STACK

TECHNICAL FIELD

This invention relates to a stack of material sheets folded at least once in the longitudinal direction, which direction corresponds to the dispensing direction of the stack. The material sheets being interlinked in such a way that, when a first material sheet is extracted, a predetermined part of a subsequent material sheet is fed out.

BACKGROUND ART

A common solution for dispensing material for drying or wiping is to provide a stack of folded paper or tissue sheets in a suitable dispenser. Stacks of this type may be dispensed from different sides of the dispenser. One common solution involves a dispenser with a dispensing opening adjacent a lower surface thereof. According to one example, the stack comprises individual paper towel stacked on top of each other. A problem with this solution is that when a first material sheet is extracted, a part of a subsequent paper towel may be tangled or crumpled in the dispensing opening. Alternatively, a user may place a stack of paper towels upside down in the dispenser. In both cases withdrawal of a subsequent paper towel is made difficult. According to a further example, the stack comprises interlinked paper towels. When a first towel is extracted, a predetermined part of a subsequent towel is supposed to be fed out. A problem with this solution is that the interlinking function is either too weak, so that the subsequent towel is not fed out, or that the interlinking function is too strong, so that more than one towel is withdrawn.

An alternative solution involves a dispenser with a dispensing opening adjacent an upper surface thereof. When a first material sheet is extracted, a predetermined part of a subsequent material sheet is supposed to be fed out. A problem with this solution is that the interlinking function is either too weak, so that the subsequent towel falls back into the dispenser, or that the interlinking function is too strong, so that more than one towel is withdrawn.

It is an object of the present invention to solve the above problems by providing an improved stack of material sheets for use in a dispenser arrangement for dispensing material sheets.

DISCLOSURE OF INVENTION

The above objects are achieved by means of a stack of material sheets according to claim 1 and its dependent claims.

In the subsequent text the terms “longitudinal” and “transverse” are used to define the relative position of a material sheet relative to the direction of feed of the sheet. The direction of feed coincides with the longitudinal axis of the material sheets as they are withdrawn from a dispenser. These terms are not necessarily related to the relative size of the side edges of a material sheet. Similarly, the terms “preceding” “and “subsequent” or “front” and “rear” are used to define the relative position of a material sheet in relation to adjacent sheets in relation to the direction of feed of the sheets.

A stack made from an assembled web of discrete sheets arranged according to any of the embodiments described below may be a stack where the material sheets are extracted from the bottom or the top of the stack.

According to a preferred embodiment, the invention relates to a stack of discrete material sheets, which material sheets have a longitudinal direction and a transverse direction. The material sheets forming the stack are placed with their transverse end portions partially overlapping. The partially overlapping material sheets may be folded at least once in the longitudinal direction to form an assembled web, wherein the longitudinal direction corresponds to the dispensing direction of the material sheets forming the stack. The assembled web may comprise a single line of material sheets cut from a continuous length of material. Alternatively two single lines of material sheets may be interposed on each other to form a single web. A longitudinal fold line is preferably, but not necessarily arranged so that the material sheets are folded in half. The assembled web may then be folded along fold lines in predetermined location in the transverse direction to form said stack of material sheets. The material sheets are preferably interlinked in such a way that, when a first material sheet is extracted, a predetermined part of a subsequent material sheet is fed out.

According to a further preferred embodiment, the material sheets may be folded twice in the longitudinal direction of the said material sheets. Preferably, the distance between the parallel fold lines is at least half the width of a sheet in the transverse direction. This type of folding arrangement is sometimes referred to as a C-fold and is preferably, but not necessarily, performed when the material sheets are placed in an overlapping relationship.

According to a first alternative embodiment of the invention the degree of overlap between adjacent material sheets forming a stack may be constant. Also, each subsequent sheet is placed with its transverse front portion arranged on top of the transverse rear portion of a preceding sheet throughout an assembled web, or alternatively with said transverse front portion arranged below the transverse rear portion of a preceding sheet throughout an assembled web. This may be achieved by cutting a continuous web into sheets that are arranged end-to-end and then displacing adjacent sheets relative to each other in the longitudinal direction to form an overlap.

