CA1259024A

CA1259024A - Device to reduce or avoid webbing in vsp process

Info

Publication number: CA1259024A
Application number: CA000417056A
Authority: CA
Inventors: Ermanno Bortolani; Sandro Brembilla; Enzo Vassarotti
Original assignee: WR Grace and Co
Current assignee: Cryovac LLC
Priority date: 1982-04-30
Filing date: 1982-12-06
Publication date: 1989-09-05
Also published as: DK15283A; IT1151393B; EP0093480A2; DK157742C; DK157742B; JPS58193225A; IT8221030A0; AU561552B2; EP0093480A3; DK15283D0; BR8302137A; EP0093480B1; AU1409583A; DE3362974D1

Abstract

ABSTRACT
"IMPROVEMENTS IN OR RELATING TO VACUUM PACKAGING"

The invention provides a method of vacuum packing by defining a "dummy product" 17 alongside a product article 14 on a support sheet so that any "webbing"
18 is to the side of that projection 17 which faces away from the adjacent product article 14. That projection 17 can subsequently be trimmed to leave a webbing-free pack.
Cutting down webbing reduces the risk of leakage of the pack. Preferably the height of the projection 17 is adjusted in response to the height of a product article 14 so that the extent of such webbing 18 is at a minimum.

Description

~25go~4 DESCRIPTION
" I~l'R~ NTS IN OR REI~TING TO VACUllM PACKAGING"

The present invention provides an improved method and apparatus for producing a vacuum package, and in particular so as to avoid or reduce the incidence of "webbing" around tall products packa~ed on a relatively flat support.
`` It is a well known problem that when packaging relatively tall products by placing them on a support board on which a cover sheet is draped while in a heat- -softened condition, the cover sheet attaches itself to the support board, as desired, but leaves unsightly .
"webbing" where folds arise in the cover sheet around the edges of the product. This webbing is particularly undesirable because it gives rise to leakages in the ~inished pac~age.

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.~ ' , ~ ~59024 ~ le now propose to provide a vacuum package comprising at least one product article on a support, substantially without any wrinkles or webbing around the product in the finished packa~e.
~ ccordingly, the present invention provides a process for vacuum packaging, comprising placing at least one product article on a support sheet and coverlny that product article with a heat softened cover film and sealing it on the support sheet with the application of vacuum arouncl the product article or articles and between the support sheet and cover film~
characterised by the step of providing an upstandiny or recess formation on the side of the support sheet to which the cover film is attached during the closing operation, such formation serving as a cover film "collector" to absorb material of the cover film which would otherwise form webbing on the adjacen~ artlcle.
The "collector" formation alongside the product article or array of product articles may comprise a thermoformed upstanding rib in the support sheet, or a filler strip laid on the support sheet, or an ups~anding marginal rib in the ~ase of a rigid support sheet, or a recess in the support sheet due to local downward deformation. Other ways of achieving the collector formation are well within the capability of the e~pert in this field.
Finally, the invention provides apparatus for vacuum paclcaging, comprising: a vacuum chamber adapted to receive a support sheet and a cover film over the support sheet; and means for evacuating a space between the cover film and support sheet to form a vacuum pack of the cover film sealed to the support sheet around a product article; characterised by means defining an B

upstandiny formation or a recess formation in the cover film to define a cover film "collector" in the finlshed pack to absorb cover film material which would otherwise form webbing on a said product article being packed.
In oLcler that the present invention may more readily be understood the following description is given, merely by way of example, of one embodiment of a method in accordance with the present invention, in which an array of four product articles is packed simultaneously across a web. This embodiment is described with reference to the accompanying drawings in which:-Figure 1 is a top plan view of a prior art packageshowing "webbing" formed at the corners of the rectangular array of four rectangular parallelepiped-shaped product articles;
Figure 2 is a section taken on the line 2-2 of Figure 1;
Figure 3 is a top plan view of a similar package but when formed by the method in accordancè with the present invention;
Figure 4 is a schematic sectional view showing the vacuum chamber closed around the product articles æ ' ~.J ~
~59~:~4 and films during the formation of the package of Figure 3;
Figure 5 is an overhead perspective view sh~wing the base portion of the chamber illustrated in Figure 4, Fi~ure 6 is a detail, on the same section plane as Figure 4, but showing a depressed"cover film collector"
formation.
Referring now to the drawings, Figure 1 shows the package as comprising a support sheet 10 on which are placed product articles 11,12,13,14 which are then `I
covered by a cover film 15.
At the four corners of the rectangular array of product articles are "webbing"formations 16, one of which is shown in sectional view in Figure 2.
We have now discovered that if a co~er film "collector" formation such as a ~'dummy product"-like formation is arranged alongside an article such as 11, 12, 13-or ï4 any "webbing" is formed around that "dummy product" rather than on the nearest adjacent article of the array. Thus, Figure 3 shows an upstanding rib 17 which, in accordance with one form of the present invention, is positioned alongside the array of product articles. In this case there are two such "dummies" 17, one at each end of the array of product articles and (by careful choice of heights of these "dummies") each attracting a much smaller "webbing"
formation 18 extending in a direction towards the adjacent edge of the support sheet 10, and therefore : away`from the adjacent product article 11 or 14.

