U.S. patent number 3,761,013 [Application Number 05/236,409] was granted by the patent office on 1973-09-25 for double wall package for storing items in bacteria-free condition.
Invention is credited to Samuel J. Schuster.
United States Patent |
3,761,013 |
Schuster |
September 25, 1973 |
**Please see images for:
( Certificate of Correction ) ** |
DOUBLE WALL PACKAGE FOR STORING ITEMS IN BACTERIA-FREE
CONDITION
Abstract
A package is disclosed comprising a double wall, plastic bag
having an access opening covered by a readily removable closure
membrane bonded to the bag by heat seals adjacent the access
opening. Both the bag and the membrane are essentially completely
impermeable to bacteria, but the membrane is highly permeable to
sterilizing vapor in comparison to the plastic bag. The bag
comprises inner and outer plies, portions of which define the
access opening, and other portions of which overlap within the
confines of the access opening. Along any transverse section of the
bag, the combined thickness of the inner and outer plies is
essentially the same, thereby facilitating the fabrication of the
bag out of high temperature plastic, such as polypropylene, which
can withstand steam sterilization temperatures.
Inventors: |
Schuster; Samuel J. (Monterey
Park, CA) |
Family
ID: |
22889381 |
Appl.
No.: |
05/236,409 |
Filed: |
March 20, 1972 |
Current U.S.
Class: |
206/439; 383/66;
383/109; 383/210 |
Current CPC
Class: |
A61M
25/002 (20130101); B65D 33/24 (20130101); A61B
50/30 (20160201); A61B 2050/316 (20160201); A61F
15/001 (20130101); A61M 5/002 (20130101); A61B
42/40 (20160201); A61M 2209/06 (20130101); A61B
2050/314 (20160201); A61B 50/3001 (20160201) |
Current International
Class: |
A61B
19/02 (20060101); A61B 19/00 (20060101); B65D
33/24 (20060101); B65D 33/16 (20060101); A61F
15/00 (20060101); A61B 19/04 (20060101); A61M
5/00 (20060101); B65d 033/16 () |
Field of
Search: |
;229/62,66,62.5
;206/63.2R,63.2A ;150/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rothberg; Samuel B.
Assistant Examiner: Garbe; Stephen P.
Claims
What is claimed is:
1. A package for storing articles in substantially bacteria-free
condition, comprising:
a flexible, plastic bag having a double wall and opposed ends and
an access opening through said double wall, portions of said double
wall overlapping with the confines of said access opening,
substantially all cross-sections of said bag having substantially
the same, uniform thickness, said double wall having a thickness at
least sufficient to render said container essentially completely
impermeable to bacteria; and,
a closure membrane covering said access opening and bonded to said
bag about said access opening, said membrane being manually
separable from said bag and essentially completely impermeable to
bacteria but highly permeable to sterilizing vapor in comparison to
said bag.
2. A package, as defined in claim 1, in which:
said double wall bag includes an inner ply and an outer ply,
portions of said inner ply overlapping within the confines of said
access opening.
3. A package, as defined in claim 1, in which:
said double wall bag includes an inner ply and an outer ply,
portions of said outer ply overlapping within the confines of said
access opening.
4. A package, as defined in claim 1, in which:
said double bag includes an inner ply and an outer ply, a portion
of said inner ply overlapping with a portion of said outer ply
within the confines of said access opening.
5. A package, as defined in claim 1, in which:
said double wall bag includes an inner ply and an outer ply having
the same thickness.
6. A package, as defined in claim 1, in which:
said double wall bag includes an inner ply and an outer ply having
different thicknesses.
7. A package, as defined in claim 1, in which:
said double wall bag is constructed of plastic capable of
withstanding steam sterilization temperatures.
8. A package, as defined in claim 1, in which:
said double wall bag includes an inner ply and an outer ply, said
plies being cohered to eliminate air between said plies.
9. A package for storing articles in bacteria-free condition,
comprising:
a double wall plastic bag consisting of an inner ply and an outer
ply, said plies having a combined thickness sufficient to render
said bag essentially completely impermeable to bacteria, said plies
having longitudinal edge portions and transverse edges, said
transverse edges defining opposed ends of said bag, said plies
being folded along longitudinal fold lines, one pair of said
longitudinal edge portions disposed in spaced-apart relation to
define a longitudinally-extending access opening, the other pair of
said longitudinal edge portions being disposed in overlapping
relation within the confines of said access opening, the combined
thickness of said plies being substantially the same along
substantially all portions of all transverse sections of said bag;
and
a closure membrane covering said access opening, said membrane
being highly permeable to sterilizing vapor in comparison to said
bag but essentially completely impermeable to bacteria, said
membrane and said plies being bonded together by a longitudinal,
continuous heat seal joinder line on each side of said access
opening, said package includng a transverse, continuous heat seal
joinder line adjacent one end of said package to unite said
membrane and said plies and close said end of said package.
