CA1060620A

CA1060620A - Forming and cooling extruded profile film

Info

Publication number: CA1060620A
Application number: CA189,969A
Authority: CA
Inventors: Seiichi Yagi
Original assignee: Minigrip Inc
Current assignee: Minigrip Inc
Priority date: 1973-03-13
Filing date: 1974-01-11
Publication date: 1979-08-21
Also published as: FR2221262B1; BE812258A; FR2221262A1; LU69598A1

Abstract

ABSTRACT

A mechanism for continuously making a plastic film with interlocking profiles with an extruding means for forming a continuous length of film with profiles on the surface shaped and sized to releasably interlock. The profiles engage the film after extrusion and a first coolant supply directs coolant onto the female profile and a second subsequently positioned coolant supply directs coolant onto the male profile. In one form successive coolant supplies are provided for each profile with water first directed against a profile and air thereafter directed against said profile.

Description

i The present invention relates to improvements in methods and mechanism for making continuous plastic film bag material having shaped profiles on the surface and more particu-larly to plastic profile and film extruding and cooling mechanisms which are capable of providing a profile sheet with more accurately shaped and sized profiles.
Thin plastic bags having releasably interlocking closures along the top are provided for containing products to be sold, and the bag is reusable for the original product or other products. Such bags have continuously extending shaped plastic flexible fastener profiles along the top which profiles have male and female elements shaped and sized to interlock when pressed together and to separate when forcibly pulled apart. Such bags are manufactured inexpensively from the extrusion of thin plas$ic film having the fastener profiles thereon. Previously fastener profiles have been made separately and attached as separate strips to the film. However, a saving of plas~c is effected if a separate strip for supporting the profile is omitted and the pro- ;
file is integrally attached to the film. In one form the profiles 20- and film are extruded out of the same die opening, and in an- -other form they are separately extruded, but the profiles are immediately attached. In either arrangement difficulties are experienced in that because the film is thinner, it cools more rapidly than the profiles. If uniform controlled cooling of the profiles relative to each other is not achieved, they can shrink nonuniformly so that they will not interengage and interlock wi$h o~
each other. If heat is taken away from one portion of the profile at a nonuniform rate, or at an uncontrolled rate different than another portion, the plastic can wrinkle and shrink so that either or both of the male and female profile distort and refuse to interlock or inter-lock only weakly so that an insecure fastener results.
Also, if uniform controlled cooling can be achieved, the profiles can be accurately extruded to be very small effect-ing a saving of plastic and yet achieving a strong inter-locking profile relationship.

It is accordingly an object of the present invention to provide an extruding and cooling arrangement for mak-ing continuous films for plastic bags having profiles on the surface thereof with a resultant more accurate profile dimension and shape to achieve small profiles with strong interlocking features.

The invention provides the method of continuously .
extruding a profile plastic film, comprising the steps of extruding heated plastic into a continuous length of ~ ~
film with shaped profile means on the surface, cooling :
the film by engagement with a chill surface at the surface of the ilm opposite the profile means, directing a first flow of coolant fluid aganist the profile means at one :~ .