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j~.^, ~2sgo~4 In this particular embodiment there are four product articles each of rectangular parallelepiped-shape, and arranged in a rectangular array with the two "dummy products" extending parallel to the shorter sides of that array. However, any other configuration is possible provided the "dummy products" formed in accordance with the present invention are positioned relative to an adjacent product article (which may ~e the only product article on the support base) such as to avoid the formation of "webbing" with that article.
Figure 4 shows the formation of such a package by placing a cover 19, having a downwardly concave cavity to define a vacuum chamber above t~e cover film 15, a base-20 co-operating with cover 19.
In this particular embodiment the "dummy products" are in the form of upstanding ribs formed in the support sheet 10 by liftable plates 21 each of which is actuated by a respective fluid pressure-operated ram (either pneumatic or hy~raulic) 22 only one of which is shown in Figure 4.
Figure ~ shows an overhead perspective view of the base 20 of Figure 4, including the two "dummy product"-aefining plates 21 but, for the purpose of simplicity of illustration, the operating rams 22 have b2en omitted from this drawing.
The operation of the apparatus of Figures 4 i .

~2S9024 and 5, and of the process exemplified by Figures 3, 4 and 5 is as follows:-A continuous support sheet 10 is advancedover the base 20 in a direction parallel to the extent ~E the two "dummy product"- defining plates 21 to index a fresh portion of the support sheet, with an array of four product articles 11, 12, 13 and 14 thereon, on the base 20, ready to be sealed by the vertical reciprocable cover 19.
In this particular embodiment of the process, the "dummy product"-defining plates 21 are able to be retracted into the base 20 so that the support sheet 10 can be substantially flat as it is moved into position on the base 20. ~nce the cover film 15 has arrived under the cham~er cover 19, the cover 19 descends and the vacuum chamber space defined in the clearance between the cover 19 and the base 20 is evacuated in such a sequence as to draw the cover film 15 down onto the support sheet 10. At this time, or slightly earlier but after closing of the cover 19 onto the base 20, the rams 22 are operated to raise the "dummy product"-defining plates ~1 to a position shown in Figure 4 where they deform the now clamped support sheet 10, and the cover f~lm 15 thereon, upwardly to define the illustrated "dummy product" ribs 17.
Although not mentioned above, it will of ' ~ 1259~124 course be understood that the cover film 15 is heated before this vacuum draping operation in which it is draped onto the support sheet 10~ The heating can be either by means of radiant heaters positioned in the . path of the cover film 15 towards the sealing station defined by the chamber cover 19 and the base 20~ or alternatively some heating means ma~r be incorporatea in the cham~er cover 19 and the cover film 15 may be attracted into contact with the hot cavity within the .
cover 19 by a pressure differential. The latter system `~
will be su~stantially as disclosed in U.S. Patent No. 3,6941991 (Perdue et al). Alternative processes may be substantially as disclosed in U.S. Patent No. 3,~91,504 (Young et al), U.S. Patent No. 3,634,993 (Pasco and - Wolfelsp~rger)~ ~.K. Patent No. 1~445~285 (Du Pont)~
U. S. Patent No. 3,260,032 (Hill et al) or in Modern Pac~aging (May 1971) at pages 60 to 62.
Figure 4 shows one form of means for opening and closing the chamber 19~ 20, namely a fluia pressure-operated jack 23 progræmmed to op~rate in a repetitivecycle coordinated with operation of the feed means 25 for ~he support sheet 10 and the cover lilm 15 so that the film-advancing movement occurs while the chamber is open~ and the film advance is interrupted as the chamber closes. A suiLable vacuum source is connected to the duct 2~ for evacuating the space between the support sheet 10 and the cover film 15, the evacuation operation being coordinated~ by m_an5 of a central programmer, ':

