Portable screw driver having flexible extension shaft

In a cordless portable electric screwdriver having a chuck for normally holding a tool for rotary driven motion at one end thereof, the improvement comprising:

• a flexible extension shaft having a first end adapted to cooperate with said chuck and a second end adapted to hold said tool for rotary driven motion, said first end of said flexible extension shaft and said chuck having complementarily shaped non-circular cross-sections, said chuck having an axis and being adapted to receive said first end of said flexible extension shaft by means of axial insertion of said shaft into said chuck with said non-circular cross-sections in rotationally aligned relationship and said chuck also including means for holding said first end of said flexible extension shaft for rotary driven motion of said shaft, said second end of said flexible extension shaft and said tool having complementarily shaped non-circular cross-sections, said second end of said flexible extension shaft including means for holding said tool for rotary driven motion thereof;
• said flexible extension shaft normally being disposed so as to be substantially entirely coaxial with said chuck, said flexible extension shaft being universally deflectable relative to said axis of said chuck so as to position said second end of said shaft and said tool at an acute angle relative to said axis of said chuck, said tool being rotary driven by said cordless portable electric screwdriver through said flexible extension shaft;
• one of said first end of said flexible extension shaft and said chuck including a male hex shank and the other of said first end of said flexible extension shaft and said chuck including a female hex shank-receiving opening defining said complementarily shaped non-circular cross-sections;
• one of said second end of said flexible extension shaft and said tool including a female hex shank-receiving opening and the other of said second end of said flexible extension shaft and said tool including a male hex shank defining said complementarily shaped non-circular cross-sections;
• one of said first and second ends of said flexible extension shaft including a generally cylindrical body portion terminating in said male hex shank and the other of said first and second ends of said flexible extension shaft including a generally cylindrical body portion terminating in said female hex shank-receiving opening;
• said flexible extension shaft including a plurality of concentric coil springs in tightly wound adjacent relation extending between and secured to said generally cylindrical body portions of said first and second ends of said shaft to accommodate universal deflection of said shaft relative to said axis of said chuck;
• and
• a flexible sleeve disposed about said concentric coil springs, said flexible sleeve having cylindrical fittings secured thereto at opposite ends thereof so as to define a shoulder internally of each of said fittings, said cylindrical fittings each being adapted to receive one of said cylindrical body portions therein;
• said cylindrical body portions being spaced apart by a distance greater than the distance between said shoulders and said cylindrical fittings to permit limited axial movement of said cylindrical body portions and said concentric coil springs relative to said cylindrical fittings and said flexible sleeve.