Calendar and method for processing web-like materials

Abstract

A calender for processing web-like material, comprising a structure for supporting two heated rollers forming a nip, each roller having a surface relief (RR), in an operating setting of the calender, the relief of one roller radially faces the relief of the other roller, each roller rotates about its axis at a predetermined angular velocity, the rollers are heated by heating means, and each roller undergoes an axial elongation as a result of said heating. The calender comprises detection means (E1, E2; IS) adapted to detect the axial elongation of each roller, and a programmable control unit (UCP) connected to said detection means and to said heating means. The control unit is programmed to determine the difference in axial elongation between the rollers and to issue an alarm signal if the absolute value of this difference is greater than a limit value.

Description

Technical Field

[0001] The present invention relates to a calendar and a method for processing web-like materials.

[0002] More particularly, the calendar and method according to the present invention relate to the processing of web-like materials by heated rollers.

Background Art

[0003] The processing of web-like materials, particularly non-woven fabrics (TNT), is described in Patent Document 1, which shows a system including a calendar formed by two heated embossing rollers that define a nip intersecting a web of a TNT-type material containing thermoplastic fibers. The material crossing the nip between the two rollers is subjected to a combined pressure and heat treatment, which determines the arrangement and physical state changes of the fibers contained in the material itself. In particular, depending on the pressure applied to the material processed by the rollers, the operating temperature of the rollers, the thickness and composition of the material, and the surface treatment of the rollers, deformations corresponding to a predetermined pattern can be formed in the material. Other systems including calendars using heated rollers for the processing of TNT are described in Patent Document 2 and Patent Document 3.

[0004] The calendar rollers through which the material to be processed passes can be arranged in a so-called "tip to tip" configuration, which means that the relief or "tips" of the calendar rollers must always coincide with the relief of the other calendar rollers, i.e., the two rollers must always be in the same phase.

[0005] The disadvantage of a calendar configured in this way is that the rollers tend to lose their axial phase during use, which results in the production of products that do not conform to the manufacturing specifications and thus means an economic loss.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] US3507943 [Patent Document 2] US4005169 [Patent Document 3] WO2020 / 183504 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] The main object of the present invention is to provide a system that can eliminate or at least significantly reduce the above-mentioned drawbacks. [Means for Solving the Problems]

[0008] According to the present invention, this object is achieved by creating a calendar having the features shown in the independent claims and implementing an operating method. Other features of the present invention are the subject of the dependent claims. [Advantages of the Invention]

[0009] According to the present invention, it is possible to eliminate or at least contain within a predetermined limit the loss of the axial phase of the engraved roller of the calendar for the heat treatment of web-shaped materials, thereby bringing about an obvious economic benefit related to the reduction of the production of out-of-specification materials. Furthermore, the control mechanism integrated into the calendar according to the present invention is a relatively simple mechanism from a constructive and functional point of view and can be easily attached to an existing calendar.

[0010] These and further advantages and features of the present invention will become even more apparent to those skilled in the art from the following description and the accompanying drawings, which are provided by way of example and should not be considered in a limiting sense. [Brief Description of the Drawings]

[0011]

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Figure 14A

Figure 14B

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Figure 16A

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Figure 18A

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Figure 19C

Figure 19D

Figure 20A - 20B

Figure 20C

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Figure 22

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Figure 24

Embodiments for Carrying Out the Invention

[0012] The calendar (1) according to the present invention is of the type comprising a structure formed by a support frame having a metal cross member (10) and side walls (11H, 11K), these side walls defining the extent of a space in which two rollers (R1, R2) are arranged with their respective longitudinal axes perpendicular to the side walls (11H, 11K), and defining a nip (N) that can be crossed by the material (W) to be processed. The rollers (R1, R2) are heatable rollers and are removably supported by the structure (10, 11H, 11K) so that, if desired, they can be removed and exchanged for other heatable rollers. The rollers (R1, R2) are designed to rotate in opposite directions at a predetermined angular velocity about their respective longitudinal axes. For this purpose, a drive unit (UM) is arranged and the rollers can be connected to the drive unit to control the rotation of the rollers (R1, R2) as described above. For the sake of simplicity, the material (W) is represented only by a horizontal dotted line in Figure 4, and the arrow above the dotted line indicates the direction in which the material itself continues.

[0013] The web-like material (W) is of the type normally used for manufacturing non-woven products. For example, this material can be composed of only thermoplastic fibers or a mixture of thermoplastic fibers and non-thermoplastic fibers such as cellulose, i.e., a material intended to be processed by passing it through a calendar equipped with heatable rollers.

[0014] Each roller (R1, R2) comprises an outer surface (100) having a relief (RR) arranged according to a predetermined pattern. The rollers (R1, R2) are arranged in a so-called "tip-tip" configuration, which means that the relief (RR) of one roller corresponds radially to the relief (RR) of the other roller.