location, and subsequently directing a second flow of cool-ant fluid against the profile means at a second location ~ L~ tj~?~
downstream relative to said first location.
~ here the profile means comprise a female profile at one location on the film and having a groove and a male profile at a second location on the film and having a projection of a size and shape to releasably interlock with the female profile, the method may comprise directing the first coolant fluid at the female profile to remove heat therefrom, and directing the second coolant fluid at the male profile downstream from the first coolant fluid with respect to the direction of film travel, so that the female profile has heat removed therefrom in advance of the male profile.
Where the profile means include a female profile having a groove and having side legs, the method may comprise directing the coolant simultaneously against the inner surfaces of the legs within the groove and also directing coolan' against the outer surfaces of the legs to simultaneously cool the inner and outer surfaces of the female profile.
The method may also comprise providing flange means alongside the profile means, and directing a flow of coolant -against the flange means for removing heat therefrom.
The invention also provides a mechanism for con-tinuously making profile plastic film comprising, in combination, extruding means for extruding heated plastic material into a continuous length of film with shaped profile means on the sur-face, a chill surface positioned to be engaged by the film on thesurface opposite the profila means to remo~e the heat from the film, a first coolant supply means positioned to direct coolant against the profile means at one location, means for supplying coolant to said first coolant supply means, a second coolant supply means positioned at a second location to direct coolant against the profile means in downstream relation to said first ~ -2a-o~
location, and means to direct coolant to said second coolant supply means.
Where the profile means comprise a female profile having a groove and a male profile having a projection of a size and shape to releasably interlock with the female profile, the female profile being located at one location and the male profile being located at a second location, coolant fluid may be directed to the female profile ahead of the directing of coolant to the male profile and thereby assuring substantially equalized cooling of the profiles in the continuous advance of the plastic profile film.
In another aspect of the invention where the profile means are formed as a female profile to be cooled at a first location and a male profile to be cooled at a second location, ~ `
coolant supply means are provided at the first location positioned to direct coolant onto the female profile with the coolant directed to engage the outer surface of the female profile out-side of a groove therein, and also to direct coolant to engage the inner surface of the female profile inside of the groove so as to engage the surfaces on both sides of the groove.
In addition, where the profile means comprise male and `
female profiles, which are interlockable, and with extruded flange strips outwardly of the profiles, coolant supply means may be provided positioned outwardly of at least one of the pro-files and arranged to direct a separate supply of coolant against the flange strip outwardly of said at least one profile.
Other objects, advantages and features will be-come more apparent, as will equivalent structures and methods which are intended to be covered herein, from the teaching of the -2b-,.~,.~ .

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principles of the inven~on in connection with the disclosure of the preferred embodiments thereof in the specification, claims and drawings, in which:
ON THE DRAWINGS
FIGURE 1 is a schematic elevational view of an extruder mechanism constructed and operating in accordance with the principles of the present invention;
FIGURE 2 is a somewhat schematic fragmentary sectional view taken substantially along line II-II of Figure 1;
FIGURE 3 is a fragmentary eleva~onal view taken substantially in the direction indicated by III-III in Figure 2;
FIGURE 4 is a fragmentary schematic plan view illustrating a cooling arrangement;
FIGURE 5 is a schematic sectional view taken sub-stantially along line V-V o~ Figure 4;
FIGURE 6 is an enlarged sectional view taken through a profile illustrating a cooling arrangement; - - -FlGURE 7 is an enlarged sectional view of a profile :-illustrating a cooling arrangement; and FIGURES 8 and 9 are enlarged sectional views taken through female and male pro~iles respectively illustrating cooling arrangements.
DESCRIPI~ION OF THE PREFERRED EMBODIMENTS
.
As shown in Figures 1 and 2, an extruding head 10 25- extrudes fused plastic through an elongate thin slot 11. Simul-taneously, fused plastic is extruded thrc)ugh shaped profile openings ~ . -12 and 13. The profile openings 12 and 13 are interre~ ed in slze and shape so as to respectively provide male'and ' female profiles which will interlock when pressed together and will separate when forcibly pulled apart.
As particularly illustrated in Figure 2, the plastic for the film slot 11 is supplied through a passage~l2b from , a suita~le extruder mechanism. The material for the pro~ '-iles is provided from a preform die'block 15 which,is secured to the film die head 10. Plastic is delivered through lines such as 14 to be'extruded through the open-ings 12 and 13. The profile element 12a in the'fused plastic state is almost immediately engaged with the sur- ~
face of the fused plastic film 16 so that the two fuse - ' together.
The film is engaged on the surface opposite the pro-files with a chill roll'18 so as to remove the heat there-from. Substantially at the time the film engages the chill roll, and slightly in advance'thereof, a jet of coolant is directed against the'female profile 13a by a jet 19.
Downstream from the coolant jet 19, with respect to the direction of traveI of the film 16, is located a coolant jet 20 which directs a flow of coolant against the male'profile 12a. In accordance with the concept herein disclosed, one'profile is cooled in advance'of the other.
In the preferred arrangement, the female'is first cooled. This is because'the'female profile' '~'''.,~ ' .::
,.. ~ , ., 13a has more mass than the male profile 12c, and hence requires a longer cooling period. Also, the female profile has a more complex shape than ;he male profile and, therefore, is more easily distorted. Cooling it sooner reduces the possibility of distortion occurring. The escape of heat from the female ele-ment is slowed somewhat by the groove of the female profile and additionally because of the female profile having separate side legs, there are four lateral surfaces to be cooled, as will be observed from the illustration of Figure 6, which will be described later.
The relationship of the coolant jet 19 for the female element 13a to the coolant jet 20 for the male element 12 is shawn in Figure 3 relative to the direction o~ travel of the film 16, with the direction being shown by the arrowed line 16a. The coolant is preferably water which has a higher spedfic heat trans-fer than air and is, therefore, capable of carrying away the heat of fusion at a greater rate. The water, hawever, is directed against the profiles at a limited velocity so that its impact does not distort the shape of the profiles. The profiles are still relatively soft when hot, and their shape can be changed by the force aE the coolant.
In the arrangement of Figure 4, the profiles are cooled in first and second stages with water coolant being deliver-ed by a first jet 22 at location 26. The flow of water is con-trolled by a valve 24. The film 21 is travelling in the direction indicated by the arrow 21a. Subsequent to the water, air as a ' - 5 - ;