According to a first example of the first alternative embodiment, the degree of overlap is 25% of the length of an unfolded material sheet in its longitudinal direction. The assembled web is preferably, but not necessarily, folded in alternating directions, so that the assembled web assumes a zig-zag shape allowing it to form a stack. In the folded stack, every second material sheet has a transverse fold line dividing the material sheet in half. The folding process may be initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or by locating said front edge halfway between and parallel to two opposing outer sides of the resulting stack. The width of the resulting stack is substantially equal to half the length of a material sheet in its longitudinal direction.

Alternatively, the assembled web is folded in alternating directions so that every fourth material sheet extends across the stack in its entire length. The folding process may be initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or by locating said front edge at ¼, ½ or ¾ of the distance between and parallel to two opposing outer sides of the resulting stack. In this case, the width of the resulting stack is substantially equal to the length of a material sheet in its longitudinal direction.

According to a second example of the first alternative embodiment, the degree of overlap is 33% of the length of an unfolded material sheet in its longitudinal direction. The assembled web is preferably, but not necessarily, folded in alternating directions so that every material sheet extends across the stack along a third of its entire length. The folding process may be initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or by locating said front edge halfway between and parallel to two opposing outer sides of the resulting stack. The width of the resulting stack is substantially equal to two thirds of the length of a material sheet in its longitudinal direction.

According to a third example of the first alternative embodiment, the degree of overlap is 50% of the length of an unfolded material sheet in its longitudinal direction. The assembled web is preferably, but not necessarily, folded in alternating directions so that every material sheet extends across the stack along half of its entire length. The folding process may be initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack. The width of the resulting stack is substantially equal to half the length of a material sheet in its longitudinal direction.

According to a second alternative embodiment of the invention the degree of overlap between adjacent material sheets forming a stack may be variable. As in the first alternative embodiment, each subsequent sheet is placed with its transverse front portion arranged on top of the transverse rear portion of a preceding sheet throughout an assembled web, or alternatively with said transverse front portion arranged below the transverse rear portion of a preceding sheet throughout an assembled web. This may be achieved by cutting a continuous web into sheets that are arranged end-to-end and then displacing adjacent sheets a variable increasing or decreasing distance relative to each other in the longitudinal direction to form a variable overlap.

A stack of material sheets according to the invention is preferably, but not necessarily arranged in a substantially vertical direction. When discrete material sheets are dispensed from the bottom of the stack, the overlap may be constant from top to bottom. However, depending on parameters such as stack size, surface structure, friction and/or physical sheet size it may be desirable to provide the stack with a continuously decreasing overlap from bottom to top. For instance, as the height of the stack is reduced as the material sheets are removed, the weight of the stack resting on the lowermost material sheet is reduced. Consequently, the force required to withdraw a sheet will decrease, requiring less overlap. In order to compensate for this the overlap may be increased towards the bottom of the stack. The overlap may be selected in the range 25-50% of the length of an unfolded material sheet in its longitudinal direction, depending on the properties of the material sheets.

Similarly, when discrete material sheets are dispensed from the top of the stack, the overlap may be constant from top to bottom. In some cases it may, however, be desirable to provide the stack with a continuously increasing overlap from top to bottom depending on parameters such as stack and dispenser size, surface structure, friction and/or physical sheet size. For instance, as the height of the stack is reduced as the material sheets are removed, the distance between the top of the stack and a dispensing opening at the top of the dispenser will increase. In order to compensate for this, and to ensure that extraction a preceding sheet will cause a subsequent sheet to be fed out, the overlap may be increased towards the bottom of the dispenser. As stated above, the overlap may be selected in the range 25-50% of the length of an unfolded material sheet in its longitudinal direction, depending on the properties of the material sheets.

A stack of material sheets having a predetermined size and a varying overlap may be arranged to fit dispensers with a dispensing opening located at the top or at the bottom of the dispenser. Provided that the direction of increasing overlap is indicated on the stack, the same stack may be used in both types of dispenser. A user is simply required to identify and place the end of the stack having the largest overlap away from the dispensing opening.

After the material sheets have been placed in an overlapping relationship forming an assembled web, as described above, a folding process is carried out in order to form the assembled web into a stack. This is achieved by folding the assembled web along transverse fold lines in predetermined locations. When the overlap is variable, the locations of the transverse fold lines are selected to achieve a predetermined stack width.

