Metal can being a pressure tight metal packaging

Abstract

Metal can wall suitable to form part of a pressure tight metal packaging further comprising a bottom and a top adjoining the wall having essentially one main wall thickness, whereby the wall is provided with means other than the bottom or the top supporting the wall essentially along its circumference.

1 . Metal can, being a pressure tight metal packaging, comprising an ironed side wall stretching essentially along an axial direction and a circumferential direction, and a first end closure adjoining the side wall in a first wall-to-closure transition portion, and a second end closure adjoining the side wall in a second wall-to-closure transition portion, which side wall comprises a main side wall portion stretching from the first wall-to-closure transition portion to the second wall-to-closure transition portion, wherein the main side wall portion is provided with means of increased side wall thickness supporting the side wall essentially along the circumference of the can, consisting of one annular portion of wall ironed metal in which the thickness of the side wall is greater than the side wall thickness in the main side wall portion outside the annular portion, characterised in that the one annular portion comprises wall ironed metal that has been reduced in thickness by more than 39.4%, and the side wall thickness in the annular portion is less than 40 μm thicker than the side wall thickness in the remainder of the main side wall portion.  
     
     
         2 . Metal can according to  claim 1 , characterised in that the one annular portion comprises wall ironed metal that has been reduced in thickness by more than 41.6%, preferably by more than 45.1%.  
     
     
         3 . Metal can according to  claim 1  or  2 , characterised in that the main side wall portion outside the annular portion comprises wall ironed metal that has been reduced in thickness by more than 50.6%.  
     
     
         4 . Metal can according to  claim 1 ,  2 , or  3 , characterised in that the main side wall portion comprises steel, preferably packaging steel.  
     
     
         5 . Metal can according to  claim 1 , characterised in that the annular portion is intersected along essentially the entire circumference by a cross sectional plane through the metal can, located halfway between the first wall-to-closure transition portion and the second wall-to-closure transition portion.  
     
     
         6 . Metal can according to  claim 1  or  5 , characterized in that the annular portion is a circumferential rib protruding inwardly from the inside surface of the side wall into the packaging.  
     
     
         7 . Metal can according to any one of the preceding claims, characterised in that the side wall thickness in the annular portion is not more than 28 μm thicker than, by preference not more than 22 μm thicker, than the side wall thickness in the remainder of the main side wall portion.  
     
     
         8 . Metal can according to any one of the preceding claims, characterised in that, when seen in a longitudinal section of the metal can, the annular portion comprises a portion wherein the side wall thickness is constant over an axial distance.  
     
     
         9 . Metal can according to any one of the preceding claims, characterised in that, when seen in a longitudinal section of the metal can, the thickness of the side wall in the annular portion of the main side wall portion, measured at increasing distances from the first end closure, first gradually increases from the thickness of the side wall outside the annular portion to a maximum thickness of the side wall inside the annular portion over a section with an axial length D 1 , and then decreases from the maximum thickness to the thickness in the remainder of the main side wall portion outside the annular portion over a section with an axial length D 2 , which length is shorter than D 1 , and wherein the first end closure is integral to the side wall.  
     
     
         10 . Metal can according to any one of the preceding claims, characterised in that, the first end closure is integral to the side wall, and, when seen in a longitudinal section of the metal can, the thickness of the side wall in a section of the annular portion of the main side wall portion, measured at increasing distances from the first end closure, gradually increases from the thickness of the side wall outside the annular portion to a maximum thickness of the side wall inside the annular portion, in which section the surface of the side wall inside the packaging is wedged with respect to the corresponding surface of the side wall on the outside of the packaging at an angle between 0.01 and 5°, by preference at an angle between 0.01 and 1°, more by preference at an angle between 0.01 and 0.25°.  
     
     
         11 . Method of producing a metal can, being a pressure tight metal packaging, comprising an ironed side wall stretching essentially along an axial direction and a circumferential direction, and a first end closure adjoining die side wall in a first wall-to-closure transition portion, and a second end closure adjoining the side wall in a second wall-to-closure transition portion, which side wall comprises a main side wall portion stretching from the first wall-to-closure transition portion to the second wall-to-closure transition portion, wherein the main side wall portion is provided with means of increased side wall thickness supporting the side wall essentially along the circumference of the can, consisting of one annular portion of wall ironed metal in which the thickness of the side wall is greater than the side wall thickness in the main side wall portion outside the annular portion, the method comprising the steps of (i) producing cups in at least one drawing operation, (ii) reducing the side wall thickness using at least one ironing die and a punch having a forming contour in longitudinal cross section comprising an essentially straight section provided with a recess, the recess being provided for forming the annular portion, characterised in that the recess has a depth of less than 40 μm and thickness of the main side wall portion where the recess is located is reduced from at least 313.5 μm to less than 190 μm.