10. A package, as defined in claim 9, in which:
said overlapping longitudinal edge portions are portions of said
outer ply.
11. A package, as defined in claim 9, in which:
said overlapping longitudinal edge portions are portions of said
inner ply.
12. A package, as defined in claim 9, in which:
said overlapping longitudinal edge portions are portions of said
inner and outer plies.
13. A package, as defined in claim 9, in which:
said plies are formed of material capable of withstanding steam
sterilization temperatures and said membrane has adequate wet
strength to withstand steam sterilization conditions.
14. A package, as defined in claim 9, in which:
the thickness of said inner ply is the same as the thickness of
said outer ply.
15. A package, as defined in claim 9, in which:
the thickness of said inner ply is different than the thickness of
said outer ply.
16. A package, as defined in claim 9, in which:
said clousre membrane has a tear strength greater than the strength
of said longitudinal heat seal joinder lines so that said membrane
is separable from said bag as a single piece so as to substantially
completely expose said access opening.
17. A package, as defined in claim 9, in which:
said longitudinal heat seal joinder lines terminate a short
distance from at least one of said ends of said package to define
at least one pull tab on said closure membrane to facilitate its
removal.
18. A package, as defined in claim 9, in which:
said closue membrane includes lateral gripping means adjacent at
least one of said longitudinal heat seal joinder lines to
facilitate removal of said membrane.
19. A package, as defined in claim 9, in which:
said plies are transparent and said closure membrane is in the form
of a longitudinal strip substantially narrower than the overall
width of the package to facilitate identification of the stored
article.
20. A package as defined in claim 9, in which:
said package has a longitudinal center line and said access opening
is substantially symmetrical of said center line.
21. A package, as defined in claim 9, in which:
said package has a longitudinal center line and said access opening
is asymmetrical of said center line.
22. A package, as defined in claim 9, in which:
said plies are cohered to eliminate any air between said plies.
23. A package for storing articles in bacteria-free condition,
including:
a transparent, plastic bag essentially completely impermeable to
bacteria and comprising longitudinally coextensive inner and outer
plies of equal thickness, said plies having transverse edges
defining opposed ends of said bag and longitudinal edge portions,
said plies being folded along longitudinal fold lines to define
opposed faces of the bag, one pair of said longitudinal edge
portions disposed in parallel, spaced-apart relation to define a
longitudinally-extending access opening, the other pair of said
longitudinal edge portions being disposed in overlapping relation
within the confines of said access opening, the combined thickness
of said plies being substantially the same along substantially all
portions of all transverse sections of said bag;
a longitudinally-extending, manually removable paper strip covering
said access opening and extending the length of said bag, said
strip being highly permeable to sterilizing vapor in comparison to
said bag but essentially completely impermeable to bacteria, the
overall width of said package being substantially greater than the
width of said strip to make visible the contents of said package
through either face therof, said strip and said plies being bonded
together by a longitudinal, continuous heat seal joinder line on
each side of said access opening, said strip havng a tear strength
in relation to the strength of said longitudinal heat seal joinder
lines sufficient so that said strip is separable from said bag in
one piece; and,
a transverse, continuous heat seal joinder line adjacent one end of
said package uniting said strip and said plies and closing said end
of said package.
24. A package, as defined in claim 23, in which:
said plies are formed of material capable of withstanding steam
sterilization temperatures and said strip has adequate wet strength
to withstand steam sterilization conditions.
25. A package, as defined in claim 23, in which:
said overlapping longitudinal edge portions includes an edge
portion of said outer ply.
26. A package, as defined in claim 23, in which:
said overlapping longitudinal edge portions includes an edge
portion of said inner ply.
27. A package, as defined in claim 23, in which:
said plies are cohered to eliminae air from between said plies.
28. A package, as defined in claim 27, in which:
said plies are cohered mechanically by embosisng said plies.
29. A package, as defined in claim 23, in which:
said longitudinal heat seal joinder lines terminate a short
distance from at least one of said ends of said package to define
at least one end tab on said paper strip to facilitate its removal.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to packages for storing articles
in bacteria-free condition, and particularly to packages which
permit sterilization of the stored particles by a variety of
sterilizing vapors, provide storage for such articles in
bacteria-free condition over extended periods of time and are
easily opened to permit ready utilization of the bacteria-free
articles.
