The present invention relates to an embossing unit. More in particular, the present invention relates to an embossing unit for embossing a multi-ply web material, preferably made of tissue paper, for example to manufacture toilet paper, kitchen towels and other cellulose products.
Embossing is one of the operations that are normally performed on plies or sheets of tissue paper, to produce paper articles for personal and household cleaning and hygiene, or also for commercial and industrial use, such as toilet paper, kitchen towels, paper napkins and handkerchiefs and the like.
Embossing is an operation that is performed for the dual purpose of improving aesthetic properties and increasing functional properties, in particular the softness, smoothness, absorption capacity or thickness of the finished material.
Normally, a tissue paper material, such as kitchen towel or toilet paper, is produced from two or more plies of paper embossed separately and subsequently bonded together by applying a glue and laminating the plies between counter-rotating rollers defining a lamination nip.
Embossing is typically performed by feeding each ply between an embossing roller, equipped with protuberances, and a pressure roller with an outer surface coated in yielding material, typically rubber. In this case this is known as steel to rubber embossing, as the embossing roller is typically made of steel. In some cases embossing is performed between two rollers made of steel or another hard material, one equipped with protuberances and the other with corresponding recesses. The protuberances of the embossing roller produce corresponding protuberances or projections in the paper ply. The protuberances formed in the two outermost plies are facing the inside of the finished product.
According to a possible technique (known as tip-to-tip”), the two plies of paper web material are bonded by making the protuberances of one ply coincide with the protuberances of the other ply, having previously applied glue to the protuberances of one of the two plies, or at least to some of said protuberances. In practice, two embossing rollers which emboss the two paper plies separately by means of respective pressure rollers, form therebetween a lamination nip, through which the two embossed plies are fed before being detached from said rollers. In the lamination nip the protuberances of one roller coincide with the protuberances of the other roller and the reciprocal distance between the rollers is such as to cause localized compression of the plies at said protuberances.
A tip-to-tip embossing unit for obtaining a product of this type is described in U.S. Pat. No. 3,414,459. The tip-to-tip embossing technique has gradually been perfected and improved, in order to solve particular problems arising with this processing method. U.S. Pat. No. 5,096,527 describes, for example, a technique to reduce the vibrations and wear in tip-to-tip embossing units. U.S. Pat. No. 6,113,723 describes a distribution of protuberances having the object of increasing the adhesion strength through a particular arrangement of the protuberances. U.S. Pat. No. 5,736,223 describes a method for producing a paper article in sheet form comprising three layers or plies of tissue paper.
U.S. Pat. No. 5,173,351; U.S. Pat. No. 6,032,712; U.S. Pat. No. 6,245,414; U.S. Pat. No. 6,053,232 describe embossing-laminating units which with particular measures prevent concentrated wear of the protuberances also when these do not completely coincide, but give rise to a partial correspondence in areas, between some of the protuberances of one roller and some of the protuberances of the other. U.S. Pat. No. 3,961,119 describes a tip-to-tip embossing unit, wherein two mutually cooperating embossing rollers are equipped with helical projections. The projections of one embossing roller present protrusions that mesh with recesses provided in the helical projections of the opposed embossing roller.
According to a different technique, the two plies are embossed separately, each between an embossing roller and a counter-roller or pressure roller. The two plies are then mutually joined so that the protuberances of one ply are nested between the protuberances of the other ply. This is known as “nested” embossing. Lamination of the two plies is obtained between one of the embossing rollers and a laminating roller, while the two embossing rollers do not touch. Examples of embossing-laminating devices of this type are described in U.S. Pat. No. 3,556,907; U.S. Pat. No. 3,867,225; U.S. Pat. No. 5,339,730.
U.S. Pat. No. 5,686,168 describes a method of nested embossing, wherein the plies are bonded by lamination between two opposed embossing rollers.
U.S. Pat. No. 6,578,617 and U.S. Pat. No. 6,470,945 describe embossing units that can perform embossing according to both the aforesaid techniques. To switch from tip-to-tip to nested embossing, the angular phase and/or the axial position of the two embossing rollers can be modified.
U.S. Pat. No. 6,261,666 describes a similar device for alternatively performing tip-to-tip or nested embossing. Another similar device is described in U.S. Pat. No. 6,109,326.
