GB913728A - Motor starting relay - Google Patents

Abstract

913,728. Electromagnet relays. RANCO Inc. May 8, 1961 [June 15, 1960], No. 16577/61. Class 38 (5). The effective leverage of a bow-spring engaging an armature of a relay close to its pivot and biasing said armature away from a solenoid, is reduced when the armature moves to actuate a switch mechanism on being attracted by the said solenoid. A contact-arm 21 is flexed so as to separate moving and fixed contacts 22, 14 respectively, by the movement of a relay armature 24 the end portion 29 of which has a plastic bumper 30 possibly retaining graphite or some anti-friction material. The armature has a portion reduced in width to form two shoulders 26 which engage in V- bearings 28 formed in a rearwardly projecting portion of a bracket 25 having a central opening through which the reduced armature portion projects. A flat bow-spring 32, the lower end of which is located in a recess 33 formed in a tongue 34 of an L-shaped frame 18, and the upper which is in an armature recess 35, biases the armature into its raised position so that it engages a stop 31. The distance between the walls of the recesses 33 and 35 is such as to maintain the spring 32 bowed and its ends to the left end of recess 33 and the right recess 35 respectively, when the spring leverage biasing the armature is proportional to a length shown as f. When the armature is brought into engagement with a solenoid 40, the spring leverage is reduced due to a reduction in the perpendicular distance of the armature pivot 28 to the line of action of the force produced by the spring, to a valve proportional to f<SP>1</SP>, and hence the armature biasing force is reduced by a value proportional to f-f<SP>1</SP>. The solenoid 40 is connected across a motor starter winding, not shown, so as to respond to the voltage across it, when the then reduced armature biasing force ensures that the relay armature remains actuated during the running condition of the motor, and thus keep interrupted a starter winding circuit which is series connected with the contacts 22 14. The action of member 30 on the contact arm 21 is such as to impart a peeling action to the contact 22, thus tending to break possible contact welds.