Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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12366
The present invention relates to an extrusion
die apparatus for producing a plastic closure device
including two closure strips, wherein each closure strip
includes profile and base portions and particularly to an
extrusion die apparatus for producing a plastic closure
strip in which the extruded profile and base portions
` join together before exiting the die body.
Plastic bags including plastic closure devices
are well-known and in popular use. Typically, a plastic
closure device includes two closure strips which interlock
together. Each closure strip includes a profil~ portion
and a base portion.
It is the two complementary profile portions
of two closure strips which become occluded when the
closure device is closed. The integrity of the shapes
of the profile portions must be maintained during the
production of the closure strips so that good occlusion
is obtained. In addition,.the joining together of the
profile and base portions must be done in a manner to
avoid distortions which can interfere with the preferred
shape of the closure strip.
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The prior art method and apparatus f~r
producing a closure strip includes the separate extrusion
and forming of pr~file and base portiDns and subsequently,
joining th~se portions together. This method has
drawbacks and is not suitable fDr commercial high production
of many closure strips. One drawback is that relatively
slow cooling, such as air cooling, is required and
this results in low production rates.
The instant invention overcomes the problems
arising from the prior art method and apparatus. The
invention allows good control of the extrusion 3f the
profile and base portions as well as a good maintenance
of the integrity of the ~hape of the closure strip. An
additional feature is that different plastic mat~rial can
be used for the profile and base portions.
one em'o~diment of the invention is an extrusion
die apparatus for producing at least one plastic closure
strip having profile and base portions, comprising a die
~od~ having a die face, at least a first profile channel
defined in the die body and communicating with a correspond-
ing first profile die opening in the die face for extruding
a first pro:Eile portion, and at least a first b2se channel
defined in the die b~dy andcommunicating with a correspcnd-
ing first base die opening in the die face for extruding
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a first base p~rtion, the first profile and first base
channels being adjacent tD each other near the first
profile and first base die openings and separated by a
first portion of the die bDdy which terminates short ~f
the die face so that the extruded first profile pDrtion
and first base portion join to~ether before exiting the
die body,
Another embodiment of the invention further
includes a second profile channel defined in the die body
and communicating with a corresponding second profile die
opening in the die face for extruding a second pro~ile
portion, and a second base channel defined in the die
bodyand communicating with a corresponding second base
die opening in the die face for extruding a second base
portion~ the second profile and second base channels being
adjacent to each other near the second profile and second
base d~e openings and separated by a second portiDn of the
die body which terminates short of the die face so that
the extruded second profile portion and second base portion
join together before exitin~ the die body.
A further embod~ment of the invention teaches
a plurality of separate profile channels de~ined in the
die body and co~munica~ng with corsesponding profile
die openings in the die face for extruding separate profile
portions, the plurality Df profile channels being
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adjacent to the first base ch~nnel near the die openings
and separated by the first portioR of the die body so
that the extruded plurality Df profile portions join the
first base portion bef3re all of the portions exit the
die body.
Yet another embodiment of the invention is in
the method f~ producing at least one plastic closure strip
having profile and base portions comprising ex~ruding at
least a first profile portion, ex~rudin~ at least a first
base portion, and joining the first profile and first base
portions ~ogether, the improvement wherein the first
profile and ~irst base portions are joined together before
exiting the die body.
Further embodiments and advantages of the
invention will be set forth in part in the following
specification and in part will be obvious therefrom
without being specifically referred to, the same being
realized and attained as pointed out in ~he claims hereof
The invention accord~ngly comprisPs the
features of construction, combination of elements and
arrangement of parts which will be exemplified in the
construction hereina~tar set forth and the scope of the
application of ~hich will be indicated in the claims.