According to a second preferred embodiment of the invention the overlap between adjacent material sheets forming a stack may be formed by placing two parallel lines of individual material sheets on top of each other. As opposed to the first alternative embodiment, each alternate sheet of an assembled web is placed with its transverse rear portion arranged on top of a transverse front portion of a subsequent sheet, and with its transverse front portion on top of the transverse rear portion of a preceding sheet throughout the said web. This may be achieved by cutting a continuous web into a first line of sheets and then placing a cut, second line of sheets on top of said first line of sheets. Each line of sheets of the respective first and second line may be arranged end-to-end or at a predetermined fixed or variable distance between opposing ends of consecutive material sheets.

The interlinking may be achieved by at least partially overlapping adjacent ends of the material sheets. The material sheets may be interlinked by an overlap of at least 25% of the length of an unfolded material sheet in its longitudinal direction. An overlap between 25% and 50% will require a separation of the individual sheets in each line of sheets prior to, or subsequent to, the assembly of the first and second lines of sheets. The overlap may be up to and including 50% of the length of an unfolded material sheet in the longitudinal direction. A 50% overlap merely requires indexing of the cut second line of sheets in the longitudinal direction prior to placing it on top of the cut first line of sheets. The overlap may be constant, but can also be variable depending on predetermined parameters.

The first and second lines of sheets may be placed on top of each other with their respective side edges coinciding in a vertical plane, that is, with a 100% transverse overlap. The transverse overlap may be selected between 30% and 100% of the transverse width of the material sheets.

According to a first example of the second preferred embodiment, the degree of longitudinal overlap is 50% of the length of an unfolded material sheet in its longitudinal direction. The transverse overlap may in this example be 100% of the transverse width of the material sheets.

The partially overlapping first and second lines of material sheets may be folded at least once in the longitudinal direction to form an assembled web, wherein the longitudinal direction corresponds to the dispensing direction of the material sheets forming the stack. Such a longitudinal fold line is preferably, but not necessarily arranged so that the material sheets are folded in half. The assembled web may then be folded along fold lines in predetermined locations in the transverse direction to form said stack of material sheets.

According to a second example of the second preferred embodiment, the degree of overlap is 50% of the length of an unfolded material sheet in its longitudinal direction. The transverse overlap may in this example be 50% of the transverse width of the material sheets.

Preferably, the partially overlapping material sheets may be folded twice in the longitudinal direction of the said material sheets. The distance between the parallel fold lines may be at least half the width of each sheet in the transverse direction. The assembled web can be achieved by folding the outer, non-overlapping edge of the lower line of material sheets inwards over and fully covering the overlap. Subsequently, the outer, non-overlapping edge of the upper line of material sheets inwards over and fully covering the first folded edge and the overlap. Alternatively the assembled web is created by simultaneously folding the outer edge of the lower line of material sheets upwards and inwards, and the outer edge of the upper line of material sheets downwards and inwards This type of folding arrangement creates an assembled web comprising consecutive partially overlapping pairs of substantially V-shaped, opposed and interleaved material sheets.

The same effect, using partial overlap in the transverse direction may be achieved at other degrees of overlap. For instance, with a transverse overlap of ⅓ of the transverse width, the sheets on either side of the overlap may be folded in half towards to create an assembled web. Alternatively, with a transverse overlap of ⅔ of the transverse width, the sheets on either side of the overlap may be folded along a longitudinal fold line located at approximately ⅓ of the width from the outer edges of the respective of the first and second line of sheets to cover a part of the overlap and create an assembled web.

The examples described above for the second preferred embodiment may also apply to examples using a variable overlap in the longitudinal direction.

The assembled web of longitudinally and transversely overlapping material sheet may then be folded in the same way as described above for a single line of material sheets in order to form a stack.

In addition to the overlap described above, adjacent material sheets may be interlinked by one or more alternative arrangements in order to achieve a desired friction between at least predetermined parts of the contacting surfaces of said material sheets. By modifying the friction between adjacent surfaces it is possible to ensure that a first material sheet withdrawn from a dispenser will feed out a predetermined portion of a subsequent material sheet. The amount of friction modification is dependent on the quality and surface structure of the material sheets used. For sheets having a relatively rough surface structure the friction resulting from the overlapped and folded relationship between adjacent sheets may be sufficient. In this case, varying the amount of overlap may be sufficient to achieve the desired result. On the other hand, for material sheets having a relatively smooth surface structure a friction enhancing process and/or arrangement may be required to ensure that a portion of a subsequent material sheet is fed out by a preceding material sheet.

