[0001] This invention relates to packs which are intended to be easy to open and to be provided
with a peelable sealing lap.
[0002] Many foods (such as cheeses) and other products are packaged for sale and distribution
in flow wrap (or pillow pack) form. These packs, produced on both vertical and horizontal
machines, are often produced in films designed to give extremely strong and even hermetic
seals. Such films are often themselves very strong and tear resistant, in order to
give a high level of seal strength and thus product protection. However, such strong
packs may be very difficult to open, and devices such as tear strips and end seal
nicks are often included to allow the user easier access. These methods of gaining
entry to the product inevitably tear the material from which the pack is produced,
and consequently re-wrapping of any unused part of the contents is made difficult
or ineffective. The preferred method of entry into the pack is therefore to open a
seal, rather than to tear the film. On most systems the seals are heat-fused to a
high degree and are therefore not easily openable, but peelable materials and adhesive
systems do exist.
[0003] An ideal method of producing easily openable packs is to have some degree of peelability,
if only in the seal areas. Such seal areas can be provided from a so-called T junction
as depicted in Figures 1A and 1B of the accompanying drawings.
[0004] Where a single layer of material is folded round on itself to form a seal, three
types of seal can be formed. The outer surface of the material is referred to the
A surface and the inner surface of the material is referred to as the B surface. The
three types of seals which can be formed are as shown in Figures 2A, 2B and 2C of
the accompanying drawings, which show, respectively, an A-A seal (outer surface to
outer surface), a B-B seal (inner surface to inner surface), and an A-B seal (outer
surface to inner surface). It will be appreciated that it is the B-B seal as shown
in Figure 2B which can produce, on opening, a T-junction as shown in Figure 1B.
[0005] The A-B seal as shown in Figure 2C is a standard lap (overlap) and, depending on
the nature of the A-B seal, can be peelable.
[0006] Where a surface of a sheet of material is to form a seal, which can be either a peelable
seal or a non-peelable seal, the surface needs to have the ability to be tacky or
sticky when suitably activated, typically upon heating. Where a sheet of material
is to have the ability to be tacky on both the inner and outer surfaces, the layer
of material could be formed from a laminate which could have, for example a polypropylene
layer on the A side (outer surface), a polyethylene layer on the B side (inner surface),
and a core of a nylon between the polypropylene and polyethylene. If desired additional
layers could be present in the laminate. If desired, the laminate could be formed
by coextrusion.
[0007] In terms of forming the bond, much will depend upon the combination of temperature,
pressure and duration, and these three factors can have a considerable effect on the
resulting nature of the bond, in other words as to whether it will be peelable or
non-peelable.
[0008] Typically, however, a polypropylene to polypropylene bond is not a strong bond; a
polypropylene to polyethylene bond can be made to fuse together but, generally, is
not a strong bond; and generally a polyethylene to polyethylene bond is very strong
but, when using weaker bonding conditions, can be made peelable.
[0009] In the accompanying drawings Figure 3A denotes a seal intended to be peelable; Figure
3B denotes a seal intended to be non-peelable; and Figure 3C denotes the optional
presence on a layer of an adhesive intended to be peelable which may be with or without
a covering which serves as a protective layer to counter the effect of the adhesive
until such time as any such covering is removed.
[0010] When a single length of a layer of material is used to wrap a product there will
generally speaking be a longitudinally-extending seal such as one of the types mentioned
above, as shown in Figure 4A of the accompanying drawings, and at each end of the
product the wrapping material will need to be brought together and sealed, which is
why it is generally necessary for the material to be capable of adhesion on its inner
surface so that there is an inner surface to inner surface bond formed by a heated
transverse pressure-member. However, it will be appreciated that when the pack is
opened, the presence of the A-A bond in the region of any false gussets on either
side will prevent the pack material from being fully opened, thus reducing the ease
of access to the pack. Such gussets have a high shear strength, and do not readily
peel open as they do not form a T-junction. During opening, the lap is peeled back
from the peelable A-B seal in the top central region as shown in Figure 4A and is
opened up but, as shown in Figure 4B, the material cannot be fully opened in view
of the undesired seal in the region of the false gussets.
[0011] The problem associated with the arrangement shown in Figures 4A and 4B stems from
the fact that the layer of material employed is potentially tacky on both its inner
and outer surfaces. This is necessary in order to form the lap seal of the A-B type
in the top central region of Figure 4A. A consequence of this, unfortunately, is that
false gussets can be formed by the A-A bonding formed in the outer edge regions at
the end regions of the pack, as a result of the pressure of the heated transverse
pressure member.
[0012] In the aforementioned T junction arrangement as shown in Figure 1B, it can be appreciated
that when the seal is peeled open the resulting opening may go to the left, or to
the right, or even in both directions. Thus the opening of the seal lacks any sense
of direction. This may not matter with many types of products but can cause considerable
inconvenience with certain types of products such as wedges of cheese. This is because
if the opening moves in the direction in which the wrapping material converges towards
the "nose" of the cheese, it can be difficult to remove the cheese through the relatively
narrow opening. If, in contrast, the opening moves towards the larger end of the wedge
of cheese, then it is relatively easy to remove the wedge from the package and to
re-insert any unused cheese into the package prior to any resealing.
