MACHINE FOR MANUFACTURING PAPER OF THE TISSUE TYPE

Abstract

 A machine for manufacturing paper of the tissue type with a paper drying region (7) which comprises a Yankee drying cylinder (8), on which the paper being processed passes. According to the invention, the Yankee cylinder (8) comprises a substantially cylindrical side wall (11), which can rotate about the axis of a shaft (12) which passes axially through the Yankee cylinder (8). The shaft (12) supports, within the side wall (11), at least one air-stream burner device (18) which comprises a burner body (19) which has a longitudinal extension that is substantially parallel to the axis of the shaft (12) and is provided, on its side directed toward the internal surface of the side wall (11), with a plurality of openings (20) for the outflow of the combustible gas and of the oxidizing air, in order to generate a plurality of flames (21) in heat exchange relationship with the internal surface of the side wall (11). The burner device (18) is provided with an assembly (25) for igniting the flames (21) and with means (26) for detecting the presence of flames (21). Multiple passage openings (28) are formed in the shaft (12) and communicate with a discharge channel (29) which is extended axially along at least one portion of the shaft (12), for the outflow of the combustion gases from the Yankee cylinder (8).

Description

[0001] The present invention relates to a machine for manufacturing paper of the tissue type.

[0002] As is known, machines for manufacturing paper are currently divided in two types: machines that allow to manufacture ordinary printing paper, writing paper, paperboard and so forth, and machines for manufacturing tissue paper, i.e., the paper used for hygienic or domestic use, such as for example toilet paper, paper towels and so forth.

[0003] Machines of the first type are known as multi-cylinder, since they require the presence of a plurality of cylinders to dry the paper being formed, the number of which can vary as a function of various parameters, such as the thickness of the paper and the speed of the machine.

[0004] Ordinary multi-cylinder machines typically have, in mutual succession, a sheet forming region, a region for mechanical pressing of the sheet, and a sheet drying region, in which the paper is dried, passing it around a plurality of cylinders, which are heated on their lateral surface, by means of steam that is fed inside them, so as to obtain the evaporation of the water contained in the paper.

[0005] Machines for manufacturing tissue paper, more simply commonly known as tissue machines, are instead characterized by the presence of a single paper drying cylinder, which in the common technical jargon of the industry is known as Yankee drying cylinder or drum.

[0006] More particularly, generally speaking, tissue machines have, arranged in mutual succession along an advancement path of the paper being processed, a paper forming region, a transferring region by means of a felt moving belt, a pressing region, a drying region, with a single Yankee cylinder, and a region for winding the finished paper into a roll.

[0007] In detail, in the forming region, a head box, supplied with paper pulp, deposits a wet paper sheet on the felt moving belt, which conveys the paper being processed to a pressing region, in which a pressing roller presses the wet sheet against the Yankee cylinder, which, like the cylinders of multi-cylinder machines, is fed internally with pressurized steam, in order to obtain the heating of its side wall, on which the paper sheet is rested to be dried.

[0008] Above the Yankee cylinder there is a drying hood which, by means of hot air, dries the side of the paper sheet that is opposite the side in contact with the side wall of the Yankee cylinder.

[0009] According to the background art, the steam that is sprayed axially under pressure inside the Yankee cylinder becomes distributed radially, transferring heat to the side wall of the Yankee cylinder, with formation, on the internal surface of said side wall, of condensation, which is aspirated by means of central pipes which convey it outside the Yankee cylinder.

[0010] The internal surface of the side wall of the Yankee cylinder is typically grooved in order to obtain a larger surface for heat exchange between steam and side wall of the Yankee cylinder.

[0011] Currently, a boiler, thermocompressors and a complex steam distribution system are traditionally used in order to produce the steam that is fed to the Yankee cylinder.

[0012] One drawback of current tissue machines is that the steam distribution system, besides being expensive, entails frequent losses of load and steam, with consequent dispersion of a significant quantity of useful energy.