[0015] Furthermore, each roller (R1, R2) has pins on each of the heads (T1, T2), and has a first pin (101) connectable to the drive unit (UM) and a second pin (102) through which a fluid for heating the roller can be introduced. The pins (101, 102) are aligned along the longitudinal axis of the roller, and when the roller is positioned at the operating position on the aforementioned structure, the longitudinal axis of the roller coincides with the rotation axis (r-r) of the roller.

[0016] A calendar structured in this way is described in Patent Document 3.

[0017] The following description is provided to illustrate a possible embodiment of a calendar that can be equipped with a control mechanism according to the present invention. The control mechanism will be described later in order to better explain its operation. It is understood that the structure of the calendar, as well as the members connecting the roller and the roller to the structure of the calendar, the means for moving the roller, and the method of heating the roller can be configured in any suitable manner other than those described below.

[0018] For example, the drive unit (UM) includes an electric motor (M) connected to two elastic axial joints (G1, G2) by a belt or chain transmission (not shown) included in a cutter (CM) disposed outside the structure (10, 11H, 11K). Each joint (G1, G2) is arranged corresponding to the rotation axis (r-r) of each roller (R1, R2), and includes a terminal portion (200) that slides axially with respect to the joint itself. An arm (201) is connected to the terminal portion (200) via a bearing (202). On the opposite side, the arm (201) is similarly connected to a hydraulic actuator (203) that is integral with the side wall (11K) of the structure. The terminal portion (200) is formed to be coupled to a power take-off portion (103) disposed at the end of the first pin (101) of each roller (R1, R2).

[0019] According to the embodiment shown in the attached drawings, the power take-off part (103) is fixed to the first pin (101) by a reinforcing ring (104). There are two joints, i.e., the same number as the number of the rollers (R1, R2), so two actuators (203) are provided, each actuator acts on a respective arm (201), and each of the arms (201) is connected to the end portion (200) of the corresponding joint (G1, G2). In FIG. 18A, the joint (G1) is in the engaged position on the first pin (101), while in FIG. 18B, the joint is in the disengaged position. The positioning of the joint at the engaged / disengaged position on the first pin (101) is controlled by the actuator (203). As shown in FIG. 18B, at the disengaged position of the joint, a space (y) is formed between the end portion (200) and the power take-off part (103), which enables the removal of the roller as further described below.

[0020] According to the example shown in the attached drawings, the aforementioned structure has a pair of side walls (11H, 11K) on each side, i.e., a pair of side walls (11H, 11K) on the drive unit side (UM) and a pair of side walls (11H, 11K) on the opposite side, such that it has two outermost walls (11K) and two innermost walls (11H). The distance between the inner walls (11H) is smaller than the distance between the outer walls (11K). The inner side walls (11H) have two overlapping recesses (300) suitable for partially accommodating the corresponding bearings (105) presented by the rollers (R1, R2) proximate to the respective heads (T1, T2) at the respective front portions (F).

[0021] Furthermore, an actuator (301), for example a hydraulic actuator, is attached to the front portion (F) of each inner side wall (11H), and its stem (302) is constrained to the front end of a lever (303). This has a recess which faces upwards and is hinged to each inner side wall (11H) by means of a pin (340) having a horizontal axis disposed at the rear of the lower recess (300), i.e., the rear of the recess (300) closest to the base (BA) of the structure. In practice, the pin (340) is on the side opposite to the connection point (305) of the stem (302) at the front end of the lever (303). The recess of the lever (303) is intermediate between the connection point (305) and the pin (340) and cooperates with each lower recess (300) to define the lower housing of the corresponding bearing (105) of the lower roller (R2). The actuators (301) are synchronized such that the two levers (303) rotate synchronously about their respective pins (340).

[0022] A lever (304) having a concave front portion (350) with a recess, preferably facing downwards, is applied to each outer side wall (11K), more precisely to the side facing each inner side wall (11H). The lever is constrained to the stem (306) of a corresponding hydraulic actuator (307) and is hinged to the wall (11K) by a pin having a horizontal axis (308) at an intermediate position between its concave front portion (350) and the connection point (309) for connection to the stem (306) of the actuator (307). The front portion of each lever (304) is intended to engage above the bearing (106) indicated by each roller (R1, R2) at a predetermined distance from the aforementioned bearing (105).

[0023] Above the lever (304), there is another lever (310), which is identical to the first lever (304) but arranged in a mirror - reflective manner, that is, the recesses at the front - end portions (311) face upward instead of downward. The other lever (310) is also constrained by the stem (312) of the corresponding hydraulic actuator (313) and is hinge - connected to the wall surface (11K) by respective pins (314) having a horizontal axis at an intermediate position between its front - end portion (311) and the connection point (315) to the stem (312) of the actuator (313). The front - side portion of the other lever (310) is intended to engage with the corresponding bearing (106) from below.

