Abstract:
The present invention is directed to an improvement for a fill valve ( 22 ) for an aerosol container ( 10, 30 ) to provide better sealing capability. The fill valve is made using a flashless injection molding process in which both the mold cavity and molding material are heated to elevated temperatures to significantly improve cross-linking which occurs during the molding process. A backside ( 22   a ) of the fill valve now has a recessed portion ( 56 ) to facilitate ejection of the valve from a mold so leak paths are not created due to the forces applied to the valve during its extraction from the mold. The recessed portion reduces the amount of material required to make the fill valve and makes the fill valve flexible to aid in providing a good seal against leakage of a propellant from the container after filling.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     Provisional patent application 60/645,679 filed Jan. 21, 2005  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     N/A  
       BACKGROUND OF THE INVENTION  
       [0003]     This invention relates to aerosol dispensing containers incorporating a bag holding a product to be dispensed and a propellant chamber formed between the bag and container sidewall, and more particularly, to an improved grommet or fill valve (sometimes also referred to as an umbrella valve or seal valve) by which a propellant is introduced into the container and retained therein until all the product in the container is dispensed. Alternately, the container may employ a piston on one side of which is the product to be dispensed and on the other side of which is the propellant chamber. Again, the improved fill valve allows a propellant to be introduced into the chamber and retained therein until all the product is dispensed.  
         [0004]     Certain types of aerosol containers include a collapsible bag or pouch disposed within the container. The bag or pouch is filled with a fluent material dispensed by the container. A propellant chamber is formed between the bag and container sidewall. At the base of the container, on a domed bottom surface thereof, an opening is formed and a fill valve is seated in this opening. During manufacture, after the bag or pouch is seated in the container and a dispensing valve attached to the top of the container, a propellant is injected into the container. For a 7 ounce container, 10-12 grams of a propellant such as butane is injected. To inject the propellant, the fill valve is unseated so propellant can flow into the chamber around the valve. The fill valve has a stem which fits through the opening, an inner sealing element formed on one end of the stem, and a “bowtie” section formed on the outer end of the stem. Opposed longitudinally extending grooves extend from the bowtie section along the side of the stem. During filling, a nozzle presses against the bowtie section of the valve and pushes the valve a sufficient distance inwardly that the butane can flow through the grooves into the chamber. In addition, pressure of the butane causes the valve to flex upwardly to create a larger opening for the gas to enter the container. When the nozzle is withdrawn, the pressure in the chamber now forces the inner sealing element of the fill valve against the inner surface of the container bottom, sealing the container. An example of this type of aerosol container is shown in co-assigned U.S. Pat. No. 5,915,595.  
         [0005]     A second type container utilizes a piston disposed in the container with the product to be dispensed being on an outlet valve side of the piston, and the other side of the piston partially forming a propellant chamber in which the butane is injected. The propellant is introduced into the container through a fill valve fitted in the base of the container in the same manner as described above.  
         [0006]     There are number of problems with current fill valves, both with respect to their design and manufacture. One significant problem occurs when a fill valve does not properly seal allowing propellant to leak out of the container subsequent to filling. Propellant leakage dramatically reduces the usefulness of a container to dispense product, and if enough propellant leaks out, the result is a “dead” container. A “dead” container is one on which, when the outlet valve is actuated, little or no product is dispensed. It will be understood that there is usually a significant time between when a container is filled and it is used. During this period when the container is being packaged, shipped, warehoused, sits on a shelf in a store, and finally purchased, any loss of propellant, however small, will affect the final usefulness of the can. It has been estimated that even a small leak can result in the loss of as much as 1 gm. of propellant a year.  
         [0007]     Other, related problems occur during manufacture of the fill valve. Heretofore, fill valves have been made using a compression molding process which has been found to result in poor sealing because of poor cross-linking of the molded material during the manufacturing process, and compression setting. Cross-linking is the formation of chemical links between molecular chains in polymers. Compression set is a property of grommets that adversely affects their sealing capability. The result has been that even if a fill valve properly seals after filling; over time, propellant can still escape from the container because of poor compression set.  
         [0008]     In addition to these factors, another factor causing poor sealing is the cryogenic process used to remove flash produced on a grommet during compression molding. After the molding process is completed, the fill valves are frozen and any extraneous material (the flash) is knocked or broken off the part. However, the freezing process can result in large and/or microscopic cracks being created in the grommet and these cracks become leakage paths for propellant to escape from the container.  
         [0009]     It will be appreciated by those skilled in the art, that release of the propellant to the atmosphere adds to our environmental problems, regardless of how the propellant escapes. In addition, one “band aid” fix to loss of propellant is to inject more propellant into the container during filling than is otherwise needed, so even if some propellant escapes there is still sufficient propellant that product is adequately dispensed from the container. Further, manufacturers, fillers, or suppliers of the containers often have to replace “dead” containers adding to their warranty costs.  
