NZ202072A

NZ202072A - Heat sealing of gathered necks of plastics containers using radiant heat

Info

Publication number: NZ202072A
Application number: NZ202072A
Authority: NZ
Inventors: G C Gianelli
Original assignee: Grace W R & Co
Priority date: 1981-10-06
Filing date: 1982-10-04
Publication date: 1985-07-31
Also published as: IT1139497B; DK442482A; BR8205796A; GB2110592B; CH652087A5; MX157688A; AU8911982A; GB2110592A; JPS5873524A; FR2513967B1; IT8124350A0; FR2513967A1; ZA827275B; DE3236519A1; AU549613B2

Description

t # 2020721 Priority Datefs): k. lR~. f.\ Complete Specification Filed: V.'.T'.??- Class: . ® • • • • • • ? ■ ;•••' ^ 31 JUL 198S Publtoation Date: P.a JotimoJ, No: LltfZ NEW ZEALAND PATENTS ACT, 1953 No: Date: COMPLETE SPECIFICATION METHOD AND APPARATUS FOR SEALING PACKS We, W. R. GRACE & CO., a corporation organized and existing under the laws of the State of Connecticut, United States of America, of 1114 Avenue of the Americas, New York, New York 10036, United States of America hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by page -la-) 202072 - la- DESCRIPTION "METHOD AND APPARATUS FOR SEALINS--PACKS-" The present invention relates to a method of and apparatus for sealing packs, and more particularly for sealing packs comprising one or more product articles within a flexible packaging container of plastics material, by the application of radiant heat.

The use of radiant heat for sealing flexible packaging containers is known from U.S. Patent No. 3,330,716 (S. ZELNICK) where two sets of clamping bars hold superimposed panels of plastics material while ♦ the application of radiant heat along a gap between the pairs of clamping bars causes burning and fusion of the plastics material at each pair of clamping bars. Each of the two simultaneously sealed finished packages has a flat seal running the full width of the container; for example in the case where the panels are the opposed walls of a plastics bag or pouch, the seal runs from one side edge to the other. A similar arrangement is disclosed in U.S. Patent No. 3,477,194 (L. CORRSIN).

It is an object of the present invention to provide a radiant heat sealing system in the case of a pack formed using a packaging container with a neck which is gathered upon closing (as is particularly suitable where the product article or articles are tall and where the flat seal formed using the teachings of U.S. Patents Nos. 3,330,716 and 3,477,194 will be unsuitable).

Accordingly, the present invention provides, a process of packaging at least one product article in a flexible container, comprising loading the or each product article in the container, and subjecting / 202072 an opening of the container to pressure and heat to seal the container opening, characterised in that the heat is applied to the container opening by radiant heating means before the application of pressure to 5 the container opening, and in that the application of pressure to the container opening comprises a gathering action of gathering means after the material of the container has been heat-softened and so the container opening will be caused to adopt and retain, 10 in a permanent manner, the gathered configuration imparted to it by the gathering means.

A further aspect of the present invention provides apparatus for packaging at least one product article in a flexible container, comprising means for 15 applying heat and pressure to an opening of such a flexible container for closing the container in a permanent manner, characterised in that the means for applying heat comprise radiant heating means emitting heat radiation to soften the mouth region 20 of such container: in that the means for applying pressure comprise a gathering mechanism for gathering the mouth region of the container between a relatively open configuration where the container mouth is clo&e to the radiant heating means, and a fully gathered 25 configuration in which the container mouth is closed off by the gathering; and in that programming means are provided for ensuring operation of the gathering mechanism after operation of the radiant heating means to effect substantial heat-softening of such a container. 30 The above-mentioned process and apparatus enable the gathered pack to be sealed using radiant heating, but do so in a particularly convenient system in that the heat may be applied to the flexible packaging container during the final stages of evacuation 35 in a vacuum chamber. Thus preferably the apparatus 2020?2 includes a vacuum chamber enclosing the radiant heat-emitting means and the gathering means, and the process preferably includes the step of carrying out the radiant heating operation and the gathering operation within 5 a vacuum chamber.

Because the pressure is applied to an already heat-softened portion of the container, it is possible for printing, such as a Trade Mark or a description of the contents, or the packaging date, or the identity 10 of the packaging station, to be applied to the container during the pressure applying operation.

A further aspect of the present invention provides a pack comprising a flexible packaging container enclosing at least one product article, the packaging 15 container having a gathered opening region closed in an air-tight manner, characterised in that the gathered container opening has been heat-sealed by fusion of the container wall to perform heat sealing of the % gathered wall without the application of any external 20 enclosure such as a clip or a sealing tie to the gathered neck.