[0013] According to the present invention, there is provided a pack formed of a length of
material having an inner surface capable of adhering to other regions of the same
inner surface, the pack having a seal formed by the inner surface of one edge region
of the pack being peelably sealed to the inner surface of the opposite edge region
of the pack, with only the one edge region being readily manually grippable and with
the opposing edge region being restrained, the arrangement being such that, in use,
when the one edge region is gripped and pulled away from the opposing edge region,
the seal opens to reveal the interior of the pack but only in a region adjacent to
the one edge region.
[0014] Thus the seal in the pack according to the present invention is directional. The
aforesaid opposite edge region can be doubled back on an adjacent region and held
in place by an adhesive, which can thus prevent access to what will be the lower "fin"
in the region of the seal.
[0015] Moreover, preferably the fin which is to be manually gripped is longer to ensure
that it is that fin that is gripped rather than the other.
[0016] The longer fin can be provided with an adhesive region so that prior to initial opening,
or upon resealing, that fin is secured in place by means of the adhesive to a region
adjacent to the opposing end region.
[0017] It is to be noted that the material which is to be employed in the production of
the pack in accordance with the present invention need be adhesive/tacky only on its
inner surface, and the outer surface can be non-adhesive and non-tacky, to avoid formation
of undesirable A-A seals in false gussets.
[0018] For a better understanding of the present invention, and to show how the same may
be carried into effect, reference will now be made, by way of example, to the accompanying
drawings in which:
Figure 5 is a cross-section through one embodiment of a pack in accordance with the
present invention;
Figure 6 is a cross-section through a second embodiment of a pack in accordance with
the present invention;
Figure 7 is a cross-section through a third embodiment of a pack in accordance with
the present invention;
Figures 8A and 8B show different lines of seals; and
Figures 9A and 9B show those seals being opened.
[0019] Referring now to Figure 5, there is shown a length of material 101 having a tacky
inner surface 102 and a non-tacky and non-adhesive outer surface 103. The sheet of
material 101 has two opposing edge regions 104 and 105. Those two edge regions 104
and 105 are bonded to each other by a peelable seal 106 which is of the B-B variety.
The edge region 105 is restrained by being adhered by an added adhesive 107 to an
adjacent underlying outer surface of the material 101.
[0020] Figure 6 is similar to Figure 5 except that the one edge region 104 is considerably
longer than the opposing edge region 105 and is bent so as to extend away from the
package, thus making it easier to grip.
[0021] Turning now to Figure 7, this is generally similar to what is shown in Figure 5,
except that one or more peelable adhesive regions, in this case two peelable adhesive
regions 108 and 109, are applied to the free edge 104 and its opposing region, nearer
to the free end of the edge 104 and the seal 106. The purpose of the adhesive 108
and 109 is to hold the access fin 104 in place to prevent accidental opening, and/or
is to enable that fin to be re-secured after the package has been opened and when
it is being re-sealed.
[0022] As has already been indicated, the strength of the various seals can be controlled
by changing seal widths, temperature of sealing, pressure of sealing and duration
of sealing, and to that there is now added provision to ensure that the pack is peeled
in a particular direction.
[0023] It is acknowledged that it may be more difficult to peel across a large seal area
than across a smaller one, and that with a straight seal the whole seal is being attempted
to be opened simultaneously. With a view to reducing the amount of force required
to open a seal, the line of the seal, instead of being longitudinal and parallel but
offset to the axis of the product, can be in zig zag form or sinusoidal, as shown
in the accompanying Figures 8A and 8B, respectively. When opening the seal is attempted,
the result is that only a small length of the seal is being peeled at any one time,
as is clear from Figures 9A and 9B respectively. Also it is advantageous for the peel
seals to be narrower than any non-desired peel seal.
1. A pack formed of a length of material having an inner surface capable of adhering
to other regions of the same inner surface, the pack having a seal formed by the inner
surface of one edge region of the pack being peelably sealed to the inner surface
of the opposite edge region of the pack, with only the one edge region being readily
manually grippable and with the opposing edge region being restrained, the arrangement
being such that, in use, when the one edge region is gripped and pulled away from
the opposing edge region, the seal opens to reveal the interior of the pack but only
in a region adjacent to the one edge region.
2. A pack according to claim 1, wherein the said opposite edge region can be doubled
back on an adjacent region and held in place by an adhesive, which can thus prevent
access to what will be a lower "fin" in the region of the seal.
3. A pack according to claim 2, wherein the fin which is to be manually gripped is longer
to ensure that it is that fin that is gripped rather than the other.
4. A pack according to claim 3, wherein the longer fin is provided with an adhesive region
so that, prior to initial opening, or upon re-sealing, that fin is secured in place
by means of the adhesive to a region adjacent to the opposing end region.