Patent Publication Number: US-7582251-B2

Title: Apparatus for cooling a strip of sheet metal

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Applicant claims priority under 35 U.S.C. §119 Of Austrian Patent Application No. A 1336/2004 filed on Aug. 4, 2004. 
     FIELD OF THE INVENTION 
     The invention relates to an apparatus for cooling a strip of sheet metal with nozzles for a cooling liquid to be sprayed onto the bottom side of the strip, which nozzles are arranged beneath the strip in transversal rows relative to the feeding direction of the same. 
     DESCRIPTION OF THE PRIOR ART 
     For the purpose of rapidly cooling hot strips of sheet metal it is known (EP 0 695 590 A1) to spray a cooling liquid, especially water, against the bottom and upper side of the strip, which occurs with the help of jet nozzles which are arranged in longitudinal rows distributed over the width of the strip and extending in the feeding direction of the strip and, depending on each longitudinal row, are situated in a common median spraying surface. The fan jets of the nozzles aligned in the feeding direction of the strip are deflected in an alternating manner to both sides with the help of compressed air transversally to the feeding direction of the strip in order to achieve an even cooling of the strip of sheet metal. This is achieved only insufficiently. In order to prevent any dependence of the spraying surface on the pivoting angle of the fan jet nozzles and the uneven accumulation of cooling water on the upper side of the strip it has already been proposed to use full jet nozzles which are arranged in transversal rows beneath the strip relative to the feeding direction of the strip, so that the cooling liquid is only sprayed against the bottom side of the strip of sheet metal. Since in the case of full jet nozzles, which are pressurized with cooling liquid below a preferred, comparatively low pressure of up to 1 bar, the central spraying region shows a high cooling effect, one must expect a shrinkage of the strip of sheet metal starting from these central spray regions, leading to fluctuations in the thickness over the width of the strip, which cannot be prevented even when the full jet nozzles combined in nozzle beams are moved in an oscillating fashion to and fro transversally to the feeding direction of the strip. An additional factor is that in the longitudinal boundary region there is an inevitable different distribution of the sprayed cooling liquid as compared with the region situated in between, so that although it is possible to achieve a more even cooling with this known apparatus, the cooling is still insufficient to meet higher demands placed on a rapid and even cooling of the strip. 
     SUMMARY OF THE INVENTION 
     The invention is thus based on the object of providing an apparatus of the kind mentioned above for cooling a strip of sheet metal such that the strip of sheet metal can be cooled evenly over its width despite high cooling rates under avoidance of longitudinal strips caused by differences in thickness. 
     This object is achieved by the invention that the nozzles configured as fan jet nozzles form a common middle spraying surface for each transversal row and that covers are provided in the spraying region of the nozzles which are laterally adjacent to the strip of sheet metal. 
     The use of fan jet nozzles whose jets form a common middle spraying surface for each transversal row allows a substantially even distribution of the cooling liquid over the spraying surface, assuming a predetermined alignment of the jet which remains the same during the cooling relative to the bottom side of the strip, because the distribution of liquid which is uneven especially over the longitudinal extension of the spraying region of the individual fan jet nozzles can be offset sufficiently through a respective overlapping of the individual spraying regions. An additional factor is that as a result of the covers which are laterally adjacent to the strip and are in alignment with the bottom side of the strip it is possible to ensure a cooling meeting the conditions in the region between the longitudinal edges, because a wetting of the upper side of the strip in the region of the longitudinal boundary can be avoided which would occur otherwise due to unavoidable turbulent flows, so that the desired even cooling over the width of the strip can be ensured right up to the longitudinal boundary region. 
     Especially advantageous boundary conditions can be maintained when the covers are in alignment with the bottom side of the strip. The lateral covers in alignment with the bottom side of the strip form a spraying surface extending beyond the width of the strip which enables comparable reflection conditions for the sprayed cooling liquid beyond the edge of the strip. 
     In order to advantageously utilize the desired effect of lateral covers it is necessary to ensure a low distance between the longitudinal edges of the strip and the laterally adjacent covers. For this purpose, the covers can be displaced transversally to the feeding direction depending on the course of the longitudinal edge of the strip of sheet metal, which can be realized for example in a simple way from a constructional standpoint by scanning the longitudinal edges of the strip and a control device triggered by said scanning for the actuating drives of the covers. 