[0013] Another drawback of tissue machines arises from the constructive complexity of traditional Yankee cylinders.

[0014] In fact, the machining of the Yankee cylinder in order to provide the grooves on its internal surface and its internal components for removing the condensation are quite complex and onerous to provide.

[0015] Another problem of current tissue machines is constituted by the deformation to which the Yankee cylinder is subjected. In fact, since the pressure inside the Yankee cylinder is much higher than the external pressure and since said cylinder is usually made of steel, it tends to deform, forming a bulge in the central part of its longitudinal extension.

[0016] This forces the provision of complex grinding processes on the external surface of the side wall of the Yankee cylinder, in order to compensate the deformation to which is subjected, so as to have a constant contact profile between the Yankee cylinder and the presser cylinder and, consequently, uniform drying on all of the transverse extension of the paper sheet.

[0017] The aim of the present invention is to provide a machine for manufacturing paper of the tissue type that is capable of improving the background art in one or more of the aspects mentioned above.

[0018] Within this aim, an object of the invention is to provide a machine for manufacturing paper of the tissue type that allows to avoid expensive losses of the energy produced to heat the Yankee cylinder.

[0019] Another object of the invention is to devise a machine for manufacturing paper of the tissue type that allows to heat the Yankee cylinder without pressure excesses inside it, thus avoiding deformations of the Yankee cylinder and the consequent need to resort to expensive operations for grinding its external surface.

[0020] Another object of the present invention is to devise a machine for manufacturing paper of the tissue type that allows to easily provide increases in production without excessive loads on its components.

[0021] Another object of the present invention is to provide a machine for manufacturing paper of the tissue type that, by virtue of its particular constructive characteristics, is capable of giving the greatest assurances of reliability and safety in use.

[0022] Another object of the present invention is to provide a machine for manufacturing paper of the tissue type that is easy to maintain.

[0023] A further object of the present invention is to overcome the drawbacks of the background art in a manner that is alternative to any existing solutions.

[0024] Another object of the invention is to provide a machine for manufacturing paper of the tissue type that can be constructively simple and can be provided by means of commonly commercially available elements so as to be competitive also from a purely economic standpoint.

[0025] This aim and these and other objects which will become better apparent hereinafter are achieved by a machine for manufacturing paper of the tissue type according to claim 1, optionally provided with one or more of the characteristics of the dependent claims.

[0026] Further characteristics and advantages of the invention will become better apparent from the description of some preferred but not exclusive embodiments of the machine according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

Figure 1 is a schematic view of the machine according to the invention;

Figure 2 is a schematic and longitudinal sectional view of the Yankee cylinder of the machine according to the invention;

Figure 3 is a schematic transverse sectional view of the Yankee cylinder of the machine according to the invention;

Figure 4 is a schematic transverse sectional view of a constructive variation of the Yankee cylinder of the machine according to the invention.

[0027] With reference to the figures, the machine for manufacturing paper of the tissue type, according to the invention, generally designated by the reference numeral 1, comprises, in mutual succession, along an advancement path of the paper being processed, a paper forming region 2, in which for example a head box, not shown and per se known, operates, a paper pressing region 3, connected to the forming region 2 by means of a felt moving belt 4, on which a wet paper layer is placed at the forming region 2, and a paper drying region 7, which comprises a rotating Yankee drying cylinder 8.

[0028] In particular, in the pressing region 3, a presser roller 3a, also per se known, presses the wet paper layer that arrives from the felt moving belt 4 against the Yankee cylinder 8, to which the wet paper layer adheres so as to be dragged, by the same Yankee cylinder 8, below a drying hood 9, which is above the Yankee cylinder 8 and emits hot air designed to dry the side of the paper layer that is opposite the one that adheres to the Yankee cylinder 8.

