Abstract:
An electric door operator for opening and closing one or a spaced pair of transit vehicle passenger doors for being mounted over an opening for the doors. A rotatable input shaft has an electric motor secured to the input shaft for driving the input shaft, a worm centrally positioned on the motor shaft, and an electric brake mounted to the input shaft at an end opposite of the electric motor. A drum cam lifts a pinion from a worm gear disconnecting the worm gear from an output gear train in an emergency.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to door operators for doors on transit vehicles such as buses and trains. Some vehicle doors have a single panel mounted at an outside edge of the door opening. Many vehicle doors have two panels, each mounted at an outside edge of the door opening. The panels usually swing outward to permit entrance or exit of passengers. Often, the doors are caused to open or close with a pneumatic cylinder or electric motor and a well known teeter assembly mounted over the top of the door opening. The space available for mounting the door operator over the door opening is often limited. Automatic opening and closing of the doors is controlled by the vehicle driver at stops for picking up and discharging passengers. It is an essential feature of door operators that the doors cannot be pushed open by passengers leaning against the doors, for example, while the vehicle is moving. However, in an emergency there must be a manual release that can be operated by a passenger. Generally, passengers must be able to operate the manual release with no more than 20 pounds pull force. 
     2. Description of Related Art 
     U.S. Pat. No. 5,332,279 entitled “Power Door Operator for Multi-Passenger Mass Transit Vehicles” discloses an electric door operator and illustrates the manner in which the spaced doors are rotated open and closed by the action of the teeter assembly connected to drive rods and pivot levers fixed to the vertical door shafts on which the doors are mounted. FIG. 1 of the &#39;279 patent is incorporated herein by reference. This application is directed to an improved system for driving the teeter assembly with an electric motor. 
     SUMMARY OF THE INVENTION 
     An electric door operator for opening and closing one or a spaced pair of transit vehicle passenger doors comprises a structure for being mounted adjacent an opening for the doors. A rotatable input shaft is mounted to the structure with an electric motor secured to the input shaft for driving the input shaft, a first stage pinion positioned on the input shaft, and an electric brake mounted to the input shaft. An output shaft is rotatable relative to the structure and has a teeter mounted thereon with journal bearings at at least one end thereof for engagement with drive bars for opening and closing the doors. An output gear is fixed to the output shaft for driving the output shaft. 
     A first stage shaft is rotatable relative to the structure and has a first stage gear fixed to the shaft in a position to engage the first stage pinion on the input shaft. A second stage pinion with a sliding connection to the first stage gear shaft enables axial movement of the second stage pinion between engaged and disengaged positions with the first stage gear. 
     A second shaft is rotatable relative to the structure. A second stage gear is fixed to the second shaft and arranged for engagement with the second stage pinion. A third stage pinion is fixed to the second shaft for directly or indirectly transferring torque to the output gear fixed to the output shaft. 
     A drum cam shaft is rotatable relative to the structure. A drum cam is axially movable relative to the drum cam shaft. A pin extending from the drum cam shaft engages a cam slot in the drum cam. A lifting plate is fixed to the drum cam and extends to engage a slot in the first stage pinion to move the first stage pinion between engaged and disengaged positions. A disengagement lever and an engagement/disengagement cam are fixed to the drum cam shaft. A pin extends from the disengagement lever. 
     A mechanical release is fixed to a slotted end piece. The aperture in the slotted end piece receives the pin extending from the disengagement lever. When the mechanical release is actuated, the drum cam shaft rotates the pin extending from the drum shaft and the drum cam moves to lift the lifting plate and first stage pinion to the disengaged position. 
     Briefly, according to a specific embodiment of this invention, there is provided an electric transit door operator for opening and closing a spaced pair of transit vehicle passenger doors. A housing is provided with a base plate for being mounted over an opening for the doors. A rotatable input shaft is mounted over the base plate and parallel thereto. An electric motor is secured to the input shaft for driving the input shaft; a worm is centrally positioned on the input shaft; and an electric brake is mounted to the input shaft at an end opposite the electric motor. 
     An output shaft is rotatable relative to the housing and has a teeter mounted thereon with journal bearings at opposite ends thereof for engagement with drive bars for opening and closing the doors. A gear is fixed to the output shaft for driving the output shaft. 
     The input shaft is rotatable perpendicular to the output shaft and has a worm fixed to the input shaft in a position to engage a worm gear. A second stage pinion with a sliding connection to the gear shaft enables axial movement of the second stage pinion between engaged and disengaged positions, 
     A second shaft is rotatable parallel to the output shaft. A second stage gear is fixed to the second shaft and arranged for engagement with the second stage pinion. A third stage pinion is fixed to the second shaft. The third stage pinion directly or indirectly transfers torque to the output gear fixed to the output shaft. 
     A drum cam shaft is rotatable on a drum cam shaft parallel to the output shaft. The drum cam is rotatably and axially movable relative to the drum cam shaft. A pin extends from the drum cam shaft engaging a cam slot in the drum cam. A lifting plate is fixed to the drum cam and extends to engage a slot in the second stage pinion to move the second stage pinion between engaged and disengaged positions. A disengagement lever and a disengagement cam are fixed to the drum cam shaft. 
