Abstract:
An elevator door restrictor system for preventing an elevator door from being opened unless the elevator car is near a floor landing, utilizing battery backed electronics for sensing the presence of a building landing such that the system will continue to maintain the mechanism in the correct state, either locked or unlocked, even if the elevator car continues to move. Wherein even if the battery backup were to become completely discharged, the mechanism will remain in the last state, either locked or unlocked and prevent the elevator car door from being opened until an authorized person takes the appropriate step to move the car or open the car door.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an elevator door restrictor and more particularly to a system for preventing an elevator door from being opened unless the elevator car is near a floor or landing. 
   BACKGROUND OF THE INVENTION 
   When an elevator car is caused to be stalled between floors of a building, the persons trapped in the car should remain in the stalled car until trained assistance arrives to facilitate evacuation. However, oftentimes in such situations, some of the trapped persons may attempt to force the elevator door open in an effort to evacuate. In certain instances the above situation can be extremely dangerous, such as, for example, when the stalled elevator is not at or close to a landing. In such a situation, trapped persons may attempt to jump from the elevator car or climb to a landing. As a result, the trapped persons may fall into the hoistway or elevator shaft, resulting in injury. 
   Such accidents may be avoided by a door restrictor system that is effective to prevent the opening of the elevator car from inside of the car if the car is at a location away from a landing at a floor of the building. 
   Restrictor systems of the type referred to above generally include a latching or locking member that is typically not accessible from the inside of the elevator car and must be retracted to render the elevator doors operative. These systems may include sensing means which are capable of producing a signal when the elevator car is at or close to a landing and an electrical actuator which retracts the latching or locking member in response to the produced signal. 
   The floor sensing means may be an electric switch mounted on the elevator car and actuated by contact with contacting members mounted in the elevator hoistway and more specifically, may be typically mounted on the elevator guide rail and located along the path of travel of the switch. These types of switches tend to deteriorate from wear and are prone to breakage causing continual inspection and frequent replacement. 
   In recent years door restrictor systems have included photoelectric sensors for detecting the location of an elevator car in respect of the floor landings in a building. An infrared light emitter and appropriate detector are carried by the car and are directed towards the elevator guide rail of the wall of the hoistway. Spaced apart infrared reflecting members on the guide rail or hoistway wall are disposed to reflect infrared radiation from the emitting member when the elevator car is at or close to a landing. Similar systems have employed optical sensors and magnetic sensors to sense the floor landing and lock, or in certain instances, unlock the elevator doors by means of an associated solenoid. 
   These systems have been deemed unacceptable because they default to a certain position when the electrical power is off and associated back-up battery dies. 
   Accordingly, some manufacturers have adapted a restrictor system which defaults to a locked state and others default to an unlocked state. Each of these systems results in a state that will be wrong in some instances. 
   It would be desirable to produce a bi-stable locking system which can remain in either the locked or unlocked state when electrical power is terminated. 
   SUMMARY OF THE INVENTION 
   Consistent and consonant with the present invention, a bi-stable locking system which can remain in either the locked or unlocked state when electrical power is terminated, has surprisingly been discovered. 
   The present invention, in the preferred embodiment utilizes battery-backed electronics for sensing the presence of a building landing. Such a system will continue to maintain the mechanism in the correct state, either locked or unlocked, even if the elevator car continues to move. In a power failure, typically, the elevator car will stop moving within ten (10) seconds. After the expiration of the ten (10) second period, the elevator car should move only if an authorized person is on site to physically lift the brake or open a lowering valve. Even if a battery backup were to become completely discharged, the mechanism will remain in the last state (either locked or unlocked) and prevent the elevator car door from being opened until an authorized person takes the appropriate step to move the car or open the car door. 
   The door restrictor for preventing opening of an elevator car door by a person inside the car when the car is between unlocking zones at landings along the path of travel of the elevator car comprises: 
   a primary source of electrical power; 
   a detecting member in electrical communication with the primary source of electrical power; and 
   an actuated locking device adapted to selectively lock and unlock the elevator car door, an actuation of the locking device controlled by the detecting member, wherein, in the event of a loss of the primary source of electrical power the locking device remains in the selected locked or unlocked position at the time of the loss of the primary source of electrical power. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The above, as well as other objects, features, and advantages of the present invention will be understood from the detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings, in which: 
       FIG. 1  is a is a schematic diagram showing a door restrictor system incorporating the features of the invention; 
       FIG. 2  is a flow diagram showing the normal operation of the energy detecting member of the door restrictor system illustrated in  FIG. 1 ; and 
       FIG. 3  is a flow diagram showing the backup power operation of the energy detecting member of the door restrictor system illustrated in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring now to the drawings, and particularly  FIG. 1 , there is shown generally at  10  a schematic diagram showing a door restrictor system incorporating the features of the invention. The door restrictor system  10  facilitates selectively locking or unlocking doors  12  of an elevator car  14  to prevent the doors  12  from being opened unless the elevator car  14  is in an unlocking zone near a landing. 