2. Description of the Prior Art
U. S. Pat. No. 3,472,369 issued to the present inventor on Oct. 14,
1969 discloses a package so constructed that the interior of the
package and its contents may be readily sterilized by a sterilizing
agent such as ethylene oxide. The package of the referenced patent
comprises a flexible plastic container or bag having an access
opening covered by a removably-attached closure membrane such as a
paper tear strip. Although both the plastic bag and closure
membrane are essentially completely impermeable to bacteria, and
under normal conditions will not allow entry of bacteria, the
closure membrane is highly permeable to the sterizing agent in
comparison to the plastic bag. The package is fabricated with an
open end for receiving the article to be stored. The article is
inserted in the package, the open end is sealed with a transverse
heat seal and the interior of the package and article are
completely sterilized by sterilizing gas which readily enters the
package through the closure membrane. The sterilizing gas is
withdrawn through the membrane, the article remaining in sterile
condition until ready for use. Retrieval of the sterilized article
is accomplished by pulling back or completely removing the closure
membrane thereby at least partially exposing the access opening
through which the article is removed.
The package of the referenced patent, which is particularly useful
for the storage of disposable articles, meets a combination of
essential requirements which have never before been fulfilled in a
single product. Thus, the package retains its contents in sterile
condition until use (which may take place several months or even
more than a year after sterilization), it is low in cost compared
to the total cost of the package and contents, the contents are
readily visible and, lastly, the package is easily opened while
providing sufficient strength to guard against accidental puncture
or tearing during handling.
The above-described package is readily manufactured on what is
basically a conventional plastic bag-making machine modified in
certain substantial respects to accommodate the fabrication of the
packages described. Briefly, plastic sheet stock is fed in
successive steps and folded along spaced, parallel longitudinal
fold lines, the side edges of the sheet thereby being brought
together either in abutting or overlapping relation to define a
longitudinal access opening. The closure membrane, typically in the
form of a paper strip, may be fed concurrently along the
longitudinal access opening and into contact with the sheet. The
paper strip and the sheet are joined by longitudinal heat seals
applied along both sides of the access opening in timed relation
with the intermittent feed of the plastic sheet and paper strip.
The result is a continuous, flattened, composite tube. A transverse
heat seal is then applied at intervals across the width of the
composite tube to define individual packages which are then
separated from each other adjacent the transverse seal by
mechanical or thermal cutting means. Packages with one open end
ready to receive the article to be stored are thus provided.
The overlapping configuration of the longitudinal side edge
portions defining the access opening has certain advantages most
important of which is that it helps preclude entry of foreign
matter into the interior of the package when the closure membrane
is removed. For example, when the closure membrane is in the form
of a paper strip, minute paper fibers may be dislodged upon removal
of the strip and these fibers can more easily enter the package in
the absence of the overlap described. Moreover, the overlap
prevents contact between the closure membrane and the article
inside.
On the other hand, the use of the overlap presents certain
problems. Thus, when the package is viewed in transverse section
differential thicknesses along the section will be observed. The
degree of differential thickness may be exemplified as follows: if
the plastic sheet and the closure membrane each have a thickness of
4 mils (1 mil equals 0.001 inch) then at the overlap the total
thickness of the package material is 16 mils. In contrast, the
portions of the package adjacent the overlap but within the
confines of the closure membrane have a thickness of 12 mils and
still further, the regions of the package on eithr side of the
closure membrane are only 8 mils thick. Since heat sealing
temperatures increase with material thickness, in order to insure
an effective transverse heat seal with a conventional bar-type heat
sealer a relatively high sealing temperature is required at the
overlap. Such high sealing temperatures, however, sometimes cause
"burn-throughs" in other portions of the package where the
thickness is less. Singeing or burning of the closure membrane may
also result thereby weakening or perforating the membrane at the
affected points. Control of "burn-throughs" has been found to be
extremely critical and difficult to maintain in the context of high
production, especially when plastics requiring higher sealing
temperatures such as polypropylene, saran, nylon, or the like, are
used.
One solution to the foregoing problem is to utilize a
differentially heated transverse bar sealer having higher
temperatures along those portions engaging the thicker sections.
This is not an altogether reliable technique however. Among other
requirements, nearly perfect registration must be maintained at all
times between the differentially-heated portions of the heat sealer
bar and the corresponding regions of the bags being processed.
Thus, to the extent that requirements of commercially feasible
production dictate, this is not currently a practical solution.
The package structure of the prior patent, which may be fabricated
of essentially any flexible, heat-sealable plastic sheet
impermeable to bacteria, including polyethylene, polypropylene,
cellophane, nylon, polybutylene, or the like, is especially adapted
for sterilization of low temperature sterilizing processes such as
the ethylene oxide process which is carried out at about
140.degree. F. Many hospitals and other facilities, however, employ
the autoclaving process by which sterilization is accomplished in
an air-tight chamber filled with pressurized steam at a temperature
well in excess of 212.degree. F. The temperature at which
autoclaving or steam sterilization is carried out does not
adversely affect the higher temperature plastics such as medium to
high density polyethylene, polybutylene, polypropylene, nylon, and
the like, but is much too high for low density polyethylene which
rapidly melts, shrivels or distorts in the autoclaving environment.