     A cable sheath bracket fixes the sheath of a release cable to the base plate. A release cable is fixed to a slotted end piece. The aperture in the slotted end piece receives the pin extending from the disengagement lever. A return spring urges the slotted end piece away from the cable sheath bracket. When the release cable is pulled, the drum cam shaft rotates the pin extending from the drum cam shaft and the drum cam moves to lift the lifting plate and second stage pinion to the disengaged position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and other objects and advantages will become apparent from the following detailed description made with reference to the drawings in which: 
         FIG. 1  is a front view in partial perspective of an electric door operator according to this invention; 
         FIG. 2  is a side view in partial perspective of an electric door operator according to this invention in which the housing has been removed to better observe the moving parts; and 
         FIG. 3  is an end view in perspective of an electric door operator according to this invention with the housing and brake removed to better observe certain of the moving parts. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to  FIG. 1 , a structure or housing  12  supports or encloses most of the moving elements of the door operator. A housing has a base portion to which the moving elements are indirectly or directly mounted. The teeter  14  is mounted on an output shaft  16 . The teeter  14  has a drive arm  15  mounted to the output shaft  16  with journals  18 ,  20  at one or both ends for receiving drive rods (not shown). The teeter can rotate both clockwise and counterclockwise to operate the drive rods. Mounted on opposite sides of the housing  12  are electric motor  22  and electric brake  24  connected to each end of an input shaft  26 . The electric motor can be controlled to rotate either clockwise or counterclockwise. 
     Referring now to  FIGS. 2 and 3 , the electric motor  22  is coupled to the input shaft  26  at one end and to the electric brake  24  mounted to the input shaft, for example, at the other end. The electric brake is spring biased in the braking position with an electric release. An electromagnetic coil (not shown) inside electric brake  24  releases a spring actuation such that when no electric power is available the motor shaft is locked in position. Thus, a passenger leaning on a door will not force it open. Electric power is only required to open or close the doors and not to maintain the doors closed. Other fail safe braking systems can be used. 
     When the electric brake  24  is released, the electric motor  22  can turn the input shaft  26  either clockwise or counterclockwise. The motor may be brushless in one embodiment. 
     Mounted on the input shaft  26  is worm  28 . A gear shaft  30  is mounted rotatable, and preferably, perpendicular to the input shaft  26 . A worm gear  32  is fixed to the gear shaft  30  in a position to engage the worm  28 . A second stage pinion  34  has a sliding connection on the gear shaft  30  enabling axial movement of the second stage pinion  34  between engaged and disengaged positions with the worm gear  32 . Under normal conditions, the worm gear  32  is mounted to the lower portion of the gear shaft  30  and engages the second stage pinion  34  with pins  33  (see  FIG. 2 ) or the like. 
     This arrangement allows for the emergency release of the input shaft  26  from the teeter  14  permitting manual opening of the door in an emergency. Alternatively, second stage pinion  34  may have one or more arm extensions received in one or more recesses in worm gear  32 . With such arrangements, the electric door operator may be permitted to selectively engage the second stage pinion with respect to the worm gear, and thus, disengage the door operating mechanism entirely from the doors. 
     A second shaft  36  is mounted rotatable, preferably parallel, to the gear shaft  30 . A second stage gear  38  is fixed to the second shaft  36  and arranged for engagement with the second stage pinion  34 . A third stage pinion  40  is fixed to the second shaft  36 . Said third stage pinion  40  is for directly or indirectly transferring torque to the output gear  48  fixed to the output shaft  16 . In the particular embodiment illustrated in the drawings, there is a third shaft  42  having a third stage gear  44  fixed thereto for engagement with the third stage pinion  40  on the second shaft  36 . A fourth stage pinion  46  is fixed to the third shaft  42  for engagement with a fourth stage or output gear  48  fixed to the output shaft  16 . An advantage of this embodiment is that the gear ratios may be altered to vary the output torque available given the electric motor selected. A particular advantage of this embodiment is that the frictional forces between the second stage pinion  34  and the first stage gear  38  at the time of disengagement by axial movement of the first stage pinion can be minimized. 
     A drum cam shaft  50  is rotatable perpendicular to the housing  12 . A drum cam  52  slides over the drum cam shaft. A pin  54  extends from the drum cam shaft  50  engaging a cam slot  56  in the drum cam. A lifting plate  58  is fixed to the drum cam  52  and extends to engage a circumferential slot  56  in the second stage pinion  34  to move the second stage pinion between engaged and disengaged positions. The cam slot  60  in the cam drum may have dwell portions  60 A and  60 B at each end thereof. In this case, the drum cam slot has a cam lifting portion having a face that extends circumferentially and axially and at the ends thereof has substantially circumferential dwell portions. As drum shaft  50  is rotated, the pin  54  travels from one dwell portion to the other either raising or lowering the drum cam  52  as the pin rides in the slot. The dwell portions  60 A and  60 B enhance engagement and reengagement of the first stage pinion and the worm gear by allowing some additional rotation without lifting or lowering the drum cam. In the illustrated embodiment, ball bearing  62  is press fit on the drum cam shaft  50  and abuts the housing  12  to axially constrain the drum cam shaft. Alternatively, a slot and retainer (not shown) and/or snap ring may be positioned on the drum cam shaft with a bearing or bushing to restrain axial movement of the drum cam shaft. 
