Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Patent
1999-05-07
2000-08-08
Pelham, Joseph
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
492 46, F28F 502, D21G 100
Patent
active
061005088
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a heated roller of the type in which the heated roller has a cylindrical roller body that rotates around its axis and has an outer cylindrical surface that serves as the roller working surface. The roller has a first inside cavity arrangement as well as a second cavity arrangement in the form of several elongated axis-parallel channels, separate from one another, that are evenly distributed over the circumference of the roller body and which are sealed at their ends.
Axis-parallel channels have long been known in connection with heating of rollers, e.g. from DE-GM (utility model) 90 14 117, where they don't form a closed system, however, but rather have a heat carrier fluid flowing through them which is heated and pumped in circulation outside the roller.
In German Patent 40 33 986 A1, no heating elements are arranged in a central bore of the roller body, and rod-shaped electrical heating elements are arranged in the peripheral channels, which are partially filled with a convection fluid capable of boiling.
Elongated axis-parallel channels can be produced in the roller body using known means, with relatively little effort, and leave the roller body essentially unimpaired in its stability. The term "elongated channels" in this contexts means that the cross-sectional area of the channel is not important and that the length of the channels is a multiple, e.g. 20 to 150 times, of the cross-sectional dimension. In practice, these are so-called peripheral bores made in the roller body close to its outside circumference. These bores contain the heating elements, the connections of which must be brought out at the ends. This requires complicated seals, because of the high pressures in the bores. Because of the closeness of the heating elements to the roller circumference, the temperature distribution in the circumference direction of the roller circumference is frequently uneven.
SUMMARY OF THE INVENTION
The invention is directed to the problem of structuring a roller of this general type in such a way that the effort and expense involved in its production are reduced and its properties in operation are improved.
The apparatus of the invention provides for a heated roller having a first inner cavity and a second cavity arrangement, located radially exteriorly of the first inner cavity, and taking the form of several elongated axis-parallel channels distributed beneath and evenly along the outer working surface of the roller. An electrical radiant heating system is located in the first cavity, and extends along the length of the roller.
In the invention, the elongated channels are individually and partially filled with water, and then sealed to be pressure-tight. The air is evacuated from the channels after they have been charged with water, since otherwise air plugs would form in the channels, preventing condensation of the steam. If a temperature reduction occurs at a location of a bore during operation, the steam located there, in the free space of the cavity not filled by the water, will condense at that location, thereby causing condensation heating which immediately brings the location in question back to the temperature prevailing in the surroundings. Therefore automatic temperature equalization over the surface of the roller body takes place.
Because of the arrangement of the radiant heating system in the first inside cavity, heat distribution at the roller circumference (i.e., the outer cylindrical working surface of the roller body) becomes more uniform. The sealing expense and effort for bringing the electrical connections out at the channels is also eliminated, since these no longer contain any heating elements.
According to one embodiment of the invention, the channels are sealed at their ends by plugs that have been inserted into the channels. Alternatively, the channels can be sealed towards the outside of at least one end of the roller body by a common sealing ring.
Since the sealing rings and the plugs must be leak-proof and able to w
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F. Wagner, "Die Elektrische Walzenheizung", die elektrische ausrustung, No. 2, Apr. 20, 1996. Cited in Specification.
Eduard Kusters Maschinenfabrik GmbH & Co. KG
Pelham Joseph
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