Packaging machine

A packaging machine (1) is adapted to form a web (8) of packaging material into a tube to surround items (3) to be packed, the tube then being closed, sealed and severed between successive items to produce individual packages (5). The tube is formed by sealing one surface of an edge zone of the web to the same surface of the opposite edge zone of the web so that, in the finished package, the sealed zones form a flap (45) extending longitudinally of the package. The machine comprises a support surface (2) having a longitudinal slot (43) therein, the slot being adapted to accommodate the flap, the machine further comprising at least two pairs of rollers (18,22), at least the first (18) of the pairs of rollers being located beneath the support surface (2), the pairs of rollers forming successive nips for gripping the flap (45) and driving the partly formed packages along the support surface (2) towards a closing, sealing and severing station (23) and for forming the required seal between the edge zones of the web (8), and means (32,34) for applying a vacuum to the tube adjacent the point where the edge zones of the web are brought together to form the tube, wherein the width of the longitudinal slot (43) for at least a section of the slot downstream of the point of application of the vacuum, is sufficiently great relative to the distance of at least the first pair of rollers (18) below the support surface (2) to allow an air passage to be formed within the tube as it moves towards the closing, sealing and severing station (23).

This invention relates to a packaging machine, and more particularly to a 
packaging machine of the type in which a web of packaging material is 
formed into a tube to surround the items to be packed and the tube is then 
sealed and severed between successive items to produce individual 
packages. The invention is more particularly concerned with packaging 
machinery of this type in which the tube is formed by sealing one surface 
of an edge zone of the web to the same surface of the opposite edge zone 
of the web so that, in the finished package, the sealed zones form a flap 
extending longitudinally of the package. 
Packaging machines of the type described above are commonly used in the 
food manufacturing industry, more particularly for the packaging of 
biscuits and similar items. For the purposes of illustration the invention 
will be described in the context of a biscuits packaging machine. It 
should be appreciated, however, that the invention is of more general 
applicability and may be used in a wide range of packaging machines of the 
type described above. 
In the packaging of biscuits by such machines the biscuits may already be 
held in containers of card or plastics material, for example, or they may 
be loose and simply assembled together into groups, each group being 
intended to be packaged to form a single packet of biscuits. In the latter 
case, the packaging machine bed is horizontal and the biscuits are 
arranged vertically--i.e. the biscuits stand on edge--as they are fed into 
the packaging machine by means of a conveyor. The groups of biscuits are 
automatically spaced apart by a distance sufficient to enable the 
packaging tube, between consecutive groups of biscuits, to be sealed and 
severed to form the individual packets required. 
In machines of the prior art, the apparatus for sealing and severing the 
tube to form individual packets is typically located several packet 
lengths downstream of the tube forming station. This arrangement leads to 
two recognized disadvantages. Firstly, between the tube forming station 
and the tube severing station the biscuits must be supported and 
maintained in their pre-formed groups. In particular, because the biscuits 
are standing on edge, care must be taken to prevent the leading or 
trailing biscuit in each group from falling over. Because, along the 
relevant portion of the machine length, the biscuits are totally enclosed 
by the tube it is not possible to support the biscuits directly by means 
of fingers extending from the conveyor. In the circumstances, conventional 
practice has been to provide a pair of chains, one each side of the line 
of the tube, to engage the lateral faces of the tube and maintain the 
biscuits in the correct position. Each time the packaging line is changed 
for a different type of biscuit the chains must be re-adjusted. This is a 
time consuming process and one which inevitably leads to certain waste 
production. Secondly, excessive amounts of air tend to be trapped within 
the finished packages with the result that subsequent handling and packing 
of the packages into outer cases or containers for transport is rendered 
difficult. 
With a view to overcoming the problem of excessive air within the packages 
it has been proposed to apply a vacuum to the tube and, in a known 
arrangement, the vacuum is applied to the packaging tube adjacent the 
point where the lateral edges of the web are brought together to form the 
tube. The vacuum is simply applied by means of a suction chamber under the 
support surface on which the groups of biscuit move into and through the 
packaging machine. The conveyor feeds the groups of biscuits to the 
packaging machine and the end of the conveyor passes through the suction 
chamber, which is of sufficient size to accommodate the end roller of this 
conveyor. Whilst this proposal does, to an extent, reduce the amount of 
air contained in the final packages it does not completely eliminate the 
air problem. Firstly, because the conveyor passes through the suction 
chamber it is not possible to seal the suction chamber from the outside 
environment, so that it is difficult to obtain an effective vacuum without 
expending significant power. Secondly, it will be appreciated that, since 
the final sealing and severing station is located two or three package 
lengths downstream of the point where the vacuum is applied, it is 
difficult to expel air from the final package which is about to be closed 
and severed because of the intervening two or three groups of product 
located between the severing point and the point of application of vacuum. 
