DEVICE FOR REMOVING A LIQUID OR SOLID PARTICLES FROM A FLAT METALLIC PRODUCT Field of the invention

The present invention relates to a device for removing a liquid or solid particles from flat metallic surfaces, particularly used specifically for removing oil emulsion and/or pure oil and/or dust and/or scale and for drying and cleaning metallic strips during rolling. State of the art An oil emulsion, or pure oil, is commonly used in strip rolling mills to lubricate the working zone of the rollers and ensure adequate cooling.

The high speeds at which the strip moves, up to 1500 m/min and over, and consequently the high rotation speeds of the mill stand rollers determine a dispersion of atomised emulsion, for example, which very often goes beyond all the drying devices normally used and is disadvantageously deposited on the rolled product immediately prior to winding.

When the emulsion remains on the strip and the latter is then wound, a chemical reaction is produced which generates a visible stain on the strip itself which is detrimental to quality, so that the segment of strip concerned by the stain must be rejected for the subsequent machining processes. The solution commonly used in the state of the art contemplates using a series of rows of nozzles fed by high-pressure compressed air, 5 bars and over, possibly followed by an air blade fed by a dedicated fan to create a flat jet on the strip. The used nozzles may be of various types, with a flat or cylindrical jet, single jet or multiple jet, ejector effect nozzles, etc. The first rows of nozzles serve the purpose of stopping the feed of the most thick part of the emulsion, while the last rows and the air blade serve the purpose of performing the final drying of the strip. However, the great dispersion and the turbulent atomisation of the emulsion in drips, produced by all the known devices, makes this configuration never fully efficient, despite the global use of high flow rates of compressed air.

It is thus felt the need to make a strip drying and cleaning device which allows to overcome the aforesaid drawbacks. Summary of the invention

It is the primary object of the present invention to make a device for removing a liquid or solid particles from metallic strips which allows a perfect and uniform removal of the oil emulsion and/or pure oil and/or dusts and/or scale and the total drying and cleaning of the strip prior to its winding, eliminating the quality problems consequent to the staying of the liquid or solid particles on the finished product. The present invention thus suggests to reach the abovementioned object by making a device for removing a liquid or solid particles from a flat metallic product moving along a longitudinal path, comprising

- feeding means of a jet of gas along the width of said path so as to generate reciprocally opposite first flows of gas along the path and whereby remove the liquid or solid particles previously deposited or formed on the metallic product;

- suction means;

- a casing having an appropriate profile such to incorporate said feeding means in a volume, said casing having first ends arranged at predetermined distances from said path so as to make the external environment communicate with said volume, and such to define throat sections communicating with the suction means, wherein said suction means are adapted to produce a vacuum within the volume such to generate second air flows from the external environment towards the volume which oppose the first flows allowing the suction of all the liquid or the solid particles.

The device, object of the present invention, may be advantageously applied in any process in which it is required to continuously remove a liquid previously deposited on a surface in translating motion, or in which it is required to continuously remove dust or scale previously deposited or formed on said surface. The operation of the device provides a flat air jet or compressed air blade or other suitable gas, such as for example nitrogen in the case of special processes, generated by a nozzle which, seen in vertical section, is angled with respect to the surface of the strip and is mainly oriented in opposite direction with respect to that of movement of the strip. The jet produces an intense viscous shearing force action on the strip which represents both the main mechanism of atomisation and removal of the liquid film from the surface of the strip and the main mechanism of lifting and removal of solid particles.

The jet is locally evacuated by an integrated suction system, arranged on both sides with respect to the direction of movement of the strip, in order to ensure that the liquid atomised by the jet or the dust or scale lifted by the jet is moved away from the zone of the product and cannot fall back on it. The viscous shearing action of the jet on the strip is from 7 to 25 times greater than that of all the other nozzles installed in the known devices.

All the air or gas introduced by the nozzle is sucked by the integrated suction/evacuation system and with it air from outside of the device is sucked, the latter constituting the real sealing safety with respect to the atomised liquid or the dust lifted.

No significant leakage of gas contaminated by the liquid or dust appears outside of the system, which is therefore capable of working in safety.

Possibly, rows of nozzles arranged near the working rollers may cooperate with the device of the invention. The dependent claims describe preferred embodiments of the invention.

