FI88419C - Bk roller with heated jacket - Google Patents

Description

8841 9

Heat-coated tk roll Bk-Vals med uppvärmd mantel

The invention relates to a jacket-heated tk roll comprising a roll shaft and a roll shell rotatably mounted thereon, a series of hydraulically or correspondingly loaded piston-cylinder assemblies having a sliding shoe or shoes having a sliding shoe or shoes arranged between the roll shaft and the inner surface of the roll shell. with the inner surface of the roll shell and with sliding shoes for compensating or adjusting the distribution of the deflection of the roll shell in the axial direction, and for heating the tk roll shell with an electromagnetic induction heating arrangement based on the resistive heating effect of eddy currents in the roll shell.

Rollers that can be adjusted for the deflection and temperature of their casing are needed and used in paper machines and finishing machines, e.g. calendars. For example, a heated, so-called a "hot roll" that is desired to be used to get hot. At the same time, the temperature profile of the roll shell should often be adjustable, usually as uniform as possible, since the temperature of the roll shell has a significant effect on the calendering result.

In the following, when we talk about tk rolls, we mean both adjustable and only compensated rollers from the deflection of the jacket.

'Several different solutions are already known for heating and controlling the heat of the TK rolls. For example, U.S. Patent 4,679,286 discloses a pre-fabricated tk roll which is also heated to obtain the desired roll shell temperature. The heating system of this U.S. patent does not provide a uniform temperature profile for the roll shell, but the profile inevitably becomes skewed so that the temperature at one end of the roll is higher than at the opposite end.

U.S. Pat. No. 4,282,639 discloses another arrangement for heating a deflection-compensated roll, which roll is heated by spraying heated oil from nozzles against the inner surface of the roll shell. However, the solution of this U.S. patent does not take into account that spraying heated oil onto the surface of the roll shell does not keep the temperature profile of the outer surface of the roll shell constant because heat is dissipated from the roll shell by a web passing over the roll. Thus, in the end regions of the roll shell, from which no heat is dissipated in a corresponding manner, the temperature is considerably higher than that of the shell shell.

An additional disadvantage of oil-heated rollers is that if you want to get oil inside the roll at about 200 ° C, you have to feed oil, for example, at about 2000 1 / min. at a temperature of T - 220 ° C. In some cases, the tk roll must be made even hotter than described above, but known oils generally cannot withstand the higher temperature mentioned above.

It is already known, for example, from EP application 159,337 and U.S. patent 4,823,688 for electrically induction heated rolls, the heating devices of which are arranged outside the roll shell. With these known devices, the temperature level and temperature profile of the roll jacket can be adjusted axially, e.g. by using several parallel induction coil-magnetic shoe combinations to which the frequency and / or current of the supplied electricity is controlled and / or whose magnetic shoe air gap is adjusted to the outer surface of the roll. These known devices use quite high frequencies, usually above 20 kHz, in order to concentrate the heating effect on the outer surface layer of the roll shell.

An internally inductively heated so-called A “Tokuden” roll having a coil inside the roll shell between the shaft and the shell, but this known roll is not implemented as a tk roll.

Internally heated rollers with a live fire inside are also known. The use and adjustment of such a roller is cumbersome.

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It is an object of the present invention to provide new solutions to the problems discussed above.

It is a further object of the invention to provide a heated tk roll in which the heating efficiency is high.

It is a further object of the invention to provide a tk roll into which the maximum temperature and amount of heating oil to be fed, if it is generally necessary, can be further reduced.

It is a further object of the invention to provide a tk roll whose heating width is limited only to the width of the web to be treated by the tk roll so that the end regions of the roll shell are not adversely heated.

It is a further object of the invention to provide such a tk roll in which, in addition to adjusting the temperature level of the jacket, temperature profiling is possible relatively steeply if necessary.

A non-essential further object of the invention is to provide a heated tk roll in which the deflection control devices and the heating devices can be integrated together in a new synergistic way.

It is a further object of the invention to provide a tk roll in which heating devices can be positioned so as not to interfere with the placement and operation of other devices.

In order to achieve the above and later objects, the invention is mainly characterized in that said induction. . the heating arrangement is arranged inside the shell of the tk roll in connection with its inner surface.

According to the invention, the induction heating device is placed inside the cylindrical shell of the tk roll and fixed to the stationary shaft of the tk roll and / or arranged in a new synergistic way on the sliding shoes of the tk roll.

