ENERGY ABSORBING AND PRESSURE APPLYING ARRANGEMENT FOR ELECTRICAL CONTACTS

摘要

ENERGY ABSORBING AND PRESSURE APPLYING ARRANGEMENT FOR ELECTRICAL CONTACTS An energy absorbing and contact pressure applying arrangement which minimizes bounce of a movable electrical contact upon engagement with a stationary or fixed electrical contact. In an illustrated embodiment, an armature member is attracted by an electromagnet means to draw the movable contact into engagement with the fixed contact. The movable contact engages the fixed contact before the armature has completed its travel into magnetically sealed engagement with the core of the electromagnet means. During the additional increment of travel necessary for the armature to move into magnetically sealed relation to the core of the electromagnet means, means connected to the moving armature causes compression of an energy absorbing and contact pressure applying device against the carrier arm on which the movable contact is mounted. The energy absorbing and contact pressure applying arrangement may be a composite spring comprising a helical metal wire coil spring embedded in a suitable energy absorbing material such as an elastomeric material, preferably silicone rubber, which dampens the natural resiliency or tendency to bounce of the metal wire spring. The resiliency of the metal wire spring itself is a significant factor in contact bounce. The energy absorbing device greatly reduces, as compared to the prior art, the duration of the time interval during which the movable contact bounces relative to the fixed contact due to the impact of closure, to thereby greatly reduce the duration of arcing and in many instances substantially reducing the amplitude and amount of the arc current between the contacts during the bounce period, with consequent reduction in erosion of the contacts. The reduced duration of the bounce period, in accordance with the present invention, also reduces mechanical wear on the contacts. The advantages of the invention just described result in a substantial increase in contact life. In a modified embodiment which operates upon the same principle as hereinbefore described, movement of the movable contact into engagement with the fixed contact and compression of the energy absorbing device against the movable contact are both imparted by a magnetic plunger which is axially movable in an electromagnetic solenoid.