| 摘要 |
1287474 Making electromagnets JUNKERS & CO GmbH 28 Nov 1969 [5 July 1969] 58199/69 Heading B3A [Also in Divisions F2 and H1] Assembly for thermoelectric safety cut-off valve for gas burning appliances, comprises a U-shaped electromagnet core 22 fixed by its base and having pole faces on the free ends of the limbs 222, 223 accurately machined in one plane. A co-operating armature plate 21 is connected to a stem 15 of the valve member 12. To enable accurate pole surfaces in one plane to be achieved during machining, e.g. lapping, operations, and prevent inaccuracy owing to vibration, the fundamental oscillation frequency of the fixed unwound core is arranged to be not less than twenty-five kilocycles per second, preferably 30 kc/s. The corresponding frequency of each limb separately is not less than 30 kc/s., preferably 34 kc/s. The arrangement enables the core to be effectively of small dimensions, e.g. the volume of each limb may be not more than 70 mm.<SP>3</SP> or 60 mm.<SP>3</SP>. The gap between the limbs is less than the thickness of one limb. The core may be formed by cold extrusion. As shown, the core is fixed to a base 23 carrying a contact head 25 and an inner casing 27 providing a guide for the valve stem 15. The valve is re-set by a push-button (29), Fig. 1 (not shown). |
