MXPA97000473A - Member of flexible barrier useful in deaero supplies - Google Patents

Abstract

The present invention relates to a spout, without impeller or product, for dispensing product under pressure, comprising: a container having a bottom, a side wall, an upper part, a hole in said part for mounting a valve device that it can be activated externally, and an opening that can be closed in said bottom to introduce the impeller into said containers, an externally activatable valve device that extends through said upper opening to supply product from the part internal of said container, a flexible and unitary expandable barrier sealed between the side wall and an upper part of said container to define a first zone above said barrier to maintain the product in fluid communication with said valve device and a second zone of said barrier to prevent an impeller from entering into fluid communication with said first zone, said barrier having a spatial shape which e has a spatial shape has a terminal seal device, a flexible and expandable wall part, and a central piston region, said sealing device, wall part and piston region is formed in a special unitary manner with sufficient rigidity to maintaining its shape and during insertion into said container, said flexible and expandable wall portion having an inner wall segment and an outer wall segment spaced apart therebetween and connected by means of a fold, said outer wall segment extending to from the terminal sealing device to the fold, and said inner wall segment extending from the fold along the inner surface of the outer wall segment, said central piston region being connected to the area defined by the circumference of the wall. inner wall segment and extends through said area to close and complete the unitary barrier member, said inner segment The wall has sufficient flexibility to allow said inner wall segment and said central piston region to move in an axial direction within the container.

