EP0275231B1 - Method and apparatus for consolidating web materials, in particular a fibre web - Google Patents

Abstract

Fibre webs are consolidated and embossed using pairs of rotating calender rolls between which the fibre web passes. The calender rolls have been provided with raised discrete areas which form a surface pattern and determine the pattern which is embossed on the fibre web. To emboss different patterns, depending on the desired constitution and stiffness of the fibre web, different calender rolls are available, but it is very inconvenient to interchange the calender rolls. To avoid this disadvantage, the calender rolls of the novel apparatus are each driven at a synchronous speed and it is made possible to alter the speed of one of the rolls for a short time, so that the surface patterns of the two calender rolls become displaced relative to one another. This creates different degrees of overlap between mutually opposite pairs of raised areas, so that it is possible to set different embossing patterns in the course of continuous operation without it being necessary to replace the calender rolls. <IMAGE>

Description

The invention relates to a method for solidifying and / or for thermal bonding and / or for embossing according to the preamble of claim 1.

Devices of this type with calender rolls are known to be used for the treatment and processing of web-shaped materials such as non-woven fabrics in order to bring about consolidation, aesthetic embossing or thermal bonding of the non-woven fabric. One or both rollers are heated, and furthermore, the one roller or both rollers can be provided with a surface pattern which is formed by raised, discrete points located on the circumference of the calender rollers.

The rotating calender rolls form a gap between them in which the nonwoven fabric is guided under pressure. In this case, the degree of coverage between opposing pairs of raised, discrete points forms an embossing surface which determines the pattern of the finished nonwoven fabric, and a connection or consolidation takes place on the embossing surfaces.

A process described so far has become known from DE-OS 21 07 887, using two calender rolls, each of which has a surface pattern of heatable, insulated, raised discrete locations, the calender rolls being rotated in such a way that the raised ones Places to be kept in line with each other.

As a result of the surface patterns of the calender rolls used, this results in each case in the known method or in the known device for the nonwoven fabric a very specific embossing pattern, and the nonwoven fabric therefore has a very specific embossing area, which is given in percent.

If the end product is to be a soft material, a relatively small embossing area is sufficient, whereas a larger embossing area must be selected for stronger materials. Depending on the requirements of the desired end product, it is therefore necessary to use different calender rolls according to the desired embossing surface and to replace the previously used calender rolls with new ones.

This exchange of calender rolls for different webs with different embossing surfaces has an extremely disadvantageous effect in practice because it involves a great deal of time and a longer production interruption. The calender rolls have a considerable weight and it takes a lot of time to replace the calender rolls.

In order to counter this effort and to enable a faster change to achieve different embossing surfaces, one has already gone over to to provide several individual calender stands, each with two calender rolls one behind the other, each calender stand being equipped with a smooth roll and a grain roll, each with a different surface pattern. Here, the different grain rollers can be used relatively quickly as required. However, this solution is also very complex because of the multiple grain rollers, and the multiple calender stands also take up a not inconsiderable amount of space.

Therefore, the most common method is still used in practice, if the embossing pattern or the embossing surface needs to be changed, to stop the production process and to carry out the time-consuming change of the calender rolls.

This is where the invention intervenes, which is based on the object of creating a method - and a device suitable for carrying out the method - which enables a rapid and thus extremely economical change from a first to a desired different embossing pattern or to another percentage The embossing area enables a continuous change in the percentage of the embossing area during the process Production process should be possible within wide limits.

This object is achieved by the invention in the method mentioned in the preamble of claim 1 by the features specified in the characterizing part. Devices for carrying out the new method are specified in claims 4 and 10.

The invention is based on driving the two calender rolls at an identical speed, so that a very specific predetermined degree of coverage or a very specific percentage embossing area is achieved. In addition, there is provision for briefly interrupting the synchronous running of the two calender rolls and practically bringing about a brief phase shift between the individual revolutions in order to then immediately switch back to the identical synchronous speed of the two calender rolls.

