EP0252572A1 - Drying cylinder for web materials in particular for paper, and his remote control - Google Patents

Abstract

The invention relates to a remote-controlled drying cylinder (1) for a web material machine, in particular for paper. The lateral surface of the cylinder (1) is subdivided into contiguous annular zones (2) which each surround an individually controlled heating device and comprising at least a heating element (8) and a regulation element (10) of the heating power dissipated, which are housed in the cylinder (1) and rotated with it around its axis. The regulating member (10) is remotely controlled from a common control box (20), external to the cylinder (1) and containing a heating control member (23) which is specific to each regulating member (10) for it. transmit a heating control signal.

Description

Technical area

The present invention relates to paper machines, and it relates more precisely to a drying cylinder intended for the equipment of a dryer and / or a post-dryer of a paper, cardboard or other material in bandaged.

Prior art

In paper machines, it is known that the paper web is already well formed when it leaves the press section, the main problem then remaining to be solved being to reduce the water content of the web, which is then between 60 and approximately 65%, at a much lower value, of the order of 5 to 10%. This is carried out in a dryer, in which the strip of wet paper leaving the last press, and still containing 60 to 65% of water, is brought into close contact with a number of large drying cylinders, the usual diameter is 1.5m, and which are heated internally with steam, the strip of wet paper being strongly pressed on the external face of these cylinders by means of felts. The drying cylinders or drums are arranged in two rows, an upper and a lower, and are generally grouped in batteries of three to twenty cylinders, each battery being associated with its felt, which develops downwards or upwards, and each felt being dried by a felt dryer drum or drum. The strip of paper passes successively from a lower drying cylinder to an upper drying cylinder, and vice versa. Blowers, suitably arranged, peel off the thin film of air saturated with vapor which tends to form continuously on the strip of wet paper and to stagnate there, and the vapors released are collected by a hood and evacuated. In these dryers with drying cylinders heated internally with steam, it is accepted that 1.3 to 1.5 kg of steam are necessary, depending on the installations and the nature of the paper pulp, to evaporate a liter of water contained in the strip. wet paper.

In more recent drying works, the felts were removed, and each drying cylinder was surrounded by an individual hood pierced with multiple orifices, in the form of holes and slots, in communication with a system for blowing hot air and extracting fumes.

These two types of dryer have the common disadvantage that their operation takes place according to a cycle having a high inertia and that the regulation of the operation of the heavy and complex mechanical and thermal assemblies which these dryers pose poses many problems. For this reason, a large number of devices have been designed and are used in order to control the quantities and the qualities of the vapor admitted into the drying cylinders at the various stages of the evaporation of the strip of paper in the dryer. In practice, the greatest difficulty to overcome consists in maintaining an equal degree of dryness over the entire width or width of the strip, or even in preserving a desired moisture profile. For this reason, modern paper machines include various devices which make it possible, by an additional supply of hot air, to dehydrate locally the parts of the strip which remain too wet, and, by spraying with water, to rewet the parts of the strip become too dry.

The various drawbacks presented above are also encountered in paper machines in which the cylinders of the dryer are partially or totally replaced by a huge single cylinder called a "frictionneur", the diameter of which can reach from 3 to 6 m, and which is surrounded by a high efficiency hood.

In some paper machines, drying is followed by a size press. In this case, the latter is itself followed by a post-dryer, which is in fact a second dryer, of smaller size than the main dryer, and it is understood that these paper machines also have, at the level of the whole of the dryer, the same drawbacks as the state facilities of the technique presented above.

After having passed over one or two cooling rolls, which are mounted at the outlet of the drying or post-drying, the strip of paper can be considered as being completely formed and then be wound up in mother reels. However, in the majority of cases, the paper strips undergo, before being wound up in master rolls, treatments intended to improve their surface condition and / or their internal structure. When these treatments are carried out on the paper machine itself, the strip of paper leaving the dry or post-dry is received in a heddle responsible for improving the surface condition, while the internal structure of the paper can be improved by moistening the strip of paper leaving the dryer with the help of wetting or moistening machines. A damper is a device that sprays water, in the form of as small droplets as possible, on the strip of paper leaving the dryer, in order to restore humidity of between 5 and 10% approximately. The arm is a vertical mechanical device comprising several carefully polished metal rollers, resting horizontally on each other and clamped together with an adjustable force, by means of a frame. The strip of paper coming out of the cooling rollers passes between the rollers of the heald, which are cooled or heated by external blowing of air through nozzles, in order to contract or locally expand the metal and to correct, where it is necessary, the defects that the paper strip may have in its thickness. In addition to the regularization of the thickness profile of the strip, the smoothing decreases, by simple compression, the natural roughness of the paper.