[0029] Also as per se known, downstream of the drying hood 9, along the rotational direction of the Yankee cylinder 8, the paper, which is by now dry, is removed from the Yankee cylinder 8, for example by means of a separator blade, and conveyed toward a winding region 10, in which a winding roller forms a finished paper roll.

[0030] As shown particularly by Figure 2, the Yankee cylinder 8 is internally hollow and, according to the invention, comprises a substantially cylindrical side wall 11 which can rotate about the axis of a shaft 12 which passes axially through the Yankee cylinder 8.

[0031] Preferably, the shaft 12 is fixed with respect to the framework of the machine and the side wall 11 of the Yankee cylinder 8 is rotatably mounted on the shaft 12 by means of a pair of closing end walls 13a and 13b of the Yankee cylinder 8, which are integral with the side wall 11 and are connected to the shaft 12 by means of the interposition of bearings 14a and 14b.

[0032] Conveniently, the rotational actuation of the side wall 11 of the Yankee cylinder 8 can be provided by a motor 15, which by means of a transmission assembly 16, constituted for example by a pair of pulleys 16a and 16b and by a transmission belt 16c, actuates rotationally a movement sleeve 17, mounted rotatably about the shaft 12 and connected rigidly to one of the closing end walls of the Yankee cylinder 8, for example the one designated by the numeral 13a, as in Figure 2.

[0033] As an alternative, the transmission assembly 16 can be constituted also by a hollow shaft reduction unit axially connected to the Yankee cylinder 8. In particular, the reduction unit may be keyed, with its own hollow shaft, on the movement sleeve 17 and may be connected at its input shaft to the output shaft of the motor 15, for example by means of a double cardan transmission shaft arranged substantially parallel and spaced with respect to the shaft 12.

[0034] Also according to the invention, the shaft 12 supports, within the side wall 11, at least one air-stream burner device 18 which is arranged proximate to the internal surface of the side wall 11.

[0035] Optionally, as shown in Figure 4, it is also possible to provide at least two air-stream burner devices 18, which are supported by the shaft 12 and are angularly mutually spaced around the axis of said shaft.

[0036] Each burner device 18 has a burner body 19 which has a longitudinal extension that is substantially parallel to the axis of the shaft 12 and is provided, on its side directed toward the internal surface of the side wall 11, with a plurality of openings 20 for the outflow of the combustible gas and of the oxidizing air, from which multiple flames 21 extend in heat exchange relationship with the internal surface of the side wall 11.

[0037] At least one pair of perforated confinement walls 22 is connected to each burner body 19, and said walls delimit laterally a combustion chamber 23, open toward the side wall 11, in which the flames 21 are laterally confined.

[0038] More particularly, the confinement walls 22 are arranged mutually opposite with respect to the outflow openings 20 and are extended substantially parallel to the longitudinal extension of the burner body 19.

[0039] Conveniently, the confinement walls 22 can be mutually joined, at the opposite longitudinal ends, by two transverse delimitation walls 24a and 24b of the combustion chamber 23.

[0040] Advantageously, the confinement walls 22 are inclined with respect to a plane that is radial to the shaft 12 and passes through the outflow openings 20, and mutually converge in the direction of the burner body 18.

[0041] Each burner device 18 is provided with an assembly 25 for igniting the flames 21, for example constituted by a pair of electrodes adapted to produce an ignition spark or by a pilot flame burner, and with sensor means 26 for detecting the presence of the flames 21 inside said combustion chamber 23, which can, for example, comprise at least one thermocouple.

[0042] Advantageously, the sensor means 26 are functionally connected, by means of a cable or wirelessly, to a control device 27, which is functionally connected to a control actuator of a valve 28 for controlling the flow of the combustible gas fed in input to each burner device 18 or to the respective burner device 18, in order to allow the automatic interruption of the supply of combustible gas at least to the corresponding burner device 18, upon detection of the absence of the flame 21 by the sensor means 26.