     The even sudden use of strip cooling must not be impaired by disturbing influences such as cooling liquid reflected from the housing walls. The same applies to the outlet region of the cooling section. In order to avoid such disturbing influences on the one hand and in order to secure a constructional limitation of the cooling section on the other hand, the spray region of the nozzles in the feeding direction of the strip can be limited by a deflection device for the cooling liquid which is provided beneath the strip of sheet metal. The portion of liquid sprayed by the closest transversal row of nozzles against the deflection device is diverted from the strip before it meets the lower side of the strip, which provides advantageous constructional conditions, especially when the nozzles of the transversal rows at the front and back in the feeding direction of the strip can be set in their inclination about an axis extending in the direction of the transversal row. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter of the invention is shown by way of example in the drawings, wherein: 
         FIG. 1  shows a schematic top view of an apparatus in accordance with the invention for cooling a strip of sheet metal; 
         FIG. 2  shows this apparatus in a side view, and 
         FIG. 3  shows a sectional view along line III-III of  FIG. 2 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The illustrated apparatus for cooling a strip  1  of sheet metal which is conveyed out of a continuous furnace  2  with the help of a supporting air cushion comprises several spray beams  4  and  5  which extend transversally to the feeding direction  3  of the strip  1  of sheet metal and are situated beneath the strip  1  of sheet metal, with the nozzles  6  of the spray beams  4  and  5  configured as fan jet nozzles being arranged in mutually offset transversal rows, as is shown in  FIG. 1 . Within each transversal row, the nozzles each form a common middle spray surface  7 , as is shown in  FIG. 2  with the dot-dash line. This means that the spray cones  8  of the fan jet nozzles  6  which overlap one another in the region of the bottom side of the strip and are shown in dot-dash lines in  FIG. 3  lead to a spray region  9  on the bottom side of the strip as indicated in  FIG. 1  with the dot-dash line, which spray region, in cooperation with the spray regions of the other nozzles of a transversal row, ensures a sufficiently even, strip-like application of the cooling liquid over the width of the strip for the purpose of evenly cooling the strip  1  of sheet metal. Notice must be taken in this connection that the uneven distribution of the cooling liquid of the spray cones in the direction of the nozzle beams  4 ,  5  can be offset substantially by the overlapping of the spray regions  9 . 
     As is shown especially in  FIGS. 1 and 3 , lateral covers  10  are adjacent to the longitudinal edges of the strip  1  of sheet metal on both sides of the strip  1  along the cooling section determined by the nozzle beams  4  and  5 . These covers  10  are in alignment with the bottom side of the strip, which is thus enlarged by the covers  10  with respect to the spraying surface. This means that otherwise unavoidable disturbing influences on the spraying of the cooling liquid in the longitudinal boundary region can be avoided. The lateral covers  10  not only ensure even reflection conditions for the sprayed cooling liquid which continue beyond the edge of the strip, but also prevent cooling liquid from reaching the upper side of the strip of sheet metal in the longitudinal boundary region. By preventing the disturbing influences caused by the edges, advantageous cooling of the strip of sheet metal is ensured in cooperation with the aligned spray cones  8  of the fan jet nozzles  6 , which despite the high cooling rate does not lead to any uneven deformations of the strip. 
     In order to keep the distance between the longitudinal edges of the strip  1  and the lateral covers  10  sufficiently small, the covers  10  are held in a displaceable manner in guides  11  extending transversally to the feeding direction  3  and are connected with actuating drives  12 , which are controlled according to  FIG. 1  via a control device  13  depending on the course of the longitudinal edge of the strip  1 . For this purpose, the course of the longitudinal edge of the strip  1  is scanned via sensors  14  whose output signals are sent to the control device  13 . 
     To ensure that cooling conditions can be observed which are substantially relieved from any disturbing influences in the front and rear end regions of the cooling section defined by the nozzle beams  4 ,  5 , this cooling section is delimited by deflection devices  15  for the cooling liquid which are provided beneath the strip  1  of sheet metal. These deflection devices  15  each consist of a boundary wall  16  with a deflection profile  17  overlapping the same at a distance, as is shown especially in  FIG. 2 . These deflection devices  15  enable defining the spray region of the nozzle beams  4  at the edge in a constructional manner, because the portion of the cooling liquid sprayed against the deflection device  17  is carried off from the spray region, so that disturbing influences are prevented which are caused by reflections of the cooling liquid on walls of the cooling apparatus provided in this region. In connection with a pivoting bearing of the nozzle beams  4 , the cooling conditions at the beginning and end of the cooling section can be set according to the respective conditions. The pivoting capability of the nozzle beams  4  at the boundary side is indicated in the drawing by swivel pins  18 . 
     It is understood that an additional influence can be taken on the cooling effect by a change of the distance of the nozzle beams  4  and  5  from the bottom side of the strip and by a change of the pressurization of the cooling liquid. An advantageous pressurization for the cooling liquid is a pressure of between 1 bar and 3.5 bar.