U.S. patent number 3,850,462 [Application Number 05/358,386] was granted by the patent office on 1974-11-26 for stripping of thin films.
This patent grant is currently assigned to Yarsley Research Laboratories Limited. Invention is credited to John Norman Cheetham, Ratilal Lalji Shah.
United States Patent |
3,850,462 |
Cheetham , et al. |
November 26, 1974 |
STRIPPING OF THIN FILMS
Abstract
Apparatus for stripping a continuous thin film from a support
web on which it has been formed, comprises a pair of closely spaced
driven stripping rolls disposed with their axes horizontal, an
idler roll positioned on either side of the pair of stripping rolls
and spaced from and parallel to the adjacent stripping roll, a
take-up roll resting on each stripping roll and its adjacent idler
roll and supported only by them, and means for preventing axial
movement of the take-up rolls while allowing rotational and radial
movement thereof.
Inventors: |
Cheetham; John Norman (Ashtead,
EN), Shah; Ratilal Lalji (London, EN) |
Assignee: |
Yarsley Research Laboratories
Limited (Chessington, Surrey, EN)
|
Family
ID: |
10161749 |
Appl.
No.: |
05/358,386 |
Filed: |
May 8, 1973 |
Foreign Application Priority Data
|
|
|
|
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May 8, 1972 [GB] |
|
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21368/72 |
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Current U.S.
Class: |
242/530; 242/538;
242/542.2 |
Current CPC
Class: |
B65H
41/00 (20130101); B65H 18/145 (20130101); B65H
18/16 (20130101) |
Current International
Class: |
B65H
18/16 (20060101); B65H 18/14 (20060101); B65H
41/00 (20060101); B65h 017/08 () |
Field of
Search: |
;242/66,67.1R,67.3R,67.5,65 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Huckert; John W.
Assistant Examiner: McCarthy; Edward J.
Attorney, Agent or Firm: Bacon & Thomas
Claims
What is claimed is:
1. Apparatus for stripping a continuous thin film web from a
support web, comprising a pair of closely spaced stripping rolls
having rotational axes in a horizontal attitude and parallel with
each other, drive means operatively coupled to said stripping rolls
for driving them in opposite rotational directions, a pair of
freely rotatable idler rolls one positioned on one side of said
pair of stripping rolls and the other positioned on the other side
of said pair of stripping rolls, each idler roll being parallel
with and spaced from an adjacent one of said stripping rolls, a
pair of take-up rolls, each resting on a respective one of said
stripping rolls and its adjacent idler roll, whereby each said
take-up roll is adapted to be driven by its contact with said
stripping roll to accumulate a roll of one of said webs and to
rise, relative to said stripping roll and associated idler roll as
said web accumulates thereon, and means preventing axial movement
of said take-up rolls relative to said stripping and idler
rolls.
2. Apparatus as set forth in claim 1, wherein said idler rolls
comprise spindles and the ends of the spindles of said idler rolls
are mounted in horizontally disposed slide means whereby the
separation between each said idler roll and its adjacent stripping
roll can be varied while maintaining said idler roll parallel to
said stripping roll.
3. Apparatus as set forth in claim 1, wherein said drive means is
directly coupled to one of said stripping rolls and the other said
stripping roll is operatively coupled to the first said stripping
roll through transmission means comprising gearing and finely
adjustable slipping clutch means.
4. A method of stripping a continuous thin film web from a support
web, which comprises the steps of feeding the support web and
adherent thin film web into the gap between a pair of closely
spaced, driven stripping rolls having their rotational axes in a
horizontal attitude and parallel with each other, the gap between
said stripping rolls being just greater than the combined thickness
of the support web and the thin film web, dividing the support web
and the thin film web in said gap, taking the thin film web over a
part of one of said stripping rolls and on to a first take-up roll
which is supported by said stripping roll, and taking the support
web over a part of the other said stripping roll and on to a second
take-up roll which is supported by said other stripping roll, said
first and second take-up rolls being rotated by their contact with
their respective supporting stripping rolls.
5. A method as set forth in claim 4, wherein the support web makes
contact with said other stripping roll upstream of said gap between
said stripping rolls.
