Method for regulating the temperature of an adjustable-crown roll and regulation system intended for carying out the method

Abstract: The invention concerns a method for regulating the temperature of an adjustable-crown roll. The roll mantle (12) arranged revolving on the stationary axle (11) of the roll (10) is loaded by passing a pressure medium into a pressure chamber (15) or series of chambers formed between the axle (11) and the mantle (12) so as to correct the deflection of the roll mantle (12). The roll (10) is additionally heated/cooled by passing heating/cooling fluid into the roll (10). The heating/cooling fluid used for the regulation of the temperature of the roll (10) is introduced into the roll (10) as substantially uniformly distributed over the areas of the roll (10) in which heat is removed/produced in the radial direction of the roll. The heating­ /cooling fluid is passed into the pressure chamber (15) in the roll (10), in which case, by its means, pressurization of said chamber (15) is also carried out, and/or into the unpressurized chamber (16) of the roll (10), in which case the function of the fluid is ex­ clusively regulation of the temperature. The invention further concerns a regulation system intended for carrying out the method.

Description: The invention concerns a method for regulating the temperature of an adjustable-crown roll, according to the preamble of claim 1. The invention further concerns a regulation system intended for carrying out the method in an adjustable-crown roll, according to the preamble of claim 4. The preambles of claims 1 and 4 are based on GB-A-1,185,937 In paper machines, such rolls are commonly used as form a dewatering press nip, a smoothing nip, or a calendering nip together with a backing roll. In these purposes of use, and so also, e.g., in a supercalender, it is important that the distribution of the linear load, i.e. the profile, in the nip in the axial direction of the rolls can be made invariable or that this profile can be regulated as desired, for example, in view of controlling the transverse moisture profile and/or thickness profile (caliper) of the web. For this purpose, in prior art, several different adjustable-crown rolls are known, by whose means attempts are made to act upon the distribution of the linear load in a nip. As a rule, such rolls comprise a massive or tubular, stationary roll axle and a roll mantle arranged revolving around said roll axle. Between said axle and said mantle, a glide-shoe arrangement and/or a chamber or series of chambers of pressure fluid are fitted, which act upon the inner face of the mantle, so that the axial profile of the mantle at the nip can be straightened or adjusted as desired. The present invention is in particular related to such variable-crown rolls in which there is a chamber or series of chambers of pressure fluid between the roll axle and the roll mantle, the distribution of linear load of the roll being adjusted as desired by passing pressure medium into said chamber or series of chambers. In such rolls, one problematic point consists of the temperature profile of the roll. Especially in rolls in which the roll mantle is provided with a resilient coating, such as a polyurethane or rubber coating, it is important that the temperature level of the roll mantle should be sufficiently low and uniform. A uniform temperature promotes the formation of a uniform linear load as well as uniformity of the operation of the roll nip in the transverse direction of the web. In the prior-art rolls of the type described above, attempts have been made to affect the roll temperature, e.g., so that, into the pressure-fluid chamber in the roll, cooling/heating fluid has been fed from one end of the roll, and the return-fluid duct has been provided at the opposite end of the roll. In such a roll, the temperature of the roll mantle is, however, not uniform in the transverse direction of the roll, but the temperature of the roll mantle is changed towards the other end of the roll, becoming higher or lower in a linear way, depending on whether cooling fluid or heating fluid is supplied into the pressure-fluid chamber. Additionally, attempts have been made to solve the problem of roll temperature so that, especially in rolls that require cooling, the cooling fluid has been passed into the pressure-fluid chamber, e.g., from two points. This has, however, had the consequence that the temperature distribution in the roll has been highly uneven. According to a third alternative, in prior-art solutions, the regulation of temperature has been arranged, in particular in rolls to be cooled, so that the cooling fluid has been passed into the pressure-fluid chamber in the roll out of one end and removed through the opposite end, whereas the circulation of cooling fluid in the unpressurized chamber in the roll has been arranged in the opposite direction. This has, however, resulted in the substantial drawback that the temperature profile of the roll has been highly complicated, which is an even worse drawback than a linear change in the temperature. The object of the present invention is to provide an essential improvement over the prior-art solutions and to avoid the drawbacks related to the regulation of the temperature in prior-art adjustable-crown rolls. In view of achieving this, the method in accordance with the invention is characterized by the features stated in the characterizing portion of claim 1. The invention may be carried out so that fluid intended for regulation of the temperature is fed into the unpressurized space or chamber between the roll mantle and the axle as uniformly distributed across the axial length of the roll. On the other hand, the regulation system in accordance with the invention is characterized by the features stated in the characterizing portion of claim 4. By means of the invention, a number of significant advantages are obtained over prior art, of which, e.g., the following should be stated. By means of the method of the invention, a highly uniform temperature profile is obtained, because, especially in rolls that require cooling, the cooling fluid is passed both into the pressure chamber in the roll and into the unpressurized chamber in the roll as substantially uniformly distributed over the areas that require cooling. Moreover, the pressurization of the pressure fluid is taken care of by means