NO970179L - Flexible locking element useful in aerosol dispensers - Google Patents

Description

The invention relates to pressurized dispenser packaging or packaging, such as aerosol packaging, where the product to be dispensed and the pressure-generating media, i.e. the propellant, are kept isolated through separation on opposite sides of a barrier or barrier. An aerosol pack of this type is commonly referred to as a "barrier pack" aerosol packaging.

Aerosol barrier packs of the known type have been of at least three main types. In the piston-type barrier seal, the barrier is a piston-like component which is mounted in the container in sliding relation to the inner surface of the container. The product to be dispensed is located on the valve side of the piston and the propellant, which creates the pressure inside the container, is on the opposite side of the piston. In the Aerosol Handbook, Second Edition, 1982, there is described a piston type aerosol dispenser marketed by the American Can Company under the trademark "Mira-Flo". In the Mira-Flo dispenser, the piston skirt is designed to seal against the sides of the container to prevent the propellant gas from passing into the product chamber on the other side of the piston. Activating the aerosol discharge valve causes a reduction in the pressure in the product chamber, which thus means that the pressure in the drive chamber presses the piston against the discharge valve and causes discharge of the product through the discharge valve. Examples of a barrier seal of the piston type are described in US patent nos. 3,022,923, 3,756,476 and 3,929,132.

In another type of aerosol barrier package, a flexible, collapsible bag is attached inside the container opening either to the aerosol release valve or to the bead at the container opening. The Continental Can Company introduced in the late sixties an aerosol barrier dispenser known as the "Sepro-Can". The Sepro-Can includes an inner plastic product bag with an opening that is attached to the valve opening in the top of the container. The side walls of the bag run along the side walls of the container

IN

and is pleated like an accordion so that the bag can fold inwards and upwards under the influence of pressure in the rest of the container as the bag is emptied. Patents showing a barrier seal of the second type are US Patent Nos. 3,788,521, 3,896,970 and 4,067,499. Modifications to barrier seals of the second type include attaching the bag to the side wall of the container or to the joint formed between the side wall of the container and the top of the container.

in

A third type of known barrier seal is an unfolding cup-shaped barrier where the barrier has an outer wall which terminates in a sealing flange, the outer wall being placed continuously with the inner wall of the container. The inner wall of the barrier is first folded inside the outer wall, the inner wall ends in a completely closed part. The barrier is held in a valve-equipped aerlosol container and sealed in the joint formed between the side wall and the lower end cap of the container. The product is supplied through the valve opening in the container and propellant through a port in the lower end cap of the container. Activating the valve reduces the pressure in the product space and causes the inner wall of the barrier to unfold from inside the barrier's outer wall and causes the end-closing part of the inner wall of the barrier to advance and thus push the product towards the discharge valve.

in

A patent showing the third type of known barrier gasket is US Patent No. 3,109,463.

in

A problem with the piston type barrier packing of the first type is the imperfect seal between the side skirt of the piston and the side wall of the container which causes propellant to

in

seeps into the product with subsequent release of propellant during product release as well as contamination of the product with propellant. It is also not unusual for aerosol containers to become dented and thereby lose their true circumferential shape, with the result that the piston is unable to axially move within the container past the deviated shape.

in

in

in

A problem with barrier packages of the second type where the barrier is attached to the valve or the valve opening in the container is that the barrier collapses in a way that causes pocketing of the product inside the collapsible barrier with subsequent undesirable reduction of the evacuation of the product from the container.

In the third type of prior barrier packaging described herein, the unfolding cup-shaped barrier does not advance progressively and smoothly against the inner wall of the container, but tends to pocket and trap the product against the wall or within the pockets formed in the barrier itself as it unfolds. Attempts to solve these problems have included adding an additional rigid stamp against the end-closing portion of the inner wall, or adhering the outer wall of the barrier in a peelable manner to the inner wall of the container. In general, barriers of the third type can be difficult to form, as well as introduce into and form a seal with the container.

There is therefore a need for a flexible product/propellant barrier for an aerosol container which is easy to manufacture and transport, which is easy to introduce into and sealed to the container, which prevents leakage of fluids from one compartment to the other compartment, and which do not form a pocket and therefore exclude the evacuation of significant quantities of the product to be released.