Thus, packages of polypropylene or other plastics or plastic
compositions which can withstand steam sterilization temperatures
have the advantage of being sterilizable by a variety of
sterilizing vapors, including ethylene oxide and steam, thereby
greatly extending the usefulness and versatility of such
packages.
Plastics that can withstand steam sterilization temperatures,
however, do not have the excellent heat sealing properties of low
density polyethylene -- the sealing temperatures for a given
thickness must be higher and better regulated to produce
satisfactory seals on a repetitive, production line basis. Thus,
where there is an overlap of sheet material formed of such plastic,
the temperature required (especially if the plastic sheet is
relatively thick) is sufficient to singe or burn the closure
membrane and the thinner plastic sections.
In summary then, those materials, such as polypropylene, that can
withstand steam sterilization temperatures also require higher,
more carefully regulated sealing temperatures and if a relatively
thick sheet of polypropylene is shaped into the overlapping
configuration described in the aforementioned patent, the
temperatures required are so high that the closure material,
typically paper, will be burned. Thus, what is a difficult problem
to overcome with ordinary package configurations becomes even more
difficult with the higher temperature materials.
SUMMARY OF THE INVENTION
The present invention makes possible the utilization of the
desirable overlapping arrangement within the confines of the access
opening yet enables use of heat sealable plastics sucy as
polypropylene, nylon and polybutylene that can withstand steam
sterilization temperatures.
The package of the present inveniton includes a double wall, that
is, a two-ply flexible plastic bag. Each ply may be relatively thin
(for example, 2 mils); in any event, the combined thickness of both
plies is at least sufficient to render the bag structure
essentially impermeable to bacteria. The plies of the double wall
conjointly define an access opening closed by a closure membrane
heat sealed to the bag about the access opening in a manner
facilitating manual removal thereof. The closure membrane, like the
bag to which it is attached, is essentially completely impermeable
to bacteria but, in contrast to the bag material, is highly
permeable to sterilizing vapors such as ethylene oxide, steam, or
the like. The package is closed at one end along a transverse heat
seal joinder line.
According to a significant aspect of the present invention, the
combined thickness of the plies forming the double wall bag is
uniform along all transverse sections of the bag. Thus, if each ply
is constructed of sheet stock 2 mils thick, the combined thickness
of the plies at substantially any point along any transverse
section is 8 mils. The only differential thickness along transverse
sections of the overall package is due to the presence of the
closure membrane. However, this falls within the magnitude of
differential thickness which has been found to be tolerable and
does not materially influence the effectiveness of, or the ability
to apply, the transverse end seals. As a result of the thinness of
the individual wall plies in combination with the uniformity of the
total cross-sectional thickness of the bag, less critical,
substantially lower sealing temperatures may be utilized thus
precluding uneven seals, "burn-throughs," singeing, or like damage
to the bag and/or closure membrane. The use of polypropylene and
other higher temperature plastics thus becomes commercially
practical and makes possible sterilization by virtually any
presently used sterilizing process.
In accordance with one specific, illustrative embodiment of the
invention, the bag includes an inner ply and an outer ply having
longitudinal edge portions defining a longitudinally-extending
access opening. These edge portions are disposed beneath the
closure membrane within the confines of the heat seals joining the
closure membrane to the bag. The longitudinal edges of the inner
ply lie a short distance inwardly of the longitudinal heat seals to
define the access opening; the outer ply, in contrast, has
overlapping longitudinal portions beneath the closure membrane, the
extent of overlap and the length of the overlapping portions being
such that the edges of these portions are contiguous or in
alignment with the edges of the inner ply. In this fashion, a
typical transverse section of the container will have a uniform
thickness along virtually the entire width of the container.
A number of alternative arrangements may be employed. For example,
the outer ply may be provided with the pverlapping portions instead
of the inner ply; or, each of the outer and inner plies may be
provided with portions which overlap. Still other combinations are
possible and some of these will be covered more fully in the
detailed description below.
The foregoing structure lends itself exceedingly well to large
scale, low cost production on conventional packaging machinery
modified in certain material respects to provide consistently high
quality packages.
The article to be sterilized may be inserted manually or by
machine, either as a completely separate, subsequent operation or
as a secondary operation on a machine capable of both forming and
filling the package. The package is thereafter completely sealed
and subsequently the contents may be completely sterilized by a
sterilizing vapor, such as ethylene oxide, steam, or the like, in
accordance with well-established techniques.