When the sealing and severing of the package end takes place, the air 
which is left between the groups of biscuits in the packaging web at the 
point where the package end is to be sealed and severed is forced back 
towards the groups of biscuits upstream causing puffing of the web. This 
puffing tends to disturb the biscuits, particularly the leading and 
trailing biscuits, in the upstream groups, causing them to fall over if 
external supports, such as side chains, are not provided. 
In conventional machines, after the edge zones of the web have been brought 
together, the flap so formed is gripped between nips of successive pairs 
of rollers located beneath the support surface or machine bed on which the 
partly formed packages slide. These rollers drive the partly formed 
packages towards the sealing and severing station and, by applying 
pressure and/or heat to the packaging web located between the nips, the 
required seal between the lateral zones of the web is formed. If the web 
is to be sealed in a cold seal process, at least two pairs of rollers are 
preferred. Although only one pair of rollers may be necessary to form the 
seal, two pairs are preferred to provide sufficient pull to drive the 
partly formed packages of biscuits towards the sealing and severing 
station. If a heat seal process is to be used, it is preferred to provide 
at least two pairs of heated rollers to plasticize and seal the web, in 
which case at least one further pair of rollers needs to be provided to 
drive the partly formed packages towards the sealing and severing station. 
In our pending European patent application No. 94305754.7 we disclose how 
an improvement in the air extraction from the final package can be 
achieved if the edge of at least one roller of at least the first pair of 
rollers downstream of the point of application of the suction is relieved 
whereby an air passage is formed within the tube at the point where the 
tube passes the relevant pair of rollers as it moves downstream in the 
machine direction. More especially, a substantial improvement in air 
extraction can be achieved when both of each pair of rollers at each nip, 
except the final nip, are relieved by a chamfer whereby, as the package 
passes each of the relieved rollers, a generally triangular zone is formed 
inside the web between the web lying against the chamfered rollers and the 
lower face of the product being packaged. 
According to the present invention there is provided a packaging machine 
adapted to form a web of packaging material into a tube to surround items 
to be packed, the tube then being closed, sealed and severed between 
successive items to produce individual packages, the tube being formed by 
sealing one surface of an edge zone of the web to the same surface of the 
opposite edge zone of the web so that, in the finished package, the sealed 
zones form a flap extending longitudinally of the package, the machine 
comprising a support surface having a longitudinal slot therein, said slot 
being adapted to accommodate said flap, said machine further comprising at 
least two pairs of rollers, at least the first of said pairs of rollers 
being located beneath the support surface, said pairs of rollers forming 
successive nips for gripping said flap and driving the partly formed 
packages along the support surface towards a closing, sealing and severing 
station and for forming the required seal between the edge zones of the 
web, and means for applying a vacuum to the tube adjacent the point where 
the edge zones of the web are brought together to form the tube, wherein 
the width of said longitudinal slot for at least a section of the slot 
downstream of the point of application of the vacuum, is sufficiently 
great relative to the distance of at least the first pair of rollers below 
the support surface to allow an air passage to be formed within the tube 
as it moves towards the closing, sealing and severing station. 
In a preferred embodiment of the invention, for the entire length of the 
slot downstream of the point of application of the vacuum until the nip of 
the final pair of rollers is reached, the width of the slot is 
sufficiently great relative to the distance of the rollers below the 
support surface to allow the air passage to be formed. 
In a machine incorporating the present invention substantially all surplus 
air will be removed from the final package before closing, sealing and 
severing, with the result that in the individual packages formed by the 
machine the packaging film closely conforms to the product within it. 
Because the rollers and the items within the tube hold the packaging film 
under tension the air passage does not collapse when a vacuum is applied. 
In addition, when the sealing and severing of the package end takes place, 
any small amounts of air left in the package are expelled towards the 
groups of product located between the severing point and the point of 
application of the vacuum, and the air passage allows this air to be 
passed back readily to the point of application of the vacuum, avoiding 
disturbance to the biscuits in the upstream groups. Moreover, this air 
which is forced back up the tube also assists in preventing the collapse 
of the air passage. 
The improved air extraction of the present invention causes the web, in the 
zones between the individuaI groups of product, to be sucked inwardly 
towards the centre of the tube, notwithstanding that the tube is 
maintained under tension as it is pulled through the machine line by the 
rollers. The effect of this partial collapse of the tube and the effective 
application of the vacuum is to prevent the biscuits forming each group 
from being displaced from the vertical array in which they are fed to the 
packaging station. Hence, the side chains often previously required to 
maintain the biscuits in the desired orientation may be omitted, resulting 
in a general simplification of the machine and the removal of the 
undesirable setting step then required each time the product line being 
handled by the packaging machine is changed. 
As the tube of the invention collapses under the influence of the applied 
vacuum, gussets are automatically formed in the lateral edges of the tube. 
