U.S. patent number 3,762,255 [Application Number 05/190,908] was granted by the patent office on 1973-10-02 for method and apparatus for piercing thin sheet material.
This patent grant is currently assigned to Union Carbide Corporation. Invention is credited to David Guernsey Clash, Theodore Frederick Kozak.
United States Patent |
3,762,255 |
Clash , et al. |
October 2, 1973 |
METHOD AND APPARATUS FOR PIERCING THIN SHEET MATERIAL
Abstract
A method and apparatus for piercing thin sheet material, such as
plastic film, is provided wherein the sheet material is passed
between a piercing member having a plurality of independently
resilient protrusions extending therefrom and a backing member
having a retiform exterior surface, said piercing member or said
backup member being moved relative to the other member, thereby
causing said resilient protrusions to follow said retiform surface
and selectively pierce said film.
Inventors: |
Clash; David Guernsey (Fairview
Park, OH), Kozak; Theodore Frederick (Peekskill, NY) |
Assignee: |
Union Carbide Corporation (New
York, NY)
|
Family
ID: |
22703287 |
Appl.
No.: |
05/190,908 |
Filed: |
October 20, 1971 |
Current U.S.
Class: |
83/309; 83/348;
83/678; 83/660 |
Current CPC
Class: |
A41B
17/00 (20130101); B26F 1/20 (20130101); B29D
19/04 (20130101); A61F 13/00995 (20130101); Y10T
83/9408 (20150401); Y10T 83/4844 (20150401); Y10T
83/4731 (20150401); Y10T 83/9314 (20150401); A61F
2013/00251 (20130101); A61F 2013/00859 (20130101) |
Current International
Class: |
A41B
17/00 (20060101); A61F 13/00 (20060101); B26F
1/00 (20060101); B29D 19/04 (20060101); B26F
1/20 (20060101); B29D 19/00 (20060101); B26f
001/18 (); B27f 001/24 () |
Field of
Search: |
;83/30,2,349,309,542,678,660,348 ;264/154,156,DIG.47,DIG.70
;225/93,97 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Meister; J. M.
Claims
What is claimed:
1. An apparatus for introducing a plurality of apertures in a film
comprising a piercing member having a plurality of independently
resilient protrusions extending therefrom, a backup member having a
retiform exterior surface constituting camming tracks for said
protrusions, support means for said piercing member, means to
impart relative motion between said backup member and said piercing
member, and means urging said piercing member and said backup
member into adjacency thereby causing said protrusions to track in
said camming tracks during relative motion between said piercing
member and said backup member.
2. The apparatus in accordance with claim 1 wherein said piercing
member is a metal comb.
3. The apparatus in accordance with claim 1 wherein said piercing
member is a wire brush.
4. The apparatus in accordance with claim 1 wherein said piercing
member is a metal strip having a plurality of substantially
parallel slits extending from one edge thereof in the direction of
the opposite edge thereby defining said protrusions.
5. The apparatus in accordance with claim 1 wherein said backup
member has an undulant exterior surface.
6. The apparatus in accordance with claim 1 wherein said backup
member is a wire screen.
7. The apparatus in accordance with claim 1 wherein said backup
member is in the form of an endless belt which is driven
longitudinally with respect to said piercing member.
8. The apparatus in accordance with claim 1 wherein said backup
member is secured to a rotatable drum.
9. An apparatus for introducing a plurality of apertures in a
thermoplastic film comprising a piercing member having a plurality
of independently resilient teeth extending therefrom, a backup
member which is a wire screen secured to a drum, drive means in
combination with said drum to rotate said drum relative to said
piercing member, and support means for said piercing member
maintaining at least a plurality of the teeth of said piercing
member in adjacency with said screen such that said teeth will
individually track the undulations of said screen during rotation
of said drum and selectively perforate a film positioned on said
drum.
10. A method of introducing a plurality of apertures in a film
comprising supplying said film to a perforating area, passing said
film between the nip of a plurality of resilient teeth and a
retiform surface against which said teeth are held in adjacency at
said perforating area and moving said film through said perforating
area in a manner such that said teeth follow said retiform surface
perforating said film when the teeth engage the higher portions of
said surface and allowing said film to pass unperforated when the
teeth engage the lower portions of said surface.
Description
The present invention relates to a method and apparatus for
piercing thin sheet material and more particularly relates to a
method and apparatus for introducing a plurality of small, closely
spaced slits in sheet material.
As used herein and in the appended claims, the terms "film,"
"sheet," "membrane" or "foil" refer, unless a specific composition
is specified, to any thin, relatively flat self-supporting material
such as plastic or rubber film, paper, metal foil, and the like
having a thickness of 0.25 to 10 mils.