Initially, embossing was performed according to very simple geometric patterns, with uniform distribution of truncated-cone or truncated-pyramid shaped protuberances. This embossing had a prevalently technical function, used to produce a product of adequate thickness and with sufficient softness and absorption capacity.
Currently, embossing must increasingly achieve a dual function, both technical-functional and aesthetic. Therefore, embossing patterns and embossing devices have been developed which make it possible to obtain a product that is aesthetically pleasing and at the same time suitable to satisfy the aesthetic requirements and increasing commercial requirements demanded of these products. Embossing is no longer produced only through simple geometrical patterns, but by combinations of embossing areas of greater or lesser density (at times of micro-embossing) and of decorative patterns embossed and optionally printed. Examples of complex embossing patterns are described in U.S. Pat. No. 6,136,413; U.S. Pat. No. 5,846,636; U.S. Pat. No. 6,106,928.
A new embossing technique that makes it possible to obtain particularly refined and easily interchangeable motifs is described in U.S. Pat. No. 6,755,928 and in U.S. Pat. No. 6,681,826.
WO-A-2006/027809 describes a convertible embossing unit, wherein a pair of fixed sides cooperate with a pair of oscillating sides to define two pairs of supporting seats for the embossing rollers. In order to arrange the embossing rollers in two alternative positions, the mobile sides can cooperate directly with the fixed sides, or alternatively the fixed and mobile sides can be equipped with elements to close and complete the seats to support the ends of the embossing rollers. The embossing unit thus configured, although characterized by the possibility of modifying the arrangement of the rollers, has limited flexibility.
One of the requirements considered most necessary in the paper converting industry is the possibility to adapt production lines to different market demands, with fast and simple modifications of the line, to avoid stoppage thereof and consequent loss of production.
According to a possible embodiment, an object of the invention is to propose an embossing unit that can be easily adapted to various types of production and that can produce embossed materials according to one or other of different embossing techniques.
In substance, according to one embodiment of the invention there is provided an embossing unit to emboss and join at least two plies of web material, comprising in combination:
Further advantageous characteristics and embodiments of the invention are indicated in the appended claims and will be described with reference to a non-limiting embodiment of the invention. It must be understood that the invention also relates to an embossing unit comprising only some of the equipment and of the devices that allow the embossing unit to be configured in at least two distinct operating arrangements.
The invention will be better understood by following the description and accompanying drawing, which shows a non-limiting practical embodiment of the invention. More in particular, in the drawing:
With initial reference to
The embossing unit, indicated as a whole with 1, comprises a base structure 3, which in turn comprises, for example, a pair of parallel side members, on which the supports for the embossing rollers are arranged. There is associated with the structure 3 a first support 5 with a portion 5A by means of a hinge 5B, with which the portion 5A is hinged to the structure 3. In all the figures of the accompanying drawing, the embossing unit is in practice shown in a cross-section according to a longitudinal median plane arranged in an intermediate position between the two lateral side members of the machine. Therefore, in the drawing only one of the two side members forming the structure 3 is visible.
Hereunder and hereinbefore and also in the appended claims, when reference is made to a support for a roller this must in fact be understood as the pair of support elements on the two side members for the two ends of the respective roller. Therefore, returning to
In the support 5 there is housed a first embossing roller 7, for example a steel roller or in any case a roller made of a sufficiently hard material to perform the embossing operation on the web material that is fed to the embossing unit. In a manner known per se and not shown, the embossing roller 7 presents on the surface thereof embossing protuberances according to a suitable embossing pattern.
The embossing unit 1 also comprises a second support 9 for a first pressure roller 11. The pressure roller 11 can, for example, be composed of a roller coated with an elastically yielding material, such as rubber or the like, which cooperates with the first embossing roller 7. Also with regard to the support 9, it must be understood that in fact it presents two support elements, one for each side member forming the load-bearing structure 3. The support 9 comprises two seats 9A and 9B adjacent to each other and provided on an arm 12 hinged at 13 to the respective side member. The number 15 indicates a piston-cylinder actuator, which carries the arm 12 and therefore the pressure roller 11 to the operating position shown in
The two seats 9A, 9B are used alternatively according to the configuration taken by the embossing unit, as will be more apparent from the description below. In the configuration of
The seats 9A, 9B are closed at the top by an element 9C (
The pressure roller 11 is housed in the seats 9A or 9B removing the top element 9C which is then fitted to the underlying portion 9A, 9B of the seats to clamp the roller 11 and support it in the position it must take during operation.
