Method and apparatus for compressing an elongate stack of folded tissues

Abstract

A method and apparatus are disclosed for compressing an elongate stack of folded absorbent tissues to form a tissue log. A stack of folded absorbent tissues is transported along a compression path from an input end to an output end, the compression path being defined between first and second opposed transport surfaces provided on first and second compression members. The first compression member is moved towards the second compression member from a first spacing to a second spacing to compress the stack and form the log. The compression path has a length greater than the stack length and during compression, the stack moves along the compression path with respect to the compression members. During this process, the stack will be compressed from a first height to a second height corresponding to the second spacing.

Claims

1. A method of compressing an elongate stack of folded absorbent tissues to form a tissue log, the method comprising: providing a stack of folded absorbent tissues having a stack length; transporting the stack along a compression path from an input end to an output end, the compression path being defined between first and second opposed transport surfaces provided on first and second compression members; and moving at least the first compression member towards the second compression member from a first spacing to a second spacing to compress the stack and form the log, wherein the stack is compressed with a pressure of greater than 120 kN/m.sup.2, wherein the compression path has a length greater than the stack length, and wherein, during compression, the stack moves along the compression path with respect to the compression members.

2. The method according to claim 1, wherein the first and second transport surfaces comprise conveyor belts carried by the first and second compression members, and the method further comprises driving the conveyor belts to transport the stack along the compression path.

3. The method according to claim 1, further comprising moving the first compression member towards and into engagement with the stack only after the stack is fully located in the compression path.

4. The method according to claim 1, wherein the first compression member is moved to a position corresponding to the second spacing before a leading end of the log exits the compression path.

5. The method according to claim 1, wherein the first compression member comprises a plurality of compression elements aligned along the compression path between the input end and the output end, and the method further comprises moving a first compression element located closest to the input end from the second spacing towards the first spacing once a trailing end of the log has been transported past the first compression element; and transporting a subsequent stack of folded absorbent tissues into the compression path before the trailing end of the log has exited the output end of the compression path.

6. The method according to claim 1, further comprising applying an attachment strip to an upper tissue and/or a lower tissue of the stack prior to delivering the stack to the compression path.

7. The method according to claim 1, further comprising delivering the log from the compression path to a bander apparatus and wrapping it in a wrapping web, wherein the bander apparatus maintains the log at a compression amount corresponding to that at the output end of the compression path.

8. The method according to claim 1, further comprising sawing the log into a plurality of individual tissue bundles.

9. The method according to claim 1, wherein the stack is compressed with a pressure of greater than 160 kN/m.sup.2 and optionally greater than 225 kN/m.sup.2.

10. The method according to claim 1, wherein the tissues comprise dry crepe material or structured tissue material, and wherein the tissues are interleaved in a V, M or Z configuration.

11. The method according to claim 1, wherein the stack is transported at a speed of greater than 0.3 m/s.

12. The method according to claim 1, further comprising moving the first compression member towards the second compression member until a pre-determined pressure is achieved.

13. A compression apparatus for compressing an elongate stack of folded absorbent tissues to form a tissue log, the apparatus comprising: first and second opposed compression members, the compression members being spaced from one another and provided with respective first and second transport surfaces defining a compression path therebetween, the transport surfaces being operable to transport a stack along the compression path from an input end to an output end; and an actuator mechanism for moving the first compression member towards the second compression member from a first spacing to a second spacing wherein the stack is compressed with a pressure of greater than 120 kN/m.sup.2 to form the log, while continuing to transport the stack relative to the compression members along the compression path.

14. The apparatus according to claim 13, wherein the first transport surface is parallel to the second transport surface.

15. The apparatus according to claim 13, wherein the first transport surface comprises a conveyor belt.

16. The apparatus according to claim 13, wherein the first compression member comprises a plurality of compression elements aligned along the compression path between the input end and the output end.

17. The apparatus according to claim 16, wherein the compression elements comprise overlap portions which overlap each other such that the first transport surface is continuous between adjacent compression elements, wherein the compression elements each comprise two or more parallel conveyor belts extending side by side, with the overlap portions extending along the compression path between the conveyor belts, and wherein the actuator mechanism comprises a plurality of actuators for independently moving the plurality of compression elements between the first spacing and the second spacing.

18. A packaging system comprising the apparatus according to claim 13, and further comprising a bander apparatus aligned with the second end of the compression path for receiving the log and wrapping it in a wrapping web.

19. The system according to claim 18, wherein the bander apparatus comprises a transport path having a height corresponding to the second spacing whereby the log can be transported from the compression path through the transport path without loss in compression.