It is well known that for many uses it is desirable or necessary to
introduce a plurality of apertures into a film which might
otherwise be substantially water or air impermeable. Examples of
such uses include puncturing refuse bags to speed degradation of
the bag contents, puncturing packaging materials where trapped air
is a problem, puncturing dry cleaning bags to render them safe to
children, and fabricating breathable plastic films for use in place
of nonwovens in uses such as disposable hospital linens, and the
like.
One use which could employ a plurality of perforations in two
distinct parts of the same product is a surgical dressing or
bandage. Plastic-backed adhesive bandages have for some time
employed a plurality of holes in the portion of the plastic backing
adjacent to the absorbent dressing. Such holes provide ventilation
to permit aeration of the wound. More recently, small strips of
thermoplastic film have been provided on the side of the absorbent
dressing which is positioned adjacent to the wound. Absorbent
dressings, which have traditionally been fibrous materials, tend to
stick to a wound upon healing and tearing away such a dressing can
reopen a partially healed wound upon removal of the bandage. The
use of a thermoplastic film adjacent to the wound greatly decreases
the possibility of the bandage sticking to the wound and therefore
promotes easy removal of the bandage from the wound. In order to
permit the secretions from the open wound to reach the absorbent
dressing it has been necessay to provide the thermoplastic film
with apertures very similar to the ventilation holes formed in the
plastic backing of the bandage. Perforate dressings of this type
are described, for example, in U.S. Pat. No. 3,543,750.
Copending U. S. application Ser. No. 73,185 filed Sept. 17, 1970
discloses yet another use for a thermoplastic sheet having a
plurality of perforations therein. A disposable baby diaper
construction is disclosed which employs, as the layer adjacent to
the body of the baby, a thermoplastic film having a plurality of
valvular openings therein which permit passage of urine from the
baby to an absorbent backing material while retarding flow in the
opposite direction. The skin of the baby is thereby kept drier than
has heretofore been possible.
It has previously been suggested to manufacture perforate films
through the use of punching dies or by localized heating of
thermoplastic films through the use of heated pins, dielectric
methods or heated gases. More recently it has been suggested that
the film be initially cast from an organosol onto an open-mesh grid
pattern such that the resulting film will have preformed holes or
incorporating into the film a soluble powder which is subsequently
dissolved.
Each of these methods is subject to one or more disadvantages in
use such as wasted material in dye punching and using soluble
materials increased processing time in heating or high cost for
heating or preforming holes.
It is an object of the present invention to provide a simple method
and apparatus for piercing films.
It is a further object of the invention to provide an inexpensive
and efficient apparatus for the piercing of films which aparatus
can be adapted to accommodate various thicknesses of film and which
can be readily modified to change the size, shape, and placement of
the perforations.
It is a further object to provide a method and apparatus for
introducing valvular openings into an otherwise liquid impermeable
thermoplastic film.
These and other objects are accomplished by a method and apparatus
for perforating films employing the passage of the film between a
piercing member having a plurality of protrusions extending
therefrom and a backup member having a retiform exterior surface
against which the protrusions are resiliently held.
The apparatus of the invention comprises only four basic
components: a piercing member, a backup member, a drive means to
impart relative motion between said piercing member and said backup
member, and means urging said piercing member and said backup
member into adjacency.
The backup member should have a retiform exterior surface, which,
as used herein and in the appended claims, means that it should
have high and low portions or hills and valleys when viewed in
cross-section. Preferably, the surface will be undulant, such as
that of a woven wire screen, but to be operative it is necessary
only that parts of the surface of the backup member be either
higher or lower than the median plane of the surface of the
member.
The piercing member should comprise a plurality of resilient
protrusions such as a comb having a plurality of independently
resilient teeth.
The invention will be more particularly described with reference to
the accompanying drawings in which:
FIG. 1 is a diagrammatic side elevational view of an apparatus in
accordance with the present invention;
FIG. 2 is a perspective view of the piercing member-backup member
combination of FIG. 1 with the film removed for the purpose of
better illustrating the apparatus;
FIG. 2a is an enlarged view of section 2a of FIG. 2; and
FIG. 3 is a perspective view of a film slit by the apparatus of
FIG. 1.
FIG. 4 is an alternate embodiement wherein the backup member is in
the form of an endless belt;
FIG. 5 is an alternate embodiement wherein the piercing member is
in the form of a comb;
FIG. 6 is an alternate embodiement wherein the piercing member is
in the form of a wire brush.
Referring in detail to the drawings there is shown an apparatus for
piercing film such as a thermoplastic film 10 by passing the film
between a piercing member 12 and a backup roll 14 which will each
be described in greater detail hereinafter.