One alternative way of modifying the friction between overlapping sections of material sheets may be an embossing on at least a portion of the overlap. Such an embossing may be carried out by passing an assembled web of pre-cut and partially overlapping material sheets through a nip between a pair of cylindrical rolls. The rolls may be arranged to apply a desired amount of pressure onto at least a portion of the overlapping sections and/or to apply pressure over a predetermined surface area of each overlapping section. One or both rolls may be patterned in order to emboss the compressed portions to a predetermined degree.

According to a further alternative way of modifying the friction, the material sheets may be interlinked by a friction enhancing coating applied onto at least a portion of the overlapping sections between adjacent sheets. A coating of this type may be applied to at least a portion of one or both ends of each sheet in an assembled web of material sheets. The coating may be applied by a single roller or a pair of rollers, or by spraying. Coatings of this type may modify the surface friction of at least one of the surfaces in an overlapping section. The coating may also create a brittle bonding between contacting surfaces.

According to a similar alternative way of modifying the friction, the material sheets may be interlinked by a rubber emulsion or an adhesive on at least a portion of the overlap between adjacent sheets. Suitable adhesives may include liquid, curable adhesives, wax based hot-melt adhesives, friction hot-melt adhesives, adhesives with low adhesion and high cohesion, or a weak adhesive applied as multiple spots, such as starch or polyvinyl alcohol. Such adhesives may be applied in the same way as the coatings described above. Such a coating or adhesive may be applied prior to, preferably immediately prior to, the sheets being displaced into their overlapping positions.

Non-limiting examples of suitable materials for sheets for this purpose are suitable tissue products, such as wet crêpe dry crêpe or through-air-dried (TAD) materials, which products contain mostly paper pulp. The material sheets may also be made from a suitable type of non-woven or equivalent wiping material. The non-woven materials may be spunbond, thermobond, chemically bonded, spunlaced, spunlaid, carded; air laid or entangled non-wovens. The non-woven materials may comprise suitable natural or manmade fibres, containing cotton or rayon, polypropylene (PP), polyethylene (PE), polyether sulfone (PES), polyethylene terephthalate (PET), polyester, polyamide, bi-component fibres (Bico) or pulp fibres.

Individual sheets in the line or lines of material sheets cut from a continuous web may be separated by a straight, transverse cut at right angles to the longitudinal axis of the respective line of sheets. According to an alternative example, the transverse cut may have the shape of a curve having at least one apex, where the apex forms a leading or trailing edge of each material sheet in the line. The apex may preferably, but not necessarily, coincide with a fold line and the curve may preferably, but not necessarily, be symmetrical about an axis coinciding with the said fold line in the plane of the material sheet.

For example, for single line of material sheets placed in a constant or variable overlapping relationship the cut may have an approximate sinusoidal shape, with a single apex coinciding with a central fold line. Alternatively, if the assembled web has two fold lines, such as a C- or Z-fold, the cut may comprise a substantially sinusoidal curve with an apex coinciding with each fold line. The shape of the cut and the location one the at least one apex may also be applied to assembled webs comprising two lines of material sheets. The shape of the curve is not limited to sinusoidal curves, but may be given any suitable shape having an apex at leading edge of each material sheet.

Advantages of the transverse cut are that it makes the assembled web easier to handle during the production stage and that it provides an improved, easy to grasp portion when a subsequent material sheet is pulled out and presented to a user.

A dispenser for use with a stack according to the invention may be provided with a dispensing opening through which the material sheets are dispensed. The dispenser may be a wall mounted type dispenser with a dispensing opening in at least a part of a lower surface. Alternatively, the dispenser may comprise a box, such as a cardboard box or similar, with a dispensing opening in at least a part of an upper surface. However, the stack according to the invention is not limited for use in the above types of dispensers.

BRIEF DESCRIPTION OF DRAWINGS

In the following text, the invention will be described in detail with reference to the attached drawings. These schematic drawings are used for illustration only and do not in any way limit the scope of the invention. In the drawings:

FIG. 1 shows a lower perspective view of a dispenser provided with a stack of discrete material sheets according the invention;

FIG. 2 shows a plan view of a first part of a process for making a stack of material sheets according to a preferred embodiment of the invention;

FIG. 3A shows a plan view of a folding process occurring subsequent to the process of FIG. 2;

FIG. 3B shows a plan view of an alternative folding process occurring subsequent to the process of FIG. 2;

FIG. 4 shows an alternative longitudinal folding procedure occurring subsequent to the process of FIG. 2, according to a further preferred embodiment.

