GB1056574A - Improvements in or relating to suspension systems for movable members, such as movingcoil systems of electric measuring instruments - Google Patents

Abstract

1,056,574. Indicating-apparatus; moving coil meters. SANGAMO WESTON Ltd. March 31, 1964, No. 13170/64. Headings G1J and G1Q. A movable element 10 is suspended in a stationary bracket 20 by two tension bands 40 secured by wedges 46, 60 against coplanar faces 44, 50 of cross slots 42, 48 in members 38, 26 so that the major axes of the bands coincide with the desired axis of rotation. After soldering one end of a band 40 to a die cast zinc alloy member 26 through a solder slot 52, a wedge 60 is driven into slot 48. A member 38 is screwed on to a stud 14 on a pivot base 13 cemented to the movable element 10. The other end of the band 40 is wedged in the slot 42 of this member 38. An abutment plate 32, spacer 34 and spring washer 36 are placed on the shaft of an insulating hub 30 preferably of nylon whose tapered end 72 is snapped into a hole 22 in the bracket 20 to be retained by its shoulder 74. Two pins 54 on the member 26 are then wedged into a slot 56 in a tension spring 28, the spring 28 and an end plate 24 are placed over pins 66 on the hub 30 and the pins are hot riveted. The second band 40 is secured in the same way and one of the members 38 clamps a counterweighted pointer 18 to the element 10. In the embodiment shown, the element 10 is a coil moving in the gap between a core 1, including a permanent magnet, and a soft iron ring 2. The nuts 38 are non magnetic and may be die cast brass. The bands 40 are preferably of platinum-nickel alloy for high tensile and shear strength, good electrical conductivity, resistance to corrosion, a linear torque-deflection relationship and low temperature coefficient of resistance. In a sensitive instrument indicating zero to two micro amperes for full scale deflection a band of cross section À002" by À002" is suitable and in a slot 42 0À020" wide a wedge of aluminium alloy 0À0182" wide needs energy of 1 in. lb to drive it home. Electrical connection to the coil 11 is made through spring 28, member 26, band 40, nut 38, and stud 14. The spring 28 may be of beryllium copper, the thickness being chosen to give a tension between 10 and 50 grams as required. The hollow hub 30 limits radial displacement and its flange 70 limits longitudinal displacement of the coil 11. The abutment plate 32 frictionally engages the underside of the flange 70 and an arm 35 facilitates manipulation for zero adjustment.