Description

MEMBER OF FLEXIBLE BARBERA USEFUL IN AEROSOL SPRAYERS This application is a continuation in part of the application of North American Patent No. of Sene 08 / 253,143, filed on June 2, 1994, under the title "Flexible Barper Member Useful Ip Aerosol Dispensers ", (Flexible Flexible Barrier Member in Aerosol Spouts), which to its vr is a part of 13. 13. Application of North American Patent No. of Sene 08 / 084,638, filed on January 29, 1993 , under the title "Fle? b3e Barrier Member Useful In Aerosol Dispensers." (Member of Barrera Fie: Useable in Aerosol Spouts). BACKGROUND OF THE INVENTION 1. FIELD OF THE INVENTION This invention relates to pressurized dispensing containers, such as for example aerosol containers, where the product has to supply and the means that generates the pressure, that is, the propellant, are kept isolated by a separation on opposite sides of a barrier. The aerosol container of this type is generally known as a "barrier package" aerosol container. 2. DESCRIPTION OF THE PREVIOUS TECHNIQUE The aerosol barrier packages of the prior art are of at least three general types. In the piston-type barrier package, the barrier is a piston-like component mounted on the container in a slit relationship with the internal surface of the container. The product to be supplied is placed on the valve side of the piston and the impeller, which generates the pressure inside the container, is on the opposite side of the piston. Aerosol H3ndbool, Second Edition, 1982, describes a piston-type aerosol dispenser operated by American Can Company ba or the commercial name "iti G? -Flo". At the Mira-Fio jet, the piston skirt is designed in such a way that it seals against the sides of the container to prevent the drive gas from passing into the product chamber on the other side of the piston. The activation of the air discharge valve causes a reduction of the pressure in the product chamber resulting in the pressure in the impulse chamber pushing the ison towards the discharge valve and causing the discharge of the product through the valve. discharge valve. US Patent Nos. 3,022,923, 3,756,476 and 3,929,132 describe examples of a piston-type barrier package. In a second type of aerosol barrier package, a flexible, foldable bag is placed within the container opening, either in the aerosol discharge valve or in the container opening count. At the end of the 1960s, Continental Can Company introduced an aerosol barrier spout known as the "Sepro-Ca". The Sepro-Can includes an inner plastic product bag having an opening that fits over the valve opening in the upper part of the container. The side walls of the bag extend along the side walls of the container and are folded like an accordion so that the bag can be folded inwardly and upwardly under the influence of the pressure on the remainder of the container as empty the bag. A barrier package of the second type is illustrated in U.S. Patent Nos. 3,788,521, 3,896,970 and 4,067,499. Bar-type modifications of the second type include fixing the bag on the side wall of the tank or the joint formed between the side wall of the tank and an upper part of the tank. A third type of barrier package of the prior art is a deployable cup shaped barrier where the barrier has an outer wall that terminates in a sealing flange, said outer wall being positioned adjacent to the outer wall of the container. The inner wall of the barrier is imminently bent within the outer wall, the inner wall ends in a final closing part. The barrier is found in an aerosol container with valve and is sealed at the joint formed between the side wall and the bottom end closure of the container. The product penetrates through the valve opening of the container and the impeller through a hole in the bottom end closure of the container. Vacuuming the valve reduces the pressure in the product compartment and results in the internal wall of the barrier unfolding from within the outer wall of the barrier and causing the end closure part of the inner wall of the barrier advances and therefore pushes the product towards the discharge valve. A patent that illustrates this third type of package? barrier of the prior art is the North American Patent Na. 3, 109,463. One problem with the piston-type barrier package of the first type is imperfect sealing between the side skirt of the piston and the side wall of the container which allows the impeller to leak into the product with the consequent discharge of impeller during the discharge of the product as well as contamination of the product with the impeller. Likewise, aerosol containers are often dented and consequently lose their perfectly circumferential shape, with the consequence that the piston can not move axially inside the container beyond the dented indenture. A problem with the barrier packs, of the second type where the barrier is fixed on the valve or the valve opening of the container is that the barrier collapses in such a way that it causes the formation of a product bag within the barrier folding with the consequent undesirable decrease in the evacuation of the product from the container. In the third type of barrier package of the prior art described herein, the deployable cup-shaped barrier does not progress progressively and uniformly against the inner wall of the container but tends to create pockets and trap the product against the wall or at bags formed on the same wall as it unfolds. Attempts to solve these problems have included the addition of an additional rigid piston to the end portion of the inner wall, or the adhesion of the outer wall of the barrier removably on the inner wall of the container. Generally, barriers of the third type can be difficult to form, as well as to be inserted into the container and sealed with it. Therefore e; is the need for a flexible product / moulder barrier for an aerosol container that is easy to manufacture and transport, easy to insert into the container and forms a seal with said container, which prevents fluid leakage from a compartment towards the other compartment, and that does not form bags and therefore prevents the evacuation of significant quantities of the product to be discharged. COMPENDIUM OF THE INVENTION The present invention relates to an improvement in the third phase of the barrier package. In a broader aspect, the present invention relates to a unitary expandable and flexible barrier for use in a valve pressure vessel, with several zones, where the barrier has a spatial shape with sufficient rigidity to maintain its shape before insertion into the pressure vessel with valve, with several zones, and its use in the. The barrier comprises a flexible and expandable wall part having an outer wall segment and an inner wall segment connected by means of an angled fold, the free terminal end of the outer wall segment forms a sealing means and the end of the segment of internal wall distal in relation to the fold extends in a region of central piston that closes the barrier. In a preferred embodiment, the outer wall segment is markedly frusto-conical in shape and terminates at its free end in a sealing device, and the inner wall segment is placed in a juxtaposed relationship with the inner surface of the outer wall and is in a marked frustoconical shape opposite the frustoconical shape of the outer wall segment to form a small clot between the outer wall segment and the inner wall segment; the end of the inner wall segment 1 in relation to the fold is closed by a central piston region to thereby complete the unitary barrier member. Further, the inner wall segment is sufficiently flexible to allow the inner wall segment and said central piston region to move in an axially downward direction under the influence of product pressure when the barrier is sealed at the top inside. of the container, to have a more or less pale configuration. Additionably, the outer and inner wall segments have sufficient flexibility and expandability to extend outwardly under the influence of the product pressure to conform substantially to the inner surface of the container. When the outer wall segment is sufficiently thick and stiffer than the inner wall segment, the outer wall segment will tend to continue to conform substantially to the internal surface of the container, and the segment > ie flexible inner p3red will be inverted within the outer wall segment under the influence of the impeller pressure to substantially return the barrier to approximately its shape as initially disposed in the container. Then, the inner wall segment and the central piston area extend radially outwardly and upwardly to substantially remove the product from 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 impeller pressure, followed by the tight wrinkling together and the upward movement of the two segments of external and internal wall. In the latter case, at least in the case of products of viscosity b3, the product will be substantially evacuated from the container. Due to sufficient stiffness to maintain its shape prior to insertion into the container, as well as the presence of the tapered outer wall segment, the barrier of the present intention can be inserted very easily into the upper part of the container. Due to the tapered outer and inner wall segments, the barrier can be nested with similar barriers for convenience and cost savings in freight. In addition, nesting facilitates rapid and simple mechanical feeding of stacked barriers to the container. In a preferred form of the present invention the outer wall segment is thicker and stiffer than the inner wall segment; the inner wall segment is also of a length slightly smaller than the outer wall segment; and the sealing means is a radially extending flange that acts as packing between the upper part of the side wall of the container and the upper closure of the container. The central piston region may also be thicker than the inner wall segment. A particularly useful barrier material is polyethylene terephthalate < PET). When per- aeration through the barrier is a concern, the barrier of the present invention can be employed in a single-unit unit configuration. Such multi-layer ion configurations, their construction materials and their manufacture are well known to those skilled in the art. Generally speaking, in a three-layer system, the inner layer is made of a material that impedes the transport of the impeller and the product and the outer layers are inert to the impeller and the product. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view in elevation of a modality of the barrier of this invention. Figure 2 is a sectional elevation view of the barrier of Figure 1 placed inside an empty aerosol container with the upper opening of the container shown schematically and the aerosol valve not shown. Figure 3 is a schematic view of the barrier of this invention within an aerosol container showing the barrier in a position after loading the product into the container but before introducing the impeller into the reservoir. Figure 4 is a schematic view of the barrier of this invention within an aerosol container after partial evacuation of the product from the container.