FIG. 5 shows a stack of material sheets folded according to a first example of a first alternative embodiment;

FIG. 6 shows a stack of material sheets folded according to an alternative of the first example;

FIG. 7 shows a stack of material sheets folded according to a second example; and

FIG. 8 shows a stack of material sheets folded according to a third example.

FIGS. 9A-B show a plan view of a first part of a process for making a stack of material sheets according to first example of a second preferred embodiment of the invention;

FIGS. 10A-B show a plan view of a first part of a process for making a stack of material sheets according to second example of a second preferred embodiment of the invention; and

FIGS. 11A-B show a plan view of a part of a process for making a stack of material sheets separated by a curved transverse cut.

EMBODIMENTS OF THE INVENTION

FIG. 1 shows a lower perspective view of a dispenser 11 provided with a stack 12 (indicated with dash-dotted lines) of discrete material sheets. The stack 12 comprises discrete material sheets assembled and folded into a stack in accordance with the invention. The discrete material sheets are interlinked in such a way that, when a first material sheet 13 is extracted by a user, a predetermined part of a subsequent material sheet 14 is pulled out of the dispenser 11 by the first material sheet 13. The dispenser 1 is provided with a dispensing opening 15 through which the material sheets are dispensed.

FIG. 2 shows a plan view of a first part of a process for making a stack of material sheets according to a preferred embodiment of the invention. The material sheets used in the process have been pre-cut from a continuous web of material (not shown) in a first step. The resulting material sheets have a longitudinal direction and a transverse direction. The process involves feeding an assembled web of discrete material sheets 21, placed end to end in their longitudinal direction, through an apparatus 22 arranged for displacing the discrete material sheets 21 so that an overlap 23 is created by adjacent material sheets in their longitudinal direction. This is achieved by controlling the relative speed of a first and a second conveyor 24, 25. The apparatus 22 for displacing the discrete material sheets 21 is provided with a device (not shown) for controlling the vertical position of the front edge of a material sheet relative to the rear edge of a preceding sheet is provided at the location where the material sheets are passed from the first to the second conveyor. In the example shown, the length X₂of the overlap 23 is ⅓ of the length X₁of an unfolded material sheet 21. The overlap 23 can be increased by slowing down the second conveyor 25 to a predetermined speed relative to the first conveyor 24, and vice versa. As can be seen from the example in FIG. 2, the front portion of each material sheet is positioned on top of a preceding sheet. Subsequently, the assembled web of overlapping material sheets 21 is fed through an apparatus 31 arranged to fold the sheets 21 along a fold line coinciding with the longitudinal centreline C_Lof the material sheets 21, as shown in FIG. 3A. According to the example shown in FIG. 3A, the left hand side 32 of each material sheet is displaced upwards and folded over the right hand side 33 of the material sheet 21, as indicated by the arrow B, as seen in the direction of feed, as indicated by the arrow C, of the assembled web of material sheets 21. The overlapping and folded material sheets 21 can then be fed as a continuous assembled web 34 between opposing rollers and/or conveyors (not shown) and is subsequently subjected to a folding operation.

According to an alternative first embodiment, the front portion of each material sheet is positioned on top of a preceding sheet in the same way as described in connection with FIG. 2 above. The subsequent longitudinal folding procedure is similar to the procedure described in FIG. 3A above. Hence, the assembled web of overlapping material sheets 21 is fed through an apparatus 31 arranged to fold the sheets 21 along a fold line coinciding with the longitudinal centreline C_Lof the material sheets 21. The left hand side 32 of each material sheet is displaced downwards and folded under the right hand side 33 of the material sheet 21, as indicated by the arrow B, as seen in the direction of feed, as indicated by the arrow C, of the assembled web of material sheets 21. Hence, the difference between the folding processes shown in FIGS. 3A and 3B respectively is the direction of the arrow B. The overlapping and folded material sheets 21 can then be fed as a continuous assembled web 34 towards a subsequent folding operation.

