Safeness indicator for flexible shafts used in automotive steering mechanisms

Safety indicating unit for indicator condition of safeness of a flexible shaft rotating in response to rotation of a steering wheel in a vehicle steering system wherein deterioration of said flexible shaft produces greater torsional deflection thereof when said steering wheel is rotated in either direction, said unit including

• a base plane comprising a plastic film sheet having piezoelectric properties, said sheet being provided with a metallized coating on upper surface thereof and secured to an outermost layer of windings of said flexible shaft with an electrically conducting adhesive material,
• a pair of plastic piezoelectric strips adhered on said upper surface of said base plane by electrically conducting adhesive material, said strips each provided with a metallized coating on both surfaces thereof, exposed surfaces of said strips being of opposite polarity,
• means for generating electrical signals by said strips in proportion to torsional deflection of said flexible shaft, and
• other means for translating said generated electrical signals into an indication of safeness of said torsionally deflected flexible shaft.

Safety indicating unit for indicating condition of safeness of a flexible shaft rotating in response to rotation of a steering wheel in a vehicle steering system wherein deterioration of said flexible shaft produces greater torsional deflection thereof when said steering wheel is rotated in either direction, said unit comprising

• a pair of plastic piezoelectric strips disposed helically about said flexible shaft, each strip of said pair of strips disposed helically with an opposite pitch and spaced longitudinally along said flexible shaft, each of said strips being metallized on both surfaces thereof, each of said metallized surfaces having an electrical conductor attached thereto adjacent an end portion thereof, each surface of each strip being of opposite polarity,
• means for generating separate electrical signals by each of said strips in proportion to torsional deflection of said flexible shaft, said separate electrical signals comprising signals generated by one of said pair of strips in response to rotation of said steering wheel and flexible shaft in one direction and other signals generated by other of said pair of strips in response to rotation of said steering wheel and flexible shaft in other direction, and
• other means for translating said generated electrical signals into an indication of safeness of said torsionally deflected flexible shaft when rotated in one direction and in the other direction.