Method of prestressing concrete pipe

Claim 1

IN THE MANUFACTURE OF PRESTRESSED CONCRETE PIPE, THE METHOD OF PRESTRESSING A CONCRETE CORE TO A GIVEN MAGNITUDE COMPRISING THE STEPS OF PROVIDING A TUBULAR CONCRETE CORE BODY IN SUBSTANTIALLY CURED CONDITION, SECURING ONE END OF A FIRST REINFORCEMENT WIRE TO ONE END OF THE CORE BODY AND HEILCALLY WINDING THE WIRE FROM SAID ONE END OF THE BODY TO THE OTHER END THEREOF UNDER SUBSTANTIAL TENSION AT A PITCH SUCH THAT THE MAGNITUDE OF THE WINDING STRESS ON THE CORE IS SAFELY BELOW THE MAGNITUDE WHICH WOULD INDUCE CIRCUMFERENTIALLY CRACKING OF THE CORE BODY, SECURING THE OTHER END OF SAID WIRE TO THE BODY WHILE MAINTAINING THE TENSION UNDER WHICH THE SAME WAS WOUND, SECURING ONE END OF A SECOND REINFORCEMENT WIRE TO ONE END OF THE CORE BODY AND HELICALLY WINDING SAID SECOND WIRE FROM SAID END TO WHICH IT IS ATTACHED TO THE OTHER END OF THE CORE BODY BETWEEN THE TURNS OF SAID FIRST WIRE UNDER SUBSTANTIAL TENSION AND AT A PITCH SUCH THAT THE MAGNITUDE OF THE WINDING STRESS ON THE CORE IS SAFELY BELOW THE MAGNITUDE WHICH WOULD INDUCE CIRCUMFERENTIALLY CRACKING OF THE CORE BODY BUT SUFFICIENTLY GREAT THAT, TOGETHER WITH SAID FIRST WIRE, THE CORE IS PRESTRESSED TO SAID GIVEN MAGNITUDE, AND SECURING THE OTHER END OF SAID SECOND WIRE TO THE CORE BODY WHILE MAINTAINING THE TENSION UNDER WHICH THE SAME WAS WOUND.