The present invention relates to an improvement of the third type of barrier seal. In its broadest sense, the present invention relates to a uniform flexible and expandable barrier for use in a multi-zone, valve-equipped pressure vessel, where the barrier has a created spatial shape with sufficient rigidity to maintain its shape before being put into use in a multi-zone, valve-equipped pressure vessel. The barrier comprises a flexible and expandable wall portion with an outer wall segment and an inner wall segment connected by an angled bend, where the free end of the outer wall segment forms a sealing bridge and the end of the inner wall segment distal to the dmbend extends into a central piston area that closes the barrier . In a preferred form, the outer wall segment is broadly conically truncated in shape and terminates at its free end in a sealing member, and the inner wall segment is placed in adjacent relation to the

in

inner surface of the outer wall and in steep conical truncated form opposite to the conically truncated form of the outer wall segment so as to form a small acute angle between the

in

outer wall segment and inner wall segment; the conclusion of

in

the inner wall segment distal to the bend is closed by a central piston area to thus complete the unitary barrier element. Furthermore, the inner wall segment is sufficiently flexible that the inner wall segment and the central piston region can move in an axially downward direction under the influence of the propellant pressure when the barrier is sealed at the top of the container to assume a more or less phallic shape. Furthermore, the jed outer and inner wall segment has sufficient flexibility<p>g expandability to expand outwards under the influence of the propellant pressure to essentially conform to the shape<i>of the inner surface of

in

the container. When the outer wall segment is sufficiently thicker and stiffer than the inner wall segment, the outer wall segment will tend to continue to have substantially the same shape as the inner surface container, and the flexible inner wall segment will invert! within the outer wall segment under the influence of the propellant pressure to generally return the barrier to its approximate shape as originally placed in the container. Then |vi 1 the inner wall segment and the central piston area extend radially outward and upwards to largely evacuate the product in the container. When the outer wall segment is less thick and less rigid, the inner wall segment and the central piston will move axially upwards under the influence of the propellant pressure, followed by both the outer and inner wall segments creeping closely together and

in

moving upwards. In this last case, at least in

in the case of low viscosity products, the product will mostly be evacuated from the container.

By virtue of having sufficient rigidity to maintain its shape before insertion into the container, as well as the presence of the tapered outer wall segment, the barrier according to the invention is very easy to insert into the top of the container. Due to the tapered outer and inner wall segments, the barrier can be placed in similar barriers for appropriate and cost-saving transport. Furthermore, this makes it possible for them to be placed in each other, quick and easy machine feeding of stacked barriers sequentially into the containers.

In a preferred form of the invention, the outer wall segment is thicker and stiffer than the inner wall segment; the inner wall segment is also of somewhat less length than the outer wall segment; and the sealing means is a radially extending flange which acts as a gasket between the top of the side wall of the container and its upper closure. The central piston area may also be thicker than the inner wall segment.

A particularly advantageous material for the barriers is polyethylene terephthalate (PET). Where penetration over the barrier is a concern, the barrier according to the present invention can utilize a uniform multi-layer design. Such multi-layer designs, their construction materials and their manufacture are well known to those skilled in the art. Generally, in a three-layer system, the inner layer is a material that prevents transport of the propellant and product through it and the outer layers are inert to the propellant and product. FIG. 1 shows a sectional view through an embodiment of the barrier according to the invention. FIG. 2 shows a longitudinal section through the barrier according to FIG. 1 placed in an empty aerosol container with the upper opening of the container shown schematically and the aerosol valve not shown. FIG. 3 shows a schematic diagram of the barrier according to the invention inside an aerosol container showing the barrier in a position after the product has been filled in the container, but before

in

the propellant is introduced into the container.

FIG. 4 shows a schematic view of the barrier according to the present invention inside an aerosol container after the product has been partially evacuated from the container. FIG. 5 shows a schematic view of the barrier according to the invention in an aerosol container showing that the product has been further evacuated and the barrier has inverted its shape

in

as originally present in the aerosol container, which also shows with a dashed line a complete evacuation of the product.

FIG. 6 shows a partial cross-sectional view of a multilayer barrier according to the invention. FIG. 7 shows barriers according to the invention in a superimposed relationship. FIG. 8 shows a schematic diagram of several steps used in the production of the barrier seal according to the invention from a plastic foil.