[0043] Multiple passage openings 28 are formed in the shaft 12 and communicate with a discharge channel 29 which is extended axially along at least one portion of the shaft 12, for the outflow of the combustion gases from the Yankee cylinder 8.

[0044] Advantageously, each burner device 18 is supplied by a combustible gas supply duct 30, which communicates with a pressurized combustible gas source, not shown. In particular, the supply duct 30, with at least one first portion 30a thereof, passes axially through at least one portion of the shaft 12 and connects appropriately to each burner 18 with at least one second portion 30b thereof that extends radially with respect to the shaft 12.

[0045] Advantageously, the flow control valve 27 can be interposed along the first portion 30a of the combustible gas supply duct 30, as in the example shown in Figure 2.

[0046] Each burner device 18, moreover, is supplied by an oxidizing air supply channel 31, which is formed substantially coaxially to at least one portion of the combustible gas supply duct 30 and, more particularly, to its first portion 30a, and communicates appropriately with the burner body 19 of each burner device 18 through air intakes 31a defined on the side of the shaft 12 directed toward each burner device 18.

[0047] Conveniently, as shown in Figure 2, the oxidizing air supply channel 31 affects a first portion of the shaft 12 which passes through an axial end of the Yankee cylinder 8, while the discharge channel 29 affects a second portion of the shaft 12 which, in turn, passes through the opposite axial end of the Yankee cylinder 8. Advantageously, the supply channel 31 is separated from the discharge channel 29, inside the shaft 12, by a partition wall 32 that is appropriately arranged in a substantially intermediate region of the extension of the shaft 12 inside the Yankee cylinder 8 and extends transversely to the axis of the shaft 12.

[0048] It should be noted that the central part 12a of the shaft 12, i.e., its portion arranged inside the Yankee cylinder 8, can be advantageously constituted by a hollow profiled element and appropriately have in a transverse cross-section a substantially polygonal shape and a larger diametrical bulk with respect to the end parts 12b of said shaft that pass through the axial ends of the Yankee cylinder 8.

[0049] Advantageously, there are means 33 for adjusting the thermal power delivered by the or each burner device 18, which comprise appropriately actuation means that allow to vary the degree of opening of the flow control valve 28 and can be constituted by an adapted actuation device 34 of the flow control valve 28 or, as an alternative, also by the control device 27.

[0050] More particularly, these adjustment means are functionally connected to a controller 35 which is capable of receiving the signals that arrive from means 36 for detecting the rotation rate of the side wall 11 of the Yankee cylinder 8 about the axis of the shaft 12, constituted by angular rate transducers, such as for example an encoder or other suitable devices, connected appropriately to the output shaft of the motor 15, and has the function of actuating the adjustment means 33 in order to vary the thermal power delivered by the or each burner device 18 as a function of the signal that arrives from the detection means 36.

[0051] In this manner, in the event of a request to increase the production of the machine, with consequent increase of the rotation rate of the Yankee cylinder, the adjustment means 33 automatically increase the power delivered by the or each burner device 18.

[0052] Advantageously, the machine according to the invention is provided, moreover, with safety means adapted to maintain inside the Yankee cylinder 8 a pressure that is lower than the external environmental pressure, so as to avoid leaks of combustible gas or combustion gases from the inside of the Yankee cylinder 8 outward.

[0053] Conveniently, said safety means are provided by means of a first fan 37, which is adapted to blow oxidizing air into the supply channel 31, and by means of a second fan 38, which has instead the function of aspirating the combustion gases from the discharge channel 29.

[0054] A control unit 39 is functionally connected to the first fan 37 and to the second fan 38 and supervises the operation of the first and the second fans 37, 38, so as to keep the flow-rate generated by the second fan 38 at a higher value than the flow-rate generated by the first fan 37, so as to ensure that the inside of the Yankee cylinder 8 is kept at a lower pressure than the outside environment.