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coolant is delivered by a jet 23 at location 27 with the flaw co~-trolled by the valve 25. With the wa~er firs$ engaging the pro-file 35, the heat is removed therefrom by the water having the higher specific heat transfer, and sufficient cooling takes place to rigidify the plastic so that it has sufficient resistance ~o take the impact of a high velocity flow of coolant air.
The air is delivered through the jet 23 controlled by valve 25. The relationship of the first and second coolant jets 22 and 23 to a chill roll 30 is shown in Figure S. In addition to -10 cooling the profile, the air aids in removing the excess water from ~ -the profile and film so that it is relatively dry and can then be rolled onto rolls. The air jet 23 can also be placed on the opposing side of the chill roll 30 if so desired.
Figures 6 and 7 shaw a third detailed arrangement 15- for coolant jets. While the jets shown in Figures 2 through 5 may be of the form having a single nozzle opening, plural dis-tributed uniquely spaced openings may be provided in the manner shown in Figures 6 and 7.
Figure 6 has nozzles 38, 39 and 40 and 41 provided for cooling the individual legs 33 and 34 of the female profile 31. --The legs 33 and 34 have the groove 32 between them for impeding ~he escape of heat. The jets 39 and 40 are directed into the groove 32 and are angled slightly to cause the coolant to flow against the inner surfaces 33b and 34b of the female pr~ile legs 33 and 34. The ~ets 38 and 41 are positioned and angled so as to direct a flow of coolant ag~inst the outer surfaces 33a and 34a .:

of the legs. The jet arrangement illustrated may be used with either water or air as coolant.
In Figure 7 coolant jets 42 and 43 are angled to engage the outer surfaces 36 and 37 of the male profile 35.
S Additional jets can be installed and directed at the base of the male profile. This effects a more uniform cooling and insures coolant engagement at said base to reduce wrinkling and uneven shrinkage at the location where the profile is fused to the film 44.
10` Other jets 45 and 45a may be used to cool the areas 46 and 47 adjacent the profiles as in Figures 8 and 9. These areas, after the profile sheet has been converted into a bag, become the bag opening lips, which when pulled apart will separ-ate the interlocking profiles. By supplying spedfic cooling jets to these areas, their size 48 and 49, or the lip height when con-verted into bags, can be more readily controlled. These jets 45 and ~5a may be positioned substantially at the same location relative to the axis of the chill roll as either of the jets for -cooling the male or female profiles.
20- In certain extrusion processes, lamina~ed film may be employed so that two layers of film are laid in juxtaposition with each other. This increases the uneven cooling problem, but the present arrangement aids in maintaining the integrity of the shape ~ ~ ;
and size of the profiles. With laminated film, the outer layer of film will engage the chill roll so that the inner layer of film which supports the profiles will have its heat conducted to the chill roll j:
through the outer layer.