[0024] On the front - side portion (F) of each inner side - wall (11H), a further lever (316) connected to the corresponding hydraulic actuator (317) at its rear - side is attached. This further lever (316) has, at its front - side portion, a recess (318) that faces the rear - portion (P) of the wall (11H) in the operating position of the calendar, and is hinge - connected to the wall (11H) by respective pins (319) having a horizontal axis at an intermediate position between its front - side portion (318) and the connection point (320) to the stem of the actuator (317).

[0025] In fact, the following components are applied on each outer side - wall (11K): - A lower lever (304) controlled by an actuator (307), wherein the lever is connected to the wall (11K) by a pin (308) having a horizontal axis, the actuator controls the rotation of the lower lever around the pin (308), and the free front - end portion (350) of the lower lever (304) preferably has a recess shape with a downward - facing recess; and - An upper lever (310) controlled by an actuator (313), wherein the lever is connected to the wall (11K) by a pin (314) having a horizontal axis, the actuator controls the rotation of the upper lever around the pin (314), and the free front - end portion (311) of the upper lever (310) preferably has a recess shape with an upward - facing recess.

[0026] Similarly, the following components are also applied to each inner side wall (11H): - A lower lever (303) controlled by an actuator (301), wherein the lever is connected to the wall (11H) by a pin (340) having a horizontal axis, the actuator controls the rotation of the lower lever around the pin (340), and the middle part of the lower lever (303) preferably has a concave shape with an upward concave portion; and - An upper lever (316) controlled by an actuator (317), wherein the lever is connected to the wall (11H) by a pin (319) having a horizontal axis, the actuator controls the rotation of the upper lever around the pin (319), and when the calendar is in the operating position, the front part (318) of the upper lever (316) preferably has a concave shape with a concave portion facing the rear part (P) of the wall (11H).

[0027] Accordingly, in the calendar described here as an example, on each of its left and right sides, two lower levers (303, 304) and two upper levers (316, 310) are arranged at a predetermined distance (d) from each other, and the calendar is adapted to contact the corresponding bearings (105, 106) arranged on the rollers (R1, R2), and exerts forces (F1, F2, F3, F4) oriented in a non-matching direction on the bearings (105, 106). In practice, for each of the right or left sides of both rollers (R1, R2), the levers (303, 304, 310, 316) form two jaw members acting along parallel planes spaced apart by a predetermined value (d).

[0028] Referring to the examples shown in the attached drawings, the lower levers (303) and (308) each apply an upward thrust (F1) to the bearing (105) adjacent to the heads (T1, T2) of the lower roller (R2), and each apply a downward thrust (F2) to the outermost bearing (106) of the roller (R2). The upper levers (310) and (316) each apply an upward thrust (F3) to the outer bearing (106) of the upper roller (R1), and each apply a thrust (F4) towards the rear side (P) of the calendar to the bearing (105) adjacent to the heads (T1, T2) of the upper roller (R1).

[0029] As a result, the bending of the rollers (R1, R2) is reduced. In practice, the forces (F1, F2, F3, F4) act on parallel planes and non-coincident planes.

[0030] Referring to the examples shown in the attached drawings, inside each roller (R1, R2) there is a conduit (HT) for supplying a heating fluid, for example, a commercially available type of diathermic oil. For example, a diathermic oil of the type shown in Table 1 below can be used, where in Table 1, the letters A - E have the following meanings: A: Manufacturer B: Type C: Viscosity at 40 °C (cSt or mm 2 / s) D: Viscosity at 100 °C (cSt or mm 2 / s) E: Density at 15 °C (Kg / m 3 ) F: Flash point (°C)

[0031]

Table 1

[0032] For example, the selected diathermic oil is introduced into the duct (HT) at a temperature of 170°C to 200°C according to a specific treatment performed on the material (W) introduced between the rollers (R1, R2) of the calendar.

[0033] The duct (HT) is arranged along the longitudinal axis of the rollers (R1, R2) and has an inlet end (107) formed in the second pin (102) of the roller. A valve (108) is provided at the inlet end (107) of the duct (HT), through which a heating fluid can be introduced into the duct (HT) and the inlet (107) can also be blocked. The valve (108) is integral with the inlet (107) of the tube (HT) which is integral with the rollers (R1, R2). During operation, the valve (108) is open to allow the heating fluid to circulate in the duct (HT), while when the rollers (R1, R2) have to be removed from the calendar as described below, the valve is closed. Partition walls (S1, S2) are arranged at a predetermined distance from each head (T1, T2), and corresponding chambers (C1, C2) are formed inside the rollers (R1, R2) and in the vicinity of each head (TR) in such a way that the first chamber (C1) is further away from the inlet (107) and the second chamber (C2) is closer to this inlet.

