Note: Descriptions are shown in the official language in which they were submitted.
EXPANDABLE PRESSURIZED BARRIER CONTAINER
BACKGROUND OF THE INVENTION
.. . . _
This invention relates to a pressurized can from
which a fluent product is dispensed by actuating a prod-
uct discharge valve, and particularly, a pressurized canhaving a barrier which separates the product from a pres-
surlzed gaseous or liquefied propellant.
Pressurized cans are used for dispensing liquid,
semiviscous and viscous products. A can from which a li-
quid product is dispensed is often called an aerosol can.In some of these cans, in order to prevent cavitation, a
barrier separates the product from the propellant. Three
basic types of barriers in pressurized cans have typic-
ally been used, a piston system, a sprayed on strippable
film bag, or a bag system.
In the plston system, a ~ree piston, which is
shiftable along the interior of the can, is the ~arrier.
See U.S. Patent 4,171,757. The piston system works for
many products, but because the piston does not create an
impenetrable barrier at the can wall, this system should
-- 2
not be used for products which may bypass the piston.
Furthermore, the piston system is also ineffective ~ith
certain limited types of seamed cans, oddly shaped cans,
cans that change in cross-section over the height of the
can, and misshapen cans, since the barrier piston then
has difficulty sealing to the wall of the can as the pis-
ton moves.
In the strippable film system, a plastic compo-
sition is sprayed onto the peripheral side wall and the
bottom wall of the can. As the product is e~pelled from
the can, the film is pushed up by the pressurized propel-
lant beneath it, and the film gradually strips away from
the sides and bottom of the can to push the product out.
~ecause the bag is being stripped away from the bottom
upwardly, the bag cannot be "pinched-off" and a cut off
in the flow of the product is avoided. To e~sure even
stripping of the bag, the can should be relatively rigid.
The strippable film arrangement has a relatively expen-
sive fabricating process.
The bag system may be made in a number of ways.
In one variant, a bag is inserted into the can and it is
either brought out and around the lip of the can or it is
sealed to the chime or top rim of the can. In either
case, special folds or pleats formed in the bag or a col-
lectlng tube in the bag are necessary to prevent the bag
from collapsing and pinching or cutting off the flow of
the product, especially as the bag collapses toward the
top of the can under pressure while the product is being
expelled~ The bag system of this variant tends to be
expensive because the bags have to be made with either
folds or pleats to avold the "pinching-off" problem.
further disadvantage of this bag system is that bags
which are connected at their opening to the lip or chime
_ 3 ~ S~ ~
of the cans tend to both collapse and tear off at ~he
chime or at the seams. Although inserting a collecting
tube into the bag may overcome some of these problems,
the increased cost tend~ to make this approach impracti-
cal.
In a modification of the just described bag sys-
tem, the bag is simply secured at the top or the bottom
of the can, without being a specially designed bag, but
this system is not capable of fully expelling all of the
contents of the can.
In another variant of the bag system, the bag is
fixedly secured part way along the height of the can, be-
tween the ends of the can. In typical examples of this
system, the position of the bag along the height of the
can is predetermined, before can assembly and filling, by
the bag being secured between bottom and top halves of a
two part container, by an attachment fixture in the can,
or by slots or grooves in the can which fix the location
of the bag. Such a bag may be capable of everting for
expelling all of the contents of the can. But, this var-
iant is not universally efficient i'or all pressures or
all materials being expelled, for all types of propel-
lants or all sizes of cans, and assembly of a can with
such a bag system may be difficult or expensive.
Dif~erent propellants, e.g. a gaseous propellant
or a liquid propellant, require that they occupy quite
differen-t percentages of the total volume of a can, as
discussed in more detall below. For any particular si~e
can, where the posltLon of the bag along the can is pre-
determined by the can design, it is necessary ~or a manu-
~acturer to design and inventory difi1erent sets of cans
for differently positioned bags in the cans. ~ can which
is more universally usable would be preferred.