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The tk roll according to the invention uses a relatively low frequency, preferably a mains frequency (50 Hz; 60 Hz), with an induction heating magnetizing current, whereby the penetration depth of the resistive induction heating effect is made sufficiently large and extends over substantially the entire thickness of the roll shell.

Most preferably, in the device according to the invention, the induction coil or coils and the magnetically conductive ferrite parts or the like connected thereto are placed in connection with the sliding shoes of the tk roll, whereby the air gaps of the ferrite parts with respect to the inner surface of the roll shell are kept constant.

If necessary, temperature profiling can be used in the heated tk roll according to the invention, which can be implemented either by using separate magnetic cores and / or excitation coils, to which separately adjustable electric currents and / or frequencies can be applied. The air gaps of the magnetic shoes can also be arranged to be adjustable.

In the invention, the temperature level and, if necessary, the temperature profile of the jacket of the tk roll can preferably be adjusted electrically, and the control can advantageously be integrated in the control of the deflection of the tk roll. This is important because both the temperature and the bending shape of the tk roll jacket affect the line pressure profile of the nip formed in connection with the tk roll, e.g. the press nip or the calendering nip.

In the following, the invention will be described in detail with reference to some application examples of the invention shown in the figures of the accompanying drawing, to the details of which the invention is not limited.

Fig. 1 shows a vertical cross-section of an induction-heated tk roll according to the invention, the induction heating device of which is arranged on the side of the central axis of the tk roll separately from the sliding shoes of the tk roll.

Figure 2 shows an embodiment of the invention in which the induction heating devices are arranged in connection with the sliding shoes of the tk roll.

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Figure 3 schematically shows an arrangement with which the temperature profile of the tk roll can be adjusted.

Figure 4 shows the same as Figure 3 of another temperature profiling solution.

According to Figure 1, the tk roll 10 comprises a jacket 10a with a smooth outer surface 10 'and a smooth inner surface 10'. A solid roll shaft 15 is placed in the interior space 16 of the shell 10a. If necessary, heating oil is introduced into the space 16 in a manner known per se in order to provide basic heating of the roll shell.

As is known per se, the Tk roll has a series of cylinder bores 21 in which pistons 23 are arranged. In connection with the pistons there are sliding shoes 25 with hydraulic lubricant chambers 26 to which pressure medium is introduced from the cylinder spaces 21 through bores 24. The shoes 25 have end faces 27 which slide along the inner surface 10 "of the jacket 10a. There are a plurality of pistons 23 and sliding shoes 25 attached thereto in the axial direction of the roll, and a different pressure can be applied to different cylinders 21 to compensate and adjust the tk roll jacket deflection.

According to Fig. 1, a magnetic shoe device extending over the entire length of the roll axis or a series of magnetic shoe devices 20 with a magnetizing core and a magnetizing coil or coils 30 is arranged on one side of the central axis 15 of the tk roll. with the inner surface 10 "of the roll shell 10a. When a magnetizing current of e.g. 50 Hz is applied to the coil 30 or a series of coils 30, a resistive heating effect based on eddy currents is generated in the roll shell 10a. Thus, the roll shell 10a heats up. small enough, e.g. 50 Hz, to cause the induction heating effect to extend over substantially the entire thickness of the roll shell 10a.

; * '* · The tk roll 10 schematically shown in Figures 3 and 4 comprises rotating ends 11 and stationary shaft pins 12, by means of which the roll 10 is mounted by bearings 13 in connection with its supports and frame structures. The center of rotation of the roll 10 is marked with a dotted line K-K.

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If necessary, heating oil is introduced into the roller flange 10a by means of devices known per se, from which el is not shown. The roll shell 10a is heated by induction heating devices to be described later and, if necessary, additionally by an oil layer or a similar intermediate flow.

According to the invention, the roll 10 is arranged to be resistively heated inductively and electrically-magnetically by eddy currents so that the temperature of the jacket 10a of the roll 10 is raised considerably high as a result of this heating. In order to implement inductive local heating inside the roll 10 in its axial direction in the same horizontal row, sub-cores 20lt 202 ... 20N of the magnetic core are arranged. These partial hearts 20h_! form a magnetic shoe device 20, which further includes a magnetic actuator coil 30 or each coil 301 ... 30H with its own coil (Fig. 3). The inductive heating is performed non-contact so that a small gap V is left between the magnet core and the inner surface 10 'of the roll 10, through which the magnetic fluxes of the magnetizing core close through the sheath 10a of the roll 10, causing a resistive heating effect.

Figure 3 shows each sub-core 201 ... 20H with its own excitation coil 301 ... 307. Another alternative embodiment of the invention is according to Figure 4, in which all sub-cores 201 ... 20H (N-16) have a common magnetizing coil 30.

