Overspeed Governor

     Elevator safety equipment includes an overspeed governor for restricting elevator car movement when a predetermined speed is exceeded. Overspeed governors include a switch that opens when the elevator reaches a predetermined velocity such as 110% of related Speed . When the switch opens, power is removed from the machine motor and brake. A braking mechanism, actuated in response to movement of the elevator car by motion transmission means, then impedes the motion of the elevator car. The switch remains open, and the elevator remains inoperable until the switch is manually reset.
   

How it Works

     The system includes a governor that is responsive to elevator car speed through conventional coupling means such as a governor sheave coupled to a rope that is attached to an elevator car, whereby the rope transmits elevator car speed to the governor. When a predetermined speed is exceeded conventional actuation means, such as centrifugal flyweights, trigger a first set of switches and, if the car speed continues to increase, cause actuation of conventional mechanical means to impede elevator car movement. The first set of switches  may comprise one switch or any other number of switches, depending on various factors such as the degree of safety redundancy desired or the number of different components dependent upon overspeed conditions. For example, a "safety chain" electrically linking various components and associated switches may be implemented, whereby the opening of one switch renders the system inoperable. The first switch  of the first set, for example, may be for the purpose of tripping the remote overspeed switch while the second switch  of the first set may be directly in the safety chain.
     When the first set of switches  are tripped, they cause tripping of a second set of switches. The first set of switches  may, for example, trip the second set of switches by causing power loss when a contact is broken in response to first switch tripping. The second set of switches  is remotely located, preferably in a convenient and easily accessible location such as a control panel in an elevator landing or in a building managers office or a security office