Description
This invention is concerned with the stripping of continuous thin
film from the support web on which it is formed.
It is known to make thin film of from 0.5 to 6 micron thickness of
various polymers, such as cellulose esters, cellulose ethers,
polystyrene, polyurethane, polysulphones, and polycarbonates, by
casting a solution of the polymer on to a moving support web and
drying the coating obtained to remove the solvent and leave a thin
film of the polymer on the support web. The support web, carrying
the thin film, is then commonly reeled with an interleaved paper
web to protect the thin film. The thin films thus obtained are used
for the production of capacitors after they have been metallised on
one surface and for this purpose they must be stripped from the
support web either before or after they have been metallised.
Whether or not the thin film is metallised, it is a delicate
material in which longitudinal creases are readily formed when it
is under tension. It is difficult to avoid the formation of such
longitudinal creases during stripping of the thin film from the
support web using conventional stripping procedures and equipment,
and we have now developed an improved stripping apparatus and
procedure which substantially reduces this difficulty.
The apparatus according to the invention comprises a pair of
closely spaced stripping rolls disposed with their axes horizontal
and which, in operation, are driven, an idler roll positioned on
either side of the pair of stripping rolls and spaced from and
parallel to the adjacent stripping roll, a take-up roll resting on
each stripping roll and its adjacent idler roll and supported only
by them, and means for preventing axial movement of the take-up
rolls while allowing rotational and radial movement thereof.
The method of stripping according to the invention comprises
feeding the support web and adherent thin film upwardly into the
gap between the pair of stripping rolls, the gap between the rolls
being just greater than the combined thickness of the support web
and the thin film, taking the thin film over a part of one of the
stripping rolls and on to the take-up roll supported by that
stripping roll, and the support web over a part of the other
stripping roll and on to the other take-up roll, the take-up rolls
being rotated by their contact with the driven stripping rolls.
In order that the invention may be more fully understood, a
preferred embodiment of stripping apparatus, and the operation
thereof, will now be described, by way of example only, with
reference to the accompanying drawings, in which:
FIG. 1 is a diagrammatic elevation of the apparatus;
FIG. 2 is an elevation, on an enlarged scale, of part of the
apparatus of FIG. 1 showing the means for mounting one of the idler
rolls and one of the take-up rolls, and
FIG. 3 is a section through the spindles of the stripping rolls of
FIG. 1 showing the drive mechanism therefor.
The apparatus comprises a pair of horizontally disposed closely
spaced stripping rolls 10, 11 which are mounted so that the gap
between them is adjustable and it is adjusted to a distance just
greater than the combined thickness of the support web (which is
typically 25 microns thick) and the thin film (which is typically 2
microns thick). On either side of the stripping rolls 10, 11 are
horizontally disposed idler rolls 12 and 13, respectively, which
are spaced from and parallel to the adjacent stripping roll. The
ends of the spindles 23 of the idler rolls 12 and 13 are mounted in
horizontal slides, as shown for idler roll 13 in FIG. 2 (the
mounting of idler roll 12 being the same). Referring to FIG. 2, a
horizontal slide 24 is provided to support the spindle 23 at each
end of roll 13, the spindle 23 passing freely through a horizontal
slot 25 in the slide and being received in a bearing 26 mounted
within a bearing housing 27. The housing 27 is slidably mounted
within a recess 28 on the outer face of the slide 23 and its
position along the recess is adjustable by means of a set screw 29
which passes through the end of the slide 24. By means of this
arrangement, the separation between the idler rolls 12 and 13 and
the adjacent stripping rolls 10 and 11, respectively, can be varied
as required by adjustment of the set screws 29 while maintaining
each idler roll parallel to its adjacent stripping roll.
A take-up roll 14 is supported by the stripping roll 10 and the
idler roll 12 and a take-up roll 15 by the stripping roll 11 and
the idler roll 13. As shown in FIG. 2, the ends of the spindle 30
of the take-up roll 13 are a loose fit between the sides of a
vertically disposed channel element 31 provided at each end of the
roll 13. The channel elements 31 at each end of the roll 13 serve
to prevent axial movement of the roll 13, but permit rotational and
vertical radial movement of the roll. The take-up roll 14 is
mounted in the same way.
