Patent ID: 7793531

Claim:
A method of press forming corrugations of a selected width into a sheet comprising: detachably mounting a first pair of separate spaced apart parallel elongated forming bars on edge to a die holder mounted on a press ram member, spacing apart said first pair of forming bars at a distance corresponding to the spacing of a first set of corrugation bends; detachably mounting a second pair of separate spaced apart parallel elongated forming bars on edge to a base member mounted on another press ram member, said second pair of forming bars positioned in alignment with said first pair of forming bars, spacing apart said second pair of forming bars a distance corresponding to the spacing of a second set of corrugation bends, said first and second pairs of forming bars spaced apart a different distance so that said forming bars in said first pair of forming bars is more narrowly spaced apart and fits within the space between said forming bars in said second pair of more widely spaced forming bars with a clearance therebetween; placing said sheet between said first and said second pair of forming bars and advancing said first pair of forming bars into the space between said second pair of forming bars by press operation to engage with said sheet and thereby form a corrugation therein as said first pair of forming bars moves between said other pair of forming bars moves between said second pair of forming bars; and repeating said operation on successive sections of said sheet to corrugate the same.