20. The system according to claim 18, further comprising a saw for cutting the log into individual tissue bundles.

21. The system according to claim 18, further comprising an attachment applying apparatus aligned with the first end of the compression path, for application of attachment elements to an upper tissue and/or a lower tissue of the stack and delivering the stack to the compression path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The features and advantages of the invention will be appreciated upon reference to the following drawings. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments of the invention and, together with the general description given above and the detailed description given below, explain the one or more embodiments of the invention.

(2) FIG. 1 is a schematic side view of an output part of a conventional tissue converting machine.

(3) FIG. 2 is a schematic view of the converting machine of FIG. 1 and a packaging system according to one embodiment.

(4) FIG. 3 is a schematic view of a second embodiment of a compression apparatus.

(5) FIG. 4 is a cross section view of one portion of the compression apparatus of FIG. 3 taken along the direction IV-IV shown in FIG. 3.

(6) FIG. 5 is an upwardly-facing view of a compression surface of the compression element of FIG. 4 taken along the direction V-V shown in FIG. 4.

(7) FIG. 6 is a schematic view of the compression apparatus of FIG. 3 in one stage of operation.

(8) FIG. 7 is a schematic view of the compression apparatus of FIG. 6 in another stage of operation.

(9) FIG. 8 is a schematic view of the compression apparatus of FIG. 6 in a further stage of operation.

(10) FIG. 9 is a schematic view of the compression apparatus of FIG. 6 in yet another stage of operation.

DETAILED DESCRIPTION

(11) FIG. 1 is a schematic side view onto an output part of a conventional tissue converting machine 1 that may be used in conjunction with a packaging system and compression apparatus as described in this application. In this embodiment, the converting machine 1 is for the production of 2-ply dry-crepe tissue 10 according to the SCA article number 140299, each of the plies being 18 gsm. The skilled person will nevertheless understand that any other suitable tissue may also be used.

(12) The converting machine 1 provides its output as two webs 11, 12 of tissue 10, that are passed around output rollers 3, 4, partially cut to define individual tissue lengths and 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.

(13) 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 roller 4 is shown above the interfolder 6 and the stacking station 8. The tissue webs 11, 12, the rollers 3, 4, the interfolder 6 and the stacking station 8 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.

(14) 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 includes 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 system 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.

(15) 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.

(16) An output 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.

(17) Operation of the packaging system 2 in the packaging of tissue bundles will now be described with reference to FIG. 2.

(18) 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.

(19) 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.

(20) 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 input end 26. So that the stack 14 can enter the compression path 27, the first compression member 31 should 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.

(21) 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/m.sup.2, 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 input end 26, to the output end 28. Once compressed in this state, the stack 14 is referred to in the following as a log 44.

(22) On exiting the output 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 should therefore 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 hotmelt adhesive. It will be understood that a one-part wrap-around wrapper could alternatively be used. The wrapper material is of virgin paper with a surface weight of 110 gsm, which is somewhat stronger than a wrapper conventionally used for loose bundles of similar weight.

(23) 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/cm.sup.3. 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 converting 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. The saw 52 may be designed to operate with 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.

(24) A second embodiment of a compression apparatus 130 is shown in FIG. 3. Compression apparatus 130 may replace the compression apparatus 30 in the packaging system 2 of FIG. 2. Like elements from that embodiment are designated with the same reference numerals preceded by 100.

(25) The compression apparatus 130 of the second embodiment differs from the previous embodiment in that the first compression member 131 is formed in five separate sections by compression elements 131 A-E. Each compression element 131 A-E has its own section of the first transport surface 133 formed by conveyor belts 162 A-E. In this embodiment, the second compression member 132 and the second transport surface 134 are constructed as a continuous element as in the first embodiment although it will be understood that they could also be interrupted.

(26) Each compression element 131 A-E is provided with its own pair of actuators 138 A-E, which are individually controlled by a central controller 170, which may be the controller for the whole packaging system 2. The controller 170 is also operatively connected to the respective transport surfaces 133, 134 and is thus able to control the relative movements and speeds and pressures of all of the components of the compression apparatus 130.

(27) The compression elements 131 A-E are also provided with overlap portions 164 A-E, which extend in the transport direction Z beyond the respective conveyor belt 162 A-E. In fact, as can be seen in FIG. 3, the overlap portions 164C on the third compression element 162C overlap with those of both the second compression element 162B and the fourth compression element 162D. In this manner, the first compression member 131 is effectively continuous between adjacent compression elements 131 A-E and the compression path 127 through the compression apparatus 130 is continuous.