[0055] Conveniently, the discharge channel 29 is connected to the drying hood 9, for example by means of a connecting duct 40 which is connected to the delivery of the second fan 38, so as to be able to recover, at least partially, the residual heat in the combustion gases that exit from the Yankee cylinder 8 in order to heat, for example by means of adapted exchangers, the air used by the drying hood 9 to dry the paper that passes over the external lateral surface of the Yankee cylinder 8, with the obvious advantage of using part of the energy produced by the burner devices 18, which otherwise will be lost, to supply the drying hood 9, thus reducing its energy consumption.

[0056] The operation of the machine, according to the invention, is as follows.

[0057] The first fan 37 pushes the oxidizing air into the supply duct 31, while, as a consequence of the opening of the flow control valve 28, the combustible gas travels along the supply duct 30, so that the air and the combustible gas can exit from the outflow openings 20 of the burner body 19 of each burner device 18.

[0058] The activation of the ignition assembly 25 allows to ignite at all the outflow openings 20 the flames 21, which, by making contact with the internal surface of the side wall 11 of the Yankee cylinder, transfer to said side wall the heat necessary to heat it.

[0059] The second fan 38 aspirates from the discharge channel 29, with a flow-rate that is greater and, more preferably, twice that of the first fan 37, the combustion gases produced by the flames 21, which, after being distributed inside the Yankee cylinder, enter the discharge channel 29 through the passage openings 28 formed in the shaft 12.

[0060] The second fan 38, moreover, sends the combustion gases drawn from the discharge channel toward the drying hood 9, through the connecting duct 40.

[0061] By virtue of the activation of the motor 15, the side wall 11 of the Yankee cylinder 8 may be rotated with respect to the shaft 12 and therefore also with respect to each burner device 18.

[0062] With the Yankee cylinder 8 thus activated, a wet paper layer is deposited on the felt moving belt 4 in the forming region 2 and is pressed against the Yankee cylinder 8 by the presser roller 3a at the pressing region 3.

[0063] The wet paper then reaches the drying region 7, in which the Yankee cylinder 8, cooperating with the drying hood 9, eliminates the water contained in the paper being processed before the latter is detached from the Yankee cylinder 8 and collected in a roll in the winding region 10.

[0064] If the flames 21 of one of the burner devices 18 are extinguished accidentally, the sensor means 26 detect the absence of flames 21 and the control device 27 automatically closes the flow control valve 28.

[0065] If an increase in production is required, an increase in the rotation rate of the output shaft of the motor 15 is commanded so as to increase the rotation rate of the side wall 11 of the Yankee cylinder 8 about the shaft 12. The increase in the rotation rate of the side wall 11 is reported by the detection means 36 to the controller 35, which commands, by means of the actuation device 34, an increase in the degree of opening of the flow control valve 27, so as to obtain an automatic increase in the thermal power delivered by each burner device 18.

[0066] Obviously, in the event of a request to decrease production, with consequent reduction of the rotation rate of the Yankee cylinder 8, the controller 35, as a consequence of the variation of the signal that arrives from the detection means 36, commands a reduction of the degree of opening of the flow control valve 27 with corresponding reduction of the thermal power delivered by each burner device 18.

[0067] In practice it has been found that the invention achieves the intended aim and objects, providing a machine for manufacturing tissue paper capable of solving the drawbacks of the background art.

[0068] In particular, it is noted that the machine according to the invention allows to avoid energy losses since the heat for heating the Yankee cylinder is produced directly inside said cylinder.

[0069] Another advantage of the invention is that it allows to avoid the occurrence, in the Yankee cylinder, of an excess in pressure that causes its bulging, with the consequent need to provide expensive grinding operations that complicate the construction of the Yankee cylinder itself.

[0070] The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims; all the details may furthermore be replaced with other technically equivalent elements.

[0071] In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to the requirements and the state of the art.

[0072] The disclosures in Italian Patent Application No. 102018000010597 from which this application claims priority are incorporated herein by reference.

