IE49435B1

IE49435B1 - Apparatus and method for producing a plastics closure strip

Info

Publication number: IE49435B1
Application number: IE631/80A
Authority: IE
Original assignee: Union Carbide Corp
Priority date: 1979-03-30
Filing date: 1980-03-27
Publication date: 1985-10-02
Also published as: AU540476B2; NO800864L; DK157905B; FI800957A; IE800631L; CH636047A5; FI72918B; SE435153B; NL188839C; FR2452371A1; NO154160B; SE8002384L; GB2046660B; BE882517A; DE3011371A1; NL188839B; NL8001859A; FI72918C; IT8048276A0; NO154160C

Abstract

A pair of plastics closure strips for use in a bag, each comprises one of interengageable male and female closure profile portions (20, 22) on one of base portions (21, 23), which are simultaneously extruded from a die body having profile channels (42a, 42c) (communicating with die profile outlet openings (52, 63) for extruding the profile portions, and base channels (43, 42b) communicating with die face outlet openings (45, 66) for extruding the base portions. The channels are adjacent to each other near the die openings and separated by a portion of the die body which terminates short of the outlet face of the die, so that the extruded profile and base portions join together before exiting the die body. The portions may be of different plastics materials. Each channel has a control orifice (56, 57, 43, 48) and an adjustable valve control (58, 59, 44, 49). The profile portions may be extruded from the die in facing relationship.

Description

The present invention relates to a method in and an extrusion die apparatus for producing a plastics closure device including two closure strips, wherein each closure strip includes profile and base portions, and particularly to a method and an extrusion die apparatus for producing a plastics closure strip in which the extruded profile and base portions join together before exiting the die body. The invention also relates to a plastics closure whenever produced by the apparatus and method.

Plastics bags including plastics 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. - 2 4943 5 The closure device described in British Patent Specification No. 892,432, having the same applicant and assignee as the instant application is a typical closure device suited for being produced by the instant invention.

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-rate 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 attempts to overcome 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 plastics material can be used for the profile and base portions.

According to one aspect of the present invention there is provided an extrusion die apparatus for producing at least one plastics closure strip having profile and base portions, comprises 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. - 3 49435 According to another embodiment of the invention there is provided 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 a 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 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.

According to a further embodiment of the invention there is provided 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.

According to another aspect of the present invention there is provided 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 - 4 4943« of the die face so that said first profile and first base portions are joined together before exiting said die body.

For a fuller understanding of the nature and objects of the invention, reference should be had to the 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 plastics bag incorporating a closure device as shown in Fig. 1; Fig. 3 shows a diagrammatic side elevational view of an extrusion system 10 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; ,c 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; Fig. 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 ? 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 - 5 49435 specification, reference being had to the Figs. 1 to 10.

Fig. 1 shows a closure device in accordance with the aforementioned British Patent Specification No. 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 POftlQn/Ρ engaged in the profile portion 22. The two closure strips 2§ft apd 25B constitute a closure device. , ·. i ' Fig. 2 shows a typical plastic bag 24 which includes 4 clppure tleylce .26, It has been found economical to produce the two elpsure--StFl|5$ 0f the?' ‘ - * . Λ - - * -closure device 26 separately and connect them to a film $$ dHp’jng 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.

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 conduit 28 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 plastics material is well-known in the art and considerable prior art exists relevant to the extrusion, of closure devices. - 6 ‘ 48435 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 plastics material being supplied. Plastics material under pressure is directed into the channels 41 and 42 and 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 2Q 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.

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 enter a water bath 69 for cooling the plastic material.

Fig. 5 shows, in part, another embodiment for the extrusion of closure strips. - 7 49435 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 Fig. 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, the 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.

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 receives the plastics material being supplied under pressure and it 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 - 8 49435 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 a profile channel 93C and a die opening 94C and features a die body portion 96C which is recessed from 0.010 inch (0.0254 cm) to 0.250 inch (0.635 cm) away from the face 97C, preferably from 0.015 inch (0.038 cm) to 0.09 inch (0.229 cm). The separation between the profile and base channels at the die openings is less than 0.040 inch (0.102 cm) and preferably less than 0.020 inch (0.051 cm) and more preferably yet from 0.002 inch (0.0051 cm) to 0.008 inch (0.024 cm). 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 15 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 plastics material to one base portion extrusion opening whereas channel 101 communicates with channels 101a, 101b, and 101c for forming 2Q two profile portions as well as one base portion. This arrangement permits the selection of one of the portions as being a different colour 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. - 9 48435 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.

Claims

1. CLAIMS ' ‘ ‘

1. An extrusion die apparatus for producing at least one p]astl‘cs 'Closure strip having profile and base portions, comprises a die body living a die face witji a die opening therein, at least a first profile chapnel ty (JIS £>pdy communicating with a first profile die opening for extruding a f|fSt profile portion, and at least a first base channel in's&id die bOSty UpliiniHnig3$1pg w|th ' a first base die opening for extruding a firsVbaee PPFt'ffin» fjld 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 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. - 10 48435

3. An apparatus as claimed in 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 die body portion terminates from 0.038 cm to 0.229 cm short of said die face.

5. An apparatus as claimed in any of Claims 1 to 4, in which wherein the separation between said profile and base channel die openings at said remote locations is less than 0.102 cm.

6. An apparatus as claimed in Claim 5, in which the separation between said profile and base channel die openings at said remote location is less than 0.051 cm.

7. An apparatus as claimed in Claim 6, in which the separation between said profile and base channel at said remote location is from 0.0051 cm to 0.0204 cm.

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 openings 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 - 11 49435 together; wherein the first profile portion and the first base portion are separated by a first portion of the die body which terminates from Q.Q254 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 plastjps c]p§wre§^r1p, substantially as hereinbefore described with reference Jo the accoippanying drawings. ·. ' :

11. A method as claimed in Claim 9, for expruding a plas£ic§ clpjpre substantially as hereinbefore described with reference' to. tjie accbippen^jpg 5q drawings.

12. A plastics bag closure device whenever produced by the method or apparatus of any of the preceding claims.