| 摘要 |
A device for detecting variations in thickness of lubricating film of wires (28) by measuring electrical contact resistance at wire drawing in a drawing bench. In a drawing bench of the intended type the wire runs between uncoiling and coiling capstans (12 and 14, respectively) or so-called pulleys, a drawing box (16) provided with lubricant and draw plate (22) being placed between the capstans and pulleys, respectively. Part of the wire, the lubricating film, the draw plate and additional members associated with the drawing bench form a closed electric circuit. The very wire (28) receives current contactless via a transformer (34), which is fed from an A. C. current source (32). A capacitive sensor (38) containing a tubular electrode (40) providing a capacitive connection between the wire and an amplifier (42) is arranged in a casing (44) galvanically connected to the draw plate for measuring the voltage across the lubricating film. An evaluating means (64) electrically connected to the measuring sensor is arranged to determine the resistance of the lubricating film according to the formula: Rx = k (U/i), where i is the current through the wire (28) to be measured, U is the voltage measured via the sensor (38) and k is a constant. It is possible to evaluate by means of Rx so-called tearing, wear of draw plate and variation in quality of the produced wire. |