However, the treatment for improving the surface condition can also be carried out outside the paper machine, in a calender comprising several rollers alternately of polished metal and of compressed and rectified paper. Calenders, which are very heavy and which consume a lot of energy and generate a lot of waste, improve the surface regularity of the paper strip by the compression and the surface friction which they impose on the strip.

Statement of the invention

The object of the invention is to propose a drying cylinder which overcomes the drawbacks of the drying cylinders of the state of the art in terms of regulation, and such that a certain number of cylinders according to the invention can be substituted and / or added to certain known cylinders, downstream of a certain number of these cylinders, in order to correct the humidity profile in the dry or post-dry.

The main object of the invention is to propose a drying cylinder which allows better control of the moisture profile and the thickness profile of the strip of material, and which fulfills, at least partially, the functions usually performed by dampers and / or healds or calenders, so that the latter devices can be otherwise eliminated, at least simplified in their production, or that the overall result is improved and obtained more quickly.

To this end, the drying cylinder according to the invention, intended for the equipment of a dryer and / or a post-dryer of a strip material machine, in particular paper, and of the type having a hollow framework internally heated and having a cylindrical external lateral surface, of circular section, against which a strip of material is intended to be applied, is characterized in that the external lateral surface is delimited by several cylindrical rims, of circular section, of the same radius, arranged coaxially side by side, and made of a material which is a good conductor of heat, each rim being in heat exchange relation with an internal heating device with individual control which the rim surrounds, and each rim being integral in rotation with at at least one hub wedged on at least one cylinder rotation shaft. By thus regulating the heating of the different rims, independently one from the other, one can act selectively on the humidity profile. This advantage is reinforced if, according to an additional characteristic specific to the invention, each rim is also in heat exchange relation with an internal cooling device with individual control that the rim surrounds, because then, each rim can be successively heated and cooled, as required along the longitudinal section of width applied against the corresponding rim, in response to correction signals from suitable detectors, such as those currently used in paper machines.

Preferably, each rim is directly in contact, and integral in rotation, with an underlying member which it surrounds and which contains at least one heating member of the corresponding heating device and / or one cooling member of the cooling device. corresponding, so that the rim is heated and cooled by conduction, which is an efficient heating and cooling mode, with good efficiency, and flexible in terms of regulation.

In order to reinforce the independence of the different rims, each rim is separated from the neighboring rim (s) by a small axial space.

Preferably, the two axial ends of the cylinder are closed, in order to avoid, during rotation, the energy losses by ventilation.

In this case, it is advantageous that the interior of the cylinder is connected to a source of vacuum, so that the sheet of material is sucked against the rims, by the free axial spaces between the latter, which makes it possible to promote heat exchanges. between the cylinder and the strip of material.

When the rims are separated by an axial gap, it is also advantageous, in addition, to replace the doctor blades usually used to prevent the strip of material from rolling up on the cylinder, with at least a comb for separating the sheet of material from the cylinder, and the teeth of which are slid into the axial spaces between the rims.

Advantageously, the heating device is an electrical device, the heating member of which comprises an electrical resistance supplied with power from outside the cylinder, which can be achieved in a relatively simple, compact and inexpensive manner, with good energy efficiency. .

However, it is also possible for the heating device to be a device for circulation of a heat transfer fluid, the heating member of which comprises a tubular element through which a hot heat transfer fluid passes. Other heating means can also be envisaged, for example induction heating.

As for the cooling device of each rim, it is advantageously produced in the form of a device for circulation of a cooling fluid in a tubular cooling element, an inexpensive and practical cooling fluid for this purpose being for example cold water. The circulation of a fluid in a tubular element of a cooling device and / or a heating device can be controlled by an electrically controlled valve, while the electrical supply of the resistance of a heating device electric and / or the valve of a cooling device and / or a heating device can be controlled by a relay housed in the cylinder.