In order that the present invention may more readily be understood the following description is given, merely by way of example, with reference to 25 the accompanying drawing in which:- Figure 1 is a horizontal sectional view, taken on the line I-I of Figure 3, showing a product article and plastic bag within a vacuum chamber incorporating the apparatus in accordance with the 30 present invention; Figure 2 is a view similar to Figure 1 (i.e. taken on the lines II-II of Figure 4) but showing the. bag after gathering of its neck; Figure 3 is a schematic frontal view of 35 the chamber in the Figure 1 configuration, and showing r i' ' / v - - 4 -; the gathering means open to receive the bag neck before gathering and pressing; Figure 4 is a view similar to Figure 3 but showing the chamber in the Figure 2.. configurationr - and Figure 5 shows a typical bag neck sealed by the apparatus of Figures 1 to 4.

The | vacuum-chamber Lis defined by a chamber cover 2a and a chamber base 2b (Figures ~3 and 4) which enclose the product article 3 and "the bag 4." At the mouth region 4a of the bag the bag, material fits between upper and lower radiant heat-emitting infra-red lamps 5a and 5b, respectively, and between^-upper and lower pressing bars 6a and 6b, respectively. Between the vertical plane defined by the median axes of the_two lamps 5a and J5b, and that defined by the median axes of the pressing bars 6a and 6b is a gathering mechanism comprising gathering arms 8a and 8b projecting upwardly through a slot 7.

As can be seen from Figure 3, the gathering arms 8a and 8b are each pivoted at one end and have at their other ends inturned finger portions 8a', 8bwhich commence the gathering operation. „ - -- The operation of the device illustrated in Figures 1 and 3 can best be described with reference to a specific example of product and packaging container.

A product article 3 comprising uncooked meat, in this case a fresh chicken, is loaded into the bag 4 at a preceding station by means of a bag loader which pneumatically inflates the bag and holds the bag neck open for the chicken to be driven into the bag. Such a bag loader is disclosed in New Zealand Patent Specification Nos 153014, 153015 and 163198. The action of driving the chicken 3 into the bag 4 at the loader moves the bag 4 away from the loading region and can be used to drive it forwardly (closed-end leading) into the vacuum chamber 2 illustrated in Figure 1. ?* o /' -i . . ;'\t •it4rEBI985';" 2020^ When the chicken arrives in the position shown in Figure 1 (i.e. having just passed the vertical plane defined by the median axes of the lamps 5a and 5b), further movement ceases and the chamber is then 5 closed by lowering of the chamber cover 2a onto the chamber base 2b. The configuration at the end of this chamber closing operation is shown in Figure 3 where the upper pressing bar 6a is still raised clear of the lower pressing bar 6b, but nevertheless the 10 chamber cover 2a is fully closed and sealed onto the chamber base 2b and vacuum can be applied to the interior space 1 of the chamber to draw the air between the chicken 3 and the bag 4 out through the neck orifice 9 of the bag mouth 4a.

The bag is formed of a laminate comprising several different packaging film materials chosen for separate desired properties. For example, one of the layers is chosen for particularly good oxygen-barrier characteristics to prevent ingress of oxygen into the 20 pack after sealing (one suitable such barrier material is polyvinyl chloride), and at least one further layer is chosen for its heat-sealing properties (one suitable such heat-sealable layer is a copolymer of ethylene-vinyl acetate which is particularly conveniently 25 heated by the application of radiant heat at a wavelength of from 3 to 4 microns). Thus, towards the end of the evacuation step, while vacuum is still drawing gas through the mouth .orifice 9 of the gathered bag neck, radiant heat begins to be applied by both 30 the upper and lower radiant heat lamps 5a and 5b to heat-soften the bag mouth. At the end of the evacuation step, carefully chosen to coincide with the end of the radiant heating step, the gathering action is effected by lowering of the upper pressing bar 6 35 and simultaneous inward pivoting of the gathering arms, 20207 (i.e. clockwise pivoting of the lefthand gathering arm 8a and anti-clockwise pivoting of the righthand-gathering arm 8b) preferably cam driven by the drive means closing together the upper and lower pressing 5 bars 6ei and 6b. This causes the two gathering arms 8a and 8b to arrive at the fully gathered (Figure 4) configuration at substantially the same time as the two pressing bars 6a and 6b have closed to.the Figure 4 configuration where they apply vertical 10 pressure on the gathered bag mouth 9* to effect final closing. However, the gathering and pressing actions may if desired occur consecutively.

