Single-face corrugator for producing corrugated board from continuous flexible components using an extrusion unit

Abstract

The single-faced corrugator (1) comprises a carrier frame (3) for accommodating a first corrugating roller (15) and a second corrugating roller (17) which are meshed with each other and mounted in the carrier frame (3). The single-faced corrugator also comprises a pivot structure which is pivoted to the carrier frame about a pivot axis (29) and is provided with a first guide roller (32) and a second guide roller (35) which are pivotally supported on the pivot structure for rotation. A continuous flexible member is guided around the guide rollers. In addition, a control system (41, 43) is provided which is suitable for moving the pivot structure into a working position and a raised position, wherein in the working position the continuous flexible member (31) is pressed against the second corrugating roller (17), and in the raised position the first guide roller (32) and the second guide roller (35) are spaced apart from the second corrugating roller (17).

Description

Technical Field

[0001] The present invention relates to machines for manufacturing corrugated board. More particularly, the present invention relates to improvements in corrugating machines or so-called "single face corrugators". Background Art

[0002] Corrugated board is manufactured starting from a smooth paper web unwound from a suitable reel. In its simplest form, corrugated board consists of a smooth paper web and a corrugated paper web bonded together along the ridges of the corrugated web. Usually, it is necessary to add to this basic structure a second smooth paper web, which is glued to the corrugated paper web so that the latter is sandwiched between the two smooth paper webs, also called a liner. In some cases, additional structures with a series of corrugated paper webs sandwiched between the smooth paper webs are added to this structure consisting of three paper webs.

[0003] Single-faced corrugated paperboard is produced by a "single-faced corrugator" comprising a pair of intermeshing corrugating rollers between which a first smooth paper web is fed. The first smooth paper web is thermally deformed into the nip between the two corrugating rollers, and it becomes a grooved paper web. Adhesive is applied to the groove ridges of the grooved paper web bonded to one of the corrugating rollers, and the smooth paper web is applied under pressure and heat to the grooved paper web provided with the adhesive.

[0004] A press unit is provided, the press unit comprising at least one press member pressed against one of the corrugating rollers for bonding a grooved paper web and a smooth paper web to each other. The smooth paper web and the grooved paper web pass between the corrugating roller and the press member.

[0005] In some single-face corrugated machines, the pressing unit comprises a continuous flexible member in the form of a belt, which is driven around a guide roller. Single-face corrugated machines of this type are disclosed in US9, 545,769, EP0698752, US10,293,588, US2015 / 0122423, US5,512,020, EP2805810, EP2792477, US5,951,817, US2014 / 0345804, EP0850753, JP10-710, JP2001-38830, JP10-709.

[0006] US 2,638,962 discloses a corrugating machine comprising a squeeze belt driven around two guide rollers, wherein a first guide roller is rotatable about a fixed axis relative to a supporting structure and a second guide roller is movable by a rotational movement about the fixed axis of the first guide roller. As the belt moves away from the corrugating rollers, it presses against an outer drum which keeps the belt stretched.

[0007] JP11105172 discloses a corrugator having a squeeze belt driven around three rollers. A complex actuator system drives the movement of two belt guide rollers to control the traction of the belt and keep the belt correctly guided.

[0008] Another corrugator is disclosed in JP2962660, which has a pressing belt and a member for controlling the stretching and guiding the belt. Also in this case, the belt is guided by a complex system, which consists of three guide rollers and the associated actuators controlling their movement.

[0009] EP3556548 discloses a single-face corrugated machine with a mechanism for replacing corrugated rollers. The single-face corrugated machine also includes a pair of fixed axis guide rollers around which a squeeze belt is driven. When the corrugated rollers are removed from the single-face corrugated machine, the squeeze belt is lifted.

[0010] Continuously flexible components are complex, costly machine elements, given the very high operating temperatures and operating traction forces they must withstand. They are subject to wear and must be replaced regularly. Replacement results in machine downtime. Replacement operations must be performed carefully by trained personnel in order not to damage the new continuously flexible component that is installed in place of the old one.

[0011] When manufacturing various types of corrugated board, the fluted paper web has different shapes and sizes of flutes, which necessitates the replacement of the corrugating rollers. In modern single-faced corrugating machines, two intermeshing corrugating rollers are mounted in a roller box or drum to simplify this operation. Several roller boxes or drums contain pairs of different corrugating rollers for the manufacture of different corrugated boards. Roller replacement is quick and simple. However, it may encounter obstacles when there is an extrusion unit. Replacing the corrugating roller requires that the corrugating roller in the single-faced corrugating machine be removed from the extrusion element. This operation requires complex mechanical solutions. For example, US2007 / 0084565 discloses a single-faced corrugating machine provided with a system for replacing a roller drum or a roller box for corrugating rollers.

[0012] Furthermore, the use of a continuous flexible member in the form of a belt requires careful control of its traction and its position during operation. This requires the use of complex control and guidance systems.

[0013] Therefore, in this field, there is a constant search for simpler and more efficient construction solutions aimed at facilitating and simplifying one or more of the above-mentioned operations. Summary of the invention

[0014] According to one aspect, a single facer corrugator having a novel structure designed to facilitate replacement of corrugating rollers is described herein.

[0015] The single-face corrugator comprises a load-bearing frame, i.e. a load-bearing structure, in which a first corrugating roller and a second corrugating roller can be mounted in mesh with each other. For example, the corrugating rollers can be mounted in a quickly replaceable roller drum or roller box. In addition, the single-face corrugator has a pivoting structure, which is pivoted to the load-bearing frame about a pivot axis. A first guide roller rotatably supported about a first rotation axis and a second guide roller rotatably supported about a second rotation axis are associated with the pivoting structure.

[0016] The first guide roller, the second guide roller and the pivot structure are part of an extrusion assembly or unit. A continuous flexible member is guided around the guide roller. The continuous flexible member may be composed of a belt. The continuous flexible member includes a first branch, the first branch faces the second corrugating roller and is defined between the first guide roller and the second guide roller. The continuous flexible member also includes a second branch, which is opposite to the second corrugating roller.

[0017] The axes of rotation of the first guide roller and the second guide roller are approximately substantially parallel to each other and to the axis of the corrugating roller. Furthermore, the axes of rotation of the guide roller and the corrugating roller are substantially parallel to a pivot axis about which the pivot structure is pivoted to the carrier frame. The parallelism between the above axes is not exact, but in the sense that small deviations from this parallelism can be provided and controlled, for example, to adjust the position of the continuous flexible member and the traction forces to which the continuous flexible member is subjected, as will be apparent from the description outlined below.

[0018] The single face corrugator also includes a control system adapted to rotate the pivot structure between the pivot structure and the carrier frame about a pivot axis. More specifically, the control system can displace the pivot structure to a working position in which the continuous flexible member is pressed against the second corrugating roller and a raised position in which the first guide roller and the second guide roller are spaced apart from the second corrugating roller.

[0019] The pivot axis between the pivot structure and the carrier frame may be substantially coincident with the axis of one of the guide rollers. However, the pivot axis is preferably spaced apart from the two axes of rotation of the guide rollers. This makes the system more efficient because it allows better spacing of the guide rollers from the underlying corrugating rollers when the pivot structure is lifted.

