This invention relates to product dispensing containers wherein the container contents are forced out by internal pressure, usually under control of a valve at the top of the container. More particularly, this invention relates to a sealed package to be inserted in such a container to develop the dispensing pressure.
U.S. Patent No. 3,718,236 discloses a system for generating pressure within a dispensing container by mechanically combining two or more reactive chemicals in a sealed bag-like structure free-floating within the container. In one disclosed arrangement, the bag includes a number of sealed compartments containing sodium bicarbonate which are ruptured to combine that chemical with a mixture of citric acid and water so as to develop gas pressure within the bag. The rupturing of these compartments is carried out sequentially as the dispensing operation proceeds, in order to develop successive increments of additional pressurized gas as required to maintain an approximately constant pressure within the container as the contents are dispensed.
The bag-like structures shown in U.S. Patent 3,718,236 are relatively complex and difficult to manufacture by conventional processes. Although the basic structure can be sub-divided into simpler components for separate manufacture, that approach requires processing by at least two different types of machines to make the complete assembly, thus resulting in undesirably high cost.
European Patent Publication No. 0 044 887 discloses a bag-like package of the above-described type wherein a first outer sheet member is formed with a plurality of pockets opening into the interior of the bag-like package. At least one of the pockets contains a first chemical component of a set of chemicals to be reacted together to form an initial dispensing pressure. A second component of the set of chemicals is disposed within the package for reacting with the first chemical component to develop the initial dispensing pressure. The plurality of pockets includes a set of pockets containing additional chemical material capable of reacting with at least one chemical of said set of chemicals to develop further dispensing pressure. The bag-like package further comprises a second outer sheet member sealed peripherally to the first outer sheet member. A tape member is disposed between the first and the second outer sheet members and positioned over the first openings of the set of pockets. The tape member is releasably sealed around the peripheries of the openings of the set of pockets to the first outer sheet member and is substantially permanently sealed to the second outer sheet member to provide for progressive lift-off of the tape member from the first outer sheet member.
The present invention is directed to improvements in the bag-like package of EP-A 0 044 887. It is an object of the invention to provide means adapted for retarding the flow of liquid out of at least one pocket, and thereby controlling the degree of an initial chemical reaction commenced upon placing the package into a vertical orientation. In accordance with the invention the one pocket containing the first chemical component comprises a plurality of separate sections formed to allow communication therebetween, while another pocket is provided in the first outer sheet member for holding a charge of the second chemical component.
Other objects, aspects and advantages of the invention will in part be pointed out in, and in part apparent from, the following description of a preferred embodiment of the invention, considered together with the accompanying drawings.
Referring now to Figure 1, there is shown a sheet of flexible plastic packaging material 20 which is transported (from left to right) to a forming station 22 by conventional conveying means (not shown). This sheet may for example be a 2-layer film or web comprising polyethylene/ polypropylene, with the polyethylene facing upwards. In the station 22, thermoforming operations are carried out in accordance with known processes to form the sheet 20 with a number of pockets generally indicated at 24, 26 and 28, and adapted to receive chemicals to be reacted together for developing gas pressure.
In typical machine operations, such thermoforming of the sheet 20 preferably is carried out in multiple across the width of the plastic film 20, for example, four abreast, as shown in Figure 1 between the machine frames 29. However, to simplify the presentation, only one of the four identical formed sections will be described in detail hereinafter.
Returning now to the detailed description, the first of the formed pockets 24 may be circular in plan view, and provides a cell for holding one or more tablets or capsules containing citric acid in solid form. The second of the pockets 26 is developed in this embodiment as three distinct but intercommunicating rectangular cells for holding a mixture of bicarbonate of soda and water. The remaining set of pockets 28 provides a number (seven in this case) of separate but closely adjacent cells for holding citric acid in the form of a solution. The pockets 24-28 are filled with chemical materials as set forth above (not shown in the drawings), in any convenient way, at the station 22 or at a subsequent station.