For a ful~er understanding of the natu~e and
objects of the lnvention9 reference should be had to the
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fDllowing detailed description, taken in connection with
the accompanying drawings, in which:
Fig. l shDws a cross-sectional view Qf two
closure strips which form a closure device ~nd which are
suitable for being produced by the inventiDn;
Fig. 2 shows a plastie bag incorporating a
closure device as shown in Fig. l;
Fig. 3 showc diagrammatic side elevatlonal view
of an extrusion system including an apparatus according to
the invention;
Fig. 4 is a diagrammatic sectional view of ~n
apparatus according to the invention;
Fig. 5 is a diagrammatic par~ial sec~ional view
showing another embodiment of an apparatus according to the
inventiDn;
Fig. 6 is a perspective view of a control bar
used in Fig~ 4;
Fig. 7 is a perspective sectional view Df another
control bar used in Fig. 4;
Figs. 8A, 8B, ~nd 8C are sectional views Df
different control bars;
Fig. 9 ;s a diagrammatic partial sectional view
~hvwing another embodiment of a flow diverter-~r he
appara~us shown in Fig. 4; and
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Figs. lOA and lOB each shows a cross-sectional
view of a combined closure strip produced by an apparatus
according to the invention.
In carrying the invention into effect, certain
embodiments have been selected for illustration in the
accompanying drawings and for description in the
specification, reference being had to the Figs. 1 to 10.
Fig. 1 shows a closure device which may be produced
in accordance with the instant invention. The profile portion
20 is joined to a base portion 21 and profile portion 22 is
joined to base portion 23. The profile portions 20 and 22 are
complementary and profile portion 20 can be engaged in the
pro~ile portion 22. The two closure strips 25~ and 25B
constitute a closure device.
Fig. 2 shows a typical plastic bag 24 which includes
a closure device 26. It has been found economical to
produce the two closure strips of the closure device 26
separately and connect them to a film web during the
manufacturing of the bag 24.
Thus, it is desirable to have an economical and
reliable e~trusion die apparatus for producing the closure
strips which constitute closure device 26.
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The closure strips of clDsure device 26 can be
made by an extrusiDn system which includes an extrusi~n
die apparatus in accordance with the inventiDn as shDwn
in Fig. 3. Extruder 27 is cDnnected by a conduit28 to
an extrusion die apparatus 29. Extruded closure strips 31
and 32 are produced by the extrusion die apparatus and
enter a cooling bath 33, such as a container of water and
are then redirected by rollers 34 and 36 to nip rollers 37
where the closure strips 31 and 32 are occluded together
to form a continuous closure device 38. The rate at which
the continuous cl~sure device 38 is produced depends upon
the size and screw speed of the extruder 27, melt flow of
the material, the speed of the nip rollers 37, ~he cooling
rate, and the adjustment of the die componPnts producing
the closure strips 31 and 32 as well as other fact~rs.
Generally, equipment for extruding plastic
material is well-known in the art and considerable prior
ar~ exis~s relevant to the extrusion of closure devices.
Fi~. 4 shows a partial sectional view of an extrusion
die apparatus in accordance with ~he inventi~n and details
such as assembly screws, die heaters, sensing e~ntrDl
elements, etc. have bee~ omitted for clari~y. The flow
diverter 40 establishes the distribution pattern for the
plastic material being supplied. PlastiC~mat2rial under
pressure is communicated ~o the channels 41 and 42 and
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then through the flow diverter 40. Channel 41 is
cDnnected to a contrvl orifice 43 and an adjustable
valve control 44 before reach;ng contrDl bar 46 and
die opening 45. The die opening 45 is an Dutlet and
shape controller for a base portiDn.
The channel 42 is connected to channels 42A,
42b and 42c. The channel 42a goes through a control
orifice 48 and an adjustable valve control 49 before
reaching control bar 51 and di~ opening 52. The die
opening 52 is an outlet and shape controller for a
closure profile. The die body portiDn 47 between the
channels 41 and 42a terminates short of the face of the
die body so that the profile and base portions contact
each other and join together before exiting frDM the die
body to form a closure strip 54.
The apparatus shown in Fig. 4 includes a part
for producing another closure strip 68 which is comple-
mentary to the closure strip 54.