[0020] In order to facilitate the replacement of the corrugating rollers and avoid or reduce the risk of accidental collision between the corrugating rollers and the continuous flexible member, the single-face corrugator preferably comprises a stretching device, which is suitable for stretching the continuous flexible member when the hinge structure is in the raised position. The stretching device is suitable for stretching the branch of the continuous flexible member opposite to the corrugating roller outwardly so that the branch of the continuous flexible member facing the corrugating roller is kept in a stretched state between the guide rollers and does not protrude downward due to a loose effect.

[0021] This allows preventing the lower branch of the continuous flexible member, ie the branch facing the area of ​​the corrugating rollers, from protruding into the area where a new pair of corrugating rollers will be inserted.

[0022] In some embodiments, one of the two guide rollers is adapted to be driven by a motor. In other embodiments, both guide rollers can be idle. In both cases, provision can be made for the corrugating rollers to have their own drive. If both guide rollers are idle, i.e. not motor-driven, the corrugating roller must have its own drive and it is also used to drive the continuous flexible member.

[0023] In an advantageous embodiment, the stretching device comprises a stretching rod extending substantially parallel to the axis of the first and second guide rollers and carried by a pivoting structure pivoted to the carrier frame. The stretching rod is arranged between the first and second branches of the continuous flexible member and can be moved relative to the first and second guide rollers to push the second branch of the continuous flexible member outwards, i.e. away from the guide rollers. In this way, when the pivoting structure is in the raised position and the continuous flexible member is spaced apart from the second corrugating roller, the first branch of the continuous flexible member is stretched between the first and second guide rollers.

[0024] The stretching rod can be actuated by a special actuator mounted on a pivot structure, for example. However, this is not necessary.

[0025] In fact, in a particularly advantageous embodiment, by which a simpler, more economical and more reliable structure is obtained, the stretching rod is activated by a bearing member associated with the carrying frame. In this way, the upward rotational movement of the articulated structure in a direction away from the pair of corrugating rollers causes the stretching rod to cooperate with the bearing member, which is associated with the carrying frame and which constitutes a kind of stop element, which moves the stretching rod relative to the articulated structure. This interaction between the bearing member and the stretching rod causes the first branch of the continuous flexible member to be pulled.

[0026] In some embodiments, provision may be made for the stretching rod to be supported by a pair of pivoting levers, which are articulated to the pivoting structure about an axis substantially parallel to the pivot axis of the pivoting structure to the load-bearing frame. The pivoting levers are adapted to cooperate with corresponding static supports associated with the load-bearing frame so that when the pivoting structure is rotated from the working position toward the raised position, the pivoting levers come into contact with the static supports and rotate relative to the load-bearing structure to stretch the continuous flexible member. The supports do not necessarily have to be rigidly connected to the load-bearing frame. For example, the supports may be resilient for a smoother operation of the stretching rod and for cushioning shocks between the supports and the pivoting levers.

[0027] In a possible embodiment, the articulated structure comprises a first articulated arm and a second articulated arm rigidly connected to each other, for example by a crossbar substantially parallel to the axis of rotation of the guide rollers. The first guide roller and the second guide roller are supported between the articulated arms. At least one arm is articulated to the carrier frame. Preferably, both arms are articulated to the carrier frame. An actuator, for example a linear actuator, for controlling the lifting and lowering movement of the articulated structure and for pressing the continuous flexible member against the second corrugating roller is associated with one or the other articulated arm, preferably with both articulated arms.

[0028] If the corrugating roller is mounted on a roller cassette, in an advantageous embodiment the roller cassette and the carrying frame are configured so that in the operating position the roller cassette lies on the supporting profile of the carrying frame. In this way, the thrust exerted by the pressing unit on the roller cassette helps to stabilize the position of the roller cassette of the corrugating roller. Contrary to what is provided in many single-face corrugators of the prior art, no complicated system for pushing the corrugating roller vertically upwards towards the pressing unit is required.

[0029] Further advantageous features and embodiments of the single-face corrugator are described hereinafter and are set forth in the appended claims, which are an integral part of the present description.

[0030] According to another aspect, there is further provided a method for operating the single face corrugated machine as described above. The steps of replacing the first corrugated roller and the second corrugated roller are as follows:

[0031] - lifting the articulated structure by moving the first guide roller and the second guide roller away from the first corrugating roller and the second corrugating roller;

[0032] - when the hinged structure is in the raised position, the continuous flexible member is kept stretched by means of a stretching device;

[0033] - removing the first corrugating roller and the second corrugating roller from the carrying frame;

[0034] - inserting a new first corrugating roller and a new second corrugating roller into the carrying frame;

[0035] - a descending pivot axis structure; and

[0036] - Pressing the continuous flexible member against the new second corrugating roller.

[0037] According to another aspect, a single-face corrugated board machine for manufacturing single-face corrugated board is disclosed, comprising a carrier frame, a first corrugated roller and a second corrugated roller that can be mounted in the carrier frame, which are mutually meshed and mounted in the carrier frame. The single-face corrugated board machine also comprises a pressing unit, which is adapted to be pressed against the second corrugated roller. The pressing unit comprises a first guide roller rotatably supported about a first rotation axis and a second guide roller rotatably supported about a second rotation axis. A continuous flexible member is guided around the guide roller.

[0038] The invention is characterized in that the first guide roller and the second guide roller are supported by a pivot structure, the pivot structure is pivoted to the carrier frame about a pivot axis, the pivot axis is substantially parallel to the axis of the first corrugating roller and the second corrugating roller, the pivot structure is associated with a control system suitable for rotating the pivot structure to a working position and a raised position, wherein the continuous flexible member is pressed against the second corrugating roller in the working position, and the first guide roller and the second guide roller are spaced apart from the second corrugating roller in the raised position.

[0039] The single face corrugator may comprise in combination the other features described herein, in particular one or more of the features outlined in the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention will become more apparent from the description and the accompanying drawings, which illustrate embodiments by way of non-limiting examples. More specifically, in the drawings:

[0041] Figure 1 shows a side view of a single-face corrugator in a working position;

[0042] Figure 2 Shows Figure 1 The single-face corrugated machine is relatively Figure 1 Side view seen from the opposite side;

[0043] Figure 2A shows a very simplified cross-section of a single face corrugator according to a vertical plane midway between the two sides;

[0044] Figure 2B A single-face corrugator is shown according to the middle vertical plane between the two sides. Figure 1 and Figure 2 A cross-sectional view at the position shown;

[0045] Figure 3 Shown with Figure 1 a similar side view with the extrusion unit raised;

[0046] Figure 4 Shown with Figure 2 a similar side view with the extrusion unit raised;

[0047] Figure 5 The single face corrugator is shown in FIG. Figure 3 and Figure 4 A cross-sectional view at the position shown;

[0048] Figure 6 Shows something like Figure 3 , with the roll box of the corrugating roll removed;

[0049] Figure 7 Shows something like Figure 4 , with the roll box of the corrugating roll removed;

[0050] Figure 8 Shown according to Figure 7 A cross-sectional view of a middle vertical plane of a single-face corrugated machine;

[0051] Fig. 9 Shows Figure 8 A magnified view of a detail with some parts removed;

[0052] Fig.10 Shown with Figure 6 a similar side view with the extrusion unit lowered;

[0053] Fig.11 Shown with Figure 7 A similar side view with the extrusion unit lowered;

