Film winding apparatus and method

An apparatus and method for winding thin films. Boundary air is discharged and the layers are compressed by a flexible, bowed idler roller located between a winding roll and a backup drive roll. High quality rolls free from wrinkles are produced.

BACKGROUND 
This invention relates generally to the manufacture of thin film and, more 
particularly, to the winding of such film into rolls of high quality. 
Equipment for winding rolls from a continuous length of film is available 
and in use. It is known that bowed rolls and/or spreader bars can be used 
in advance of the windup to flatten the film. Although such devices spread 
the film in transport, additional defects are introduced in the actual 
winding process. For example, as film is advanced to a roll, boundary air 
is entrapped and compressed slightly between the outside film layers and 
moves to regions between high spots or gage bands. This compressed air 
increases the diameter of the roll slightly where the film layers are 
thinnest. Resulting bubble-like areas reduce the laydown width. When the 
air bleeds to atmosphere, the affected film layers fold into wrinkles in 
the machine direction (MD). It is difficult, if not impossible, to avoid 
prominent, unacceptable wrinkles when winding ultra-thin film according to 
standard methods. Such wrinkles have an adverse effect on yield insofar as 
they present difficulties in achieving uniformity in subsequent coating, 
metallizing and laminating steps. 
SUMMARY 
Film has been wound into rolls of high quality on an apparatus which 
includes a winding roll, a drive roll and a flexible, bowed idler roller 
between and in contact with the winding and drive rolls. The idler roller 
preferably is mounted between pivoted arms and means are provided for 
adjusting the arms to flex and thereby bow the roller. Alternatively the 
idler roller may be mounted for linear movement on a mount having means 
for adjusting the orientation of the bow.

DESCRIPTION 
Referring to FIG. 1, the apparatus into which the improvements of the 
present invention have been incorporated includes a stand for a mill roll 
9. Film F from roll 9 advances over freely rotatable rolls 10, 11, 12 and 
pull rolls 13, 14, 15 to knife roll 16 where it is slit by a bar knife 17. 
The slit film passes over pull roll 18. Slit halves f pass over backup 
drive rolls 19, 20 and advance tangentially to winding rolls 21, 22. Such 
a tangential approach provides a hydrostatic air cushion which supports 
each film f prior to laydown. After substantial wraps on the winding 
rolls, the cushioned films reach solid, flexible, bowed idler rolls 23, 
24. In the illustrated embodiment, there are wraps of about 270.degree. 
before film f reach idler rollers 23, 24 which have diameters 
substantially less than the diameters of the winding and drive rolls. Each 
idler roller is located between a drive roll and a winding roll and has 
its rotational axis offset from the axes of those rolls. As shown, the 
winding rolls and idler rollers are swingably mounted on arms. Each 
winding roll is biased against and is surface driven by its idler roller 
which, in turn, is driven by its drive roll. The manner in which the idler 
rollers are first bowed and then twisted in the direction of advance for 
the film is described below with reference to FIGS. 4-7. The concentrated, 
bowed roll point of the relatively small rollers 23, 24 at laydown is 
surprisingly effective in blocking and discharging boundary air. At the 
same time, they spread films f on rolls 21, 22. 
As shown in FIGS. 2 and 3, rear drive roll 20 is rotatably driven by a 
motor driven belt 26 and coupled with front drive roll 19 by spur gears 
28. In addition, motor driven belts 30, 32 are coupled to winding rolls 
21, 22. Both the winding and the drive rolls are rotatably driven in order 
to establish and maintain a minimum level of web feed tension at the idler 
roller. 
Winding roll 21 is rotatably mounted between arm assemblies 34, 36 and rear 
roll 22 between arm assemblies 38, 40. The arm assemblies are fixed to 
shafts 42, 44 and torque is applied to those shafts, for swinging rolls 
21, 22 toward and away from idler rollers 23, 24, by hydraulic, vaned, 
rotary actuators 46, 48. The actuators furnish enough rotary power to 
maintain the desired levels of pressure on the idler rollers. Rolls 21, 22 
can, of course, be removed from the arm assemblies for the donning of 
empty cores and the doffing of cores with rolls of film thereon. 
