TECHNICAL FIELD

The invention relates generally to the field of degreasing metal sheets in a production line.

In the metal sheet or plate working industries, metal sheets will often need degreasing between process steps in order to remove greasy substances and dust or particulate matters in order to maintain a proper performance of the working machines and tools in following steps.

BACKGROUND ART

The known solutions usually require a fair amount of space to achieve a proper cleaning while the sheets are in a continuous movement along the production line. Moreover, the cleaning operation and the cleaning liquid cause dirt to spread on the sheets to be cleaned and to the surroundings, because it is hard to shield off the zone of operation.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide a compact and better encased degreasing zone, so that a clean sheet can be delivered to the next process step in the production line.

A method according to the invention is provided for use in a production line with a need for degreasing a sheet before a next process step, said method comprising the steps of:

(a) providing a metal sheet having a greasy coating to be removed before further processing,

(b) delivering said metal sheet to the entry end of a degreasing apparatus, by entering an end of such sheet into a first roller arrangement comprising a plurality of rollers, of which the surface of a driven transport roller provides enough friction to not slide on the metal sheet, while advancing said sheet in the production direction and in between said rollers in the roller arrangement,

(c) forcing a pressing roller towards a first surface of the sheet, while remaining rollers of such arrangement are actively or passively kept in fixed positions relative to the sheet, providing a first transverse liquid-sealing contact line between the pressing roller and the sheet, (d) brushing the advancing sheet by a brush arrangement in a movement transverse to the production direction; a degreasing liquid being added to the brushing zone for dissolving the greasy coating on the sheet while brushing is performed,

(e) then passing the cleaned sheet through a second roller arrangement similar to said first roller arrangement and working in the same manner and providing a second transverse liquid-sealing contact line between the roller and the sheet, and

(f) delivering the cleaned sheet to a next process stage in the production line.

Said method provides a well-defined degreasing zone bounded by first and second liquid-sealing contact lines keeping the degreasing liquid inside said zone and not running further on the surface of the sheet being degreased.

In a preferred embodiment of the invention, the sheet entering the first roller arrangement is supported by a support roller of the first arrangement and then advanced into the nib of a pressing roller and a counter roller of same arrangement, such that in step c) a further first transverse liquid-sealing contact line is provided on a second surface of the sheet, when the counter roller and the sheet are in adjacent position, i.e. thereby establishing first sealing barriers across and on both sides of the sheet.

In step e) a further second transverse liquid-sealing contact line is provided on a second surface of the sheet, when the counter roller of the second arrangement and the sheet are in adjacent position, i.e. thereby establishing second sealing barriers across and on both sides of the sheet.

The greasy coating on the sheets would most often be rolling or forming lubricants and corrosion inhibitors The degreasing liquid would be a solution, e g. an alkaline solution able to dissolve said coating. Alkaline solutions are to be preferred over chemicals like trichloroethylene (TCE), tetrachloroethylene (PERC) and trichloroethane, which have been deemed hazardous to the environment. The alkaline solution is preferably maintained at a temperature of 40-60 ⁰ C, preferably 45°C.

In general, degreasing liquids and dissolved coatings will present a surface tension which has to be broken, and the solution chosen is very often mechanical force applied to the surface, preferably by means of brush wheels or forceful flushing equipment. According to the invention, the effect of the brushing is improved over rotary brush cups or roller brushes by implementing a transverse brush belt, which applies the mechanical brushing in combination with moving the liquid sideways away from the zone and the contact lines. Such brush belts could be applied on both sides of the sheet, if required. This results in much less liquid having to be squeezed away from the sheets and removed from their surfaces, which also means that the sheets get clean and dry over a very short distance in the production direction

The liquid could be applied to the brushing area(s) by simple means, e.g. a perforated pipe or conduit alongside a brush belt.

The brush belts on each side of the sheets may in a preferred embodiment brush the sheets in opposite directions, which stabilizes the sheets laterally on the support.

In yet another embodiment, step f) is preceded by the sheet being advanced from the second set of rollers to an optional third set of rollers similar to said second set of rollers, adapted to squeeze off any remaining fluid or dirt from the sheet surfaces.

The spent degreasing liquid will usually be collected in collection means, e g. a chute and a tank, below the degreasing zone, and discharged. However, in order to free space in the production line, a remote collection/recirculation system serving several installations could be provided.

If needed, the method could be extended to drying the edges of the sheets with airknife means after the grease has been squeezed off.

According to the invention also an apparatus adapted to the method for degreasing metal sheets is provided, said apparatus comprising:

- a support structure defining the path for sheets advancing through the apparatus

- an input end having a first roller arrangement to receive each sheet to be degreased

- an output end having at least one roller arrangement to receive each sheet as degreased

- a brush arrangement working in an angle to the direction of the production line.

- a liquid supply arrangement to supply degreasing liquid to the degreasing zone between a first and a second roller arrangement

- a collection means for collecting spent degreasing liquid, located below the degreasing zone

- drive means for the roller arrangements.

The support structure advantageously comprises a plurality of rotatable rods aligned with supporting rollers of the roller arrangements in such a manner that a straight support plane is defined on top of said rods and said rollers, serving to support sheets being advanced through the apparatus.

The rotatable rods and/or support rollers can be driven by drive means providing advancement of the sheets.

The roller arrangement may advantageously comprise a pressing roller provided with a forcing means, e.g a hydraulic or pneumatic cylinder or a spring to force the roller against a sheet to be cleaned, and which again is forced against a passive or active support or counter roller of the arrangement.

Preferably, the position of the pressing roller of each roller arrangement is adjustable relative to the adjacent surface of the sheet in order to provide an adequate squeezing force to remove grease and liquid from said sheet surface.

