Device for cleaning cylinders in plants for the treatment of web like paper material.

DESCRIPTICN

The present invention relates to a device for cleaning the cylinders in plants for the treatment of web like paper material .

A known technique for the tratment of web like paper material provides for the embossing of one or more paper webs, commonly said plies, and their bonding by gluing.

The embossing, which produces an apparent increase in thickness of the plies, is made by passing a ply through an embossing unit which comprises an embossing cylinder, provided with reliefs and/or depressions arranged in a predetermined pattern, and a corresponding smooth counter- cylinder. The ply, passing between the embossing cylinder and the smooth counter-cylinder, is deformed assuming a conformation corresponding to the reliefs, or depressions, of the embossing cylinder.

To achieve bonding of the plies, use is made of a sizing unit whereby a first embossed ply is adhesivised. The definitive bonding of the plies takes place by passing them through a nip formed in part by the first embossing cylinder and in part by a pressure cylinder, commonly called "marrying roll". The plies to be joined to form the finished product can be all embossed or in part embossed and in part smooth or micro- embossed.

The scheme in Fig.l shows a generic embossing step implemented by passing two paper plies (VI, V2) through two corresponding embossing units (El, E2) , each of which comprises an embossing cylinder (Gl, G2) with a corresponding counter-cylinder (CI, C2) . Each of the plies (VI, V2) is embossed in the respective unit (El, E2) . The first embossing cylinder (Gl) is associated with a roller (RA) forming part of a sizing unit (C) comprising a tank (S) and a roller (R) that picks up the glue from the tank (S) and distributes it on the end roller (RA) which in turn applies the glue on the embossed ply supported by the outer surface of the first embossing cylinder (Gl) . The definitive joining of the embossed plies takes place by passing them through a nip formed in part by the first embossing cylinder (Gl) and in part by a marrying roll (MR) which is in contact with the latter. The finished product, consisting of the plies embossed and glued to each other, is marked by the reference "PF" .

A drawback arising from such an embossing technique resides in the fact that on, the surface of the embossing cylinder with which the marrying roll and the sizing unit are in contact, glue deposits are formed and the paper of the plies in treatment tends to adhere to the same surface and to break. Therefore, there is the need to periodically stop the plant to ensure the cleanliness of the embossing cylinders. For cleaning of the embossing cylinders currently use is made of brushes or scrapers associated with a sprayer which delivers lubricating substances. However, the use of brushes and scrapers normally implies a premature wear of the outer surface of the embossing cylinder. Moreover, given the delivery pressure of the lubricating substances, around the cylinder to be cleaned there is a sort of cloud formed by the lubricating particles that is incompatible with the need to preserve the healthiness of the workplace and implies the adoption of complex containment systems of said particles. The drawbacks associated with the deposition of sticky and fibrous residues also concern the marrying roll.

Examples of devices for cleaning rollers are disclosed in DE4105674A1 and US2010/218909A1. The device disclosed in DE4105674A1 includes a deformable cylindrical brush that acts by contact on the outer surface of a roller to be cleaned. The device disclosed in US2010/218909A1 comprises one or more pads coupled to a support which in turn has one end that can be inserted in a doctor blade holder preferably by means of a hinge connection.

The main purpose of the present invention is to eliminate, or at least greatly reduce, the aforementioned drawbacks and to propose a device allowing to widen the range of products that can be used for cleaning the rollers.

This result is achieved, according to the present invention, by adopting the idea of making an apparatus having the features indicated in claim 1. Other features of the present invention are the subject of the dependent claims.

Thanks to the present invention, it is possible to remove effectively and with simplicity the sticky and fibrous residues from the surface of the embossing cylinders and other cylinders used for the treatment of paper materials, as the marrying rolls. Furthermore, it is possible to distribute the lubricating substances, or detergents, on the surface of said cylinders without dispersion of the same substances and during normal operation of the embossing units that, therefore, must not be necessarily stopped. Therefore, a device according to the present invention provides benefits both in economic terms and in terms of healthiness in the workplace.

These and other advantages and features of the present invention will be best understood by anyone skilled in the art from the following description and with the aid of the attached drawings, given by way of example but not to be considered in a limiting sense, in which:

- Fig.l schematically represents a generic embossing step and gluing of two paper plies;

- Fig.2 is a schematic cross-sectional view of a device according to the invention;

- Fig.3 is a schematic side view of a generic embossing system on which is mounted the device shown in Fig.2;

- Fig.4 shows an enlarged detail of Figure 3 with some parts omitted to better illustrate others; - Figs. 5-7 are three perspective views of the device shown in Fig.2;

- Fig.8 is a schematic rear view of the device shown in Fig.2;

- Fig.9 shows a schematic exploded view of the device shown in Figs. 2-8;

- Fig.10 is an enlarged detail relating to the contact between the embossing cylinder (5) and the roller (23), in which the reference "VO" indicates a veil of emulsifiable silicone oil on the surface of the roller (23) ;

- Fig.11 is a schematic side view of the device shown in Figs. 2-10 according to a further embodiment.

