CA1241908A - Multistage draping in vacuum skin packaging - Google Patents
Multistage draping in vacuum skin packagingInfo
- Publication number
- CA1241908A CA1241908A CA000434561A CA434561A CA1241908A CA 1241908 A CA1241908 A CA 1241908A CA 000434561 A CA000434561 A CA 000434561A CA 434561 A CA434561 A CA 434561A CA 1241908 A CA1241908 A CA 1241908A
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- Prior art keywords
- packaging
- closure
- article
- engaged
- members
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
- B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
- B65B11/00—Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material
- B65B11/50—Enclosing articles, or quantities of material, by disposing contents between two sheets, e.g. pocketed sheets, and securing their opposed free margins
- B65B11/52—Enclosing articles, or quantities of material, by disposing contents between two sheets, e.g. pocketed sheets, and securing their opposed free margins one sheet being rendered plastic, e.g. by heating, and forced by fluid pressure, e.g. vacuum, into engagement with the other sheet and contents, e.g. skin-, blister-, or bubble- packaging
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Vacuum Packaging (AREA)
Abstract
MULTISTAGE DRAPING IN VACUUM SKIN PACKAGING
ABSTRACT OF THE DISCLOSURE
An improvement is provided in a method for vacuum skin pack-aging. Vacuum skin packaging includes placing an article between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of the members, then vacuumizing the region between the closure and the engaged member to draw the engaged member against the closure, then vacuumizing the region between the packaging members, then releasing the first vacuumized condition to collapse the engaged member into conforming contact with the article, and then peripherally sealing together the packaging members about the article. The improvement provides for releasing the first vacuumized condition stage-wise across the closure, proceeding toward the periphery of the engaged packaging member, to move excess packaging material to the periphery of the final packaged configuration thereby diminishing any tendency toward wrinkling.
Associated apparatus is also provided.
ABSTRACT OF THE DISCLOSURE
An improvement is provided in a method for vacuum skin pack-aging. Vacuum skin packaging includes placing an article between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of the members, then vacuumizing the region between the closure and the engaged member to draw the engaged member against the closure, then vacuumizing the region between the packaging members, then releasing the first vacuumized condition to collapse the engaged member into conforming contact with the article, and then peripherally sealing together the packaging members about the article. The improvement provides for releasing the first vacuumized condition stage-wise across the closure, proceeding toward the periphery of the engaged packaging member, to move excess packaging material to the periphery of the final packaged configuration thereby diminishing any tendency toward wrinkling.
Associated apparatus is also provided.
Description
19~
, BACKGROUND OF THE INVENTION
This invention relates generally to vacuum skin packaging and more particularly to improvements in such packaging methods aimed at elimination of wrinkling of the packaging film in the final packaged configuration.
Vacuum skin packaging refers to a type of packaging wherein an article is enshrouded in thermoplastic packaging film such that the film lies in conforming contact with the packaged article. One basic approach to vacuum skin packaging is shown in U.S. Patent Re. 30,009 reissued May 29, 1979 to Perdue et al, which provides, in one representative mode, that a product is vacuum skin packaged between two impervious sheet members by first drawing by differential air pressure one of said sheet members which is1a heat softenable, formable plastic material against a concave surface i~la vacuum chamber which is shaped to partially enclose the product to be packaged; then while maintaining said differential air pressure heating said concave surface to at least the forming and soften-ing temperature of said sheet member; positioning said~product between said sheet members in said vacuum chamber; then evacuating the space between said sheet members while retaining by said differential air pressure said sheet member in contact with said heated concave surface;
then increasing the air pressure on the exterior of the retained sheet member to cause it to be released from contact with the concave surface thereby causing the retained sheet member to collapse around and into conforming contact with the product and against said other sheet member;
and then sealing said sheet members together about said product.
Generally, this approach is referred to as double chamber vacuum skin packaging.
~2:4~
-A variation of the foregoing method is shown in U.S. Patent 3,835,618 issued September 17, 1974 to Perdue being especially adapted for multipack vacuum skin packaging wherein a plurality of articles is packaged in a single operation. Another variation is shown in U.S.
Patent 3,950,919 issued April 20, 1976 to Perdue wherein an article is vacuum skin packaged between two flexible films. Another approach to vacuum skin packaging between two flexible films is shown in U.S. Patent 3,736,721 issued June 5, 1973 to Wolfelsperger wherein a single film is arranged around the article in a U shape and by differential pressure is formed over the article.
