Note: Descriptions are shown in the official language in which they were submitted.
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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
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"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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~ 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
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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
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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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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
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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
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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
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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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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
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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
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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
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"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
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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
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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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