Method and apparatus for detecting surface flaws in electrical cable plastic jacketing

Abstract From the Canadian patent

Abstract This invention employs principles associated with air-lubricated thrust bearings, to provide highly sensitive indicators of the presence of defects along the surface of a cable insulative layer. A spring-loaded mounted probe containing anaxial air passage is closely directed at the cable surface. The cable is moved linearly under the probe, and air is introduced to create air flow at and along the surface in the vicinity of the probe's outlet oriface. The static pressure at the probe outlet oriface is essentially constant, until a surface defect such as a scratch or a protrusion causes a substantial change in the air pressure or air flow rate. The change is detected and recognized …