I was wondering how inner tubes are made. A Google search turned up little info, which surprises me.

Are they extruded in a tube, the edges joined and valve vulcanized onto them? If so how is the valve held in place and what type of tool joins the seams and valve?

Or are they extruded into a flat sheet and joined around the circumference too?

THE REASON I ASK: I was pondering a tubeless tire. Imagine a tire made in the normal way, except that along the bead is extruded / formed a sheet of rubber, tube weigh in thickness. It is slightly more in width than half the width of what would be a nominal rim size. The rubber would be pressed in from both sides and vulcanized along the circumference and a valve joined in where it meets. Essentially a tire with an enclosing piece of rubber across the two beads that would set in the rim and act as the tube side sealer to hold air. Or to put it another way a tube with a tire tread and bead built onto it.

Benefits would be no pinch flats and lighter weight. It wold not require such careful sealing as "regular" tubeless tires, along the rim OR the spokes in the rim as the entire volume of air is enclosed with rubber all sealed to the tire carcass.

Down side is that flats would have to be plugged from the outside only, perhaps with mushroom headed plugs inserted through the tread.

Just and idea, and probably crazy. The flaps would have to be vulcanized together around the circumference with some sort of tool that could reach inside the tire till it got to the place where the valve would be placed. How the valve would be vulcanized in place is beyond me. Maybe someone has tried it already.