[0054] Fig.12 Shown with Fig.11 A side view similar to the view of , wherein the actuator of the extrusion unit is in a separated state from the corresponding pivoting arm;

[0055] Fig.13 Shows the single-face corrugated machine Fig.12 an axonometric view of a position in which the continuous flexible member is partially withdrawn from the guide rollers;

[0056] Fig.14 Shown according to Fig.13 View of the single-face corrugator of line XIV-XIV;

[0057] Fig.15 and 16 Shows Fig.14 enlarged views of the details indicated by XV and XVI;

[0058] Fig.17 shows a top view of the extrusion unit;

[0059] Fig.18 Shown according to Fig.17 Views XVIII-XVII of;

[0060] Fig.19 Shown according to Fig.17 View of XIX-XIX;

[0061] Fig. 20 Shown according to Fig.17 A cross-sectional view of XX-XX;

[0062] Fig.21 Shown according to Fig.19 A cross-sectional view of XXI-XXI;

[0063] Fig. 22 Shown according to Fig.19 A cross-sectional view of XXII-XXII;

[0064] Fig.23 shows a partial isometric view of the extrusion unit on the side where the motor actuating the continuous flexible member is mounted;

[0065] Fig.24A and 24B shows a partial isometric view of the extrusion unit 21, showing a sensor for detecting the position of the continuous flexible member 31;

[0066] Fig.25A , 25B Two schematic side views of an extrusion unit are shown, illustrating the movement of one of the two guide rollers of the continuous flexible member to adjust its stretching;

[0067] Figures 26 and 27 show two schematic views of a pressing unit illustrating the movement of one of the guide rollers of the continuous flexible member to correct its distortion; and

[0068] Fig.28A , 28B Two schematic diagrams of a pressing unit are shown, illustrating the movement of one of the two guiding rollers of the continuous flexible member to correct its distortion. DETAILED DESCRIPTION

[0069] The overall structure of the single-sided corrugated machine 1 can be referred to Figure 1 , 2 2A and 2A, wherein the first two figures show side views of a single-face corrugated machine seen from two opposite sides, and Figure 2A A very simplified cross-section according to a vertical plane midway between the two sides is shown, in which only the essential components of the single face corrugator 1 are shown. Figure 2B A cross-section according to a vertical plane midway between the two sides of a single face corrugator is shown.

[0070] The single-face corrugator 1 comprises: a supporting frame 3 on which corrugating rollers are supported; and a pressing unit for pressing two paper webs forming a single-face corrugated board (not shown) against each other. The supporting frame comprises a first side wall 5 located on a first side of the single-face corrugator 1 and a second side wall 7 located on a second side of the single-face corrugator 1, see also for details Fig.14 and 17 The two side walls 5 and 7 are connected to each other by cross beams 9 and 11, as shown in FIG. Fig.13 and 14 , wherein the corrugating rollers of a single face corrugator 1 are removed. Typically, the first side is the side where the drive is located, and the second side is the operator side, i.e. the side where the operator can usually access the single face corrugator 1.

[0071] A roll cassette or roll drum 13 comprising a first corrugating roll 15 and a second corrugating roll 17 superposed thereon is inserted into the carrier frame 3. The roll drum 13 is replaceable, ie interchangeable, to change the properties of the corrugated web produced by the single face corrugator 1 using different corrugating rolls 15, 17.

[0072] The roller cassette 13 is supported in the carrying frame 3 of the single face corrugator 1 by means of two shaped support profiles 13.1 and 13.2, which cooperate with complementary support profiles 3.1 and 3.2 which are integral with the carrying frame 3. The roller cassette is inserted into the single face corrugator 1 on the side of the single face corrugator 3, usually on the side defined by the second side wall 7. Insertion on the opposite side or on both sides cannot be excluded.

[0073] Advantageously, the roller cassette 13 is inserted into the carrying frame 3 and supported on supporting profiles 3.1, 3.2, wherein the roller cassette 13 remains stationary due to the weight of the roller cassette and the corrugating rollers 15, 17 and due to the thrust of the pressing unit, as will be described below.

[0074] The corrugating rollers 15, 17 are known per se and therefore will not be described in detail. Each of them has a corrugated cylindrical surface, and the two grooved cylindrical surfaces mesh with each other at a corrugating nip defined between the two corrugating rollers 15, 17, through which a first smooth paper web passes and is corrugated due to the pressure applied by the two corrugating rollers.

[0075] The first corrugating roller 15 and only Figure 2AThe single face corrugator 1 is provided with an adhesive applicator 16 shown in a simplified cross section of FIG. 1 and applies adhesive to the groove ridges formed on the first web before applying adhesive to the second smooth web (while still adhering to the second corrugating roller 17). In order to bond the two webs, one grooved and one smooth respectively, the single face corrugator 1 comprises a pressing unit or assembly 21 which is arranged to act from top downwards on the upper part of the second corrugating roller 17 around which the two webs are guided.

[0076] The pressing unit or assembly 21 comprises a pivoting structure which in turn comprises a first pivoting arm 23 located on a first side of the carrying frame 3 and a second pivoting arm 25 located on a second side of the carrying frame 3. The two pivoting arms 23, 25 can be rigidly connected to each other, for example by means of a crossbeam 27. In the embodiment shown, the two pivoting arms 23, 25 are articulated to the carrying frame 3 about a pivoting axis 29 which is parallel to the axis of the corrugating rollers 15, 17 when the corrugating rollers 15, 17 are mounted in the single face corrugator 1.

[0077] The extrusion unit or assembly 21 also includes a continuous flexible member 31, such as a continuous belt. The continuous flexible member 31 is guided around a first guide roller 32 to rotate around a first rotation axis 33, and is guided around a second guide roller 35 to rotate around a second rotation axis 37. The guide rollers 32, 35 and the corresponding rotation axes 33, 37 and the continuous flexible member 21 are specifically shown in FIG. Figure 5 and Figure 8 in the cross-sectional view.

[0078] The overall operation of the single-face corrugated machine is easy to refer to Figure 2A . The first smooth paper web N1 is guided around the heated roller 20 and fed into the corrugating nip between the first corrugating roller 15 and the second corrugating roller 17, where it is permanently deformed, forming grooves parallel to the axis of rotation of the corrugating rollers 15, 17. The first paper web N1 remains adhered to the second corrugating roller 17 and receives adhesive applied by the adhesive applicator 16 on the grooves thus formed. Downstream of the adhesive applicator 16, the first corrugated web N1 is guided by the second corrugating roller 17 below the pressing unit 21 and more precisely between the corrugated surface of the second corrugating roller 17 and the continuous flexible member 31 acting on the second corrugating roller 17. The second smooth paper web N2 is guided around the heated roller 22 and fed between the first grooved paper web N1 adhered to the second corrugating roller 17 and the pressing unit 21, and more precisely below the continuous flexible member 31 of the pressing unit 21. The pressure exerted on the two webs N1, N2 in the nip between the pressing unit 21 and the second corrugating roller 17 causes the webs N1, N2 to adhere to each other. At the outlet of the single-face corrugator 1, a single-face corrugated board web SF is obtained, the structure of which is Figure 2A This can be seen in the enlarged view shown. Designated C is the adhesive that bonds the grooved web N1 to the smooth web N2.

