Cleaning and liquid contact with solids – Processes – With work or work parts movable during treatment
Reexamination Certificate
1999-10-06
2001-10-30
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
With work or work parts movable during treatment
C134S018000, C134S032000, C134S144000, C134S12200P, C134S015000
Reexamination Certificate
active
06309472
ABSTRACT:
FIELD OF THE INVENTION
Our present invention relates to a method of and to an apparatus for the cleaning of rolls used in strip casting, rolling mills and/or other strip processing lines and especially the rolls used for dressing mill stands, sizing mill stands and finishing mill rolls, including mill rolls for the after-rolling of strip following the usual rolling process.
More particularly, the invention relates to a method of cleaning the rolls or rollers of a strip line of a type described which is used in the production and the processing of metal strip in all stages, including initial production, sizing, finishing and surface formation. The invention especially relates to a system in which the roll is cleaned by a jet from at least one nozzle of a cleaning liquid and in which the nozzle is moved back and forth along the roll. The metal strip to which the invention is applicable includes steel strip.
BACKGROUND OF THE INVENTION
It is known, especially in conjunction with zinc coating lines or galvanizing lines, to integrate dressing roll stands in the strip processing line to thereby emboss or otherwise impart certain surface properties to the strip and to alter in a targeted way the properties of the strip being processed. In such cases there is the danger that zinc particles, for example, which are only partly adherent to the strip can be transferred to the working and back-up rolls of a stand in the strip line. The zinc particles which remain adherent to the surface of the roll tend to be pressed into the surface with time and to imprint on subsequently rolled products, thereby introducing defects which may make a portion of the product unusable, which can require cutting out and scrapling of a portion of the product, and which can decrease productivity.
In order to reduce the risk of adhesion of particles on the rolls of a strip line and especially the rolls of a dressing mill or stand, it is known to operate the dressing stand in a wet condition. The result is a wet rolling of the strip under conditions in which particles tend to remain in the liquid and not to adhere to the dressing rolls.
Cleaning devices for such rolls in the form of brushes, fleece rollers and fleece cushions are known, these units being either as wide as the widest metal strip to be processed or being mounted to traverse along the effective length of the roll. The cleaning effect of brushes, fleece rollers and fleece cushions is, however, limited, and in many cases is unsatisfactory.
A high pressure liquid cleaning of the rolls has been proposed in which a wide mouth nozzle for each roll provides a water spray to clean the surface of the roll. With this system, the position of the cleaning nozzle cannot be varied. A nozzle system which is capable of moving along the roll is also known but this earlier system is satisfactory only for rolls of constant diameter with constant strip speeds. The wide mouth nozzle is not versatile in that especially dressing roller stands must have rolls of different roll diameter from time to time for processing different steel alloys and for different products made by the system. For example, a working roll may have a diameter of 450 mm when new and 400 mm when ground down for use with hard materials but 650 mm when new and 600 mm when ground down for softer materials. The backing rolls in this case may have diameters of 900 mm when new and 820 mm when ground down. The cleaning unit in the case of a broad slit nozzle is only properly positioned for one roll diameter and, for example if the roll is ground down, the cleaning effect is largely lost.
Similar problems arise with the rolls and roll stands used in extrusion casting and strip casting apparatus and in strip mills using continuous casting, as well as with the rolls used in rolling mill and strip processing lines.
In addition, in for example an aluminum process line problems arise with aluminum oxide which is more or less adherent to the strip surface and which can adhere to the rolls for the respective line, especially the stretching rolls of a processing line and can lead to growth of the deposit on the roll and the generation of surface defects.
OBJECTS OF THE INVENTION
It is, therefore, the principal object of the present invention to provide a method of cleaning rolls for strip casting lines, strip rolling lines and/or strip processing lines and especially dressing stand rolls or sizing rolls or post rolling treatment rolls, particularly dressing rolls, whereby an especially efficient cleaning is maintained for rolls of different diameters, for the processing of different strip materials and in the case of different strip speeds.
Another object of the invention is to provide a method of operating a strip line which involves the cleaning thereof whereby drawbacks of earlier systems are eliminated.
It is also an object of the invention to provide an apparatus which has been found to be especially suitable for carrying out the cleaning process and which can operate in a simple and reliable manner.
SUMMARY OF THE INVENTION
These objects and others which will become apparent hereinafter are attained, in accordance with the invention by adjusting and controlling the distance between the cleaning nozzle and the roll surface. The adjustment and control of the spacing allows a highly accurate establishment and maintenance of a given spacing so that the effect of changes in the distance upon changing roll diameter can be eliminated. The invention therefore operates with a cleaning nozzle of variable spacing with which it is relatively simple to match the cleaning nozzle spacing to various roll diameters. The consequence is an optimal cleaning effectiveness. This is the case when, according to another feature of the invention, the traversing speed for the back and forth movement of the cleaning nozzle is set in dependence upon the strip speed and/or the strip material and/or the strip surface. An especially efficient cleaning effect is obtained in this matter.
According to another feature of this invention, the spacing between the roll and the nozzle is maintained constant during the back and forth movements and hence from one repetition to the next and in spite of variations in the roll diameter. The distance or spacing should be smaller than 100 mm for greatest high pressure clean efficiency.
According to a feature of the invention the metal strip before contacting the roll can be subjected on its upper side and/or on its lower side to a hydromechanical cleaning with a cleaning liquid discharged from one or more jets. The cleaning of the roll can thus be greatly simplified and in many cases made superfluous.
According to another feature of the invention the jet is trained against the strip as it overshoots a roll. This has been found to improve the cleaning efficiency. The liquid jets used for cleaning the roll and/or the strip should be supplied with the cleaning liquid at at least 100 bar.
The cleaning liquid is preferably desalinated or salt free water and corrosion limiting additives can be added to the cleaning liquid.
The method of operating a strip line with a roll to be cleaned can comprise:
(a) training a jet of a cleaning liquid from at least one nozzle against a surface of the roll to be cleaned;
(b) displacing the nozzle back and forth along the roll while rotating the roll and the jet impacts the surface; and
(c) controlling a spacing between the nozzle and the surface and regulating the spacing during the back and forth displacement of the nozzle to maintain a predetermined value of the spacing.
The apparatus, in turn, can comprise:
at least one nozzle training a jet of a cleaning liquid against a surface of the roll to be cleaned;
means for displacing the nozzle back and forth along the roll while rotating the roll and while the jet impacts the surface; and
means for controlling a spacing between the nozzle and the surface and regulating the spacing during the back and forth displacement of the nozzle to maintain a predetermined value of the spacing.
With the apparatus, the roll or roller of a stri
Biele Peter
Nentwich Wolfgang
Noe Andreas
Noe Rolf
Schönenberg Rudolf
BWG Bergwerk-und Walzwerk-Maschinenbau GmbH
Dubno Herbert
El-Arini Zeinab
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