Catheter with helical drive shaft and methods of manufacture
Drive shafts having helical blades and methods of making are disclosed. In one method a helical auger blade is formed by twisting or sculpting a heated polymer tube which has been placed over a cylindrical drive shaft. In another method a drive shaft is placed within a helical winding and heat is applied to melt polymer which has been coated over one or both of the drive shaft and helical winding.
1. A method of making a helical drive shaft having a helical auger blade with a desired pitch, depth, width and outer diameter comprising:
placing a cylindrical drive shaft into a polymer tube, the polymer tube having opposite ends, a longitudinal axis extending between the opposite ends, and a generally circular cross section;
attaching one end of the polymer tube to the drive shaft;
applying heat to the tube overlying the drive shaft at a temperature sufficient to soften the polymer tube; and
twisting the softened polymer tube about the longitudinal axis and relative to the drive shaft to buckle a portion of the tube, the buckled portion of the tube forming at least a portion of the helical auger blade with the desired pitch, depth, width and outer diameter.
2. The method of claim 1 wherein the drive shaft comprises wire wound in alternating right and left hand layers.
3. The method of claim 1 wherein heat is applied to the tube at a temperature of 425° F.
4. The method of claim 1 wherein the drive shaft has a diameter (D DS ), the polymer tube has a diameter (D POLY ), the polymer tube has a wall thickness (T POLY ), and wherein the auger blade has a radial length equal to approximately: (πD POLY −πD DS )/2.
5. The method of claim 1 wherein the drive shaft has a diameter (D DS ), the polymer tube has a diameter (D POLY ), the polymer tube has a wall thickness (T POLY ), and wherein the helical auger blade has an outer diameter equal to approximately: D DS +(πD POLY −πD DS )+2T POLY .