[0034] The duct (HT) ends within the first chamber (C1), i.e., the outlet (109) of the duct (HT) is within the first chamber (C1). The first chamber has several holes (110) for communicating with a heat exchanger (111) that is coaxial with and external to the duct (HT). The second chamber (C2) also has more holes (110) for communicating with the heat exchanger (111). At the second pin (102), a second duct (RF) is arranged to form a return line for the heating fluid. The second duct (RF) is coaxial with and external to the first duct (HT), and the second duct (RF) has an inlet section (112) formed in the second head (T2) and an outlet section (113) to which a corresponding valve (114) is attached. The valve (114) enables the heating fluid to exit through the outlet section (113) of the second duct (RF) and also enables the outlet section (113) to be closed. The valve (114) is integral with the outlet (113) of the duct (RF), and the duct (RF) is integral with the rollers (R1, R2). In the operating state, the valve (114) is open to allow the heating fluid to pass through the second duct (RF), while the valve is closed when the rollers (R1, R2) have to be removed from the calender.

[0035] Accordingly, the heating fluid introduced into the duct (HT) at a predetermined pressure through the inlet (107) fills the first chamber (C1), circulates within the heat exchanger (111), enters the second chamber (C2), and exits through the second duct (RF). The inlet (107) of the delivery duct (HT) and the outlet (113) of the return duct (RF) are connected via their respective valves (108, 114) to a fluid heating and supply system known per se, which is only represented by the reference number "HTS" in the block diagram of FIG. 22.

[0036] According to the example shown in the attached drawings, the second pin (102) is intersected by both the delivery duct (HT) and the heated fluid return duct (RF), and the valves (108, 114) are both arranged from the same side and both at the free end of the second pin (102). In addition, the valves (108, 114) each have an outlet (180, 141) for inserting a pipe (not shown) for the supply and discharge of the heated fluid.

[0037] The jacket (100) of the rollers (R1, R2) is coaxial with and outside the heat exchanger (111), and receives the heat carried by the heated fluid from the heat exchanger.

[0038] For example, in order to ensure accurate heat exchange, the heat exchanger (111) inside the rollers (R1, R2) is formed from a spiral coil whose outer diameter corresponds to the inner diameter of the jacket (100). For example, the coil is formed by a tube having a rectangular cross-section wound in a spiral. According to the example described above, the exchanger (111) extends between the two heads (T1, T2) along the entire length of the rollers (R1, R2).

[0039] Preferably, the hydraulic joint is attached to the end of the pin (102), and this hydraulic joint is formed by an internal hollow body (400) having a first internal axial duct (401) arranged at the end of the duct (HT) and a second duct (402) coaxial with and external to the first duct (401), and the second duct (402) constitutes an extension of the heated fluid return conduit (RF). The duct (401) ends at the valve (108), while the duct (402) ends at the valve (114). The body (400) of the joint is integral with the rollers (R1, R2), and when the rollers are in the operating position, by means of suitable appendages (403), the body (400) is locked to the corresponding wall surface (11K) of the calendar (1). In this way, the valves (108, 114) are always located at the same point during the rotation of the rollers (R1, R2). In fact, the pin (102) rotates inside the joint (400) to which the valves (108, 114) are attached.

[0040] Preferably, the valves (108, 114) are applied to the side of the joint (400) facing the rear side (P) of the calendar (1) in the operating position of the rollers (R1, R2).

[0041] The valves (108, 114) are normally closed and are opened by respective actuators (508, 514) attached to predetermined positions on the side wall (11K) of the calendar (1). Referring in particular to the example shown in FIG. 14B, the wall (11K) has two pairs of actuators (508, 514), that is, one pair of actuators (508, 514) for each roller (R1, R2). The operation of this part of the calendar (1) will be described below with reference to FIGS. 19A and 19B which refer to a single valve (108), but the operation for both the inlet (108) and the outlet (114) of the heating fluid is the same for all valves: During the introduction of the heating fluid into the duct (HT), the piston (581) of the actuator (508) pushes the front base (181) of the valve (108), and its movement is transmitted to the lower element (182) of the internal group (182, 184) by the bridge (183) connecting the lower element (182) of the group to the upper element (184). Thus, the heating fluid can freely pass through the valve as indicated by the arrow "T" in FIG. 19A; conversely, when closing the valve (108), as shown in FIG. 19B, the piston of the actuator (508) is retracted, as a result, the lower body (182) of the aforementioned group (182, 184) is separated from the upper body (184), and the fluid cannot pass through the lower element (182) with which the outlet (180) is engaged, and leakage of the fluid through the outlet (180) is prevented.

