Package making – Methods – Closing package or filled receptacle
Utility Patent
1998-11-13
2001-01-02
Kim, Eugene (Department: 3721)
Package making
Methods
Closing package or filled receptacle
C053S373700, C053S374600, C053S375900, C053S374200
Utility Patent
active
06167681
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a sealing apparatus and more particularly concerns an apparatus and method for sealing together plastic layers of packaging material to form a seal.
BACKGROUND OF THE INVENTION
Packaging containers, for example those having a brick shape, for containing liquid food such as milk and soft drinks have been made through the use of packaging machines. These machines form a continuously moving web-shaped packaging material made of a flexible laminate into a tubular shape, which is then filled with the desired liquid food product. The web-shaped packaging material is manufactured with a packaging material manufacturing machine and is placed on a reel. The reel is then installed in the packaging machine where it is reeled out and routed within the packaging machine using drive mechanisms disposed in several positions in the packaging machine. The packaging material is sealed in the longitudinal direction within the packaging machine to form the tubular shape. For this reason, the packaging material possesses a laminate structure made up of a paper base layer, a film coating layer on each side of the paper base layer and, if necessary, an aluminum foil layer interposed between the paper base layer and the film.
While the tubular packaging material is being transferred downward within the packaging machine, liquid food is supplied from above to fill the inside of the tubular packaging material. Next, the packaging material is squeezed from both sides and sealed in the lateral direction at specified intervals to form interconnected primary containers having the desired shape, e.g., pillow shaped, bag shaped, etc.
Next, the laterally extending sealed portions are cut, and each of the resulting primary containers is folded along previously formed crease lines to form a container having a specified shape. Thus, a plurality of packaging containers each containing a specified amount of liquid food are formed.
To seal the packaging material in the longitudinal or lateral direction, plastic films on the packaging material surfaces are positioned so as to face each other. The aluminum foil in the packaging material generates heat by a sealing apparatus such as an inductor, and pressure is applied to heat-fuse and bond together the plastic films.
FIGS.
2
-
4
illustrate various stages in a sealing process using a conventional sealing apparatus. As illustrated, a tubular packaging material
11
is used and web-shaped packaging materials
51
,
52
are placed in face to face relation to each other in a sealing zone S. Each of the packaging materials
51
,
52
is of a laminate structure made up of a paper base layer
54
, an aluminum foil layer
55
located on the inside surface of the paper base layer
54
, and a film layer
56
of polyethylene, for example, located on the inside surface of the aluminum foil layer
55
. Although not specifically illustrated, the outside surface of the paper base layer
54
is also coated with a layer of plastic material such as polyethylene. The polyethylene portions
56
of the two packaging materials
51
,
52
are bonded together by heat fusion.
The conventional machines employ a sealing apparatus to seal and cut the packaging material
11
. The sealing apparatus is provided with cutting jaws and heat seal jaws (the specific details of which are not shown) disposed in opposing relation to each other. Each of the cutting jaws is provided with a pair of cutting rails
61
while each of the heat seal jaws is provided with a pair of sealing blocks
62
. A cutter (not shown) is disposed in the gap formed between both cutting rails
61
.
The cutting rail
61
includes a counter element
63
of rubber that extends along the cutting rail
61
, while the sealing block
62
is provided with an inductor
65
disposed opposite to the counter element
63
. The inductor
65
extends along the sealing block
62
and is provided with a projection
66
extending toward the cutting jaws. A coolant passage
67
is formed through the inductor
65
to control the temperature of the inductor
65
as a result of coolant flowing through the coolant passage
67
.
In the initial stages of the sealing process shown in
FIG. 2
, the packaging material
11
is placed between the sealing block
62
and the cutting rail
61
, whereupon the cutting jaw and the heat seal jaw are moved so that they approach each other. In the subsequent stage shown in
FIG. 3
, the cutting jaw and the heat seal jaw are moved further towards each other, and the sealing portion of the packaging material
11
is pressed hard and deformed with the inductor
65
and the counter element
63
. As shown in
FIG. 3
, a high frequency voltage is applied with a power device (not shown) to cause the aluminum foil
55
to generate heat with induction current. As a result, paired polyethylene portions
56
of the packaging material facing each other and squeezed between the paired aluminum foils
55
are heated and the polyethylene portions
56
in the sealing zone S are fused. As a result, the packaging material
11
is bonded together by heat fusion.
With conventional sealing apparatus such as that described above, it has been found that melted polyethylene
56
flows excessively beyond the sealing zones of the packaging material
11
and ends up flowing from the sealing zone S to an area AR
1
on the cutter side and to an area AR
2
on the liquid food side. As a result, the amount of polyethylene
56
contributing to the heat fusion in the sealing zone S decreases and so appropriate bond strength may not be obtained. Consequently, liquid food may leak. Furthermore, it is possible that the polyethylene
56
flowing out from the sealing zone S to the area AR
2
on the liquid food side will be rapidly cooled by the liquid food, will solidify, and will adhere to the inside surface of the primary container, thus possibly causing cracks in the vicinity of the sealing zone S during the forming process that is performed after filling and sealing.
If the induction heating energy is reduced in an attempt to prevent the polyethylene material
56
from excessively flowing out of the sealing area S, the polyethylene material
56
typically cannot be melted to the extent necessary and so sufficient bond strength cannot be achieved.
SUMMARY OF THE INVENTION
Generally speaking, a need exists for a sealing apparatus that is not susceptible to the same disadvantages, drawbacks and problems associated with conventional sealing apparatus such as those described above. In particular, it would be desirable to provide a sealing apparatus that is able to prevent melted plastic from flowing out beyond the sealing zone, even when the induction heating energy is increased for purposes of increasing the sealing strength. Similarly, it would be desirable to provide a sealing apparatus that makes it possible to obtain appropriate bond strength in the sealing zone and prevent cracks from being produced in the vicinity of the sealing zone.
In light of the foregoing, the sealing apparatus of the present invention includes a sealing block and a cutting bar positioned in opposing relation to the sealing block. A pair of spaced apart inductors is positioned in the sealing block, with each inductor being partially exposed above the front surface of the sealing block and with each inductor being provided with a first pressing portion for pressing packaging material during a sealing operation. A pair of spaced apart counter elements is mounted in the cutting bar, with each counter element being positioned in opposing relation to one of the inductors to permit the packaging material to be held between the counter elements and the inductors. A voltage applying device applies a high frequency voltage to the inductors. At least one of the inductors or the counter elements is provided with a second pressing portion that is disposed at a position corresponding to a portion of the packaging material that is nearer to the liquid food than to the sealing zone in order to press the packaging material at the ti
Iwasaki Yutaka
Tezuka Isao
Yano Keiji
Burns Doane Swecker & Mathis L.L.P.
Kim Eugene
Tetra Laval Holdings & Finance S.A.
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