Thermoplastic film 10 may be supplied to the apparatus of the
invention directly from an extruder or from a supply roll, not
shown. The film is positively carried through the apparatus by
being passed between the nip of the backup roll 14, which is driven
in a clock-wise direction by a motor 11 through a drive mechanism
13, and a pressure roll 16. A pair of nip rolls 18, 20 and an idler
roller 22 control the tension of the films as it is being passed
between the piercing member 12 and the backup roll 14.
The backup roll 14, in the embodiment of the invention shown in
FIGS. 2 and 2a, is a 6 inch diameter steel drum 24 having a
stainless steel wire screen 26 encircling the central portion of
its outer circumference.
The piercing member 12 of FIGS. 2 and 2a is a strip of tempered
spring steel having a plurality of parallel slits 28 cut therein to
form resilient ribs 30 extending from a continuous steel backbone
32. The backbone 32 is secured in a holder 34 which is supported by
the frame (not shown) of the apparatus and is adjustable to control
the contact angle and contact pressure between the ribs 30 and the
wire screen 26.
As the backup roll 14 moves the film 10 under the piercing member
12, resilient ribs 30 individually follow the undulations of the
wire screen 26. The film is perforated when the ribs pass over
raised portions of the screen, since the film is tightly pressed
against the wire by the metal edges of the ribs. When the ribs
contact the valley portions of the screen, the contact pressure
between the ribs and the wire is greatly reduced and the film is
not pierced by the ribs. The resulting pierced film 36 will have
perforations 38 (FIG. 3) which correspond to each of the raised
portions of the wire screen. If the film is wider than the wire
screen 26, unperforated borders 40, 42 will be formed along the
sides of the film. The same result is achieved if the piercing
member 12 is narrower than the wire screen 26.
Using a 10 inch wide, 9 .times. 9 mesh screen formed from 0.023
inch stainless steel wire secured to a 15 inch wide, 6 inch
diameter drum which was rotated at a speed, measured at the
circumference of the drum, of 54 feet per minute the 10 inch
central portion of a one mil polyethylene film measuring 14.5
inches in width was continuously pierced by a piercing member
formed by cutting 1.5 inch deep slits in a strip of tempered spring
steel 10 inches wide and 0.010 inch thick. The slits were spaced
0.17 inch apart and formed a piercing member which consisted of a
continuous backbone having 54 resilient ribs extending therefrom.
The resulting pierced film contained uniform slits of a pattern
similar to that shown in FIG. 3 of the drawings.
In operation, the retiform surface of the backup member acts as a
series of camming tracks for the protrusions of the piercing
member. The support for the piercing member is arranged in a manner
such that, upon relative longitudinal movement between the piercing
member and the backup member, the individual protrusions of the
piercing member track the surface of the backup member. Due to
their resiliency the protrusions follow the hills and valleys of
the backup member exerting greater force against the hills than
against the valleys. When a film is positioned between the piercing
member and the backup member during this tracking, the film is
selectively perforated with the portions of the film covering the
hills being perforated while the portions covering the valleys
remain unperforated.
From the above it will be obvious to those skilled in the art that
various combinations of piercing members and backup members can be
used to obtain a wide variety of film aperture sizes, shapes and
patterns within the scope of the present invention, and that by
modifying the mesh or type of screen used and placement or size of
ribs in the piercing member the apparatus of the present invention
can be used to form various perforation patterns in different types
and thicknesses of film. Variations in speed of piercing, the angle
of and pressure exerted by the piercing member, and drawing the
film from the piercing zone under tension will all be useful tools
in obtaining preferred films in accordance with the present
invention for particular uses.
Referring to the types of piercing members useful in the apparatus
of the present invention, it will be apparent to those skilled in
the art that various materials can be substituted for the slit
spring steel member described above. For example, spring steel ribs
welded to a backbone, a wire brush 58, as shown in FIG. 6, or even
razor blades will be useful in combination with various backup
rolls to obtain a variety of perforation patterns. A comb 56, as
shown in FIG. 5, comprising a backbone having a plurality of teeth
extending therefrom will also be useful. Likewise, the ends of the
ribs or teeth of the piercing member may be sharpened, pointed,
flattened, rounded or separated to obtain various piercing
effects.
The backup roll will also be susceptible to change to accommodate
the various types of piercing members and obtain different
perforation patterns. The retiform surface may be provided by
embossing, etching, knurling or perforating a metal sheet or roll
and the backup member may be in the form of a continuous belt 52,
as shown in FIG. 4, passing around rollers 48 and 50 rather than
the roll described or a screen or metal sheet secured to continuous
belt or roll.
Likewise, from the above it will be obvious that while the present
invention has been set forth in some detail and described with
particularlity, it is susceptible to changes, modifications and
alterations without departing from the scope and spirit of the
invention.
* * * * *