Thereafter, the formed and filled sheet member 20 is transported to another station 30 (Figure 2) where a rectangular tape 32 is positioned over the set of pockets 28 and is heat-sealed to the sheet member 20 around the peripheries of the individual cells, e.g. closely adjacent the open mouths of the pockets, as illustrated by the shading at 34. The tape 32 is a strip-like member of flexible plastic material. This tape is heat-sealed uniformly but lightly to the upper surface of the bottom sheet 20 in such a way that it can be pulled away with relatively low force, e.g. 300 to 1000 grams per inch of width. The tape may for example be a 3-layer film comprising polyethy- lene/polyester/polypropylene, with the polypropylene being the bottom layer sealed to the polyethylene layer of the bottom sheet member 20 and advantageously providing the light-force peelability as described. Peelability in this case means that the pull force should be sufficiently light that the two films can readily be separated without resulting in any tearing of the films.
With the tape 32 sealed in place as described, the bottom sheet 20 is moved forward to a subsequent station 38 (Figure 3) where a second sheet of flexible plastic packaging material 40 is applied over the first sheet 20 and the tape 32, as with the aid of a laydown roller 41. This second sheet is heat-sealed in peripheral fashion around the first sheet, as indicated by the shading 42, to form a strongly sealed enclosure encompassing all of the pockets 24-28 as well as the tape 32. This top sheet 40 also is secured to the tape 32, as by heat-sealing the two together along a narrow line 44 adjacent the pockets 28. This seal, like seal 42, is a strong seal capable of holding the films together during normal operation of the package, capable of resisting a force order of magnitude greater than the force needed to open the peelable seal 34. Thus the seals 42 and 44 effectively serve as welds, whereby application of a sufficiently large force would tear the film material rather than open the seal. Figures 4-6 further illustrate the sealing configuration, with certain aspects of the interfilm spacing somewhat exaggerated to clarify the relationships involved. See also Figure 7 for an overall perspective view of the final package.
The top sheet 40 may for example be a 2- layered film or web consisting of polypropylene/ polyethylene, with the polyethylene on the lower (inner) side, facing downwards towards the tape 32. This combination of materials provides for a very strong seal between the top sheet and the tape at 44, and between the top and bottom sheets at 42, because both are polyethylene-to- polyethylene seals.
It may be noted that if the heat applied in making the seal 44 also produces unintended sealing between the tape 32 and the bottom sheet 20, it will be a weak polypropylene-to-polyethylene seal, using the types of sheet and tape materials suggested above, and will not interfere with the pulling of the tape up from the bottom web with only a light pulling force. When making the seal 44, the amount of heat reaching the interface between the tape 32 and the bottom sheet 20 will be significantly less than that producing the seal 34, when using comparable heat sealing devices for both seals 34, 44, so if an inadvertant seal develops along line 44 between the tape and the bottom sheet it will be of even less strength than the light-force seal between the tape and the bottom sheet at the seal line 34. It will of course readily be understood by those skilled in the art that other techniques can be used for establishing a strong secure seal between the top sheet member 40 and the tape 32 along line 44 while assuring that the tape can readily be peeled up away from the bottom sheet member with only a small force.
The completed package thereafter is cut from the forming webs and is ready for use. When the package is tilted, the water and sodium bicarbonate mixture in the cells 26 will flow to the tablets or capsule in cell 24, thus starting gas production within the sealed package. Gas production will normally be slow enough to allow time to load the package into a dispensing container, particularly if the known means are employed to slow down the reaction.
As a dispensing operation proceeds, the package expands to fill the space left by the dispensed contents. Thus the two sheet members 20 and 40 are gradually forced apart, especially in the central region adjacent the seal line 44. This expansion thus also lifts up the tape 32 in a progressive fashion, starting at the inner edge of the tape which runs parallel to the seal line 44, and moving outwardly towards the side edge of the package, across the set of pockets 28. Since these pockets are staggered, the progressive lift-up of the tape causes the individual cells to be opened sequentially, thus developing successive additional increments of gas pressure to tend to maintain the internal container pressure approximately constant.