Manufacture of articles of a substantially sack-like or tubular structure

A method of producing a generally three-sided tubular article from a continuous length or web of sheet material, which comprises the steps of feeding along a path having at least a linear terminal portion two continuous web sections, one superposed upon the other, which are joined along a common edge to provide when viewed in transverse cross-section, a generally U-shaped web configuration having a transverse dimension generally corresponding to the depth dimension of said tubular article sealing together the leading edges of said web sections along a line extending generally transversely of the web length to form the leading end into a two-sided pocket, advancing a generally flattened supporting form in a plane generally coincident with the linear web path portion along an angular path intersecting with said terminal web path portion to introduce said flattened form into said semi-pocket with the leading end of said form engaging said sealed web end, sealing together said two web sections along a transverse strip region immediately proximate the trailing end of said form to close the third side of said end pocket with the form disposed therein, separating the thus-formed pocket from the web sections by severing through said sealed strip to concurrently form a further two-sided semipocket, transfering the separated article containing the supporting form from said terminal path portion, and repeating said advancing, sealing, separating and transfering steps with further supporting forms.