[0079] The first guide roller 32 and the second guide roller 35 define a first branch of the continuous flexible member 31, which includes the portion of the continuous flexible member 31 between the two guide rollers 32, 35 facing the second corrugating roller 17. The first branch of the continuous flexible member 31 constitutes the active branch, i.e. the branch pressed against the second corrugating roller 17. The second branch or return branch of the continuous flexible member 31 is again defined between the guide rollers 32, 35 on the opposite side, i.e. opposite the second corrugating roller 17.

[0080] A gear motor 39 providing a rotational movement to the second guide roller 35 and thus to the continuous flexible member 31 is mounted on the first articulated arm 5 , whereas the first guide roller 32 is idly mounted on the articulated arms 23 , 25 .

[0081] In other embodiments not shown, no gear motor 39 is provided, and both guide rollers 32 and 35 are mounted idlingly on the pivot structure. In this case, the movement of the continuous flexible member can be provided by the friction of the second corrugating roller 17.

[0082] The first pivoting arm 23 is constrained to a first linear actuator 41, for example a cylinder-piston actuator, preferably of the hydraulic type. One end 41.1 of the linear actuator 41 is pivoted to the carrier frame 3, while a second end 41.2 of the linear actuator 41 is pivoted to the first pivoting arm 25. Arranged on the opposite side of the single facer 1 is a second linear actuator 43, which constrains the second pivoting arm 25 to the carrier frame 3. One end 43.1 of the linear actuator 43 is pivoted to the carrier frame 3, while a second end 43.2 of the linear actuator 43 is pivoted to the second pivoting arm 25. The two linear actuators 41, 43 control the pivoting movement of the pivoting structure comprising the pivoting arms 23, 25 and the crossbeam 27 around the pivot axis 29 to perform the operations to be described below.

[0083] Further details of the squeezing unit 21 will be described below. Specifically, the following aspects are described: details about the interconnection between the pivoting arms 23, 25 and the carrying frame 3 and the details of the system for facilitating the replacement of the continuous flexible member 31; details about the system for facilitating the replacement of the roller box or roller; and details about the system for controlling the traction and keeping the continuous flexible member 31 guided. It can be clearly seen from this description that the features of these three functions of the single-faced corrugator 1 are combined in the embodiment shown. However, they can be used separately from each other. For example, the features for facilitating the replacement of the corrugating roller can be used in a single-faced corrugator 1 that has a different system for replacing the continuous flexible member and / or a different system for controlling the traction and keeping the continuous flexible member guided. Similarly, the features and elements for facilitating the replacement of the continuous flexible member can be used with different systems for facilitating the replacement of the corrugating roller and / or different systems for controlling the traction and keeping the continuous flexible member guided. Similarly, the latter can also be used in a single-faced corrugator with different systems for changing the corrugating roller and / or for replacing the continuous flexible member.

[0084] Before describing the aforementioned aspects in more detail, reference is made here to Figures 1 to 7 Described is the movement performed by the single face corrugator 1 , more precisely by the pressing assembly or unit 21 , for removing the roller cassette 13 of the corrugating rollers 15 , 17 . Figure 1 and 2 A side view of a first and a second side of a single-face corrugating machine 1 having a roller box or drum 13 and corresponding corrugating rollers 15, 17 is shown. The pressing unit 21 is in a working position, i.e. in a lowered position. In this position, the continuous flexible member 31 is pressed against the upper part of the second corrugating roller 17, i.e. the corrugating roller arranged at a higher level in the roller box 13 resting on the supporting frame 3. In this working position, the actuators 41, 43 push the pressing unit 21 downwards. In the embodiment shown, each articulated arm 23, 25 has a support 23A and 25A. The two supports 23A, 25A are arranged to act together with the support 13A carried by the drum 13. The supports 23A, 25A are specifically Figure 2 , 4 , 5, and 7. One of the supports 13A is specifically Figure 2 Visible in.

[0085] When the single face corrugator 1 is in the working position, the articulated arms 23, 25 adopt an angular position defined by the resting of the supports 23A, 25A on the supports 13A of the roll cassette 13, which in turn rest on the supporting profiles 3.1, 3.2. The pressure exerted by the actuators 41, 43 holds the articulated arms 23, 25 in place and helps to keep the roll cassette 13 of the corrugating rollers 15, 17 in the correct position.

[0086] A stretching actuator as described below applies a traction force to the continuous flexible member 31 when the pressing unit 21 is in the working position to keep the continuous flexible member 31 adhered to the paper web (not shown) between the continuous flexible member 31 and the second corrugating roller 17. The traction force of the continuous flexible member reduces the thrust force applied by the actuators 41, 43 on the support 13A.

[0087] To replace the roller cassette 13, the pressing unit 21 is first rotated upwards with a rotational movement about the pivot axis 29. By this movement, the pressing unit 21 is brought into a raised position spaced apart from the roller cassette 13. The lower branch of the continuous flexible member 31, i.e. the branch facing the second corrugating roller 17, is held in traction between the first guide roller 32 and the second guide roller 35 by means of a mechanism to be described below.

[0088] The raised position of the pressing unit 21 and thus the raised position of the articulated structure and the guide rollers 32, 35 carried thereon are shown in FIG. Figure 3 In the two side views of 4 (first side of the single-face corrugated machine 1) and 4 (second side of the single-face corrugated machine 1), as well as in Figure 5 in the cross-sectional view.

[0089] Arranging the pivot axis 29 of the pivot structure at a distance from the rotation axis 33 of the first guide roller 32 and at a distance from the rotation axis 37 of the second guide roller 35 allows obtaining a larger spacing between the guide roller and the second corrugating roller 17, thereby facilitating removal of the roller cassette 13.

[0090] Providing the pressing unit 21 with a lifting and lowering movement about the pivot axis 29 makes it possible to obtain an extremely simple and reliable system for carrying out the various operations required of a single-face corrugator, in particular: keeping the continuous flexible member 31 under the pressure of the second corrugating roller 17 during the production of corrugated board; operations for replacing the roller box 13; operations for replacing the continuous flexible member 31.

[0091] When the articulated structure is in the raised position, the roller cassette 13 can be lifted from the supporting profiles 3.1 and 3.2 and can be removed from the single facer corrugator 1. In the illustrated embodiment, the roller cassette 13 is preferably removable by taking it out from the second side of the single facer corrugator 1, but the possibility of removing it from the first side of the single facer corrugator 1 cannot be excluded. Figure 6 , 7 8 show a side view and a cross-sectional view of the single face corrugator 1 after the roller cassette 13 has been removed.

[0092] After the roller cassette 13 is removed, it can be replaced with a roller cassette 13 having different corrugating rollers 15, 17, thereby producing another type of corrugated board.

[0093] like Figure 1 , Figure 2 and Figure 3 As clearly shown in FIG. 1 , when the pivoting structure including the first pivoting arm 23, the second arm 25 and the cross beam 27 moves away from the second corrugating roller 17, the continuous flexible member 31 tends to loosen and its first branch facing the second corrugating roller 17 tends to rest on the second corrugating roller 17. When the roller cassette 13 is removed, the first branch (lower branch) of the continuous flexible member 31 will hang downward, at least partially occupying the space where the new roller cassette 13 will be inserted. If the operator inserting the new roller cassette 13 does not pay enough attention and does not care to manually lift the first branch of the continuous flexible member 31, this may damage the continuous flexible member 31.

