METHOD OF RADIAL WELDING BY MOTION FRICTION OF THIN-WALLED TUBULAR PARTS MADE FROM THERMOPLASTIC POLYMERS AND DEVICE FOR REALIZATION OF THIS METHOD Russian patent published in 2004 - IPC

FIELD: welding parts made from thermoplastic polymers in form of bodies of revolution by motion friction. SUBSTANCE: proposed method includes relative engagement of parts to be welded over two mounting surfaces of different diameters, relative rotation of parts, braking and holding them for cooling. Relative engagement of parts is effected over cylindrical engageable mounting surface at radius of outer chamfer of end of pipe changing to conical surface of end face equal to 5-6 magnitudes of radius of change from inner cylindrical surface to cone of bell-mouth. Engagement of parts over other mounting surface is carried out at initial clearance between engageable taper surfaces of end face of pipe and cone of bell mouth not exceeding 1/3 of minimum thickness of walls of parts to be welded together. Walls of parts are pressed by preset radial fusion force. After braking, end of pipe is forced axially into bell mouth at preset force till end of pipe and cone of bell mouth are brought in contact. Circumferential, axial and radial forces applied to parts to be welded together are smoothly distributed over cylindrical surfaces of parts in zone of their contact; radial forces applied outside and inside are balanced. Walls of parts are compressed by radial setting force. Device proposed for realization of this method is provided with clamp having cylindrical working surface, cylindrical slide mandrel which is coaxial to clamp and is provided with drive for motion along axis, pneumatic system for supply and distribution of compressed air, command apparatus and valve unit of pneumatic system. Clamp has toroidal pneumatic chamber communicated with valve unit and fitted on bell mouth. This chamber is made from reinforced elastomer. Cylindrical slide mandrel is located inside bell mouth for rotation and transmission of torque from drive. Mandrel is also provided with toroidal pneumatic chamber which is also made from reinforced elastomer. According to second version, cylindrical slide mandrel has two toroidal chambers mounted coaxially and made from reinforced elastomer; their side walls adjoin tightly through anti-friction washers. Pusher made in form of hollow cylinder is placed between side walls of pneumatic chambers at average diameter of their cavities. EFFECT: avoidance of deformation in welding, forming of flash on weld seam; possibility of controllable action on fusion and setting processes. 5 cl, 3 dwg