[0042] In particular, as shown in FIGS. 22 and 23, each pin (101, 102) can be provided with an internal channel designed to allow air to pass through it in order to lower its temperature and maintain the integrity of the bearings (105, 106). Thus, it is possible to obtain control of the operating temperature of the bearings (105, 106) without providing an external cooling circuit such as is usually provided in a hot roller calendar. Referring to the example shown in FIGS. 22 and 23, each pin (101, 102) can form a channel (CC) extending parallel to the rotation axis (r-r) of the roller. The channel (CC) forms a heat-insulating chamber within the pin, which insulates the bearing from the heat transmitted by the heating fluid. Finally, air or even a heat-insulating material can be present within the channel (CC). As shown in the drawings, the channel (CC) extends beneath the bearings (105, 106).

[0043] The channel (CC) can also communicate with the outside by means of a first series of radial holes (RC) located near the relative heads (T1, T2) when the diameter of the pin is larger, and a second series of holes (SC) spaced a predetermined distance (a) from the first series of holes (RC) when the diameter of the pin is smaller. The axes of the second series of holes (SC) converge on the rotation axis (r-r) of the roller and present an inlet further from the head and an outlet closer to the head. Since the distance (a) is greater than the distance between the bearings (105, 106), the air flowing within the channel (CC) can cool both bearings. As shown in FIG. 24, in the pin (102) attached to the valves (108, 114) described above, the channel (CC) is coaxial with and external to the fluid return duct (RF).

[0044] External air enters the channel (CC) through the holes (SC), exits through the radial holes (RC), and provides proper insulation for the bearings (105, 106) of the rollers (R1, R2). FIG. 18C shows a nozzle (UR) for blowing air in the direction of the holes (SC) to further facilitate the circulation of air through the duct (CC) if necessary.

[0045] The air-cooled duct is arranged on the pins (101, 102) of both of the rollers (R1, R2), but this duct may be arranged only on the pin (102). Also in FIG. 22, the above-described cooling duct is provided on the pin (101).

[0046] Two bushes (B) can be applied to each pin (101, 102) of the rollers (R1, R2), and each of the bushes is preferably arranged at an intermediate position between two corresponding bearings (105, 106), and each bush is suitable for being engaged by an arm of an overhead crane (not shown) having a function of moving the rollers (R1, R2) between the calendar (1) and one or more parking stations or standby stations for the rollers.

[0047] For example, in order to enable the removal of the rollers (R1, R2) from the calendar (1), and to release the bearings (105, 106) and release the rollers from the seat (300), the levers (303, 304, 310, 316) are formed to rotate around the respective pins by corresponding actuators (301, 307, 313, 317). At this stage, the connection of the rollers to the drive unit is released, each power take-off part (103) is released, and the supply of the heating fluid is interrupted by closing the valves (108, 114) by the actuators (508, 514). The procedure for releasing the engagement of the rollers involved in the removal by the bridge crane, the procedure for closing the valves (108, 114), and the procedure for releasing the bearings (105, 106) are automatically managed by an actuator control unit (UE) that controls the above-described actuators. A block diagram regarding the control of the actuators by the actuator control unit (UE) is shown in FIG. 23.

[0048] As described above, the foregoing description has been provided to illustrate a possible configuration of a calendar that can be provided with a control mechanism according to the present invention, which mechanism generally relates to the support structure, the roller, and the member connecting the roller to the calendar structure, means for moving the roller, and a method for heating the roller itself, and is understood to be applicable to calendars having different structures.

[0049] Accordingly, the control mechanism according to the present invention can be equally applied to the heat treatment of web-like materials passing through a nip formed by two thermal engraving rollers arranged opposite each other in a tip-to-tip configuration, in particular, in a calendar. In this case, the bearing structure can have only two roller support walls, the heating system of the roller is not configured as described above but is configured according to different criteria, the roller is constrained to the bearing structure by restraint members other than the levers (304, 310, 303, 316) described above, and the roller is driven to rotate around its respective longitudinal axis by a motor member other than the drive unit (UM) described above. For example, as shown in FIGS. 20A to 20C, the drive unit (UM) includes two electric motors (M), one for each roller of the calendar.

[0050] Advantageously, according to the present invention, in order to ensure the maintenance of the axial phase of the rollers (R1, R2), control of uniform heating of the rollers is performed. A possible way of actually implementing this control includes detecting the axial elongation due to heating of the rollers (R1, R2). Generally, an unacceptable loss of axial phase is associated with different axial elongations of the two rollers exceeding a predetermined limit value (for example, 3 / 10 mm) according to the present invention. For example, the detection is performed using linear encoders (E1, E2) arranged on each side of the rollers (R1, R2) and can measure the axial elongation due to their heating.

[0051] As schematically shown in FIG. 22, each of the encoders (E1, E2) is connected to a programmable control unit (UCP), receives the electrical signals generated by the encoders, and compares them with each other. If the axial elongation of one roller differs from the axial elongation of the other roller by a value exceeding a predetermined threshold, the control unit (UCP) generates an alarm signal. The alarm signal can activate an acoustic and / or optical signal device (SAL) and / or a procedure for automatically restoring the normal operating state of the calendar.