To varying extent, one problem encountered in vacuum skin pack-aging is wrinkling of the packaging film in the final packaged configura-tion. Various improvements have been suggested to minimize wrinkling in vacuum skin packaging, for example in U.S. Patent 3,956,867 issued May lD, 1976 to Utz et al wherein shrink film is utilized. Another approach islshown in U.S. Patent 3,686,822 issued August 29, 1972 to Wolfelsperger wherein the packaging film is stretched centrally in the vicinity of the article to be packaged and relative to its peripheral portions.
It is the aim of the present invention to minimize wrinkling in vacuum skin packaging of the type wherein one or more packaging members are shaped into one or more concavities, respectively, within a vacuum chamber as a step precedent to collapsing film into conforming contact with the article being packaged, such as in the methods disclosed in the above cited patents to Perdue.
, SUMMARY OF THE INVENTION
Essentially, the present invention provides a way to sequential-ly vent the vacuum chamber of a vacuum skin packaging apparatus in such a way as to cause excess packaging material to be transferred to the edge of the package where it can be later trimmed. The area near the center of the chamber is vented first, while the area near the edges is vented last. The delayed vacuum toward the outer portions peripherally holds the film and thereby supresses wrinkling in the central portions of the film as the film collapses over the product.
AccordinglyJ an improvement is provided in a method for vacuum skin packaging that includes placing an article between packaging members in a vacuum c;hamber having a concave closure that peripherally engages at least one of said members, then vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure, then vacuumizing the region between said packaging members, then releasing the first vacuumized condition to collapse said engaged member into conforming contact with said article, and then;peripherally sealing together said packaging members about said article, the improvement comprising releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of sald engaged packaging member, to move excess material of said member to the periphery of the final packaged configuration thereby diminishing any tendency toward wrinkling. Preferably, the method further includes selectively heating said closure to compensate for disproportionate thinning of the packaging material.
The apparatus of the invention provides for an improvement in vacuum skin packaging of the type wherein an article is initially placed 9~
between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of said members, including means for vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure; means for vacuumizing the region between said packaging members; means for releasing the first vacuumized condition to collapse said engaged member into conformity with said article; and means for peripherally sealing together said packaging members about said article, the improvement comprising means for releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of said engaged packaging member, to move excess material of said member to the periphery of the final packaged configura-tion to thereby diminish any tendency towards wrinkling. Preferably, the apparatus further includes meansifor selectively heating said closure to compensate for disproportionate thinning of the packaging material.
BRIEF DESCRIPTIiON OF THE DRAWINGS
Further details are given below with reference to the drawings wherein:
FIG. 1 is a schematic cross-section of an embodiment of the invention showing a beginning step;in a vacuum skin packaging operation wherein packaging film is vaccum drawn against a concave closure of a vacuum chamber;
FIG. 2 depicts an intermediate step, beyond the step of the previous figure, wherein excess packaging film is moved to the periphery by stagewise draping during collapse of the film onto the article being packaged; and ~;~4~
FIG. 3 depicts the final step in this sequence wherein the film is collapsed into conforming contact with the article being packaged while excess film material is accumulated at the periphery of the final packaged configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring specifically to the drawings, in FIG. 1, there is shown in schematic cross-section representative vacuum skin packaging apparatus modified in accordance with the invention which also depicts the beginning step in vacuum skin packaging operation. This basic type of apparatus is generally referred to as double chamber vacuum skin packaging apparatus. Vacuum skin packaging apparatus 10 has an upper closure 11 and a lower chamber 13. Closure 11 has inside surface 12 preferably being of a generally concave shape. Within chamber 13 is support platform 14 for supporting an article to be packaged. Concave closure 11 has a multiplicity of vacuum ports, shown representatively at 15, passing vertically through the closure and being in- communication with concave surface 12 and manifold regions above closure 11 as shown at 16 and 17a,b. The interior of chamber 13 is in communication with lower manifold region 18. Within chamber 13 during a typical packaging opera-tion there is an article 20 to be skin packaged resting on a lower pack-aging member 21 which in turn rests upon support platform 14. Above article 20 there is an upper packaging member 19. Packaging members 19 and 21 are typically sheets of flexible packaging material, preferably made from thermoplastics such as polyethylene, polypropylene, saran, nylon, polyvinyl chloride, and the like, and composite film structures of any of these materials. Preferably, the packaging members are substan-tial]y impermeable to gas transmission.