Figure 5 is a schematic view of the barrier of this invention inside an aerosol container after the additional evacuation of the product and after the return of the barrier to its initial shape in the aerosol container, also showing in dotted line a total evacuation of the product. Figure 6 is a partial sectional view of a multi-layer barrier of the present invention. Figure 7 shows barriers of this invention in the nested relationship. Figure 8 is a schematic diagram of the various steps employed in the manufacture of the barrier package of this invention from a plastic sheet. DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, Figure 1 shows a unitary barrier generally indicated as 10, as or is formed in e, said barrier having a. wall 11 comprising a flexible and expandable outer wall segment 12 and a flexible and expandable inner wall segment 14 connected by means of a fold 15, the outer wall segment 12 ends in a sealing flange 16. In the e; 18 of the inner wall segment 14, the piston region 20 extends inward to close the barrier. It should be noted that the outer wall segment 12 has a markedly frusto-comca shape extending from the sealing flange 16 towards the fold 35, and that the inner wall segment 14 has a markedly fruto-conical shape directly opposite. to the outer wall segment 12 extending from the fold 15 to the central piston region 20. The outer wall segment 12, including the sealing flange 16, is thick and stiff enough to provide a spatial shape to the barrier and causes the barrier to be able to stand freely and be ready to be inserted in the container. It has been found that a barrier formed of PET with the following dimensions, has had satisfactory performance as a barrier in a container under pressure: Thickness of the sealing flange - .01778 cm Thickness of external wall segment - .01778 cm adjacent to the flange becoming narrower to .01016 c in the leg leg Thickness of internal wall segment - .01016 cm adjacent to the fold becoming narrower up to .00508 cm adjacent to the central p? s.ton region Central piston region - .00508 cm at the junction of the inner wall segment and 13 central piston region and increasing to .01016 cm immediately within the aforementioned joint and becoming thicker up to 0.1778 cm in the central area of the piston.

Length of the external wall segment - 7.94 cm Length of the internal wall segment - 6.59 cm The container used with the above described PET barrier had a straight-sided cylinder of 202 x 509 of 5.40 cm and 34.20 cm in length. The barrier has a taper of 1 * in each of the outer and inner wall segments, 12 and 14, respectively, to form a fold 15 that provides an included angle of 2o between the inner and outer wall segments, 12 and 14 It is believed that a taper of 3o in each of the internal and external wall segments would also work in a satisfactory manner. The central piston region for the above-described barrier has a configuration as shown in FIG. 1, where the term 18 on the perimeter of the piston has a depth of 0.47752 cm and a radius of 0.16002 cm. The seal flange 16 for the described barrier has a turning radius in the external wall segment 12 of 0.19812 cm. Figure 2 shows the barrier 10 inserted in a pressure vessel with valve, generally indicated by the number 22 having an internal wall surface 23, and permanently attached to the receiver 22 by means of the sealing flange 16 by means of a fold of the flange 16 between the joint formed by the upper end 25 of the side wall the container 22 and the perimeter of the upper closure 27 of the retentate 22. Without intending to limit the type of pressure vessel (aerosol) with which the barrier package of this invention can be usefully employed, it has been found especially useful when used with an aerosol container commonly known as an "internal recess" container. A sealable orifice 28 is provided in the lower closure 26 for introduction of the impeller. A manually actuated valve (not shown) is pumped in a manner well known to those skilled in the art at the opening 29 of the pressure vessel 22. In FIG. 2, the barrier 10 divides the inner part of the container into several areas under pressure; the upper zone 33 for receiving the product to be supplied and the lower zone 35 for receiving the impeller. In general terms, the container manufacturer will insert the barrier 10 into the container 22, and seal the barrier on the container in accordance with what has been described above. A product refill will then fill the product and the impeller 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 area 33 to cause the barrier 10 to expand fully downwardly within the container 22 to conform substantially to the internal surface 23 of the container 22, as shown in Figure 3. During the filling of the product into the container it can It is necessary to provide a device for evacuating the air in the impeller and / or product area. After introducing the impeller into the impeller area 35, the container is ready to operate to discharge the product by activating the aerosol valve positioned in the opening 29 of the container. Figure 2 shows a configuration for attaching the barrier 10 to the container 22. Figure 2 shows the barrier package 10 having a terial flange 16 extending from the outer wall segment 12. The flange 16 fits tightly between the flanges 25 and 27. The seam is formed by winding the flanges 25, 27 and 16 towards the side wall 12 to form a rolled seam by techniques known to those skilled in the art. The thickness and length of the sealing flange 16 are dictated by the requirements of the rolled seams, which may vary according to the type of container and the type of winding. The sealing flange 16 / may be thicker than the outer segment 12 of the adjacent wall. The sealing flange 16 can function as a packing to seal the barrier on the base of the container. If necessary, an adhesive can be provided to the components that must be joined by scraping.