[0052] The acoustic and / or optical signal can serve to warn the operator involved in the operation of the calendar, who can thus intervene to restore the normal operating conditions of the calendar, i.e., by manually adjusting the amount of hot fluid introduced into the rollers, the difference in axial elongation of the rollers (R1, R2) can be made less than a preset threshold.

[0053] The procedure for automatically restoring the normal operating conditions of the calendar includes the automatic adjustment of the amount of high-temperature fluid introduced into the rollers. In this case, for example, the control unit (UCP) is connected to the valve (108) arranged at the inlet (107) for introducing the high-temperature fluid into the rollers (R1, R2), and the valve (108) is an electromagnetic valve controllable by the control unit (UCP). By the controlled opening and closing of the electromagnetic valve (108), the control unit (UCP) can adjust the operating temperature of each roller (R1, R2) so that the difference in the axial elongation of the roller itself is lower than a preset threshold value. The positive or negative signal of the difference in the axial length thus detected can be used to identify the hottest roller. For example, when the difference D = dL1 - dL2 between the elongations (dL1, dL2) of the rollers (R1, R2) is positive, the control system interprets this condition as indicating a greater axial elongation of the roller (R1) relative to the roller (R2). Conversely, when the difference D = dL1 - dL2 between the elongations (dL1, dL2) of the rollers (R1, R2) is negative, the control system interprets this condition as indicating a greater axial elongation of the roller (R2) relative to the roller (R1).

[0054] As a result, when the difference in the axial elongation exceeds a predetermined threshold value, the control unit (UCP) reduces the flow rate of the heating fluid introduced into the hottest roller. Figure 24 shows, as an example, an operating condition in which the upper roller (R1) undergoes a greater elongation than the lower roller (R2), and as a result, the difference D = dL1 - dL2 is positive. In the enlarged detail of the figure, it can be seen that the greater axial elongation of the roller (R1) determines the loss of correspondence between the reliefs (RR) of the two rollers, particularly on one side of the calendar (the right side of the figure).

[0055] Alternatively, when the difference in the axial elongation exceeds a preset threshold value, the control unit (UCP) changes the set value of the heating unit of the hottest roller. In this case, the control unit (UCP) does not intervene in the valve (108), but commands a decrease in the set point of the heating unit that supplies fluid to the hottest roller. In Figure 22, the connection between the control unit (UCP) and the heating unit (HTS) is represented by the dashed arrow "UH". Also, in this case, what has been said regarding the sign of the difference in the axial elongation of the rollers (R1, R2) applies.

[0056] In both cases illustrated above, the system for heating the rollers (R1, R2) comprises several individually controllable heating units (HTS), each of which supplies hot fluid to the respective calendar roller.

[0057] In practice, the axial elongation of the rollers (R1, R2) is controlled by the active control of the operating temperature of the rollers themselves, and this active control is carried out by detectors (for example, encoders E1, E2), which are configured to detect the axial elongation of the rollers and are connected to the control unit (UCP) configured to adjust the operating temperature of the rollers according to the detection performed by the detectors in order to maintain the difference in the axial elongation of the rollers below a predetermined threshold value.

[0058] Relating to the configuration example shown in FIGS. 18A - 18C, each encoder (E1, E2) is a magnetic encoder attached to an arm (201) of an engagement / release mechanism for transmitting motion to the rollers (R1, R2). In this example, each encoder (E1, E2) includes a magnetic slider (MS) fixed to a plate (PM), and this plate (PM) is then fixed to the side portion of each arm (201). Accordingly, each translational movement of the arm (201) parallel to the axis (r - r) of each of the rollers (R1, R2) is accompanied by an equal translational movement of the magnetic slider (MS) on each of the encoders, and thus generates a position signal correlated with the position of the arm (201). The arrow "SA" in FIG. 18C (enlarged detail of FIG. 18A) indicates the thrust applied to the arm (201) by the elongation of the roller (R1), and this elongation of the roller (R1) corresponds to the translational movement of the slider (MS) of the encoder (E1) shown in this figure.

[0059] Axial elongation of any one of the calendar rollers (elongation along the direction of the r - r axis) means the thrust applied to each of the bearings (202) by this roller, and this thrust determines the translational movement of the corresponding arm (201) parallel to the axis (r - r) of the roller, and as a result, determines the translational movement of the magnetic slider (MS) converted by the encoder into the position signal transmitted to the control unit (UCP) programmed to intervene as described above. Since the actuator (203) is a pneumatic or hydraulic actuator operating at a relatively low pressure, the actuator (203) does not prevent the elongation of the roller, and as a result, does not prevent the translational movement of the arm (201), and thus the translational movement of the magnetic slider (MS).

