Metal working – Method of mechanical manufacture – Roller making
Reexamination Certificate
2001-12-27
2004-11-23
Jimenez, Marc (Department: 3726)
Metal working
Method of mechanical manufacture
Roller making
C029S895220, C492S047000
Reexamination Certificate
active
06820336
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application claims priority on Finnish Application No.20002885 filed Dec. 29, 2000, the disclosure of which is incorporated by reference herein.
STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT
Not Applicable.
BACKGROUND OF THE INVENTION
The invention relates to a method of making a roll end for a roll in a paper or board machine or in a finishing machine, which roll end comprises a whole formed by an end flange and an axle journal, as well as a duct system situated inside the material of the roll end.
The invention relates particularly to a method of making a roll end for a heatable roll, which roll end comprises a whole formed by an end flange and an axle journal, as well as a duct system which is situated inside the material of the roll end and through which in a finished roll end a heat transfer medium intended for heating the roll is arranged to circulate from outside the roll through the axle journal and the roll end into bores of a roll shell and back.
The invention also relates to a heatable roll in a paper or board machine or in a finishing machine, which roll comprises a roll shell and roll ends which comprise an end flange and an axle journal and which are attached to the ends of the roll shell in the axial direction, the roll shell being provided with axial ducts for a flow of a heat transfer medium and at least one of the roll ends being provided with an axial central duct for passing the heat transfer medium into the roll and out of it, as well as with connecting ducts connecting the central duct and the axial ducts of the roll shell.
Heatable rolls, or so-called thermo rolls, are used, as known, in paper and board machines as well as in paper/board finishing machines, such as calenders, supercalenders and equivalent. The heating of these rolls is generally provided such that a heating medium, for example, water, steam or heating oil is passed into the roll through a roll end for heating the roll shell to a desired temperature. Most commonly, mainly axial bores have been formed in the roll shell and a heating medium has been made to circulate in them. Today, the roll ends of thermo rolls are manufactured by machining out of forging blanks made of tempering steel. The requirements for the material are high because the roll end, which comprises an end flange and an axle journal, is very heavily loaded in particular in a roll replacement situation. Moreover, the roll end is complicated in construction and expensive to accomplish because it includes a large number of blind hole bores in different directions. All ducts have been produced as blind hole bores or, in a corresponding manner, as through bores which have been plugged. In order to reduce the heat load of the roll bearing, a special vacuum insulation sleeve is used inside the axle journal, and the manufacture of this sleeve also causes additional costs. Duct systems are also needed for various purposes in roll ends of a number of rolls other than merely heatable rolls, in which connection the problems associated with the manufacture of these duct systems in particular are similar to those in connection with heatable rolls.
With respect to the state of the art, reference is further made to the publications DE 40 36 121 A1 and DE 44 04 922 C1, which also show quite clearly how many bores must be formed in the roll end in order to make it operative. In DE publication 44 04 922, these bores have additionally been produced as said blind hole bores, the making of which requires special precision. Another drawback in a system of blind hole bored ducts is constituted by sharp elbows which are produced in it and which are not optimal from the viewpoint of the flow of a medium, but which cannot be avoided by any means in boring.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a new method of making a roll end for a heatable roll in a paper or board machine or in a finishing machine, which method is simpler than prior art methods and which method makes it possible to avoid making bores requiring high precision in the roll end and avoid other drawbacks associated with making these bores. Further, an object of the invention is that the strength properties of the roll end manufactured in accordance with the new method are superior to those of the roll ends manufactured in accordance with the state-of-the-art methods and thus it withstands better high loads. With a view to achieving these objects as well as those coming out later in the description, the present invention is mainly characterised in that the roll end is made by a powder metallurgy process in a mould such that at least a duct system that is placed in an end flange of the roll end is formed in connection with the stage of making the roll end by the powder metallurgy process. Advantageously, the duct to be provided in the axle journal is also formed in the same stage of manufacture. A hot isostatic pressing process in particular is used as the method of manufacture.
In the method of making the roll end, the duct system to be placed in the roll end is made first into a finished construction out of pipes by welding, the thus made pipe system is placed in a mould, the mould is filled with a metal powder and the manufacture is carried out under hot isostatic pressure.
Further, in the method, when the duct system is made, an encased cavity/encased cavities is/are formed on the pipes remaining inside the axle journal by means of a closed sleeve disposed on said pipes or by a similar means. The cavity/cavities is/are advantageously left empty or they are provided with a vacuum by suction.
In accordance with the method, the pipe system is advantageously coated on the outside with a heat insulating coating layer before the pipe system is disposed in the mould. The coating is preferably accomplished by flame spraying or by plasma spraying, and zirconium oxide or an equivalent material is used as the coating material.
In the manufacturing method, a high-alloy material, advantageously a gas-atomised medium-carbon tempering steel powder, is used as the powder metal material.
In accordance with the method, in the axle journal of the roll end, a powder material that conducts heat more poorly than steel, such as a metal matrix composite, is used at a desired depth in the region which will be under a bearing.
In the method, the pipe system forming the duct system is advantageously made out of a seamless pipe or a hollow bar, in particular out of a pipe/bar the material of which is austenitic stainless steel.
When a blank of the roll end has been made by a powder metallurgy process, the mould is dismantled, broken or machined off, and the blank is machined into a desired shape and dimensions.
The heatable roll in accordance with the invention is mainly characterised in that the roll end is made by a powder metallurgy process and that at least the connecting ducts which are provided in it and which connect an axial central duct and axial ducts of a roll shell are formed in connection with the making of the roll end.
Most advantageously, the central duct of the roll end is also formed in connection with the making of the roll end.
The duct system provided in the roll end is made in advance into a finished construction out of pipes by welding, which construction is left inside the material of the roll end in connection with the manufacture of the roll end.
The connecting ducts of the roll end in the roll in accordance with the invention advantageously comprise a radial portion and an axial portion. Between the radial portion and the axial portion there is advantageously a curved portion which connects them.
At the roll end, the axial portions of the connecting ducts which are connected to the axial ducts of the roll shell most advantageously come perpendicularly out of the end flange of the roll end.
The connecting ducts in the roll end are advantageously arranged to lead as separate ducts to the axial central duct provided in the axle journal.
The invention provides a
Kiiski Erkki
Koivukunnas Pekka
Laitinen Arttu
Leinonen Erkki
Tervonen Matti
Jimenez Marc
Metso Paper Inc.
Stiennon & Stiennon
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