Figure 3 shows the barrier in an initial position shortly after loading the container with product. By continuously or intermittently activating the valve positioned in the upper opening of the pressure or pressure vessel, the product will be evacuated from the container by lowering the pressure in the product zone 33 and causing the greatest pressure in the impeller? reversing the inner wall 14 of the barrier IO inside the external wall 12 and thus pushing the product through the discharge valve of the container. As the product of the container 22 is evacuated, the inner wall segment 14 and the central piston region 20 are moved axially towards the aerosol discharge valve as the bairn reverses, as shown in Figure 4. If the segment 12 of the wall has a sufficient thickness everywhere from the terminal flange 16 towards the fold 15, then the external wall segment will continue to adapt substantially to the internal surface 23 of the container wall during the entire evacuation of the product as shown schematically in Figures 4 and 5. The barrier then returns to its initial shape comma as shown in Figure 5, followed by radial and axial stretching of the intern segment 34. of wall and central piston region 20 toward the dotted line configuration shown in figure 5 to obtain a substantially complete evacuation of the product from the container. To obtain this action, the thickness of the external wall segment 12 should be substantially greater than the aforementioned 0.01778 cm thickness; without wishing to be limited in any way, the thickness may be of the order of 0.0508 cm to 0.0635 cm from the flange 16 to the fold 15, or of sufficient thickness to obtain a complete inversion of the internal wall segment within the outer wall segment presented in figure 5. With this narrower outer wall segment, more viscous products can be completely evacuated from the container without significant bag formation. The internal wall segment will remain thin and reliable. If the external wall segment 32 has a thickness of the order of 0.01778 cm, the transition from Figure 4 to an almost complete evacuation of the product will result in internal and external wall segments, 12 and 14, wrinkling inward and squeezing between them. and moving up. In this case, using water as a simulated product, a substantial evacuation to the complex entity of the product was obtained from test conditions without training if the test bag without formation means stock exchange. When using more viscous products, however, it is expected that the thicker walled product 12 will need to be employed to obtain a complete evacuation of > The product information means stock exchange. It has been observed that the frusto-conical configuration of the inner wall segment 14 results in the first internal wall segment being progressively inverted in an axial direction within the external wall segment 12, when the outer wall segment 12 is sufficiently thick, to cause the progressive advance of the product towards the discharge valve and minimize the capture or treatment of product in the bag. The ahusamienta of the external wall segment facilitates the imagination of the barrier of the present invention in the container under pressure. The presence of the ahusamienta of both the internal wall segment and the external wall segment, and at small angles, also allows optimal nesting of the barriers for convenience and to save shipping costs from the barriers of the manufacturing site to the place of operation of container manufacture. At the container manufacturing site, the rows of knotted barriers facilitate quick and easy feeding of the barriers sequentially in the containers. Each knotted barrier can be installed from the row and placed in the proper container under the influence of an initial vacuum in the container's envelope, each barrier closing the vacuum when inserted into its container; At the same time, each nested barrier can be blown by means of a re from its rows in the proper container. The next container shell is fed under the row of nested barriers, and the identical action continues the next container and the next barrier. The containers continue to be sequentially sequestered to the entity under the nested barrier rows, and the nested conduit provides a high speed and very simple feeding operation. To overcome the problem of impeller and / or product permeation through the barrier found in the prior art dispensers, the single barrier in accordance with the present invention is constructed op cally from a multi-layer material. . Figure 6 shows a wall construction consisting of an internal inner layer 102 designed to prevent the transport of impeller and product. The layer 102 is inserted between the outer layers 104 and 106 which are inert relative to the impeller or the 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 306 may be fused together thermally or by other means. In one embodiment, the inner layer 102 is a gas barrier layer and the outer layers 104 and 106 are barrier layers to 3 organic or aqueous fluids. The gas barrier layer can be made from PET, ethylene vinyl alcohol, alcohol, or polyvinyl chloride, polyvinyl chloride, cellophane, or other suitable materials. . The outer layers can be made of PET, filled poly (especially high density polyethylene), polypropylene, polytetrafluoroethylene, polybutene, sulphide, butyl rubber, polyvinyl chloride or ideno, pol. orotpfl uoroeti wood, pentop, polyvinyl fluoride or other similarly suitable materials. As the gas barrier materials, polyvinyl and vipyl alcohol are poured from the full and high density palethylene is preferred as a barrier material to the aqueous or organic fibers. Any impeller known in the art can be employed with the spout and the flexible barrier of the present invention. The barrier of the present invention requires smaller amounts of impellers in the liquid state than the amounts required in package aerosol systems that do not have barriers and in certain barrier package systems that use compressed gases, thus allowing economical use of the most expensive drivers. The present system lends itself to an optimization of the quantity of product to be supplied from a side container.

