Patent GB-433620-A (GB)
Title: Improvements in and relating to means for determining the state of wire ropes
IPC: G01N27/82
Filed: 1934-02-14
Abstract: 433,620. Wire ropes. PHILLIPS, L. H. J., 41, Fairlands Road, Sale, Cheshire, KING, A. J., 46, Raglan Road, Stretford, ARMOUR, A. M., 140, Manley Road, Whalley Range, both in Manchester, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Feb. 14, 1934, No. 4934. [Class 109] [See also Groups XXXVI and XXXVII] Wire ropes or rods, tubes, bars, &c. of magnetic material having uniform cross-section are tested for flaws by magnetizing the rope &c. longitudinally and causing the variation of the magnetic flux at the surface due to a flaw to actuate a pivoted magnetic member and thereby close two contacts in succession. As shown in Fig. 1, the wire rope 1 to be tested is moved vertically between two electromagnets 2, 3, by which a portion of the rope is magnetized in the longitudinal direction. The magnets 2, 3 are supported on a framework 8 having guiding wheels 9 which maintain the relative positions of the rope and the electromagnets. The framework 8 may be in two parts hinged together so that the apparatus may be clamped in place round the rope. Between the poles of the electromagnet 2 is an indicating or detecting device 10 comprising an evacuated or evacuable enclosure 11 of glass or other non-magnetic material within which is pivotally mounted a magnetic needle 12 of a high permeability alloy. The needle carries a contact arm 13 moving between contacts 14, 15 by means of which the circuits of relays or indicators 18, 19 are closed. Normally, the magnetic flux is parallel to the axis of the rope 1, causing the needle 12 to take up the position shown in which the arm 13 is clear of both contacts 14, 15. On the passage of a flaw in the rope past the detector 10 the resulting distortion of the flux at the surface of the rope causes the needle 12 to be deflected in one direction as the flaw approaches and in the reverse direction as it recedes. The contacts 14, 15 are consequently closed in succession, causing successive operation of the indicators or relays 18, 19. The passage of a flaw is thus distinguished from failure of the exciting current in the magnetizing coils 4, 5, 6, 7, which causes the arm 13 either by gravity or by a biassing spring, to engage the contact 15, thereby operating the relay 18 only. In a modification the rope passes through a non-magnetic tube surrounded by two coils for magnetizing the rope, magnetic yokes being provided for the return flux. One construction of detecting device is shown in Fig. 5 and comprises a flattopped evacuated glass envelope 11 mounted on a base or cap 37 provided with pins 38 arranged to fit a standard valve holder. Mounted in a U-shaped bracket 35 is a non- magnetic shaft 32 journalled in pivot screws 33, 34 and carrying a needle 12 of high permeability alloy and an aluminium contact arm 13 which swings between the bent-over upper ends of wires 29, 30. Connection between the arm 13 and the bracket 35 is effected by means of a fine wire 36, the pins 38 being connected to the wires 29, 30 and to wires 27, 28 supporting the bracket 35. The instrument may be applied to the control of protection apparatus for winding gear by imparting different magnetic properties to selected parts of the rope so that when these parts pass a predetermined point an indication will be given or protective apparatus actuated.