TUBE MAKING MACHINE AND PROCESS BACKGROUND OF THE INVENTION

The present invention relates to tube making machines and processes of making tubular material from plastics material film web. Flexible tubular material made from plastics material film has a number of practical uses including, for example, as an outer protective sheath to protect pipeline lengths, particularly when they are made from metal. A still further possible application is to convert the plastic flexible plastic tubing into bags by cross or transverse sealing the tubing to itself and severing the tubing into individual lengths forming bags. It is of course possible to also simultaneously fill such bags with a liquid or otherwise flowable material as the tubing and the bags are produced. Other possible uses are also anticipated.

US patent specification no. 5566530 discloses making bags from tubing formed by wrapping flexible plastics material web in a plurality of overlapping helical spirals and closing opposed ends of lengths of such tubing to form a bag. Such bags are inexpensive to produce and can provide quite strong bags to enable heavy loads to be packed, stored or transported therein. These types of bags work quite well and are generally inexpensive to manufacture, however, they do have in some forms, certain disadvantages. One such disadvantage is that the helical or spiral wrapping of the film web layers does provide a "washboard effect" in that transverse join regions are formed both internally and externally on the side walls of the bag. Pressure from the filling apparatus or the filling material itself may cause these join regions to open up to some extent, particularly if the edge regions face the filling direction, which may over time cause leakages or bag / wall failure. Similar effects may also occur on the outer surface of the bag over time by weathering or other external influences. Another disadvantage of these systems is the speed of bag formation, filling and closing can be limited if high speed operation in a continuous or semi-continuous basis is desired. A still further disadvantage of known arrangements of this type, particularly when the formed bag is filled under pressure in a vertical direction is that the overall height of the machinery needed for relatively continuous operation is too great for many conventional building sites.

International patent application no. PCT/AU2005/001166 also discloses a similar arrangement for making tubular material and preferably bags therefrom. In this disclosure at least multiple plastics material film webs are first laid in a longitudinal or tube movement direction with longitudinal edge zones overlapping and adhered to one another. This solves the potential weaknesses by a washboard effect on the inside of the tubing. Conveniently the adherence of the longitudinal edge zones is achieved by using plastic material film with some self adhesive capabilities or characteristics. This of course is not a problem if the tubing is to be immediately filled and formed into bags, however, if the tubing is collapsed and rolled up onto a storage roller for later use, either as bag making material as protective sheathing (or otherwise), then the inside surfaces of the tubing tend to self adhere making future use of the tubing material difficult. SUMMARY OF THE INVENTION

The objective of the present invention is to, in one aspect, solve the above- mentioned potential difficulty, but in other aspects provide improvements in the machine, the manufacturing process and the material formed thereby over that which is disclosed in International patent application no. PCT/AU2005/001160.

Accordingly, the present invention provides, in a first aspect, a flexible tube formed from overlapping layers of flexible plastic material film webs at least partially adhered to one another, the tube being formed with a first region formed by at least one said plastic material film web extending in a longitudinal direction with an adjacent edge zone or adjacent edge zones overlapping to form a tube, said overlapping edge zone or zones being heat sealed to one another, and a second region formed by at least one said plastics material film web wrapped in spirally wound layers with at least adjacent transverse edge zones overlapping and adhered to one another, said first and second regions being adhered to one another, with said first region forming an inside surface of the tube. Conveniently multiple said film webs are provided in the first region. By providing such an arrangement, a relatively strong tube (or bag formed therefrom) can be produced in an economical manner whereby the inside of the tube (or bag) is completely sealed without the prospect of leakage occurring.

Preferably the plastic material film web or webs in the first region are not self adherent, particularly if the tube alternately produced is to be pressed flat and

rolled onto a storage roll for later use. The non-adherent quality of the inner surface of the tube is also helpful to allow the tube to be drawn from a stationary former means. If the tube is to be simultaneously formed into filled bags, then the non-adherent capabilities of the internal film webs is less important. The plastic material film web or webs forming said second region are self adherent plastic material film web(s). It is, preferable, but not essential that the plastic material film web be a polyolefin such as linear low density polyethylene. Conveniently such film web material might be pre-stretched beyond its yield point to increase its length and decrease its thickness. The film web material used in both the first and second regions might also include in their composition, substances to improve its self adherent qualities when required.

Conveniently, the tube may include a third region positioned outwardly of said second region, the third region including at least one said plastics material film web wrapped in spirally wound layers with at least adjacent transverse edge zones overlapping and adhered to one another, the film web or webs in said third region being spirally wound opposite to the film web or webs forming said second region, said second and said third regions being adhered to one another.

