[0001] 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 packaged on a relatively flat support.
[0002] 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
finished package.
[0003] We 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 package.
[0004] Accordingly, the present invention provides a process for vacuum packaging, comprising
placing at least one product article on a support sheet and covering that product
article with a cover film sealed to the support sheet with the application of vacuum
around the product article or articles and between the support sheet and cover film,
such process being 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 product
article.
[0005] 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 upstanding marginal rib in the case of a rigid support
sheet, or a recess in the support sheet due to local downward deformation. Each of
these possibilities for the "collector" formation constitutes a particularly convenient
way of defining a location to absorb surplus cover film material so as to avoid webbing.
[0006] Preferably the "collector" formation and the collected cover film material is subsequently
trimmed from the finished pack to leave an attractive end product with no sign of
the surplus cover film.
[0007] Advantageously this process is incorporated in a fully automated packaging line by
carrying out the packaging 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. Other ways of achieving the collector formation are
well within the capability of the expert in this field.
[0008] The invention also provides 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 or 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.
[0009] Preferably the means defining an upstanding or recess formation includes an adjustable
rib projecting into the chamber, thereby allowing the height of the rib, and hence
the volume of cover film "collected", to be adjusted according to the height of the
product article being packaged.
[0010] Advantageously, means may be provided for retracting the rib and for extending it
into the chamber once the chamber is closed. Thus, in an automated packaging line
the base mould has no upstanding formation to impede horizontal advance of a web of
packs and indexing of a fresh product article or batch of product articles to the
packaging station:
In order 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 package showing "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
accordance with the present invention;
Figure 4 is a schematic sectional view showing the vacuum chamber closed around the
product articles and films during the formation of the package of Figure 3;
Figure 5 is an overhead perspective view showing the base portion of the chamber illustrated
in Figure 4;
Figure 6 is a detail, on the same section plane as Figure 4, but showing a depressed
cover film collector" formation.
[0011] 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 covered by
a cover film 15.
[0012] 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.
[0013] We have now discovered that if a cover film "collector" formation such as a "dummy
product"-like formation is arranged alongside an article such as 11, 12, 13 or 14
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.
[0014] 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 be the only product
article on the support base) such as to avoid the formation of "webbing" with that
article.
[0015] 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 the cover film 15, a base 20 co-operating
with cover 19.
[0016] 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 hydraulic) 22 only
one of which is shown in Figure 4.
[0017] Figure 5 shows an overhead perspective view of the base 20 of Figure 4, including
the two "dummy product"-defining plates 21 but, for the purpose of simplicity of illustration,
the operating rams 22 have been omitted from this drawing.
[0018] The operation of the apparatus of Figures 4 and 5, and of the process exemplified
by Figures 3, 4 and 5 is as follows:-A continuous support sheet 10 is advanced over
the base 20 in a direction parallel to the extent of 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.
[0019] 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. Once the cover film 15 has arrived
under the chamber 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 21 to a position shown in Figure 4 where
they deform the now clamped support sheet 10, and the cover film 15 thereon, upwardly
to define the illustrated "dummy product" ribs 17.
[0020] Although not mentioned above, it will of 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 may be incorporated in the
chamber 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 substantially
as disclosed in U.S. Patent No. 3,694,991 (Perdue et al). Alternative processes may
be substantially as disclosed in U.S. Patent No. 3,491,504 (Young et al), U.S. Patent
No. 3,634,993 (Pasco and Wolfelsperger), U.K. Patent No. 1,445,285 (Du Pont), U.S.
Patent No. 3,260,032 (Hill et al) or in Modern Packaging (May 1971) at pages 60 to
62.
[0021] Figure 4 shows one form of means for opening and closing the chamber 19, 20, namely
a fluid pressure-operated jack 23 programmed to operate in a repetitive cycle coordinated
with operation of the feed means 25 for the support sheet 10 and the cover film 15
so that the film-advancing movement occurs while the chamber is open, and the film
advance is interrupted as the chamber closes. A suitable vacuum source is connected
to the duct 24 for evacuating the space between the support sheet 10 and the cover
film 15, the evacuation operation being coordinated, by means of a central programmer,
with the operation of the chamber-opening and-closing means in a programme which is
well known to the expert in this art.
[0022] Although the above description 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.
[0023] 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.
[0024] The chamber cover 19 is then raised, 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 package shown
in Figure 3 is severed from a continuous strip of such packages having a succession
of such rectangular arrays 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 four separate vacuum packages.
[0025] 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.