[0094] The continuous flexible member 31 is a very expensive machine element, both in terms of traction and in terms of operating temperature, given that it is designed to withstand extreme working conditions. In fact, the corrugating rollers are heated to accelerate the mutual adhesion of the webs forming the corrugated board, and the traction forces to which the continuous flexible member 31 is subjected are very high, thus generating a high pressure on the second corrugating roller 17, again accelerating the adhesion of the webs forming the corrugated board.

[0095] In the embodiment shown, in order to avoid the risk of damaging the continuous flexible member 31 during the replacement of the rollers 13, the pressing unit or assembly 21 comprises a stretching device, which is indicated as a whole with the reference numeral 51 and in particular at Figure 8 and 9 Visible in.

[0096] In the embodiment shown, the stretching device 51 comprises a stretching rod 53, which is arranged in a closed path defined by the continuous flexible member 31. The stretching rod 53 extends substantially parallel to the pivot axis 29 and is carried by the pivot structure. Thus, the stretching rod participates in the pivoting movement of the pivot structure around the pivot axis 29. When the extrusion unit 21 is in the working position, the stretching rod 53 is in the non-working position, preferably not in contact with the continuous flexible member 31, or in any case not exerting any considerable force on it. For this purpose, the stretching rod 53 can be accommodated in the space between the first guide roller 32 and the second guide roller 35.

[0097] When the pivot structure is moved from the working position ( Figure 1 , 2 ) to the raised position ( Figure 3 , 4 , 5), the stretching rod 53 is lifted together with the pivot structure, and at the same time it performs a movement relative to the first guide roller 32 and the second guide roller 35, thereby pushing the second branch of the continuous flexible member 31 from the inside, which second branch faces the opposite side of the second corrugated roller 17. Figure 8 and 9The final position occupied by the stretching rod 53 once the articulated structure has been brought to its fully raised position is shown. The stretching rod 53 of the stretching device 51 pushes the return branch of the continuous flexible member 31 outwards, deforming it and preventing the flexible member from loosening towards the first branch of the second corrugating roller 17. Basically, the first branch of the continuous flexible member 31 is kept stretched between the first guide roller 32 and the second guide roller 35. The traction force exerted on the continuous flexible member 31 is negligible. It is sufficient to avoid the first branch of the continuous flexible member 31 from slacking downwards.

[0098] In some embodiments not shown, the movement of the stretching rod can be driven by an actuator carried by the articulated structure comprising the articulated arms 23, 25 and the crossbar 27. However, in order to obtain a safer operation while making the structure simpler and thus reducing costs, it is advantageous to provide that the stretching device 51 is passively activated when the articulated structure is brought into the raised position.

[0099] To this end, the stretching rod 53 is carried by a mechanism that cooperates with a static element integrally constrained to the supporting frame 3 , causing the stretching rod 53 to move relative to the articulated structure 23 , 25 , 27 , due to this cooperation.

[0100] In the embodiment shown, the stretching rod 53 is carried by two pivoting levers 55, each of which is associated with a respective pivoting arm 23, 25. Figure 8 and Fig. 9 The two pivoting levers 55 are hinged about a pivot axis 57, only one of which can be seen in the figure, which is integrated into the pivoting arms 23, 25 and is essentially parallel to the pivot axis 29. Each pivoting lever 55 has a first end 55.1 constrained to the stretching rod 53 and a second end 55.2 arranged in the vicinity of the second guide roller 35. The second end of each pivoting lever 55 forms a movable support, which acts together with a corresponding support 59 mounted on the supporting frame 3. Each support 59 can be fixed or almost fixed, for example it can be an elastic support for cushioning the impact of the end 55.2 of the pivoting lever 55. The elastic member 59.1, for example a pneumatic spring, can gradually contract when the pivoting arms 23, 25 reach the maximum raised position. The contraction of the elastic member 59.1 allows the corresponding support 59 to be pivoted upwards under the thrust of the end 55.2 of the corresponding pivoting lever 55, while the latter's pivot point (axis 57) moves following the lifting of the pivoting structure 23, 25, 27 (see Fig. 9 ). The elasticity provided by each of the two elastic members 59 . 1 allows compensating for any extension or contraction of the continuous flexible member 31 , thereby ensuring that it is always adequately stretched by the stretching rod 53 .

[0101] like Fig. 9As shown, when the pivot structure comprising the pivot arms 23, 25 and the crossbeam 27, on which the stretching rod 53 is rotatably supported, is raised until it reaches a position of maximum distance from the second corrugating roller 27, the stretching rod rotates around the axis 57 due to the cooperation of the end 55.2 of the pivot lever 55 and the support 59. As a result, the stretching rod 53 pushes the second branch of the continuous flexible member 31, stretching the first branch of the continuous flexible member, thereby preventing it from tending to relax downwards and entering the area of ​​the roller box 13 of the mobile corrugating rollers 15, 17. Basically, as Figure 5 and 8 As is clearly shown in FIG. 5 , when the hinged structure is in the raised position, the continuous flexible member 31 is stretched between the two guide rollers 32, 35 and the stretching rod 53. This makes it easier to move the roller box 13 without the risk of damaging the continuous flexible member 31.

[0102] In some embodiments, the single face corrugator 1 may include means to facilitate the replacement of the continuous flexible member 31. In fact, this member is subject to wear due to the high thermal and mechanical stresses to which it is subjected.

[0103] To facilitate replacement of the continuous flexible member 31, a pivoting structure including the pivoting arms 23, 25 and the crossbeam 27 is constrained to the carrier frame 3 so as to be able to support the guide rollers 32, 35 in a cantilevered manner on one of the two pivoting arms and to allow the continuous flexible member 31 to be removed from the other side of the pivoting arm. In the example shown, as will be described in more detail below, the first pivoting arm 23 is constrained to the carrier frame 3 so as to be able to support the first guide roller 32, the second guide roller 35 and the second pivoting arm 25 in a cantilevered manner (they can be temporarily detached from the carrier frame 3 to allow the continuous flexible member 31 to be removed and replaced from the side of the second pivoting arm 25).

[0104] Specific reference diagram Fig.13 , 14 As shown in FIG. 23, the first pivot arm 23 comprises a crossbeam 23.3 rigidly connected to the pivot arm 23 and extending in a cantilever manner approximately parallel to the pivot axis 29. The pivot arm 23 with the corresponding crossbeam 23.1 defines two hinges 23.2 and 23.3 (see Fig.23 ), which are coaxial with each other and spaced apart in the direction of the pivot axis 29. Two hinges 23.2 and 23.3 form elements for constraining the pivot arm 23 to the carrying frame 3 on the side of the side wall 5.

[0105] Two mutually spaced hinges 23.2, 23.3 provide a constraint for the first pivoting arm 23. The arm 25 is also held in cantilevered fashion by means of a crossbeam 27 which connects the pivoting arms 23, 25 to each other. Finally, the guide rollers 32, 35 and the pivoting arms 23, 25 are supported by the hinge system 23.2, 23.3 which connects the pivoting arm 23 to the carrying frame 3. In this way, the pivoting arm 25 can be detached from the carrying frame 3, allowing an easy replacement of the continuous flexible member 31 as described below.