     Referring again to  FIG. 1 , a disengagement lever  64  and engagement/disengagement cam  66  are fixed to the drum cam shaft. A pin  68  extends from the disengagement lever  64 . A cable sheath bracket  70  is provided for fixing the sheath  72  of a release cable  74  to the housing  12 . The release cable is fixed to a slotted end piece  76 . The aperture  78  in the slotted end piece receives the pin  68  extending from the disengagement lever  64 . A return spring  80  urges the slotted end piece  76  away from the cable sheath bracket  70 . 
     When the release cable  74  is pulled, the drum cam shaft  50  rotates the pin  54  extending from the drum cam shaft  50  and the drum cam  52  moves to lift the lifting plate  58  and second stage pinion  34  to the disengaged position. 
     The engagement/disengagement cam  66  has spaced engagement cam surface portions  66 A and disengagement cam surface portions  66 B. An electrically operated actuator, for example, a solenoid  82  is fixed to the housing  12  for pulling a spring biased stop  84  away from the disengagement lever such that when the release cable is pulled, the slotted end piece  76  rotates the disengagement lever  64  and the rotation of the disengagement lever rotates the engagement/disengagement cam allowing the spring biased stop  84  to enter the disengagement cam surface portion preventing return of the first stage pinion to the engaged position until the solenoid is activated. Typically, actuation of the solenoid is only controlled by the vehicle operator. 
     Once the cable is released but before the disengagement lever  64  is rotated out of the emergency disengaged state, the cable may be spring biased by return spring  80  to return to the pre-emergency position urging the slotted end piece  76  to the opposite end of the aperture  78  (slot). Although the spring  80  may urge rotation of the engagement lever to the engaged position, the spring biased stop  84  in contact with the disengagement cam surface portion  66 B prevents such rotation. Accordingly, the aperture in the slotted end piece  76  allows the cable to move back to its pre-emergency position but the worm gear  32  and second stage pinion  34  remain decoupled. The aperture (slot)  78  further allows a secondary drive to actuate the emergency release. 
     In one embodiment for transit bus doors, the decoupling of the electric door operator would allow the transit doors to freely rotate. Accordingly, in the emergency release state, the current design minimizes back-drive force by decoupling the spur gears in from the worm gear. 
     In order to return the transit doors to an operational state, the solenoid  82  is used to retract the stop  84  to allow the disengagement lever  64  to rotate back to the operational position. Such rotation of the lever is accomplished by a torsion spring  86  around the drum cam shaft urging the drum cam into the engagement position thus moving the second stage pinion into engagement with the worm gear. Thus second stage pinion  34  may be reengaged with the worm gear  32  once rotated into a position for engagement. This positioning may be accomplished by dithering of the motor  22 . 
     According to a preferred embodiment, sensors are provided to detect the door open and/or closed positions of the teeter  14  and to detect when the worm gear  32  and second stage pinion  34  have been reengaged. As seen in  FIG. 1 , a target tab  88  rotates with the output shaft between sensors (for example, magnetic or optical sensors)  90 ,  92  enabling detection of the open and closed positions of the teeter  14  (and consequently the transit doors). Also as seen in  FIG. 1 , a target tab  94  rotates with the drum cam shaft  50  and is aligned with sensor  96  when the disengagement lever is in the engaged position. This is useful in order to command the discontinuance of motor dithering used to urge reengagement of the worm gear and the second stage pinion. The sensors could be located at various other positions and could be replaced with limit switches. 
     LIST OF REFERENCE NUMERALS 
     
         
           12  structure 
           14  teeter 
           15  drive arm 
           16  output shaft 
           18  journal 
           20  journal 
           22  motor 
           24  electro/mechanical brake 
           26  input shaft 
           28  first stage pinion (worm) 
           30  gear shaft 
           32  first stage gear (worm gear) 
           33  pin 
           34  second stage pinion 
           36  second shaft 
           38  second stage gear 
           40  third stage pinion 
           42  third shaft 
           44  third stage gear 
           46  fourth stage pinion 
           48  fourth stage gear 
           50  drum cam shaft 
           52  drum cam 
           54  pin 
           56  slot 
           58  lifting plate 
           60  cam slot 
           60 A dwell portion 
           60 B dwell portion 
           62  ball bearing 
           64  disengagement lever 
           66  engagement disengagement cam 
           66 A engagement cam surface 
           66 B disengagement cam surface 
           68  pin 
           70  bracket 
           72  sheath 
           74  cable 
           76  slotted end piece 
           78  aperture (slot) 
           80  return spring 
           82  solenoid 
           84  stop 
           86  torsion spring 
           88  target tab 
           90  sensor 
           92  sensor 
           94  target tab 
           96  sensor