U.S. patent application number 10/061133 was filed with the patent office on 2002-11-21 for contoured seal facing for seal jaws in vertical form, fill, and seal packaging system.
Invention is credited to Cooper, Rodney Wayne, Kohl, Garrett William, Meyer, Eric Eugene, Tucker, Steven Kenneth.
Application Number | 20020170272 10/061133 |
Document ID | / |
Family ID | 22033802 |
Filed Date | 2002-11-21 |
United States Patent
Application |
20020170272 |
Kind Code |
A1 |
Cooper, Rodney Wayne ; et
al. |
November 21, 2002 |
Contoured seal facing for seal jaws in vertical form, fill, and
seal packaging system
Abstract
In order to handle bag configurations having extra layers in
some portions, especially where thicker materials are used, the
facings of the sealing jaws are relieved in the area of the extra
layers, so that even pressure is applied to the material across the
entire seal area. An improved transverse seal is obtained using
this method.
Inventors: |
Cooper, Rodney Wayne;
(Little Elm, TX) ; Kohl, Garrett William; (Allen,
TX) ; Meyer, Eric Eugene; (Allen, TX) ;
Tucker, Steven Kenneth; (Hurst, TX) |
Correspondence
Address: |
CARSTENS YEE & CAHOON, LLP
P O BOX 802334
DALLAS
TX
75380
|
Family ID: |
22033802 |
Appl. No.: |
10/061133 |
Filed: |
January 31, 2002 |
Current U.S.
Class: |
53/450 ;
53/374.8; 53/479; 53/550 |
Current CPC
Class: |
B29C 66/71 20130101;
B29C 66/7373 20130101; B29C 66/1122 20130101; B29C 66/71 20130101;
B29C 66/81435 20130101; B29K 2023/00 20130101; B29C 66/4312
20130101; B29K 2067/00 20130101; B29K 2023/12 20130101; B29C 65/305
20130101; B29C 66/8491 20130101; B29C 66/133 20130101; B29C 65/18
20130101; B29C 66/8167 20130101; B29C 66/83221 20130101; B29C 66/71
20130101; B29C 65/7451 20130101; B29C 66/72328 20130101; B29C
66/346 20130101; B29C 66/135 20130101; B65B 51/30 20130101; B29C
66/4322 20130101; B29C 66/71 20130101; B29C 66/112 20130101; B29C
66/81431 20130101 |
Class at
Publication: |
53/450 ; 53/479;
53/550; 53/374.8 |
International
Class: |
B65B 009/10; B65B
051/14 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2001 |
GB |
2101909 |
Claims
What is claimed is:
1. A set of heat sealers for installation on a form and fill
machine, said set of heat sealers comprising: a first seal facing
surface; a second seal facing surface, wherein a first level of
said first facing surface and a first level of said second facing
surface generally fit together in a mating fashion; wherein a
second level of said first facing surface is recessed from said
first level of said first facing surface by an amount that
approximately equalizes the pressure across a seal being
formed.
2. The set of heat sealers of claim 1 wherein said first and said
second facing surfaces have generally corrugated surfaces.
3. The set of heat sealers of claim 1 wherein said second level of
said first facing surface is recessed by the thickness of a
material with which said set of facings are designed to work.
4. The set of heat sealers of claim 1 wherein said first seal
facing surface is a mirror image of said second seal facing
surface.
5. The set of heat sealers of claim 1, wherein said heat sealers
are sealing jaws.
6. The set of heat sealers of claim 1, wherein said heat sealers
are seal facings.
7. The set of heat sealers of claim 1, wherein said first seal
facing surface has relieved areas, but said second seal facing
surface does not.
8. The set of heat sealers of claim 1, wherein both said first seal
facing surface and said second seal facing surface have relieved
areas.
9. An improvement to a form, fill, and seal machine, said
improvement comprising: a first seal facing surface; a second seal
facing surface, wherein a first level of said first seal facing
surface and a first level of said second seal facing surface
generally fit together in a mating fashion; wherein a second level
of said first facing surface is recessed from said first level of
said first facing surface by an amount that approximately equalizes
the pressure across a seal being formed.
10. The improvement to a form, fill, and seal machine of claim 9,
wherein said first and said second seal facing surfaces have
generally corrugated surfaces.
11. The improvement to a form, fill, and seal machine of claim 9,
wherein said second level of said first facing surface is recessed
by the thickness of a material with which said set of heat sealers
are designed to work.
12. The improvement to a form, fill, and seal machine of claim 9,
wherein said first seal facing is a mirror image of said second
seal facing.
13. The improvement to a form, fill, and seal machine of claim 9,
wherein said first seal facing surface is part of a removable seal
facing.