_ 4 _ ~ ~5~6
Conventional cans used in the bag system are
relatively thick and rigid. In some cases, this is nec-
essary to maintain the seal between the bag and the can
wall~
It would be advantageous to provide a pressur-
ized barrier container using a thin, expandable can wall,
which would be substantially less expensive than a con-
ventional thick, rigid can wall. In addition, it would
be advantageous to provide such a container which could
be used with an inexpensive barrier mounted in a simple
manner to the can wall.
SUMMARY OF THE INVENTION
It is an object of the present invention to pro-
vide a pressurized can with a barier system which may be
used with a thin expandable can wall in which an inexpen-
sive barrier is mounted in a simple manner.
Another object of the invention is to provide a
barrier which dispenses the entire product contents of a
pressurized can without trapping product in the can.
It is a ~urther object oi' the invention to pro-
vide a barrier system which may be used with a great var-
iety of cans, including cans which are oddly shaped.
Another object of the invention is to provide an
effective barrier in an expandable can between the prod-
uct to be dispensed and the pressurized dispensing pro-
pellant.
It is still a ~urther object of the invention to
provide a barrier system which can be firmly and immov-
ably attached to the peripheral side wall o~ the can to
avoid sealing problems.
Yet a further object of the invention is to pro-
vide a barrier system using a flexible barrier which can
be easily disposed at any selected location along the
height o~ the can.
~5;5~i6
Another object o~ the invention is to assure
that the flexible barrier positioned in the can will re-
main sealed to the side wall of the can even as the pres-
sure in the can causes its walls to e~pand.
A pressuri7able container according to the in-
vention comprises an expandable can wall and a barrier~
The barrier is mounted to the can wall by means which
ensure that a seal is maintained as the can wall expands
due to pressure.
More specifically, the invention provides a bar-
rier system for an expandable pressurized can from which
a fluent product is dispensed under pressure through a
discharge opening in the can. The can has a wall ~hich
surrounds a can chamber and has the discharge opening at
its upper end. The can side walls are thin enough that
under pressures to which the contents of the can are
pressurized, the side walls will flex and expand out-
wardly slightly. The diameter of the wall across the can
may increase by at leat one one-thousandth (l/lOOO) o~
its unexpanded value as the pressure goes from zero to
100 psi.
A flexible barrier, such as a bag in the shape
of a cup, is mounted in the can to divide the can chamber
into a product chamber above the barrier and a propellant
chamber below the barrier. The barrier is impervious to
the product being dispensed and to the propellant for
dispensing it. The ~lexible barrier is sealed to the
peripheral wall o~ the can by sealing means to guarantee
that neither the propellant nor the product can leak past
the seal, and the seal is maintained according to the
inventlon even when the can pressure causes the can walls
to flex and expand. The barrier is mounted in the can so
that it everts as the product is dispensed from the can.
~2S~ 6
The sealing means may comp~ise a fairly rigid
ring of plastic, or the like, which is disposed inside
the open peripheral edge of the barrier. The ring has a
peripheral exterior shaped and sized for snugly fitting
against the inner surface of the side wall of the can.
The ring is inserted into the barrier, and the ring in-
side the barrier presses against the side wall o-f the
can. The ring is placed in the can at a height which
will allow the barrier to be everted~
As the can walls are flexible and are expected
to flex slightly when the can is pressurized, the ring
must assure the continuing seal between the product and
propellant chambers, respectively above and below the
barrier. Appropriate means comprising at least one of
either the can wall and the inserted ring are stressed
and deformed before the can is pressurized such that upon
pressurization of the can and slight expansion of its
side wall, the seal is still rnaintained.
In one embodiment, the ring includes expansible
zo wall engaging means at its periphery which are sized so
that when the ring is installed in the can before the can
wall has expanded, the expansible means on the ring are
compressed and de~ormed by the contact with the wall o~
the can. For example/ a plurality of resilient annular
ridges or flanges may be defined on the ring periphery.