(28) Also shown in FIG. 3 is a portion of bander apparatus 140. The transport path 142 of the bander apparatus 140 is also provided with overlap portions 147 which overlap with the overlap portions 164E of the fifth compression element 162E. In this manner the compression path 127 is also continuous with the transport path 142. A stack 114 is entering the input end 126 of the compression path 127 and a log 144 is leaving the output end 128 and entering the transport path 142.

(29) FIG. 4 is a section through the stack 114 along line IV-IV of FIG. 3, looking in the transport direction X. As can be seen in this view, the stack has a width W. Compression element 131A can be seen in end view to have a pair of conveyor belts 162A aligned side by side between three rail elements 166A positioned on either side of both conveyor belts 162A. The rail elements 166A, form part of the structure of the compression element 131A, supporting the conveyor belts 162A for rotation and providing structural support for the conveyor drive (not shown). The lower surfaces of the rail elements 166A lie flush with the transport surface 133 formed by the conveyor belts 162A. At their lower portions too, the rail elements 166A extend to become the overlap portions 164A.

(30) Also visible in FIG. 4, on the uppermost tissue of the stack 114 are attachment elements 122. Similar attachment elements 122 are also adhered to the lowermost surface of the stack in engagement with the second transport surface 134 of the second compression member 132. The second transport member 132 is similar in section to the first transport member 131 apart from the fact that it is not divided into individual transport elements.

(31) FIG. 5 is a view onto the transport surface 133 of the first compression element 131A in the direction V-V of FIG. 4. In this view, the extent of the rail elements 166A in the transport direction X can be seen between the overlap portions 164A at their respective ends. Conveyor belts 162A can also be seen.

(32) Operation of the compression apparatus 130 of FIGS. 3 to 5 will now be described with reference to FIGS. 6 to 9, to the extent that it differs from that of the first embodiment. In an initial stage of operation shown in FIG. 6, the compression path 127 is opened completely with all of the compression elements 131 A-E fully withdrawn. In this situation, a stack 114 having an uncompressed height H1, can enter the compression path 127 from the input end 126 and is shown located beneath the first three compression elements 131A-C.

(33) In FIG. 7, the compression stroke begins and all of the compression elements 131 A-E start to move downwards together towards the second compression member 132 under the control of the controller 170. During the compression, the stack 114 continues to move forwards, transported in the transport direction X by the transport surfaces 133, 134.

(34) In FIG. 8, compression is complete and the compression elements 131 A-E are at a second spacing with respect to the compression member 132, corresponding (approximately) to the final height H2 of the log 144. By now however the log 144 has progressed to a position under the fifth compression element 131D with its leading end 145 at the output end 128 of the compression path 127. The trailing end 143 of the log 144 has now passed the first compression element 131A, which is actuated to withdraw by the controller 170. As previously shown in FIG. 3, once the first compression element 131A has withdrawn, a new stack 114 can enter the compression path 127.

(35) FIG. 9, shows schematically the compression apparatus 130 in a further step, together with a portion of the bander apparatus 140. The log 144 has been transported further in the transport direction X through the output end 128 of the compression apparatus 130 and into the transport path 142 bander apparatus 140. As the trailing end 143 of the log 144 passes each of the compression elements 131 A-E in sequence, the controller 170 actuates the respective actuator 138 A-E to withdraw the respective compression element 131 A-E. In FIG. 9, the second compression element 131B has also been withdrawn and the stack 114 has moved forwards under it.

(36) It will be noted in the above that all of the compression elements 131 A-E move downwards together in the compression stroke. Retraction or withdrawal of each compression element 131 A-E takes place one at a time i.e. incrementally as the trailing end 143 of the log 144 passes the respective compression element. This allows a greater throughput of tissue stacks 114, since there is no necessity for a log to completely clear the compression apparatus 130 before a subsequent stack 114 enters. Once compressed, the log 144 remains compressed as it transports into the transport path 142 of the bander apparatus 140. It will be understood that although the compression elements 131 A-E are shown retracting individually, one at a time, it is also possible to retract them in groups, namely 131A, B together followed by 131C, D, E. It is also possible that only compression element 131A needs be retracted individually to achieve the desired throughput with the remaining compression elements 131 B-E retracted together. It will also be understood that different numbers of compression elements may be provided and that they may be different from each other in length.

(37) 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 scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the present application. It is intended that the specification and examples be considered as exemplary only. Many additional variations and modifications are possible and are understood to fall within the framework of the disclosure.