[0106] In the embodiment shown, the second pivoting arm 25 is constrained and pivotally connected to the supporting frame 3 by means of a hinge 25.1, as shown in FIG. Fig.14 The second pivot arm 25 is provided with a removable bracket 25.2 connecting the pivot arm 25 to the hinge 25.1, see the side view of the second side of the single-face corrugator 1 ( Figure 2 , 4 , 7, 11, 12). The function of the bracket 25.2 will be explained with reference to the sequence of operations for removing the worn continuous flexible member 31. These operations are Figure 7 , 8 and 10 to 13 are described in detail.

[0107] Figure 7 and 8 The preliminary operations necessary to clear the space required for replacing the continuous flexible member 31 are shown for the single facer corrugator 1 from which the roll cassette 13 has been removed.

[0108] from Figure 7 , 8 The pivot structure comprising the pivot arms 23, 25 and the crossbeam 27 with the two guide rollers 32, 35 is lowered by rotating about the pivot axis 29 until it reaches a position below the normal working position, i.e. below the position where the supports 23A, 25A of the pivot arms 23, 25 rest on the supports 13A of the roller box 13 located in the single-face corrugated machine 1.

[0109] The lowered position of the pivot structure is Fig.10 is shown on the side of the side wall 5, and Fig.11 and Fig.12 6 is shown as the side away from the side wall 7. The position of the pivot structure in this operation step is defined by the fixed support 61 and the movable support 63. The fixed support 61 is integrated with the supporting frame 3, more precisely, with the first side wall 5 of the supporting frame 3. The movable support 63 is integrated with the first pivot arm 23. During the step of replacing the continuous flexible member 31, the supports 61, 63 allow to define a lower position of the pivot structure and give greater stability to the pivot arm 23.

[0110] At the lower part of the hinge structure, such as Fig.10 , 11 12 , the continuous flexible member 31 is no longer held in traction by the stretching rod 53 , and its first branch is loosely suspended in the space left by the roller box 13 with the corrugating rollers 15 , 17 .

[0111] When this position is reached, in order to remove the continuous flexible member 31, the second pivoting arm 25 is first separated from the side wall 7 of the supporting frame 3. To this end, Fig.11 and 12 As shown, the bracket 25.2 is separated from the rest of the arm 25 and rotated downward about the pivot axis 29. In addition, as shown in Fig.11 and 12 As shown, the actuator 43 is separated from the arm 25.

[0112] In some embodiments not shown, the articulated arm 25 may not be articulated to the carrier frame 3 by means of its hinge. In this case, no bracket 25.2 is provided, and the disengagement of the articulated arm 25 from the carrier frame 3 is faster, since it only requires the actuator 43 to be separated.

[0113] exist Fig.12 In the embodiment of the present invention, the arm 25 is substantially separated from the carrying frame 3. It is held in a cantilever manner by a crossbeam 27 constrained to the pivoting arm 23. This is constrained to the carrying frame 3 via two hinges 23.2, 23.3, an actuator 41 and a support 63 resting on a support 61.

[0114] Therefore, if Fig.13 As shown in the isometric view of FIG. 3 , the continuous flexible member 31 can be removed from the guide rollers 32, 35. Once the worn continuous flexible element 31 is removed, it can be replaced with a new continuous flexible element 31. The guide rollers 32, 35, the continuous flexible member 31 and the pivoting arms 23, 25 are returned to the original position by the reverse operation of the above operation. Figure 6 , 7 , the lifted position of 8.

[0115] In this position, the new continuous flexible member 31 is held in traction by the stretching rod 53, so that the first branch of the continuous flexible member 31 is in a straight line shape and leaves a space below, in which the first corrugating roller 15 and the second corrugating roller 17 are inserted into the roller box 13 ( Figure 3 , 4 and Figure 5 ). Subsequently, the extrusion unit including the continuous flexible member 31, the guide rollers 32, 35, the pivoting arms 23, 25 and the crossbeam 27 is lowered to the working position ( Figure 1 and Figure 2 ).

[0116] When the single face corrugator 1 is in the working position, the continuous flexible member 31 must be kept properly stretched and guided around the guide rollers 32, 35. The width of the continuous flexible member 31 and the axial length of the guide rollers 32, 35 are very large relative to the length of the continuous flexible element. This makes guiding the continuous flexible member 31 particularly critical. In order to keep the continuous flexible member 31 properly stretched and guided, the following specific references are provided: Figures 14 to 23 The adjustment and guiding arrangement of the continuous flexible member 31 is described. This system is used to maintain the correct stretching of the continuous flexible member 31, to prevent or correct any slipping in the transverse direction, i.e. displacement along the axis of the guide rollers 32, 35, and to avoid or correct the distortion of the continuous flexible member 31. Twisting occurs when the two edges of the continuous flexible member 31 advance unevenly, so that the line of the continuous flexible member 31 that was originally parallel to the axis of rotation of the guide rollers 32, 35 is displaced so that its position is no longer parallel to such axis of rotation.

[0117] In the embodiment shown, the articulated arms 23, 25 are associated with respective actuators which independently adjust the distance between the axes of rotation of the two guide rollers 32, 35 for both sides of the single facer 1. Furthermore, another actuator is provided on one of the two sides of the single facer 1, which is associated with one end of one of the two guide rollers 32, 35 and adjusts the inclination of the axis of this guide roller in the transverse direction, preferably substantially orthogonal to the direction of adjustment of the center distance of said guide rollers.

[0118] More specifically, the first guide roller 32 is supported on the first pivot arm 23 by means of a first support 32.1 and on the second pivot arm 25 by means of a second support 32.2. Similarly, the second guide roller 35 is supported to the first pivot arm 23 by means of its first support 35.1 and to the second pivot arm 25 by means of a second support 35.2.

[0119] In the illustrated embodiment, as described in detail below, the supports 35.1 and 35.2 of the second guide roller 35 are mounted in a fixed position relative to the first and second pivot arms 23, 25, while the supports 32.1 and 32.2 of the first guide roller 32 are mounted so that they can move relative to the first and second pivot arms 23, 25 in a controlled manner.

[0120] In the embodiment shown, the first support 32.1 of the first guide roller 32 and the second support 32.2 of the first guide roller are mounted in respective movable units, one of which is located in the Fig. 20 The cross-sectional view of the first guide roller 32 is indicated in detail with reference numeral 71. The supports 32.1 and 32.2 are pivot supports, ie they allow the inclination of the axis of rotation 33 of the first guide roller 32 to be varied in the manner described below for the purpose described below.

[0121] The mobile unit 71 comprises a first support 32.1 of a first guide roller 32, and is connected to the first pivot arm 23 as described below. For a similar mobile unit 72, the second support 32.2 of the first guide roller 32 is mounted in the same manner on the second pivot arm 25, with reference to Fig.17 , 18 , 19 and 20.

[0122] Specific reference Fig. 20 , the mobile unit 71 has a base 71.1 for the first support 32.1 of the first guide roller 32. The mobile unit 71 is constrained to the pivoting arm 23 by means of a rocker 73, one end of which is pivoted to the mobile unit 71 and the other end of which is pivoted to the pivoting arm 23. The axes for pivoting the rocker 73 to the arm 23 and the mobile unit 71 are indicated with reference numerals 73.1 and 73.2, respectively.

[0123] The mobile unit 71 is further constrained to the articulated arm 23 by means of a first actuator 75 for adjusting the traction of the continuous flexible member 31. In the embodiment shown, the first actuator 75 is a linear actuator, for example a cylinder-piston actuator, preferably of the double-acting hydraulic type.