The flanges normally have a fully extended diameter
greater than the expanded diameter oi' the can wall. Upon
pressurization of the can, with corresponding expansion
of its flexible wall, the expansible means, i.e. the
~langes on the ring, expand or flex outwardly to maintain
contact and seal with the wall. In an alternate embodi-
ment, the periphery o~ the ring includes a receptacle,
such as a groove, for receiving an expansible means, such
as a separate, expansible and compressible O ring. The
O-ring is of a diameter to be compressed when the sealing
~5~
-- 7 ~
ring is inserted in the can. The O-ring is expansible to
maintain a seal with the side wall of the can when the
can expands.
In a second embodimen-t of the sealing means, tbe
ring is rigid and its periphery is rigid. However, the
ring diameter is selected to be slightly greater than the
diameter of the can when the can is unpressurized. As
the ring is installed by pushing it into the can, it de-
forms the side wall outwardly. Wherever the ring is
lodged along the height of the can, the can will be
slightly deformed outwardly at that location. The extent
to which the ring diameter is greater than that of the
can is only slight. Too great a difference in these di-
ameters would permanently deform the can wall to a new
shape, and upon pressurization, the seal between the can
wall and the ring would be broken. However, slight de-
formation of the can wall would not cause a permanent
change in shape of the can wall, '~hen this can is pres-
surized, its wall above and below the ring expands, while
the slightly deformed section of the can wall at the ring
does not correspondingly expand, and the can to ring seal
is thereby maintained.
The sealing means may take other forms, provided
that the seal is maintained as the can wall expands. In
an additional embodiment, a stretchable adhesive is used
which stretches as the can wall expands without cracking
or otherwise breaking the seal. In another additional
embodime~t, the barrier itself is sufficiently stretcha-
ble that the sealin~ means may be a direct mounting of
the barrier to the wall by adhesive or by a melting pro-
cess such as heat sealing.
In one embodiment, the flexible barrier is
formed from a sheet with a surface area which is greater
than the transverse cross-section o~ the can. The sheet
may form a bag in the shape of a cup. The flexible bar-
66
-- 8
rier is e~tendible into the can below the ring when thecan is filled with product, and is extendible above the
ring through the pressure exerted by the propellant in
the propellant chamber as product is being expelled from
the product chamber~ The flexible barrier is everted
above the ring and pushes the product out until substan-
tially all of the product has been e~pelled.
The can is fitted with an upper cover which also
supports a discharge valve through which the product is
eventually expelled. The can is filled with product up
to the underside of the cover. The upper cover may be in
the shape of a dome, and the product discharge valve can
be fitted at the apex of -the dome. A gaseous or liqui-
fied propellant is introduced into the bottom of the can
beneath the barrier to define the propellant chamber and
this serves to pressurize the product within the can
above the barrier.
~ s the product is expelled through the discharge
opening, the barrier under pressure from below begins to
evert into the upper region of the can to continually
keep the product pressurized. The size or surface area
of the barrier and the point along the height oE the can
at which it is secured to the can are chosen such that
when the barrier is ~ul]y everted, its top sur~ace is in
contact with the peripheral side wall and with the upper
cover of the can to ensure that substantially all o~ the
product has been expelled ~rom the can.
Other ~eatures and advantages o~ the invention
will be appar0nt trom the ~ollowing description of the
preierred embodiments illustrated in the accompanying
drawings.
BRIEF DESCRIPTION OF THE DR~WINGS
. .
Fig. 1 shows a cup shaped barrier assembled with
a sealing ring prior to insertion into the can body.
~552~
g
Fig. 2 shows the can body prior to the inser$ion
of the barrier.
Fig. 3 is a cross-sectional, elevational view
showing a pressurized fluent material containing and dis~
pensing can having in it a barrier according to a pre-
ferred embodiment of the invention.
Fig. 4 shows the pressurized can after it has
been filled with product and sealed ~ith a top cover and
after a small quantity of product has been expelled from
the can.
Fig. 5 shows the can and barrier after all the
product has been expelled.
Fig. 6 shows a first sealing ring embodiment ~or
the barrier for providing the seal between the product
and propellant chambers of the pressurized can.