According to another aspect of the invention, the faces of the two
plastic plies forming the bag portion of the package may be cohered
mechanically, such as by embossing or rolling the two sheets
together under slightly elevated heat and pressure. Cohesion can be
increased by treating the contacting surfaces with a corona
discharge. Trapped air between the plies is thus avoided and the
production of the package is facilitated because the plies cannot
move laterally relative to each other during processing by the
bag-making machine. The elimination of air between the plies is
important if the package is subjected to a rapid, sterilant-purging
vacuum cycle as part of the sterilization process. Any pair at
atmospheric pressure trapped between the plies will expand during
such vacuum cycle and possibly rupture the bag.
Other features of packages in accordance with the invention include
the use of different, although compatible plastics, transparencies,
and/or thicknesses for the inner and outer plies to achieve
specific objectives for given applications.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects, advantages and features of the invention will be
understood by reference to the following detailed description taken
in conjunction with the accompanying drawings, in which:
FIG. 1 is a partially broken away perspective view of a package for
sterilized items in accordance with the invention;
FIG. 2 is an enlarged, transverse section of the package of FIG. 1,
taken along the plane 2--2, and showing details of the package
structure;
FIG. 2A is a portion of an enlarged, transverse section, such as
shown in FIG. 2, of an alternative embodiment of the package
according to the invention;
FIG. 2B is a portion of an enlarged, transverse section, such as
shown in FIG. 2, of another alternative embodiment of a package
according to the invention;
FIG. 2C is an enlarged transverse section, such as shown in FIG. 2,
of still another alternative embodiment of the package according to
the invention;
FIG. 3 is a perspective view of the package of FIG. 1 showing the
package during opening with the closure membrane partly removed;
and,
FIG. 4 is a perspective view of another package configuration
according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
It is to be noted that in the accompanying drawings the thicknesses
of the plastic sheets forming the bags and that of the closure
membranes have all been greatly exaggerated in order to clearly
show their interrelationship. Further, it will be evident that a
great many combinations of materials, overall package dimensions,
material properties, specific package configurations, and so forth,
fall within the purview of the claimed invention. Only relatively
few specific examples are shown and discussed herein and these
should not be construed as exhaustive.
For purposes of illustrating the background of the invention and
the state of the art, the above-mentioned U. S. Pat. No. 3,472,369
issued to the present inventor on Oct. 14, 1969 is incorporated
herein by reference.
Referring now to FIGS. 1 and 2, packages in accordance with the
present invention may be utilized for the ready sterilization,
storage in sterile condition and easy removal of an article 10.
From a practical standpoint, there is no limit to the kinds of
articles that can be sterilized and stored in packages of the
invention; such articles may typically include surgical and medical
instruments, surgical gloves, garments and related wearing apparel,
pipettes, petri dishes, syringes, swabs scalpel blades and food
items. The dimensions of the package can be tailored to accommodate
the particular article to be sterilized and stored. The disclosed
packages are especially suitable where the article 10 is of a low
cost, disposable nature but all of the advantages of the invention
may be realized regardless of the specific character of the article
to be sterilized and stored in sterile condition for subsequent
use.
Packages such as that shown in FIG. 1 and 2 mainly comprise a
plastic container or bag 12 and a closure membrane 14. The bag 12
is a double wall structure comprising two plies, an outer ply 16
and an inner ply 18. Materials which may be used for the plies 16
and 18 include polyethylene, polypropylene, mixtures of
polyethylene and polypropylene, nylon, polybutylene and other heat
sealable materials.
In comparison to the closure membrane 14, which will be described
more fully later, the combination of the material and the thickness
of each ply 16 and 18 is such that the ply exhibits very little
permeability to sterilizing vapors such as steam, ethylene oxide,
or the like. The extent of impermeability of the plastic to
sterilizing vapor is approximately a linear function of thickness,
that is, increasing thickness increases the impermeability
proportionately in linear fashion. Since heavier gauges, for
example, 2-4 mils, are typically necessary to protect the enclosed
article from damage, permeability of the plastic to the sterilizing
vapor is reduced very substantially. Plies thinner than 2 mils, for
example, 1.5 mils, may be used where strength is a less important
factor.
For most applications, both plies 16 and 18 will be transparent to
facilitate inspection and identification of the contents of the
package but it will be appreciated that either one or both of the
plies 16 and 18 may be translucent, opaque or tinted. Tinting may
be desirable in certain instances to control the entry of
electromagnetic radiation in both the visible and non-visible
portions of the spectrum.
