from the heater 50 to a temperature 
substantially above 300 degrees Fahrenheit, and preferably in the range of 
375 degrees to 425 degrees Fahrenheit. It will be understood by those 
skilled in the art that insufficient temperature will result in a poor 
bond, while a temperature which is too high causes damages to the thin 
decorative film 66 which is to be laminated to the surface of the sheet 
64. 
Another important aspect of the present invention will be described with 
reference to FIG. 1. 
Certain types of the compressible wood fiber sheet materials described 
above, notably particle board, fiberboard and porous woods (such as 
plywood) are shipped from the manufacturers with a rough, highly porous 
finish. In the past, it has been difficult to laminate the thin decorative 
films onto these rough, porous surfaces in a satisfactory manner because 
the adhesive is too rapidly absorbed into the material, or the decorative 
film makes a poor bond to the rough finish, or both. 
It has been found that successful lamination of these films onto materials 
having a rough, porous finish may be obtained by first running such sheet 
materials through the heated incompressible pressure rollers 12, 14 of 
FIG. 1 prior to the step of laminating the decorative film thereon. The 
resulting intermediate product has a smooth, calendared finish which is 
virtually non-porous with respect to the starting sheet material. While 
the effect of this heat and pressure treatment on the rough, porous sheet 
material during passage through the rollers 12, 14 is not completely 
understood, it is believed that the heat causes the naturally occurring 
resins in the sheet material to become amorphous at the sheet surface, 
while the pressure of the rollers 12, 14 serves to smooth the amorphous 
resins which are immediately hardened after passage between the rollers. 
In any event, the resulting output of sheet material is extremely smooth 
and non-porous with respect to the input sheet. 
The effect of this initial treatment on the porous-finish sheet materials 
provides two important advantages. First, it has been found that the 
subsequent lamination of a thin decorative film (such as the film 66 in 
FIG. 1) onto a sheet initially treated as described above results in a 
much more satisfactory lamination of that film. Second, and most 
importantly, it has been found that considerably less adhesive is required 
with a sheet treated in this manner. Further, it has also been found that 
aqueous-based adhesives may be substituted for the solvent-based adhesive 
previously used for these purposes.