[0073] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A machine for manufacturing paper of the tissue type comprising, in mutual succession, along an advancement path of the paper being processed, a forming region (2), a pressing region (3) and a drying region (7) for the paper, said drying region (7) comprising a rotating and internally hollow Yankee drying cylinder (8), on which the paper being processed passes to dry, characterized in that said Yankee cylinder (8) comprises a substantially cylindrical side wall (11), which can rotate about the axis of a shaft (12) which passes axially through said Yankee cylinder (8), said shaft (12) supporting, within said side wall (11), at least one air-stream burner device (18) which is arranged proximate to the internal surface of said side wall (11) and comprises a burner body (19) which has a longitudinal extension that is substantially parallel to the axis of said shaft (12) and is provided, on its side directed toward the internal surface of said side wall (11), with a plurality of openings (20) for the outflow of the combustible gas and of the oxidizing air, in order to generate a plurality of flames in heat exchange relationship with the internal surface of said side wall (11) and laterally confined within a combustion chamber (23), which is open toward said side wall (11) and is delimited by at least one pair of perforated confinement walls (22), which are connected to said burner body (19), said confinement walls (22) being arranged mutually opposite with respect to said outflow openings (20) and being extended substantially parallel to the longitudinal extension of said burner body (19), said at least one burner device being provided with an assembly (25) for igniting the flames (21) and with sensor means (26) for detecting the presence of flames (21) within said combustion chamber (23), multiple passage openings (28) being formed in said shaft (12) and communicating with a discharge channel (29) which is extended axially along at least one portion of said shaft (12), for the outflow of the combustion gases from said Yankee cylinder (8).

2. The machine according to claim 1, characterized in that said at least one burner device (18) is supplied by a combustible gas supply duct (30), which passes axially through at least one portion of said shaft (12), and by an oxidizing air supply channel (31), which is formed substantially coaxially to at least one portion of said combustible gas supply duct (31).

3. The machine according to one or more of the preceding claims, characterized in that said confinement walls (22) are inclined with respect to a plane that is radial to said shaft (12) and passes through said outflow openings (20), and mutually converge in the direction of said burner body (19).

4. The machine according to one or more of the preceding claims, characterized in that it comprises means (33) for adjusting the thermal power delivered by said at least one burner device (18), said adjustment means (33) being functionally connected to a controller (35), which is connected to means (36) for detecting the rotation rate of said side wall (11) about the axis of said shaft (12) and is adapted to actuate said adjustment means (33), in order to vary the thermal power delivered by said at least one burner device (18) as a function of the signal that arrives from said detection means (36).

5. The machine according to one or more of the preceding claims, characterized in that it comprises at least two air-stream burner devices (18) which are supported by said shaft (12) and are angularly mutually spaced around the axis of said shaft (12).

6. The machine according to one or more of the preceding claims, characterized in that said oxidizing air supply channel (31) affects a first portion of said shaft (12) which passes through an axial end of said Yankee cylinder (8), said discharge channel (29) affecting a second portion of said shaft (12) which passes through the opposite axial end of said Yankee cylinder (8).

7. The machine according to one or more of the preceding claims, characterized in that it comprises safety means adapted to maintain inside said Yankee cylinder (8) a pressure that is lower than the pressure of the outside environment.

8. The machine according to one or more of the preceding claims, characterized in that said safety means comprise a first fan (37) which is adapted to blow oxidizing air into said supply channel (31) and a second fan (38) which is adapted to aspirate the combustion gases from said discharge channel (29), a control unit (39) being provided which is functionally connected to said first fan (37) and to said second fan (38) and is adapted to keep the flow-rate generated by said second fan (38) at a higher value than the flow-rate generated by said first fan (37).

9. The machine according to one or more of the preceding claims, characterized in that said discharge channel (29) is connected to a drying hood (9) which is above said Yankee cylinder (8).

Drawing