Each ply 16 and 18 is fabricated from a single continuous sheet of
material, the parallel, longitudinal side edges of which are folded
inwardly along spaced, parallel longitudinal fold lines. Thus, the
outer ply 16 has longitudinal edges 20 and 22 and is folded about
the longitudinal fold lines 24. Similarly, the inner ply 18 has
longitudinal edges 26 and 28 and is folded about the longitudinal
fold lines 30. The parallel edges 26 and 28 are spaced transversely
to define a longitudinal access opening 32. The access opening 32
is approximately symmetrical of the longitudinal center line 33 of
the container 12 but it will be appreciated that the opening can be
displaced to one side or the other of the center line. FIG. 4,
discussed further below, depicts an example of such an asymmetrical
arrangement.
In the embodiment of FIGS. 1 and 2, the outer ply 16 is provided
with overlapping portions 34 and 36 closing the access opening 32.
The extent of overlap of the portions 34 and 36 is such that the
edges 22 and 28 are in abutting relationship, or very close to such
relationship. The longitudinal edge 20 of the outer ply 16 and the
edge 26 of the inner ply 18 are nearly in alignment, that is, they
lie approximately in a common vertical plane, the transverse
spacing separating these edges being only that necessary to permit
the passage of the portion of the outer ply 16 leading to the
overlapping portion 36. By inspection of the transverse section of
FIG. 2, it will be seen that along virtually the entire extent of
the section, the total thickness of the bag is the same,
essentially all portions thereof comprising four layers.
The closure membrane 14 comprises a longitudinal strip somewhat
wider than the access opening 32 and its functions are to close the
access opening and form a barrier for bacteria while simultaneously
being highly permeable to the sterilizing vapor in comparison to
the container 12. The closure membrane 14 may be made of
conventional paper 3 to 7 mils thick. Paper is characterized by
several important properties for purposes of this invention. Unlike
plastic, increasing the thickness of paper does not substantially
affect its permeability to sterilizing vapors. On the other hand,
the labyrinth structure of the fibers constituting paper is such
that even modest increases in the thickness of the paper greatly
increases its impermeability to bacteria. A long fiber paper,
having superior wet strength, should be used where the package is
to be subjected to a steam sterilization process.
The paper strip can be provided with a thin polyethylene coating
(not shown), such coating being in contact with the outer ply 16.
The thickness of the polyethylene coating would preferably be of
the order of 1/2 mil which is insufficient to impede the passage of
sterilizing vapor but nevertheless would provide a sufficient
thickness to facilitate the joinder between the paper strip 14 and
the bag 12. Alternatively, direct heat sealing of the paper and the
outer ply 16 is made possibly by treating the seal areas of the
plastic with a corona discharge produced by a voltage source of
10-30 kv at a frequency of 3-5 kHz.
Many kinds of paper provide for an inexpensive, easily handled
closure membrane 14 but depending upon particular needs, other
materials, both woven and non-woven, that are impermeable to
bacteria yet are comparatively highly permeable to sterilizing
vapors may be used. These alternatives would include various
paperlike materials such as glass fiber products and "Tyvac" (a
spun polyolefin of the Du Pont Company) which are impermeable to
bacteria but, in comparison to the plastic bag 12, highly permeable
to sterilizing vapor.
As best seen in FIG. 2, the closure membrane 14 and the plies 16
and 18 are all bonded together along longitudinal joinder lines 40
and 42 symmetrical of the center line 33 and spaced apart somewhat
more than the transverse spacing between the edges 26 and 28 of
inner ply 18. The bonds are preferably and most easily obtained by
heat sealing, using spaced apart heat sealer bars elevated to the
required heat sealing temperautre. The bonding may also be provided
by adhesive or other forms of chemical or mechanical bonding.
As shown in FIG. 1, the longitudinal joinder lines 40 and 42 may be
terminated short of one end of the closure membrane 14 thereby
defining a pull tab 44 to provide a manual gripping edge and
thereby facilitate removal of the closure membrane 14. The closure
membrane 14 may also have transverse extensions 46 and 48 beyond
the longitudinal joinder lines 40 and 42 of sufficient width to
provide a lateral pull tab on each side of membrane 14 in addition
to, or instead of, the end pull tab 44. It is generally sufficient
to provide a pull tab of only so much width that it can be grasped
with the tips of the fingers. Where greater tearing forces are
involved more area may be provided for more secure gripping.
In accordance with one practical example of the invention, the
width of the closure membrane 14 is 25/8 inches in comparison to
the overall width of the package of about 61/4 inches. Thus, the
width of the closure memebrane 14 is little more than 1/3 of the
entire package width and in most instances this is sufficiently
narrow to facilitate a view of the article 10 through either face
of a package fabricated of transparent plies. The transverse
distance between the longitudinal joinder lines 40 and 42 is about
21/8 inches and the edges 26 and 28 of the inner ply 18 each extend
inwardly approximately 5/8 inch from the adjacent longitudinal
joinder line. Each ply of the container is 2 mils thick and made of
transparent polypropylene and the closure membrane 14 is uncoated
paper having a thickness of 4 mils. Obviously, great variations in
the dimensions, configuration and other characteristics of the
package can be made within the purview of the invention.
