Brushing – scrubbing – and general cleaning – Machines – Brushing
Reexamination Certificate
1998-04-06
2001-04-17
Spisich, Mark (Department: 1744)
Brushing, scrubbing, and general cleaning
Machines
Brushing
C015S088300, C134S06400P, C134S12200P
Reexamination Certificate
active
06216304
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method and an apparatus for cleaning a strip, and more particularly, to a method and an apparatus for cleaning a metal strip by an electrolytically cleaning technique in the steel industry.
DESCRIPTION OF PRIOR ART
Methods for electrolytically cleaning a strip have been conventionally carried out in the iron-manufacturing industry by passing a metal strip between opposed positive and negative plates in an aqueous solution of alkali held in an electrolytic cell. These conventional methods, however, entail the following problems.
Usually a strip passing between the positive and negative plates moves zigzag in the direction of strip thickness. Consequently, the strip may contact or collide with the positive or negative plates due to the zigzag movement. To avoid the contact or collision, the positive and negative plates should be relatively widely spaced away from the strip passing through the alkali solution, or namely the plates should be arranged with a sufficient space. In the arrangement of plates widely spaced away, a large current should be applied to the plates so as to electrolytically clean the strip. Conventionally a current at about 4,000 to about 10,000 amps. has been applied to the plates. If a large current is applied, a serious problem of electric corrosion is raised due to stray current.
If a small current is applied to the plates to overcome the problem of electric corrosion resulting from stray current by application of a large current, a low current density results, leading to a reduced electrolytically cleaning effect.
According to the conventional techniques for electrolytically cleaning a strip, the plates are disposed with a space of about 1.5 m at 10 to 30 locations in the travelling direction of the strip in a strip-cleaning line which is operated at a running speed of about 500 to about 700 m/min.
In this mode of electrolytically cleaning operation, an alkali aqueous solution flows out from an electrolytic cell and can be returned after regeneration or after replenishment with a new alkali aqueous solution outside the electrolytic cell. Even in this case, a large amount of alkali aqueous solution (about 20 to about 30 m
3
) should be held in the electrolytic cell. This denotes that only a low energy effect is produced in the electrolytically cleaning operation, and that a large-scale electrolytically cleaning equipment is required which incurs a high running cost and a high maintenance cost.
Since the conventional electrolytically cleaning system is of immersion type, the oil deposited on the strip is released into the alkaline bath and unavoidably re-deposits on the strip passing through the alkaline bath, resulting in reduced degreasing or cleaning efficiency in addition to the foregoing deficiency.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the foregoing prior art problems. Stated more specifically, the object of the invention is to provide a method and an apparatus for cleaning a strip by an electrolytically cleaning technique with the following advantages:
(1) a high electrolytically cleaning efficiency can be achieved by application of a small current;
(2) it is possible to resolve the problem posed by the conventional techniques due to stray current by application of a large current,
(3) a high energy effect can be produced by the electrolytically cleaning operation,
(4) a significantly small-size electrolytically cleaning equipment compared with conventional one can be provided,
(5) the running cost in the electrolytically cleaning operation can be decreased far below the costs heretofore involved,
(6) the maintenance cost in the electrolytically cleaning operation can be lowered, and
(7) the oil released from the strip by the electrolytically cleaning operation is prevented from redepositing on the strip.
According to the present invention, there is provided a method for cleaning a strip, the method comprising the steps of:
(i) electrolytically cleaning a strip to be cleaned by passing the strip between opposed nozzles for ejecting an alkali aqueous solution over the strip, one of the nozzles being a positive electrode and the other being a negative electrode, and a voltage being applied to the nozzles, and
(ii) brushing, in a spray of cleaning water, the strip with a brush roll or brush rolls disposed at a position(s) adjacent to the nozzles of the electrolytically cleaning step (i) downstream of the nozzles in the travelling direction of the strip, the strip being subjected at least once to the procedures in the steps (i) and (ii).
According to the present invention, there is also provided an apparatus for cleaning a strip, the apparatus comprising at least one cleaning unit comprising:
(a) opposed nozzles for ejecting an alkali aqueous solution over the spray between which the strip to be cleaned is passed, one of the nozzles being a positive electrode and the other being a negative electrode, and
(b) a brush roll or brush rolls for brushing the strip in a spray of cleaning water, the brush roll or rolls being disposed at a position(s) adjacent to the nozzles downstream thereof in the travelling direction of the strip.
According to the present invention, one of the opposed nozzles for ejecting an alkali aqueous solution over the strip is the anode and the other is the cathode. The strip to be treated is passed between the opposed nozzles, whereby it is electrolytically cleaned.
In this case, when moving zigzag even in a narrow space between the nozzles, the strip neither contacts nor collides with the nozzles for the following reasons.
The solution is forced out from the nozzles at a pressure which is inversely proportional to the distance between the nozzle and the strip. Consequently, the strip coming closer to the nozzles is exposed to a higher pressure according to the distance between the nozzle and the strip. The nearer the strip moves, the more strongly it is prevented from moving closer by a higher pressure.
According to the invention, when the alkali aqueous solution is supplied, at a pressure of 1 kg/cm
2
, to the nozzles spaced by 10 mm from the strip, the strip can pass between the nozzles without contact nor collision with the nozzles serving as the electrodes.
In accordance with the present invention, the opposed electrodes can be arranged with such a short space that a high electrolytically cleaning efficiency can be achieved by application of a small current which overcomes the prior art problem of electric corrosion owing to stray current by application of a large current.
According to the present invention, the current density per input unit of power can be much more increased than in the prior art, whereby a strip can be electrolytically cleaned with a noticeably high efficiency.
For example, the desired electrolytically cleaning effect can be produced using nozzles, 7 to 8 mm in size in the strip-travelling direction, in the strip-cleaning line which is operated at the above-mentioned running speed. In this embodiment, a large amount of electrolyte need not be held in the electrolytic cell so that a high energy effect can be achieved by the electrolytically cleaning operation.
Stated more specifically, the electrolytically cleaning effect can be achieved as contemplated by application of power of 10 amps. at 7-8 volts using a single cleaning unit with nozzles of the above-mentioned size arranged at a distance of 10 mm between the nozzle and the strip in a strip-cleaning line which is operated at the above running speed. In contrast, the conventional techniques require power of 4,000 to 10,000 amps. at 20 volts in a strip-cleaning line which is operated at the same running speed.
According to the invention, a significantly smaller size electrolytically cleaning equipment can be provided, and the electrolytically cleaning equipment can be operated at a far lower running cost and can be maintained at a lower cost, than in the prior art.
The oil deposited on the strip can be removed from the strip in a short time by the above-menti
Hotani Co., Ltd.
Knobbe Martens Olson & Bear LLP
Spisich Mark
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