The short phase shift also results in a different degree of coverage, since different areas of the raised discrete points now lie on top of one another than before. This also changes the percent embossing area. So it can be easier Depending on the requirements of the end product, the percentage embossing area can be changed, which is a particularly important advantage of the invention during operation. A laborious exchange of the calender rolls to adapt to different embossing surfaces of the desired end product is no longer necessary. While the known devices and methods always pay close attention to the exact synchronism of the two calender rolls, the invention, on the other hand, treats the surprising way of briefly interrupting this synchronism and then restoring it. The associated displacement of the surfaces which overlap when the calender rolls roll off results in a desired new embossing pattern without the need to replace the calender rolls themselves. Rather, these can be used unchanged.

It is customary to use calender rolls with a so-called bombage, that is to say a slightly curved outer circumferential line. In this case, the calculated bombage can be distributed equally between the two calender rolls. However, the invention is not limited to this. When using cylindrical calender rolls, the different embossings can be made Areas in addition to the method described so far can also be achieved in that the two calender rolls are arranged displaceably in the axial direction. In this case, the synchronous speed of the two calender rolls can be maintained; the degree of coverage changes due to the axial displacement of one calender roll relative to the other.

A drive unit with an adjustment gear is preferably provided for driving the calender rolls at synchronous speed, which enables an angular displacement of one calender roll relative to the other calender roll.

This has the advantage that only a single motor has to be used for the drive. The drive, consisting of motor and gearbox, expediently forms a unit. In this case, the transmission has an input shaft for the motor, two output shafts for the two calender rolls, the differential adjustment gear being integrated into the main transmission and being operable manually or with a servomotor via an adjustment shaft.

He further advantageous embodiments of the invention result from the subclaims and the drawing.

• Fig. 1 eine Prinzipdarstellung zweier von einem einzigen Motor über ein Getriebe angetriebener Kalanderwalzen. Das Getriebe enthält ein Verstellgetriebe zur Phasenverstellung der Kalanderwalzen;
• Fig. 2 einen teilweisen Ausschnitt des Prägemusters der Kalanderwalzen gemäß Fig. 1,
• Fig. 3 eine Darstellung unterschiedlicher Überdeckungsgrade, die sich mit dem Prägemuster gemäß Fig. 2 erzielen lassen,
• Fig. 4 eine Darstellung von Überdeckungsgraden bei einem anderen Prägemuster,
• Fig. 5 einen Ausschnitt eines unter einem Winkel zur Längsachse der Kalanderwalzen angeordneten Oberflächenmusters mit unterschiedlichen Überdeckungsgraden, und
• Fig. 6 unterschiedliche Überdeckungsgrade bei einem weiteren Oberflächenmuster, welches unter einem Winkel zur Längsachse der Kalanderwalzen geneigt angeordnet ist.

The invention is explained in more detail below for better understanding with the aid of the exemplary embodiments shown in the drawing. Show it:

• Fig. 1 shows a schematic diagram of two calender rolls driven by a single motor via a gear. The gear contains an adjustment gear for phase adjustment of the calender rolls;
• 2 shows a partial section of the embossing pattern of the calender rolls according to FIG. 1,
• 3 shows a representation of different degrees of coverage that can be achieved with the embossing pattern according to FIG. 2,
• 4 shows a representation of degrees of coverage in another embossing pattern,
• 5 shows a section of a surface pattern arranged at an angle to the longitudinal axis of the calender rolls with different degrees of coverage, and
• Fig. 6 different degrees of coverage in a further surface pattern, which is arranged inclined at an angle to the longitudinal axis of the calender rolls.

The device shown schematically in Fig.1 comprises two calender rolls 10 and 12, which are driven at identical speed but in the opposite direction, so that a web-shaped material can be guided and embossed along a contact surface 14 (line pressure) between the calender rolls. The calender rolls 10 and 12 can have a bombage; however, it is also possible to use cylindrical calender rolls.

The upper calender roll 10 and the lower calender roll 12 are driven by a motor 24 via a gear 28 and drive shafts 22, 36 so that they run synchronously.

The adjustment gear 32 is a differential gear known per se (harmonic drive or specon differential gear), which enables an adjustment in the barrel via the adjustment shaft 34 manually or with a servo motor.

Normally, the rotational movement from the gear 28 is transmitted unchanged to the drive shaft 22 in an identical manner.