The channels 42b and 42c pass through control
orifices 56 and 57 and adjustable valve controls 58 and 59
and eventually reach control bars 61 and 62. Die opening
63 is an outlet and shape contrDller fDr a profile por~ion
64 and die opening 66 is an outlet and shape controller for
a base portion 67. --
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The profile portion 64 and base portion 67
contact each other and join together befDre exiting
the die body tD form closure strip 68 The closure
strips 54 and ~8 enter a water bath 69 for cooling the
plastic material.
Fig. 5 shows, in part, another embodiment for
the extrusion of closure strips. For the embodiment in
Fig. 5, the closure strips are reversed as compared to
the embodiment shown in Fig. 4. That is, profiles 70
and 71 face each other while the base portions 72 and 73
are on the outside of the closure strips 74 and 76. The
difference in the arrangement shown between Fig. 4 and 5
can be achieved by the choice of arrangement of the control
bars 46, 51, 61 and 62.
Fig. 6 shows a typical control bar 81 for
producing a base portion of a closure strip. A lead-in
taper 82, control "land" 83, and recess 84 are factors
determining the size and shape of the extruded material.
The control land 83 and recess ~4 are shDwn as being
linear, but this is not necessarily the pre~erred
embodiment. Generally~ the control land 83 can be
either a gentle contour ~x have s~ps of different
depths The control land 83 can bP straight in the
dir~ction determining width and havP a variable height
so that thickness variations can be contrDlled.
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The width of the control land 83 depends upon
the width of the base portion desired. Mounting holes 86
allow the control bar 81 to be mounted Dr removed
conveniently.
Fig. 7 shows a sectional perspectivP view of a
control bar 87 for producing a profile portion of a
closure strip. A counter bore 88 communicates with a
plastic material being supplied under pressure and also
co~municates with channel 89 which defines the shape
of the prDfile portion. The channel 89 can be formed with
goo~ precision through the use of an electrodeposition
method in accordance with ~no~n technology. The mounting
hole 91 permits the mounting ind removal of the
control bar 87.
Figs. 8A, 8~, and 8C show cross-sec~ional views
of three control bars having profile channels in different
locations. Profile bar 92A shows profile channel 93A
with die opening 94A spaced apar~ from the location of where
the diP npening for the base portion would be Sb that the
base and profile portions join together outside the die
body in accordance with the pri~r art. Control bar 92B
shows profile channel 93B having a die opening 94B which
will produce base and profile portions which will
join together just before exi~ing the die body
because the die body portion 96B is just short
of the die ~ace. Control bar 92C includes
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a profile channel 93C and a die opening 94C and features
a die body portion 96C which is recessed from about 0.010
inch to about 0.250 inch away fxom the face 97C, preferably
from about 0.015 inch to about 0.09 inch. The separation
between the profile and base channels at the die openings
is less than 0.040 inch and preferably about 0.020 inch
and more preferably yet from about 0.002 inch to about
0.008 inch. The profile and base portions produced will
join together before exiting the die body. The control
bar 92C can be used advantageously with a low draw ratio
of about 1:4, a high operating speed of about 300 feet per
minute, and rapid cooling means such as a water bath.
Cooling can also be established by liquid spray or other
known ways.
Fig. 9 shows a partial sectional view of another
en~odiment of a flow diverter. Channel 100 supplies
plastic material to one base portion extrusion opening
whereas channel 101 communicates with channels lOla, lOlb,
and lOlc for forming two profile portions as well as one
base portion. This arrangement permits the selection of
one of the portions as being a different color or
composition from the other portions.
Figs. lOA and lOB show two intermediate products
which can be extruded from an extrusion die apparatus
according to the invention by positioning two profile die
openings near a wida ~ase die opening. Cutting base
portion 106 ~etween the profile portions lU7 and 108 will
produce two closure strips. Similar operations on base
portion 109 will produce four closure strips.
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It is to be understood that there is no desire
for the invention to be limited to the exact details of
constructlon shown and described, for obvious modifications
will occur to a person skilled in the art.
Having thus described the invention, what is
claimed as new and desired to be secured by Letters Patent
is as follows:
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