Heretofore, when packaging products of, for example, rectangular 
cross-section it has usually been necessary to form gussets by mechanical 
gusseting fingers immediately prior to operation of the closing, sealing 
and severing machine. Since, in embodiments of the present invention, 
gussets are automatically formed by the collapsing tube, there is no 
requirement for gusseting fingers. 
In a particularly preferred embodiment of the invention, the support 
surface is cut away at the final pair of rollers and the top surface of 
the final pair of rollers is level with the support surface. 
A further improvement in air extraction can be achieved by applying the 
suction to the tube downstream of the end of the conveyor which feeds the 
groups of biscuits into the packaging machine, between the end of the 
conveyor and the first pair of rollers at which the edges of the web are 
brought together to form the tube. The conventional suction chamber may be 
replaced with a small housing fitted beneath the support surface on which 
the groups of biscuits move as disclosed in our pending European 
application No. 94305754.7.The housing, in combination with the support 
surface, then substantially surrounds the point where the lateral edges of 
the web are brought together to form the packaging tube and is 
sufficiently small that the end roller of the conveyor does not interfere 
with the housing. The housing may be located beneath guide slots in the 
support surface which bring the edges of the web together, and may extend 
above and beneath the first pair of rollers to the point where the nip is 
formed between the first pair of rollers. The housing preferably seals 
against the underside of the support surface and closely abuts the top 
surface and the underside of the first pair of rollers. A source of vacuum 
is applied to the housing and, because the housing and support surface 
substantially surround the point where the lateral edges of the web are 
brought together, there is little leakage from the surroundings into the 
evacuated housing and the vacuum source need be considerably less powerful 
than in known machines. 
A particularly preferred embodiment of the invention comprises three 
successive pairs of rollers.

Referring firstly to FIG. 1, a packaging machine 1 comprises a bed or 
support surface 2 along which groups 3 of a product 4 pass to form 
discrete packets 5 of the product. Apparatus is provided upstream of the 
machine 1 for grouping the product 4 into the required groups 3 and for 
spacing the groups apart for supply to the packaging machine,the groups 
being conveyed into the packaging machine by conveyor 30 which returns 
around end conveyor roller 31. The conveyor 30 may be provided with 
fingers 40 for supporting the groups 3 on the conveyor. Such apparatus 
will be well known to those skilled in the art and will not be described 
further here. 
As the product passes through the machine a tube 6 is formed about the 
successive groups 3 in a tube forming station 7. In the tube forming 
station 7, a web 8 of, e.g., plastics film from a suitable supply reel 9 
is guided and shaped into a tube. The tube is formed by bringing one face 
of one edge zone 10 of the web into engagement with the same face of the 
opposite edge zone 11 (see FIGS. 2 and 3). For this purpose, the web is 
initially deformed into a generally inverted U-shape and the edge zones 
10,11 are fed between guides 13,14 (for the edge zone 10) and 15,16 (for 
the edge zone 11). The edge zones then pass into a longitudinal slot 43 in 
the support surface and also into the nip between a pair of rollers 17,18 
(see FIG. 3) and are sealed to form a flap 45. The rollers 17,18 are 
driven and accordingly grip the flap and thus move the tube forward in the 
machine direction. In this embodiment two further pairs of rollers are 
located downstream of the tube forming station of which one of each pair 
20, 22 can be seen in FIG. 1. The first two pairs of rollers are 
positioned below the support surface of the machine bed. The top surface 
of the final pair of rollers 22 is level with the top of the support 
surface 2 and forms part of the surface along which the tube moves, the 
machine bed being cut away to accommodate the rollers. 
Located two or three package lengths downstream of the tube forming station 
is a tube closing, sealing and severing station 23 in which the tube is 
flattened to close it, sealed and severed through the seal, thereby 
simultaneously closing the final package 24 and severing it from the tube 
and forming the leading closed and sealed end of the next package 25. 