By means of the adjusting shaft 34 it is now possible to briefly change the "translation" of the adjusting gear 32, i.e. the speed at the input of the adjustment gear 32a deviates briefly from the speed at the output 32b. Then the original transmission characteristic of the adjustment gear 32 is set again, i.e. the two calender rolls 10 and 12 are again driven at the same speed.

During the short adjustment time through the adjustment shaft 34 there is a relative displacement between the two surfaces of the calender rolls 10 and 12, which is explained in more detail below, which leads to different degrees of coverage 42 and 48 (cf. FIGS. 3, 4, 5 and 6).

The two calender rolls 10 and 12 each have an identical surface pattern 38, which is shown in detail in FIG. 2. The surface pattern 38 is formed by a multiplicity of raised locations (squares) 40 which are arranged in a regular structure. With a₀ the side of a square 40 is designated, and t₀ indicates the division, which is the same in both directions - horizontally and vertically. The sides a₀ of the squares 40 run parallel or perpendicular to the respective axis 18 or 20 of the associated calender rolls 10, 12.

It is now assumed that the two calender rolls 10 and 12 are set relative to one another in such a way that the pairs of raised areas 40 of the surface patterns 38 of the two calender rolls 10 and 12 lying opposite one another come to lie exactly one above the other, that is to say each square 40 of the a calender roll 10 with the associated square 40 of the other Calender roller 12 meets exactly and the two surfaces of the squares are fully covered. This case is shown in the top row in FIG. 3, and the hatching 42 indicates that the degree of coverage covers the entire area of the squares 40.

$${\text{F}}_{\text{min}}\text{=}\frac{{\text{2a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \%}$$

Für das Verhältnis von F_max zu F_min gilt als Beziehung $$\frac{{\text{F}}_{\text{max}}}{{\text{F}}_{\text{min}}}\text{=}\frac{{\text{a}}_{\text{0}}}{{\text{2a}}_{\text{0}}{\text{- t}}_{\text{0}}}$$

In der obersten Reihe in Fig. 3 mit der vollflächigen Überdeckung ist eine Verschiebung s₀ zwischen den beiden Kalanderwalzen 10 und 12 zugrunde gelegt, d.h. die Verschiebung ist gleich Null, da die einzelnen Quadrate 40 vollflächig übereinander zu liegen kommen.In the exemplary embodiment described so far, the embossing area F to be specified in percent or the maximum value F _max and the minimum value F _min can be specified as follows: $${\text{F}}_{\text{Max}}\text{=}\frac{{\text{a}}_{\text{0}}{}^{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\%}$$

$${\text{F}}_{\text{min}}\text{=}\frac{{\text{2a}}_{\text{0}}{}^{\text{2nd}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\%}$$

The relationship for the ratio of F _max to F _min applies $$\frac{{\text{F}}_{\text{Max}}}{{\text{F}}_{\text{min}}}\text{=}\frac{{\text{a}}_{\text{0}}}{{\text{2a}}_{\text{0}}{\text{- t}}_{\text{0}}}$$

In the top row in Fig. 3 with the full area Coverage is based on a shift s₀ between the two calender rolls 10 and 12, ie the shift is zero, since the individual squares 40 come to lie one on top of the other.

If a short-term adjustment is carried out with the aid of the adjusting shaft 34 or the adjusting gear 32 - as already mentioned above - this has the consequence that a non-zero displacement results, with the effect that the mutually opposite squares 40 of the two Calender rolls 10 and 12 only partially overlap, as shown in Fig. 3 in the second to sixth series for different shifts s₁, s₂, s₃ and s₄. The hatchings indicate the different degrees of coverage 42.

Für die unterschiedlichen weiteren Verschiebungen s₁₋₄ ergeben sich die prozentualen Prägeflächen gemäß den nachfolgenden Beziehungen: $$\text{F₁ =}\frac{{\text{a}}_{\text{0}}{\text{(a}}_{\text{0}}\text{- s)}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% (für 0 < s <t₀ - a₀)}$$

$$\text{F₂ =}\frac{{\text{a}}_{\text{0}}{\text{(2a}}_{\text{0}}{\text{- t}}_{\text{0}}\text{)}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \%}$$

$$\text{=}\frac{{\text{2a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% (für s = t₀ - a₀)}$$

$$\text{F₃ =}\frac{{\text{2a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% (für t₀ - a₀ < s <}\frac{{\text{t}}_{\text{0}}}{\text{2}}\text{)}$$

$$\text{F₄ =}\frac{{\text{2a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{100 \% (für s =}\frac{{\text{t}}_{\text{0}}}{\text{2}}\text{)}$$