A device in accordance with the present invention can be used, for example, in an embossing system - known per se - of the type shown in Fig.3, wherein an embossing step is carried out by passing two paper plies (1, 2) through two corresponding synchronized embossing units (3, 4), each of which comprising an embossing cylinder (5, 6) associated with a counter-cylinder (7, 8); wherein each of the plies (1, 2) is embossed in a respective embossing unit (3, 4); wherein a first embossing cylinder (5) is in contact with an end roller (9) that is part of a sizing unit (10) comprising a reservoir (11) and a roller (12) which picks up the glue from the tank (11) and distributes it on the end roller (9) which in turn applies the glue on the embossed ply supported on the surface of the first embossing cylinder (5) ; and wherein the final joining of the embossed plies takes place by passing them through a nip formed in part by the first embossing cylinder (5) and in part by a marrying roll (13) that is in contact with the same first embossing cylinder on a side opposite to said end roll of the sizing unit . In Fig.3, The finished product, consisting of the plies embossed and glued together, is marked by the reference "14".

Reduced to its essential structure and with reference to Figures 2-10 of the attached drawings, an apparatus according to the present invention comprises a rigid shoe (15) , preferably made of a so-called self-lubricating material, intended to press with its lower or ventral surface (150) on the outer surface of the embossing cylinder (5) to be cleaned.

The shoe (15) can be made of any metal or composite material, preferably self-lubricating (meaning a material with a low coefficient of friction), normally available on the market. For example, the shoe (15) can be made of bronze with graphite inserts distributed on the ventral surface (150) . Even lamellar cast iron is a material suitable for this purpose because in such material the graphite is in the lamellar form, that is, in a form that promotes the self- lubrication. Still, the shoe (15) can be made of any metal coated, or plated, with a material with a low coefficient of friction of the type commonly available on the market. The shoe (15) can be, for example, of steel with a ceramic coating at least at said ventral surface (150) .

The said ventral surface (150) is concave, with the concavity turned outwards to fit the curvature of the cylinder (5) with which it is in contact. With reference to the example illustrated in the attached drawings, said surface (150) is a cylindrical surface portion whose diameter is equal to the outer diameter of the cylinder (5) . From the opposite side to the surface (150) destined to be in contact with the cylinder (5), the shoe (5) has a stem (151) inserted in a guide (160) formed in an end portion of a respective support (16) . Inside the guide (160), the stem (151) of the shoe (15) is preferably subjected to the thrust of a spring (152) that is oriented in a radial direction relative to the cylinder (5) , i.e. with respect to said surface (150), to always ensure the contact of the latter with the outer surface of the cylinder (5) . For this purpose, the support (16) of the shoe (15) has a corresponding inner seat (161) for the spring (152) . Furthermore, the said support (16) has, in its rear part (162) - that is, in the part opposite to that of the guide

(160) in which the shoe (15) is inserted -, an appendix (162) on which there is fixed a front portion (163) of an extension element (164) . In practice, the element (164) forms a rear extension of the support (16) . By means of this extension

(164), the support (16) is fixed to a slide (17) which, in turn, is mounted to slide along an inclined (180) of an arm

(18) movable, as further described below, parallel to the embossing cylinder (5) with which the shoe (15) is in contact. Therefore, the support (16) is firmly connected to the arm (18) and follows any movement of the latter, allowing, in this way, to move the shoe (15) parallel to the embossing cylinder (5) .

The said arm (18) is connected, in correspondence of an upper extension (181) thereof, with a carriage (19) which moves along a horizontal guide (20), i.e. a guide parallel to the embossing cylinder (5) axis, and is driven by an electric motor (21) with which the carriage (19) is connected by a transmission belt ring (22) closed on two pulleys (200) each of which is at a respective side of the guide (20) . The carriage (19) is connected to the lower part of the belt (20) by means of a clamp (201) whose jaws engage the same lower of the belt (20) . In Fig 8 the double arrow "F" represents the bidirectional movement of the carriage (19) along the guide (20). The motor (21) moves the carriage (19), by means of belt (20) , between two opposite end positions (H, K) of the guide (20) under the control of two limit switches (not visible in the drawings) each of which is placed in correspondence with one of said end positions.

Preferably, the said support (16) can be moved along the inclined part (180) of the arm (18), to move it away from the embossing cylinder (5) and respectively move it close to the latter as further described below, by means of a pneumatic actuator (300) whose skirt is fixed to the arm (18) through a connecting plate (318) and whose stem acts on a screw (301) inserted in a lateral appendix (170) of the slide (17) . On the same lateral appendix (170) of the slide (17) there is a spring (172) fitted on a screw (that is parallel to the screw 301 subjected to the action of the actuator 300) equipped with an adjusting ring (173) so the preload of the spring (172) can be adjusted.

When the carriage (19) reaches one of said end positions, for example the position (K) , the support (16) - with all the elements associated with it, and therefore also the shoe (15) - is moved away from the embossing cylinder (5), by means of the actuator (300) that is correspondingly activated and overcomes the resistance offered by the spring (172) , to then be re-approached to the same embossing cylinder (5) when the carriage (19) is reaches the other end position (H) of the e guide (20) : in the position (H) the actuator (300) is deactivated and the spring (172) determines the repositioning of the shoe (15) on the surface of the cylinder (5) . In other words, cyclically, the shoe (15) runs along the line H-K remaining with its concave surface (150) in contact with the embossing cylinder (5), then is moved away from the latter, is carried back to the starting position (H) and therefore is approached again to the embossing cylinder (5) .