The barrier package of this invention in accordance with that described in the preceding pages of the present text is currently manufactured using a ing process generally known as thermoion. The technique of thermoing the manufacture of plastic s from a sheet of plastic material is a well-known technique in general. Specific modifications of the general techniques are used to adapt the thermo procedure to the ation of a specific . The schematic diagram of Figure 8 shows the various steps involved in the ation of the barrier packages of this invention. In step 3, the plastic sheet material, PET, example, having a thickness of 0.0635 cm, passes through a dry heating zone (furnace) to bring the PET to a ing temperature of 121.1 ° C - 165.5 'C. It is desirable to have the PET at a temperature comprised between 140.5 ° C and 148.8 ° C that is to avoid the extremes of the range of 121. lSC - 165. S'C. The PET material suitable the ation of the barrier packages is biaxially oriented and suitable a deep stretch ion thermoing. The barrier package of this invention is of deep anger and there is susceptible to "getting confused", that is to say, a fold can be formed with the excess material in the mold base and the barrier side wall. When "embroiled" is a concern, the precise control of the temperature of the plastic sheet matepal is a critical factor. In addition, by controlling the temperature and preventing the temperature from rising above the distortion temperature of plastic sheet material, the plastic material retains a degree of plastic memory, and this memory helps to avoid or eliminate the problem of "embroiled". In step 2, the preheated PET sheet is moved to the forming station (thermoformer), where the PET sheet is pre-stretched using a "pin" for the initial formation of the inner wall segment and the outer region. piston dc? l barrier pack and using a "ring" to form the segment e: wall fear. The "ring" helps to avoid "embroiling". The "aid pin" and the "ring" are mounted on the upper movable plate (base plate at the top) of the thermoforming equipment, directly through the lower movable plate (base plate) where the assemble the mold. After placing the heated plastic sheet between the upper and lower plates, the forming operation starts by moving the plates towards each other to match the heated sheet. During the course of the displacement of the plates until their last contact between them, the "plug of auda" and the "ring" will stretch the ho a in and around the inner surface of the mold cavity to force the PET sheet heated to conform and come into contact with the mold in the fold joining the external wall segment and the inner wall segment and the base of the "ring". The "ammo" by forcing the sheet of PET plastic against the base plate of the thermoform ion equipment effects an annular seal around the mold. After achieving the seal, vacuum is applied to the mold to cause the stretch of the PET plastic sheet against the mold surface and thus complete the final formation of the PET plastic sheet. The Teflon coated aluminum mold, water cooled, heat conductor, and the "help pin" and the "ring" are made of fine grain wood covered with felt to avoid splitting and adhering to the formed part. After adequate cooling, the upper and lower plates are separated and the formed sheet is transported to the finishing station (step 3) where cutting dies cut out 33S formed parts. The formed parts are ejected towards a stacker and the residue cut out in the sealing breeze is ground for recycling and its rejection in the extrusion process of plastic sheet. It is noted that the biaxial orientation of the plastic during the extrusion of the pillar to thermopharm reduces the permeation of the barrier material.