[0060] According to the example shown in FIG. 21, the actuator (203) is connected to the wall (11K) of the calendar by a bracket (210), and an attachment (211) to which an inductive sensor (IS) is attached is provided on the bracket (210). The inductive sensor (IS) detects the distance of the arm (201) from the attachment (211). Thus, similar to the case exemplified above, each translational movement of the arm (201) parallel to the axis (r-r) of the relative rollers (R1, R2) includes an equal translational movement of the arm (201) detected by the inductive sensor (IS). Also, the arrow "SA" in FIG. 21 indicates the thrust applied to the arm (201) by the elongation of the roller (R1). In this example, an inductive sensor (IS) is provided for each of the calendar rollers. Further, also in this case, the sensor (IS) constitutes a transducer that generates the position signal of the arm (201) used by the control unit (UCP) as described above.

[0061] Actually, according to the present invention, the axial elongation of each roller of the calendar, the axial elongation due to heating of the roller, is detected by a sensor configured for this purpose and arranged in the calendar, and the programmable control unit compares the elongations of the rollers and is assumed to generate an alarm signal when the difference in these elongations exceeds a predetermined limit value.

[0062] The actuator control unit (EU) can be physically integrated with the control unit (UCP).

[0063] According to the foregoing description, the calendar according to the invention is a calendar for the treatment of web-shaped material (W), comprising a fixed structure (10, 11H, 11K, 300) adapted to support two heating rollers (R1, R2) arranged mutually so as to form a nip (N) crossable by the web-shaped material (W), each roller (R1, R2) having a surface relief (RR) arranged according to a predetermined pattern, said rollers (R1, R2) being arranged in a tip-to-tip configuration such that, in the operating setting of the calendar, the relief (RR) of one roller (R1) is radially opposed to the relief (RR) of the other roller (R2) corresponding to the nip (N), each of said rollers (R1, R2) being connected to a drive unit (UM) that determines its rotation at a predetermined angular velocity around its longitudinal axis (r-r), said rollers (R1, R2) being heated by heating means configured to heat each roller (R1, R2) of the calendar individually, and each roller (R1, R2) undergoing an axial elongation as a result of its heating, and each roller (R1, R2) comprising detection means (E1, E2; IS) adapted to detect the axial elongation of each roller (R1, R2), and a programmable control unit (UCP) connected to said detection means and said heating means, said programmable control unit being programmed to determine the difference in axial elongation between said rollers (R1, R2) detected by said detection means and to issue an alarm signal if the absolute value of this difference is greater than a predetermined limit value.

[0064] According to a particular method of implementation of the invention, the calendar according to the invention can have one or more of the following features: - The detection means consist of magnetic encoders (E1, E2). - The encoders (E1, E2) are linear encoders. - The detection means are constituted by inductive sensors. - The detection means act by being arranged at one end of the rollers (R1, R2). - The alarm signal controls the activation of an acoustic signal and / or an optical signal. - The alarm signal controls the heating means of the rollers (R1, R2) by lowering the temperature of the roller receiving the maximum elongation, and the control unit (UCP) determines the positive or negative sign of the difference. - The rollers (R1, R2) are rotationally driven around their respective longitudinal axes by a drive unit (UM) comprising one or two electric motors (M). - Internal ducts (HT, RF) through which a liquid supplied by the heating means can circulate are provided in both of the rollers (R1, R2).

[0065] A method for treating a web-like material (W) by means of a calendar for treating the web-like material, comprising a fixed structure (10, 11H, 11K, 300) adapted to support two heating rollers (R1, R2) arranged relative to each other so as to form a nip (N) that can be crossed by the web-like material (W), each roller (R1, R2) having a surface relief (RR) arranged according to a predetermined pattern, the rollers (R1, R2) being arranged relative to each other in a tip-to-tip configuration such that, in the operating setting of the calendar, the relief (RR) of one roller (R1) is radially opposed to the relief (RR) of the other roller (R2) corresponding to the nip (N), each of the rollers (R1, R2) being connected to a drive unit (UM) that determines its rotation at a predetermined angular velocity around its own longitudinal axis (r-r), the rollers (R1, R2) being heated by heating means configured to heat each roller (R1, R2) of the calendar individually, and each roller (R1, R2) undergoing an axial elongation as a result of its heating, according to the invention, detecting the axial elongation of each roller (R1, R2) by detecting means (E1, E2; IS), determining the difference between the axial elongations of the rollers (R1, R2) detected by the detecting means (E1, E2; IS), and generating an alarm signal if the absolute value of the difference is greater than a predetermined limit value.