FIG. 4 shows an alternative longitudinal folding procedure, according to a further preferred embodiment, taking the place of the procedure described in FIGS. 3A and 3B. According to this alternative procedure, the material sheets are folded twice in the longitudinal direction of the said material sheets. The assembled web of overlapping material sheets 21 is fed through an apparatus 41 arranged to fold the sheets 21 along a first and a second fold line F₁, F₂, that are parallel to the longitudinal centreline C_Lof the material sheets 21. In FIG. 4, the left hand side 42 of each material sheet is displaced upwards and folded inwards along the first fold line F₁, as indicated by the arrow B₁, as seen in the direction of feed, as indicated by the arrow C, of the assembled web of material sheets 21. At the same time the right hand side 43 of each material sheet is displaced upwards and folded inwards along the second fold line F₂, as indicated by the arrow B₂. Preferably, the distance X₃between the parallel first and second fold lines F₁, F₂is at least half the length X₄of a material sheet in the transverse direction of the material sheets 21. In the schematic example shown, the first and second fold lines F₁, F₂are placed symmetrically on both sides of the centreline with the distance X₃being approximately 55% of the length X₄of a material sheet. The overlapping and folded material sheets 21 can then be fed as a continuous assembled web 44 towards a subsequent folding operation. The folding operation will be described in further detail below. Alternatively, the same assembled web as shown in FIG. 4 can be used, wherein the folding is carried out in the opposite direction of the arrows B₁and B₂, that is, downwards and inwards in the plan view shown.

The first and second fold lines F₁, F₂can also be placed asymmetrically relative to the longitudinal centreline C_LHowever, the distance X₃between the parallel first and second fold lines F₁, F₂should preferably not exceed half the length X₄of a sheet. This type of folding arrangement is sometimes referred to as a C-fold and is preferably, but not necessarily, performed when the material sheets are placed in an overlapping relationship.

According to a first alternative embodiment of the invention the degree of overlap between adjacent material sheets forming a stack may be constant.

FIG. 5 shows a stack 51 of material sheets according to a first example of the first alternative embodiment. In this example the degree of overlap is 25% of the length of an unfolded material sheet in its longitudinal direction. An assembled web is folded in alternating directions, so that the assembled web assumes a zig-zag shape allowing it to form a stack 51. In the folded stack 51, every second material sheet 52 has a transverse fold line 53 dividing the material sheet 52 in half. The folding process is initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or, alternatively, by locating said front edge halfway between and parallel to two opposing outer sides of the resulting stack. The width of the resulting stack is substantially equal to half the length of a material sheet in its longitudinal direction.

FIG. 6 shows an alternative way of folding an assembled web with an overlap of 25% into a stack 61, according to the first example. The assembled web is folded in alternating directions so that every fourth material sheet 62 extends across the stack in its entire length. The folding process is initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or, alternatively, by locating said front edge at ¼, ½ or ¾ of the distance between and parallel to two opposing outer sides of the resulting stack. In this case, the width of the resulting stack is substantially equal to the length of a material sheet in its longitudinal direction.

FIG. 7 shows a stack 71 of material sheets according to a second example, the degree of overlap is ⅓ of the length of an unfolded material sheet in its longitudinal direction. The assembled web is folded in alternating directions so that every material sheet 72 extends across the stack along a third of its entire length. The folding process is initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack, or, alternatively, by locating said front edge halfway between and parallel to two opposing outer sides of the resulting stack. The width of the resulting stack is substantially equal to a third of the length of a material sheet in its longitudinal direction.

FIG. 8 shows a stack 81 of material sheets according to a third example, the degree of overlap is 50% of the length of an unfolded material sheet in its longitudinal direction. The assembled web is preferably, but not necessarily, folded in alternating directions so that every material sheet 82 extends across the stack along half of its entire length. The folding process is initiated by locating a front transverse edge of a material sheet adjacent and parallel to an outer side of the resulting stack. The width of the resulting stack is substantially equal to half the length of a material sheet in its longitudinal direction.

According to a second alternative embodiment of the invention the degree of overlap between adjacent material sheets forming a stack may be variable. The overlap may be selected in the range 25-50% of the length of an unfolded material sheet in its longitudinal direction, depending on the properties of the material sheets. After the material sheets have been placed in an overlapping relationship forming an assembled web, as described above, a folding process is carried out in order to form the assembled web into a stack. This is achieved by folding the assembled web along transverse fold lines in predetermined locations. When the overlap is variable, the locations of the transverse fold lines are selected to achieve a predetermined stack width. In order to place such a stack in a dispenser, that end of the stack having the largest overlap is placed away from the dispensing opening.

