Methods and apparatus for folding sheet material

A method of folding a bag formed of two overlying sheets of pliable material, said bag being closed except for an open mouth at one side of said bag, said method comprising

• arranging said bag so that said mouth faces in one direction;
• winding said bag about a rotary mandrel to form a roll having said mouth at one end of said roll;
• transferring said roll to a pleating station;
• clamping said roll at that end thereof opposite said one end;
• creasing said roll at said pleating station a plurality of times in succession in a direction from said opposite end toward said one end while maintaining the clamping of said opposite end of said roll thereby forming a pleated packet from said roll;
• and
• unclamping said opposite end of said roll following the creasing thereof.

Apparatus for folding overlying sheets of pliable material forming a bag closed except for an open mouth at one side of said bag, said apparatus comprising:

• rotatable mandrel means for winding said bag into a roll having said mouth at one end of said roll;
• means forming a pleating station;
• transfer means for transferring said roll to said pleating station;
• and
• pleating means at said pleating station operable to crease said roll at successive zones in a direction toward said mouth and form a pleated packet from said roll, the successive creasing of said roll enabling air within said bag to be expelled through said mouth.

Apparatus for folding a bag formed of overlying sheets of pliable material, said bag being closed except for an open mouth at one side thereof, said apparatus comprising:

• a rotatable mandrel on which said bag may be wound to form a cylindrical roll having opposite ends, said mouth of said bag being at one end of said roll, said mandrel having air passages in communication with its surface;
• air pressure control means for selectively establishing negative and positive air pressure at the surface of said mandrel for respectively enabling and disabling adherence of said bag to the surface of said mandrel;
• a pleating station spaced from said mandrel;
• releasable gripping means operable to grip said roll at an end thereof following winding of said bag about said mandrel;
• transfer means coupled to said gripping means and operable to transfer said roll from said mandrel to said pleating station;
• and
• pleating means at said pleating station for creasing said roll successively at a plurality of zones between its ends and in a direction toward said one end thereof to form a pleated packet having a plurality of pleats adjacent one another, the successive creasing of said roll enabling air within said bag to be expelled through said mouth.