BigPatents India

The invention provides for a mehtod of designing spiral ribs for a duct used in cable blowing comprising th esteps of selecting an apex of rib in the range of 80 to 120 degrees; determining the longitudinal spacing between the ribs from the cable thickness and mass; deriving a range of values for rib density and the helix angle from the longitudinal spacing , determining the optimum rib density and helix angle from the range of values by determining net axial force for the range of values; determining the optimum rib height for the optimum rib density and helix angle, such that a reduction in friction between the cable and the duct without a significant or no reduction in axial force is achieved.