Abstract:
An electromechanically actuated safety lock mechanism particularly suited for elevator hall doors, dumb waiters, and similar lift mechanisms and other applications. A door lock and switch comprises a fixed contact member that is attached to a movable door and a movable locking mechanism attached to a door jamb or second moving door. The locking mechanism may include an involute gear and star wheel, a pawl constrained by a torsion spring and an electromechanical device for actuating the pawl.

Description:
FIELD OF THE INVENTION 
     This invention relates to interlocks generally, and is more particularly related to electromechanically operated locks that are useful in lifting devices such as elevators, lifts and dumb waiters. 
     BACKGROUND 
     Elevator landing door locks, which are commonly referred to as interlocks, are provided in elevator systems to lock hall doors against movement when the elevator car is not in position to receive loads. The interlock is a safety device that prevents access to an elevator shaft through the doors when the car is not present in the doorway. The interlock also prevents the elevator cab from moving before the door is closed and locked. Safety locks are required by numerous building safety codes. 
     Interlocks in common use with lifting devices are controlled by solenoids. While generally dependable, solenoids require a large coil to have sufficient power to engage and hold the locking mechanism in the ‘open’ position. The size of the coils that comprise these systems require that interlocks be bulky and unsightly when compared to most residential door locking mechanisms. These locks are commonly ‘normally closed’, such as by spring biasing, and rely on being energized to maintain an ‘open’ position. This design can prevent the hall door from being closed if the hall door is open and there is a power failure, since gravity moves the interlock into the ‘closed’ position, preventing the door from reclosing. There is a need for a device that will permit easy locking of the door if the operating device is not powered. 
     SUMMARY OF THE INVENTION 
     The present invention is a lifting device door latch and switch mechanism that permits a lifting device, such as an elevator, to move only when the car door is closed and locked, preventing access to the elevator shaft when the elevator car is not at the floor level of the door of the shaft. The device provides a positive holding mechanism that prevents inadvertent movement of the door once locked. A self-latching device locks access to hall doors in the event of loss of power to the device. The device may be used on multiple floor levels, and when any one of the doors is open, movement of the elevator is disabled. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded view of the latch, locking mechanism and cover of an embodiment of the invention. 
         FIG. 2  is an isometric view of a latch and locking mechanism of an embodiment of the invention showing an ‘open’ position ( FIG. 2A ) and a ‘closed’ position ( FIG. 2B ). 
         FIG. 3  is a sequence of isometric cutaway views of the back of a latch of an embodiment of the invention progressively depicting the interaction of the star-wheel, gear, pawl and the keeper in self-latching action. 
         FIG. 4  is an isolation of a drive shaft that may be used with the invention. 
         FIG. 5  is an isolation of a servo motor that may be used with the invention. 
         FIG. 6  is an isolation of a torsion spring that may be used with the invention. 
         FIG. 7  is an isolation of a back side of a gear that may be used with the invention. 
         FIG. 8  is an isolation of a front side of a gear that may be used with the invention. 
         FIG. 9  is an isolation of a pawl that may be used with the invention. 
         FIG. 10  is an isolation of a keeper that may be used with the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of illustration, the electrical components that are associated with this device are not shown in detail. The device is incorporated into known lifting devices, and is connected to a power source, signaling devices and switching devices as used with lifting devices. 
     Turning to the drawing figures, in a preferred embodiment, gear  2  is supported on the housing back plate  8 , and is rotatable about a stationary vertical pin  11 , which acts as an axle.  FIGS. 2A and 2B . The gear is constrained in the ‘locked’ position by spring biasing, which may be provided by a torsion spring  4 . The gear  2  may be constructed from a variety of materials, and in one embodiment is formed of a hard resilient material such as Acetal. The gear as shown has a central bore that receives pin  11 , allowing the gear to rotate about the pin. The gear may be of a daisy shape as shown in the drawing figures, with angularly spaced teeth  14 , and having intervening pockets that may be formed on the top side around the periphery of the gear  2 .  FIG. 8 . The pockets are preferred to be formed and adapted to a size and shape that accepts the tooth  16  of the keeper  1 . In this embodiment, a bottom portion  36  of the gear  2  is formed in a star or pinwheel shape having teeth  34  and pockets corresponding to the teeth of the top gear.  FIG. 7  and  FIG. 8 . However, the lower gear may be provided as a separate part coupled to the top part of the gear  2 , preferably with a square axle. 