         [0010]     Another problem with previous fill valves has been that molded into each fill valve is indicia identifying the particular mold and mold cavity in which the fill valve is formed. This, of course, is to assist in trouble shooting if valves are found to be defective. Currently, this indicia is in the form of raised alphanumeric characters on one surface of the fill valve. It has been found that after manufacture, when the fill valves are placed on a conveyor which moves them to a container assembly station, the raised characters often cause the valves to not move smoothly along the conveyor, but rather more haphazardly. This can require additional manpower to insure that the fill valves do properly get to the assembly station and are properly oriented for insertion into the bottom of a container.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The present invention is directed to an improved fill valve for use in an aerosol container to provide a better sealing capability. The fill valve is made using a flashless injection molding process rather than the compression molding process previously used. As part of this process, both the mold cavity and molding material are heated to elevated temperatures and this significantly improves the cross-linking which occurs during the molding process. Further, a section of the backside of the sealing area of the fill valve now has a recessed portion that improves flexing of the seal after propellant is injected into the container, thereby creating a more responsive seal. Information about the fill valve is now engraved on an out-of-the-way surface of the valve so to facilitate conveying of the valve during manufacture of a container.  
         [0012]     This improved fill valve has a number of advantages over previous valves. One is a fill valve with more consistent dimensional and operational characteristics than previous fill valves. Importantly, the improved fill valve provides a more capable seal, and a valve less prone to the formation of leak paths through the valve. This significantly reduces the possibility of propellant leakage from a container, even containers with long shelf lives. This, in turn, reduces warranty returns and the associated costs of replacing a non-functioning or “dead” container. Additionally, because of the improved sealing capability, the reduction in leakage reduces pollution. It may also be possible to reduce the amount of propellant injected into a container during filling because, with less leakage, more propellant will remain in the container.  
         [0013]     The elimination of unnecessary raised lettering also now makes it easier to handle and move significant volumes of fill valves during fabrication of a container.  
         [0014]     Other objects and features will be in part apparent and in part pointed out hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0015]     The objects of the invention are achieved as set forth in the illustrative embodiments shown in the drawings which form a part of the specification.  
         [0016]      FIGS. 1A and 1B  are simplified representations of aerosol container using an improved fill valve of the present invention;  
         [0017]      FIG. 2  is a perspective view of the fill valve;  
         [0018]      FIG. 3A  is plan view of one end of the fill valve and  FIG. 3B  is a sectional view of the valve taken along lines  3 B- 3 B in  FIG. 3A ; and,  
         [0019]      FIG. 4  is plan view of the opposite end of the fill valve.  
     
    
       [0020]     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.  
       DETAILED DESCRIPTION OF INVENTION  
       [0021]     The following detailed description illustrates the invention by way of example and not by way of limitation. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what I presently believe is the best mode of carrying out the invention. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.  
         [0022]     Referring to  FIG. 1A , an aerosol container  10  comprises a cylindrically shaped body  12 , a bottom, dome shaped end piece  14 , and an upper cap/valve assembly  16 . A product bag  18  is disposed in the container for dispensing a fluent product, and for this purpose, the container is filled with a propellant material, under pressure. End piece  14  has a central opening or aperture  20  formed in it, and a grommet or fill valve  22  of the present invention is seated in this opening to seal it. A propellant chamber  24  is formed in the lower end of the container and a propellant such as butane is injected into the container through valve  22  to pressurize this chamber during a filling operation.  
         [0023]     In  FIG. 1B , an aerosol container  30  comprises a cylindrically shaped body  32 , a bottom, dome shaped end piece  34 , and an upper cap/valve assembly  36 . A piston  38  is disposed in the container for dispensing the product, and again, the container is pressurized with a propellant material during a fill operation. End piece  34  has an aperture  40  formed in it and grommet or fill valve  22  is seated in this opening to seal it. A propellant chamber  44  is formed in the lower end of the container and the propellant is injected into the container through valve  22  to pressurize chamber  44 .  
         [0024]     As shown in  FIG. 2 , fill valve or grommet  22  comprises a unitary valve molded of a suitable elastomeric material in a multi-cavity mold. The valve is shown to have a first section  22   a , referred to as the “backend” of the valve, a central shaft section  22   b , and a head or “bowtie” section  22   c . Section  22   a  is the greatest diameter portion of the valve. During fabrication of the container, the fill valve is pushed through opening  20  or  40  in the respective container  10  or  30 , from the inside of the container, using an appropriate tool. The “bowtie” section of the valve then projects through the respective opening to the outside of the container. The length of shaft  22   b  is slightly greater than the thickness of the dome end of the container, so there is a slight play in the valve when first installed and before the container is pressurized with propellant.  