Fig. 7 shows a second embodiment of such a ring.
Fig. 8 shows a third embodiment of such a ring
and can construction for such purpose.
Fig. 9 shows an alternate embodiment of pressur-
~0 ized can in which the barrier is mounted directly to thecan wall,
DETAILED DRSCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig~ 2, the pressurizable can ac-
cording to the invention includes an outer can 10 com-
prising a cylindrical body, defined by a cylindrical per-
ipheral side wall 12, an open to~ 1~, and a closed bottom
16 shaped to allow the pr~ssurized can to stably rest on
a ~lat surface. For strength, the can bottom 16 includes
a peripheral rounded ridge 17 on whose crest the can
sits, and a rounded depression 18. Other bottom shapes
can be used to increase the strength of the can, and a
number of such shapes are generally ~nown in the art.
The top o~ the depression has a pluggable hole 19 through
it into the can. A gaseous or liquified propellant is
-- 10 --
conventionally supplied (Erom a source not shown) through
the hole 19 after the top opening 1~ has been closed so
that the can may be pressurized. Thereafter, a plug 21
is installed in the hole 19 to Glose it.
S The material of the can is typically metal.
However, other materials like strengthened paper or plas
tic may be used, so long as it is strong enough to con-
tain the pressure in a filled pressurized can. For
safety, it is desirable often that the can be of metal.
For economic reasons, that is to reduce the
amount of materials re~uired in can fabrication, it is
desirable to have thin walled cans. The can wall accord-
ing to the invention is sufficientIy thin that it expands
when the can chamber is pressurized. The dimension of
the can w~ll across the can chamber, such as the diameter
of a cylindrical can wall, will increase in length. For
example, at the lower pressures described below, the can
wall may be made by a drawn and ironed process from sheet
steel or even sheet aluminum giving a wall thickness of
.0045-.008 inch. It is even possible to use a steel can
with a wall thickness of less than .0045 inch. In such a
can which is sealed and under pressure, and where the
temperature to which the can, its contents and the pro-
pellant therein are exposed is in the range of 30-130F,
the pressurization of the can could cause an increase in
its diameter of between .002-.007 inch for temperatures
of 30 130F, respectively. For a thin-walled can ac-
cordlng to the invention, the diameter will increase by
an increment whlch will be approximately one one-thous-
andth (1/lO00) or more of its unexpanded value as it ispressuriz0d to a pressure of 100 psl. If the diameter is
2.50 inches, -the increment will be approximately .0025
inch or more. This increment is approximate in that it
is within the scope of the invention for the increment to
~5 5i~ D
be a few ten-thousandths of an inch less than this value,
depending on the particular alloy of the can.
It has been found that even a gap of .OO1 inch
between the side wall of the can and a ring suppor-ting a
barrier in the can will permit leakage of propellant and/
or product past the ring and barrier, which is undesira-
ble. Therefore, the container according to the invention
includes means for mounting the edge of the flexible bar-
rier to the can wall and for sealing the mounting for
preventing the product and propellant from leaking past
the edge of the barrier as the can wall expands and re-
turns to its unexpanded condition~ This means may take
any of several forms, as described below.
Because the propellant is not mixed ~ith nor ex-
pelled with product from the can 10, the initial pressureand quantity of the propellant in the can need not be
very high, and with some very fluent products and rela-
tively larger discharge valve orificest -the can pressure
can be quite low, e.g. 10-B0 psig for low viscosity prod-
ucts, as compared with the conventional aerosol barriercan pressure of about 90-lOO psiK. This lower pressure
helps to avoid stress on the seal and can-~a~ wall, per-
mitting use of thinner walls and simpler bottoms, but
higher presssure, up to 120 psig or more, could also be
used with cans whose walls and bottoms are designed to
withstand this stress.
There are a variety of dif ferent propellants
which may be placed in the pressure chamber, including
various compressed gases or liqui:Eied gases, Where the
propellant is a compressed gas, typically in an aerosol
container, the compressed gas pressure chamber occupies
in the range oE 1/3-1/~ of the total volume of the entire
can. On the other hand, where the propellant is in the
Earm of a liquified gas, the pressure chamber occupies in
the ran~e of 1/10-1/50 of the total volume of the can.