In these different cases, each relay is for example switched by an independent remote control. In a preferred embodiment, the remote control comprises a receiver specific to the corresponding relay and sensitive to a particular control frequency of a transmitter common to all the relays and to several transmission frequencies, in number corresponding to the number of relays, l the transmitter being itself controlled, for each frequency, by an interrup particular tor. In the latter embodiment, it is advantageous for the switching frequencies of the relays to pass through at least one power supply line to the resistor and / or to the corresponding valve.

However, the remote control is not limited, in its implementation, to frequency control of the various relays, and it is also possible that each relay is switched, for example, by an individual photoreceptor cell, which is attached to it, and which captures a particular light beam. In the case where the rims are separated by axial spaces, it is also possible that each relay is a relay with proximity microswitch actuated by a comb tooth introduced into an axial space between two rims, which makes it possible to make the most of the presence of a separation comb between the strip of material and the cylinder.

Brief description of the drawings

• - la figure 1 est une vue partielle en perspective d'un cylindre sécheur conforme à l'invention,
• - la figure 2 est une vue partielle schématique et en coupe axiale du cylindre sécheur de la figure 1, et
• - la figure 3 est un schéma illustrant le principe de la commande électronique du cylindre sécheur représenté sur les figures 1 et 2.

The present invention will be better understood using a particular embodiment, described below without limitation, with reference to the accompanying drawings in which:

• FIG. 1 is a partial perspective view of a drying cylinder according to the invention,
• FIG. 2 is a schematic partial view in axial section of the drying cylinder of FIG. 1, and
• FIG. 3 is a diagram illustrating the principle of the electronic control of the drying cylinder shown in FIGS. 1 and 2.

Best way to realize the invention

With reference to FIGS. 1 and 2, the drying cylinder 1 consists of several rims 2, cylindrical, of circular section and of the same radius, made of copper or stainless steel, each of which is integral with an underlying member 3, called underlying in the rest of this memo. Each sub-rim 3 has the shape of a circular ring of cross section substantially in an isosceles trapezoid with slightly curved inclined sides and surrounded by the corresponding rim 2 which the sub-rim supports. By its large base, facing outwards, each sub-rim 3, also made of copper or stainless steel, is integral with the internal face of the corresponding rim 2, while by its small base, facing inwards, the sub-rim rim 3 is connected by three rigid spokes 4 to the external lateral surface of a hub 5 having an axial passage by which the hub 5 is secured in rotation with a drive shaft 6, for example by keying or by splines.

The axial dimension of each hub 5 is slightly greater than that of the corresponding rim 2, so that all of the rims 2, the sub-rims 3, the spokes 4 and the hubs 5 abutted against each other, are assembled and wedged on the shaft 6, so that a free space 7 of about 1 mm wide separates two adjacent rims 2. The cylindrical and circular external lateral surface of the drying cylinder 1 is thus delimited by the polished external lateral surfaces of five to ten independent rims 2 per meter of width, the rims 2 being mounted coaxial, side by side, and separated two by two. by an axial space 7, the drying cylinder 1 having the same external dimensions as steam-heated drying cylinders of the state of the art, that is to say an external diameter of approximately 1.5 m and a length between 1.5 and 10 m.

Each independent rim 2 is associated with a heating device and a device for cooling this rim 2. Each heating device comprises an electric heating element in the form of an electrical resistance 8 housed in a toric channel embedded in the sub-rim 3 corresponding. This electrical resistance 8 which, by the Joule effect, ensures the heating of the sub-rim 3, and therefore by conduction the heating of the rim 2, is supplied with power by a supply line (not shown in Figures 1 and 2) extending radially along or in a radius 4, then passing through the corresponding hub 5 and the shaft 6, and then extending in the shaft 6, which is hollow, up to two rotating slip rings 9, carried by the shaft 6 on one of its two axial ends. Against these rings 9 are applied fixed brushes connected to the electrical current distribution network.

The supply of the heating resistor 8 is regulated by a control member in the form of a relay 10, which is mounted on the corresponding power supply line, remote-controlled from outside the cylinder 1 and arranged on a spoke. 4, near the corresponding hub 5.

