| 摘要 |
<p>A lockable switch mechanism for use in association with for example where a door of a machine guard must be secured in a locked condition until the guarded machine has stopped operating. A switch plunger (2) is mounted in a housing (1) and is displaceable relative to the housing along a predetermined axis between first and second positions. The switch plunger is displaced as a result of insertion of an actuator which causes a cam to rotate from a datum position, rotation of the cam locking the actuator in engagement with the cam. A locking mechanism is provided for locking the switch plunger in the second position and a switch mechanism is provided which is actuated by movement of the switch plunger between the first and second positions. The locking mechanism comprises at least one first locking member (15) which is biased against a surface of the switch plunger and at least one second locking member (14) which is displaceable between locked and released positions. The surface of the switch plunger against which the first locking member is biased defines a profile in the form of an annular shoulder arranged such that movement of the switch plunger from the second to the first position causes the profile to displace the first locking member. The second locking member when in the locked position prevents displacement of the first locking member by the profile to thereby prevent movement of the plunger from the second to the first position. Thus removal of the actuator (and for example opening of an associated machine guard door) is prevented unless the second locking member has been moved to the unlocked position by for example a solenoid which is energised when the guarded machine is in a safe condition. Furthermore, in the locked position the second locking member makes an electrical circuit to indicate that the switch is locked and intact, and in the event that an opening force is applied to the switch assembly that exceeds its design parameters, the locking member fractures causing aforesaid electrical circuit to be broken and drawing attention to the fact.</p> |