The above mentioned transverse folding is performed prior to a longitudinal folding step. The longitudinal folding step involves folding the sheets along a fold line coinciding with the longitudinal centreline of the material sheets, as described in connection with FIGS. 3A and 3B above.

FIG. 9A shows a plan view of a first part of a process for making a stack of material sheets according to a first example of a second preferred embodiment of the invention. The process involves feeding two lines of individual material sheets in parallel, in the direction of the arrows A₁and A₂, and placing on top of each other. This is achieved by cutting continuous webs of material (not shown) into a first line L₁of sheets 91 and then placing a cut, second line L₂of sheets 92 on top of said first line of sheets. In this example, the sheets 91, 92 of the respective first and second lines L₁, L₂have the same length X₁and are arranged end-to-end, with the material sheets 92 of the second line L₂of sheets indexed to form an overlap 93 between subsequent sheets (FIG. 9B). The overlap 93 has a length X₂corresponding to 50% of the length X₁of a material sheet. Each alternate sheet of overlapping web is placed with its transverse rear portion arranged on top of a transverse front portion of a subsequent sheet, and with its transverse front portion on top of the transverse rear portion of a preceding sheet throughout the said web.

As can be seen in FIG. 9B, the first and second lines L₁, L₂of sheets 91, 92 have been placed on top of each other with their respective side edges coinciding in a vertical plane, that is, with a 100% transverse overlap Y. The second part of the process involves feeding the lines L₁, L₂of overlapping material sheets 91, 92 in the direction of the arrow A₃through an apparatus 94 and folding it in half in the direction of the arrow B along a central fold line C_Linto an assembled web. The assembled web can then be folded into a stack in the same way as the stack described in FIG. 8 above.

Alternatively, two lines of individual sheets arranged partially overlapping in the longitudinal direction as shown in FIG. 2 can be used. The folding can then be carried out in the direction of the arrow B as shown in FIG. 9B or in the opposite direction said arrow.

FIG. 10A shows a plan view of a first part of a process for making a stack of material sheets according to a second example of the second preferred embodiment of the invention. As in the first example, individual sheets 101, 102 of a respective first and second line L₁, L₂are fed in the direction of the arrow A and are arranged end-to-end, with the material sheets 102 of the second line L₂of sheets indexed to form an overlap of 50% between subsequent sheets in the longitudinal direction. The longitudinal overlap X₂in this example is 50% of the longitudinal length X₁of the material sheets. The transverse overlap Y₂in this example is 50% of the transverse width Y₁of the material sheets. The process involves feeding the lines L₁, L₂of overlapping material sheets 101, 102 in the direction of the arrow A through a first apparatus 104 and folding it in the direction of the arrow B along a first fold line F₁. The first fold line F₁coincides with the overlapping side edge 105 of the second line L2. During folding a first outer, non-overlapping edge 106 of the lower, first line L₁of material sheets, which edge 106 is folded inwards over and fully covering the transverse overlap Y₂.

As shown in FIG. 10B, the web comprising partially overlapping and folded material sheets 101, 102 shown in FIG. 10A are fed in the direction of the arrow A through a second apparatus 107 and folding the web in the direction of the arrow C along a second fold line F₂. During folding a second outer, non-overlapping edge 108 of the upper, second line L₂of material sheets is folded inwards over and fully covering the overlap Y₂. The assembled web can then be folded into a stack in the same way as the stack described in FIG. 8 above.

Alternatively the assembled web is created by simultaneously folding the outer edge of the lower line of material sheets upwards and inwards, and the outer edge of the upper line of material sheets downwards and inwards. Both folding arrangements create an assembled web comprising consecutive partially overlapping pairs of substantially V-shaped, opposed and interleaved material sheets.

The same effect, using partial overlap in the transverse direction, may be achieved at other degrees of overlap. For instance, with a transverse overlap of ⅓ of the transverse width, the sheets on either side of the overlap may be folded in half towards to create an assembled web. Alternatively, with a transverse overlap of ⅔ of the transverse width, the sheets on either side of the overlap may be folded along a longitudinal fold line located at approximately ⅓ of the width from the outer edges of the respective of the first and second line of sheets to cover a part of the overlap and create an assembled web. The examples described above for the second preferred embodiment may also apply to examples using a variable overlap in the longitudinal direction.