Each cooling device, which is circulating with a cooling fluid, also comprises a cooling member and a control member. The cooling member is a toric channel 11, which is also embedded in the corresponding sub-rim 3, and which is traversed by a flow of water. This water, which enters cold in the channel 11, is heated, by conduction, by the sub-rim 3 and by the rim 2 which are thus cooled. The channel 11 is connected to a cold water supply pipe and to a heated water discharge pipe (not shown in FIGS. 1 and 2) which extend radially either within a radius 4 or along d 'a radius 4, then pass through the corresponding hub 5 and the shaft 6, and open into the latter respectively in a general cold water supply pipe and in a general pipe for evacuating the heated water, which are by example coaxial and extend to an axial end of the hollow shaft 6, where these two pipes are connected by rotating nozzles each to one of two pipes external to the cylinder 1 and intended for the arrival of water cold and at the outlet of the heated water.

The circulation of water in each channel 11 is regulated by a control member in the form of a solenoid valve 12, arranged on a radius 4, near the corresponding hub 5, the electrical control of which is provided by an integrated and remote-controlled relay in the same manner as relay 10.

Each rim 2 can thus be successively heated and cooled, independently of the others, by the individual control of the heating and cooling devices associated with it, as required and in accordance with control signals which are produced, for example by computer, as a function of detection signals coming from humidity or thickness detectors suitably arranged opposite the paper strip, as is the case in the paper machines of the state of the art. These control signals are transmitted to each relay controlling the supply of the corresponding heating resistor 8 or the corresponding solenoid valve 12 by an independent remote control.

In order to avoid any risk of warping of the different sub-assemblies, each of which comprises a rim 2, the sub-rim 3, the spokes 4 and the corresponding hub 5, the spokes 4 of the different sub-assemblies can be connected by threaded tie rods 13, which pass through the spokes 4 parallel to the axis of rotation of the shaft 6 and are rigidly fixed to each spoke 4 by two nuts 14 screwed onto the corresponding tie rod 13 and tightened on either side of the spoke 4 against the external lateral surface of the latter. The different spokes 4 thus connected by a tie rod 13 are kept apart at constant distances from each other.

FIG. 3 schematically shows an embodiment of an electronic remote control for heating and cooling a drying cylinder such as 1. Each rim 2 corresponds to two frequency-controlled static relays, which are each switched by a alternating control signal having a particular frequency. For each rim 2, the relay 10 associated with its particular receiver, sensitive to a first frequency particular, controls the supply of the heating resistor 8 connected in bypass on an internal and bipolar electrical line 15 of power supply of all the heating resistors 8 and of all the solenoid valves 12. This relay 10 is also mounted in bypass on the internal power supply line 15. Each solenoid valve 12, also connected in bypass on the internal line 15, is controlled by its integrated static relay 12ʹ, itself associated with its particular receiver, sensitive to a second particular frequency, and in bypass on the internal line 15. The two wires of the latter are each connected to one of the two rotating slip rings 9 of the shaft 6, against which a fixed brush 16 of an external and bipolar power supply line 17 is applied, bypassing on a line 18 for supplying power to the mains, for example alternating current at 220 V, by means of a protection switch 19 housed in a control box or console 20. The latter essentially contains a single transmitter 21 of alternating signals which is connected as a branch on the line of sector 18, by means of a second protection switch 22. This transmitter 21 can transmit signals at particular frequencies whose number cor corresponds to the sum of the number of heating resistors 8 and the number of solenoid valves 12, and this transmitter 21 is controlled by switches 23 in number equal to the number of the particular emission frequencies. The transmitter 21 is also connected to the external power supply line 17, downstream of the protection switch 19, so that each signal, transmitted at a particular frequency, passes through the power supply lines 17 and 15 to reach relay 10 or relay 12ʹ which is sensitive to this particular frequency.

Thus, heating or stopping the heating of each rim 2 by supplying or interrupting the supply of the corresponding electrical resistance 8, as well as the cooling or stopping of the cooling of this rim 2 by the opening or closing of the corresponding solenoid valve 12 are controlled by the emission or the interruption of the emission by the transmitter 21 of a signal having a particular frequency and which is received by a relay 10 or by a relay 12ʹ switched by this signal. Preferably, the switches 23, which each control the emission of a signal at a particular frequency, are actuated automatically in any suitable known manner, in order to obtain automatic regulation of the heating and / or cooling of the rims 2, independently one from the other.