Referring again to FIG. 1, the transverse end edges 52 and 54 of
the plies 16 and 18 respectively, are joined to each other and to
the closure membrane 14 by trnasverse joinder lines 56 and 58 each
of which is adjacent one of the ends of the package. The joinder
lines 56 and 58 are also preferably and most conveniently produced
by heat seals. Thus, it will be apparent from FIG. 1 that the
longitudinal access opening 32 is completely bounded by a
continuous bond or heat seal which is completely impervious to the
passage of bacteria.
The closure membrane 14 may include appropriate printed matter,
identifying the article 10 contained in the package, the name of
the supplier, and so forth. It may also have marginal indicia
showing the points at which the closure membrane 14 may be most
readily gripped for removal and the preferred direction of
removal.
If the article 10 is to be inserted manually, the packages may be
fabricated individually on a suitable package-making apparatus in
which plastic sheet stock is fed intermittently in successive
steps, heat sealed across one end and cut into separate packages,
the end opposite the heat sealed end being open to receive the
article to be sterilized and stored. Standard packaging machines,
such as the "Simplex" manufactured by FMC Corporation, San Jose,
California, may be used but require certain modifications the
nature of which are unimportant to the disclosure of the present
invention but which allow production of the packages of the present
invention at an extremely high rate with a great deal of
reliability, accuracy, and repeatability.
Generally, the plies 16 and 18 are fed as individual, overlapping
sheets from independent supplies, folded over as explained and
joined to the closure membrane 14 to form a composite tube stock.
The closure membrane 14 is fed concurrently with the plastic sheet
stock and is fed along the longitudinal access opening and into
contact with the folded outer ply 16. The longitudinal joinder
lines 40 and 42 are added by a heat seal mechanism using
longitudinal, parallel spaced heater bars and actuated
intermittently in timed relation with the feeding of the plastic
stock and closure membrane strip. An insulated separator plate is
positioned along the path of the composite tube stock within the
tube to serve as a backup member for the heat seal elements.
Appropriate masking arrangements can be provided in connection with
the longitudinal heat sealing operation to prevent heat seals 40
and 42 from extending all the way to the end of the closure
membrane 14 so as to provide the pull tab 44.
After the composite tube stock is formed, the transverse heat
sealing and cutting operations may take place in conventional
fashion using, for example, either roller elements or heat seal
bars to apply the transverse heat seal and either a mechanical or
thermal cutter to separate the tube stock adjacent the transverse
heat seal.
In the event the package is filled manually, it is fabricated with
one open end, as explained, and the article 10 is inserted through
the open end which is thereafter sealed with a transverse heat
seal. If automatic assembly is used in a combined "form and fill"
operation, the article 10 is inserted by machine as a secondary
operation to the formation of the composite tube as described
above. In either case a fully sealed package is provided on a
substantially continuous basis.
Certain additional details of the package according to the present
invention should particularly be noted. The package is
substantially rectangular when empty but is extremely flexible so
that it conforms appropriately to the inserted article 10. The
inner and outer plies 16 and 18 have sufficient strength to provide
adequate protection equivalent to conventional packaging. The plies
16 and 18, when not cohered, are further free to slide relative to
one another to greatly increase the resistance of the package to
damage by abrading. The tear strength of the closure membrane 14
relative to the strength of the longitudinal joinder lines 40 and
42 is such that the closure membrane 14 is separable from the rest
of the package in one piece so that the production of paper
particles and fibers during the removal process is minimized. In
any event, the overlapping construction of the outer ply 16 impedes
the entry into the interior of the package of any foreign matter
such as dislodged paper particles and fibers.
After loading and complete closure of the package, the entire
interior of the package along with the article 10 are sterilized by
steam, or by processes involving the use of sterilizing gases such
as ethylene oxide. These operations in any event are simple and
inexpensive. For example, containment of the package within an
ethylene oxide atmosphere for a short period such as a few minutes
is sufficient for the gas to completely fill the interior of the
package and allow the gas to contact and sterilize all accessible
surfaces within the accepted sterilization times. Thereafter, the
placement of the package in an enclosed chamber held at or near
vacuum levels for another short interval, for example, a few
minutes, is adequate to purge the package of ethylene oxide. The
package is then ready for storage and use. Autoclaving or steam
sterilization is similar except that the process is carried out
with steam as the sterilant at a substantially higher
temperature.
To use the package the closure membrane 14 is grasped by the pull
tab 44 and pulled back, as shown in FIG. 3. Upon complete removal
of the membrane 14, the article 10 is readily removed from the
package.