IN

FIG. 9 schematically shows a thermoforming equipment used for forming the barrier package according to the invention.

Reference is now made to the drawings regarding FIG. 1 shows a unitary barrier generally denoted by 10, as it is initially designed, where the barrier has a wall 11 comprising a flexible and expandable outer wall segment 12 and a flexible and expandable inner wall segment 14 connected by a fold or bend 15,<1> where the outer wall segment 12 terminates in a sealing or sealing flange 16. At the termination 18 of the inner wall segment 14, a central piston area 20 extends inwards to close the barrier. It should be noted that the outer wall segment 12 has a steep conical truncated shape extending from the sealing flange 16 to the bend 15, and that the inner wall segment 14 has a steep conical truncated shape opposite to the outer wall segment 12 extending from the bend 15 to the central piston area 20.

The outer wall segment 12, including the sealing flange 16, is sufficiently thick and rigid to give a formed space shape to the barrier and cause the barrier to be free-standing and ready for insertion into the container.

It has been found that barriers made of PET with the following dimensions have acted satisfactorily as a barrier in a pressure vessel:

Thickness of sealing flange - 0.178 mm

Thickness of outer wall segment - 0.178 mm

near the flange tapering to 0.102 mm at the bend.

Thickness of inner wall segment - 0.102 mm

near the bend tapering to 0.051 mm near the central piston area.

Central piston area - 0.051 mm at the transition between the inner wall segment and the central piston area and increasing to 0.102 mm immediately within the aforementioned transition and becoming thicker to 0.178 mm at the central area of the piston.

The length of the outer wall segment - 79.375 mm

The length of the inner wall segment - 65.881 mm The container used with the PET barrier described above was a 202 x 509 straight sided box which is 53.975 mm in diameter and has a length of 141.288 mm.

The barrier had a 1° taper to each of the outer and inner wall segments, 12 and 14 respectively, to form a

in

fold or bend 15 which provides an enclosed angle of 2° between the outer and inner wall segments 12 and 14. It is assumed that a 3° taper to each of the inner and outer wall segments would also function satisfactorily. The central piston area for the barrier described above had a design as shown in FIG. 1, d<i>is the end 18 of the circumference of

in

the piston had a depth of 4.775 mm and a radius of 1.600 mm. The sealing flange 16 for the barrier described therein had a bending radius into the outer wall segment 12 of 1.981 mm.

FIG. 2 shows the barrier 10 inserted in a valve-equipped pressure vessel generally designated as 22, with inner wall surface 23 and permanently connected to the vessel through the sealing flange 16 with a suitable crimping of the flange 16 between the transition formed by the upper! end 25 of the side wall of the container 22 and the circumference of the upper lid 27 of the container 22. Without intending to limit the type of pressurized container (aerosol) with which the barrier seal according to this invention can be usefully used, it has been found particularly useful when used with an aerosol container commonly referred to as a "necked-in"

in

container. A sealable port 28 is provided in the lower closure 26 for the introduction of propellant. A manually actuated valve (not shown) is located in a manner well known to those skilled in the art in the opening 29 of the pressure vessel 22.

in

In FIG. 2, the barrier 10 divides the inside of the container 22 into a number of zone-wise pressure containers; the upper zone 33 for receiving the product to be delivered and the lower zone 35 for receiving the propellant. Generally, the container manufacturer will introduce the barrier 10 into the container 22, and seal the barrier to the container as described above. A product filler will then fill the product and propellant in the respective chambers 33 and 35.