14. The improvement to a form, fill, and seal machine of claim 9,
further comprising stripping bars.
15. The improvement to a form, fill, and seal machine of claim 9,
further comprising heat probes capable of heating said set of heat
sealers.
16. The improvement to a form, fill, and seal machine of claim 9,
further comprising crumb plates.
17. The form, fill, and seal machine of claim 9, further comprising
a knife assembly positioned between a first and a second portion of
said first facing surface.
18. A method for manufacturing a bag with a vertical form, fill,
and seal machine, said method comprising the steps of: forming a
packaging material into a shape in which a first area to be sealed
has a first number of layers of packaging material and a second
area to be sealed has a second number of layers of packaging
material, wherein said first number is greater than said second
number; relieving sections of a pair of heat sealer facings which
contact said first portion of an area to be sealed so that an
approximately equal pressure is provided across said first and said
second areas
19. The method of claim 19, wherein each of said pair of heat
sealer facings are relieved approximately the thickness of one
layer of a material with which the set of facings are designed to
work.
20. The method of claim 19, wherein said relieving step relieves
sections of said pair of heat sealer facings in mirror images of
each other.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field
[0002] The present invention relates to a seal facing design for
use in a sealing carriage of a vertical form, fill and seal
packaging machine, and, in particular to a modified facing that can
allow for differences in the relative thickness of material in
different sections of the seal.
[0003] 2. Description of Related Art
[0004] Vertical form, fill, and seal packaging machines are
commonly used in the snack food industry for forming, filling, and
sealing bags of chips and other like products. The bags are made
from a packaging film, such as polypropylene, polyester, paper,
polyolefin extrusions, adhesive laminates, and other such
materials, or from layered combinations of the above. Packaging
machines take a sheet roll of a packaging film and form the film
into a vertical tube around a product delivery cylinder. In FIGS.
1a and 1b, the vertical tube of packaging film 100 is seen in
cross-section prior to being sealed along its length to form a back
seal. FIG. 1a is a schematic of a "lap seal" embodiment of a back
seal being formed on a tube of film. FIG. 1b illustrates a "fin
seal" embodiment of a back seal being formed on a tube of film.
[0005] With reference to FIG. 1a, a portion of the inside of
packaging film 100 is mated with a portion of the outside of
packaging film 100 in the area indicated by the arrows to form a
lap seal. The seal in this area is accomplished by applying heat
and pressure to the film in such area.
[0006] In the fin seal variation shown in FIG. 1b, the inside of
packaging film 100 is folded over and then sealed on itself in the
area indicated by the arrows. Again, this seal is accomplished by
the application of heat and pressure to the film in the area
illustrated.
[0007] The form, fill, and seal machine then applies a pair of
heat-sealing jaws across the entire width of the tube to form a
transverse seal. This transverse seal acts as the top seal on the
bag below and the bottom seal on the package being filled and
formed above. After the seal has been formed, a cut is first made
across the sealed area to separate the finished package below the
seal from the partially completed package above the seal, then the
film tube is pushed downward to draw out another package
length.
[0008] Before the sealing jaws form each transverse seal, the
product to be packaged is dropped through the product delivery
cylinder and is held within the package by the bottom transverse
seal. Prior to forming the upper transverse seal, the sealing jaws
are brought together in two steps. First, a pair of stripping
plates, or bars, is brought into contact with the film in order to
flatten the tube and strip product out of the area to be sealed.
Second, the seal jaws or facings are brought together, thereby
forming the transverse seal.
[0009] The bag sealing functions of a vertical form, fill, and seal
machine are best described with reference to FIGS. 1c and 1d. FIG.
1c shows a sealing carriage on a prior art form, fill, and seal
packaging machine. FIG. 1d is a cross-section of a prior art
sealing assembly installed in the carriage. Opposed transverse seal
facings 102, 104 are shown attached to opposed bridge assemblies
106, 108. Behind each seal facing 102, 104 is a heat probe 128, 130
capable of heating the exposed surface of the seal facings up to
450.degree. F. during operation. Placed between the seal facings
102, 104 and their respective bridge assemblies 106, 108 is a heat
separator 136, 138. The heat separators 136, 138 provide a thermal
barrier between the seal facings 102, 104 and the bridge assembly
106, 108 in order to minimize heat transfer to the bridge assembly
106, 108 and other components attached thereto. A thermocouple or
thermistor 132, 134 is placed between the heat separator 136, 138
and the heat probe 128, 130 in order to monitor the seal facing
102, 104 temperature. As previously described, a transverse seal is
formed when a tube of film placed between the seal facings 102, 104
is flattened as the seal facings 102, 104 are brought in close
proximity to each other. To accomplish this, both bridge assemblies
106, 108 move towards each other on stationary rods 110, 112.