Any air that might otherwise become trapped within the space
between the plies can be removed by cohering the plies, that is, by
intimately uniting the faces of the sheet stack mechanically.
Mechanical cohering may be accomplished by rolling under slightly
elevated temperature and pressure or embossing the plies together;
such treatment has the further advantage of facilitating separation
of the overlapping portions of the plies within the confines of the
access opening. Embossing techniques and patterns which will
accomplish the desired results are well known in the art.
Elimination of air between the plies precludes rupture of the bag
during the sterilant-purging vacuum cycle and permits such cycle to
be rapidly applied to decrease the overall residence time of the
bag in the sterilizing apparatus. The cohesion between the sheet
stock forming the plies of the bag can be enhanced by pretreating
the contacting surfaces with a corona discharge pursuant to
practices well known in the art.
The uniformity of the transverse cross-section of the container 12
essentially eliminates burn-through and other problems related to
excessive differential thicknesses. The overlay of the closure
membrane 14 does result in a greater thickness differential (which
adds 3 to 7 mils to the overall or total thickness) but can be
tolerated without any adverse results. Thus, production rates are
greatly increased and the rejection rate is minimized. Neither
precisely controlled heat seal bar temperatures nor differentially
heated bars are required.
A number of alternatives will suggest themselves to those skilled
in the art. For example, the longitudinal joinder lines 40 and 42
may not only be provided by different types of bonds but may have
different strengths so that removal of the closure membrane might
be from one side only. Similarly, a gripping edge need be provided
only on one side of the access opening 32. For many applications
other sealing techniques can be used such as radio frequency (RF)
sealing.
Turning now to FIG. 2A, an alternative overlap arrangement is
illustrated. The package of this embodiment includes outer and
inner plies 64 and 66, respectively. In this embodiment, the inner
ply 66 (as opposed to the outer ply 16 in the embodiment of FIGS. 1
and 2), is provided with longitudinal overlapping portions 68 and
70, the longitudinal edges 72 and 74 of the outer ply 64 disposed a
short distance inwardly of the longitudinal joinder lines 76 and 78
to define the access opening. All of the features and alternatives
discussed in connection with the embodiment of FIGS. 1 and 2
pertain to the package configuration of FIG. 2A, the only
differences being that the longitudinal extremities of the access
opening are defined by the outer ply 64 and the inner ply 66 is
provided with the overlapping portions.
In FIG. 2B, another alternative is shown in which the outer ply 84
has a portion 86 overlapping with a portion 90 of the inner ply 88.
Thus, the longitudinal edges 92 and 94 of the outer ply 84 are in
abutting or closely spaced relationship along a longitudinal line
lying on one side of the package center line and adjacent one of
the longitudinal joinder lines 96 and 98. The longitudinal edges
100 and 102 of the inner ply 88 are in an abutting or closely
spaced relationship along a longitudinal line lying on the other
side of the package center line near the other of the longitudinal
joinder lines 96 and 98. Again, all of the features, advantages and
alternatives that have heretofore been discussed earlier in
connection with other embodiments are equally applicable.
Although the thicknesses of the plastic plies will usually be the
same, one ply may be thickner than the other in order to achieve
particular package characteristics. For example, superior strength
may be imparted to the outer ply by making it somewhat thicker than
the inner ply. FIG. 2C shows an example of such a package. It is
similar in all respects to the package whose transverse section is
shown in FIG. 2B except that the outer ply 110 is of a heavier
gauge or thickness than the inner ply 112 to obtain certain
advantages and benefits as already discussed. It should be noted
that when the thicknesses of the inner and outer plies are
different, in order to obtain transverse sections of uniform
thickness, the overlap is preferably obtained by overlapping
portions of the outer ply only or the inner ply only as shown, for
example, in FIGS. 2 and 2A.
In FIG. 4, an alternative configuration of the package of the
invention is shown which has already been alluded to. In this
embodiment, the overlapping configuration within the access opening
is the same as that shown in FIG. 2 the only distinction being that
the access opening and closure membrane (here referenced by the
numeral 116) have been displaced substantially to one side of the
longitudinal center line 118. Such package is most often and most
conveniently used in the orientation shown in which the closure
membrane 116 is adjacent the upper part of the package.
Although there have been described above a number of alternative
forms and modifications of packages in accordance with the
invention, it will be appreciated that the invention encompasses
all modifications and variations falling within the scope of the
appended claims. Thus, many other variations of the overlap scheme
will become apparent to those with ordinary skill in the art. For
example, in FIG. 2B, the overlapping portion 86 of the outer ply 84
could be positioned below the overlapping portion 90 of the inner
ply 88.
* * * * *