The internal equipment of such a cylinder 1 with the various relays 10 and 12ʹ and the various corresponding electrical connections, as well as with the various solenoid valves 12 and the various corresponding water pipes, does not pose any major problem, given the large internal volume available and the repetitive nature of the assemblies, all of the components of which remain easily accessible when the cylinder is stopped for maintenance work.

To avoid loss of energy by ventilation, the cylinder 1 is closed in a relatively airtight manner at its two axial ends, as is schematically represented on the right axial end of the cylinder 1 in FIG. 3 This can be achieved using two radial discs such as 24, one of which delimits around the part of the shaft 6 which passes through it a suction opening connected by an external bell 25 to a source of vacuum. , so that the slight depression prevailing in the rotating cylinder 1 causes a suction at the axial spaces 7 between the rims 2. Thus the strip of material, for example of paper, is sucked and well applied against the external lateral surface of the rims 2, which promotes heat exchange between the rims 2 and the paper, which can thus correct the profile humidity. Indeed, a supply of moisture to an excessively dry area of the paper is obtained due to the condensation which results from the cooling of the rim (s) 2 against which this area of paper is applied, while evaporation at the levels heated rims 2 dehydrate excessively damp and corresponding areas of the paper.

In addition, such a drying cylinder 1 participates in the correction of the paper thickness profile, because it is placed upstream of a heddle for example, to which the strip of paper, locally heated or cooled in adjacent longitudinal zones and transverse, will bring more or less heat.

In order to prevent the strip of paper from wrapping around the cylinder 1, a comb 26 is used, the teeth 27 of which, in the shape of a knife blade, are each engaged and slides in an axial space 7 between two adjacent rims 2, as schematically shown in Figure 1.

The invention is not limited to the preferred embodiment which has been described with reference to Figures 1 to 3, but it can be subject to variants. For example, the heating device can also be a device for circulation of a hot heat-transfer fluid, the flow of which in a channel such as that which is traversed by the coolant, is controlled by another solenoid valve with electric control by a relay.

The different relays of the heating and cooling devices can be controlled by a remote control different from that described above. For example, each relay can be controlled by a particular photo-receiving cell, which picks up a particular light beam, or alternatively each relay is a relay with proximity microswitch, actuated by the tooth 27 of the comb 26 which is engaged. in an axial space 7 adjacent to the corresponding rim 2. The relays can also be switched by radio waves, without transit through the power line. The strip of material can be applied against the rims by a felt by atmospheric pressure if the cylinder is in depression, or by the tension of winding of the strip around the cylinder.

Claims (15)