Für den in Fig. 4 dargestellten Fall a₀ = t₀/2, bei dem die Hälfte der Teilung gleich der Seitenlänge eines Quadrates ist, läßt sich eine maximale Prägefläche $${\text{F}}_{\text{max}}\text{=}\frac{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{4t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% = 25 \%}$$

erzielen, während sich die minimale Prägefläche gemäß nachfolgender Beziehung $${\text{F}}_{\text{min}}\text{=}\frac{\frac{{\text{2t}}_{\text{0}}{\text{}}^{\text{2}}}{\text{4}}\text{-}\frac{{\text{t}}_{\text{0}}{\text{· t}}_{\text{0}}}{\text{2}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% = 0 \%}$$

zu Null ergibt. Der letzte Fall darf natürlich nicht eintreten, da dann kein Überdeckungsgrad vorhanden ist und die einzelnen erhabenen Stellen auf den Oberflächen der beiden Kalanderwalzen 10 und 12 "abkämmen".3, the condition applies that the sides a₀ of the squares 40 are larger than t₀ / 2. In the event of a shift s₀ = 0 (top row in FIG. 3), the embossing area F₀ is calculated as follows: $$\text{F₀ =}\frac{{\text{a}}_{\text{0}}{}^{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for s₀ = 0)}$$

For the different further displacements s 1, the percentage embossing areas result according to the following relationships: $$\text{F₁ =}\frac{{\text{a}}_{\text{0}}{\text{(a}}_{\text{0}}\text{- s)}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for 0 <s <t₀ - a₀)}$$

$$\text{F₂ =}\frac{{\text{a}}_{\text{0}}{\text{(2a}}_{\text{0}}{\text{- t}}_{\text{0}}\text{)}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\%}$$

$$\text{=}\frac{{\text{2a}}_{\text{0}}{}^{\text{2nd}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for s = t₀ - a₀)}$$

$$\text{F₃ =}\frac{{\text{2a}}_{\text{0}}{}^{\text{2nd}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for t₀ - a₀ <s <}\frac{{\text{t}}_{\text{0}}}{\text{2nd}}\text{)}$$

$$\text{F₄ =}\frac{{\text{2a}}_{\text{0}}{}^{\text{2nd}}{\text{- a}}_{\text{0}}{\text{t}}_{\text{0}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for s =}\frac{{\text{t}}_{\text{0}}}{\text{2nd}}\text{)}$$

For the case shown in Fig. 4 a₀ = t Fig / 2, in which half of the pitch is equal to the side length of a square, a maximum embossing area can be $${\text{F}}_{\text{Max}}\text{=}\frac{{\text{t}}_{\text{0}}{}^{\text{2nd}}}{{\text{4t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% = 25\%}$$

achieve, while the minimum embossing area according to subsequent relationship $${\text{F}}_{\text{min}}\text{=}\frac{\frac{{\text{2t}}_{\text{0}}{}^{\text{2nd}}}{\text{4th}}\text{-}\frac{{\text{t}}_{\text{0}}{\text{· T}}_{\text{0}}}{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% = 0\%}$$

results in zero. The latter case must of course not occur, since there is then no degree of coverage and the individual "raised areas" on the surfaces of the two calender rolls 10 and 12 "comb".

gilt, mit den unterschiedlichen Verschiebungen s₀, s₁ und s₂. Folgende Berechnungsformeln für die Prägeflächen kommen zum Ansatz: $$\text{F₀ =}\frac{{\text{a}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% (für s = 0)}$$

$$\text{F₁ =}\frac{{\text{a}}_{\text{0}}{\text{(a}}_{\text{0}}\text{- s)}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% (für 0 < s < a₀)}$$

$$\text{F₂ = 0 \% (für s = a₀)}$$

The last case described can be seen from the surface pattern shown in FIG. 4, the condition for the following considerations $$\text{a₀ ≦}\frac{{\text{t}}_{\text{0}}}{\text{2nd}}$$