The embossing unit 1 comprises a third embossing roller 17 supported in a third support 19 provided with an openable portion 19A similar to the portion 5A that allows opening and closing of the support 5 of the first embossing roller 7. The portion 19A is pivoted in 19B to the respective side member of the load-bearing structure 3. In
As shown in particular in the detail in
The number 29 indicates an actuator (called “Torpress”) which presses between the structure 3 and the oscillating base 23 to cause the second embossing roller 17 to press against the first embossing roller 7, in a tip-to-tip arrangement, i.e. with at least some of the protuberances of the roller 7 pressing against at least some of the protuberances of the roller 17 in the nip defined between the embossing rollers.
With the second embossing roller 17 there cooperates a second pressure roller 33 supported in a support 35 provided in an oscillating arm 37 and formed of two openable portions, the movable one of which is indicated with 35A in
A base 3A for a gluing unit 45 is associated with the fixed structure 3, movable according to the double arrow f45 to move toward or away from the embossing roller 7.
The gluing unit 45 comprises cylinders 47, 49 that pick up the glue from a reservoir and transfer it to the web material fed around the embossing roller 7, all in a manner known per se and which does not require further description herein.
As can be observed in
In this configuration the pressure rollers 11 and 33 are located on opposite sides of the substantially horizontal geometrical plane on which the axes of rotation of the embossing rollers 7 and 17 lie.
The embossing unit described here can be reconfigured to take a different position of the embossing and pressure rollers, again arranged so as to operate in a tip-to-tip arrangement.
This second configuration is shown in
It can be seen that in this configuration the support 35 is empty and held in an idle position with the arms 37 rotated clockwise with respect to the position taken thereby in
The support 51, or more precisely each support element for the two ends of the pressure roller 33, is pivoted in 53 to the respective side member of the machine and associated with a piston-cylinder actuator 55, which presses the pressure roller 33 against the embossing roller 17.
The support 51 of the pressure roller 33 in this configuration is shown in detail in
As can be seen in particular in
The possibility of configuring the embossing unit 1 in one or other of the two modes illustrated above makes it possible to choose the best arrangement of the embossing rollers and of the pressure rollers as a function of the type of embossing pattern, taking into account the deformations to which the embossing rollers are subjected due to their weight and to the thrusts exerted thereon by the pressure rollers 11 and 33.
With regard to the supports of the embossing rollers 7 and 17, and of the first pressure roller 11, the configuration of
The same embossing unit described above can be transformed to take a configuration for nested or “DESL” embossing, or to operate according to an “embossing-gluing” technique typical of the most modern embossing units. These last configurations will be described below with reference to
With respect to the configuration of
The second pressure roller 33 is supported in the support 35 which, due to an appropriate oscillation of the arms 37, is in a lower position with respect to the position that it takes in the configuration of
In the fifth support 51, not utilized in the configuration of
The position of the support 19 and therefore of the axis of the embossing roller 17 with respect to the first embossing roller 7 is defined in this configuration by a stop 65 adjustable, for example, through a servomotor 67. In fact, in this configuration the embossing roller 17 must not press against the embossing roller 7, but is maintained so that there is no reciprocal pressure in the nip between the two rollers. It must be understood that preferably the stop 65 is double, with a stop element on each side member of the embossing unit 1 and one or two servomotors for adjustment thereof.
In the configuration show in
In the configuration of
From the above description it is apparent that the embossing unit according to the invention can take a variety of configurations simply by fitting or removing equipment, modifying the position taken by the axes of the various rollers. This allows the users of the embossing unit to produce, with the same line and the same unit, different materials according to market demands with minimum operations to modify the configuration of the machine.
It is understood that the drawing only shows an example provided by way of a practical arrangement of the invention, which may vary in forms and arrangements without however departing from the scope of the concept underlying the invention. Any reference numbers in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims.
Number | Date | Country | Kind |
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FI2007A000048 | Feb 2007 | IT | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IT2008/000096 | 2/15/2008 | WO | 00 | 8/26/2009 |