The duration of the radiant heating step preferably comprises 2 to 6 seconds. 15 The above conditions will provide adequate heating of the bag mouth 4a for the gathered and pressed mouth to adopt a permanently sealed configuration with a particularly tidy appearance at the mouth. However, where the shape of the product 20 article 3 demands further tidying, a shrinking step may be carried out by arranging for the flexible plastic material of the bag to include at least one layer which has been cross-linked by irradiation and • subsequently bi-axially oriented by stretching, so 25 that the subsequent application of heat by any suitable. means (for example by blowing hot air over the exterior of the bag 4 or by radiant heating) will effect a shrink-tidying operation before or during evacuation.

It will of course be understood that the 30 means for closing the chamber cover 2a onto the chamber base 2b,,and the means 10 and 11 for lowering the upper pressing bar 6a and raising the lower pressing bar 6b are separate but operated by a common programming means to ensure that the chamber cover 35 - 2a closes onto the chamber base 2b before any substantial £02 closing together of the two pressing bars 6a and 6b so that adequate evacuation through the bag mouth orifice 9 can take place after closing of the chamber cover 2a onto the chamber base 2b but well before the 5 attainment of the final gathered and pressed configuration illustrated in Figure 4.

After gathering and pressing have been completed, or during the final stages of the pressing action, excess bag neck material may be removed by lO operation of a trimming knife (not shown).

The resultant pack, with or without the shrinking operation described above, provides a particularly pleasing appearance and has a gathered seal which does- not need the conventional closing clip or tape 15 and which can be enhanced by the application of printing to the heat softened gathered neck material. As shown in Figure 5, the sealed mouth 20 bears printing 21 which may indicate the date of packaging, or the identity of the packaging stations, or a Trade Mark of the packaging 20 operation, or any other information may be printed, for example information indicative of the product contents. The seal also has a hole 22 punched therein to enable the pack to be hung on a display bar.

The packaging operation is completed by 25 separation of the pressing bars 6a and 6b in the vertical direction and opening of the gathering arms 8a and 8b by pivoting about their pivot axes 13, when the -chamber cover 2a is raised. This opening of the gathering and pressing mechanism may occur simultaneously with opening of the 30 chamber, or just ahead of the chamber opening (i.e. in the reverse sequence from that used during chamber closing and bag gathering).

Finally the sealed pack 12 (Figure 2) is removed from the chamber 1 and a subsequent bag 4 with 35 its chicken 3 therein is loaded into the same chamber for evacuation and sealing. *2.0^^ It is not essential for the process and apparatus of the present invention to involve the use of a vacuum chamber, but this is where a particularly significant commercial advantage of the process and 5 apparatus can be achieved in that'the radiant heating step can be carried out while the hag mouth is being evacuated. > Likewise it is not essential to use a two stage gathering and pressing operation. Gathering 10 may alone provide sufficient pressure on the preheated bag material to close off the mouth in which case the pressing bars 6^a and 6b may be superfluous.

It is not essential for the gathering mechanism to be in the form of pivoting arms. For 15 example, it is conceivable for the gathering mechanism to employ upstanding gathering studs which move laterally inwardly along the line of the lower pressing bar 6b so that gathering may be carried out by a two-stage operation of the pressing bars 6a and 6b 20 with the two stages of operation separated by the closing operation of the gathering studs. Initial partial closing of the two pressing bars 6a and 6b gathers the bag mouth into a relatively loose slot ' configuration. Then, while the pressing bars 6a and 25 6b are substantially stationary, the gathering studs (not shown) move towards one another (i.e. inwardly towards the centre of the lower pressing bar 6b) to close up the slot-like configuration of the bag mouth 4a to a bunched neck configuration. Finally, 30 the upper and lower pressing bars 6a and 6b complete their closing operation to effect the heat seal.

During this gathering operation (or at least during the initial partial closing of the pressing bars 6) the final stages of the evacuation operation can be 35 carried out and heat may still be applied by way of the lamps 5a and 5b.

The lamps 5a and 5b are preferably pulsed to give a relatively short high intensity heat pulse which ceases during the final stages of the gathering operation so that there is no question of applying 5 radiant heat to the inwardly moving gathering arms 8a and 81d of Figure 3 or the gathering studs of the alternative embodiment. By having relatively cool gathering means contact the heated bag mouth, sticking of the bag material to the gathering means can be kept 10 to a minimum.

The finished seal is capable of withstanding prolonged exposure to atmospheric pressure without any leakage of air through the seal to the evacuated interior of the bag over prolonged periods (several 15 months) of storage. In effect, the oxygen-barrier characteristics of the seal are no less than those of the oxygen-barrier layer of the packaging container (in this case the bag 4).