applies, with the different shifts s₀, s₁ and s₂. The following calculation formulas for the embossing surfaces are used: $$\text{F₀ =}\frac{{\text{a}}_{\text{0}}{}^{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for s = 0)}$$

$$\text{F₁ =}\frac{{\text{a}}_{\text{0}}{\text{(a}}_{\text{0}}\text{- s)}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% (for 0 <s <a₀)}$$

$$\text{F₂ = 0\% (for s = a₀)}$$

The dashed hatching 50 indicates that there is no overlap between the individual squares 40 of the upper and lower calender rolls 10 and 12, but that they comb alongside one another. The shift s₂ must therefore not be set because it can not achieve embossing.

For illustration purposes, some numerical examples are given in Table 1 below, which result from the use of the embossing pattern 38 according to FIGS. 3 and 4. For a = 1 mm and t = 1.75 mm, for example, a maximum stamping area F _max of 32.65% and a minimum stamping area F _min of 8.16% are calculated. By means of the adjustment gear 32, different embossing surfaces can be clearly realized within a relatively wide range, namely during ongoing operation, without it being necessary to replace the calender rolls 10 and 12.

With a constant pitch t and a = 1.3 mm, the maximum embossing area is F _max = 55.18% and F _min is 36.07%.

In den Ausführungsbeispielen gemäß Fig. 2 - 4 verlaufen die Seitenflächen der Quadrate 40 parallel bzw. senkrecht zu den Achsen 18, 20 der Kalanderwalzen 10, 12. Es ist aber auch möglich, die das Oberflächenmuster bildenden Quadrate unter einem Neigungswinkel α zu den Achsen 18 und 20 anzuordnen, wie dies in Fig. 5 und 6 für den Fall α = 45° anhand der auf beiden Kalanderwalzen 10, 12 wieder identischen Oberflächenmuster 44 dargestellt ist. Die erhabenen Stellen (Quadrate) sind mit der Bezugsziffer 46 bezeichnet, und die einzelnen Überdeckungsgrade 48 sind durch Schraffuren angedeutet. Hier gelten allgemein die nachfolgenden Beziehungen: $${\text{F}}_{\text{max}}\text{=}\frac{{\text{a}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \%}$$

$${\text{F}}_{\text{min}}\text{=}\frac{{\text{4a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- 4a}}_{\text{0}}{\text{t}}_{\text{0}}{\text{+ t}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \%}$$

$$\frac{{\text{F}}_{\text{max}}}{{\text{F}}_{\text{min}}}\text{=}\frac{{\text{a}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{4a}}_{\text{0}}{\text{}}^{\text{2}}{\text{- 4a}}_{\text{0}}{\text{t}}_{\text{0}}{\text{- t}}_{\text{0}}{\text{}}^{\text{2}}}$$

In dem besonderen Fall, daß die Seitenlänge a₀ gleich der Hälfte der Teilung t₀ ist, ergibt sich für $${\text{F}}_{\text{max}}\text{=}\frac{{\text{t}}_{\text{0}}{\text{}}^{\text{2}}}{{\text{4t}}_{\text{0}}{\text{}}^{\text{2}}}\text{· 100 \% = 25 \%}$$

Die minimale Prägefläche F_min beträgt dann 0 %. Als Funktion der unterschiedlichen möglichen Verschiebungen s wird die prozentuale Prägefläche gemäß der nachfolgenden allgemeinen Beziehung errechnet: $$\text{F (s) =}\frac{{\text{2a}}^{\text{2}}\text{- sa}\sqrt{\text{2}}{\text{+ s}}^{\text{2}}}{{\text{2t}}^{\text{2}}}\text{· 100 \%}$$

Optisch sind die bei den unterschiedlichen Verschiebungen s₀, s₁, s₂, s₃ und s₄ auftretenden unterschiedlichen Überdeckungsgrade 48 in Fig. 4 und 5 durch die Schraffuren 48 deutlich zu erkennen. In Fig. 5 ist zugrunde gelegt, daß a₀ größer als t₀/2 sei, während Fig. 6 für a₀ kleiner oder gleich t₀/2 gilt. Ähnlich wie voranstehend bei Fig. 3 und 4, lassen sich auch für den Fall in Fig. 5 und 6 mit dem Neigungswinkel α = 45° für unterschiedliche Verschiebungen die prozentualen Prägeflächen mathematisch bestimmen (auf die Wiedergabe der einzelnen Formeln wird hier verzichtet).

