One-sided covered marking on sheet metal surfaces

Abstract

The object of the process is to hide a visible and legible mark ( 7 ) impressed on one side of a thin metal sheet ( 6 a ) used for making beverage cans in such a way that an image does not show on the reverse side. A second impression ( 10; 11; 12; 13 ) is embossed on the reverse side ( 6 b ) in such a way that the visibility and legibility of the mark ( 7 ) is retained on the one side, but the image on the reverse side is covered and made illegible.

1 . A method for providing a hidden mark (on) a thin metal sheet, preferably a beverage can, wherein 
 a visible and legible mark ( 7 ) is provided on one side ( 6   a ) of the sheet metal by embossing;    the reverse side ( 6   b ) of the metal sheet provided with such marking, is subsequently impressed ( 10 , 11 , 12 , 13 ) in such a way that the visibility and legibility of the impressed mark ( 7 ) on the one side is retained, but the mirror image ( 8 ) appearing on the reverse side by the first impressing is covered by the subsequent impression ( 10 ), especially obscured.    
     
     
         2 . Method according to  claim 1 , characterized by the image ( 8 ) of the first impression ( 7 ) being subsequently covered on the reverse side by a textural or hatched second impression on that side after the first impression.  
     
     
         3 . Method according to claims  1  or  2 , characterized by the result that the first impression on the inner side of the lid ( 3 ) tab ( 3   a ) being covered or made illegible by impressing ( 10 ) the corresponding area of the lid tab from the outside of the lid.  
     
     
         4 . Method according to claims  1  or  2 , characterized by the image of the first impression ( 7 ) on the underside ( 6   a ) of the grip of a grip loop ( 5 ) made of thin sheet metal for tearing out the tab ( 3 ), being covered by a second impression on the outside ( 6   b ) of the grip area ( 6 ).  
     
     
         5 . Method according to  claim 1 , in which the sheet metal is so thin that the first impression ( 7   a,    7   b,    7   c;    7 ) forms an image ( 8   a,    8   b,    8   c;    8 ) visible from the reverse side even if this is not embossed or raised.  
     
     
         6 . Method according to  claim 1 , in which the second impression causes a change in the surface in a restricted area ( 10 ′, 10 ′″, 10 ″) which reduces the smoothness or quality of the surface compared to sections adjoining the image ( 8 ) which have been untouched by the first impression.  
     
     
         7 . Method according to  claim 1 , in which the first impression forms a mark ( 7   a,    7 ′, 7   a ′) which penetrates the surface by means of carving, tearing or any other method.  
     
     
         8 . Method according to  claim 1  or  claim 7  in which the first impression more clearly penetrates and changes the surface in a more strongly localized area ( 7   a ′, 7   a ″) than the subsequent impression on the reverse side ( 6   b ) which extends wider ( 10 ′) and alters the surface to a smaller depth.  
     
     
         9 . Method according to  claim 1  in which the subsequent impression forms a point-pattern ( 11 ) in a limited field ( 10 ′″) on the reverse side.  
     
     
         10 . A thin sheet metal portion of a can ( 1 ), like the body of the can, its bottom, the lid ( 2 ) or tear-out tab ( 5 ) for attaching to a tear-out lid ( 2 ), wherein 
 (i) a visible, legible mark or identification ( 7 ) is embossed on an interior face ( 6   a ) by a first impression, especially by means of scoring;    (ii) an image ( 8 , 8 ′, 8 ″) of the first impression appearing on the outer face ( 6   b ) is covered by a surface impression ( 10 ; 11 ; 12 ; 13 ),    for at least substantially complicating legibility.    
     
     
         11 . A part of thin sheet material, especially lid ( 2 ) or grip loop ( 5 ) for a sheet metal can according to  claim 10 , characterized by the outer image ( 8 ) of an interior mark ( 7 , 7 ′, 7 ″) being hidden, is surface covered by a textured, patterned or hatched subsequent impression in the sense of an operation changing the structure of the surface ( 10 ; 11 ; 12 ; 13 ).  
     
     
         12 . Metal sheet portion according to  claim 10  the difficult legibility on a sheet metal part means that it is actually illegible.  
     
     
         13 . Metal sheet portion according to  claim 10  or  claim 11 , the sheet metal part is a section of a beverage can.  
     
     
         14 . A proc ss for providing hidden marking of a surface, especially a sheet metal surface of a can for drinking liquids (beverage), in which process 
 a visible mark ( 7 ) is made by means of a strongly penetrating first impression on one side ( 6   a ) in at least a limited section of the surface;    a second weakly penetrating impression is made on the reverse side ( 6   b ) which alters the surface ( 10 ;  11 ;  12 ;  13 ) to such an extent that 
 the visibility of the mark ( 7 ) made by the first impression on one the side is retained,  
 an image ( 8 ) formed by the first impression on the reverse side, is hidden by the second impression ( 10 ;  11 ,  12 ) and made essentially illegible.  
   
     
     
         15 . Method according to  claim 1  or  claim 14  in which the sheet metal is thinner than 0.3 mm.  
     
     
         16 . A portion of the sheet metal obtainable by a method according to  claim 1  or  claim 14 .  
     
     
         17 . Metal sheet portion ccording to claims  10 ,  11 , or  16 , a thin metal portion ( 3   a ′) of the grip ( 6 ) is provided with a tear-out loop ( 5 ) which is made rigid on at least three sides by means of a shaped edge ( 6   c ). The first and second impressions lie on opposite sides of the respective surface.  
     
     
         18 . Method according to  claim 1  or  claim 14 , in which the depth of penetration of the first impression is greater than that of the second one on the reverse side, i.e. the depth of penetration (t 11 ) of the second impression is less than that (t 7 ) of the first impression.