Brief description of the drawings

Further features and advantages of the present invention will be more apparent in the light of the detailed description of preferred, but not exclusive, embodiments of a device for removing a liquid or solid particles from metallic strips, illustrated by way of non-limitative example, with the help of the accompanying drawings, in which:

Fig. 1 shows a perspective view of a device according to the invention;

Fig. 2 shows a cross-section view of a first embodiment of the device in Fig. 1 ;

Fig. 2a shows an enlarged detail of part of the section in Fig. 2; Fig. 3 shows a perspective view of a variant of the device of the invention;

Fig. 4 shows a section of the device schematically illustrating the pattern of the various gaseous flows inside it;

Fig. 5 shows a diagram of the device of the invention;

Fig. 6 shows a diagram of a configuration of devices according to the invention; Fig. 7 shows a cross-section view of a second embodiment of the device of the invention.

Detailed description of preferred embodiments of the invention

With reference to the Figures, a device for removing a liquid or solid particles from

metallic strips, globally indicated by reference numeral 1 , is shown comprising:

- feeding means of an air jet or blade on the strip, moving along a longitudinal path, so as to remove the oil emulsion or other liquid previously deposited on the strip; - air suction means;

- a bell incorporating said feeding means and communicating with said suction means so as to allow the suction of the air containing the removed atomised oil emulsion.

The feeding means comprise a feeding or delivery manifold 2 provided with a delivery flange 4, arranged on one side of the device, and a distribution system 3,

3' of the delivery flow arranged inside along the longitudinal extension of the device in order to ensure an uniform distribution of the flow rate along the length of the system.

Feeding manifold 2 is provided in its part closest to the direction of movement of strip 6 with two plates 14, 14' appropriately machined and joined so as to define a delivery nozzle or slot 5 of an air jet or air blade. The jet will impact on strip 6 so as to produce flows in both directions along it.

In a first advantageous configuration, illustrated in Fig. 2, the distribution system 3 is arranged in the lower part of manifold 2 in direct contact and communication with said delivery nozzle or slot 5.

Such distribution system 3, preferably tubular and having a T-shaped section, is provided on its sides either with a series of holes 13 or with a series of slots or with one continuous slot.

A flow of air enters feeding manifold 2 through delivery flange 4, then enters in the distribution system 3 through holes or slots 13 where the flow rate and the pressure are equalized, and a jet escapes by nozzle 5.

In a second advantageous configuration, illustrated in Fig. 7, the distribution system 3' is substantially arranged in the central part of manifold 2 without any direct communication with the delivery nozzle or slot 5. Such distribution system 3', preferably tubular and having a circular section, is provided in its upper part either with a series of holes 13' or with a series of slots or with one continuous slot. These holes or slots 13' may be placed also or alternatively in other parts of the circular section of the system 3'.

Preferably, distribution system 3' consists of a pipe directly connected to the delivery flange 4. A flow of air enters pipe 3', where the flow rate and the pressure are equalized, through delivery flange 4; enters feeding manifold 2 through holes or slots 13' and a jet escapes by nozzle 5 provided on the lower part of manifold 2. The air suction means instead comprise suction manifolds 10 provided at the respective ends with suction flanges 1 1 .

Advantageously, there is provided an external tubular bell 7 which incorporates feeding manifold 2. First ends 15, 15' of bell 7 are arranged at a predetermined distance d ₂ from the surface of the strip; second ends 16, 16' of bell 7 are instead appropriately shaped so as to define communication zones between internal volume 17, provided between bell 7 and feeding manifold 2, and suction manifolds 10. Such communication zones have a configuration providing respective throat sections 8 and outlet sections 9 for the outlet in suction manifolds 10. The first ends 15, 15' may also be asymmetric with respect to axis Y. For example, end 15 which encounters the strip first in its movement may have a different shape than end 15' so as to define a respective internal volume greater than that defined by end 15'. Also distance d ₂ from the surface of the strip may be different for the two ends 15, 15'. Through the four suction flanges 1 1 , at least one dedicated fan 18 arranged in suction draws flow from suction manifolds 10 and through outlet sections 9 forms a vacuum in the internal volume resulting between external tubular bell 7 and feeding manifold 2.

By effect of this vacuum a great air flow rate is advantageously drawn from the external environment through the free section between external tubular bell 7 and strip 6. With reference to Fig. 4, for example, air flows coming from the outside 21 , 23 are produced opposite to flows 22, 22' produced by the air jet on strip 6. Such flows 23, 21 are sufficiently intense to prevent flows 22, 22' from being let out from bell 7. Due to this effect, both the flows produced on the strip by the jet and those sucked from the external environment deviate within bell 7 generating resulting flows towards throat sections 8. Advantageously, the external part of feeding manifold 2 performs the important function of supporting the rotation of the resulting flows towards throat sections 8.

The entire suction system of the device of the invention has a uniform section along its entire extension.