.. . .
iL9~)8 Turning now to the use of apparatus 10, initially closure 11 will be removed from chamber 13 thereby rendering its interior accessible.
Lower packaging member 21 is placed on support platform 14, and an article 20 to be packaged is placed on top of packaging member 21. Upper pack-aging member 19 is initially placed under closure 11 and is then drawn into concave surface 12 by vacuumizing the region between concave surface 12 and member 19. This first vacuumizing operation is done by drawing a vacuum through ports 15 which exhaust into manifold regions 16 and 17a,b which in turn are in communication with vacuum sources (not shown), respectively. The term "vacuumizing" is intended to refer to the opera-tion of partially evacuating a region to the desired extent. Thus, in vacuumizing the region between upper packaging member 19 and concave surface 12, the region is vacuumized at least to the extent that packaging member 19 i8 drawn into conforming contact with concave surface 12. It is preferred that closure 11 is heated, for example by a series of steam pipes representatively indicated at 22 passing through-the upper manifold regions, 80 that upon drawing a thermoplastic packaging.sheet into concave surface 12, the sheet is heated to its softening and forming.temperature.
Closure 11 is then lowered over chamber 13 thereby closing chamber 13 for further vacuumizing. Upper packaging member 19 is peripherally engaged by closure 11 upon seating closure 11 on lower chamber 13. The region between article 20 being packaged and upper packaging member 19 is then vacuumized by drawing a vacuum on manifold 18. This second vacuumizing step is sufficient to substantially evacuate the region around article 20, representatively a vacuum in excess of 20 inches of mercury, but less than the extent of vacuumizing carried out previously in shaping upper packmember 19, which representatively will be vacuumized to about 29 lnches of mercury, the object of this limitation being that upper member ,.
~2~19~3 19 be maintained in contact with closure 11 during the second vacuumizing step in the region around article 20. At this point in the operation the apparatus and the packaging elements are configured as shown in FIG. 1.
In FIG. 2, there is shown the next step in the vacuum skin packaging operation in accordance with the invention wherein upper pack-aging member 19 is draped over article 20. Draping is accomplished by releasing the first vacuumized condition stage-wise proceeding from an area over the article being packaged towards the peripheral areas of the concave inner surface 12 of closure 11. Specifically, the first stage in the release of the first vacuumized condition is accomplished by venting manifold 16 to the atmosphere. However, the vacuumized condition in manifold 17a,b is maintained so as to retain the outer portions of pack-aging member 19 in contact with the peripheral portions of concave surface 12. The purpose of this stage-wise draping is to accumulate excess packaging material toward the outside of the packaged configuration.
Optionslly, release of the vacuumized condition in manifold 16 may be accomplished by venting manifold 16 to a high pressure reservoir to it further enhance and smooth the draping motion of member 19 downward over article 20. A further optional feature of the invention provides for selectivity in the relative spans of manifolds 16 and 17a,b across closure 11. For example, as the span of manifold area 17a,b is increased and the span of manifold 16 is correspondingly decreased, the draping width will be decreased. Thus, selectivity is contemplated in determining optimum allocation between draping and peripheral retaining for any given pack-aging material and article configuration.
In FIG. 3 there is shown the final step in the vacuum skin packaging operation of the invention wherein upper packaging member 19 is collapsed into conforming contact with article 20. This collapsed con-19()~3 , figuration is accomplished by release of the vacuumized condition inouter manifolds 17a,b by, as discussed above, venting to atmospheric pressure The upper packaging member 19 is collapsed onto article 20 by the driving force of differential pressure, i.e. the region between packaging member 19 and concave closure 12 is at or above atmospheric pressure while the interior of vacuum chamber 13 is below atmospheric pressure. This stage-wise release of the first vacuumized condition above upper packaging member 19 tends to accumulate excess packaging material at the outside of the final packaged configuration as indicated at 25. Sealing between packaging members 19 and 21 as representatively indicated at location 26 is accomplished upon collapse of upper packaging member 19 onto article 20 and lower packaging member 21. This sealing can be accomplished in several different manners. For example, the confronting surfaces of the packaging members may be coated with adhesive which can be heat activatable. Thus, when the film is heated by contact with heated concave surface 12, the adhesive will be activated; and upon packaging member 19 collapsing about article 20 and into contact with lower packaging member 21, the adhesive will seal. For example when polyethylene packaging sheets are used, a coating of ethylene-vinyl acetate provides a satisfactory heat activatable adhesive. Another means of sealing is to coat the upper surface of lower packaging member 21 with a material being the same as the material of upper packaging member 19 such that when sufficiently heated the like materials will bond or seal together. Another method of sealing is to put a pressure sensitive adhesive or heat activatable adhesive on the upper surface of lower packaging member 21 and rely upon heat within the chamber to activate the adhesive. Finally, the periphery of the final package configuration is trimmed to remove excess packaging material that has accumulated toward the periphery of the upper packaging member 19.