By means of the screw (301), whose free end (302) can be approached to the actuator (300) or moved away from the latter simply by screwing or unscrewing the same screw (301), it is possible to adjust the intervention position of the actuator (300) on the slide (17) and then on the support (16).

By means of the carriage (19) it is possible to move the arm (18), and then the aforementioned support (16) with all the elements it supports, parallel to the cylinder (5) . In other words, by moving the arm (18) parallel to the cylinder (5), the shoe (15) performs a scraping of the sticky residue from the surface of the same cylinder (5) while it is in rotation, i.e. while the unit embossing is in operation. The scraping action of the shoe (15) does not cause a premature wear of the cylinder (5) given the concave shape of its ventral surface (150) designed to be in contact with the engraved surface of the same cylinder (5) and also by virtue of the fact that the shoe (15) is made of self-lubricating material as said above. Furthermore, since the stem (151) of the shoe (15) is free to move in the guide (160) of the support (16), although contrasted by the spring (152), the possible shape irregularities of the sticky residue does not alter its effectiveness . The removal of sticky and fibrous residues from the surface of the engraved cylinder (5) thus made drastically reduces the drawbacks previously cited.

Preferably, the concave surface (150) of the shoe (15) is engraved, presenting a series of grooves (153) . For example, the said grooves (153) are helicoidal.

Preferably, the depth of said grooves (153) is at least equal to the height of the reliefs (50) presented by the embossing cylinder (5) .

Alternatively, said surface (150) may be perforated.

The presence of holes or grooves on the surface (150) may further improve the effect of scraping of residues from the surface of the cylinder (5) .

The device described above can also be used in combination with a dispenser of lubricating fluids (eg. emulsifiable silicone oil of the type used in conventional systems) .

In accordance with a further aspect of the present invention, the said support (16) also supports an idle roller (23) adapted to distribute lubricating substances (for example emulsifiable silicone oil the type normally used in this industrial sector) on the surface of the engraved cylinder (5) . More particularly, in accordance with the example shown in the figures of the attached drawings, the said roller (23) is oriented parallel to the engraved cylinder (5) and its shaft (230) is carried by a base (231) connected, by means of a hinge (232), to the support (16): the hinge axis (232) being parallel to the axis of the embossing cylinder (5) and of the roller (23) . The roller (23) is located upstream of the shoe (15) relative to the direction of rotation (R5) of the cylinder (5) and is made of rubber. On the side opposite to that of contact with the cylinder (5), the roller (23) is in contact with an felt element (24) through which receives the lubricants substances, drawn by the same felt (24) from a respective tank (25) which is fixed to the aforementioned rear appendix (162) of the support (16) . In this way, the roller (23) receives the lubricating substances contained in the tank (25) and applies them by contact on the surface of cylinder (5) upstream of the shoe (15) .

A spring (233), housed in a corresponding angled seat (165) formed in the support (16), exerts a thrust on the base (231) , at a preset point of the latter, in order to keep the roller (23) to contact with the embossing cylinder (5) . Since the roller (23) is integral with the support (16), the movement (F) imparted thereto by means of the arm (18) and the carriage (19), also affects the roller (23).

The combined action of the roller (23) and the shoe (15) helps to further reduce the drawbacks previously cited.

According to a further embodiment of the present invention, the roller (23) can be divided into two parts (23a, 23b), one of which is intended to distribute by contact the lubricating substances on the cylinder (5), as in the previous example; and the other is intended to apply water, even by contact, on the cylinder (5) . In this case, each of the two parts (23a, 23b) of the roller (23) is connected to a respective tank by means of a corresponding felt. In accordance with this further embodiment of the invention, the two parts (23a, 23b) in which is divided the roller (23) are coaxial with each other and mounted on the same shaft (230) .

The detail in Fig.10 shows how the roller (23) is subject to deformation and acts also on the sides of the reliefs (50) of the cylinder (5) . In accordance with a further embodiment of the present invention, schematically shown in Fig.11, the shoe (15) and the roller (23) are as long as the cylinder (5) and the arm (18) is fixed, i.e. not connected with any carriage.

What has been said above with reference to the embossing cylinder (5) identically applies also to other cylinders used for treating the paper material, such as the marrying roll (13) that can be affected also by the formation of sticky or fibrous residues. In other words, the device disclosed above is usable not only for cleaning embossing cylinders but also for cleaning a marrying roll and, more generally, for cleaning cylinders coming into contact with glued paper material .

In the drawings, the reference (303) indicates an anti- accident fixed structure covering the device described above. In practice execution details may vary in any equivalent way with regards to the arrangement and conformation of the individual elements disclosed and illustrated, as well as the nature of the materials indicated, without departing from the scope of the adopted solution and thus remaining within the limits of the protection conferred by this patent.