- 12
It is economically desirable to produce a st~ndard can
design which can include a barrier that is adapted for
either type of propellant, that is where the propellant
chamber can be relatively smaller in volume or where it
S must be larger. The invention permits this.
Also, there is a wide variety of fluent products
which may be contained in and expelled from the can 10,
including quite fluent li~uids of a viscosity of 10,000
cps or less and higher viscosity products like processed
10foods, e.g. cheese at a viscosity upwards of 300,000 cps
or even higher, depending on the rheological properties
of the product. Very low viscosity products, such as
water and alcohol (1 cps or less) may also be contained
and expelled.
15Referring to Figs. 1, 3-5, there is a barrier 20
in the can, which is shown in the shape of a cup. The
barrier is a sheet of greater cross-section than the can,
and the barrier sheet may be cut and folded so that the
cup shape may be defined. Further, the sheet may have a
pocket or generally tubular shape or it may be flat, al-
though i-ts surface area and shape are preferably such
that the sheet will extend to the closed cover of the
can, as described below. The cup shaped barrier has a
side wall 22 and a closed bottom. The barrier may simply
be a flat sheet which is deformed in use. It may be a
sheet with cut regions which enable the sheet to be
shaped into a cup, and the cut regions of the sheet are
attached to the can at their marginsl The cup is of a
flexible material so that the cup may be filled and later
everted as described below. The cup may also be made by
vacuum forming or blow molding.
The material of the barrier 20 need merely be
sufficiently ductile and flexible to evert as described
below and be impervious to the product and to the propel-
lant which contacts the barrier at its opposite sides.
- 13 -
The material is preferably not a highly stretchable
material like rubber, although some stretching may be
desired. For example, an ine~pensive plas-tic sheet or
tube material of substantially uniform thickness and
flexibility may be ~olded and heated to form a cup-shaped
~ bag. Suitable ~lastics could inclu~e polyethylene, poly-
g~ propylene, Myl ~, Sara~,~an ~so ~o~th, The barrier maybe made of a paper, e.~. a waxed paper. It may be of any
appropriate fabric. It could even be a metallic barrier,
such as an alumi,num film, or metallized plastic, such as
aluminum on Myla~o~r ~aran~rC~e~' J
The means for mounting and sealing the barrier
20 to side wall 12 of can 10 may take several ~orms. In
general, the mounting and sealing means must maintain the
seal despite the expansion of the can. If can wall 12 is
smooth and continuous, a seal may be more easily main-
tained, in most cases. The specific forms of the mount~
ing and sealing means described below include ring seals
as well as adhesives and melt sealing.
F'igs. 1 and 3-5 show a general ring seal embodi-
ment in which a barrier fastening ring 24 is inserted
into the barrier 20 and is positioned in the region near
the upper edge 26 of the cup shape. The barrier 20 with
its ring 24 are inserted into the can 10 and are posi-
tioned a distance clown from the open top 14 of the can.
The dimensions of the ring 24 and the barrier are selec-
ted such that the ring 24 can snugly fit against the per-
ipheral side wall 12 of the can 10, thereby securing the
barrier cup 20 firmly in the can. In this manner, the
can 10 is divided by the cup into the upper product cham-
ber 30 and the bot-tom propellant chamber 32,
The size and shape oi' the barrier are coordina-
ted with the height of the can 10 and with the position
oi the ring 24 along the height of the can intermediate
the upper and lower ends so that when the barrier is sub-
stantially fully extended, it will e~tend toward the bottom of the can and be substantially fully in contact with
the peripheral side of the can when the can is loaded
with the product and it will extend toward the top oi the
can and be substantially fully in contact with the side
of the can and with the cover over the can when all the
product has been expelled. Although barrier 20 could be
slightly larger than the upper region, it is prei'erable
that the barrier substantially fill the upper region of
the can when fully everted, barely leaving some unfilled
space, so that it cannot be pinched off by islanding
caused by the propellant and so that nearly all of the
product may be expelled. This makes it unnecessary to
use a tube or other device to prevent pinch-off. Any
suitable type of valve may be used in the discharge open-
ing.