Although not shown in the drawings, some 20 screening mechanism may be employed around the lamps 5a and 5b to ensure that there is no possibility of the bag material at the mouth 4a contacting the hot infra-red lamps 5.a and 5b causing burning and puncturing of the bag. As can be seen, the infra-red 25 lamps 5a and 5b maintain a substantially constant spacing once the chamber cover 2a has closed onto the chamber base 2b, so the time when contact of the bag material with the lamps is most likely is during the early stages of the gathering operation. 30 If desired, the process may include the step of choosing'a bag material having pre-printing of radiation-absorbent material to the bag mouth region in order to enhance the uptake of radiant heat by the bag mouth region. 202072 - lO - The sealed bag mouth 20 shov/n in Figure 5 has ribbing 23 formed by use of ribbed pressing bars 6ji, 6b. However, any other surface configuration (for example a flat seal or a criss-cross ribbed seal) may instead be formed.

Claims

2C2G72 - li - WHAT VWE CLAIM IS i

1. A process of packaging at least one product article in a flexible container, comprising loading the or each product article in the container, and subjecting an opening of the container to pressure and heat to seal the container opening, characterised in that the heat is applied to the container opening by radiant heating means before the application of pressure to the container opening, and in that the application of pressure to the container opening comprises a gathering action of gathering means I after the material of the container has been heat-softened and so the container opening will be caused to adopt and retain, in a permanent manner, the gathered configuration imparted to it by the gathering means.

2. A process according to claim 1, characterised in that the application of pressure further comprises a pressing action of pressing means once the gathering of the heated bag mouth has been completed.

3. A process according to claim 2, characterised the step of applying printing to the gathered container opening during operation of the pressing means. |

4. A process according to claim 1, 2 or 3, characterised in that the heating and gathering operations are carried out within a vacuum chamber and while the interior of the container is being subjected to vacuum.

5. A process according to claim 4, characterised in that the application of heat by the heating means 5 occurs during the final stages of the evacuation of the chamber and the interior of the flexible container. 202C72 - 12 -

6. A process according to any one of the _ preceding claims, characterised in that the radiant he"at applied has a wavelength of 3 to 4 microns..

7. A process according to any one of .the preceding claims, characterised in that the packaging container is formed of a laminate of polyvinyl chloride and an ethylene-vinyl acetate copolymer.

8. A process according to any one of" the preceding claims, characterised in that the energisation of the radiant heating means is of short duration and the radiant heating means i are de-energised before completion of the gathering operation. '

9. Apparatus for packaging at least one product article in a flexible container, comprising means for applying heat and pressure to an opening of such a flexible container for closing the container -• - *;in a permanent manner, characterised in- that the means for applying heat comprise radiant heating means for emitting heat radiation to soften the mouth region of such container; in that the means for applying pressure comprise a gathering mechanism for gathering the mouth region of the container between a relatively open configuration where the container mouth is close to the radiant heating means, and a fully gathered configuration in which the container mouth is closed off by the gathering; and in that programming means are provided for ensuring operation of the gathering mechanism j after operation of the radiant heating means |to effect substantial heat-softening of such a container.;

10. Apparatus according to claim 9, characterised in that the means for applying pressure to the container opening further include pressing means i^or pressing the heat-softened container opening after gathering.;■ f.UFEBBWy;- 13 -;

11. Apparatus according to claim 9 or claim 10, characterised by a vacuum chamber enclosing the radiant heating means ,and the gathering means. ';

12. A pack comprising a flexible packaging container enclosing at least one product article, the packaging container having a gathered opening region closed in an air-tight manner, characterised in that the gathered container opening has been heat-sealed by fusion of the container wall to perform heat sealing of the gathered wall without the application of any external enclosure such as a clip or a sealing tie to the gathered neck.;

13. A pack according to claim 12, characterised in that the heat fusion has been performed by preheating the opening region of the container j and subsequently pressing a part ; of the preheated opening region to achieve the seal.;

14. A pack according to claim 12 or 13, characterised by printing on the exterior of the pressed, gathered opening.;

15. A pack according to claim 12, 13 or 14, characterised by a hole formed in the heat-sealed opening region to facilitate suspension of the pack for display.;

16. A process of packaging at least one product article in a flexible container substantially as hereinbefore described with reference to the accompanying drawings.;

17. Apparatus for producing at least one product article in a flexible container substantially as hereinbefore described with reference to the accomp- • anying drawings. oated Tfyts day op ^;A. J. PARK & SON;PER;AGENTS FOR THE APPLICANTS^;\;y'i . V/l ri4FEB1985w;\ * -