~L2419(~
As a further optional feature of the invention, there is contemplated zone-wise heating of the concave closure when thermoplastic film is being used as the upper packaging member. Specificallyj zone-wise heating of the closure refers to differentially heating the closure such that the hottest zones correspond to those areas of the film least susceptible to thinning upon collapse onto the article being packaged, while the coldest zones correspond to those areas of the film most susceptible to thinning upon collapse onto the article. The term "thinning" refers to disproportionate thinning of the collapsed film in deeply drawn or highly deformed areas -of the -film in the collapsed configuration, e.g. near the upper corners of the article being packaged, most especially when the article is~high profile having a height of about
, BACKGROUND OF THE INVENTION
This invention relates generally to vacuum skin packaging and more particularly to improvements in such packaging methods aimed at elimination of wrinkling of the packaging film in the final packaged configuration.
Vacuum skin packaging refers to a type of packaging wherein an article is enshrouded in thermoplastic packaging film such that the film lies in conforming contact with the packaged article. One basic approach to vacuum skin packaging is shown in U.S. Patent Re. 30,009 reissued May 29, 1979 to Perdue et al, which provides, in one representative mode, that a product is vacuum skin packaged between two impervious sheet members by first drawing by differential air pressure one of said sheet members which is1a heat softenable, formable plastic material against a concave surface i~la vacuum chamber which is shaped to partially enclose the product to be packaged; then while maintaining said differential air pressure heating said concave surface to at least the forming and soften-ing temperature of said sheet member; positioning said~product between said sheet members in said vacuum chamber; then evacuating the space between said sheet members while retaining by said differential air pressure said sheet member in contact with said heated concave surface;
then increasing the air pressure on the exterior of the retained sheet member to cause it to be released from contact with the concave surface thereby causing the retained sheet member to collapse around and into conforming contact with the product and against said other sheet member;
and then sealing said sheet members together about said product.
Generally, this approach is referred to as double chamber vacuum skin packaging.
~2:4~
-A variation of the foregoing method is shown in U.S. Patent 3,835,618 issued September 17, 1974 to Perdue being especially adapted for multipack vacuum skin packaging wherein a plurality of articles is packaged in a single operation. Another variation is shown in U.S.
Patent 3,950,919 issued April 20, 1976 to Perdue wherein an article is vacuum skin packaged between two flexible films. Another approach to vacuum skin packaging between two flexible films is shown in U.S. Patent 3,736,721 issued June 5, 1973 to Wolfelsperger wherein a single film is arranged around the article in a U shape and by differential pressure is formed over the article.
To varying extent, one problem encountered in vacuum skin pack-aging is wrinkling of the packaging film in the final packaged configura-tion. Various improvements have been suggested to minimize wrinkling in vacuum skin packaging, for example in U.S. Patent 3,956,867 issued May lD, 1976 to Utz et al wherein shrink film is utilized. Another approach islshown in U.S. Patent 3,686,822 issued August 29, 1972 to Wolfelsperger wherein the packaging film is stretched centrally in the vicinity of the article to be packaged and relative to its peripheral portions.
It is the aim of the present invention to minimize wrinkling in vacuum skin packaging of the type wherein one or more packaging members are shaped into one or more concavities, respectively, within a vacuum chamber as a step precedent to collapsing film into conforming contact with the article being packaged, such as in the methods disclosed in the above cited patents to Perdue.
, SUMMARY OF THE INVENTION
Essentially, the present invention provides a way to sequential-ly vent the vacuum chamber of a vacuum skin packaging apparatus in such a way as to cause excess packaging material to be transferred to the edge of the package where it can be later trimmed. The area near the center of the chamber is vented first, while the area near the edges is vented last. The delayed vacuum toward the outer portions peripherally holds the film and thereby supresses wrinkling in the central portions of the film as the film collapses over the product.