         [0025]     A circumferential seal  46  is formed by the shoulder or rim portion of section  22   a  which contacts or abuts against the inner face of the bottom  14  or  34  of container  10  or  30 . As noted, when the fill valve is first installed in the un-pressurized container, it fits loosely in place. However, after the container is filled with a propellant, the internal container pressure forces section  22   a  of the fill valve tightly against the inner face of the container bottom. Seal  46  is now tightly pressed against this bottom wall surface of the container preventing leakage of propellant from the container.  
         [0026]     On the other end  22   c  of the fill valve, opposed grooves  48   a ,  48   b  are formed. The grooves extend longitudinally of section  22   c  and into central shaft section  22   b  of the fill valve. The grooves taper along the length of this section of the fill valve so that they terminate at the transition between this section and backend section  22   a  of the valve. Section  22   c  tapers outwardly from the outer end of the section to the abrupt transition between this portion of the fill valve and the section  22   b . A circumferential shoulder  50  is formed at the inner end of section  22   c  where the transition occurs. During a container fill operation, a nozzle (not shown) is pressed against the outer end of section  22   c  of the fill valve, forcing shoulder  50  against the outer face of the container bottom  14  or  34 . This action moves section  22   a  of the valve away from opening  20  or  40  in the container. The grooves  48   a ,  48   b  formed in the fill valve now allow flow of propellant through opening  20  or  40 , into the propellant chamber  24  or  44 . When the nozzle is removed, the internal pressure in the container forces shoulder  46  of the valve to seal opening  20  or  40  as previously discussed.  
         [0027]     The improved grommet or fill valve  22  of the present invention has a number of advantages of previous valves. One significant improvement is a better compression set from an increased cross-link density formed during the molding process and an improved elastomeric formulation. In the flashless injection molding process by which fill valves  22  are manufactured, the mold is maintained at a temperature necessary to cross-link the elastomer. The temperature of the elastomer injected into the mold to form the fill valves is at a temperature well above room temperature at the time of injection. In the fill valve of the present invention, the fact the mold and molding compound are heated to relatively high temperatures enhances the cross-linking process and substantially reduces the creation of leak paths. A particular advantage of the process by which the grommets are now made is that cryogenic deflashing of the fill valve is now unnecessary. Eliminating this manufacturing step prevents formation of cracks in the fill valve which could provide leakage paths for the propellant from the container in which the fill valve is installed  
         [0028]     As shown in  FIGS. 3A and 3B , an annular ring  52  is formed inwardly of the sidewall of section  22   a . Progressing further inwardly toward the center of the valve section, an annular raised section  54  is formed. Inwardly of section  54  is formed a section  56  which is stepped-down or recessed from section  54  by approximately 0.007″. The recessed section  54  provides a number of advantages to fill valve  22  over previous valves.  
         [0029]     First, it provides an area by which the elastomer injected into a mold cavity can be readily injected without the gate for the cavity getting in the way of the flow of compound into the cavity.  
         [0030]     Second, the recess reduces the amount of friction present during the feeding of the product on an assembly line.  
         [0031]     Third, the undercut reduces the amount of material required to make the fill valve and results in a valve which is more flexible than previous fill valves. This makes the valve easier to handle and also helps it provide a better seal when a container is pressurized with propellant.  
         [0032]     At the center of the section  54  is a depression or recess  58 . This recess is designed to receive the end of a tool (not shown) used to insert fill valve  22  in the opening  20  or  40  in an aerosol container during fabrication of the container. The valve is inserted by pushing against section  22   a  so to force the outer, smaller diameter end  22   c  of the fill valve through the opening.  
         [0033]     Finally, previous fill valves had raised characters formed on the section  54  of the backside of the valve. As previously noted, this often complicated movement of the fill valves on a conveyor or inserting them into a container. Now, as shown in  FIGS. 3A and 3B , the section  56  within annular ring  52  has pertinent information about the fill valve engraved on it. Specifically, this information identifies the mold and mold cavity in which the valve was formed. Such information is useful in analyzing productions problems which might occur so a mold or section of a mold which needs to be repaired or replaced is readily identified. Importantly, since this information is recorded in an out-of-the-way location but accessible location, this type of lettering is no longer required and the now “clean” surface of the backside of the fill valve makes it easier to handle the valve.  
         [0034]     In view of the above, it will be seen that the several objects and advantages of the present invention have been achieved and other advantageous results have been obtained.