1.Drying cylinder, for the treatment of a strip material, in particular paper, the cylinder (1) having a hollow framework heated internally by a heating installation which comprises a plurality of internal heating devices (8,10) to individual control, axially spaced from each other, and each comprising at least one heating member (8) driven in rotation with the hollow framework, which is mounted in rotation about the axis of the cylinder and has a substantially cylindrical external lateral surface , of circular section, against which a strip of material is intended to be applied, and which is subdivided into annular zones (2) contiguous axially, each of which is in radial correspondence and in heat exchange relation with one of the devices internal heating (8,10) as said external corresponding annular zone,
characterized in that each heating device further comprises a member (10) for regulating the heating power dissipated by the heating member (s) (8) of said device, said regulating member (10) being mounted in the hollow framework , integral in rotation with the latter, and remote-controlled from a control box (20) common to all the regulating members (10), external to the cylinder (1) and containing, for each regulating member (10), a control member (23) of its own heating to transmit a heating control signal to it. 2.Drying cylinder according to claim 1, characterized in that it further comprises a cooling installation comprising a plurality of individually controlled internal cooling devices (11, 12, 12ʹ), axially spaced from each other, and each comprising at least one cooling member (11) driven in rotation with the hollow framework, and in radial correspondence and in heat exchange relation with one of said annular zones (2) which surrounds it, each cooling device further comprising a member (12, 12ʹ) for regulating the cooling power dissipated by the cooling member (s) (11) of said device, said regulating member (12, 12ʹ) being mounted in the hollow framework, integral in rotation with the latter, and remotely controlled from said control box (20) which also contains, for each regulating member ( 12, 12ʹ) of the cooling, a cooling control member (23) which is specific to it for transmitting a cooling control signal to it. 3.Cylinder dryer according to one of claims 1 and 2, characterized in that said remote control ensures the transmission of control signals without contact between the cylinder (1) and the control box (20). 4.Drying cylinder according to claim 3, characterized in that said remote control ensures the transmission of control signals optically, each regulating member (10, 12-12ʹ) of the heating or cooling power being controlled by a cell photoelectric capturing a particular light beam. 5. Drying cylinder according to claim 3, characterized in that said remote control ensures transmission of control signals by radio, said control box (20) comprising a single signal transmitter (21) and each regulating member (10, 12-12ʹ) being controlled by an associated own receiver, receiving specific radio signals broadcast by the single transmitter (21). 6.Drying cylinder according to one of claims 1 and 2, characterized in that said remote control ensures the transmission of control signals from the cabinet (20) to the regulating members (10; 12-12ʹ) by at least one electrically conductive line and an arrangement with at least one rotating slip ring (9) cooperating with at least one fixed friction brush (16). 7. drying cylinder according to claim 6, characterized in that said control members (23) for heating and / or cooling are mounted in parallel in said box (20) and transmit their control signals to the cylinder (1) by a single line at least bipolar on which all the regulating members (10, 12-12ʹ) are mounted in bypass. 8.Drying cylinder according to one of claims 1 to 7, characterized in that the regulating members (10, 12-12ʹ) are organs consuming electrical energy, such as relays (10, 12ʹ) and solenoid valves (12), which are bypassed on a part (15) internal to the cylinder (1) and rotating with it a power supply line (15,17). 9.Drying cylinder according to one of claims 1 to 8, characterized in that each heating device (8, 10) is an electrical device of which each heating member is a gold electric heating gane (8) such as a resistor, supplied with power from a heating current source outside the cylinder (1) by an electric supply line (15,17) having an internal part (15) to the cylinder (1) and rotating with it, and on which all the heating devices are mounted in bypass. 10. Drying cylinder according to one of claims 1 to 8, characterized in that each heating device is a device for circulation of a heat transfer fluid, the heating element or elements of which comprise a tubular element in which the circulation of the heat transfer fluid is controlled by at least one solenoid valve, mounted as a bypass on a part (15) internal to the cylinder (1), and rotating with it, of an electrical supply line (15,17). 11.Drying cylinder according to one of claims 3 to 10 as attached to claim 2, characterized in that each cooling device is a device for circulating a cooling fluid, the cooling member or members of which comprise an element tubular in which the circulation of the coolant is controlled by at least one solenoid valve (12) mounted as a bypass on said part (15) of the power supply line (15,17) which is internal to the cylinder (1) and rotates with him. 12.Cylinder dryer according to one of claims 9 to 11 characterized in that the regulating members controlling the electrical supply of the heating members (8) and / or the actuation of the solenoid valves (12) are relays (10, 12ʹ ) each switched by an independent remote control and mounted in derivation on said part (15) of the power supply line (15,17) which is internal to the cylinder (1). 13.Drying cylinder according to claim 12, characterized in that said independent remote control comprises a receiver specific to the relay (10,12ʹ) corresponding and sensitive to an alternating signal having a particular frequency and emitted by a transmitter (21) common to all relays (10,12ʹ) and with several transmission frequencies, in number at least equal to the number of relays (10,12ʹ), the transmitter (21) being controlled for each frequency by a particular control member arranged as a switch ( 23). 14.Drying cylinder according to claim 13, characterized in that the alternating signals at the different specific switching frequencies of the relays (10,12ʹ) pass through said power supply line to power the electric heating elements (8) and / or solenoid valves (12) for heating and / or cooling devices. 15.Drying cylinder according to one of claims 1 to 14, characterized in that the heating element (s) of each heating device and / or the cooling element (s) of each cooling device is or are one or more elements substantially annulars embedded in the corresponding annular zone (2) of the external lateral surface of the cylinder (1).

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