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with the operation of the chamber-opening and-closing means in a programme which is well known to the expert in this art.
Although the above.descripti.on relates to the simultaneous packaging of a set of articles 11, 12, 13, and 14 in a rectangular array extending laterally across a continuous web, any convenient number of such articles, even including only one article, may be packaged during each operating phase of the vacuum chamber 19, 20 defining the sealing station.
Upon completion of the sealing operation, the package will have the configuration shown in Figure 4 in that the raised "dummy product"-defining ribs 17 will ...... remain in the support sheet 10 and the "webbing" 18 (not shown in Figure 4) will then extend outwardly towards the margin of the support sheet 10. To enhance this operation, the support sheet 10 may itself be heated so as..to undergo a degree of thermoforming in the deformation process.
~he cham~er cover 19 is then ralsed, and the composite.sheet 10-15 is advanced to a trimming station where the lateral margins of~the composite sheet 10, 15, including the remaining "dummy product"-defining ribs 17, are trimmed off and the pac~age shown in

2~ Figure 3 is severed from a continuous strip of such pac~ages having a succession of such rectangular arrays ` ~J
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of product articles 11-14 thereon- Optionally, the individual product articles 11, 12, 13 and 14 in each array may then be severed from one another to provide ~our separate vacuum packages.
It has been found that the process described above considerably reduces the formation of "webbing" and bearing in mind that the webbing is then formed in the selvage at the edge of the composite web the wrinkles can be completely eliminated from the finished package by trimming. Thus the aesthetic appeal of the finished package is much better than with the prior art pack where more substantial corner "webbing" 16 is noticeable.
A rather more important advantage of the present process is that, by appropriate selection of the height of the "dummy product"-defining ribs 17, it is ; possible to reduce the magnitude of the "webbing" 18 to such an extent that there will no longer be a risk of lea~age of thP ~inished pack. In any case, bearing in mind that the "webbing" 18 is now fol~ed at the "dummy product"-defining ribs 17 away from the corners of the - array ~f product articles 11-14, th~is array itself is substantially free of "webbing". It is, after all, vacuum on the product articles themselves which is being ; aimed for and thus it is the occurrence of "~ebbing" at those corners which could aive rise to unacceptable lea~age; this has been avoiaed by the pr~cess of the .
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_ 10-present invention.
As indicated above, ~he height of the "dummy pr~duct"-defining ribs 17 is preferably adjustable and conseguently the raised position of each of the plates 21 is preferably itself adjustable by means such as the rams 22 shown in Figure 4~ so as to allow optimisation of the height of the ribs 17 in dependence on the heights of the individual product articles 11-14.
If desired the plates 21 may be normally fixed in use of the apparatus but adjustable in height to allow for different heights of product. Likewise the height of the cavity in the underside of the cover 19 ma~ be adjustable as disclosed in U~S. Patent ~o. 3835618 _ As will be appreciated, the apparatus 1~ illustrated in Figure 4 is particularly advantageous in that it does not require the presence of partition walls .