For use with liquified gas propellants, the ini-
tial volume of the upper product chamber 30 may be much
larger than that of the bottom propellant chamber 32, on
~0 the order of 15 or 20 to one, thereby utilizing the
majority of the space within the can body for the prod-
uct. For use with compressed gas propellants, the ini~
tial volume of the product chamber 30 to the initial vol-
ume of the propellant chamber 32 would typically be on
the order of 2 or 3 to 1. To accommodate these different
chambers of different volume in a can of a standard size,
and to enable the two chambers 30, 32 to have a correct
volume relationship, lt is desirable to be able to posi-
tion the ring 24 and the barrier at appropriate selected
positions along the height o~ the can wall.
As the invention is intended to assure complete
expulsion of product in the chamber 30, the barrier size
and shape are selected so that the barrier will press
against the inside of the can cover on eversion to expel
product, and the barrier will not be folded or wrinkled
there but will instead be i'ully extended.
- 15 -
The two chambers 30, 32 are sealed off at the
peripheral side wall of the can by the outward ~orce ex-
ertsd by the ring 2~ on the wall 12. As the pressures in
the product and propellant chambers are identical when
the discharge Yalve 38 is closed and are nearly identical
when that valve is open, the holding ring is not likely
to move along the wall of the can.
After the product has been loaded in the product
chamber 30 of the can 10 and the propellant has been
loaded in the propellant chamber 32 of the can 10, the
can is pressurized. The internal pressure in the can
causes the side wall of the can to bulge slightly in di-
ameter. For example, if the can 10 is of aluminurD with a
2.5 inch diameter and with a wall that is 0.005 inch
thick, when the can is pressurized to 60 psi at normal
room temperature of 70C, its diameter will increase ap-
proximately 0.004 inch. If this expansion is not compen-
sated for, a radial clearance will be created between the
interior of the can wall and the exterior of the ring 24.
The radial clearance will provide a leakage path between
the product and propellant chambers allowing gas and/or
product to bypass the barrier cup 20, resultlng in a
pressure reduction in the can, leakage of propellant out
of the valve of the can and inability to properly expel
all of the product from the product chamber.
A number of ring seal embodiments described
herein compensate for the bulging enlargement of the di-
ameter of the can.
The first alternative is to provide the ring 24
with a preloaded, radially expansible, elastic seal
against the can wall, so that even when the can expands
as it is pressurized, the ring expands with the can and
maintains the seal. As shown in Fig. 6, the ring 24 is
provided on its periphery 42 with a vertically spaced
array of annularly uninterrupted, resilient flanges 44,
~25~
each with a diameter greater than the anticipated inside
diameter of the can when it has been e~panded under pres-
sure. The flanges 44 are thin and flexible enough that
as the ring 2~ is installed in the can, the flanges 44
are deflected radially inwardly, that is, they are some-
what flattened against the periphery 42 of the ring. As
the can wall expands upon pressuriza~ion, the resilient,
somewhat flattened flanges resiliently deflect slightly
outwardly to maintain their biased contact against the
internal wall of the can for pressing the barrier against
the can wall and maintaining the seal.
In the second embodiment of Fig. 7, in contrast,
the ring 46 is of a different design. It is a solid,
annular body with an exterior peripheral channel 48 which
opens radially outwardly. The channel receives and holds
in it an elastic, resilient, compressible sealing element
50, illus-trated as an O-ring. The diameter of the seal-
ing element ring 5~ is slightly greater than the internal
diameter of the can, even when the can has stretched un-
der pressure. When the ring 46 with the captive O-ring
50 in the channel 48 is installed in the can, the O-ring
50 is compressed through its engagement against the can
wall. As the can wa]l expands under pressure, the resil--
ient ring 50 tends to restore itself to its undeflected
condition and is biased outwardly against the barrier and
the can wall for maintaining the seal there.
