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Priority claimed from US06/497,001external-prioritypatent/US4485756A/en
Priority claimed from US06/508,509external-prioritypatent/US4509447A/en
Application filed by Universal SpiralweldfiledCriticalUniversal Spiralweld
Priority claimed from EP84300499Aexternal-prioritypatent/EP0127248B1/en
Application grantedgrantedCritical
Publication of ATE28416T1publicationCriticalpatent/ATE28416T1/en