between the individual product articles and consequently the same chamber con~iguration can be used for various different layouts of product articles on the support sheet 10.
An alternative embodiment of the process is one in which the plates 21 2re no longer required but, insteaa, "dummy products" in the form of filler strips are laid on the support sheet 10 in the selvage region ~$ 2~ where the ribs 17 arise in ~igures 3 and 4 These "dummy products" are preferably disposable items so lZ5~024 that they can be discarded with the trimmed selvage at the subsequent trimming station.
A further possibility, particularly suitable in the case of packaging using relatively stiff backing b~ards, such as an expanded polystyrene tray coated with an air-impervious surface film to facilitate vacuum ., packaging, is one in which the lateral edges ~f a generally flat horizontal tray extend upwardly to define "dummy product" formations which will attract the .
"webbing" and can then be trimmed off as with the emb~diment of package shown in Figure 4.
It is not essential for the various product articles 11, 12, 13 and 14 to be severed from one another.
; lt would instead be p~ssible to packag~simultaneously four separate product articles which will be sold in a "consume s~me-save some" pack enabling the consumer to cut open each of the four product-containing "bubbles"
separately. The display of such a pac~ may even be effected with tne aid of one or b~th of the "dummy product"
formations left on the pac~ to enable the pac~ to be suspendedj for example by placing it on-two closely adjacent rails which pass between a "dummy product"
formation 17 and the nearest product article 11 or 14.
This is applicable in the case of relatively stiff support sheets 10 in which the "dummy product" formation will be sufIiciently rigid to supp3rt ~he weight of the : ' ~ ~ 1;2S90;24 pac~. , Otherwise, suspension display of the individual product articles 11, 12, 13 and 14 can be achieved by punching a suspension display hole (not shown) in the peripheral zone of the pac~ containing such an individual product article, the punching operation taking place . simultaneously with the operation of severing the articles one from another.
Any sui-table medium may be used for the support sheet, ranging frcm a single or multi-layer film preferably having a heat-sealzble upper surface, to a rigid or semi-rigid material, for example the above-mentioned expanded pDlystyrene board having a coating on its uppex -surface to hold vacuum and, preferably, to render it heat-sealable. Instead of heat sealing, self-welding may be employed as the sealing mechanism, or an adhesive action may be used. Similarly, the cover film 15 may be of single layer or multi-layer construction, preferably having a heat-sealable layer coming into c~ntact with the support sheet to facilitate sealing. Such single layer or-multi-layer ~ilms of self-welding or heat-sealable type are well ~nown in the art.
- Fig 6 shows an alternative embodiment in which the coverfilm "collector" fo_~tion is deIined not by a 2~ "dummy product" but in5tead by a local down~a~dly deformed region or recess formation 17~ in the ~upp~rt sneet ~ ,~3 ~2sso2~

Upon vacuum sealing, surplus cover film of the sheet 15 (around the adjacent product article 14) is absorbed in the recess on the upper concave face of depressed formation 17a and webbing at the product article 14 is considerably reduced and even substantially eliminated.
Generally the recess type of "collector"
. formation defines an aperture of adequate size in the supp~rt sheet and may simply be a hole in the support sheet.
The process for forming the pack shown in Figure 6 will be analDgous to the process employing upstanding "dummy pack"~ormations and the "collector"
. recess or aperture may be preformed or formed in situ in .-.the-chamber. The design of suitable apparatus for 1~ achieving this is well within the capability of the expert in this art.
As will be readily appreciated, the description given above..is merely by way of example and is capable of being varied to a wide degree by the expert s~illed in this art, while remaining within the scope of the foll~wing claims.. .

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for vacuum packaging, comprising placing at least one product article on a support sheet and covering that product article with a heat softened cover film and sealing it on the support sheet with the application of vacuum around the product article or articles and between the support sheet and cover film, characterised by the step of providing an upstanding or recess formation on the side of the support sheet to which the cover film is attached during the closing operation, such formation serving as a cover film "collector" to absorb material of the cover film which would otherwise form webbing on the adjacent article.

2. A process according to claim 1, characterised in that said "collector" formation is formed by an upwardly deformed region of the support sheet.

3. A process according to claim 1, characterised in that said "collector" formation is formed by a filler between the support sheet and the cover film.

4. A process according to claim 1, characterised in that the "collector" formation is formed by a marginal rim of the support sheet.

5. A process according to claim 1 characterised in that said "collector" formation is formed by a downwardly deformed region of the support sheet.

6. A process according to claim 1, 2 or 3, and further characterised by the step of trimming the said "collector"
formation from the sealed pack.

7. A process according to claim 1, 2 or 3, characterised in that the packaging is carried out on a continuous cycle in which the support sheet and the cover film are advanced to a sealing station with a plurality of product articles on the support sheet;
and, after sealing, the product articles which are packed simultaneously at the sealing station are trimmed from the continuous composite web comprising the support sheet and cover film.

8. Apparatus for vacuum packaging, comprising: a vacuum chamber adapted to receive a support sheet and a cover film over the support sheet; and means for evacuating a space between the cover film and support sheet to form a vacuum pack of the cover film sealed to the support sheet around a product article;
characterised by means defining an upstanding formation or a recess formation in the cover film to define a cover film "collector" in the finished pack to absorb cover film material which would otherwise form webbing on a said product article being packed.

9. Apparatus according to claim 8, characterised in that said means defining an upstanding or recess formation include an adjustable rib projecting into the chamber.

10. Apparatus according to claim 9, and further characterised by including means for retracting said rib and for extending it into the chamber once the chamber is closed.