METHOD FOR COMPRESSING STRUCTURED TISSUES

Abstract

A method and apparatus are disclosed for processing structured tissue material to form a compressed bundle of folded tissues. A web of at least one ply of structured tissue is subjected to a destructuring operation before folding with itself or with another similar web to form a stack. The stack can then be compressed to form the compressed bundle at a pressure that is less than would have been the case, had the structured tissue not first been destructured.

Claims

1. A method of processing structured tissue material to form a compressed bundle of folded tissues, the method comprising: providing a web comprising at least one ply of structured tissue; at least partially destructuring the at least one ply of structured tissue; folding the web with itself or with another similar web to form a stack; and compressing the stack at a compression of greater than 120 kN/m.sup.2 to form a compressed bundle of folded tissues having a density of greater than 0.2 g/cm.sup.3.

2. The method according to claim 1, wherein destructuring takes place by embossing and calendering the at least one ply of structured tissue.

3. The method according to claim 2, wherein embossing takes place at a pressure of from 15,000 N/mm.sup.2 to 25,000 N/mm.sup.2.

4. The method according to claim 2, wherein calendering takes place by setting a nip between the calender rollers, wherein the nip is from 0.1 to 0.02 mm.

5. The method according to claim 1, further comprising spreading the web subsequent to destructuring to remove wrinkles.

6. The method according to claim 1, wherein the web has a weight of between 10 gsm and 65 gsm.

7. The method according to claim 1, wherein the web comprises further plies of tissue material.

8. The method according to claim 1, wherein the web is partially cut or perforated into sheets prior to being folded.

9. The method according to claim 1, wherein the web is folded in an interleaved fold configuration.

10. The method according to claim 1, wherein the stack has a width of between 70 mm and 100 mm.

11. The method according to claim 1, wherein the stack has a length of between 1.5 m and 2.5 m.

12. The method according to claim 1, wherein destructuring and folding take place in a tissue conversion machine in a continuous process and the stack is subsequently delivered to a compression station for compression of the stack.

13. The method according to claim 1, comprising calendering and embossing and wherein calendering takes place subsequent to embossing.

14. The method according to claim 1, further comprising delivering the compressed bundle to a bander station and wrapping the bundle in a wrapping web to form a wrapped bundle.

15. The method according to claim 14, wherein the wrapped bundle is in the form of an elongate log and the method further comprises sawing the log into a plurality of individual tissue packages.

16. A tissue package comprising a plurality of folds of embossed and calendered, structured tissue enveloped in a wrapping web, the package having a density of greater than 0.2 g/cm.sup.3, and the pressure exerted on the wrapping web is less than 130 kN/m.sup.2.

17. The tissue package of claim 16, wherein the tissue is hybrid tissue comprising plies of dry crepe and structured tissue.

18. The tissue package of claim 16, wherein the wrapping web comprises high-tensile paper having a tensile strength in a height direction of the stack of at least 3.5 kN/m.

19. A tissue conversion apparatus for converting a tissue web of structured tissue into folded tissue bundles, the apparatus comprising: an embossing station; a calendering station; a folding station; a compression station; and a wrapping station, wherein the apparatus is arranged to pass the web through the embossing station and the calendering station to the folding station for forming a folded tissue bundle and the compression station is arranged to compress the stack at a compression of greater than 120 kN/m.sup.2 to form a compressed bundle of folded tissues having a density of greater than 0.2 g/cm.sup.3.

20. The apparatus according to claim 19, further comprising a spreading station subsequent to the embossing station for removing wrinkles.

21. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The present invention will be discussed in more detail below, with reference to the attached drawings, in which:

[0042] FIG. 1 is a schematic side view of part of a tissue conversion machine according to the present invention; and

[0043] FIG. 2 is a schematic view of the conversion machine of FIG. 1 and a packaging system of the invention.