[0010] Also shown attached to the bridge assemblies 106, 108 is a
pair of opposed crumb plates 114, 116. When the bridge assemblies
106, 108 are brought together, the crumb plates 114, 116 slightly
overlap, thereby forming a temporary "S" shaped constriction in the
flattened film tube. This "S" shaped constriction provides a means
for keeping product out of the transverse seal area while the tube
of film above the constriction is filled with product. Two stripper
bars 118, 120 are also shown attached to the bridge assemblies 106,
108. The stripper bars 118, 120 are typically spring loaded and
provide the stripping function previously described.
[0011] Both of the seal facings 102, 104 are constructed with a
central channel 141, 143 to accommodate a knife or cutting tool
122, best seen in FIG. 1c. This knife 122 is recessed within the
channel 141 of one of the seal facings 102 and held in place by two
knife brackets 124, 126 attached to the bridge assemblies 106, 108.
After the transverse seal has been formed on the flattened film
tube, the knife brackets 124, 126 are rotated slightly, thereby
exposing the knife 122 to the transverse seal. This action cuts the
transverse seal, thereby completing the process of forming,
filling, and sealing a single package.
[0012] The prior art carriage described above is designed such that
the seal facings 102, 104 can be removed in order to install
another set of seal facings that provide for different vertical
widths of the resultant transverse seals. The facing assembly shown
in FIG. 1d is aligned at the factory, and it is not recommended
that the operator remove more than the seal facings 102, 104, crumb
plates 114, 116, and stripper bars 118, 120 from the facing
assembly.
[0013] There can be variations to the specific art described above.
For instance, some machines do not require crumb plates and
stripper bars, although other machines do. Additionally, in many
packaging machines, the facing 102/104 is not a separate,
replaceable part of the jaws, but is integral with the jaws.
[0014] FIG. 2a is a perspective drawing of a prior art bag after
the back seal and bottom seal have been formed as described above.
It will be evident that as the transverse seals are formed, most
sections of the seal have only two layers of material, from the
front and the back of the bag. In the region of the back seal,
however, there will be a total of four layers of material included
in the transverse seal when a fin seal is used, as seen in FIG. 2b,
a cross-section taken at line A-A of FIG. 2a. In general, this
creates differences in the quality of transverse seal achieved in
the different areas of the seal, although operator adjustments can
often be made to compensate for this area of added thickness, as
described below.
[0015] There are three main parameters of the sealing mechanism
that are typically changed to correct improper sealing of a bag:
temperature, pressure, and dwell time (the time the seal jaws are
closed to form the seal). The materials used generally seal within
a given range of temperatures, such as 375-425.degree., although
this range can vary, depending on the accompanying pressure and
dwell time. Of these three variables, the pressure is generally set
at the factory by a mechanic, and is not easily changeable, but the
temperature and dwell time are operator decisions at the time the
product is packaged. The operator will generally be familiar with
the specific materials being used for a package and can vary the
time and temperature parameters as needed to obtain an effective
seal, within the constraints of the situation. One such constraint
is that increasing the temperature past a given range for a
material can result in burning, or melting a hole through the
material. An additional constraint is the effective throughput of a
machine, which can be affected by the dwell time. For instance, if
a seal formed at a given temperature and pressure is not holding
after {fraction (1/10)} of a second, increasing the dwell time of
the sealing mechanism to 1/2 second, or even a second, may
significantly improve the seal, but it may also mean that the
machine can only package a fraction of the product it can handle at
a lower dwell time. A dwell time that requires additional machines
to meet a production schedule is not an economic solution.
[0016] FIG. 3a is a perspective drawing of an alternate style of
bag that the assignee of this patent application has produced. In
this bag style, a deep pleat or gusset is taken in both sides of
the bag. As seen in FIG. 3b, which is a cross-section taken at line
B-B of the bag of FIG. 3a, there are three areas in which more than
two layers of material need to be sealed by the seal facings: each
gusset area will have four layers, while the back seal area will
have three layers, if an overlap seal is used, or four layers, as
shown, if a fin seal is used. Additionally, this bag is made of a
film containing a layer of paper for esthetic reasons, so that the
thickness of the film, about 6 mils, is greater than usual. FIG. 4
shows diagrammatically how the folds of the bag look as the prior
art seal facings are closed on them. In segments A, C, and E, where
four layers of material are present, the seal facings fit snugly
against the bag, providing heat and pressure to create an effective
transverse seal. However, where there are only two layers (sections
B and D), the seal facings bridge the gap, so that an effective
seal is not created. In testing, the improperly sealed bags opened
under the weight of the enclosed product, causing the product to be
lost or contaminated.