In the above embodiments, individual sheets in the line or lines of material sheets cut from a continuous web are separated by a straight, transverse cut at right angles to the longitudinal axis of the respective line of material sheets. FIG. 11A shows an alternative example, where a transverse cut 110 has the shape of a sinusoidal curve with an apex 111. The apex 111 forms a leading edge of each material sheet 112 in a line L of sheets. The process involves feeding a web of discrete material sheets 112, placed end to end in their longitudinal direction, through an apparatus 113 arranged for displacing the discrete material sheets 112 so that an overlap 114 is created by adjacent material sheets in their longitudinal direction. The direction of feed is indicated by the arrow A. This is achieved by controlling the relative speed of a first and a second conveyor 115, 116. The apparatus 113 for displacing the discrete material sheets 112 is provided with a device (not shown) for controlling the vertical position of the leading edge of a material sheet relative to the rear edge of a preceding sheet is provided at the location where the material sheets are passed from the first to the second conveyor. In the example shown, the length X₂of the longitudinal overlap 114 is ⅓ of the length X₁of a material sheet 112.

As shown in FIG. 11B, the apex 111 of the sinusoidal curve in FIG. 11A coincides with a fold line F and the sinusoidal curve is symmetrical about a central axis coinciding with the said fold line F in the plane of the material sheets. The web of overlapping material sheets 112 is fed through a second apparatus 117 arranged to fold the sheets 112 along a fold line F coinciding with the longitudinal centreline C_Lof the material sheets 112, as shown in FIG. 11A. According to the example shown in FIG. 11B, the left hand side 118 of each material sheet is displaced upwards and folded over the right hand side 119 of the material sheet 112, as indicated by the arrow B, as seen in the direction of feed, as indicated by the arrow A, of the assembled web of material sheets 112. The overlapping and folded material sheets 112 can then be fed as a continuous assembled web 120 between opposing rollers and/or conveyors (not shown) and is subsequently subjected to a folding operation.

In the above embodiment, the apex is described as forming a leading edge. However, the apex can also form a trailing edge at the rearmost end of each material sheet in a line of sheets.

In addition to the overlap and folding described above, adjacent material sheets can be interlinked by one or more alternative arrangements in order to achieve a desired friction between contacting surfaces of said material sheets.

One alternative way of modifying the friction between overlapping sections of material sheet is the use of an embossing step performed on at least a portion of the overlap. According to one example the embossing is carried out by passing the assembled web of pre-cut and partially overlapping material sheets through a nip between a pair of cylindrical rolls. The rolls may be arranged to apply a desired amount of pressure onto at least a portion of the overlapping sections and/or to apply pressure over a predetermined surface area of each overlapping section. Alternatively, a pair of rolls can apply continuous pressure along the edges of the assembled web of sheets, allowing the said edges to be provided with a decorative pattern that provides enhanced friction in the region of each overlap. In the above examples, one or both rolls may be patterned in order to emboss the compressed portions to a predetermined degree.

Embossing or compression of selected portions of adjacent material sheets can be carried out after the overlapping procedure shown in FIG. 2, or after the folding procedures shown in FIG. 3A, 3B or 4, prior to the transverse folding operation.

According to a further alternative way of modifying the friction, the material sheets can be interlinked by a friction enhancing coating applied onto at least a portion of the overlapping sections between adjacent sheets. A coating of this type is applied to at least a portion of one or both ends of each sheet in, an assembled web of material sheets, prior to the sheets being displaced into their overlapping positions. The coating is applied by a single roller or a pair of rollers, or by spraying. Coatings of this type will modify the surface friction of at least one of the surfaces in an overlapping section. The coating preferably creates a brittle or crystalline bonding between contacting surfaces, which bond will break as a preceding material sheet is withdrawn from the dispenser.

According to a similar alternative way of modifying the friction, the material sheets can be interlinked by an adhesive on at least a portion of the overlap between adjacent sheets. Suitable adhesives include liquid, curable adhesives or hot-melt adhesives. Such adhesives are applied in the same way as the coatings described above. As stated above, the adhesive is applied prior to the sheets being displaced into their overlapping positions.

The invention is not limited to the above embodiments, but may be varied freely within the scope of the appended claims.

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