[0066] According to a specific method of implementing the method according to the invention, - Detection of the axial elongation of the rollers (R1, R2) is performed by detection means comprising magnetic encoders (E1, E2) or inductive sensors (IS). - When the magnetic encoders are used, these encoders (E1, E2) are preferably linear encoders. - The detection means is preferably arranged and acts at one end of the rollers (R1, R2). - The warning signal controls the activation of an acoustic signal and / or an optical signal. - The warning signal is emitted by a control unit (UCP), which controls means for heating the rollers (R1, R2) by reducing the temperature of the rollers (R1, R2) that undergo greater elongation, and the control unit (UCP) evaluates the positive or negative sign of the difference as a function of the detection performed by the detection means.

[0067] In practice, in all cases, the details of the implementation remain within the scope of protection conferred by this patent according to the following claims, without departing from the concept of the solution adopted, and can vary in equivalent ways with respect to the individual elements described and illustrated and their mutual arrangement.

Claims

1. A calendar for processing web-like material (W), comprising a fixed structure (10, 11H, 11K, 300) adapted to support two heated rollers (R1, R2) arranged mutually so as to form a nip (N) crossable by the web-like material (W), each roller (R1, R2) having a surface relief (RR) arranged according to a predetermined pattern, the rollers (R1, R2) being arranged mutually in an end-to-end configuration such that in the operating setting of the calendar, the relief (RR) of one roller (R1) is radially opposed to the relief (RR) of the other roller (R2) corresponding to the nip (N), each of the rollers (R1, R2) being connected to a drive unit (UM) that determines its rotation at a predetermined angular velocity around its longitudinal axis (r-r), the rollers (R1, R2) being heated by heating means configured to heat each roller (R1, R2) of the calendar individually, and each roller (R1, R2) being configured to undergo axial elongation as a result of its heating, the calendar comprising detection means (E1, E2; IS) adapted to detect the axial elongation of each roller (R1, R2), and a programmable control unit (UCP) connected to the detection means and the heating means, the programmable control unit being programmed to determine the difference in axial elongation between the rollers (R1, R2) detected by the detection means and to issue an alarm signal if the absolute value of this difference is greater than a predetermined limit value.

2. The calendar according to claim 1, wherein the detection means are magnetic encoders (E1, E2).

3. The calendar according to claim 2, wherein the encoders (E1, E2) are linear encoders.

4. The calendar according to claim 1, wherein the detection means are inductive sensors (IS).

5. The calendar according to any one of claims 1 to 4, wherein the detection means are arranged and act on one end of the rollers (R1, R2).

6. The calendar according to any one of claims 1 to 5, wherein the alarm signal controls the activation of an acoustic signal and / or an optical signal.

7. The alarm signal controls the heating means of the rollers (R1, R2) by lowering the temperature of the roller undergoing the maximum elongation, The calendar according to any one of claims 1 to 6, wherein the control unit (UCP) determines the positive or negative sign of the difference.

8. The calendar according to claim 1, wherein the rollers (R1, R2) are rotated around their longitudinal axes respectively by a drive unit (UM) comprising one or two electric motors (M).

9. The calendar according to claim 1, wherein internal ducts (HT, RF) through which the liquid supplied by the heating means can circulate are provided on both of the rollers (R1, R2).

10. A method for the treatment of a web-like material (W) by a calendar comprising a fixed structure (10, 11H, 11K, 300) adapted to support two heated rollers (R1, R2) arranged relative to each other so as to form an intersectable nip (N) by the web-like material (W), each roller (R1, R2) has a surface relief (RR) arranged according to a predetermined pattern, the rollers (R1, R2) are arranged relative to each other in an end-to-end configuration such that in the operating setting of the calendar, the relief (RR) of one roller (R1) is radially opposed to the relief (RR) of the other roller (R2) corresponding to the nip (N), each of the rollers (R1, R2) is connected to a drive unit (UM) that determines its rotation at a predetermined angular velocity around its longitudinal axis (r-r), the rollers (R1, R2) are heated by heating means configured to heat each roller (R1, R2) of the calendar individually, and each roller (R1, R2) is configured to undergo an axial elongation as a result of its heating, the method comprising detecting the axial elongation of each roller (R1, R2) by detection means (E1, E2; IS) adapted to detect the axial elongation of each roller (R1, R2), determining the difference in the axial elongation between the rollers (R1, R2) detected by the detection means, and generating an alarm signal when the absolute value of the difference is greater than a predetermined limit value.

11. The method according to claim 10, wherein the detection of the axial elongation of the rollers (R1, R2) is performed by detection means comprising magnetic encoders (E1, E2) or inductive sensors (IS).

12. The method according to claim 10, wherein the detection means is arranged and acts on one end of the rollers (R1, R2).

13. The method according to claim 10, wherein the warning signal controls the activation of an acoustic signal and / or an optical signal.

14. The warning signal is emitted by a control unit (UCP), which controls the heating means of the rollers (R1, R2) by lowering the temperature of the roller that undergoes a greater elongation, The method according to claim 10, wherein the control unit (UCP) determines the positive or negative sign of the difference as a function of the detection performed by the detection means.

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