Drying and gas or vapor contact with solids – Apparatus – For diverse operations on treated material
Patent
1990-07-05
1991-10-29
Bennet, Henry A.
Drying and gas or vapor contact with solids
Apparatus
For diverse operations on treated material
34155, F26B 1900, F26B 1300
Patent
active
050603973
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for heat treatment of material, particularly infra-red radiation of a continuous paper web in a paper machine and is more closely defined in the preamble of claim 1.
It is previously known to expose e.g. a continuous paper web in a paper machine to infra-red radiation for drying the web wholly or partially. Hereby, the infra-red radiation creates a great heat potential, which entails the need for cooling the radiation and protection of the paper web against smear spots and other polution, the risk of fire and unequal drying. For achieving such a protection, supply and/or exhaust air currents are used, which affect the radiation and the paper web. These currents are provided to bring about guaranteed cooling, but without minimizing the efficiency of the drying process and without adversely affecting the path of the web, respectively. These demands have, so far, not been met by previously known techniques.
Such apparates do often comprise a s.c. counter reflector provided to throw back part of the heat radiation having passed through the paper against same. It is desirable, for making the drying process more efficient, to arrange the counter reflector as close to the paper web as is possible. Hitherto, the counter reflector had, however, to be arranged at relatively large distance to the paper web, for various reasons, which brought about decreased efficiency. The same applies to the reflector itself with the radiation source which, mainly because of security reasons, had to be arranged at relatively large distance from the paper web in previously known apparates, which rendered a clearly worse degree of efficiency. Of major importance in this connection is, however, the guidance of the web, which so far, for certain combinations of paper weight, structure, moisture contents, free length in the direction of the web etc, has been adversely affected by reflectors arranged too closely nearby, because of negative affects of the cooling air currents on the web. Further drawbacks of known techniques are great waste of power, difficulties to perform maintenance and service, maintaining an equal degree of efficiency and need for frequent service.
The object of the invention is to provide an improved apparatus of the kind as initially defined, which avoids the said drawbacks. A superior purpose of the invention is to provide a basis for using the components comprised by the apparatus as efficiently as possible, to increase the level of efficiency substantially and to provide, in spite of these advantages, the same or even increased security. A further object of the invention is to improve techniques in this field in various other respects.
These objects are achieved according to the invention in that an apparatus of the kind as initially defined substantially is characterized by the features of the characterzing clause of claim 1. Thanks to these features, it is possible to arrange the radiator with the reflector very close to e.g. a paper web, namely, according to obtained test results, at 20 mm distance between protective glas panes and a paper web, which is to compare with app. 50 mm according to previously known technique. In such a way, a much more extensive drying is, of course, obtained and the level of efficiency may be increased further by arranging even the counter reflector closer to the web. In spite of these features, it is possible to ensure an advantageous web guiding, which is not or only negligibly affected by e.g. air currents. Said features do also safeguard, that the apparatus is, as far as possible, kept free from dirt. The lack of substantial free air currents brings about a degree of purity which is unknown so far, and which considerably increases both efficiency and safety.
Furthermore, the concept of overlapping protective panes offers the advantage, that tolerances and thermical expansion won't affect the tightness of the assembled glas surface.
Further characteristics of and advantages with the invention are revealed by the following specificati
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Bennet Henry A.
Infrarodteknik AB
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