Device for clamping the power end spring in drive devices for electric power switches, especially vacuum power switches

摘要

The invention concerns a device for tensioning the cut-in spring in actuator units for circuit breakers, in particular vacuum circuit breaker, the cut-in spring (7) being designed as a tensioning spring which is in contact with a cam (2) mounted on the cut-in shaft (5) and which can be tensioned both by an electric motor (20) and by a hand-turned shaft (21) through a spur-gear train, the last spur gearwheel (1) also being mounted on the cut-in shaft (5). The aim of the invention is to design a tensioning device in which the spur-gear train operates without overrunning, and reversing of the cam (2) is prevented or limited by the cut-in spring (7). This is achieved by virtue of the fact that the last spur gearwheel (1) in the spur-gear train is disposed over an overrunning bearing (6) on the cut-in shaft (5) in such a way that, when cut-in spring tensioning begins, the cam (2) and hence also the cut-in shaft (5), are carried directly by the last spur gearwheel (1) out of a position in which they are located past the bottom dead centre position (9) of the shaft (5) as the cam (2) rotates upwards, while, during the cut-in phase, the last spur gearwheel (1) is locked in position, when the cut-in shaft (5) turns through bottom dead centre (9), by the overrunning bearing (6) and by the operative connection with the other spur gearwheels in the spur-gear train.