Metal working – Method of mechanical manufacture – Roller making
Reexamination Certificate
2003-03-04
2004-03-23
Cuda-Rosenbaum, I (Department: 3726)
Metal working
Method of mechanical manufacture
Roller making
C492S046000, C419S049000
Reexamination Certificate
active
06708407
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a method for manufacturing a thermoroll for a paper/board machine or a finishing machine including a shell made by casting and/or powder metallurgical methods.
BACKGROUND OF THE INVENTION
Heatable rolls, that is, thermorolls, are commonly used in paper machines and paper finishing or converting machines, especially in calenders and multi-roll calenders, the length of the said thermorolls being as much as 10 m, their diameters being typically of the order of approximately 500-1000 mm—with soft calender rolls 1200-1650 mm. The heating of the rolls is usually carried out by means of a heating medium, such as steam or hot water or oil. Thermorolls are typically formed by drilling axial bores close to the outer surface of the roll shell, the diameter of the bores being typically about 25-50 mm, and through which bores the heating medium is passed from one axial end of the roll to its opposite end. There are typically several such bores, distributed evenly in the circumferential direction of the roll. The heating medium may circulate in the bore, for example, once from one end of the roll to the other, or twice or several times so that in adjacent bores, the heating medium travels in opposite directions.
FIGS. 1 and 2
show a prior art thermoroll of this type, in which a shell
2
is attached to end flanges
16
,
18
provided with axle journals
15
,
17
, in which shell are formed axial bores
3
, of which there are several, distributed evenly in the circumferential direction. In the axle journal
15
is formed an axial bore
14
, to which is fitted a pipe
11
extending to the opposite end flange
18
. Between the outer surface of the pipe
11
and the interior surface of the axial bore
14
remains an annular slot. The heating medium is supplied to the roll
1
from the first end (the end with the axle journal
15
) through a pipe
11
and passed via the radial bores
12
at the opposite end to the bores
3
, and along them back to the first end, and via the radial bores
13
to the said annular slot in the axle journal
15
and from there out of the roll.
A problem associated with thermorolls provided with this type of prior art bores relates to making the axial bores by means of long hole drilling, which is relatively slow and expensive. Long hole drilling is made particularly demanding by the formation of material structure boundary surfaces in the wall construction of the shell due to the manufacturing technique. The cementite microstructure in chill cast thermorolls is brittle and susceptible to breakage due to the effect of mechanical and thermal loads. Variation in the thickness of the cementite layer may in addition cause curving of the rolls when heated. Intergranular corrosion may also occur due to paper auxiliaries. Furthermore, the current trend towards increasingly high temperatures increases the problems caused by the thermal fatigue of materials. To improve wear resistance, chilled rolls have to be coated, for example, by hard chromium plating.
OBJECTS AND SUMMARY OF THE INVENTION
Thus, one of the aims of the present invention is to achieve an improved thermoroll, where long hole drilling and other prior art disadvantages are avoided. The aim is, moreover, to achieve a roll, where good heating properties are obtained for the outer surface of the roll. To achieve this aim, it is characteristic of the thermoroll relating to the invention that the shell is made by means of casting or powder metallurgical methods, and that the ducts are formed in the matrix material of the shell which is of metal, ceramic or a composite, directly in connection with manufacture.
Of the method relating to the invention for manufacturing a thermoroll it is, on the other hand, characteristic that the shell is made by means of casting and/or powder metallurgical methods, and that the ducts are formed in the matrix material of the shell which is of metal, ceramic or a composite, directly in connection with manufacture, without machining. The object of the present invention is to provide a thermoroll for a paper/board machine or a finishing or converting machine, the said thermoroll comprising a shell of metallic, ceramic or composite material, the shell incorporating ducts for passing a heating medium from one axial end of the shell to its opposite end.
A further object of the invention is to provide a method for manufacturing a thermoroll for a paper/board machine or a finishing or converting machine, the said thermoroll comprising a shell of metallic, ceramic or composite material, the said shell incorporating ducts for passing a heating medium from one axial end of the shell to its opposite end.
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Leinonen Erkki
Viljanmaa Mika
Cuda-Rosenbaum I
Metso Paper Inc.
Steinberg & Raskin, P.C.
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