Depending on the requirements of the desired end product, the different embossing surfaces can thus be easily realized with the new device.

2-4, the side faces of the squares 40 run parallel or perpendicular to the axes 18, 20 of the calender rolls 10, 12. However, it is also possible to form the surface pattern Arrange squares at an angle of inclination .alpha. To axes 18 and 20, as shown in FIGS. 5 and 6 for the case .alpha. = 45.degree. On the basis of the surface patterns 44 again identical on both calender rolls 10, 12. The raised places (squares) are designated by the reference number 46, and the individual degrees of coverage 48 are indicated by hatching. The following relationships generally apply here: $${\text{F}}_{\text{Max}}\text{=}\frac{{\text{a}}_{\text{0}}{}^{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\%}$$

$${\text{F}}_{\text{min}}\text{=}\frac{{\text{4a}}_{\text{0}}{}^{\text{2nd}}{\text{- 4a}}_{\text{0}}{\text{t}}_{\text{0}}{\text{+ t}}_{\text{0}}{}^{\text{2nd}}}{{\text{t}}_{\text{0}}{}^{\text{2nd}}}\text{100\%}$$

$$\frac{{\text{F}}_{\text{Max}}}{{\text{F}}_{\text{min}}}\text{=}\frac{{\text{a}}_{\text{0}}{}^{\text{2nd}}}{{\text{4a}}_{\text{0}}{}^{\text{2nd}}{\text{- 4a}}_{\text{0}}{\text{t}}_{\text{0}}{\text{- t}}_{\text{0}}{}^{\text{2nd}}}$$

In the special case that the side length a₀ is equal to half the division t₀, we get for $${\text{F}}_{\text{Max}}\text{=}\frac{{\text{t}}_{\text{0}}{}^{\text{2nd}}}{{\text{4t}}_{\text{0}}{}^{\text{2nd}}}\text{100\% = 25\%}$$

The minimum stamping area F _min is then 0%. As As a function of the different possible displacements s, the percentage embossing area is calculated according to the following general relationship: $$\text{F (s) =}\frac{{\text{2a}}^{\text{2nd}}\text{- sa}\sqrt{\text{2nd}}{\text{+ s}}^{\text{2nd}}}{{\text{2t}}^{\text{2nd}}}\text{100\%}$$

Visually, the different degrees of coverage 48 occurring in the different displacements s₀, s₁, s₂, s₃ and s₄ in FIGS. 4 and 5 can be clearly recognized by the hatching 48. 5 is based on the fact that a₀ is greater than t₀ / 2, while FIG. 6 applies to a₀ less than or equal to t₀ / 2. Similar to FIGS. 3 and 4 above, for the case in FIGS. 5 and 6 with the inclination angle α = 45 ° for different displacements, the percentage stamping surfaces can be mathematically determined (the individual formulas are not shown here).

6 in the case of the shift s₂, in which there is no degree of coverage at all, rather, the dashed hatching 52 illustrates here that the individual squares 46 - as in FIG. 4 in the bottom row - comb side by side. This case can of course be excluded in practical application.

The advantage of the new method and of the new device is not only limited to being able to set different embossing surfaces with simple measures during operation, but - as FIG. 5 illustrates - it is also possible to use the different embossing surfaces or degrees of coverage 48 with different patterns. There desired effects can also be achieved optically.

By applying a constant, uniform or non-uniform speed to the adjusting shaft of the adjusting gear, a material with a constantly changing embossing pattern can be produced.

In the exemplary embodiments described, a displacement perpendicular to the axes 18, 20 of the calender rolls 10, 12 was assumed in each case, and this solution is appropriate for cylindrical calender rolls 10, 12 and those with a bomb.

The idea according to the invention can of course also be realized by moving it in the direction of the axes 18, 20 by means of an adjustable bearing 30 if cylindrical calender rolls are used.

