Heat exchange – Movable heating or cooling surface – Rotary drum
Patent
1991-11-06
1993-12-21
Bennet, Henry A.
Heat exchange
Movable heating or cooling surface
Rotary drum
34124, F28D 1102
Patent
active
052714560
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements to drying cylinders of the type that ar especially encountered in plants for manufacturing cardboard, paper or the like.
2. Discussion of Background Information
Drying cylinders are heated by pressurized steam introduced into their internal cavity. The present invention relates more particularly to the removal of the condensates which form inside these drying cylinders.
The presence of condensates in the cylinder impairs the heat transfer between the steam and the cylindrical casing whose external wall is in contact with the paper or cardboard, whereby the effectiveness of the drying is reduced. Moreover, when the cylinder is stopped, the presence of condensates inside causes localized deformations of the casing due especially to temperature gradients. On restarting the cylinders, these deformations alter the quality of the drying, in a cyclic manner which can, in the manufacture of cardboard, for example, cause internal pasting defects.
Means for recovery of the condensates inside the cylinders do exist. A device described in U.S. Pat. No. 3,449,839 proposes two modes of recovery. A first mode consists in recovering the condensates by means of a fixed scoop maintained at a distance from the internal wall of the cylindrical casing. This device has the disadvantage of being fragile and often not very effective by reason of the difficulty in maintaining a precise clearance between the scoop and the cylindrical casing. A second system consists of suction recovery from a fixed point of the casing of the cylinder. This system has the disadvantage, when the cylinder stops rotating, of leaving the condensates in the cylinder. The suction head is randomly located within the space and becomes totally ineffective if its stop position does not correspond with the bottom point.
Other recovery devices are described especially U.S. Pat. No. 1,575,249 and DE-A-3,143,347. In these two documents, the condensates are recovered by means of orifices pierced into the ends of the cylinder, which orifices are in communication, via channels, with the shaft of the cylinder whereby the condensates escape.
These devices comprise only a limited number of orifices for evacuating the condensates. When the cylinder stops, the condensates can stagnate in the bottom if an evacuating orifice is not located at the bottommost point.
Moreover, these arrangements and, in particular, the orifices pierced in the ends, weaken these ends and the cylinders.
SUMMARY OF THE INVENTION
The present invention enables all these disadvantages to be overcome. The system for extracting condensates according to the invention makes it especially possible to be freed from the problems connected with the stopping of the cylinders in a random position; it enables condensates to be extracted in any position of the cylinder when it is stationary. The extraction system according to the invention enables condensates to be extracted continuously and permanently, whether the cylinders are moving or not. It also enables condensates to be extracted for all rotational speeds of the cylinder.
Another advantage of the extraction system according to the invention resides in the fact that it makes it possible to extract the condensates in cylinders comprising a corrugated internal wall, whether these corrugations are obtained by machining or by addition of surface-disrupting bars.
A further advantage of the system for extracting the condensates, according to the invention, resides in the fact that it imposes no maintenance constraint during the entire life of the equipment.
The device for extracting steam condensates in the drying cylinders according to the invention is constituted by at least one disk-shaped partition, through which passes the duct which enables steam to be introduced into the internal cavity of the cylinder, which partition is disposed, in front of one of the corresponding ends of the cylinder, in the cavity and comprises, on its periphery, means enabling
REFERENCES:
patent: 1575249 (1923-12-01), Berry et al.
patent: 3449839 (1966-07-01), Crist
patent: 3612171 (1971-10-01), Trautner
patent: 3675337 (1972-07-01), Daane
patent: 4252184 (1981-02-01), Appel
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