7 ~

Claims

Embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. The method of continuouly extruding a profile plastic film, comprising the steps of: extruding heated plastic into a continuous length of film with shaped pro-file means on the surface, cooling the film by engagement with a chill surface at the surface of the film opposite the profile means, directing a first flow of coolant fluid against the profile means at one location, and subsequently directing a second flow of coolant fluid against the profile means at a second location downstream relative to said first location.

2. The method of continuously making a profile plastic film, comprising the steps of: extruding a heated plastic material into a continuous length of film with shaped profile means on the surface comprising a female profile at one location on the film and having a groove and a male profile at a second location on the film and having a projection of a size and shape to releasably inter-lock with the female profile, cooling the film while in engagement with a chill surface on the surface of the film opposite the profile means, directing a first coolant fluid at the female profile to remove heat therefrom, and directing a second coolant fluid at the male profile downstream from the first coolant fluid with respect to the direction of film travel so that the female profile has heat removed there-from in advance of the male profile.

3. The method of continuously extruding a profile plastic film, comprising the steps of:
extruding heated plastic into a continuous length of film with shaped profile means on the surface, cooling the film by engagement with a chill surface at the surface of the film opposite the profile means, directing a first flow of coolant fluid against the profile means at one location, subsequently directing a second flow of coolant fluid against the profile means at a second location downstream relative to said first location, said profile means including a female profile having a groove and having side legs, and directing the coolant simultaneously against the inner surfaces of the legs within the groove and also directing coolant against the outer surfaces of the legs to simultaneously cool the inner and outer surfaces of the female profile.

4. The method of continuously extruding a profile plastic film, comprising the steps of: extruding heated plastic into a continuous length of film with shaped profile means on the surface, cooling the film by engagement with a chill surface at the surface of the film opposite the profile means, directing a first flow of coolant fluid against the profile means at one location, subsequently directing a second flow of coolant fluid against the profile means at a second location downstream relative to said first location, providing flange means alongside the profile means, and directing a flow of coolant against the flange means for removing heat therefrom.

5. A method according to claim 4, wherein said profile means comprise a female profile at said one location and a male profile at said second location, providing said flange means as laterally extending flanges along each of said profiles, and directing coolant flow against both of said flanges for removing the heat therefrom.

6. A method according to claim 1, 3, or 4, wherein the profile means includes a male profile having angled outer surfaces, and directing coolant from separate nozzles respectively towards said surfaces.

7. A method according to claim 1, 2, or 3, com-prising extruding a layer of film and positioning such layer in face-to-face engaging relationship against the surface on the extruded length of film opposite the profile means, engaging said layer of ilm against the chill surface and removing heat from the layer of film and also heat conducted through said layer to the chill surface from the continuous length of film which has the profile means thereon.

8. A method according to claim 1, 2, or 3, com-prising moving the film vertically downwardly away from extruding means, and directing the coolant fluid in an angular direction against the profile means.

9. A method according to claim 1, 4, or 5, which comprises applying said first flow of coolant fluid as liquid coolant and said second flow of coolant fluid as coolant air against the same profile of said profile means.

10. A method according to claim 1, 2, or 3, wherein the profile means comprise a female profile having inner surfaces and outer surfaces, and directing said coolant fluid from means to said inner surfaces and from other nozzle means to said outer surfaces.

11. A method according to claim 1, 2, or 3, wherein the profile means comprise a female profile having inner surfaces and outer surfaces, and directing said coolant fluid from a pair of nozzles to the inner surfaces, and from another pair of nozzles to the outer surfaces of the female profile.

12. A mechanism for continuously making profile plastic film comprising, in combination: extruding means for extrudin heated plastic material into a continuous length of film with shaped profile means on the surface, a chill surface positioned to be engaged by the film on the surface opposite the profile means to remove the heat from the film, a first coolant supply means positioned to direct coolant against the profile means at one location, means for supplying coolant to said first coolant supply means, a second coolant supply means positioned at a second location to direct coolant against the profile means in downstream relation to said first location, and means to direct coolant to said second coolant supply means.