AccordinglyJ an improvement is provided in a method for vacuum skin packaging that includes placing an article between packaging members in a vacuum c;hamber having a concave closure that peripherally engages at least one of said members, then vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure, then vacuumizing the region between said packaging members, then releasing the first vacuumized condition to collapse said engaged member into conforming contact with said article, and then;peripherally sealing together said packaging members about said article, the improvement comprising releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of sald engaged packaging member, to move excess material of said member to the periphery of the final packaged configuration thereby diminishing any tendency toward wrinkling. Preferably, the method further includes selectively heating said closure to compensate for disproportionate thinning of the packaging material.
The apparatus of the invention provides for an improvement in vacuum skin packaging of the type wherein an article is initially placed 9~
between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of said members, including means for vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure; means for vacuumizing the region between said packaging members; means for releasing the first vacuumized condition to collapse said engaged member into conformity with said article; and means for peripherally sealing together said packaging members about said article, the improvement comprising means for releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of said engaged packaging member, to move excess material of said member to the periphery of the final packaged configura-tion to thereby diminish any tendency towards wrinkling. Preferably, the apparatus further includes meansifor selectively heating said closure to compensate for disproportionate thinning of the packaging material.
BRIEF DESCRIPTIiON OF THE DRAWINGS
Further details are given below with reference to the drawings wherein:
FIG. 1 is a schematic cross-section of an embodiment of the invention showing a beginning step;in a vacuum skin packaging operation wherein packaging film is vaccum drawn against a concave closure of a vacuum chamber;
FIG. 2 depicts an intermediate step, beyond the step of the previous figure, wherein excess packaging film is moved to the periphery by stagewise draping during collapse of the film onto the article being packaged; and ~;~4~
FIG. 3 depicts the final step in this sequence wherein the film is collapsed into conforming contact with the article being packaged while excess film material is accumulated at the periphery of the final packaged configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring specifically to the drawings, in FIG. 1, there is shown in schematic cross-section representative vacuum skin packaging apparatus modified in accordance with the invention which also depicts the beginning step in vacuum skin packaging operation. This basic type of apparatus is generally referred to as double chamber vacuum skin packaging apparatus. Vacuum skin packaging apparatus 10 has an upper closure 11 and a lower chamber 13. Closure 11 has inside surface 12 preferably being of a generally concave shape. Within chamber 13 is support platform 14 for supporting an article to be packaged. Concave closure 11 has a multiplicity of vacuum ports, shown representatively at 15, passing vertically through the closure and being in- communication with concave surface 12 and manifold regions above closure 11 as shown at 16 and 17a,b. The interior of chamber 13 is in communication with lower manifold region 18. Within chamber 13 during a typical packaging opera-tion there is an article 20 to be skin packaged resting on a lower pack-aging member 21 which in turn rests upon support platform 14. Above article 20 there is an upper packaging member 19. Packaging members 19 and 21 are typically sheets of flexible packaging material, preferably made from thermoplastics such as polyethylene, polypropylene, saran, nylon, polyvinyl chloride, and the like, and composite film structures of any of these materials. Preferably, the packaging members are substan-tial]y impermeable to gas transmission.
.. . .
iL9~)8 Turning now to the use of apparatus 10, initially closure 11 will be removed from chamber 13 thereby rendering its interior accessible.
Lower packaging member 21 is placed on support platform 14, and an article 20 to be packaged is placed on top of packaging member 21. Upper pack-aging member 19 is initially placed under closure 11 and is then drawn into concave surface 12 by vacuumizing the region between concave surface 12 and member 19. This first vacuumizing operation is done by drawing a vacuum through ports 15 which exhaust into manifold regions 16 and 17a,b which in turn are in communication with vacuum sources (not shown), respectively. The term "vacuumizing" is intended to refer to the opera-tion of partially evacuating a region to the desired extent. Thus, in vacuumizing the region between upper packaging member 19 and concave surface 12, the region is vacuumized at least to the extent that packaging member 19 i8 drawn into conforming contact with concave surface 12. It is preferred that closure 11 is heated, for example by a series of steam pipes representatively indicated at 22 passing through-the upper manifold regions, 80 that upon drawing a thermoplastic packaging.sheet into concave surface 12, the sheet is heated to its softening and forming.temperature.
