Abstract: A depth measuring device is used for measuring the depth of insulation on an electric conductor travelling along a predetermined path. The device includes a cylindrical magnetizable core (11) which generates a magnetic field having an axis directed to intersect the path. The core (11) is magnetized by an electric coil (12) coupled to the core (11) and the current drawn by the coil (12) will vary with the distance of the conductor from the core (11) and so provides an indication of the distance of the conductor from the core (11). A laser beam (14) is directed along the axis of the core so as to lie coaxial with the magnetic field. A detector (15) detects light reflected from the outer surface of the insulation and so provides an indication of the distance of the insulation from the core (11). An electrical system subtracts the two measured distances from each other to provide an indication of the insulation thickness.

Abstract: An apparatus for use in determining the thickness of the insulated coating of an electrical cable manufactured in an extrusion process having means for generating an alternating current in the cable core coupled with means for detecting the magnetic field produced by the current flow in the cable such that in combination with a measurement of the distance from the detection means to the coated cable surface, a determination of coating thickness may be made.

Abstract: The invention relates to method and apparatus for measuring and displaying the eccentricity or off-set position with respect to coaxiality of a metallic conductor within an insulating coating during an extrusion process. The measuring apparatus employs a combination of optical and electrically inductive techniques to determine respectively the position of the outer coating of the cable and that of the core within the cable. By relating these positional measurements it is possible to determine the position of the core relative to a desired location namely the coaxial position so that appropriate corrections can be made to the extrusion process to keep the core in that coaxial position.

Abstract: The invention relates to method and apparatus for measuring and displaying the eccentricity or off-set position with respect to coaxiality of a metallic conductor within an insulating coating during an extrusion process. The measuring apparatus employs a combination of optical and electrically inductive techniques to determine respectively the position of the outer coating of the cable and that of the core within the cable. By relating these positional measurements it is possible to determine the position of the core relative to a desired location namely the coaxial position so that appropriate corrections can be made to the extrusion process to keep the core in that coaxial position.

Abstract: Apparatus for determining the dimension and position of an elongate object (1) travelling freely in space, for example, a cable being coated in an on-line extrusion process. Two separate out-of-focus images of the object (1) are formed on respective charge coupled devices (5) and (6) positioned on either side of the image plane of the optical system (2, 4) employed. By monitoring variations in the comparative characteristics of the two images caused by object movement and size variation, using conditioning circuits (7) and (8) and an indicator/controller unit (9), the spatial position of the object (1) and its dimensions are determined on a continuous basis whereby it is possible to compensate for inaccuracies in dimensional measurement caused by object movement in space, and to control thereby the extrusion process.

Abstract: The apparatus disclosed includes at least two optical measuring devices for forming independent images of the object in their respective focal planes. From these images a specific dimension of the object, for example its diameter where a circular object is concerned, may be obtained. To correct for inaccuracies due to product movement, the dimension of the product obtained from one of the measuring devices is compensated by a positional measurement obtained from the other camera and vice versa. By this means accurate determination of the size of a product, for example a cable moving in an extrusion run, is possible without contact being necessary within the product.

Abstract: Apparatus for controlling the tension of travelling filamentary material such as that being unwound from a drum or spool. It comprises a three phase induction motor for turning the drum or spool modified to have a high resistance rotor providing a torque speed characteristic of falling torque with increasing speed. The motor drive, and torque in either forward or reverse drive, is controlled by a pair of thyristor banks selectively triggered for forward and reverse drive modes by error signals representative of variation in tension from the required value.