Single web grid with reinforced bulb

Abstract

Manufacture of roll formed one piece sheet metal grid tees that affords different load ratings with the same gauge and quality of sheet stock and the same overall cross-section dimensions by varying the width of the strip used to make the tees and disposing material added for increased load rating at the area of the hollow reinforcing bulb of the tees.

1 . A method of manufacturing grid tees of different load ratings comprising operating a roll-forming line to make grid tees of at least two different load ratings from strips of metal sheet stock of essentially uniform thickness that is formed into a tee with a single web and a hollow bulb, the hollow bulb being made from stock adjacent one edge of the web, increasing the width of the stock strip fed to the roll-forming line in some production runs to increase the load rating of the grid tee and decreasing the width of the stock strip fed to the roll-forming line in other production runs to lower the load rating of the tee, the additional material of the strip of increased width being rolled so that it is contiguous with the bulb while causing the external dimensions of the bulbs of the tees of increased and the decreased ratings to remain essentially the same whereby the grid tees of different load ratings can be produced on the same roll set without the need for significant adjustment or substitution of rolls. 
   
   
       2 . A method as set forth in  claim 1 , wherein the additional material of the strip of increased width is formed so that it lies within the bulb. 
   
   
       3 . A method as set forth in  claim 2 , wherein the additional material of the strip of increased width is formed so that it follows the contour of an outer layer of the bulb. 
   
   
       4 . A method as set forth in  claim 3 , wherein the additional material of the strip of increased width is formed to follow the contour of substantially all of the outer layer of the bulb thereby forming a double layer bulb. 
   
   
       5 . A method as set forth in  claim 3 , wherein the additional material of the strip of increased width is formed in a scroll-like relation to the outer layer of the bulb. 
   
   
       6 . A grid tee for a suspended ceiling, soffit, or like structure, the grid tee being of the inverted tee style and being roll-formed from a single strip of sheet metal of a selected width, the tee having a lower flange, an upper hollow reinforcing bulb, and a web extending between the flange and the bulb, the lower flange having portions on each side of the web that are of generally equal width, at least one of the flange portions being of a double layer, the web being of a single layer, the bulb having a width and height, the width being generally centered over the web, at least a portion of the bulb being a double layer that increases the load rating of the tee. 
   
   
       7 . A grid tee as set forth in  claim 6 , wherein said bulb is curvilinear in section. 
   
   
       8 . A suspended ceiling grid tee as set forth in  claim 7 , wherein said bulb is round in cross-section. 
   
   
       9 . A suspended ceiling grid tee as set forth in  claim 7 , wherein said bulb is oval in cross-section. 
   
   
       10 . A suspended ceiling grid tee as set forth in  claim 6 , wherein said double layer bulb portion includes a fold at a part of the cross-section of the bulb that is remote, as measured along the cross-section, from a point where the bulb transitions with the web. 
   
   
       11 . A suspended ceiling grid tee as set forth in  claim 6 , wherein said double layer bulb portion, in cross-section, is scroll-like in relation to an outer layer of the bulb.