The present invention, in a further aspect, may also provide a flexible tube formed from overlapping layers of flexible plastic material film webs at least partially adhered to one another, the tube being formed with a first region formed by at least one said plastic material film web extending in a longitudinal direction with adjacent edge zones overlapping to form a tubular structure, a second region formed outwardly of said first region by at least one said plastics material film web wrapped in optionally wound layers with at least adjacent transverse edge zones overlapping and adhered to one another, a third region formed outwardly of said second region including at least one said plastics material film wrapped in spirally wound layers with at least adjacent transverse edge zones overlapping and adhered to one another, the film web or webs in said third region being spirally wound opposite to the film web or webs forming said second region. Such a crossed arrangement of the spirally wound layers provides a much stronger and durable wall structure.

Preferably the third region described above may include a plurality of further plastic material film webs extending in the longitudinal direction with

adjacent edge zones overlapping and adhered to one another, said further plastic material film webs extending in the longitudinal direction being disposed either inwardly, outwardly or both inwardly and outwardly of the plastics material film web wrapped in spirally wound layers in said third region. In accordance with one preferred application, a tube formed as aforesaid might be further formed into bags by flattening the tube and transversely sealing same across its flattened width at longitudinally spaced locations, the tube being separated at least transversely through or adjacent each said seal to form said bags. In a further preferred application, the tube being flattened and sealed by a first transverse seal extending across its width, the tube forward of said first transverse seal being filled with said material contents and subsequently sealed by a second transverse seal across its width, the first and said second transverse seals being longitudinally spaced. The aforesaid bags (empty or filled) might be produced as the tube is produced or alternatively from a storage roll of the tube that has previously been produced as described above.

In accordance with another aspect of this invention, there is provided apparatus for producing a flexible tube from overlapping layers of flexible plastic material film webs at least partially adhered to one another, said apparatus including: a longitudinally extending stationary former means on which said flexible plastic material film webs are laid, said former means in a first section defining in cross-section a polygonal shape; first dispensing means for dispensing at least one said plastic material film web in said longitudinal direction onto said first section of the former means, the or each said film web being formed into a tubular shape with adjacent edge zones overlapping; heat seal means to heat seal the or each of said overlapping adjacent edge zones together; second dispensing means for dispensing at least one further plastic material film web wrapped in spirally wound layers with at least transverse edge zones overlapping and adhered to one another over said plastic material film webs extending in said longitudinal direction to form said tube; and

withdrawal means provided to withdraw said tube from said stationary former means. Conveniently, the first dispensing means permit dispensing of at least two said plastic material film webs in the longitudinal direction.

Conveniently the stationary former means in said first section includes a plurality of elongate members extending longitudinally and located at the corners of a polygon in transverse cross-section. Preferably each of the elongate members has a dry non-stick coating applied to its surface adapted to contact the plastics material film web or webs extending in said longitudinal direction. The apparatus may include a third dispensing means downstream of said second dispensing means for dispensing at least one additional plastic material film web wrapped in spirally wound layers with at least transverse edge zones overlapping and adhered to one another, said third dispensing means operating in an opposite direction to said second dispensing means whereby the spirally wound layers extend in opposition directions. Conveniently, a fourth dispensing means for dispensing a plurality of additional plastic material film webs in said longitudinal direction with adjacent edge zones overlapping. A said fourth dispensing means may dispense said additional plastic material film webs onto the plastic film web or webs laid by said second dispensing means. Preferably a said fourth dispensing means is also positioned downstream of the third dispensing means.

Conveniently, the former means includes a second section downstream of said first section, said second section in cross-section progressively becoming larger in one dimension and smaller in a second dimension at 90° to said one dimension. The apparatus may include downstream of the second section of the former means, a pair of transversely extending cooperating rollers are provided having a nip through which the tube passes in a flattened condition, said cooperating rollers pressing together the plastic material film webs forming said tube. Preferably at least one, or both of the aforesaid cooperating rollers is, or are, brush rollers. The apparatus may further include a plate member positioned in the tube at at least the nip formed between said cooperating rollers, said plate member having a plurality of grooves or slots extending in the longitudinal direction. The withdrawal means of the apparatus may include at least one pair

of driven rollers pressed against outer surfaces of the tube and driving the tube in a direction away from said former means. BRIEF DESCRIPTION OF THE DRAWINGS

Further preferred features of the present invention will become apparent from the following description of a preferred embodiment of apparatus for carrying out the invention given in relation to the accompanying drawings, in which:

Fig 1 is a schematic side elevation view of the apparatus;

Fig 2 is a schematic cross-sectional view along line 2-2 of Fig 1 ;

Fig 3 is a schematic cross-sectional view along line 3-3 of Fig 1 ; Fig 4 is a schematic cross-sectional view along line 4-4 of Fig 1 ;

Fig 5 is a schematic partial sectional view along line 5-5 of Fig 1 ; and

Fig 6 is a partial perspective view of the downstream side of the intermediate station for applying further film web layers to the tube being produced. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