After sealing the flange 16 between the upper part of the container 22 and the upper side wall of the container 22, the product is introduced into the product zone 33 to cause the barrier 10 to fully expand downwards in the container 22 to have substantially the same shape as the inner surface 23 of the container 22, as shown in fig. 3. During the filling of the product in the container, it may be necessary to provide a device to evacuate air in the propellant and/or product zone. After introduction of propellant into the propellant zone 35, the container is ready to function to dispense product through activation of the aerosol valve located in the container opening 29. Fig. 2 shows a design for incorporating the barrier 10 into the container 22. Fig. 2 shows the barrier package 10 with a closing f flange 16 extending from the outer wall segment 12. The flange 16 fits nicely between the flanges 25 and 27. The seam is formed by rolling the flanges 25, 27 and 16 against the side wall 12 to form a rolled seam using techniques known to those skilled in the art. The thickness and length of the sealing flange 16 is dictated by the requirements for rolled seams, which may vary with the type of container and rolling equipment. The sealing flange 16 may be thicker than the continuous outer wall segment 12. The sealing flange may function as a gasket in sealing the barrier to the bottom of the container. If necessary, an adhesive can be applied to the components to be folded. Fig. 3 shows the barrier in an initial position a short period of time after the container has been filled with product. By continuous or intermittent activation of the valve located in the upper opening of the pressure container, the product will be evacuated from the container by lowering the pressure in the product zone 33 causing the greater pressure in the propellant zone 35 to begin to invert the inner wall 14 of the barrier 10 inside it outer wall 12 and thus push the product through the discharge valve from the container. When product is evacuated from the container 22, the inner wall segment 14 and the central piston area 20 move axially towards the aerosol outlet when the barrier inverts, as shown in fig. 4.

j

If the outer wall cement 12 has a sufficient thickness throughout from the end flange 16 to the board 15, then the outer wall segment will continue to largely adapt to the shape of the inner surface 23 of the container wall throughout the product evacuation shown schematically in fig. 4 and 5. The barrier then returns to approximately its initial shape as shown in fig. 5, followed by radial and axial stretching of the inner wall segment 14 and central piston region 20 to the dotted line configuration shown in FIG. 5 to achieve substantially complete product evacuation from the container. In order to achieve this effect, the thickness of the outer wall segment 12 will probably need to be substantially greater than the thickness of 0.178 mm referred to above; without wishing to be limited in any way, the thickness may be on the order of 0.51 to 0.635 mm from the flange 16 to the fold 15, or sufficient to achieve full inversion of the inner wall segment within the outer wall segment shown in FIG. 5. With this thicker outer wall segment, more viscous products can be completely evacuated from the container without significant pocket formation. The inner wall segmenti will still remain thin and flexible.

in

in

If the outer wall segment 12 has a thickness of the order of 0.178 mm, the transition from fig. 4 to almost complete product evacuation cause both the inner and outer wall segments 12 and 14 to shrink inwards and close together and move upwards. In this case, using water as a simulated product, largely complete product evacuation was achieved from a test setup without significant pocketing. However, where more viscous products are used, it is expected that the thicker outer wall segment 12<i>will have to be used to achieve complete product evacuation without particular pocket formation. It has been observed that the conically truncated design of the inner wall segment 14 causes the inner wall segment 14 to invert progressively in an axial direction within the outer wall segment 12, where the outer wall segment 12 is sufficiently thick, to effect progressive advancement of the product to the discharge valve and a minimization of the entrapment of the product in pockets.

The tapering of the outer wall segment makes it possible to narrow the barrier according to the present invention into the pressure vessel. The presence of the taper for both the outer and inner wall segments, and at small angles, also allows maximum nesting of the barriers for expediency and cost savings during transportation of the barriers from a production site to the site of the container manufacturing operation. At the container's production site, the stacks of stacked barriers enable quick and easy feeding of the barriers in sequence into the containers. Each nested barrier can be extracted from its stack into its intended container under the influence of a first negative pressure in the container jacket, where each barrier when inserted into its container shuts off the negative pressure; alternatively, each nested barrier can be blown with air from its stack into the intended container. The next container jacket is fed under the stack of nested barriers, and the same sequence of events continues for the next container and next barrier. Containers continue to be fed in sequence under the stacks of barriers, and the fact that they are stacked together ensures a high speed and a very simple feeding operation.