Idler roller 23 is rotatably mounted between arms 50, 52 and the latter are 
attached to adjusting rolls 54, 56. Arm 50 and roll 54 can be rotated by 
hand wheel 58 which is coupled to a bracket 60 through a shaft 62 and a 
chain 64. Between the reaches of chain 64, there is a connecting link 66 
(FIG. 2). Arm 52 and roll 56 can also be adjusted, through a link and 
chain drive, by a hand wheel 68 (FIG. 3). Similarly, the pivot arms for 
idler roller 24 and the split rolls to which they are attached can be 
adjusted by hand wheels 70, 72. 
The manner in which the idler rollers are flexed, bowed and then twisted in 
the direction of advance is shown in FIGS. 4A, 4B and 5. Hand wheels 70, 
72 are turned to bring idler roller 24 into engagement with the enlarged 
portion of drive roll 20 and then turned further to bow the offset roller 
24 to the position shown in FIGS. 4A and 5. When winding roll 22 is biased 
against roller 24, by rotary actuator 48, the roller is twisted upwardly 
to the position shown in FIG. 4B, producing a compound bow which, in 
effect, spring loads the roller against the winding roll. 
Referring now to FIGS. 6 and 7, it will be seen that adjusting roll 54 is 
coupled to bracket 60 through a gearbox 74. Bracket 60 is attached to a 
ring 76 which is rotatable on box 74. Similarly, adjusting roll 56 is 
coupled to a bracket 77 through a gear box 78. Adjusting rolls 54, 56 are 
relatively rotatable on a support tube 79. Details of the manner in which 
one end of roller 23 is mounted for rotation in a housing 80 and the 
housing is attached to the thin, flat arm 50 are shown in FIG. 7. There is 
an identical housing 80 coupling the other end of roller 23 to arm 52. 
Between each housing and the legs of a yoke 82, there is a pin 84. Flexing 
and bowing of idler roller 23 is facilitated by rotational movements about 
pins 84 and slight twisting movements of flat arms 50, 52. Idler roller 24 
is flexed and bowed by adjustments of rolls 86, 88 (FIG. 2) through gear 
boxes 90, 92, chains 94, 96 and hand wheels 70, 72. 
In addition to the manual adjustments of idler rollers 23, 24, the flexible 
bearing arrangements shown in FIGS. 6 and 7 permit the operating bow in 
each idler roller to change in response to eccentricities between the 
driving and winding rolls and/or in response to variations in thickness of 
the film. The thicker lanes at gage bands lead to slight twisting of an 
idler roller into adjoining areas where boundary air would still 
accumulate and form bubbles. Thus, boundary air is blocked and discharged 
at laydown. In addition, the high contact pressure at the narrow footprint 
of the idler roller forces areas of film in the thicker lanes into closer 
proximity than the thinner areas by compressing the interface regions 
occupied by surface asperities. These cumulative effects of the 
self-adjusting idler rollers disclosed herein have led to the production 
of high quality rolls free from wrinkles. Furthermore, the quality of the 
wrinkle free, slit rolls does not degrade with time. 
The apparatus is readied for slitting and rewinding by threading film F 
from mill roll 9 around rolls 10-16 and raising the blade of bar knife 17 
to start a slit. Then, enough film is advanced beyond roll 16 to present, 
after a transverse cut by the operator, separate films f of sufficient 
length to reach pretaped cores on winding rolls 21, 22. With the latter 
pressing against idler rollers 23, 24, rolls of films f are wound. The 
concentrated roll prints of the relatively small idler rollers 23, 24 on 
winding rolls 21, 22 block and discharge boundary air. Furthermore, the 
flexible resilience of those rollers and the flexibility of their pivotal 
mounts leaves them free to adjust automatically to variations in the 
surfaces of rolls as they are being wound. 