Closure 11 is then lowered over chamber 13 thereby closing chamber 13 for further vacuumizing. Upper packaging member 19 is peripherally engaged by closure 11 upon seating closure 11 on lower chamber 13. The region between article 20 being packaged and upper packaging member 19 is then vacuumized by drawing a vacuum on manifold 18. This second vacuumizing step is sufficient to substantially evacuate the region around article 20, representatively a vacuum in excess of 20 inches of mercury, but less than the extent of vacuumizing carried out previously in shaping upper packmember 19, which representatively will be vacuumized to about 29 lnches of mercury, the object of this limitation being that upper member ,.
~2~19~3 19 be maintained in contact with closure 11 during the second vacuumizing step in the region around article 20. At this point in the operation the apparatus and the packaging elements are configured as shown in FIG. 1.
In FIG. 2, there is shown the next step in the vacuum skin packaging operation in accordance with the invention wherein upper pack-aging member 19 is draped over article 20. Draping is accomplished by releasing the first vacuumized condition stage-wise proceeding from an area over the article being packaged towards the peripheral areas of the concave inner surface 12 of closure 11. Specifically, the first stage in the release of the first vacuumized condition is accomplished by venting manifold 16 to the atmosphere. However, the vacuumized condition in manifold 17a,b is maintained so as to retain the outer portions of pack-aging member 19 in contact with the peripheral portions of concave surface 12. The purpose of this stage-wise draping is to accumulate excess packaging material toward the outside of the packaged configuration.
Optionslly, release of the vacuumized condition in manifold 16 may be accomplished by venting manifold 16 to a high pressure reservoir to it further enhance and smooth the draping motion of member 19 downward over article 20. A further optional feature of the invention provides for selectivity in the relative spans of manifolds 16 and 17a,b across closure 11. For example, as the span of manifold area 17a,b is increased and the span of manifold 16 is correspondingly decreased, the draping width will be decreased. Thus, selectivity is contemplated in determining optimum allocation between draping and peripheral retaining for any given pack-aging material and article configuration.
In FIG. 3 there is shown the final step in the vacuum skin packaging operation of the invention wherein upper packaging member 19 is collapsed into conforming contact with article 20. This collapsed con-19()~3 , figuration is accomplished by release of the vacuumized condition inouter manifolds 17a,b by, as discussed above, venting to atmospheric pressure The upper packaging member 19 is collapsed onto article 20 by the driving force of differential pressure, i.e. the region between packaging member 19 and concave closure 12 is at or above atmospheric pressure while the interior of vacuum chamber 13 is below atmospheric pressure. This stage-wise release of the first vacuumized condition above upper packaging member 19 tends to accumulate excess packaging material at the outside of the final packaged configuration as indicated at 25. Sealing between packaging members 19 and 21 as representatively indicated at location 26 is accomplished upon collapse of upper packaging member 19 onto article 20 and lower packaging member 21. This sealing can be accomplished in several different manners. For example, the confronting surfaces of the packaging members may be coated with adhesive which can be heat activatable. Thus, when the film is heated by contact with heated concave surface 12, the adhesive will be activated; and upon packaging member 19 collapsing about article 20 and into contact with lower packaging member 21, the adhesive will seal. For example when polyethylene packaging sheets are used, a coating of ethylene-vinyl acetate provides a satisfactory heat activatable adhesive. Another means of sealing is to coat the upper surface of lower packaging member 21 with a material being the same as the material of upper packaging member 19 such that when sufficiently heated the like materials will bond or seal together. Another method of sealing is to put a pressure sensitive adhesive or heat activatable adhesive on the upper surface of lower packaging member 21 and rely upon heat within the chamber to activate the adhesive. Finally, the periphery of the final package configuration is trimmed to remove excess packaging material that has accumulated toward the periphery of the upper packaging member 19.
~L2419(~
As a further optional feature of the invention, there is contemplated zone-wise heating of the concave closure when thermoplastic film is being used as the upper packaging member. Specificallyj zone-wise heating of the closure refers to differentially heating the closure such that the hottest zones correspond to those areas of the film least susceptible to thinning upon collapse onto the article being packaged, while the coldest zones correspond to those areas of the film most susceptible to thinning upon collapse onto the article. The term "thinning" refers to disproportionate thinning of the collapsed film in deeply drawn or highly deformed areas -of the -film in the collapsed configuration, e.g. near the upper corners of the article being packaged, most especially when the article is~high profile having a height of about
2 inches or greater. Typically, the area of the film least susceptible to thinning will be on top of the article being packaging. Such zone-wise heating of the closure can be accomplished by selectively varying the heat rate among steam pipes 22 in the upper- manifold regions.