[0124] In the embodiment shown, the actuator 75 comprises a cylinder 75.1 formed in the mobile unit 71, in which a piston 75.2 slides. In turn, the rod of the piston 75.2 is pivoted in 75.3 to the first pivoting arm 23. The movement of the actuator 75 results in the pivoting of the rocker arm 73 and the following movement of the axis of rotation 33 of the first guide roller 32 relative to the pivoting arm 23.

[0125] A similar arrangement is provided for connecting the second support 32 . 2 of the first guide roller 32 to the second pivoting arm 25 .

[0126] Acting on the two actuators 75 associated with the two supports 32 . 1 and 32 . 2 allows the traction of the continuous flexible member 31 to be varied, due to the variation of the distance between the axes of rotation 33 and 37 of the two guide rollers 32 , 35 .

[0127] The two actuators 75 on both sides of the single facer 1 can be actuated independently of each other in the sense that they allow independent adjustment of the position of the respective supports 32.1 and 32.2 of the first guide roller 32 relative to the respective supports 35.1 and 35.2 of the second guide roller 35. This allows maintaining proper guiding and proper stretching of the continuous flexible member 31. Independent actuation of the actuators 75 allows changing the inclination of the rotation axis 33 of the first guide roller 32 so that it is not completely parallel to the rotation axis 37 of the second guide roller 35. Such a change in inclination can be used, for example, to compensate or correct a twist of the continuous flexible member 31.

[0128] The actuator 75 can be controlled by a control unit (not shown) based on signals from sensors (not shown) with which the single-face corrugator 1 is equipped. For example, a load cell can be provided for detecting the traction of the continuous flexible member 31, which corresponds to the determined pressure on the second corrugating roller 17 and thus to the determined bonding pressure between the smooth web and the grooved web. Furthermore, a sensor can be provided that reads the position of one or both longitudinal edges of the continuous flexible member 31. Alternatively, the traction can be determined simply from the pressure of the hydraulic fluid used to control the actuator 75.

[0129] More specifically, based on the signals of these sensors, possible displacements of the continuous flexible member 31 can be corrected by differentially acting on the two actuators 75, thereby causing a change in the inclination of the rotation axis 33 of the first guide roller 32. Since both actuators 75 act simultaneously, the rotation axis 33 is translated parallel to itself by imparting the same movement thereto, thereby causing a change in the traction of the continuous flexible member 31.

[0130] In the embodiment shown, the pivot axis 73.1 of the rocker arm 73 associated with the pivot arm 25 is fixed (see Fig.18 ). On the other hand, the pivot axis 73.1 of the rocker arm 73 associated with the pivot arm 23 is movable to exert a further adjustment movement on the first guide roller 32. This further movement will be more apparent by reference to 19, 20 and 21. The pivot axis 73.1 of the rocker arm 73 associated with the first pivot arm 23 comprises an eccentric 73.3, which is accommodated in a base 73.4 of the pivot arm 23 (see Fig. 20 ). The eccentric 73.3 rotates in the base 73.4 about an axis 73.5 which is parallel to the pivot axis 73.1 of the rocker arm 73 but spaced therefrom. In the illustrated embodiment, the rotation of the eccentric 73.3 is controlled by a linear actuator 77 (e.g. an electric jack) by means of a lever 79 (see Fig.19 ) for control.

[0131] The rotation of the eccentric 73.3 about the axis 73.5 causes a displacement of the pivot axis 73.1 of the rocker arm 73 relative to the pivot arm 23. Fig. 20 In the figure, the general direction of this displacement is indicated by the reference numeral f73. This direction is transverse to the direction of displacement imparted by the linear actuator 75, indicated by the reference numeral f75. Thus, on the side of the first pivoting arm 23, the first support 32.1 of the first guide roller 32 can be displaced according to two directions that are substantially orthogonal to each other. The displacement imparted by the actuator 75 according to the arrow f75 ( Fig. 20) is used to adjust the traction of the continuous flexible member 31 and it can be coordinated with the corresponding movement imparted by the corresponding actuator 75 of the second support 32.2. The displacement imparted by the actuator 77 by means of the eccentric 73.3 can be used to correct the displacement of the continuous flexible member 31 parallel to the axis of rotation of the guide rollers 32, 35, for example a lateral sliding. A homologous displacement of the support 32.2 on one side of the second articulated arm 25 is not necessary.

[0132] Figures 24A to 28B Further details are shown to aid in understanding the control of the traction force and position of the continuous flexible member 31. More particularly, Fig.24A and 24B Details of the articulated arms 23 , 25 and the continuous flexible member 31 guided around guide rollers 32 and 35 are shown in an axonometric view. Fig.24A and 24B Sensors are shown for detecting the displacement of the continuous flexible member 31, which provide signals to the central unit 101 controlling the above-mentioned actuators in order to keep the continuous flexible member 31 in the correct position.

[0133] In the embodiment shown, at least one respective sensor 103, for example a magnetic sensor, is arranged on each articulated arm 23, 25, which detects the twisting of the continuous flexible member 31. To this end, an element detectable by the sensor 103, for example two magnets 105, is inserted along the two edges of the continuous flexible member 31. The two magnets 105 are arranged on a line orthogonal to the edges of the continuous flexible member 31. Thus, if the continuous flexible member 31 shows no twisting or bending, they pass simultaneously in front of the respective sensor 103. The twisting of the continuous flexible member 31 causes the two magnets 105 to be offset relative to each other in the direction of advancement of the continuous flexible member 31. This is detected by the delay of the signal of one sensor 103 with respect to the signal of the other sensor, and this provides the central unit 101 with information about the need to correct the two actuators 75 by means of differential actuation.

[0134] A possible lateral sliding of the continuous flexible member 31 can be detected with a corresponding arrangement of sensors. In the illustrated embodiment, a sensor 107 is provided on one of the articulated arms 23, 25 and more specifically on the articulated arm 23 in the illustrated example. The sensor 107 can be an optical sensor, for example comprising one or more photoelectric elements arranged orthogonally to the edge of the continuous flexible member 31 to identify its position. For example, a fiber optic sensor can be used, which has a plurality of optical fibers along a direction orthogonal to the edge of the continuous flexible member, which detects light signals from opposing emitters located on opposing faces of the continuous flexible member 31. A lateral sliding of the continuous flexible member 31 in one direction or the other results in a change in the number of photoelectric elements or optical fibers that see the light signal emitted by the opposing emitters. The central unit 101 uses the obtained signal to emit a control signal for the linear actuator 77 for correcting any sliding.

[0135] The possibility of using a combined movement of actuators 77 and 75 to correct for sliding and twisting movements cannot be excluded.

[0136] Fig.25A and 25B It is shown in more detail how the control of the traction of the continuous flexible member is performed by means of simultaneous actuation of the actuators 75 .

[0137] exist Fig.25A In the embodiment, the continuous flexible member 31 is not stretched, but Fig.25B In the embodiment of the present invention, due to the influence of the equal extension of the two actuators 75 and the follow-up movement of the guide roller 32 away from the guide roller 35, it is stretched, thereby keeping the axes of the two guide rollers parallel to each other.

