Method of making spirally wound flexible, plastic tubing

Claim 1

IN A PROCESS FOR THE CONTINUOUS PRODUCTION OF A RELATIVELY THIN WALLED, HIGH STRENGTH PLASIC TUBING PRODUCT COMPRISING, CONTINUOUSLY EXTRUDING FROM A STATIONARY EXTRUDER A HOT PLASTIC MATERIAL OF GENERALLY NON-ELASTIC TYPE INTO STRIP FORM, WITH SAID STRIP OF MATERIAL COMPRISING LATERALLY DISPOSED FLANGES AND AN INTEMEDIATE RIB PORTION, WINDING SAID STRIP OF HOT PLASTIC MATERIAL IN SPIRAL FORM ON A MANDREL DIRECTLY FROMTHE EXTRUDER BY ROTATING SAID MANDREL, TO CAUSE SAID FLANGES TO BE DISPOSED IN LAPPED, HEAT-BONDED SECURED RELATION WITH THE FLANGES OF ADJACENT CONVOLUTIONS OF THE SPIRALLY WOUND STRIP OF MATERIAL WHILE APPLYING EXTERNAL ROTATIONAL PRESSURE AT AN ANGLE TO THE TUBING PRODUCT AT A POINT DISTANT FROM THE POINT OF EXTRUSION TO MOVE THE TUBING AXIALLY OF THE MANDREL AWAY FROM THE POINT OF EXTRUSION AT A SPEED DIFFERENT FROM THE SPEED IMPARTED TO THE MOVEMENT OF THE TUBING PRODUCT BY ROTATION OF THE MANDREL, THEREBY TO CONTROL THE DISTANCE BETWEEN THE CENTERS OF ADJACENT RIB PORTIONS AND THE AMOUNT OFOVERLAP OF THE FLANGES AS THE STRIP IS EXTRUDED ONTO THE MANDREL INSAID BONDED RELATION SO AS TO VARY THE FLEXIBILITY OF THE TUBING PRODUCT.