According to an alternative embodiment of the invention, each sub-core is individually arranged to be displaceable in the radial plane of the roll 10 in order to adjust the size of the active gap of the excitation core and at the same time the heating effect. The transfer of the sub-cores can be arranged by various mechanisms. Said slits can generally vary, for example, between 1 ... 100 mm. With regard to mechanical gap adjustment devices, the structure of which is not shown in this connection, reference is made to the applicant's F1 patent No. 73260.

With respect to the electrotechnical background of the invention, the following is stated. When a variable magnetic field is provided in an electrically conductive material, eddy current and hysteresis losses are known to occur in the material and the material is heated. The power of eddy currents (P) depends on the strength of the magnetic field (B) and the frequency of change of the magnetic field (f) as follows P - B2 · f2 (1)

The variable magnetic field generated by the roll 30 is closed between the end face of the iron core of the device 20 and the slot V through the sheath 10a of the roll 10. This magnetic field induces eddy currents in the roll shell 10a which, due to the high resistance of the roll shell 10a, generate heat. Distribution of eddy currents induced in the jacket 10a in the radial direction x of the roll 10 follows the law I * - Ι0β · χΛΙ (2)

Ix is the current density at depth x from the inner surface 10 "of the roll shell 10a, I0 is the current density at the inner surface 10" of the shell 10a and S is the penetration depth. The penetration depth is defined as the depth at which the current density has dropped to 1 / e of the surface current density Ic. The penetration depth gives the expression i Λ ιο7ρ; ‘v« - \ - - o) - * · *: 2π 'ίμ fis ____ p is the resistivity of the substance, f is the frequency of the excitation current and μ is the relative permeability of the substance.

The expression shows that as the frequency increases, the penetration depth decreases. When steel is heated, both electrical conductivity and permeability decrease as the temperature increases.

: The invention generally uses heating powers in the range of 300-700 kW, preferably about 500 kW. As is known, the smaller the gap V • (Fig. 1), the larger part of the electrical power supplied to the device through the coil 30 is transferred to the jacket 10 of the roll to be heated.

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According to Fig. 2, the structure of the magnetizing shoes and the hydraulically loaded shoes 35 used in the deflection compensation of the roll shell 10a are synergistically integrated. Figure 2 shows an inductively internally heated tk roll 10 forming a nip N with a counter roll 50. A web W passes through the nip N, which is, for example, paper to be calendered in the nip N. The rollers 10 and 50 form part of a calender roll with a plurality of overlapping calender rolls arranged per se.

The combined slipper-magnetic shoe arrangement includes a press shoe 35, which preferably extends over the entire width of the web W. The shoe 35 is connected to a series of load cells 33 which are fitted to the load cylinders 31. A pressure medium is supplied to the load cylinders 31 via pipes 32 from a pressure source (not shown). A bore 34 is passed through the shoe 35 from the pressure space of the cylinders 31. The bore 34 opens at the central end face 37 of the shoe 35 into pressure spaces 36 bounded by the end faces 37 at the front and rear edges of the shoe 35 and at the edges of the shoe. By applying different pressure to the different cylinders 31, the tape 10a can be adjusted axially.

According to Fig. 2, ferrite parts are formed in connection with the pressure chambers 36 as the magnetic shoe core 38 of the induction heating magnetic shoe device, consisting of portions 38c and fixed inner portions 38b and adjustable edge portions 38a opposite the bottom planes of the pressure states. The air gaps V of the portions 38a with respect to the inner surface 10 "of the roll shell 10a are arranged to be adjustable. An insulating body 41 is attached to the upper surface of the ferrite portions 38c, on which a copper coil 40 with one or more turns is attached. The coil 40 has necessary turns and may The coil is supplied via a transformer from the AC mains at a frequency of, for example, 50 Hz or 60 Hz.

As shown in Figure 2, the ferrite portions 38a of the magnetic core are arranged to be adjustable so that their gap V with respect to the inner surface 10 "of the roll shell 10a is adjustable. The magnetic core 38 consists of a plurality of parallel core portions each individually controlled by -shoe 35. The stepper motors 42 have shafts using an adjusting nut or mandrel attached to the adjustable ferrite sections 38a at 44. By adjusting the slots V with the stepper motors 42, the magnetic flux density distribution in the axial direction of the roll 10 can be controlled to produce the roll 10 sheath 10a an inductive heating effect to obtain the just-desired temperature profile L on the roll shell 10a.