[0138] 26 and 27 show the displacement of the first guide roller 32 caused by the linear actuator 77 to correct the lateral sliding movement of the continuous flexible member. More specifically, FIG. 26 is a rear view according to XXVI-XXVI of FIG. 26 , while FIG. 27 is a side view according to XXVII-XXVII of FIG. 26 of the extrusion unit 21. The two tilted positions of the first guide roller 32 are indicated with reference numerals 32X and 32Y. For greater clarity, the displacement is represented as being much greater than the actual displacement.

[0139] Fig.28A and 28B The displacement of the first guide roller 32 controlled by the differential stroke of the actuator 75 is shown in a top view of the pressing unit 21 to correct possible distortion of the continuous flexible member 31. The positions of the first guide roller 32 tilted in opposite directions obtained by the differential action of the actuator 75 are indicated by reference numerals 32Z and 32W. As in FIGS. 26 and 27, in Fig.28A , 28BThe displacement is also shown as being much larger than the actual displacement in order to make the representation clearer.

[0140] The present invention has been described in terms of various specific embodiments. However, it will be apparent to those skilled in the art that many modifications, changes and omissions may be made without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A single-face corrugated paperboard machine (1) for manufacturing single-face corrugated paperboard, comprising: Load-bearing frame (3); a first corrugating roller (15) and a second corrugating roller (17), the first corrugating roller and the second corrugating roller being meshed with each other and being associated with the supporting frame (3); A pivot structure, pivotally connected to the supporting frame about a pivot axis (29); a first guide roller (32) rotatably supported on the pivot structure about a first rotation axis (33); a second guide roller (35) rotatably supported on the pivot structure about a second rotation axis (37); a continuous flexible member (31) guided around the first guide roller (32) and the second guide roller (35); wherein the continuous flexible member (31) comprises a first branch facing the second corrugating roller (17) and a second branch opposite the second corrugating roller; a control system (41, 43) capable of moving the pivot structure to a working position in which the continuous flexible member (31) is pressed against the second corrugating roller (17) and a raised position in which the first guide roller (32) and the second guide roller (35) are spaced apart from the second corrugating roller (17); as well as A stretching device (51) capable of stretching the continuous flexible member (31) when the pivot structure is in a raised position, the stretching device (51) comprising a stretching rod (53) extending substantially parallel to the axis of the first guide roller (32) and the second guide roller (35) and carried by the pivot structure pivotally connected to the carrying frame (3); wherein the stretching rod (53) is located between the first branch and the second branch of the continuous flexible member (31); and wherein the stretching rod (53) is movable relative to the first guide roller (32) and the second guide roller (35) to push the second branch of the continuous flexible member (31) and stretch the first branch of the continuous flexible member between the first guide roller (32) and the second guide roller (35) when the pivot structure is in the raised position and the continuous flexible member (31) is spaced apart from the second corrugated roller (17).

2. The single-face corrugated machine (1) according to claim 1, wherein the first corrugated roller (15) and the second corrugated roller (17) are mounted on an interchangeable roller cassette (13).

3. Single-face corrugator (1) according to claim 1, wherein the stretching rod (53) is actuated by a support (59) associated with the carrying frame (3).

4. Single face corrugator (1) according to claim 2, wherein the stretching rod (53) is actuated by a support (59) associated with the carrying frame (3).

5. The single-face corrugator (1) according to claim 3, wherein the stretching rod (53) is supported by a pair of pivoted levers (55) pivoted to the pivot structure, and the pivoted levers (55) can cooperate with the support (59) associated with the supporting frame (3) so that when the pivot structure is raised from the working position to the raised position, the pivoted levers (55) contact the support (59) and rotate relative to the supporting frame to stretch the continuous flexible member (31).

6. A single-face corrugated machine (1) according to claim 4, wherein the stretching rod (53) is supported by a pair of pivoted levers (55) pivoted to the pivot structure, and the pivoted levers (55) can cooperate with the support (59) associated with the supporting frame (3) so that when the pivot structure is raised from the working position to the raised position, the pivoted levers (55) contact the support (59) and rotate relative to the supporting frame to stretch the continuous flexible member (31).

7. The single face corrugator (1) according to claim 3, wherein the support (59) is elastic.

8. The single facer corrugator (1) according to any one of claims 1 to 7, wherein the pivot axis (29) is spaced apart from both the first rotation axis (33) of the first guide roller (32) and the second rotation axis (37) of the second guide roller (35).

9. The single-face corrugated machine (1) according to any one of claims 1 to 7, wherein the pivot structure comprises a first pivot arm (23) and a second pivot arm (25) rigidly connected to each other, at least one of the first pivot arm and the second pivot arm being pivotally connected to the supporting frame (3).

10. The single-face corrugated machine (1) according to any one of claims 1 to 7, wherein the pivot structure comprises a first pivot arm (23) and a second pivot arm (25) rigidly connected to each other, and the first pivot arm and the second pivot arm are both pivotally connected to the supporting frame (3).

11. The single facer corrugator (1) according to any one of claims 1 to 7, wherein the control system comprises a first actuator (41) and a second actuator (43) arranged on opposite sides of the single facer corrugator (1).

12. The single facer corrugator (1) according to claim 9, wherein the control system comprises a first actuator (41) associated with the first articulated arm (23) and a second actuator (43) associated with the second articulated arm (25).

13. A method for operating a single face corrugating machine (1) according to any one of the preceding claims, wherein the following steps are performed to replace the first corrugating roller (15) and the second corrugating roller (17): - lifting the articulated structure by moving the first guide roller (32) and the second guide roller (35) away from the first corrugating roller (15) and the second corrugating roller (17); - when the hinged structure is in the raised position, the continuous flexible member (31) is kept stretched by means of a stretching device (53); - removing the first corrugating roller (15) and the second corrugating roller (17) from the carrying frame (3); - inserting a new first corrugating roller (15) and a new second corrugating roller (17) into the supporting frame (3); and - Lowering the articulated structure and pressing the continuous flexible member (31) against the new second corrugating roller (17).

14. A single-face corrugated paperboard machine (1) for manufacturing single-face corrugated paperboard, comprising: a) load-bearing frame (3); b) a first corrugating roller (15) and a second corrugating roller (17), the first corrugating roller and the second corrugating roller being meshed with each other and associated with the supporting frame (3); c) a pressing unit (21) capable of pressing against said second corrugating roller (17) and comprising: - a first guide roller (32) which is pivotably supported about a first rotation axis (33); - a second guide roller (35) which is pivotably supported about a second rotation axis (37); - a continuous flexible member (31) which is guided around said first guide roller (32) and said second guide roller (35); wherein the first guide roller (32) and the second guide roller (35) are supported by a pivot structure, the pivot structure being pivotally connected to the supporting frame (3) about a pivot axis (29), the pivot axis being substantially parallel to the axes of the first corrugating roller (15) and the second corrugating roller (17); and wherein the pivot structure is associated with a control system (41, 43), the control system being capable of rotating the pivot structure into a working position and a raised position, wherein in the working position the continuous flexible member (31) is pressed against the second corrugating roller (17), and in the raised position the first guide roller (32) and the second guide roller (35) are spaced apart from the second corrugating roller (17); The invention is characterized in that the pivot axis (29) of the pivot structure is arranged at a distance from the rotation axis (33) of the first guide roller (32) and at a distance from the rotation axis (37) of the second guide roller (35).

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