In order to overcome the problem of permeation of the propellant and/or product through the barrier found in previously known dispensers, the flexible barrier in accordance with the present invention is alternatively made of a multi-layered material. FIG. 6 shows a wall structure consisting of an inner layer 102 designed to prevent transport of propellant and product. The layer 102 is sandwiched between the outer layers 104 and 106 which are inert to the propellant or product in contact with the outer layers. Adhesive layers 108 and 110 are optionally provided, or alternatively the inner and outer layers 102, 104 and 106 can be fused together with heat or other means. In one embodiment, the inner layer 102 is a gas barrier layer and the outer layers 104 and 106 are barrier layers for aqueous or organic fluids. The gas barrier layer can be made of PET, ethylene vinyl alcohol, polyvinyl alcohol, polyvinylidene chloride, polyacrylonitrile, cellophane or other similarly suitable materials. The outer layers can be made of PET, polyethylene, (special high-density polyethylene) polypropylene, polytetrafluoroethylene, polybutane, sulfur ions, butyl rubber, polyvinylidene chloride, polychlortrifluoroethylene, penton, polyvinyl fluoride or other similarly suitable materials. Ethylene vinyl alcohol and polyvinyl alcohol are preferred gas barrier materials and high density polyethylene is a preferred aqueous or organic fluid barrier material.

Possible propellants known in the art can be used with the dispenser and flexible barrier according to the present invention. The barrier according to the present invention requires smaller quantities of liquid propellants than is required in non-barrier aerosol-package systems and in certain barrier-package systems that use pressurized gases, which thus enables the economic use of more expensive propellants. The present system lends itself to a maximization of the amount of product to be dispensed from a given container.

IN

The barrier package according to the invention as described on pages 7 and 8 is currently manufactured using a forming process generally referred to as thermoforming. The thermoforming technique for producing plastic molds from a foil of plastic material is well known in a general sense. Certain modifications of the general; techniques are used to tailor the thermoforming process to form a specific shape. The schematic representation in FIG. 8 shows the many steps involved in forming barrier packages according to the present invention. In step 1, plastic foil material is introduced, e.g. PET, with a thickness of 0.635 mm through a dry heating zone (oven) to bring the PET to a molding temperature of 121°C - 166° C. It is desirable to obtain PET at 140° C - 149° C, i.e. to avoid the outer limits in the range 121"C - 166°C. The PET material that has been found suitable for forming the barrier seals is biaxially oriented and suitable for thermoforming by deep drawing.

The barrier gasket according to the present invention is a deep drawing part and is thus subject to "webbing", i.e. the formation of a fold of the excess material at the mold base and the side wall of the barrier. Where webbing is a concern, accurate control of the temperature in the plastic film material is critical. Furthermore, with temperature control and avoidance of a temperature above the distortion temperature of the plastic film material, a degree of plastic memory is retained in the plastic material, this memory helps to exclude or remove the problem of "webbing".

In step 2, the preheated PET foil is moved to the forming station (thermoformer), where the PET foil is pre-stretched using a "plug helper" for the first shaping of the inner wall segment and stamp area in the barrier package and when using of a "ring" to partially shape the outer wall segment. See also FIG. 9. The "ring" helps to avoid "webbing". The "plug helper" and "ring" are mounted on the upper movable plate (upper base plate) of the thermoforming equipment, directly across from the lower movable plate (bottom plate) on which the mold is mounted. After placing the heated plastic foil between the upper and lower plates, the forming operation continues by moving the plates towards each other to clamp the heated foil. During the course of moving the plates until their final contact with each other, the "plug helper" and "ring" pull the film into and around the inner cavity surface of the mold to force the heated PET film to conform and contact the mold at the crease which connects the outer wall segment and the inner wall segment and at the bottom of the "ring". The "ring" that forces the PET plastic film against the bottom plate of the thermoforming equipment provides an annular seal around the mold. After performing the sealing, negative pressure is applied to

in

the mold to cause the PET plastic film to be pulled against the surface of the mold and thus complete the final shaping of the PET plastic film.

The mold is water-cooled, Teflon-coated aluminum, heat-conducting, and the "plug helper" and "ring" are finely ground wood

in

covered with felt to avoid chafing and sticking of the formed part.

After sufficient cooling, the upper and lower plates are separated and the formed foil transported to the trimming station (step 3) where cutting trays trim the formed parts. The shaped parts are thrown out to a stacker and the trimmed residue in the sealing surface is ground for recycling and reused in the plastic film's extruding process.