Referring to FIG. 3, the spindle 32 of the stripping roll 11 has
secured thereto a gear 33 and a pulley 34 which receives a belt
drive from a suitable variable speed motor (not shown). The gear 33
intermeshes with a gear 35 which is freely rotatable on the spindle
36 of stripping roll 10. The gear 35 forms part of a slipping
clutch assembly generally designated 37, the assembly additionally
comprising a back plate 38 secured to the spindle 36 by screw 39,
and a felt pad 40 on one side of the gear 35, and a felt pad 41, a
pressure plate 42, a clutch spring 43, and an adjusting nut 44 on
the other side of the gear 35. As will be appreciated the ability
of the clutch assembly 37 to transmit torque from the gear 33
through the gear 35 can be finely adjusted by adjustment of the nut
44.
The rotational speed of the stripping roll 10 can thus be finely
adjusted relative to the speed of the stripping roll 11 and the
tensions of the separated thin film and support web to be correctly
balanced. By this arrangement, jerkiness in the stripping and
non-uniform stretching or breaking of the thin film which might be
caused by small differences in the peripheral speeds of the
stripping rolls 10 and 11 or inequality in the drives transferred
to the take-up rolls 14 and 15 due to variations in the film
thickness or to slip, are substantially prevented. This arrangement
also enables extensible thin films to be stripped and wound
successfully.
The apparatus further comprises a supply reel 16, the spindle of
which is operatively connected to a friction clutch unit (not
shown) so that tension is applied to the support web taken off the
reel 16. The friction clutch unit has the same construction as the
slipping clutch assembly 37 shown in FIG. 3 except that the gear 35
is made fast with the mounting of the reel 16 so that the gear 35
cannot rotate. The reel 16 supports a take-up roll 17, the ends of
the spindle of which are located within vertically disposed channel
elements (not shown) similar to the element 31 shown in FIG. 2,
which allow the roll 17 to rotate freely and also to move up and
down, but do not allow it to move horizontally. Positioned below
the level of the supply reel 16 and the stripping rolls 10, 11 are
idler rolls 18, 19 and 20. All the rolls 10 to 20 have a length
greater than the width of the support web and they are all aligned
transverse to their axes.
At the commencement of the stripping operation, the supply reel 16
carrying a supply of support web with adherent thin film and an
interleaved paper web is positioned as shown and connected to the
friction clutch. The paper web is manually wound on to the take-up
roll 17 and the carrier web 21 is passed under the idler roll 18,
over the idler roll 19, under the idler roll 20 and up into the gap
between the stripping rolls 10 and 11. The carrier web with the
adherent thin film is passed, by hand, over the stripping roll 11
and wound on to the take-up roll 15 for a few turns. A light cut is
then made across the thin film (which is on the outside of the
stripping roll 11) at the point indicated by 22 so as to cut only
the thin film, the thin film is peeled back, passed over the
stripping roll 10 and wound for one or two turns on to the take-up
roll 14. Drive to the stripping rolls 10, 11 can then be started at
a slow speed and then increased to the normal working speed.
As will be seen, stripping takes place in the gap between the
stripping rolls 10 and 11, the support web passing over the roll 11
to be taken up on take-up roll 15 and the thin film passing over
the roll 10 to be taken up on take-up roll 14. Since the take-up
rolls 14 and 15 are supported only by the rolls on which they rest,
they are able to accommodate themselves to changes from true
cylindricality as they are progressively built up, due to small
variations in thickness across the width of the material being
wound on.
The idler roll 20 is so positioned that the support web with
adherent thin film 21 makes contact with the stripping roll 11
upstream of the gap between the rolls 10 and 11. This arrangement
is preferred because it provides a greater length of contact
between the support web and the driven roll 11, the driving force
developed to pull the support web off the supply reel 16 and over
the idler rolls 18, 19 and 20 being dependent on the frictional
contact between the support web and the roll 11.
When the size of the take-up rolls 14 and 15 becomes too large for
the initial separation between the rolls 10 and 12, and 11 and 13
respectively, this separation may be increased by moving the roll
12 or 13 horizontally outwardly as required.
* * * * *