The invention is not limited to the thermal consolidation of a nonwoven fabric, rather the invention can also be used to achieve surface effects or surface structures on any sheet-like materials (for example paper, synthetic leather, aluminum, etc.).

Overall, the invention achieves the following advantages over the prior art, for example in the thermal consolidation of nonwovens:
Downtimes when changing the embossing area are significantly reduced or eliminated;
Specified strengths of the finished nonwoven can be safely maintained despite the raw material fluctuations and / or fluctuations in the fiber orientation during fiber deposition by gradually adjusting the embossing surface during thermal consolidation;
Investment costs for embossing rollers when using multiple embossing patterns are drastically reduced: When using, for example, three different embossing patterns, eight rollers (including replacement rollers) are necessary with conventional technology; when using the invention, only four rollers, including replacement rollers, are required;
Lower costs for embossing rollers because of Using two "patterned" rollers the etching depth of each roller only has to be half as deep;
Nonwoven that has been thermally bonded using the invention has a significantly softer "grip", since the "secondary bonds" that result from one-sided, full-surface contact with a smooth roller according to the prior art are not present.

Claims (11)

1. Method of stiffening and/or thermally binding and/or embossing sheet materials, and/or of deforming sheet or strip materials, especially a fibre non-woven at discrete positions, by means of two rotatable calender rolls forming a gap, between which the fibre non-woven is guided, the calender rolls being provided with raised discrete locations which form a surface pattern (embossed pattern comprising embossed areas), characterized in that each calender roll (10, 12) is separately driven each at synchronous speed, and that the degree of overlap (42; 48) between mutually facing pairs of raised locations (40; 46) which determines the embossed areas (F) can be adjusted to different values between a minimum and a maximum.

2. Method according to Claim 1, characterized in that the degree of overlap (42; 48) between mutually facing pairs of raised locations (40; 46) is modified in that the rotational speed of one of the two calender rolls (10, 12) is temporarily changed with respect to the constant rotational speed of the other calender roll (12, 10) and thereafter is again adjusted to the original, identical value.

3. Method according to Claim 1, characterized in that the degree of overlap (42; 48) between mutually facing pairs of raised locations (40; 46) is adjusted by axial displacement of at least one of the two calender rolls (10, 12).

4. Device for stiffening and/or thermally binding and/or embossing sheet materials, and/or for deforming sheet or strip materials, especially a fibre non-woven at discrete positions, comprising two rotatable calender rolls forming a gap, between which the fibre non-woven is guided, the calender rolls being provided with raised locations, which form a surface pattern (embossed pattern comprising embossed areas), characterized in that a drive unit for driving the calender rolls (10, 12) at identical rotational speed is provided, and that the drive unit comprises an adjusting gear (32), which makes possible an angular displacement of one of the two calender rolls (10, 12) relative to the other calender roll (12, 10).

5. Device according to Claim 4, characterized in that the mounting of at least one of the two calender rolls (10, 12) comprises a device which makes possible an axial displacement relative to the other calender roll (12, 10).

6. Device according to one of the preceding Claims 4 and 5, characterized in that the calender rolls (10, 12) have identical surface patterns (38; 44).

7. Device according to Claim 6, characterized in that the raised locations (40; 46) forming the surface pattern (38; 44) have equal square areas.

8. Device according to Claim 6, characterized in that the raised locations (40; 46) forming the surface pattern (38; 44) possess random areas.

9. Device according to Claim 7, characterized in that the half-pitch (t/2) (one-half of the distance between two corresponding sides of adjacent raised locations (40; 46)) of the surface pattern (38; 44) is smaller than or equal to the side length of the square areas.

10. Device according to one of the preceding Claims 4 and 5, characterized in that the calender rolls (10, 12) have different surface patterns.

11. Device for stiffening and/or thermally binding and/or embossing sheet materials, and/or deforming sheet or strip materials, especially a fibre non-woven at discrete positions, comprising two rotatable calender rolls forming a gap, between which the fibre non-woven is guided, the calender rolls being provided with raised, discrete locations, which form a surface pattern (embossed pattern comprising embossed areas), characterized in that the adjusting gear (32) according to Claim 5 is continually operated with a uniform or non-uniform adjusted rotational speed and thereby a continually changing embossing is produced.

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