In order to fabricate a barrier with a thick walled outer segment 32 from the terminal flange 16 to the fold 15 as described herein, it may be necessary to employ "blow molding" methods employing partially formed controlled masses of appropriate configuration . Such manufacturing techniques are well known to those skilled in the art. While the invention has been described and presented in a particular manner in terms of preferred and illustrative embodiments thereof, it will be understood by those of ordinary skill in the art that changes can be made in form and detail without departing from the spirit nor of the scope of the invention limited only by the scope of the appended claims.

Claims (18)

1. CLAIMS 1. A spout, sn impeller or product, suitable for supplying product under pressure, comprising: a container having a bottom, a side wall, an upper part, a hole in said upper part for mounting a valve device that can activating externally, and an opening that can be closed in said bottom to introduce the impeller into said container; an externally activatable valve device 3 which extends through said upper opening for supplying product from the internal part of said re-lens; a flexible and unitary expandable barrier sealed between the side wall and an upper part of said container to define a first zone above said barrier to maintain the product in fluid communication with said valve position and a second zone indented from said barrier to prevent an impeller from entering into fluid communication with said first zone; said barrier has a spatial shape having a terminal seal device, a flexible and expandable wall portion, and a central piston region, said sealing device, wall portion and piston region is formed unitary spatially with a stiffness sufficient to maintain its shape before and during insertion into said container; said flexible and eipansible wall part has an internal wall segment and an outer wall segment spaced apart from each other and connected by means of a fold; said outer wall segment extending from the terminal sealing device to the fold, and said inner wall segment extending from the fold along the inner surface of the outer wall segment; said central piston region is connected to the area defined by the ircunference of the inner wall segment and extends through said area to close and complete the unitary barrier member; said inner wall segment has sufficient flexibility to allow said inner wall segment and said central piston region to move in an axial direction within the container. The dispenser of claim 1, wherein said outer wall segment further has a markedly frusto-conical shape extending from the terminal seal device to the fold, said outer wall segment and folds having dimensions such that upon insertion of the barrier an initial relationship spaced with the inner side of the container surface is formed in the container; and said inner wall segment is a markedly frustoconically, oppositely directed shape contained within the outer wall segment and extending from the fold. 3. The invention of the rei indicates ion 1 where the outer wall segment and the inner wall segment form an acute angle that ends in the fold. 4. The invention of claim 1, wherein said unit barrier is made of PET. 5. The invention of the rei indication 1, wherein said internal wall segment is slightly shorter in the dimension from top to bottom than said external wall segment. The invention of claim 1, wherein at least a portion of said central piston region is thicker and more rigid than said inner wall segment. The invention of claim 1, wherein said terminal seal device is a flange extending outwardly from the outer wall segment. 8. The invention of claim 1, wherein said central piston region has an outer periphery arising from the internal wall segment at a substantial angle relative to said internal wall segment. 9. The invention of claim 1, wherein the barrier has several layers, the inner layer allows neither the product nor the impeller to pass through and the outer layers are inert in relation to the product or the impeller adjacent thereto. 10. The invention of claim 2, wherein said unit barrier is formed of PET. The invention of claim 2, wherein said unitary barrier is substantially fully anidable entity with identical additional barrier members, the internal and external wall segments f rustaconic and the intervening fold of each barrier are nested with corresponding parts of members additional identical barriers. The invention of claim 2, wherein said central piston region is flexible and expandable. The invention of claim 2, wherein said internal wall segment is slightly shorter in the top-down dimension than said external network segment. The invention of claim 2, wherein said outer wall segment is thicker and more rigid than said inner wall segment. The invention of claim 2, wherein at least a portion of said center piston region is thicker and more rigid than said inner wall segment. 16. The invention of claim 2, wherein said terminal sealing device is a flange extending outwardly from the outer wall segment. 17. The invention of claim 2, wherein said central piston region has an outer periphery connected at a substantial angle relative to said inner wall segment. 18. The invention of claim 2, wherein the barrier has several layers, the inner layer does not pass through the product nor. The impeller and the outer layers are inert in relation to the product or the impeller adjacent to them.