of the same circulation of fluid, so that cooling fluid and pressure fluid need not be fed into the pressure chamber separately. It is a further remarkable advantage of the invention that the method and the system in accordance with the invention can be applied as such to existing variable-crown rolls. The further advantages and characteristic features of the invention come out from the following detailed description of the invention and of the appended claims 6 to 8. In the following, the invention will be described in detail with reference to the figures in the accompanying drawing. Figure 1 is a schematical cross-sectional view of a variable-crown roll which forms a nip with a backing roll and to which the method and the system in accordance with the invention can be applied. Figure 2 is a schematical longitudinal vertical sectional view of a roll shown in Fig. 1 and of the fluid circulation system in the roll. In Fig. 1, the variable-crown roll is denoted generally with the reference numeral 10. The roll 10 forms a nip N with a backing roll, which is denoted with the reference numeral 5. The roll 10 comprises a stationary axle 11, on which the roll mantle 12 is arranged as revolving. The mantle 12 is provided with a coating 13, which may be, e.g., polyurethane, rubber, or equivalent. The construction of the roll 10 shown in Fig. 1 is such that therein, between the roll axle 11 and the roll mantle 12, a pressure-fluid chamber or a series of chambers is provided, the profile of the roll mantle being straightened by feeding pressure fluid into said chamber or series of chambers. Said pressure chamber, i.e. the first chamber, is denoted with the reference numeral 15. The pressure chamber 15 is additionally defined by longitudinal seals 14, by means of which the roll axle 11 is sealed relative the inner face of the mantle 12 so that a second chamber 16 remains at the other side of the longitudinal seals 14, which said second chamber is unpressurized or in which the pressure is at least substantially lower than the pressure present in the pressure chamber 15. Moreover, in Fig. 2, it is shown that the roll mantle 12 is supported on the roll axle 11 as revolving by means of end bearings 17 and that, in the areas of the roll ends, the pressure chamber 15 is sealed by means of end seals 18. In Fig. 2, the reference denotation in refers to the web that runs through the nip N. Fig. 2 is a schematical illustration of a fluid-circulation and temperature-regulation system of a variable-crown roll 10. The pressure fluid required for pressurization of the pressure chamber 15 is fed into the roll through the first circuit, i.e. the primary circuit 20, from which it is passed into the pressure chamber 15 through the nozzles 21. In order that the pressure in the pressure chamber 15 could be maintained at the desired level, an outlet pipe 23 is connected to the pressure 15, said pipe 23 communicating with a regulator 25 of pressure difference, through which the fluid passed out of the pressure chamber 15 is passed further along the feed pipe 26 into the unpressurized second chamber 16. The pressure fluid passed through the primary circuit 20 into the pressure chamber 15 is kept at the suitable temperature so that, if the roll 10 requires cooling, said pressure fluid operates as cooling fluid at the same time. By means of the several nozzles 21, which are distributed evenly across the length of the roll 10, attempts have been made to illustrate schematically that the pressure/temperature-regulation fluid, which is, for example, cooling fluid, is introduced into the pressure chamber 15 in the roll as substantially uniformly distributed across the axial length of the roll. Fluid is introduced into the pressure chamber 15 in a necessary amount to keep the roll temperature at the correct level, and the regulation of the pressure in the pressure chamber 15 is arranged by means of the pressure-difference regulator 25 by pacing any excess fluid through said pressure-difference regulator 25 out of the pressure chamber 15 into the second chamber 16. According to Fig. 2, the roll 10 is additionally provided with a second fluid circulation circuit, i.e. secondary circuit 30, by means of which the temperature-regulation fluid is passed into the unpressurized second chamber 16 in the roll. In the case of Fig. 2, said temperature-regulation fluid is cooling fluid. Through the secondary circuit 30, the cooling fluid is passed into the second chamber 16 in the roll through a number of nozzles 31, so that the cooling fluid is fed as substantially uniformly distributed over the axial length of the roll. In the embodiment of Fig. 2, the secondary circuit 30 also takes care of the lubrication of the end bearings 17 of the roll, and for this purpose the secondary circuit 30 is provided with lubrication nozzles 32, through which fluid is passed to said end bearings 17. Moreover, the second chamber 16 in the roll is connected with a return pipe 40, through which any excess fluid is passed out of the second chamber 16 in the roll into the tank (not shown) and to recirculation. Thus, with reference to the above description, it is an essential feature of the invention that the cooling/heating fluid is passed to the roll as substantially uniformly distributed over the areas that require heating or cooling and that the pressurization of the pressure chamber 15 in the roll 10 is also taken care of by means of the same heating/cooling fluid. In respect of Fig. 2, it should be stated further that therein such a roll 10 is shown as is provided with a unified pressure chamber 15 which extends from end to end in the roll. The invention can, however, also be applied to rolls in which the pressure chamber 15 is divided into a series of chambers by means of transverse seals, into which said separate chambers in a series of chambers it is possible to feed pressures of different levels. In such a case, of course, each chamber in the series of chambers must be provided with an outlet pipe and with a pressure-difference regulator of its own. Above, the invention has been described by way of example with reference to the example shown in the figures in the accompanying drawing. The invention is, however, not supposed to be confined to the example described alone, but many variations are possible within the scope of the inventive idea defined in the attached patent claims.