In a particular embodiment, the throat sections have an appropriate convergent- divergent configuration. The main function of throat sections 8 is to ensure suction uniformity on the entire width of the strip.

The widening of the passage section which is obtained from throat section 8 to outlet section 9 in suction manifold 10 is appropriately calibrated so as to ensure that the resulting flow in section 9 is uniformly directed in a direction essentially orthogonal to the direction of movement of the strip, specifically upwards in the case of the configuration in Fig. 2 or Fig. 7 and downwards in the case of a device arranged symmetrically to that of Fig. 2 or Fig. 7 with respect to the plane identified by the strip.

In this way presence of recirculation or zones not passed through by the flow which could cause the fall back or accumulation inside the bell 7, and thus on strip 6, of the atomised oil emulsion carried by the air is avoided.

The upper section of external tubular bell 7, which defines along with central partition 12 the outlet sections 9, is appropriately dimensioned so as to be inserted within suction manifolds 10. The importance of this contrivance resides in that the flow of air sucked in sections closer to the median longitudinal line of the strip are made to turn within manifold 10 and forced to progressively occupy the zone closest to the respective axis, leaving free and not disturbing the flow of air which is sucked in the more external sections with respect to the median longitudinal line of the strip. The result is that the suction system integrated in the device of the invention is capable of sucking the air with extreme uniformity and on the entire width of the strip.

The device of the invention may be made almost entirely using stainless steel pipes, for example DIN 2462. In any case, it may be further made with different methods and shapes: for example external suction bell 7 may have a polygonal section.

A first advantageous embodiment provides, starting from the section shown in Fig.

2, a straight development of the device.

In its two preferred embodiments, delivery flow distribution system 3, 3' is, for

example, provided with two series of slots 13, 13', each series arranged symmetrically with respect to axis Y and made along its entire longitudinal extension. Each of these slots 13,13', having a longitudinal extension and a substantially rectangular shape, has a transversal size of approximately 1 -7 mm. The opening of nozzle 5 is approximately 0,5-3 mm. The direction of the jet is angled by approximately 40-85°, preferably 60°, with respect to the surface of strip 6.

Distance di of delivery nozzle 5 from the movement plane of strip 6 is equal to approximately 4-8 mm, whereas distance d ₂ between the first ends 15, 15' of bell 7 and said plane or path is equal to approximately 6-10 mm.

Feeding manifold 2 and suction manifolds 10 are tubular, preferably but not necessarily circular.

The pneumatic dimensioning of the device provides the use of fans and a feeding of air at ambient temperature. The feeding pressure of delivery nozzle 5 is approximately 200-400 mbar. A delivery fan 50 of small or medium dimensions is further capable of ensuring a higher head, thus widely availing of the load loss needed by flow delivery distribution system 3 to ensure the uniformity of the jet along the width of the strip. The suction pressure at flanges 1 1 is approximately 100-400 mbar. An extraction fan 18 of medium dimensions is capable of ensuring these performances.

In suction phase, extraction fan 18 is connected to both sides, and thus to all four flanges 1 1 , while in feeding phase, delivery fan 50 is connected only to one side of flange 4. The straight shaped device defines a longitudinal axis and may be installed with said longitudinal axis X orthogonal with respect to the direction of movement of strip 6, as shown in Fig. 5, or slightly inclined.

A second advantageous embodiment of the device of the invention provides instead a V-shape which encloses an angle, for example, of 120° with an either continuous or broken line development as that shown in Fig. 3. This second solution exploits all the same operating principles already described, but offers an additional safety if the quantity of oil emulsion to be eliminated is very high. In this case, indeed, the V-shaped device is capable of preventively moving away a greater mass of liquid or oil emulsion towards the sides of the

rolled product and of drying inside the remaining thinner oil emulsion film. The V-shape, indeed, if the mass of oil emulsion is not a thin film, allows to move most of it away sideways and make it fall from the edges of the strip. The jet of air from the nozzle, indeed, forms a veritable barrier and the oil emulsion, pushed from the strip, tends to slide sideways towards the edges. The mass of oil emulsion remaining on the strip, in form a thin film, is instead atomised within the bell and removed by means of the suction system described above. Advantageously, the device may also work at distances di and d ₂ from the strip 6 different than those previously indicated, for example greater distances comprised in the range from 8 to 50 mm for di and in the range from 10 to 50 mm for d ₂ . In this case, the device may be connected both in delivery and in suction to higher performance air machines, such as compressors, without any limitation. The delivery and suction pressures may be in these cases from 400 to 1500 mbar and over. The opening of nozzle 5 may also be higher, up to a value of approximately 10 mm.