In an operable embodiment, the idler roller was fabricated from a rod of a 
hardened steel alloy. The working surface was polished, had a diameter of 
0.03 meter (m.), a working surface 0.96 m. in length and a bow span of 
1.33 m. The enlarged portion of the driving roll was 0.81 m. in length and 
0.159 m. in diameter. The ratio of operating diameters, driving roll to 
idler roller, was 5.3. The driving roll was fabricated from a hardened 
steel alloy and its working surface covered with a tough, abrasive 
resistant, elastomeric finish having a durometer hardness of 65-70. Rotary 
actuators 46, 48 were Rotac fluid power rotary actuators, Model No. 
RN-63-RV, Ex-Cell-O Corp., Greenville, Ohio. 
FIGS. 4A, 4B and 5 show a preferred method of operation of the apparatus of 
this invention. 
In this method, the flexible idler roller 24 is moved into a position so 
that it is bowed in a direction outwardly from the surface of the drive 
roll 20, as seen in FIG. 5. As thus positioned, when the idler roller 24 
and the winding roll 22 are brought into engagement with each other, the 
bow in the roller 24 will be twisted in the direction of film movement and 
greater forces will be placed on the center portion of film being wound 
onto the winding roll 22 than at its edges. 
More specifically, the flexible idler roller 24 is supported at each end, 
and to cause it to bow as described above, such roller 24 is first moved 
into initial contact with the surface of the drive roll 20 and then is 
moved further so that the ends of the roller 24 are positioned below the 
plane of the surface of the drive roll 20, as seen in FIG. 5, whereby the 
flexible roller 24 is bowed outwardly from the surface of such drive roll 
20. 
The idler roller 24 may be pivotally moved into engagement with the drive 
roll 20, see FIG. 4A, or the drive roll may be pivotally moved into 
engagement with it, as shown in FIG. 9B. Further the idler roller 24 and 
winding roll 22 may be moved into engagement with each other by either 
pivotal movement, see FIGS. 4B and 8A, or linear movement, see FIG. 9A. 
FIGS. 8A through 10B show various modifications of this invention. 
More specifically, FIGS. 8A and 8B and 10A and 10B illustrate, 
schematically, a second preferred method of operation of the apparatus 
shown in FIGS. 1-3 and 6 and 7. 
In practicing this method, hand wheels 70, 72 are turned to move the 
flexible idler roller 24 first into contact with the surface S or enlarged 
portion of the winding roll 22 and then turned further to bow the roller 
into the position, as shown in FIG. 10A, in a direction facing outwardly 
from such winding roll. As thus positioned, as will be seen, greater 
forces are placed at the edges of the winding roll 22. Further these 
forces are controllable by the operator depending on the final positions 
of the ends E and E' of the idler roller 24 below the plane of the surface 
S of such winding roll 22. 
After this step has been completed, the drive roll 20 and idler roller 24 
are moved into engagement with each other to twist the roller 24 in the 
direction of film travel and thereby spring load the roller 24 against the 
winding roll 22, as best seen in FIG 10B. By so doing the primary forces 
are brought to bear against the edges of film being wound on the winding 
roll 22 to help spread the film and provide for effective winding. 
This method differs from the method previously described in connection with 
FIGS. 4A, 4B and 5 in which the idler roller 24 is moved against the drive 
roll 20 to bow the roller, after which it is moved into engagement with 
the winding roll 22 to spring load such idler roller 24 against the 
winding roll. By following this method greater forces are brought to bear 
on the center portion of the film, which for certain films and winding 
conditions is to be desired. 
FIGS. 9A and 9B show a modified version of the apparatus of this invention. 
It is similar to the apparatus shown in FIGS. 1-3 and 6 and 7 except the 
flexible idler roller 24 is mounted on a linearly movable mount 100 which 
is coupled to means 101 for moving the flexible roller 24 into engagement 
with the winding roll 22 and into the position shown in FIG. 10A. A 
suitable device for accomplishing such linear movement of the flexible 
roller 24 is shown in U.S. patent application Ser. No. 559,375, filed Dec. 
8, 1983, the teachings of which are incorporated by reference herein.