IE893462A1 - Improved gas venting means for plastic bags - Google Patents

Description

IMPROVED GAS VENTING MEANS FOR PLASTIC BAGS This invention relates to improved packaging means for the packaging of vegetable matter such as lucerne haylage, for preserving as animal feed and more particularly to a plastics bag (being impervious to air) which incorporates an improved . venting means for-permitting the escape of gases which are released by the vegetable matter as it ferments within the bag. The invention is also directed to a method of packaging vegetable matter in a plastics bag.

It is of course well known to store vegetable matter such 10. as silage and haylage in low density polythene bags, the polythene being used on account of its toughness. However, one of the main problems with such form of packaging is the requirement to puncture the bag so as to release the build-up ι of gases therewithin, following which the puncture must be . resealed - usually by means of an adhesive tape. Bearing in mind that the fermentation process is likely to continue for a significant period, the need to have to repeat the puncturing/ re-sealing procedure is extremely inconvenient or if it is not done, there is the danger of gas pressure build-up in the bag.

. Furthermore polythene is not impervious to air and the ingress of air/gas through the bag wall will cause degradation of the material packed therein.

It is also known to package silage by forming cylindrical or round bales and wrapping same up with plastics stretch film, . such an arrangement permitting the gases to escape through the lap seams between tbe layers of plastics film.

It is the main object of the present invention to provide an improved form of packaging for vegetable matter such as lucerne haylage which incorporates a venting means integrally -lfl formed therewith, a portion of the bag itself being used to form the venting means.

It is a further object of the present invention to provide an improved venting means for a plastics bag for storing . fermenting vegetable matter such as lucerne haylage which will allow gases at low pressure to escape from the interior of the bag but also substantially prevent the ingress of air/oxygen into the interior of the bag - it being appreciated that the admission of any appreciable air/oxygen into the interior of . the bag causes oxygen contamination of the vegetable matter in the form of mould (which, of course, renders the animal feed unusable).

In its broadest form, the present invention provides a flexible walled bag of synthetic plastics film material which . is impervious to air, said bag comprising a pair of opposed walls forming an enclosure for receiving material therein, and integrally formed venting means adjacent one of the margins of the bag, said venting means comprising a relatively narrow airflow or venting passageway formed between opposed wall . portions of said walls, there being a first opening for placing said passageway in gas flow communication with the interior of the bag, and a second opening remote from the first opening for placing the passageway in gas flow communication with the atmosphere, whereby gases in the bag interior are able to . escape to atmosphere via the venting passageway but the ingress of air/oxygen from atmosphere is inhibited by virtue of the sealing effect created by the drawing together of the contiguous surfaces of the opposed wall portions when the bag interior pressure is sub-atmospheric.

Preferably, the venting passageway is elongate and formed by two spaced apart weld lines extending across and fusing together said opposed walls and parallel to said one margin.

In a preferred form of this invention, the weld lines form 5. bead seals which seal the passageway uninterruptedly along its margins, the bead seals being substantially parallel to one another and to a transverse margin of the bag.

Preferably, one end of one of the bead seals terminates a short distance from one side of the bag, its other end . terminating at the other side of the bag, whilst the other bead seal terminates at the other side of the bag but short of said one side of the bag, to thereby form two openings at opposite sides of the bag interiorly thereof, one of the openings placing the venting passageway in gas flow communication with . the atmosphere, the other opening placing the passageway in gas flow communication with the interior of the bag.

In another arrangement, the outer bead seal extends uninterruptedly across the bag and terminates at each side thereof, whilst the inner bead seal extends from one side of . the bag and terminates short of the other side, the venting passageway being placed in gas flow communication with atmosphere by means of a venting hole in the bag wall intermediate the ends of the passageway.

With this invention, the gases which build up within the . interior of the bag are able to escape by firstly entering the venting passageway and passing therealong (for at least a portion of its length) and exiting through the venting opening to atmosphere. With a positive pressure inside the bag, the opposed wall surfaces defining the venting passageway separate -3 as the gases pass therealong, whilst in the case of an external positive pressure existing externally of the bag, the opposed surfaces of the venting passageway tend to “stick or “cling together to create a sealing effect which inhibits the entry of . ambient air into the interior of the bag. It has been found that due to factors such as temperature, an equilibrium state is rarely achieved - that is where the ambient pressure is equal to the pressure inside of the bag, but even with an equilibrium condition, it has been found that the ingress of . air along the venting passageway is substantially inhibited due to the tendency of the plastics film material to “stick or “cling to itself.

In order to more fully explain the present invention, several embodiments are described hereunder in some further . detail and with reference to the accompanying drawings in which:Fig. 1 is a perspective view (with a cut-away section) of a plastic bag incorporating venting means according to one embodiment of the invention; . Fig. 2 is an enlarged transverse cross-sectional view along the lines 2-2 of Fig. 1; and Figs. 3 to 6 are schematic plan views of bags according to alternative embodiments of the invention.

In the embodiment of Figs. 1 and 2, reference is made to 25. tbe packaging of lucerne in a plastic bag 10 for preserving the lucerne for use as animal feed. The bag is made of a plastics film sold under the proprietary name “CRYOVAC“ and manufactured by W.R. Grace of Australia - this being a plastic laminate film commonly used as an oxygen barrier film for packaging foods. Of jfi·:-........_^_*A£S££i5; course other thermoplastics materials, for example polythene, may be used.

In this embodiment, the plastics bag 10 is of rectangular shape and comprises opposed front and rear panels 11, 12 of . plastics film in overlying relationship, the panels 11, 12 being joined at their sides, with the top of the bag 10 being open to allow material to be inserted into the bag interior so as to fill same. The bottom of the bag 10 is formed with an elongate venting passageway 13 defined between a pair of . transversely extending, spaced apart, parallel bead seals 14, (formed by welding) which are in turn parallel to the bottom edge of the bag 10, the bead seals 14, 15 fusing together contiguous surfaces of the front and rear panels 11, 12. In this embodiment, the outer bead seal 14 extends uninterruptedly . across the whole width of the bag 10 and seals off the bottom thereof, while the inner bead seal 15 extends from one of the sides of the bag 10 but terminates a short distance from the other side of the bag to thereby form an opening 16 which places the passageway 13 into gas flow communication with the . bag interior 17. A hole 19 in one or both of the walls 20, 21 of the passageway 13 centrally thereof places the venting passageway 13 into gas flow communication with the atmosphere.

Once the bag 10 is filled with its contents, the top edge 22 is sealed by welding, adhesive means, or wire crimping.

. With this arrangement, the gases (mainly CO2) given off by the fermenting lucerne packaged within the bag 10 are able to escape by passing through opening 16 adjacent one side of the bag 10, into and along the venting passageway 13, and thereafter to atmosphere through the hole 19 in the wall(s) of the passageway 13. The pressure of gases is sufficient to separate the opposing walls 20, 21 of the venting passageway 13 which would otherwise be in contiguous relationship. When the gases are fully exhausted (or there are no more gases to be . released from the fermenting material in the bag), the surfaces of the opposed plastic film walls 20, 21 of the venting passageway 13 “cling together in such a way that the ingress of any air or oxygen from the atmosphere into the interior of the bag via the venting passageway 13 is substantially . inhibited. Where a negative pressure is developed within the bag 10, the sealing contact between the plastic film wall surfaces 20, 21 is even more enhanced.

It will of course be appreciated that the configuration of the venting means can be varied in a number of ways. Referring . to Fig. 3, the bag is formed with weld lines 25, 26, weld line extending uninterruptedly across the whole width of the bag, while weld line 26 is interrupted, approximately centrally thereof, to form an opening 27 which communicates with the bag interior. Holes 28 at each end of the passageway permit gases . flowing along the passageway to escape to atmosphere.

