NZ193297A

NZ193297A - Plastics closure strip extrusion die

Info

Publication number: NZ193297A
Application number: NZ193297A
Authority: NZ
Inventors: E A Kamp
Original assignee: Union Carbide Corp
Priority date: 1979-03-30
Filing date: 1980-03-28
Publication date: 1984-03-16
Also published as: DK157905C; GB2046660A; GB2046660B; IT1127017B; NL188839C; IE800631L; FI72918B; NL188839B; NL8001859A; FR2452371B1; SE435153B; IT8048276A0; FI72918C; CH636047A5; FR2452371A1; FI800957A; BE882517A; AU540476B2; SE8002384L; DE3011371C2

Description

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NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION "EXTRUDING DIE APPARATUS FOR PRODUCING A PLASTIC CLOSURE STRIP" Xfc/We, UNION CARBIDE CORPORATION, of 270 Park Avenue, New York, State of New York, 10017, United States of America, a Corporation organized under the laws of the State of New York, United States of America hereby declare the invention for which / we pray that a patent may be granted to OJSjius, and the method by which it is to be performed, to be particularly described in and by the following statement: - 193297 H466 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 profile 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.

The closure device described in the coponding U-Z. Tcjtevd speti'-fiWuitv \0)00<T? -patent-application serial no. 892-^432^—firled-March 31,- having the same applicant and accigncc ao the -instant application, is a typical closure device suited for being produced by the ihstant invention. ;• • -42"3<?6 ,1 932 9 7 The prior art method and apparatus for producing a closure strip includes the separate extrusion and forming of profile and base portions and subsequently, joining these portions together. This method has drawbacks and is not suitable for 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 of the profile and base portions as well as a good maintenance of the integrity of the shape of the closure strip. An additional feature is that different plastic material can be used for the profile and base portions.

One embodiment of the invention is an extrusion die apparatus for producing at least one plastic closure strip having profile and base portions, comprising a die body having a die face, at least a first profile channel defined in the die body and communicating with a corresponding first profile die opening in the die face for extruding a first profile portion, and at least a first base channel defined in the die body and communicating with a corresponding first base die opening in the die face for extruding 193297 a first base portion, the first profile and first base channels being adjacent to each other near the first profile and first base die openings and separated by a first portion of the die body which terminates short of the die face so that the extruded first profile portion and first base portion join together 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 profile portion, and a second base channel defined in the die body and 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 die openings and separated by a second portion of the die body which terminates short Df the die face so that the extruded second profile portion and second base portion join together before exiting the die body.

A further embodiment of the invention teaches a plurality of. separate profile channels defined in the die body and communicating with corresponding profile die openings in the die face for extruding separate profile portions, the plurality of profile channels being 4. 1932 9 7 adjacent to the first base channel near the die openings and separated by the first portion of the die body so that the extruded plurality of profile portions join the first base portion before all of the portions exit the die body.

Yet another embodiment of the invention is in the method fac producing at least one plastic closure strip having profile and base portions comprising extruding at least a first profile portion, extruding at least a first base portion, and joining the first profile and first base portions together, the improvement wherein the first profile and first 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 the claims hereof.

Hie invention accordingly comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the i, J 22366" 193297 following detailed description, taken in connection with the accompanying drawings, in which: Fig. 1 shows a cross-sectional view of two closure strips which form a closure device and which are suitable for being produced by the invention; Fig. 2 shows a plastic bag incorporating a closure device as shown in Fig. 1; Fig. 3 shows diagrammatic side elevational view of an extrusion system including an apparatus according to the invention; Fig. 4 is a diagrammatic sectional view of an apparatus according to the invention; Fig. 5 is a diagrammatic partial sectional view showing another embodiment of an apparatus according to the invention; Fig. 6 is a perspective view of a control bar used in Fig. 4; Fig. 7 is a perspective sectional view of another control bar used in Fig. 4; Figs. 8A, 8b, and 8C are sectional views of different control bars; Fig. 9 is a diagrammatic partial sectional view showing another embodiment of a flow diverter-for the apparatus shown in Fig. 4; and 6. ( ) ) ■ 193297 Figs. 10A and 10B 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 in accordance with the aforementioned co-pending patent application serial number 892,432. 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 profile portion 22. The two closure strips 25A 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 extrusion die apparatus for producing the closure strips which constitute closure device 26. 7.

-H3G& 193297 The closure strips of closure device 26 can be made by an extrusion system which includes an extrusion die apparatus in accordance with the invention as shown in Fig. 3. Extruder 27 is connected 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 closure 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, the cooling rate, and the adjustment of the die components producing the closure strips 31 and 32 as well as other factors.

Generally, equipment for extruding plastic material is well-known in the art and considerable prior art exists relevant to the extrusion of closure devices. Fig. 4 shows a partial sectional view of an extrusion die apparatus in accordance with the invention and details such as assembly screws, die heaters, sensing control elements, etc. have been omitted for clarity. The flow diverter 40 establishes the distribution pattern for the plastic material being supplied, plastic"material under pressure is communicated to the channels 41 and 42 and 8. ( ) \ 1 j. 1932 9 7 then through the flow diverter 40. Channel 41 is connected to a control orifice 43 and an adjustable valve control 44 before reaching control bar 46 and die opening 45. The die opening 45 is an outlet and shape controller for a base portion.