[0026] 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 leakage of the finished pack. In any case, bearing in mind that the "webbing"
18 is now formed at the "dummy product"-defining ribs 17 away from the corners of
the array of product articles ll-14, this 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 "webbing" at those corners which could give rise
to unacceptable leakage; this has been avoided by the process of the present invention.
[0027] As indicated above, the height of the "dummy product"-defining ribs 17 is preferably
adjustable and consequently 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 may be adjustable as disclosed in U.S.
Patent No. 3835618.
[0028] As will be appreciated, the apparatus 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 configuration can be used for various
different layouts of product articles on the support sheet 10.
[0029] An alternative embodiment of the process is one in which the plates 21 are no longer
required but, instead, "dummy products" in the form of filler strips are laid on the
support sheet 10 in the selvage region where the ribs 17 arise in Figures 3 and 4.
These "dummy products" are preferably disposable items so that they can be discarded
with the trimmed selvage at the subsequent trimming station.
[0030] A further possibility, particularly suitable in the case of packaging using relatively
stiff backing boards, such as an expanded polystyrene tray coated with an air-impervious
surface film to facilitate vacuum packaging, is one in which the lateral edges of
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 embodiment
of package shown in Figure 4.
[0031] It is not essential for the various product articles 11, 12 13 and 14 to be severed
from one another. It would instead be possible to package simultaneously four separate
product articles which will be sold in a "consume some-save some" pack enabling the
consumer to cut open each of the four product-containing "bubbles" separately. The
display of such a pack may even be effected with the aid of one or both of the "dummy
product" formations left on the pack to enable the pack to be suspended, 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 sufficiently
rigid to support the weight of the pack.
[0032] 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 pack containing such an individual product article, the punching operation
taking place simultaneously with the operation of severing the articles one from another.
[0033] Any suitable medium may be used for the support sheet, ranging from a single or multi-layer
film preferably having a heat-sealable upper surface, to a rigid or semi-rigid material,
for example the above- mentioned expanded polystyrene board having a coating on its
upper 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 contact with the
support sheet to facilitate sealingo Such single layer or multi-layer films of self-welding
or heat-sealable type are well known in the art.
[0034] Fig 6 shows an alternative embodiment in which the cover film "collector" formation
is defined not by a "dummy product" but instead by a local downwardly deformed region
or recess formation 17a in the support sheet. 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.
[0035] Generally the recess type of "collector" formation defines an aperture of adequate
size in the support sheet and may simply be a hole in the support sheet.
[0036] The process for forming the pack shown in Figure 6 will be analogous to the process
employing upstanding "dummy pack" formations and the "collector" recess or aperture
may be preformed or formed in situ in the chamber. The design of suitable apparatus
for achieving this is well within the capability of the expert in this art.
[0037] 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 skilled in this art,
while remaining within the scope of the following claims.
1. A process for vacuum packaging, comprising placing at least one product article
on a support sheet and covering that product article with a cover film sealed to 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 (16) (17) (17a) (21) on the side of the support
sheet (10) to which the cover film (15) is attached during the closing operation,
such formation (16) (17) (17a) (21) serving as a cover film "collector" to absorb
material of the cover film (15) which would otherwise form webbing on the adjacent
product article (11, 12, 13, 14).
2. A process according to claim 1, characterised in that said "collector" formation
(16) is formed by an upwardly deformed region of the support sheet (10).
3. A process according to claim 1, characterised in that said "collector" formation
is formed by a filler between the support sheet (10) and the cover film (15).
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 (17a) of the support sheet (10).
6. A process according to any one of the preceding claims, and further characterised
by the step of trimming the said "collector" formation (16) (17) (17a) (21) from the
sealed pack.
7. A process according to any one of the preceding claims, 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
(11, 12, 13, 14) on the support sheet (10); and, after sealing, the product articles
(11, 12, 13, 14) which are packed simultaneously at the sealing station are trimmed
from the continuous composite web comprising the support sheet (10) and cover film
(15).
8. Apparatus for vacuum packaging, comprising: a vacuum chamber (19, 20) adapted to
receive a support sheet (10) and a cover film (15) over the support sheet; and means
for evacuating a space between the cover film (15) and support sheet (10) to form
a vacuum pack of the cover film sealed to the support sheet around a product article
(11, 12, 13 or 14); characterised by means (21) defining an upstanding formation (16)
or a recess formation (17a) in the cover film (15) 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 (11, 12, 13 or 14) being packed.
9. Apparatus according to claim 8, characterised in that said means defining an upstanding
or recess formation include an adjustable rib (21) projecting into the chamber.
10. Apparatus according to claim 9, and further characterised by including means (22)
for retracting said rib (21) and for extending it into the chamber (19, 20) once the
chamber is closed.