Alternatively, such-zone-wise heating may be accomplished by venting vacuum ports 15 with heated air, the extent of heating being varied selectively among vents 15. The zone-wise heating is accomplished before or during draping of the film, the draped configuration being indicated in FIG. 2.
The foregoing discussion has focused on application of the present invention to the method and apparatus disclosed in ~.S. Patent Re 30,009 cited above; however, the generality of the present invention is to be emphasized. For examplej the present invention can be similarly applied in the method and apparatus disclosed in U.S. Patent 3,835,618, cited above, being directed to double chamber vacuum skin packaging of a plurality of articles referred to as a multipack. Likew1se, the present i ~L24~9~)8 - invention can be applied similiarly in the single chamber vacuum skin packaging apparatus disclosed in U.S. Patent 3,950,919 cited above, being -I directed to double web vacuum skin packaging utilizing a vacuum chamber ; having upper and lower concave closures. Further, the present invention ._ -I may be applied in vacuum chambers of the type disclosed in U.S. Patent
Alternatively, such-zone-wise heating may be accomplished by venting vacuum ports 15 with heated air, the extent of heating being varied selectively among vents 15. The zone-wise heating is accomplished before or during draping of the film, the draped configuration being indicated in FIG. 2.
The foregoing discussion has focused on application of the present invention to the method and apparatus disclosed in ~.S. Patent Re 30,009 cited above; however, the generality of the present invention is to be emphasized. For examplej the present invention can be similarly applied in the method and apparatus disclosed in U.S. Patent 3,835,618, cited above, being directed to double chamber vacuum skin packaging of a plurality of articles referred to as a multipack. Likew1se, the present i ~L24~9~)8 - invention can be applied similiarly in the single chamber vacuum skin packaging apparatus disclosed in U.S. Patent 3,950,919 cited above, being -I directed to double web vacuum skin packaging utilizing a vacuum chamber ; having upper and lower concave closures. Further, the present invention ._ -I may be applied in vacuum chambers of the type disclosed in U.S. Patent
3,736,721 cited above, directed to vacuum skin packaging using a single web of film folded in a U-configuration about the article to be packaged.
.
i In the foregoing discussion, attention was directed to two -I stage draping of the upper packaging member over the article being pack-aged; however, the number of stages utilized in the release of the first vacuumized condition is a process variable that may be optimized by the user as desired for a particular packaging configuration. For example, in the multipack situation wherein two or more articles are simultaneously 3 vacuum skin packaged, three-stage release of the first vacuumized condi--I tion may advantageously be utilized wherein during stage-one release - packaging film is draped over each of the articles being packaged-in the multipack while maintaining the pinned or retained position of the film ., I- against the closure in those areas between-the articles of the multipack, and in stage-two this intermediate retained position is released to collapse the-packaging film in the intermediate areas between the articles .
. in the multipack, and in stage-three the peripherally retained portion of the packaging film is finally released as discussed above.
Although the present invention has been described in conjunc-, i. ,, tion with preferred embodiments it is to be understood that modifications _ and variations may be utilized without departing from the principles and j scope of the invention, as those skilled in the art will readily under-.~ .
. stand. Accordingly such modifications and variations may be practiced j within the scope of the following claims:
/~
.
i In the foregoing discussion, attention was directed to two -I stage draping of the upper packaging member over the article being pack-aged; however, the number of stages utilized in the release of the first vacuumized condition is a process variable that may be optimized by the user as desired for a particular packaging configuration. For example, in the multipack situation wherein two or more articles are simultaneously 3 vacuum skin packaged, three-stage release of the first vacuumized condi--I tion may advantageously be utilized wherein during stage-one release - packaging film is draped over each of the articles being packaged-in the multipack while maintaining the pinned or retained position of the film ., I- against the closure in those areas between-the articles of the multipack, and in stage-two this intermediate retained position is released to collapse the-packaging film in the intermediate areas between the articles .
. in the multipack, and in stage-three the peripherally retained portion of the packaging film is finally released as discussed above.
Although the present invention has been described in conjunc-, i. ,, tion with preferred embodiments it is to be understood that modifications _ and variations may be utilized without departing from the principles and j scope of the invention, as those skilled in the art will readily under-.~ .