In a further embodiment of the invention, a wiper blade may support or replace at least one of the rollers of a roller arrangement to hinder fluid or dirt on a sheet to flow past the sealing contact lines.

Moreover, any of the rollers may be driven by drive means to convey sheets in the production direction.

For proper conveyance of sheets, the rollers are preferably made of an elastic and durable oil-resistant material, e.g. rubber, silicone, etc. Said rubber showing preferably a Shore 60 hardness.

In a preferred embodiment, the brushing means are arranged with the brushing direction in an angle of 45-90° relative to the production direction, advantageously 75-90°, preferably 90°.

The apparatus having the degreasing zone as bounded by the first and the second roller arrangement, are preferably substantially enclosed in a housing, said housing being provided with a collection chute and drain outlet for the spent liquid. Said collection could also be performed at a position remote from the production line. As a result, the production line can be kept clean in the area around the apparatus, and the heating and/or recirculation of refreshed liquid and the final storage of the spent liquid could be handled by remote means possibly supplying several installations.

In situations with sheets having very dirty surfaces to be cleaned, it may be advantageous to arrange further squeezing roller arrangements after the first and second ones or several apparatuses according to the invention after each other resulting in the cleaning operation lasting longer and thus clean sheets are guaranteed.

The special advantage achieved with a degreasing apparatus according to the invention is that the distance between the first and the final roller arrangements can be minimized to as little as the width of the brush belt, which again allows for sheets of very small dimensions to be degreased. Moreover, the compact construction also makes it very convenient for inline installation in a production line, in any position or stage where degreasing may become a requirement.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed part of the present description, a preferred embodiment of the invention will be described in more detail and with reference to the drawing, wherein

Fig.1 is a side view of a degreasing apparatus according to the invention, and Fig. 2 is a perspective view of said apparatus enclosed in a housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Fig,1 presents a preferred embodiment of the invention stripped down to the essential features thereof.

Sheets 1 are advanced in the production direction F from left to right as viewed in the drawing. The sheets are delivered to the entry end of a degreasing apparatus according to the invention. A support structure 2 defining the path for sheets advancing through the apparatus comprises a plurality of rotatable rods 3 aligned with supporting rollers 4, 5 of the roller arrangements in such a manner that a straight support plane is defined by the tops of said rods and said rollers, serving to support sheets 1 being advanced through the apparatus. A drive means (not shown) is provided for rotating at least the support roller being aligned with a pressing roller on the opposite side of the sheet to be cleaned

The first set of rollers 4-6 comprises at least one support or counter roller 4,5 preferably in a fixed position relative to sheet 1, and one pressing roller 6. Pressing roller 6 is subjected to forcing means, e.g. a hydraulic or pneumatic cylinder or a spring (not shown), to force the roller 6 against a sheet 1 to be cleaned, which again is biased against a counter roller 4 of the arrangement.

Preferably, the position of the pressing roller 6 of each roller arrangement is adjustable (double-arrow V) relative to the adjacent surface of the sheet 1 in order to provide an adequate squeezing force, and thereby a first liquid-sealant connection

line perpendicular to the direction F, to not allow passage of grease and liquid from a traversing surface of a sheet irrespective of the thickness thereof

The sheet moves through the nip of the first set of rollers 4-6 while being supported on the support structure 2 and is traversing the cleaning or degreasing zone Z In the zone Z, liquid application means 8 in the form of a perforated liquid pipe or conduit is aligned with brushing means 7 in the form of a brush belt operating in an angle, preferably 90°, to the production direction F ₁ to release the liquid and the grease from the surface of the sheet and to brush the spent liquid in a transverse direction off the sheet 1.

In the most preferred embodiment of the invention, a similar installation of a liquid pipe 8 and a brush belt 7 on the opposite side of the sheet is provided in order to clean both sides of the sheet in a simultaneous operation without turning the sheet.

The liquid applied to the surface of the sheet would spread out on the full length of the sheet 1 if not for a further second set of rollers 5 ¹ , 6' that creates a second liquid- sealant connecting line or barrier at the intersection of rollers 5\ 6' and a sheet 1, said line denoting the second barrier of the zone Z, said first set of rollers 4-6 providing a similar first barrier. The length of zone Z along the production direction F can be down to about 300 mm and the width of the rollers of the embodiment shown is about 1300 mm having a diameter of about 60 mm. The rate of sheet advancement is in the order of 1 m/min.

Optional further roller arrangements could be provided downstream of the zone Z, so that even very small occurrences of liquid, which may be passing through the second set of rollers, would be caught by the further set of rollers and squeezed away

The sheets being cleaned in a degreasing apparatus like this are required to have substantially equal thicknesses for the rollers to establish uninterrupted connecting lines across the sheet However, several sheets in various shapes can be cleaned alongside each other on the support structure 2.

In a semi-automatic embodiment, the sheets are moved manually into the nib of rollers 5,6, and the rotatable rods 3 of the support structure 2 are not driven. However, it is preferred to have the utmost benefit from the invention by automated feeding of sheets 1 by means of motor-driven rods 3 and rollers 4, 5, 5'.

The degreasing apparatus should preferably be enclosed in a housing 10, said housing being provided with a collection chute 11 and a drain outlet 12 preferably leading to a tank 13 for storage or recycling/recirculation of spent liquid; said tank would preferably be a remote installation serving one or more apparatuses. Further the apparatus would preferably be provided with a hood 15 to vent hot air from the warm liquid.

Moreover, airknife means 14 could be provided for drying vertical surfaces of a sheet if liquid should remain thereon.

The degreasing liquid is preferably heated to an appropriate temperature at a remote place and then supplied via conduits 8 to the degreasing zone. Hereby the space demand in the production line can be kept to a minimum, and several apparatuses can receive and deliver liquid from/to a common supply installation.