BETAETIGUNGSSOLENOID

The solenoid actuator comprises a slider 28 including a permanent magnet 36. When the electromagnet 12 is activated, it repels the permanent magnet, thereby moving the slider from its first position as shown towards a second position in which the permanent magnet is attracted to a mass of ferro-magnetic material 38 located adjacent the second position. In a preferred embodiment, the poles of the slider permanent magnet are co-axially aligned with the coil and core 18 of the electromagnet. In an alternative embodiment, the mass of ferro-magnetic material may be eliminated. On de-energisation of the electromagnet the slider returns to its first position. Alternatively the actuator may have a bistable operation by increasing the size of the mass 38 so that it attracts the permanent magnet 36 to latch the slider in its second position when the electromagnet is de-energised. A reed conductor 40 may be attached to the slider for cooperation with contacts 42, 44.