IN

It is assumed that biaxial orientation of the plastic during the extrusion of the plastic foil to be thermoformed reduces penetration into the barrier material.

in

To fabricate a barrier with a thicker outer wall segment 12 from the termination flange 16 to the tray 15 as previously described, it may be necessary to resort to "blow molding" processes that utilize controlled blow ends

in

for the appropriate design. Such production techniques are well within the knowledge of the person skilled in the art.

in

While the invention has been particularly shown and described with reference to illustrated and preferred embodiments thereof, it is to be understood by those skilled in the art that the foregoing and other changes in form and details may be made without deviating from the spirit and framework of the invention which shall be limited only by the scope of the attached requirements.

Claims (18)

1. Dispenser, missing propellant4 and product, which is suitable for product dispensing with pressure, comprising: a container with a bottom, a side wall, a top, an opening in the top for mounting an externally activatable valve inlet, and a closable opening! at the bottom, for introducing propellant into the container; an externally activatable valve device passing through it upper opening for dispensing product from inside the container; in a unitary flexible and extendable barrier seal between the side wall and the top of the container to define a first zone above the barrier to keep the product in fluid communication with the valve means and a second zone below the barrier to keep a propellant out of fluid communication with the first zone; which barrier has a formed spatial shape with a closing sealing device, a flexible and expandable wall section and a central piston area, which sealing device, wall part and piston area are designed as a uniform spatial shape with sufficient rigidity to maintain its shape before and during insertion into the container; charac- serted in that the flexible and expandable wall section has in an inner wall segment spaced apart and connected by a fold or fold; the outer wall segment runs from the final sealing in- in direction to the fold, the inner wall segment extends from the fold along the inner surface of the outer wall segment; IN the central piston area is connected to and extends over the area bounded by the circumference of the inner wall segment to close and complete the unitary barrier element; the inner wall segment has sufficient flexibility to allow the inner wall segment and the central piston region to move in an axial direction within the container. 2. Dispenser according to claim 1, characterized in that the outer wall segment has a steep conical truncated shape that goes from the closing sealing device to the fold, the outer wall segment and the fold are dimensioned so that when the barrier is introduced into the container, a first distance relationship is formed with the inner side of container surface; and the inner wall segment is an oppositely directed, steeply conical truncated shape which is held within the outer wall segment and extends from the fold. 3. Dispenser according to claim 1, characterized in that the outer wall segment and the inner wall segment form an acute angle which ends in the fold. 4. Dispenser according to claim 1, characterized in that the uniform barrier consists of PET. 5 . Dispenser according to claim 1, characterized in that the inner wall segment is somewhat shorter in top to bottom dimension than the outer wall segment. 6. Dispenser according to claim 1, characterized in that at least part of the central piston area is thicker and stiffer than the inner wall segment. 7. Dispenser according to claim 1, characterized in that the final sealing device is a running flange in outwards from the outer wall segment. in 8. Dispenser according to claim 1, characterized in that the central piston area has an outer periphery which starts from the inner wall segment at , a significant angle to the in inner wall segment. 9. Dispenser according to claim 1, characterized in that the barrier is multi-layered, the inner layer is impermeable to transport of product and propellant and the outer layers are inert to the product or propellant continuously with it. in in 10. j Dispenser according to claim 2, characterized in that the uniform barrier consists of PET. 11. Dispenser according to claim 2, characterized in that the uniform barrier can be largely completely inserted into further identical barrier elements, the conically truncated outer and inner wall segments and intervening fold for each barrier which can be laid into corresponding parts of further identical barrier elements. in 12. Dispenser according to claim 2, characterized in that the central piston area is flexible and expandable. 13. Dispenser according to claim 2, characterized in that the inner wall segment is somewhat shorter in top to bottom dimension than the outer wall segment. 14 . Dispenser according to claim 2, characterized in that the outer wall segment is thicker and stiffer than the inner wall segment. 15 Dispenser according to claim 2, characterized in that at least part of the central piston area is thicker and stiffer than the inner wall segment. 16. Dispenser according to claim 2, characterized in that the final sealing device is a flange that extends outwards from the outer wall segment. 17. Dispenser according to claim 2, characterized in that the central piston area has an outer periphery which is connected at a significant angle to the inner wall segment. 18. Dispenser according to claim 2, characterized in that the barrier is multi-layered, the inner layer is impermeable to the transport of product and propellant and the outer layers are inert to the product or propellant continuously with it.