DESCRIPTION OF EMBODIMENTS

[0044] FIG. 1 is a schematic side view onto part of a tissue converting machine 1 that may be used according to the present invention. In this embodiment, the converting machine 1 is described during the production of single ply structured tissue 10. The skilled person will nevertheless understand that other structured tissue types and weights may also be used. For the sake of convenience only the right-hand half of the machine 1 is described. It will be understood that the left-hand half of the machine 1 may be substantially identical.

[0045] The machine 1 comprises a supply roll 60 of unconverted tissue 10 that exits the supply roll 60 in the form of web 11. The web 11 is passed around tensioning roller 62 to a pair of embossing rollers 64. The embossing rollers 64 are a pair of steel matched cylinders which are engraved and structured to give a double-sided pattern when embossing. The skilled person will recognise that a steel on rubber combination may also be employed. Steel-steel gives a two sided imprint while steel-rubber give a single sided imprint to the web 11.

[0046] From the embossing rollers 64, the web 11 passes between brush spreader rollers 65, which spread the web 11 to remove wrinkles resulting from the embossing stage. The web 11 then enters the nip of calender rollers 66, which in the illustrated embodiment are set with a gap distance between the rollers 66 of between 0-33% of paper thickness, to calender the now embossed web 11 to a thickness comparable to the initial thickness prior to embossing.

[0047] From the calender rollers 66, the web 11 proceeds to a perforating roller 3 at the outlet of the converting machine 1, where it is partially cut to define individual tissue lengths. At this point, the first web 11 from the right-hand half of the machne 1 is combined with the second web 12 from the left-hand half of the machine, which is partially cut around perforating roller 4.

[0048] The two webs 11, 12 after passing around perforating rollers 3, 4, are folded together at interfolder 6. The tissue 10 coming from the respective webs 11, 12 is folded together in Z-formation, with folds of the respective webs 11, 12 interleaved together as is otherwise well known in the art. The partial cuts are offset from each other in the respective webs such that the folded tissue web is continuous and, when drawn from a dispenser, tissues from each web will be dispensed alternately. The folded tissue 10 is collected as a stack 14 in stacking station 8 until the stack reaches an uncompressed height H1, which in this case is around 130 mm. The stack 14 has a stack width W, which in this case is around 85 mm, being a standardized dimension for use in certain tissue dispensers. These dimensions can of course be adjusted according to the tissue material, the process and/or the required end use.

[0049] FIG. 2 is a schematic view in the direction II of FIG. 1, in the process direction of the converting machine 1. According to FIG. 2, the perforating roller 4 is shown above the interfolder 6 and the stacking station 8. The tissue webs 11, 12, and the converting machine 1 all have an effective width L, which defines the length of the stack 14. In the present embodiment, this length L is 2200 mm although the skilled person will understand that this is a variable that will be determined by the machine and/or the end use.

[0050] Aligned with the stacking station 8, is a packaging system 2 for packaging of the converted tissue produced by the converting machine 1. The packaging system 2 comprises a number of apparatus arranged in sequence in a transport direction X and aligned with the stacking station 8 for handling and packaging of the stack 14 in an effectively continuous process. It will be understood that the converting machine 1 and packaging machine 2 are both complex installations having many more components that are neither shown nor discussed as they are otherwise not relevant to the present invention.

[0051] Aligned with an outlet 16 of the converting machine 1, there is an attachment applying apparatus 20 comprising a supply of attachment elements 22 and application heads 24. The attachment applying apparatus 20 is in turn aligned with an input end 26 of compression apparatus 30. Compression apparatus 30 includes first and second opposed compression members 31, 32, which define a compression path 27, each of which carries respective first and second transport surfaces 33, 34. The first compression member 31 is mounted to be movable in a vertical direction Z and an actuator mechanism 36 comprising a plurality of actuators 38 is arranged for moving the first compression member 31 towards and away from the second compression member 32.

[0052] An outlet end 28 of the compression apparatus is aligned with a bander apparatus 40 having a transport path 42 for a compressed log 44 and which is provided with a supply of wrapping web 46 and an adhesive applicator 48. The bander apparatus 40 is in turn aligned with a saw station 50, comprising an otherwise conventional circular saw 52, arranged to cut individual bundles 54 from the log 44. The log 44 has a final height H2, which is significantly less than the uncompressed height H1.