. stand. Accordingly such modifications and variations may be practiced j within the scope of the following claims:
/~
Claims (8)
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS: -
1. In a method for vacuum skin packaging, including placing an article between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of said members; then vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure; then vacuumizing the region between said packaging members; then releasing the first vacuumized condition to collapse said engaged member into conforming contact with said article; and then peripherally sealing together said packaging members about said article, the improvement comprising releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of said engaged packaging member, to move excess material of said member to the periphery of the final packaged configura-tion thereby diminishing any tendency toward wrinkling.
2. The method of claim 1 further comprising providing for said packaging members thermoplastic film sheets which are substantially impermeable and differentially heating said-closure zone-wise such that the hotest zones correspond to those areas of said engaged film least susceptible to thinning upon collapse onto said article.
3. The method of claim 1 further provided that said engaged packaging member is maintained in contact with said closure while the region between said packaging members is vacuumized and said first vacuumized condition is released by venting to a high pressure source.
4. The method of claim 1 further comprising packaging a plurality of articles simultaneously further provided that said first vacuumized condition is released in three stages with an intermediate stage to restrain draping in the areas between said plurality of articles.
5. In an apparatus for vacuum skin packaging wherein an article is initially placed between packaging members in a vacuum chamber having a concave closure that peripherally engages at least one of said members, including means for vacuumizing the region between said closure and said engaged member to draw said engaged member against said closure;
means for vacuumizing the region between said packaging members; means for releasing the first vacuumized condition to collapse said engaged member into conformity with said article; and means for peripherally sealing together said packaging members about said article, the improve-ment comprising means for releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of said engaged packaging member, to move excess material of said member to the periphery of the final packaged configuration to thereby diminish any tendency towards wrinkling.
means for vacuumizing the region between said packaging members; means for releasing the first vacuumized condition to collapse said engaged member into conformity with said article; and means for peripherally sealing together said packaging members about said article, the improve-ment comprising means for releasing said first vacuumized condition stage-wise across said closure, proceeding toward the periphery of said engaged packaging member, to move excess material of said member to the periphery of the final packaged configuration to thereby diminish any tendency towards wrinkling.
6. The apparatus of claim 5 further comprising means for differentially heating said closure zone-wise such that the hotest zones correspond to those areas of said engaged film least susceptible to thin-ning upon collapse onto said article.
7. The apparatus of claim 5 further comprising means for maintaining said engaged member in contact with said closure while the region between said packaging members is vacuumized and means for releas-ing said first vacuumized condition by venting to a high pressure source.
8. The apparatus of claim 5 further comprising means for releasing said first vacuumized condition in three stages with an inter-mediate stage for restraining draping in the areas between a plurality of articles being packaged simultaneously.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44379682A | 1982-11-22 | 1982-11-22 | |
| US443,796 | 1982-11-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1241908A true CA1241908A (en) | 1988-09-13 |
Family
ID=23762240
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000434561A Expired CA1241908A (en) | 1982-11-22 | 1983-08-15 | Multistage draping in vacuum skin packaging |
Country Status (3)
| Country | Link |
|---|---|
| CA (1) | CA1241908A (en) |
| DE (1) | DE3342171A1 (en) |
| GB (1) | GB2130543A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2271546A (en) * | 1992-10-19 | 1994-04-20 | Grace W R & Co | Vacuum packaging chamber and method |
| DE102014114660A1 (en) * | 2014-10-09 | 2016-04-14 | Medipack Ag | Method for packaging articles in blister packs |
| DE102022110134A1 (en) | 2022-04-27 | 2023-11-02 | Multivac Sepp Haggenmüller Se & Co. Kg | METHOD FOR PACKAGING PRODUCTS AND CLOSING STATION FOR PACKAGING |
| WO2024074541A1 (en) * | 2022-10-04 | 2024-04-11 | Gea Food Solutions Germany Gmbh | Sealing tool for a skin packaging |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3950919A (en) * | 1974-08-22 | 1976-04-20 | W. R. Grace & Co. | Apparatus and process for vacuum skin packaging |
-
1983
- 1983-08-15 CA CA000434561A patent/CA1241908A/en not_active Expired
- 1983-09-05 GB GB08323729A patent/GB2130543A/en not_active Withdrawn
- 1983-11-19 DE DE19833342171 patent/DE3342171A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB8323729D0 (en) | 1983-10-05 |
| GB2130543A (en) | 1984-06-06 |
| DE3342171A1 (en) | 1984-05-24 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |