US3196587A

US3196587A - Packaging process

Info

Publication number: US3196587A
Application number: US223968A
Authority: US
Inventors: Hayward Anthony; Hill John William
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1961-09-26
Filing date: 1962-09-17
Publication date: 1965-07-27
Anticipated expiration: 1982-07-27
Also published as: GB951228A

Description

July 27, 1965 A. HAYwARD ETAL 3,196,587

PACKAGING PROCESS Filedrsept. 17, 1962 United States Patent O 3,196,537 PACKAGING PRCESS Anthony Hayward, Thornton, and .lohn William Hiil,

Cleveleys, Engiand, assigiiors to imperial Chemical Industries Limited, London, England, a corporation of Great Britain Filed Sept. 17, 1962, Ser. No. 223,968 Claims priority, application Great Britain, Sept. 26, 1961,

34A34/ 61 4 Claims. (Cl. 53-25) This invention relates to an improved packaging process, particularly useful for the packaging of granular solids and the bulk packaging of small articles.

In packaging granular solids and small articles in bulk in plastic bags and sacks, and heat sealing the pack, difficulty is caused by air becoming entrapped in the bag or sack on sealing, making it diicult or impossible to flatten the package, and, in the case of sacks, leading to very poor pallet stability and consequent danger in transporting and storing the filled sacks.

A number of methods are in use for removing air from plastic bags and sacks before sealing. For example, various methods of applying a vacuum before heat sealing have been developed, and it has also been possible in some instances to perforate the bag or sack in various ways to allow the air to escape. Vacuum methods, however, require complicated apparatus, while the presence of permanent perforations, however small, frequently leads to contamination of the bag contents, at least by the ingress of moisture, and allows only the very slow removal of air when the perforations are small.

It is an object of the present invention to provide an improved packaging process that allows for the escape of air from a plastic bag or sack before it is finally sealed.

By the term bag as used throughout this specification, we include large bags more usually described as sacks; indeed, the invention is applied with particular advantage to bags of such type. The term is also intended to include both unsupported bags and liners for bags of paper, hessian or other material.

In accordance with the invention, a process for the packaging of a material or articles in a plastic bag comprises: filling the material or articles into the bag; forming an interrupted seal across an opening of the bag, the interruptions in said seal being insufficiently large to allow the easy escape of the material or articles therethrough; flattening the bag to expel air through the interruptions in said seal; and thereafter forming a continuous seal across said opening of the bag.

By the statement that theV interruptions in the interrupted seal are insufficiently large to allow the easy escape of material, we mean that the material does not pass through the seal'to a signicant extent during the normal operation of flattening the bag, although they may be large enough to allow particles to be forced through them, or to allow some escape of lines or other undersized particles.

It will be understood that although only one opening of the bag has been referred to, any opening in the bag that is sufficiently large and of a construction such as to allow the easy escape of the contents therethrough should be sealed before pressure is exerted to flatten the bag, or should similarly be provided with an interrupted seal and subsequently with a continuous seal, as described for the one opening.

Generally the bag is filled before the formation of the interrupted seal, and the interrupted seal is then formed across the bag mouth or other filling opening. It is, however, within the scope of the invention to provide an interrupted seal across an opening of the bag other than the iilling opening, generally before the bag is lled, and

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thereafter to lill the bag, seal the filling opening, if necessary, flatten the bag with consequent expulsion of air through the interrupted seal, and form a continuous seal across the interrupted seal or the path of access thereto. This method may be used, for example, for bags provided with filling valves which do not normally allow the easy escape of air from the lled bags; sealing of the valves after lling is normally unnecessary.

The process may be used for closing the entire mouth of the bag or any part of it that has been left open for filling the bag or providing for the release of air, or for closing any other opening into the bag. It may be applied to the closing of both fiat and gusseted bags.

The interrupted seal and the nal seal are preferably formed by the application of heat and pressure when this method is appropriate to the nature of the plastic from which the bag is made. Polythene lin bags, for example, may be most easily sealed by this method, and the method is also suitable for sealing polyvinyl chloride film bags. Other sealing methods, for example those of highfrequency heating (especially useful for polyvinyl chloride film bags) or the application of adhesives, may be used when appropriate.

Our invention will be illustrated by reference to the accompanying drawing, in which is represented a filled sack, suitably of polythene film, sealed and iiattened in accordance with this invention. The sack shown and described is suitable for use, for example, in the packaging of polymers in the form of 1/8 inch cut cubes.

In this drawing: 1 represents the body of the sack, the flat width of which is 22 in.; 2 the mouth of the sack; 3 an interrupted seal in which sealed portions 0.3 inch in length alternate with unsealed portions 0.2 inch in length, this interrupted seal having been formed by heat sealing by means of a conventional heat sealer modified by the provision of a suitably castellated blade, after the bag has been lled but before it has been ilattened; and 4 a continuous seal formed after the bag has been flattened and the air expelled through the spaces in the seal 3. The interrupted seal bows somewhat, as shown in the drawing, during the iiattening of the sack, because the ears of the sack become filled with the contents.

In a modification of the process described with reference to the drawing, only a 16.5 inch section of the central portion of the interrupted heat seal 3 contains unsealed portions, which again are 0.2 inch in length, the seal becoming continuous towards the side folds of the sack. This provides a stronger seal in the parts subjected to greater forces.

For simplicity, it is usually preferred to form the interrupted heat seal by means of a conventional sealing machine adapted to provide a interrupted seal of this type, for example as in the process just described, by the use of a heated, castellated blade which presses the plastic on to a rubber roller, the latter being provided with a nonstick surface in relation to the plastic being used. Highfrequency welding machines may be similarly modified by the provision of a castellated blade. The interrupted seal may however by formed by other methods, for example by inserting a thin comb of non-stick material, such as a material coated or impregnated with polytetraiiuoroethylene, or a non-stick foil, for example of vinyl chloride/vinyl acetate copolymer, between the film surfaces, and sealing the film in the interstices by using a continuous sealer blade to apply heat and pressure.

Many other modifications may be made in the process particularly described without departing from the scope of this invention, particularly as regards the method of and position of sealing, as mentioned hereinbefore, the dimensions of the bag, which will depend on the material being packed and its application, and the dimensions of the interruptions in the seal, the optimum size of which will depend on the particle size of the material being packed. Moreover, although it is usually preferred to form the continuous seal in a position beyond the interrupted seal, towards the bag mouth, as shown, it may be superimposed on the interrupted seal, when this can be done without adverse effect on the strength of the material at the seal. Generally, the contents of the filled bag will prevent the continuous seal from being formed on the other side of the interrupted seal, although there would ofcourse normally be no other reason why it should not be so situated. if desired, more than one interrupted seal may be formed to prevent the escape of the contents while allowing the easy escape of air; for example, two parallel seals with staggered interruptions may be provided.

A particularly suitable method for iiattening bags filled with granular materials, after they have been provided with the interrupted seal, is that described in UK. specification No. 841,644, now abandoned. in this method, the filled sack is conveyed along a vibrating table having a direction of vibration inclined at less than 90 to the plane of the tablel in the direction of travel of the sack with a vertical component capable of suspending the granular material and a horizontal component capable of conveying the sack alongthe ta le, and the sack, while being so conveyed, is caused to support a platen which is at least as long and as wide as the sack and is free to move about a stationary supporting means in at least a direction having a vertical component. After flattening, the bag is provided with its continuous seal in accordance with the present invention.

The process of this invention may be used for the packaging of a wide diversity of materials, and is particularly useful for the packaging of materials and objects that need to be shielded from moisture, which is particularly eliiciently done by the use of plastic bags. Such materials include, for example: chips or other granular forrns of organic polymers such as polythene, polyvinyl chloride, nylon, linear polyesters, and polymethyl methacrylate; granular chemicals and fertilisers; grain; feeding stuffs.

When the process is used for the packaging of materials or articles that emerge from the final manufacturing or finishing step at a raised temperature, it is preferred that the bags be filled, flattened Vand sealed before the contents have cooled to ambient temperature. The contraction of the remaining air after the bags have been sealed brings about even further flattening and firming of the pack, which greatly facilitates palleting. The bags when cool take on a stippled appearance; this gives good adhesion on the pallet, preventing or greatly reducing `sliding and sideways movement of the bags.

1t is further preferred that, when the sacks are to be palleted, this is also done while the Acontents are still warm. The bag of warm material, when finally sealed, is not particularly rigid, and when palleted the sacks will take up a shape depending on the position of the sacks above and below them on the pallet. Only when cool (and this can take up to 48 hours) do the palleted bags attain full rigidity, and consequently they become keyed together in their assumed shapes. which air has been removed by applying a vacuum are quite rigid, and are palleted like bricks; and although the resultant pallet in one sense is stable, it does not possess the keyed in quality just described.

The process of the present invention allows plastic bags to be used without any of the disadvantages that often arise through the inclusion of excess air in the bags. Pallets carrying the filled bags can be stacked one upon another with maximum safety, through the increased stability of the stack, and with greatsaving of space.

By contrast, sacks from We claim:

1. A process for the packaging of a particulate material or a plurality of small articles in a plastic bag that comprises raising the temperature of the material or articles materially above ambient temperature; lling the material or articles into the bag; forming an interrupted seal across an opening of the bag, the interruptions in said seal being insufliciently large to allow the easy escape of the material or articles therethrough; flattening the bag to expel air through the interruption in said seal and redistribute the material or articles within the bag to minimize the thickness of the material or article filled bag and maximize the lateral extent thereof; and thereafter forming a continuous seal across said opening of the bag before the material or articles have cooled to ambient temperatureg'allowing said material or articles in said bag to cool to ambient temperature, whereby upon cooling said bag takes on a vstippled appearance as the air remaining in the bag contracts thereby facilitating more stable palleting of said bag with like filled bags; and palleting said bag with like lled bags.

2. Process as claimed in claim 1 in which the bag is filled before the formation of the interrupted seal, and the interrupted seal is then formed across the lilling opening.

3. A process as claimed in claim i in which the interrupted seal is formed across an opening of the bag other than the filling opening, before the bag is filled, and the bag is then filled, air is expelled through the interrupted seal, and a continuous seal is then formed across the interrupted seal or the path of access thereto.

4. A process for packaging of particulate material or a plurality of small articles in plastic bags that comprises: raising the temperature of the material or articles materially above ambient temperature; filling the material or articles into the bag; forming an interrupted seal across an opening of each bag, the interruptions in said seal being insufficiently large to allow the easy escape of the material or articles therethrough; flattening the bags to expel air through the interruptions in said seals and redistribute the material or articles within the bags to minimize the thickness of the material or article filled bags and maximize the lateral extent thereof; thereafter forming continuous seals cross said openings of said bags before the material or articles have cooled to ambient temperature; palleting said bags in at least two layers before the material or articles therein have cooled to ambient temperature; allowing said material or articles in said bags to cool to ambient temperature, whereby upon coolingsaid bags take on a stippled appearance as the air remaining in said bags contractsthereby producing stable pallets wherein the stippling of adjacent bags is substan tially interdigitated.

References Cited by the Examiner UNTTED STATES PATENTS 2,378,920 6/45 Gillican 53-25 2,655,271 10/53 Cole et al. 2,676,440 4/54 Campbell 53-22 X 2,875,070 2/59 Rockland et al 53-22 X 3,108,881 10/63 Shaw et al 53-22 X 3,113,874- 12/63 Baush 5.3--22 X FOREIGN PATENTS 565,913 4/58 Belgium. 607,267 10/ 60 Canada.

GRANVILLE Y. CUSTER, JR., Primary Examiner.

TRAVIS S. MCGEHEE, FRANK E. BAILEY, Examiners.

Claims

1. A PROCESS FOR THE PACKAGING OF A PARTICULATE MATERIAL OR A PLURALITY OF SMALL ARTICLES IN A PLASTIC BAG THAT COMPRISES RAISING THE TEMPERATURE OF THE MATERIAL OF ARTICLES MATERIALLY ABOVE AMBIENT TEMPERATURE; FILLING THE MATERIAL OR ARTICLES INTO THE BAG; FORMING AN INTERRUPTED SEAL ACROSS AN OPENING OF THE BAG, THE INTERRUPTIONS IN SAID SEAL BEING SUFFICIENTLY LARGE TO ALLOW THE EASY ESCAPE OF THE MATERIAL OR ARTICLES THERETHROUGH; FLATTENING THE BAG TO EXPEL AIR THROUGH THE INTERRUPTION IN SAID SEAL AND REDISTRIBUTE THE MATERIAL OR ARTICLES WITHIN THE BAG TO MINIMIZE THE THICKNESS OF THE MATERIAL OR ARTICLE FILLED BAG AND MAXIMIZE THE LATERAL EXTENT THEREOF; AND THEREAFTER FORMING A CONTINUOUS SEAL ACROSS SAID OPENING OF THE BAG BEFORE THE MATERIAL OR ARTICLES HAVE COOLED TO AMBIENT TEMPERATURE; ALLOWING SAID MATERIAL OR ARTICLES IN SAID BAG TO COOL TO AMBIENT TEMPERTURE, WHEREBY UPON COOLING SAID BAG TAKES ON A STIPPLED APPEARANCE AS THE AIR REMAINING IN THE BAG CONTRACTS THEREBY FACILITATING MORE STABLE PALLETING OF SAID BAG WITH LIKE FILLED BAGS; AND PALLETING SAID BAG WITH LIKE FILLED BAGS.