Method and apparatus for producing a welded joint in thermoplastic strap with differential pressure

• Main Author: ROBERT J. KOBIELLA
• Format: Patent
• Language: English
• Published: 12.05.1994
• Edition: 5
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; CONVEYING; HANDLING THIN OR FILAMENTARY MATERIAL; MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGINGARTICLES OR MATERIALS; PACKING; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; STORING; TRANSPORTING; UNPACKING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

The appts. (30) comprises essentially an anvil (32) and an opposed strap engaging member (80), with serrated faces (34, 112) through which the strap (U,L) passes. Anvil (32) has positioner that allows it to squeeze strap (U,L) against member (80) and plunger (92) at a first position, against plunger (92) only at a second position, and to disengage wholly at a third position. Strap engaging member (80) has a coaxial spring-loaded plunger (92) and is mounted on bearings (60) in cavity (54) of drive shaft (46), which itself is mounted on bearings (44) in bore (42) of support frame (40). The axis (58) of member (80) is offset (X) from the axis (48) of drive shaft (46), so rotation of the drive shaft confers an orbital motion to member (80). When the motion is applied to strap (U,L) clamped between anvil (32) and member (80), it creates friction between the strip faces and forms a friction weld conventionally. When anvil (32) is moved to the second position, the orbital motion is disengaged and smooth-faced plunger (92) maintains pressure on strap (U,L) while the weld cools.