Referring to Fig 1 , the apparatus 10 has a first flexible plastic film web dispensing station 11 where rolls of film web 12, 13, 14 and 15 dispense film webs 16, 17, 18 and 19 in the longitudinal direction such that longitudinal edge zones overlap in overlapping edge regions 20, 21 , 22 and 23. As is best seen in Fig 2 (and Figs 3 and 4), a stationary former means 24 is provided including stationary elongate members 25, 26, 27 and 28 in the form of circular tubes or pipes coated with a non-stick or dry lubricant coating 29 such as Teflon or similar. The support tubes 25 to 28 are, in the illustrated embodiment, at the corners of a square, however, other polygonal shapes could be employed. Located at or adjacent the first dispensing station 11 on the downstream side of same are a plurality (in this case four) heat sealing devices 30, 31 , 32, 33 provided to create heat sealing lines 34, 35, 36, 37 in the film web overlapping edge regions 20 to 23 sealing the film web layers together in these regions. As can be seen in Fig 2, a fully circumferentially sealed inner tube 38 is created from the four longitudinally extending film webs 16 to 19. While four such film webs are used in the illustrated preferred embodiment, it will be recognized that one, two, three, five or

more film webs can be used so long as the overlapping edges are heat sealed to form a tubular structure.

A second or intermediate plastic film web dispensing station 39 is illustrated in Fig 1 for forming a second region 72 of the tube. The stationary former means 24 extends through the second film dispensing station 39. On an upstream side of the station 39, a large ring sprocket wheel 40 is positioned driven rotationally by a chain 41 which in turn is driven by a smaller sprocket wheel 42 and motor 43. The large sprocket wheel 40 includes an axial or longitudinally extending shaft 44 carrying a film web roll 45 such that with rotation of the sprocket wheel 40, a film web 46 is dispensed from the roll 45 and laid in overlapping spirals 47. It will of course be recognized that multiple shafts 44 might be provided spaced circumferentially about the wheel 40 such that multiple film webs could be dispensed simultaneously if desired. The film web or webs 46 are laid directly onto the inner tube 38 and adhered thereto by self adherent qualities of the film web or webs 46. On the downstream side of the dispensing station a second large ring sprocket wheel 48 is positioned driven rotationally by a chain 49 which in turn is driven by a smaller sprocket wheel 50 and motor 51. The rotational direction of the large sprocket wheel 48 is opposite to that of the sprocket wheel 40. The downstream large sprocket wheel 48 also carries an axial or longitudinally extending shaft 52 extending in the downstream direction which also carries a roll 53 of a plastics material film web which dispenses a film web 54 onto the plastics material film tube 55 passing downstream out of the dispensing station 39. Because the large diameter ring sprocket wheels 40 and 48 rotate in opposite directions, the spiral layers 56 laid by the film roll 53 are directed oppositely to the spiral layers 47 laid by the film roll 45. The second dispensing station 39 may optionally include means for dispensing further plastics material film webs in the longitudinal direction laid between the spiral layers 47, 56 laid by the film rolls carried by the two large ring sprocket wheels 40 and 47. As illustrated this may include plastic film rolls 57, 58, 59 and 60 dispensing film webs 61 , 62, 63, 64 in the longitudinal direction such that their edge zones overlap in overlapping zones 65. The pitch of the spirals laid is dependent both on the speed of movement in the longitudinal direction of the tube being formed and the rotational speed of the large sprocket wheels 40 and 48.

Beyond the second film dispensing station 39, the inner former means supporting frame structure 24 progressively widens and flattens such that when the flexible plastic tube 66 leaves the supporting frame it can be passed through the nip between two rollers 67, 68 driven in opposite directions to pull the tube 66 off the former means 24 to press the layers of the tube 66 together. Conveniently the rollers 67, 68 are brush rollers as shown in Fig 5. Each of the rollers 67, 68 also conveniently press the film layers against an internal plate 69 that has longitudinally extending grooves or slots to allow the escape of air that might otherwise build up in this area. In the embodiment illustrated the flattened and pressed tube made up of layers of film webs is moved onto a storage roll 70.

It will of course be appreciated that as an alternative to forming and storing a roll of tubular material as illustrated, the tubing might be converted into bags by transversely sealing the tube and separating (cutting) the tube transversely through or adjacent the transverse seals. Bags might also be simultaneously filled with a desired liquid or flowable contents (eg particulate materials) by providing an optional filling pipe 71 internally of the tube being produced and transverse sealing the tube with desired contents held therebetween. Arrangements of this type are disclosed in International patent application no. PCT/AU2005/001160 and similar arrangements might also be used in the present case.

Other modifications and variations within the scope of the annexed claims will be apparent to those skilled in the art. For example, the outer surface of the tube may be formed by a longitudinally extending web or webs applied over the last laid spirally wound layer.