   The door restrictor system  10  includes a locking device  16  which is typically connected to an actuator  18 . The locking device  16  can be any conventional locking device such as a spring loaded pin, an electrical or magnetic device, or other mechanical or electromechanical device, for example. It is understood that any conventional actuator  18  can be used such as a solenoid, for example. The actuator  18  is typically electrically operated, although it is understood that other actuator types can be used such as pneumatic, for example, without departing from the scope and spirit of the invention. In the embodiment shown, the actuator  18  is electrically connected to a primary power source  20  and a secondary power source  22 . The secondary power source  22  operates as a backup system to the primary power source  20 , and may be a battery backup system or generator backup system, for example. The primary power source is typically the electrical power supplied to the building in which the elevator is housed. 
   The actuator  18  is controlled by a signal received from an energy detecting member  24 . The energy detecting member  24  can be any conventional detector such as a visible light energy detector, infrared detector, or a magnetic detector, for example. The energy detecting member  24  receives and detects energy from an energy emitting member  26 . The energy emitting member  26  can be any conventional emitter such as a visible light energy emitter, an infrared emitter, or a magnetic emitter, for example. It is understood that other detecting members can be used such as a mechanical detector, which detects the presence or absence of a structural member, for example, could be used without departing from the scope and spirit of the invention. Such detecting members may or may not require an associated emitting member. In the embodiment shown, the energy detecting member  24  is mounted on the elevator car  14  and the energy emitting member  26  is mounted on a shaft wall  28  of the associated elevator hoistway. It is understood that the energy detecting member  24  can be mounted on the shaft wall  28  and the energy emitting member can be mounted on the elevator car  14  without departing from the scope and spirit of the invention. The energy detecting member  24  and the energy emitting member  26  are electrically connected to the primary power source  20  and the secondary power source  22 . 
   In operation, the door restrictor system allows the opening of the elevator car doors by normal automatic operation or by occupants of the elevator car only when an energy path is established between the energy emitting member  26  and the energy detecting member  24 . During normal operation, when the elevator car  14  is at a building landing or floor, energy will be emitted by the energy emitting member  26  and will be detected by the energy detecting member  24 . Thus, a signal will be sent to the actuator  18  to cause the locking device  16  to be placed in the unlocked position, as schematically illustrated in  FIG. 2 . Therefore, the doors  12  of the elevator car  14  will be permitted to open, either automatically, or manually. When the elevator car  14  is not at a building landing, the energy is blocked by a blocking device  30 . The blocking device  30  can be a vane or protrusion, for example, which blocks the energy emitted by the energy emitting member  26 . It is understood that other methods of blocking the energy emitted could be used, such as interrupting power to the energy emitting member  26  to cease emission of the energy. Additionally, it is understood that the actuator  18  could cause the locking device to be placed in the unlocked position in the absence of a signal from the energy detecting member  24 , wherein the energy emitted is blocked when the elevator car  14  is at a building landing. 
   If the primary power source  20  is interrupted or lost, the secondary power source  22  then provides power to the actuator  18 , the energy detecting member  24 , and the energy emitting member  26 . The door restrictor system  10  operates as previously described for normal operation, and as schematically illustrated in  FIG. 3 . It should be noted that if the primary power source  20  is lost, the elevator car may not be operable, and thus caused to remain in the position when the primary power source  20  was lost. The door restrictor system  10  will, however, continue to operate with power from the secondary power source  22  and maintain the doors  12  of the elevator car  14  in a locked or unlocked condition as dictated by the energy detecting member  24  and the actuator  18 . 
   It is possible that the secondary power source  22  will be lost or interrupted. If this occurs, and the signal from the energy emitting member  24  is lost, the actuator  18  will cause or permit the locking device  16  to remain in the same position as when power from the secondary power source was lost. Thus, in the event the locking device  16  was in the locked position since the elevator car  14  was not at a building landing, the locking device  16  will remain in the locked position. Conversely, in the event the locking device  16  was in the unlocked position since the elevator car was located at a building landing, the locking device  16  will remain in the unlocked position. Therefore, as a safety device, the locking device  16  will remain in the desired position, either locked or unlocked, until manually altered by an authorized attendant. So, for example, in the event the elevator car  14  is caused to stop due to a loss of the primary power source  20  at a point not at a floor landing, the secondary power source  22  will be activated and the locking device  16  will be maintained in the locked position. Should the secondary power source be lost, the locking device  16  will maintain the present position and the doors  12  of the elevator car  14  will remain locked until manually unlocked by the authorized attendant. However, in the event the elevator car  14  is caused to stop due to a loss of the primary power source  20  at a point at a floor landing, the secondary power source  22  will be activated and the locking device  16  will be maintained in the unlocked position. Should the secondary power source be lost, the locking device  16  will maintain the present position and the doors  12  of the elevator car  14  will remain unlocked. The following summarizes the various conditions under which the door restrictor system  10  may operate: 
   1. Normal operation (operating under the primary power source  20 )—energy detected as illustrated in  FIG. 2 . 
   2. Loss of the primary power source  20  and operating under the secondary power source  22 —energy detected as illustrated in  FIG. 3 . 
   3. Loss of the primary power source  20  and loss of the secondary power source  22 —the locking device  16  remains in last position prior to loss of power as determined by the energy detecting member  24  and the actuator  18 . 
   From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications to the invention to adapt it to various usages and conditions.