The third embodiment shown in Fig. ~ uses a dif-
ferent approach to accomplish the same result. The above
described thin, metal can wall is slightly deformable
3n under pressure. If the~ can wall is only slightly de-
formed, at less than the degree of deformation which will
permanently deflect the can wall from its normal profile,
the normal resilience of the metal can material will tend
to restore the wall to its original undeflected shapeO
(This is what occurs as th~ can is pressurized to a nor-
~25~
- 17 -
mal extent and is gradually depressurized through use.)
As shown in Fi~. 8, the annular ring 5~ inside the can 10
has an outer periphery 56 with a diameter that is only
slightly greater than the diameter of the can wall even
when that wall is pressurized. As a result, when the
ring 54 is installed in the can, it does not unduly
stretch and deform the can wall. The can wall therefore
does not assume a new, deformed shape. Instead, the can
wall yields slightly as the ring is moved along the can
wall until it is finally lodged in a selected position.
The resilient, but not permanently de~ormed can wall
maintains a tight seal with the ring and prevents leakage
past the ring between the can chambers.
The ring 54 is si~ed so that it stretches the
can wall larger than the diameter to which the can would
expand at maximum loaded pressure and maximum anticipated
temperature, but less than the yield point of the can
material. For example, if an aluminum can with a 2.50
inch inner diameter and with 0.005 inch thick wall is
pressurized to 60 psi at 70F, it expands approximately
0.004 inches in diameter, to an inner diameter of 2.50~
inches. This will create a hoop stress of approximately
15,000 psi. The ring 54 has its periphery sized to ex-
pand the can wall by at least about two to four one-
thousand-ths (2/1000-~/1000) from lts unexpanded diameter,
and may expand it to 2.509 inch diameter, for example.
This expansion, referred to as interference, results in a
seal which is maintined as the can expands under pres-
sure. This wiL1 also create a hoop stress in the area of
the ring of approximately 33,750 psi, which is still well
below the yield point of the aluminum can material and of
the ring, Even if the internal pressure in the can is
raised to 100 psi at 70F, this will only expand the can
tQ approxirnately 2,507 inch, with a hoop stress of 25,000
psi. Under all expected circumstances to which the can
- 18 - ~ ~5~2~6~
may be exposed, the can will, therefore, not expand so
that its inner diameter is greater than the outer diame~
ter of the periphery 56 of the ring. Good sealing con-
tact will thereby be maintained and bypass of the ring
between the two chambers is avoided.
The above techniques of maintaining a seal rely
upon the elasticity of at least one of the can and ring
~or maintaining the seal, with the first mentioned tech-
niques of Figs. 6 and 7 using the resilience of the ring
to maintain the seal and the latter technique of Fig. 8
using the resilience of the can to maintain the seal.
A completely assembled pressurized can with a
ring seal according to the invention is shown in Fig. 3.
The upper cover 34 closes off the top opening 1~ of the
can. The cover 34 is shown dome shaped and has an apex
36 with a hole 37 through it in which a hole sealing,
product discharge valve 38 is affixed. The cover is
crimped to the chime 39 at the top of the can.
The can is filled with a fluent product through
the hole 37 before the discharge valve 38 is emplaced.
This moves the barrier 20 down to the bottom of the can
and defines and completely fills the barrier 20 and the
product chamber 30. The can is i'illed with product to
the underside of the cover 34, i.e. until it is com-
pletely filled. Then the dlscharge valve 38 is emplaced,which closes the hole 37. The discharge valve may be a
known tilt operated valve (or any other valve suitable
for the purpose), and it seals the product chamber when
it is closed. Next, the propellant chamber 32 is filled
with a ~aseous, or liquifled propellant through the hole
19. When the desired pressure level or quantity is at-
tained, the gaseous pressure supply or liquified propel-
lant is removed and the hole 19 is plugged by a plug 21.
The can is now ready for operation.
