Method of making bellows

Claim 1

In a method for making an axially extendable and contractable camera and enlarger bellows of the type including a plurality of sides defining a hollow body having a generally polygonal cross-section and an open front and rear end, each side of which has a multiplicity of pleats forming successive ridges and valleys with each ridge and valley being formed by relatively rigid planar surfaces separated by a relatively flexible joint, the improvement comprising: moving a single web of a dielectric sheet material past at least one die having die edges arranged in a predetermined pattern for producing a separable bellows blank having parallel fold lines formed therein for forming said multiplicity of pleats; die forming said bellows blank by heating said die with rf heating and effecting contact between said die and a portion of said web; separating said blank from said web and folding said blank on a form so that one longitudinal edge thereof overlaps another longitudinal edge thereof so as to produce a seam; bonding said seam by a resistance heated seaming device to produce a welded seam; and manually compressing said hollow body along the longitudinal axis thereof and along said fold lines so as to produce a polygonal bellows body having said ridges and valleys in each of the sides thereof.