[0053] Operation of the packaging system 2 in the packaging of tissue bundles according to the invention will now be described with reference to FIG. 2.

[0054] A tissue stack 14 is collected in the converting machine 1 until the stack 14 reaches an uncompressed height H1, at which point the tissue webs 11, 12 are broken and the stack 14 is moved out of the outlet 16 and into the attachment applying apparatus 20. As indicated above, additional rollers, grippers, guides, sensors, actuators, drives and transport provisions will be present to facilitate this movement. Such provisions are conventional and are not further discussed in this context.

[0055] As the tissue stack 14 passes in the transport direction X through the attachment applying apparatus 20, the uppermost tissue and the lowermost tissue of the stack 14 are engaged by application heads 24, which apply attachment elements 22 to these surfaces. The attachment elements 22 are provided on a continuous attachment strip having a self-adhesive surface that adheres to the tissue material. In this embodiment, the attachment elements 22 on the upper and lower surfaces of the stack 14 are identical hook and eye type fasteners, such that there will be no need to orientate a bundle 54 in use.

[0056] From the attachment applying apparatus 20, the stack 14 proceeds in the transport direction X to the compression apparatus 30 and enters the compression path 27 via the inlet end 26. In order that the stack 14 can enter the compression path 27, the first compression member 31 must be spaced from the second compression member 32 by a spacing that is greater than the uncompressed height H1 of the stack 14. To this purpose, the actuators 38 have been operated to withdraw the first compression member 31 in the Z direction.

[0057] Once the stack 14 is completely within the compression path 27, the actuators 38 are operated to move the first compression member 31 in the Z direction towards the second compression member 32. This movement proceeds until the first compression member 31 is spaced from the second compression the actuators 38 may be operated to move the first compression member 31 until a certain pressure is achieved. This pressure may be around 160 kN/m2, according to requirements. The spacing at this time may be less than H2, allowing for some spring back of the tissue material once the pressure is removed. During the compression stroke, the respective first and second transport surfaces 33, 34 move the stack 14 along the compression path 27 from the inlet end 26, to the outlet end 28. Once compressed in this state, the stack 14 is referred to in the following as a log 44.

[0058] On exiting the outlet end 28 of the compression apparatus 30, the log continues to move in the transport direction Z into the bander apparatus 40. The bander apparatus 40 may be otherwise conventional apart from its adaptation to handle relatively highly compressed logs. The log 44 leaving the compression path 27 has a tendency to recover to a greater height and the transport path 42 through the bander apparatus 40 must maintain this compression until the wrapping web 46 has been applied. The wrapping web 46 is applied around the log 44 from upper and lower web dispensers as a two-part wrapper, joined to each other along a longitudinal seam by a hot-melt adhesive. It will be understood that a one-part wrap-around wrapper could alternatively be used. The wrapper material is of surface weight 110 gsm virgin paper and somewhat stronger than a wrapper conventionally used for loose bundles of similar weight.

[0059] The wrapped log 44 on exit from the bander apparatus 40 has a final height H2 of around 100 mm and a final density of around 35 g/cm3. At this value, the tissue material is still viable and once dispensed has all of the properties expected of it and from a user perspective is identical to tissue material exiting the conversion machine 1. The log 44 no longer needs to be maintained in compression since the wrapping web 46 prevents expansion. The log 44 proceeds to saw station 50 where circular saw 52 cuts individual bundles 54 from the log 44. This portion of the operation may take place offline or out of line with the other operations of the packaging system 2. In particular, the saw 52 may require intermittent advancement of the log 44, while the log 44 may proceed at a constant speed through the attachment applying apparatus 20, the compression apparatus 30 and the bander apparatus 40.

[0060] It will be recognized that while the invention has been described by reference to the embodiments discussed above these embodiments are susceptible to various further modifications and alternative forms well known to those of skill in the art, without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.