A housing 32 fitted downstream of the conveyor roller 31 and below the 
plate 33 forming the guides 14 and 15 forms a plenum 26 (see FIG. 5) which 
is connected to a vacuum source via a tube or duct 34 to establish a 
subambient pressure at the point of tube formation. It will be appreciated 
that because of the shape of the web at this point and the relatively fine 
nature of the web material only a limited vacuum can be drawn from the 
plenum 26. The housing 32 is fitted beneath the slots in the machine bed 
which form the guides for bringing the edges 10, 11 of the web together 
and then feeding the edges to the first rollers 17,18. The sides 35 of the 
housing 32 have walls 46 which extend below the first pair of rollers 
17,18 to the point where the nip is formed between the two rollers 17,18 
as well as upper front walls 47 which extend above the first pair of 
rollers 17, 18 to the point where the nip is formed between them. The 
sides 35 of the housing (see FIG. 4) are shaped to abut against the 
underside of the machine bed or support surface 2 and to seal around the 
two rollers 17,18. Preferably, the sides 35 have top portions 36 formed 
from a plastics material for providing a more effective seal against the 
machine bed and around the rollers. Each top portion 36 is provided with 
an arcuate edge 37 between the upper and lower front walls 46 and 47, the 
arcuate edge 37 being adapted to cooperate with and abut the 
circumferential edge of roller 17 or 18, respectively. Thus, the housing 
32 cooperates with the rollers and the machine bed substantially to 
surround the point where the edges 10, 11 of the web are brought together, 
so that a vacuum may be developed in the plenum 26 by connecting duct 34 
to a vacuum source. Because the plenum 26 is sealed from the outside 
atmosphere save at the points where the web enters and leaves the housing 
32, the vacuum can be provided by, for example, a relatively low powered 
fan operating at around 0.5 KW, or less. 
In accordance with the present invention this limited vacuum is utilized in 
a particularly effective manner to eliminate excess air from the final 
package 24 so that in the completed and severed package the web material 
lies closely against the product which has been packed. To this end, the 
longitudinal slot 43 in the support surface has a width which is 
sufficiently great when compared to the distance of the rollers 17, 18 
below the support surface such that, as more particularly shown in FIG. 3, 
a generally triangular air passage 29 is formed between the product and 
the packaging web as the tube advances past the nip formed between rollers 
17 and 18 and preferably also between the pair of rollers 20. The 
longitudinal slot may have this particular width for the length above the 
rollers 17, 18 and may extend also with that width above the pair of 
rollers 20, such that the air passage 29 in the tube extends as far as the 
final pair of rollers 22. The width of the slot may, for example, be in 
the range of 5 to 40 mm, and is preferably approximately 20 mm, while the 
distance of the top of the rollers 17, 18 below the top of the support 
surface 2 may, for example, be in the range of 2 to 15 mm and is 
preferably no more than 8 mm. The angle A included by the packaging film 
in slot 43, as shown in FIG. 3, is preferably of the order of 90 degrees 
or more. However, the dimensions of the slot and of the vacuum passage 29 
are dependent on the type and size of the product being packaged. Clearly, 
larger products will be packaged in larger packages where a greater amount 
of air will need to be evacuated, so that the cross-sectional dimensions 
of the vacuum passage 29 may be larger to allow for more rapid or more 
effective evacuation of the air. In each case, the most appropriate 
dimensions may be selected by a simple process of trial and error 
depending on the product and package size, the strength of the vacuum used 
and the result to be achieved. Clearly, if a vacuum passage with a larger 
cross-section is required, it is more effective to increase both the width 
of the slot and the distance of the top of the rollers below the top of 
the support surface, rather than just increasing one of these two 
dimensions. 
The effect of the air passage 29 is to enhance substantially the 
effectiveness of the vacuum applied at the plenum 26 to the extent that 
the web, in the zone 50 between the successive groups 3 of product, tends 
to partially collapse as generally illustrated in FIG. 1. One effect of 
this is that the web itself holds the product in the required 
configuration and the side chains required in the prior art are no longer 
required. In addition, the final package is substantially devoid of excess 
air. Also, as the tube progressively collapses towards the closing, 
sealing and severing station 23, gussets are automatically formed in the 
side of the tube thereby obviating the previous requirement for gusseting 
apparatus. In addition, as the tube is closed, sealed and severed between 
packages 24 and 25, the tube is compressed in the closing, sealing and 
severing station 23 and a small amount of air is thus forced back into the 
incoming packages 25, 38 and so on. The air passage 29 allows this air to 
pass readily through the incoming packages and to be extracted through 
plenum 26, without disturbing the biscuits in the incoming packages. In 
fact, this air being forced back through the air passage 29 helps prevent 
the air passage from collapsing under the application of the vacuum as 
discussed above. 
It will be noted that the top surface of the final pair of rollers 22 is 
level with the support surface 2. Accordingly, as the web passes through 
the final nip prior to the closing, sealing and severing station, the seal 
between the facing zones of the web is completed. It has been found that 
the lack of an air passage in the tube at the final nip does not, as a 
practical matter, interfere with the air extraction process. While the 
invention has been described in the context of a biscuit packaging machine 
with three pairs of rollers, it would be equally applicable to machines 
with two pairs of rollers, in which case, the widened slot only extends 
above the first pair of rollers, or to machines with more than three pairs 
of rollers, in which case the widened slot extends at least above the 
first pair of rollers, and preferably above all but the last pair of 
rollers. 
Whilst the invention has been described with particular reference to the 
packaging of biscuits it will be appreciated that it is of general 
applicability to many packaging applications in which a product is 
packaged by first forming a tube about the product and then sealing the 
tube to form individual packages.