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 die opening 52. The die opening 52 is an outlet and shape controller for a closure profile. The die body portion 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 from 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 complementary 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 controller for a profile portion 64 and die opening 66 is an outlet and shape controller for a base portion 67. 1^952 9 7 The profile portion 64 and base portion 67 contact each other and join together before exiting the die body to form closure strip 68. The closure strips 54 and 68 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 84 are shown as being linear, but this is not necessarily the preferred embodiment. Generally, this control land 83 can be either a gentle contour or have steps of different depths. The control land 83 can be straight in the direction determining width and have a variable height so that thickness variations can be controlled. . 193297 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 or removed conveniently.

Fig. 7 shows a sectional perspective 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 communicates with channel 89 which defines the shape of the profile portion. The channel 89 can be formed with good precision through the use of an electro-deposition method in accordance with known technology. The mounting hole 91 permits the mounting and removal of the control bar 87.

Figs. 8a, 8b, and 8c show cross-sectional views of three control bars having profile channels in different locations. Profile bar 92a shows profile channel 93a with die opening 94a spaced apart from the location of where the die opening for the base portion would be so that the base and profile portions join together outside the die body in accordance with the prior 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 exiting the die body because the die body portion 96b is just short of the die face. Control bar 92c includes 11.

C \ \-y 193297 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 from 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 embodiment of a flow diverter. Channel 100 supplies plastic material to one base portion extrusion opening whereas channel 101 communicates with channels 101a, 101b, and 101c 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. 10A and 10B 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 wide base die opening. Cutting base portion 106 between the profile portions 107 and 108 will produce two closure strips. Similar operations on base portion 109 will produce four closure strips. 12. 193297 It is to be understood that there is no desire for the invention to be limited to the exact details of construction 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: 13. 193297

Claims

WHAT WE CLAIM IS:

1. An extrusion die apparatus for producing at least one A J P &S plastics closure strip having profile and base portions, 17. n-*3 OctupristHa /Jjm// oompricofl a die body having a die face with a die opening therein, at least a first profile channel in said die body communicating with a first profile die opening for extruding a first profile portion, and at least a first base channel in said die body communicating with a first base die opening for extruding a first base portion,-the die opening in the die face being defined by part of the first profile die opening and part of the first base die opening which openings lie adjacent one another so that the extruded first profile portion and first base portion join together before exiting said die body at said die opening, the die openings being separated at a location remote from the die face by a first portion of said die body which terminates from 0.0254 cm to 0.635 cm short of said die face.

2. An apparatus as claimed in claim 1, further comprising a second profile channel in said die body and communicating with a second profile die opening for extruding a second profile portion; and a second base channel in said die body and communicating with a second base die opening for extruding a second base portion; wherein a part of said second profile die opening and a part of said second base die opening define a second die opening in said die face, and wherein the second profile and second base die openings lie adjacent one another so that the extruded second profile portion and second base portion join together before exiting said die body at said second die opening, the die openings 1 O 7 O O 7 I J w' L. / 15 - being separated at a location remote from the die face by a second portion of said die body which terminates from 0.0254 cm to 0.635 cm short of said die face.

3. An apparatus as claimed ill claim 2, in which said first profile and first base portions define a first closure strip and said second profile and base portions define a second closure strip, said first and second profiles being adapted to be occluded together whereby said first and second closure strips define a closure device.

4. An apparatus as claimed in,'claims 1, 2 or 3 in which said first portion of said first die body portion terminates from 0.038 cm to 0.229 cm short of said die face. A. J. P. & S. , • S3 ewiws

5. An apparatus as claimed in any of olaimoo 1 to 4, in which the first portion of said die body separates said profile and base channel die openings at said remote location by less than 0.102 cm. /

6. An apparatus as claimed in claim 5, in which the first portion of said die body separates said profile and base channel die openings at said remote location by less than 0.051 cm.

7. An apparatus as claimed in claim 6, in which the first portion of said die body separates said profile and base channel at said remote location by from 0.0051 cm to 0.0204 cm. - 16 - ; !

8. An apparatus as claimed in claim 1 comprising a plurality of separate profile channels in said body and communicating with respective profile die openings for extruding separate profile portions, the plurality of profile die openings lying adjacent the base die opening so that the plurality of profile portions join said first base portion before all of the portions exit said die body, the plurality of profile portions being separated from the base portion at a location remote from the die face by respective said body portions.

9. A method for producing from a die body having a die face with a die opening therein at least .one plastics closure strip having profile and base portions, comprising extruding at least a first profile portion, extruding at least a first base portion, and joining the first profile and first base portions together; wherein the first profile portion and the first base portion are separated by a first portion of the die body which terminates from 0.0254 cm to 0.635 cm short of the die face so that said first profile and first base portions are joined together before exiting said die body.

10. Apparatus as claimed in claim 1 for extruding a'plastics closure strip, substantially as hereinbefore described with reference to the accompanying drawings.

11. A method as claimed in claim 9, for extruding a plastics closure strip, substantially as hereinbefore described with 193297 - 17 - reference to the accompanying drawings.

12. A plastics bag closure device whenever produced by the method or apparatus of any of the preceding claims. DATED THIS DAY OF fGbU - A. J. PARK & SON PER, AGENTS FOR THE APPLICANTS