Patent GB-782013-A (GB)
Title: Improvements in or relating to electromagnetic relays
IPC: H01H51/22
Filed: 1953-11-02
Abstract: 782,013. Electromagnetic relays. GENERAL RAILWAY SIGNAL CO. Nov. 2, 1953 [Dec. 17, 1952], No. 30211/53. Class 38 (5). The " fixed " contacts 64 of a relay are each mounted between two flexible stops 65, 66 and normally engage the upper stop 66 with a certain " trapped " pressure; when a moving contact 67, which is operated by the armature, moves downwards it first engages its contact 64, then carries the contact 64 with it between the two stops, and finally moves slightly further against an increased pressure due to the resistance offered by the stop 65. The stop 65 thus serves to reduce the speed of the armature near the end of its stroke and prevents contact bounce. In the form shown, there are two groups of sets of fixed and moving contacts, each group being moulded at one end into an insulating block 60. The moving contacts 67 of each group are actuated by a toothed member 151 or 152 which passes through a slot 71, Fig. 5, in the contact and embraces a roller 72. The member 151 or 152 also passes freely through slots in the fixed contacts 64, Fig. 4. The members 151, 152 are respectively engaged and operated by the ends of a channel-shaped member 36 which together with an armature 35 and a blade spring 34 is secured to a blade spring 28 itself supported at 29, Fig. 8. The left end of the spring 34 is fixed at 38 and the right end has a sliding engagement with the bracket 10. The result is that the members 35, 36 have a pivotal movement substantially about a point where the springs 28 and 34 intersect. The extent of this movement is limited by adjustable stops 42 which may be of stainless steel and engage the glazed surface of the buttons 46 of " Formica" (Registered Trade Mark). The spring 28 may bias the armature to one position as shown, Fig. 8, or it may tend to hold it symmetrical with regard to the two magnet poles 16, 17 to give an unbiased arrangement. The flux from a permanent magnet 47 passes through the armature and up through the poles 16, 17 and in the unbiased arrangement it holds the armature against that pole 16 or 17 to which it was last moved by the winding 27. The magnetic structure of the relay is shown in Fig. 9, which differs only from Fig. 8 in having a winding 52 on the core 17. When a current passes through the windings 27, 52 it will assist the permanent flux through one of the cores 16, 17 and oppose that through the other and thereby cause the actuation of the armature to its other position, or reinforce its present position. On actuation, the armature is returned to its previous position by a reverse current in the unbiased arrangement and by de-energization of the winding or windings in the biased arrangement. When the armature is biased to one position as in Fig. 8, only one winding, viz. 27, is necessary. In a modification, Figs. 10-16 (not shown), there are two armatures arranged side by side. Each armature controls its own set of contacts and the armatures are biased to take up opposite positions. The coils on the two cores may be connected in series, so that current in one direction operates one armature and current in the other direction operates the other armature. Or the two windings may be independently energized. Each contact block 60 is mounted on the base 5 by a screw 61 and pivotal about a rounded protrusion at its upper end whereby it may be adjustable by a bolt 63 controlling the tension of a spring 62 mounted in the lower end of the block. The fixed springs 64 may have carbon contact points co-operating with movable fingers 67 of silver, palladium or tungsten.