~5~
-- 19 ~
The can in Fig. 4 is shown at a stags after a
portion of the product has been expelled from the can
through the valve 38. The barrier 20 is shown partially
everted due to the propellant as the barrier assumes a
shape defined by the remaining product.
Because the barrier is mounted to the peripheral
side ~all 12 at a height which is near the middle of the
can 10 with its cover on, the barrier moves from extend-
ing downward into the can, is deflected up past the ring
24 and finally everts and extends upward into the cover
34, as substantially all the product is finally expelled,
as shown in Fig. 5. This eversion prevents the barrier
from pinching-off or islanding which would prevent expul-
sion of the product due to some product being captured in
a pinched-off region of the barrier.
The barrier cup is so shaped and the ring 2~ is
so positioned that when the barrier 20 is fully everted
as shown in Fig. 5, it substantially fills the space
bounded by the cover 34 and the side wall 12 of the can
located above the fastening ring 24. When the product
chamber 30 is filled before product is expelled, the bar-
rier fills a portion of the space bounded by the con-
tainer bottom 16 and the side wall of the can. This as-
sures that almost the entire volume which is bounded by
the walls and bottom of the can 10, besides that volume
needed for propellant, may be filled with the product and
that all of the product is usefully expelled from the can
when the barrler has been fully everted.
The sealing effectiveness can be increased
through the lntroduction of sealing compounds between the
fastening rin~ and the barrier and/or between the barrier
and the can wall.
As the pressure differential across the barrier
is usually ~uite small, it may alternatively be suffi-
~
cient to secure the barrier cup 20 directly to the can
- 20 -
wall without a ring 24. Other means ~or mounting and
sealing the barrier may be used for directly mounting the
barrier to the can wall at a seal 84 as shown ~n Fig. g.
Seal 64 may be obtained with a ring of adhesive applied
directly between the entire upper edge of the barrier and
the can wall or by a melt process in which the upper edge
of the barrier is melted and sealed to the can wall.
This arrangement still must compensate for the anticipa-
ted e~pansion of the can wall under pressure and its re-
turn to the unexpanded condition.
If an adhesive is used to form seal 64, the ad-
hesive substance and the upper edge ~2 of the barrer must
-together be sufficiently expansible and contractable to
compensate for change in can diameter. Any suitable ad-
hesive which provides a sufficient bonding force to main-
tain the seal may be used, including rubber cement, glue
and hot melt glue. The barrier may be a stretchable
material such as polypropylene.
If a melt process is used to form seal 6~, upper
edge 62 of the barrier must alone be sufficiently expans-
ible and contractable to compensate for can diameter
change. The melt process may employ thermal, sonic, or
radio frequency heating. The barrier may be polyethylene
or polypropylene or any other suitable material. Again,
it is nece9sary to obtain a suf~icient bonding force to
maintain the seal. The barrier and the adhesives must be
capable of stretching as needed without tearing and with-
out tearing away from the periphery of the can.
The invention simplifies production oi the can
and its product-propellant barrier and eliminates concern
about close manu~acturin~ tolerances i~or the barrier and
i'or its attachment to the can. For example, in previous
barrier pack cans, which employ a piston barrier system,
or in the bag barrier system with folded or pleated bag
~25~
- 21
side walls to enable the bag to collapse without pinch-
off, the consistent predictable shape of the can lO was
critical to the operation of the barrier system. With a
piston system, an indentation in the container above the
piston would prevent the piston from traveling ~]p the
peripheral side ~all o~ the can. With the present bar-
rier system, however, the container can be of almost any
size or shape. It is not even necessary that the periph-
eral side walls of the container be generally parallel to
each other as with other known systems. Consequently,
cans could be used with either esthetically pleasing
shapes or other shapes which are designed in accordance
with human iactor engineering principles.
Although the present invention has been de-
scribed in connection with preferred embodiments thereof,
many variations and modifications will now become appar-
ent to those skilled in the art, It is preferred, there-
iore, that the present invention be limited not by the
speciiic disclosure herein, but only by the appended
claims.
