Elevator car and counterweight safety

Description
FIELD OF THE INVENTION
This invention relates to a braking device for an elevator and, more particularly, to a braking device including a unitary spring and housing
BACKGROUND OF THE INVENTION
Elevators are provided with various forms of braking devices for braking an elevator car or counterweight moving in an elevator hoistway. Among these is a device referred to as a "safety", used in emergency situations when other braking devices may have failed or are not operable. The safety is used for stopping and sustaining the entire elevator car or counterweight with its rated load from a tripping speed determined using a governor.
A conventional safety for an elevator car or counterweight that is guided on a vertical guide rail uses wedge devices for braking. Particularly, a resilient spring holds wedge guides on opposite sides of the rail. A wedge is disposed between each wedge guide and one side of the rail. An actuating mechanism is operable to force the wedges into the wedge guides when a tripping speed is exceeded. The engagement between the wedges and the wedge guides forces the wedges into the rail to produce a clamping force to stop the elevator car or counterweight. Such a structure requires additional components to provide the spring forces. Also, the safety typically includes rollers disposed between the wedges and the wedge guides.

BACKGROUND OF THE INVENTION
    Elevators are provided with various forms of braking devices for braking an elevator car or counterweight moving in an elevator hoistway. Among these is a device referred to as a "safety", used in emergency situations when other braking devices may have failed or are not operable. The safety is used for stopping and sustaining the entire elevator car or counterweight with its rated load from a tripping speed determined using a governor.
A conventional safety for an elevator car or counterweight that is guided on a vertical guide rail uses wedge devices for braking. Particularly, a resilient spring holds wedge guides on opposite sides of the rail. A wedge is disposed between each wedge guide and one side of the rail. An actuating mechanism is operable to force the wedges into the wedge guides when a tripping speed is exceeded. The engagement between the wedges and the wedge guides forces the wedges into the rail to produce a clamping force to stop the elevator car or counterweight. Such a structure requires additional components to provide the spring forces. Also, the safety typically includes rollers disposed between the wedges and the wedge guides.
The present invention is directed to improvements in braking devices for elevators.
SUMMARY OF THE INVENTION
In accordance with the invention there is provided a braking device for an elevator including a unitary safety housing.
Broadly, there is disclosed herein a braking device for an elevator having a governor that actuates above a tripping speed for braking an elevator car or counterweight that is guided on a vertical guide rail. The braking device includes a unitary safety housing attached to the elevator car or counterweight and at least partially surrounding the guide rail. The safety housing is expandable and has opposite, facing wedge guides on opposite sides of the guide rail. A pair of wedges are included, each being received between the guide rail and one of the wedge guides. An actuator is linked with a governor and the wedges for driving the wedges into the safety housing, forcing the safety housing to expand and produce a clamping force on the guide rail, in response to actuation of the governor.
In accordance with one aspect of the invention, the safety housing comprises a C-shaped housing receiving the guide rail, the safety housing including a plurality of outer ribs enabling the safety housing to operate with a controlled spring rate. The safety housing expands a maximum of about one-quarter inch. The safety housing is formed as an investment casting. The wedge guides comprise U-shaped pockets in the safety housing.
In accordance with another aspect of the invention the braking device includes a pair of inserts, each being sandwiched between one of the wedge guides and the wedge received therein, the insert having a low coefficient of friction. The plastic inserts have radiused back surfaces received in the pockets, allowing the wedges to pivot to maintain even pressure along the faces of the wedges as they engage the guide rail. The inserts comprise plastic inserts.
In accordance with a further aspect of the invention, the safety housing is loosely, pivotally attached to the car or counterweight, enabling the safety housing to selfcenter during actuation.
In accordance with another embodiment of the invention, the braking device includes a safety housing attached to the elevator car or counterweight and at least partially surrounding the guide rail. The safety housing includes opposite, facing wedge guides on opposite sides of the guide rail. A pair of wedges are included, each being received between the guide rail and one of the wedge guides. A pair of plastic inserts are included, each being sandwiched between one of the wedge guides and the wedge received therein. The inserts have a low coefficient of friction. An actuator is linked to the governor and the wedges for driving the wedges into the safety housing to produce a clamping force on the guide rail in response to actuation of the governor.
Further features and advantages of the invention will be readily apparent from the specification and from the drawing.