Fig. 4 shows the weld lines 29, 30 having their opposite ends terminating short of the opposite sides of the bag to thereby form two openings 31, 32 which respectively communicate with the bag interior and atmosphere.

. Fig. 5 shows weld lines 35, 36 identical to that described in Fig. 1 but with the venting hole(s) 37 adjacent the end of the passageway, whilst Fig. 6 shows the outer weld line 38 being interrupted to form a venting hole (to atmosphere) 40, with the inner weld line 39 extending from one side of the bag but terminating short of its other side.

In another non-illustrated embodiment, three or more bead seals may be formed so as to form a venting passageway which * . extends firstly in one direction across the bag and then in the opposite direction - somewhat in the form of a labyrinth.

A brief consideration of the above-described embodiments will indicate that the invention provides an extremely simple and inexpensive venting system for a plastics bag for . applications where gases need to be released from the interior of the bag but the entry of air or oxygen into the interior of the bag inhibited. The invention may have applications in other industries apart from animal feed production, for example, in the wine industry for the storage of fermenting wine, in the . food industry for the packaging of cheese, and in the home brew kit industry for fermenting home brewed beer.

Claims (12)

1. A flexible walled bag of synthetic plastics film material which is essentially impervious to air, said bag comprising a pair of opposed walls forming a bag enclosure, and integrally formed venting means adjacent one of the margins of the bag, 5 said venting means comprising a relatively narrow airflow or venting passageway formed between opposed wall portions of said walls, a first opening for placing said passageway in gas flow communication with the interior of the bag, and a second opening spaced from the first opening for placing the 10 passageway in gas flow communication with the atmosphere, whereby gases in the bag interior are able to escape to atmosphere through said second opening via the venting passageway but the ingress of air/oxygen from atmosphere is inhibited by virtue of the sealing effect created by the 15 drawing together of the contiguous surfaces of the opposed wall portions when the bag interior pressure is sub-atmospheric.

2. A flexible walled bag according to claim 1 wherein said venting passageway is formed by two spaced apart weld lines 20 extending across and fusing together said opposed walls, said opposed wall portions bridging said weld lines.

3. A flexible walled bag according to claim 2 wherein said weld lines are substantially parallel to one another and to a 25 transverse margin of the bag.

4. A bag according to any preceding claim wherein said first opening is located at or adjacent one end of said venting passageway.

5. A bag according to any one of claims 1 to 3 wherein said second opening is located at or adjacent one end of said venting passageway. 35

6. A bag according to any one of claims 1 to 3 wherein said first opening is located intermediate the ends of said venting passageway. -8IE 893462

7. A bag according to any one of claims 1 to 3 wherein said second opening is located intermediate the ends of said venting passageway. 5

8. A bag according to claim 6 wherein said first opening is formed by an interruption or gap in the weld line remote from said one of the margins of the bag.

9. A bag according to claim 2 wherein said second opening is

10. Formed by either an interruption or gap in the weld line proximate to said one of the margins of the bag or by means of a hole formed in one or both of the opposed wall portions of the venting passageway. 15 10. An improved method of packaging vegetable matter such as lucerne haylage in a flexible walled bag of synthetic plastics material which is impervious to air, said method comprising:(i) forming a pair of spaced apart bead seals extending across the fusing together opposed walls of said bag 20 near an end margin thereof so as to form a venting passageway extending across a major portion of the transverse width of the bag; (ii) forming a first opening for placing the venting passageway in gas flow communication with the 25 interior of the bag; (iii) forming a second opening spaced from said first opening for placing the passageway in gas flow communication with the atmosphere; (iv) filling the interior of the bag with vegetable 30 matter; and (v) sealing the bag at or adjacent its other end margin.

11. A flexible walled bag of synthetic plastics film 35 material substantially according to any one of the embodiments described herein with reference to and illustrated in the accompanying drawings . -9IE 893462

12. An improved method of packaging vegetable matter such as lucerne haylage into a flexible walled bag of synthetic plastics film material substantially as hereinbefore described and illustrated in any one of the embodiments herein.