The device may be fixingly mounted with respect to the movement path of the strip or may be provided with degrees of freedom. In this second case, it may be distanced from said path to allow specific process steps, such as for example the insertion of the first segment of the strip, or may be continuously adjusted, for example to manage the distance of the device from the strip or to follow with transversal movements the exact positioning of the strip.

Both the feeding unit and the suction unit may be connected to both ends of the device or to one end only. Specifically, in the case of suction, it is preferable to connect extraction fan 18 to both sides, thus to all four flanges 1 1 , but if layout issues make this configuration not advisable, the device is capable of ensuring high performances also with the connection to only one side. Advantageously, in all embodiments, a heater 19 may be provided between delivery fan 50 and device 1 with the function of increasing the air temperature, for example up to temperatures from 100 to 400°C. In this case, the hot air allows to start an evaporation mechanism of the oil emulsion which is added to the atomisation induced by the viscous shearing. A heater having a power appropriate to the enthalpy of the air to be fed must be used in the delivery branch. In the system design, moreover, specifically relevant components and accessories

may be provided, such as for example a filter 31 for the delivery air in order to avoid to carry impurities onto the strip by means of the jet. It is also possible to provide on the suction branch of the device a filter 32 which removes the oil emulsion from the sucked air flow rate and avoids therefore the introduction into the environment.

In addition to the management of the rotation rate of delivery fan 50 and extraction or suction fan 18, from the point of view of adjustment, the suction system may be split, with respect to the two ends of the device, by means of an appropriate set of valves 20. Globally, the adjustment of the device may allow the control and the minimisation of the onside powers and flow rates in function of the real conditions of the strip, considering the degree of oil emulsion contamination , the speed, etc. The device of the invention may be installed either on only one side of the strip, for example on the upper side, or on both sides. In this second case, the two devices may either be positioned symmetrically with respect to the strip, or staggered, or arranged at different distances from the strip. Advantageously, in the case in which the drying and cleaning process occurs on different strip widths, the width of the device may be adjusted according to the width of the strip. A first variant of the device of the invention may be provided, specifically the suction section, split into compartments, with the possibility of progressively activating external sections in parallel proportionally to the width of the strip. A second variant provides, instead, the lateral insertion of mobile plates capable of simulating the presence of a wider strip. These two solutions advantageously allow to maintain optimal fluid-dynamic conditions regardless of the width of the strip to be dried and cleaned. Specifically, by operating on considerably narrower strips, the portions of the device which remain outside the strip may become significant and the suction may tend to occur preferably in correspondence of these portions to the detriment of the suction effect in the central zone of the strip. As a consequence, the removal of the oil emulsion from the median region of the strip may be insufficient. The contrivances described above eliminate this drawback. A further advantage is represented by the fact that it is possible to provide devices

of the invention mounted on both sides or surfaces of the strip, so that the net resultant of the attractive forces is averagely balanced, and positioned in proximity of strip mobility constraining means, for example a roller 20 about which the strip is slightly wound. This advantageous configuration, schematically shown in Fig. 6, allows that possible vibrations triggered by the instability of the air flows in each device, due for example to the even minimal instability of operation of the delivery fan, have a minimum amplitude, limited by the proximity of the mechanical constraint. This optimal installation of the device minimises the possibility of the strip to start vibrating under the effect of the attractive force of the suction system, due to the high vacuum which is established within external tubular bell 7. A high vacuum could indeed determine an attraction of the strip of intensity up to 100 kgf and over. For low strip thickness and/or low pulling forces applied to the strip, the strip could come into contact with the device, especially if this is very close. Thanks to the introduction of constraint means, such as for example rollers, which prevent an excessive approach of the strip to the device, such drawback is avoided in a simple manner.

Similarly, this problem may be considerably limited in the case of arrangement of the device of the invention on only one side of the strip. By positioning an appropriate roller on the opposite side of the device, a zone of slight winding of the strip about said roller is created. In this case, the pulling force applied to the strip produces a component opposite to the force of attraction of the device which may be capable of contrasting it and avoiding the approach of the strip. According to an advantageous variant, the vacuum on the strip is continuously detected by means of appropriate measurers and the device of the invention is, by means of appropriate movement means, automatically moved to or away from the surface of the strip so as to vary the relative gap and return the suction pressure values to the predetermined values needed during the operative step. In this detailed description, the device of the invention has been described considering its application for drying metallic strips on which an oil emulsion or pure oil or other appropriate lubricant liquid had been previously deposited. The same device can be used for obtaining a perfect cleaning and uniform removal of dust and/or scale from strip surfaces prior to its winding.