[0017] In a related prior application that is commonly owned by the
assignee of this application Ser. No. 09/079,382 filed on May 15,
1998, an area on the seal facing is recessed, or relieved, so that
during the sealing process, no pressure is applied across a
reclosable seal, except at the endpoints. However, unlike the prior
art application, the current application requires that pressure be
applied across the entire seal, in order to properly close the
bag.
[0018] It is thus desirable to have a means of effectively sealing
a bag without slowing the throughput of the machines, even when
extra layers and thicker materials make the sealing more
difficult.
SUMMARY OF THE INVENTION
[0019] In the present invention, the seal facings, or jaws, for the
transverse seal are modified so that they are relieved in the
region(s) where extra layers of material are found. The amount of
relief is approximately equal to the additional thickness of the
extra layers, and is just sufficient so that approximately the same
pressure is provided across the entire sealing area. This
modification improves the sealing for films as thin as 1.5 mils
when a varying number of layers exist across the length of the
seal, especially where several areas of the seal have additional
layers, which increases the likelihood of bridging. The above as
well as additional features and advantages of the present invention
will become apparent in the following written detailed
description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The novel features believed characteristic of the invention
are set forth in the appended claims. The invention itself,
however, as well as a preferred mode of use, further objectives and
advantages thereof, will be best understood by reference to the
following detailed description of illustrative embodiments when
read in conjunction with the accompanying drawings, wherein:
[0021] FIG. 1a is a simplified schematic showing how a lap seal is
formed.
[0022] FIG. 1b is a simplified schematic showing how a fin seal is
formed.
[0023] FIG. 1c is a perspective view in elevation of a prior art
sealing carriage.
[0024] FIG. 1d is a cross-section of a prior art facing
assembly.
[0025] FIG. 2a is a perspective drawing of a bag in the prior art
after the back seal and bottom seal have been formed, but before
the bag is filled or the top sealed.
[0026] FIG. 2b is a cross section of the bag of FIG. 2b at line
A-A.
[0027] FIG. 3a is a perspective drawing of one embodiment of a bag
that can be made using the present invention; the bag is shown
after the back seal and bottom seal have been formed, but before
the bag is filled or the top sealed.
[0028] FIG. 3b is a cross section of the bag of FIG. 3a at line
B-B.
[0029] FIG. 4 is a cross-sectional view of the bag of FIG. 3a as
prior art seal facings are closing on it.
[0030] FIG. 5 is a cross sectional view of the bag of FIG. 3a as
seal facings of the present invention are closing on it.
[0031] FIG. 6a-c show respectively a perspective, a cross-section
through line C-C, and a cross-section through line D-D of the seal
facings of an exemplary embodiment of the invention.
DETAILED DESCRIPTION
[0032] An exemplary embodiment of the invention will now be
discussed. FIG. 5 is a cross sectional view of the bag of FIG. 3a
as seal facings of the present invention are closing on it. In
sections A, C, and E of the bag, the seal facings have been
relieved, so that a more even pressure is applied across the whole
length of the seal. In the embodiment shown, the bag has four
layers of material in sections A, C, and E, due to the gussets and
fin seal, rather than two layers (C would have only three layers if
an overlap seal was used). Each layer is approximately 6 mils
thick, so both the front and rear seal facings have been relieved
by the thickness of one layer of material, or 6 mils, in sections
A, C, and E. Note that the edges of the relief areas do not form
sharp corners, but are beveled approximately 45 degrees to allow
for some slippage in the alignment of the material in the
machine.
[0033] FIG. 6A is a perspective of one of a pair of seal facings.
This seal facing 600 is roughly divided vertically into three
sections, 610, 620, and 630. The topmost section 610 contains holes
by which the seal facing 600 can be bolted to the form, fill, and
seal machine. Section 620 forms the bottom seal for the next bag to
be filled, while section 630 forms the top seal for the last bag
filled. A deeply recessed channel 650 separates these two sealing
sections, providing space for the knife assembly during operation.
In tests using the relieved seals to seal the gusseted bags
discussed, 60% more pressure was applied to the thinner, and
previously weaker, areas of the seal, thus demonstrating the
effectiveness of the contouring.
[0034] In an alternate embodiment all the relief can be taken from
either the front or the back seal facing, while the remaining
facing retains the normal shape. In this embodiment, only the seal
facing that contains the relief needs to be changed out, as long as
the remaining seal facing is of the proper length.
[0035] In further alternate embodiments, the number, location, and
respective depths of the relief areas can be altered to fit new bag
designs without departing from the spirit of the invention.
[0036] While the invention has been particularly shown and
described with reference to a preferred embodiment, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the invention.
* * * * *