Claims: Method for regulating the temperature of an adjustable-crown roll, in which said roll (10) the roll mantle (12) arranged revolving on a stationary axle (11) is loaded by passing a pressure medium into a pressure chamber (15) or series of chambers formed between the axle (11) and the mantle (12) so as to correct the deflection of the roll mantle (12), said pressure chamber/chambers being sealed from a substantially unpressurized chamber (16) between the axle (11) and the roll mantle (12) characterized in that the pressurization of the pressure chamber (15) or the series of chambers in the roll (10) is carried out by means of a heating/cooling fluid used for regulation of the temperature of the roll (10) introduced into the roll (10) and substantially uniformly distributed over the areas of the roll (10) in which heat is removed/produced in the radial direction of the roll and in that any excess amount of fluid is passed out of the pressure chamber (15) into the unpressurized chamber (16) in the roll through a pressure-difference regulator (25), said unpressurized chamber (16) being additionaly fed with said heating/cooling fluid from another source (30). Method as claimed in claim 1, characterized in that the fluid intended for regulation of temperature is fed into the unpressurized chamber (16) between the roll mantle (12) and the axle (11) as uniformly distributed over the axial length of the roll (10). Method as claimed in any of the preceding claims, characterized in that, when the fluid intended for regulation of temperature is cooling fluid, it is introduced into the roll (10) at a temperature colder than the temperature of equilibrium of the roll (10) and, in a corresponding way, when the fluid intended for regulation of temperature is heating fluid, it is introduced into the roll (10) at a temperature hotter than the temperature of equilibrium of the roll (10). Regulation system intended for carrying out the method as claimed in any of the preceding claims in an adjustable-crown roll (10), which comprises a roll mantle (12) arranged as revolving on a stationary axle (11) by means of end bearings (17), said axle (11) and roll mantle (12) being sealed relative one another by means of longitudinal seals (14) so that, between the axle (11) and the roll mantle (12), said longitudinal seals (14) define a substantially unpressurized chamber (16), on one hand, and a pressure chamber (15) or a series of chambers, on the other hand, the deflection of the roll mantle (12) being corrected by means of the pressure of the pressure medium supplied into said pressure chamber (15) or series of chambers, and in which said roll (10) circulation devices are provided for supplying pressure fluid to the pressure chamber/chambers, characterized in that said circulation devices comprise a first fluid-circulation circuit, i.e. a primary circuit (20), which is arranged to supply fluid for regulation of the temperature of the roll into the pressure chamber (15) of the roll, which said fluid is pressurized to the positive pressure required for the correction of the deflection of the roll mantle (12), as well as a second fluid-circulation circuit, i.e. a secondary circuit (30), which is arranged to supply same fluid for regulation of the temperature into the unpressurized chamber (16) in the roll, and in that the pressure chamber (15) communicates with the unpressurized chamber (16) through a pressure-difference regulator (25), through which any excess fluid is arranged to be passed from the pressure chamber (15) into the unpressurized chamber (16). Regulation system as claimed in claim 4, characterized in that the primary circuit (20) is provided with a number of nozzles (21) fitted as substantially uniformly spaced over the length of the roll mantle (12) so as to introduce the fluid intended for regulation of temperature into the pressure chamber (15) as substantially uniformly distributed. Regulation system as claimed in claim 4 or 5, characterized in that the secondary circuit (30) is provided with a number of nozzles (31) fitted as substantially uniformly spaced over the length of the roll mantle (12) so as to introduce the fluid intended for regulation of temperature into the unpressurized chamber (16) as substantially uniformly distributed. Regulation system as claimed in any of the claims 4 to 7, characterized in that the secondary circuit (30) is provided with lubrication nozzles (32) for lubrication of the end bearings (17) of the roll (10).

Inventors: ESKELINEN JUHANI, NISKANEN JUHANI, ESKELINEN, JUHANI, NISKANEN, JUHANI
Applicants: VALMET PAPER MACHINERY INC, VALMET PAPER MACHINERY INC.
Application year: 1990
Main classification: D21G1
IPC codes: D21G1, F16C13