GB740262A - Electric contact devices having magnetic means for increasing the contact pressure - Google Patents

Abstract

740,262. Electromagnetic relays. GOSSEN & CO.,GES., P. Feb. 13, 1953 [Feb. 16, 1952], No. 4125/53. Class 38(5) A moving coil relay in which a contact operating arm biased by a return spring carries an armature co-operating with a magnet to increase the contact pressure, is characterized by magnetic screening means, so arranged that the magnet is unable to influence the armature until the current in the moving coil attains the value at which the contacts are to be closed, a very small further movement of the arm exposing the armature to the influence of the magnet so that the contacts are closed with a sufficient pressure. According to Fig. 5, a soft iron screen 8 is slotted at 9 to permit movement therethrough of an armature 6 on an arm 3 controlled by a moving coil 1. When the armature passes outside the screen, it is influenced by an electromagnet 7 and contacts 10, 10<SP>1</SP> supported by resilient arms 4, 4<SP>1</SP> are firmly closed. Another arrangement, Fig. 8, comprises a pot electromagnet 12 having its magnetic circuit closed by a hemispherical end 14 which acts as a screen by keeping the stray field at a minimum. Hence the armature 6 is not affected by the electromagnet 12 until it enters a slot 15 formed in the end 14. To provide a degree of damping for the arm 3 in the region where it is under the influence of the contact-pressure producing magnet, the moving coil may carry an additional winding having its ends connected through a rectifier and resistance (Fig. 11 not shown). The damping winding is so positioned that it is not affected by the magnet 2 of the coil 1 until the latter has turned through a certain angle. The recti- 'fier ensures that the damping action is present only when the armature moves away from the magnet 7. Fig. 12 shows an arrangement for automatically de-energizing the magnet when the contacts are closed to permit the arm 3 to return from its contact-making position without the application of additional restoring forces. Two magnets 103, 104 and two sets of contacts 101, 105 are provided corresponding to the maximum and minimum positions of the arm 3. The maximum magnet 103 is initially energized over contacts 106 of a relay 102. In response to a maximum value of the current in the coil 1, arm 3 closes contacts 101 and relay 102 is energized whereby magnet 103 is de-energized, minimum magnet 104 is energized across contacts 107, and a holding circuit for the relay 102 is completed across contacts 107 through a resistance 23; also, contacts 108 complete an external circuit connected to 117, 118. If now the current in the coil 1 decreases the arm 3 is returned by its spring and when the current attains its minimum value the contacts 105 are closed whereby relay 102 is short-circuited. Thus the magnet 104 is deenergized by the opening of contacts 107 and the magnet 103 energized through contacts 106 and the arrangement is then in its initial condition.