If necessary, heating oil or other medium can be introduced in the roll 10 according to Fig. 2 through the space 16 between its jacket 10a and the central shaft 15 in order to provide basic heating. It is also possible for such an embodiment of the invention to use both the excitation device 20 on the side of the central shaft 15 shown in Fig. 1 and the excitation device integrated in the sliding shoes 25. This device combination is preferably implemented in such a way that the stationary excitation device according to the figure sets the temperature level of the roll jacket 10a and the device integrated in the slipper or shoes 25 adjusts the gap gaps V of the magnetizing core 38.

The following claims set forth within the scope of the inventive idea, the various details of the invention may vary and differ from those set forth above by way of example only.

Claims (11)

1. Bk roller (10) with heated jacket (10a) comprising a roller shaft (15) and a roller shaft (10a) rotatably mounted on top thereof, between the roller shaft (15) and the lower surface (10 ") of the roller sheath (10a) is provided with a series of hydraulically or otherwise loaded piston-cylinder blending cylinders (22, 23), where there is one or more sliding shoes (25) having a sliding surface (27) with the inner surface (10 ") of the roller sheath (10a) and with which sliding shoes (25) one compensates or regulates the distribution of the bending of the roller sheath (10a) in the axial direction, and in order to heat men (10a) of the bk roller (10), an electromagnetic induction heating arrangement (20,30; 35,38,40), the function of which is based on the resistive heating effect of the eddy currents generated in the roller sheath (10a), characterized in that said induction heating arrangement (20,30; 38.40) Is arranged inside the male thread (10a) of the bk roller (10) in connection with its inner surface (10 "). 2. Bk roller according to claim 1, characterized in that in the space (16) between the roller sheath (10a) and the roller shaft (15), heating medium, such as oil, is heated, with which the roller sheath (10a) is heated together with the induction heating effect. 3. Bk roller according to claim 1 or 2, characterized in that the induction heating devices Ar are placed in communication. with the sliding shoe (35) or the shoes of the bk roller (10) (Figure 2). 4. Bk roll according to claim 3, characterized in that the induction heating devices comprise magnetically conductive core parts such as ferrite parts (38) arranged in connection with sliding shoes (35) or shoes, which have an air gap (V) with the inner surface (10). ) of the roller sheath (10a) and in connection with said - * · *. ferrite parts (38) or corresponding magnetically conductive magnetic core parts there is a magnetizing coil or coils (40). ... 5. Bk roll according to claim 3 or 4, characterized in that said magnetic beads (38) consist of magnetically conductive beads (38a, 38b, 38c) placed in the spaces (36) for printed white in the sliding foam (35) and the body of at least one of the parts forming a spring (V) with the inner surface (10 ") of the roller sheath (10) arranged to be controllable with functional devices (42) for controlling the level pi the induction heating effect and / or the distribution. 6. Bk roller according to the nigot of claims 1-5, cheek marking according to the directive, that the magnetizing device consists of a magnetizing core (20) placed outside the sliding shoe or shoe (25) and a magnetizing coil (30) in connection with this , wherein the upper surface of the magnetization core (20) forms an air space (V) with the inner surface (10 ") of the roller sheath (10) (Figure 1). 7. Bk roll according to the nigot of claims 1-6, cheek-drawn dirav, that for the magnetization at the induction heating, an electric current with rivet frequency (50-60 Hz) is used. 8. Bk roller according to the nigot of claims 1-7, chin-drawn dirav, that the power used for the induction heating in the bk roller (10) ir of the class about 300-700 kU, most adhesive about 500 kW. 9. Bk roller according to claim 1 or 2, characterized in that the distribution of the induction heating in the axial direction of the roller is controlled by using several separate magnetization cores, whereby an adjustable current is conducted in the individual magnetization coils (30, 30, ,) and / or that the body of the individual magnetization cores and the air space in relation to the inner surface (10 ") of the roller sheath (10a) to be heated is arranged to be adjustable (FIG. 3). 10. Bk roll according to claim 1 or 2, characterized in that the induction heating device comprises several parallel magnetization cores (20x. 20M) having a common magnetizing coil (30) and the air space (V) of said magnetizing coils (201). H) arranged to be adjustable for controlling the axial distribution of the induction heating effect. is 88419 11. Bk roller according to any one of claims 1-10, characterized in that the internally inductively heated bk roller (10) functions as a calender roller, most suitable in a so-called. gradient calender, the bk roll (10) forms a calendering nip (9) with its counter roll (50), through which nip (N) the paper web (W) to be calendered has been passed.