     The pawl  3  is similarly preferred to be constructed with a bore offset from the center to provide a pivot point and likewise secured with a pin  11  allowing the pawl to pivot. The tail  13  of the pawl may be shaped to correspond to and match the curved face of the star wheel, so that when it rests on the convex surface  35  ( FIG. 7 ) the angular tip of the tooth  34  ( FIG. 7 ) engages the concave face  38  of the tail. The pawl  3  is restrained towards the gear by spring biasing such as torsion spring  4 , forcing the pawl and star wheel to engage, and preventing the gear from moving in a counterclockwise direction. 
     An electrically actuated or electromechanical actuator, such as a servo motor  5  or a solenoid, may be positioned with a an end of the drive shaft  6  attached to the tail of the pawl  3 . The opposite end of the drive shaft may be connected to a rotatable member  44  that is rotated by the servo sufficiently to resist the spring biasing of spring  4  and cause the drive shaft to lift the pawl away from the star wheel. When the device is energized it forces the pawl to move away from the star wheel, allowing the gear to turn freely, and allowing the keeper to retract from the gear pocket into the ‘open’ position. When the actuator is de-energized, spring  4  urges the pawl to return to the ‘closed’ position. Thereafter, the keeper  1  re-engages the gear while the pawl  3  is engaged with the star wheel  36 . The shape of the star wheel  36  and the offset pivot of the tail of the pawl  3  are such that the pawl is forced to ride along the curved face  35  of the star wheel  36 .  FIG. 7 . This action allows the gear  2  to turn in a clockwise direction accepting the pinion on the keeper and holding it securely in the ‘closed’ position. The action is illustrated in the progressive sequence shown in  FIG. 3 . 
     The protective cover  21  ( FIG. 1 ) may be formed to slip fit over the base  8  to form an enclosure or enclosed housing in which the spring biased and pivoting pawl and the electrically operated actuator can be contained. The protective cover may have openings  40 ,  42  formed to correspond with the engagement of the keeper  1  and to provide access to the manual releases,  26 ,  27 . Manual release  26  is accessed from inside the car while handle  27  of the pawl may be accessed through an opening in the hallway door. These releases are positioned relative to the pivot point and the cover to allow manual pivoting and release of the pawl from the gear  2 . As shown, the cover  21  is secured with screws  24 . 
     The resulting interlock provides an electro-mechanical means for locking the door closed. The keeper is attached to a hall door and the backing plate  8  and associated devices are attached to the hall door jamb. Signaling devices associated with the elevator or lifting device control system control the actuator or servo. The resulting interlock holds the hallway door secure, and prevents the interruption of the safety signal. Interruption of the safety signal causes failure of the call system and prevents use and access to the car. The devices also provides means for locking the door in the event of a power interruption, but allows the door to close and lock regardless of the location of the locking mechanism at the time of the power interruption. 
     The embodiment of the invention as shown utilizes a ratcheting mechanism permitting motion in one direction but not the other. In this ratchet mechanism, the rotary motion about the axes are enabled for relative motion in one direction, but the pawl engages the star wheel to prevent relative motion in the other direction. 
     The electromechanical device of the invention may utilize either AC or DC as a power source. The device may be provided to work with any elevator system or lifting system that relies on a door latch and which can receive and transmit an electrical signal from any type of controller. 
     A manual override of the lock for emergency use may be provided. In the event of a power loss a battery back-up power supply may be provided to release the door lock and allow passengers to exit the elevator car. There is also an additional provision for a radio controlled remote activation of the lock for emergency release of the lock. 
     The invention provides a universal type lock that is not left or right handed and does not require internal reconfiguration. This feature reduces the costs of stocking specific locks for doors that open to the left or right. Further the installer or repairman is not required to reconfigure the internal components of the lock, enabling easy configuration in the field and reducing opportunities for errors in the installation/repair of locks. 
     The invention provides a mechanism that can be readily manufactured in a variety of means such as tamped metal, castings in metal, plastics or composites or CNC machined parts to suit the manufacturer&#39;s preferences and processes.