13. A mechanism according to claim 12, comprising directing the coolant, at both of said locations, against one profile of said profile means.

14. A mechanism for continuously making profile plastic film comprising, in combination: extruding means for extruding heated plastic material into a continuous length of film with shaped profile means on the surface, a chill surface positioned to be engaged by the film on the surface opposite the profile means to remove the heat from the film, a first coolant supply means positioned to direct coolant against the profile means at one location, means for supplying coolant to said first coolant supply means, a second coolant supply means positoned at a second location to direct coolant against the profile means in downstream relation to said first location, said profile means comprising a female profile having a groove and a male profile having a projection of a size and shape to releasably interlock with the female profile, said female profile being located at said one location and said male profile being located at said second location, and the directing of coolant to said female profile ahead of said directing of coolant to the male profile assuring substantially equalized cooling of the profiles in the continuous advance of the plastic profile film.

15. A mechanism for continuously making profile plastic film comprising, in combination: extruding means for extruding heated plastic material into a continuous length of film with shaped profile means on the surface, a chill surface positioned to be engaged by the film on the surface opposite the profile means to remove the heat from the film, a first coolant supply means positoned to direct coolant against the profile means at one location, means for supplying coolant to said first coolant supply means, a second coolant supply means positioned at a second location to direct coolant against the profile means in downstream relation to said first location, means to direct coolant to said second coolant supply means, forming said profile means as a female profile to be cooled at said first location and a male profile to be cooled at said second location, and the coolant supply means at said first location positioned to direct coolant onto the female profile with the coolant directed to engage the outer surface of the female profile outside of the groove and to also direct coolant to engage. the inner surface of the female profile inside of the grooves so as to engage the surfaces on both sides of the groove.

16. A mechanism according to claim 12, 14, or 15 wherein the film moves vertically downwardly away from the extruding means and at least one of said coolant supply means directs coolant in an angular direction against the profiles.

17. A mechanism according to claim 12, 14, or 15, wherein at least one of said coolant suppy means includes a plurality of jet openings directing streams of coolant against the same profile of said profile means.

18. A mechanism according to claim 12, 14, or 15, wherein the profile means includes a female profile having legs defining an inner groove with a plurality of surfaces, at least one of said coolant supply means including four jets, with a separate jet directed at each of the outer sur-faces of the legs of the female profile, and with a separate jet for directing a stream of coolant at each of the inner surfaces of the groove.

19. A mechanism according to claim 12, 14, or 15, wherein said chill surface is a cooled rotating roll.

20. A mechanism according to claim 12, 14, or 15, wherein the profile means includes a male profile having divergent outer surfaces, and at least one of the coolant supply means including a plurality of nozzles one of which is directed toward one of said male profile surfaces and another of which nozzles is directed toward the other of said male profile surfaces.

21. A mechanism for continuously making profile plastic film comprising, in combination: extruding means for extruding heated plastic material into a continuous length of film with shaped profile means on the surface, a chill surface positioned to be engaged by the film on the surface opposite the profile means to remove the heat from the film, a first coolant supply means positioned to direct coolant against the profile means at one location, means for supplying coolant to said first coolant supply means, a second coolant supply means positioned at a second location to direct coolant against the profile means in downstream relation to said first location, means to direct coolant to said second coolant supply means, said profile means comprising male and female profiles, which are interlockable and with extruded flange strips outwardly of the profiles, and coolant supply means positioned outwardly of at least one of the profiles and directing a separate supply of coolant against the flange strip outwardly of said one profile.

22. A mechanism according to claim 21, comprising means for directing separate supplies of coolant against both of the flange means.

23. A mechanism according to claim 12, 14, or 15, including second extruding means for extruding a layer of film which is positioned in face-to-face engaging relationship with the first length of film which has the profile means thereon, and said layer of film engaging said chill surface so that heat is removed therefrom and heat is conducted through said layer to the chill surface from the film having said profile means thereon.