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BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT  
         [0001]    The present invention relates to a side sliding door apparatus having sliding doors for opening and closing an entrance at a side of an electric railcar.  
           [0002]    For protecting passengers in an electric railcar, a side sliding door apparatus is required to have such a high reliability without any accidental operation while the railcar is running or staying stationary. In case of emergency, however, the side sliding door apparatus is required to be opened quickly by a simple operation. To this end, the inventors of the present application have developed a side sliding door apparatus for an electric railcar disclosed in Japanese Patent Publication (TOKKAI) No.  2000-142392.    
           [0003]    [0003]FIG. 10 to FIG. 13 show the side sliding door apparatus for the electric railcar disclosed in the patent publication, and a brief description thereof will be given. FIG. 10 is a side view showing an entire structure of the side sliding door apparatus for the electric railcar, and FIG. 11 is an enlarged view showing essential parts thereof. In FIGS. 10 and 11, two sliding doors  1  and  2  are movably suspended from a door rail  3 , which is mounted horizontally along a side of the electric railcar, via moving bodies  4 . The sliding doors  1  and  2  are capable of moving horizontally in reverse directions to open and close an entrance of the electric railcar. The sliding door  1  at the left side in FIG. 10 is driven by a linear motor  5  as an actuator connected to the moving body  4  of the sliding door  1 .  
           [0004]    As shown in FIG. 11, a movable element  5   a  of the linear motor  5  is connected to the moving body  4  such that the movable element  5   a  can slide by a predetermined distance x in opening and closing directions (in the horizontal direction in FIG. 11). A compression spring  6  is interposed between the movable element  5   a  and the moving body  4 . With this arrangement, the movable element  5   a  can freely move relative to the sliding door  1  by the predetermined distance x in the opening direction of the sliding door  1 .  
           [0005]    On the other hand, the sliding door  2  at the right side is moved along with a motion of the sliding door  1  via a direction changing mechanism  7 . As shown in FIG. 11, the direction changing mechanism  7  is comprised of a lower rack  9  connected to the moving body  4  of the sliding door  1  via a connecting rod  8 , an upper rack  11  connected to the moving body  4  of the sliding door  2  via a connecting plate  10 , and a pinion  12  engaging the racks  9  and  11  at the same time. The lower rack  9  and the upper rack  11  are guided in a unit case  7   a  fixed on the railcar side such that they can slide in the opening and closing directions. A shaft fixed on the unit case  7   a  supports the pinion  12 . The direction changing mechanism  7  changes a moving direction of the sliding door  1  driven by the linear motor  6  and transmits the motion to the sliding door  2 .  
           [0006]    [0006]FIGS. 12 and 13 show details of a locking mechanism  13  arranged at a side of the direction changing mechanism  7  in FIG. 10, as well as a push rod  14  and a pull fitting  15  for causing the locking mechanism  13  to lock and unlock. FIG. 12 shows a state in which the locking mechanism  13  locks the sliding doors  1 ,  2 . FIG. 13 shows a state in which the locking mechanism  13  unlocks the sliding doors  1 ,  2 . In FIGS. 12 and 13, the push rod  14  and the pull fitting  15  are mounted on the movable element  5   a  of the linear motor  5 . The push rod  14  is fixed horizontally, and the pull fitting  15  with a hook end is placed over an upper surface of the push rod  14  and is connected to the push rod  14  to rotate vertically by a pin at one end. The pull fitting  15  is forced upward by a compression spring  16  interposed between the pull fitting  15  and the push rod  14 , and is restricted in an upward rotational range by a headed pin  17  that loosely penetrates the push rod  14  to be screwed into the pull fitting  15 . A guide fitting  18 , which is arranged to contact an upper surface of the pull fitting  15  to limit the pull fitting  15  from rotating upward, is fixed at a front end of a frame of the linear motor  5 .  
           [0007]    The locking mechanism  13  is comprised of a vertical latch rod  22  guided in a guide cylinder  21  supported and fixed by the unit case  7   a  to slide in an axial direction, a latch plate  23  integrated with a head of the latch rod  22 , and a lock spring  24  comprised of a tension spring for urging the latch rod  22  downward. For moving the locking mechanism  13  with the sliding door  1 , the locking mechanism  13  is comprised of a slider  19  guided to slide in the moving direction of the sliding doors  1 ,  2 , and a back spring  20  comprised of a compression spring for urging the slider  19  toward the sliding door  2 . A cam surface  19   a  comprised of an inclined step is formed at an upper side of the slider  19 . An engagement protrusion  19   b  is provided at an end of the slider  19 . A roller  25  contacting the cam surface  19   a  of the slider  19  is rotatably mounted on the latch rod  22  via an attachment fitting (not shown). The lock spring  24  is extended between the latch plate  23  and the unit case  7   a  for urging the latch rod  22  downward. As described later, the latch rod  22  moves up and down in response to the opening and closing motions of the sliding doors  1 ,  2 .  
           [0008]    [0008]FIG. 12 shows a state in which the sliding doors  1 ,  2  are locked in a closed state in the above described side sliding door apparatus. In this state, an end of the latch rod  22  is inserted into the latch hole  26  of the upper rack  11  constituting an engagement section of the direction changing mechanism  7  to lock the sliding motion of the upper rack  11 . Thus, the sliding doors  1 ,  2  connected to the upper rack  11  can not move. Further, in this state, the push rod  14  abuts against the engagement protrusion  19   b  of the slider  19 , and the hook portion of the pull fitting  15  is engaged with the head of the engagement protrusion  19   b  with an inclined surface.  
           [0009]    When an opening instruction is given in this state, the movable element  5   a  of the linear motor  5  moves leftward. At an initial stage of this movement, the movable element  5   a  moves leftward by a predetermined distance x with pressing the compression spring  6  while leaving the sliding door  1  in a closed position. In the meantime, the pull fitting  15  pulls the slider  19  via the engagement protrusion  19   b . At this moment, the pull fitting  15  tries to rotate upward due to the urging force of the compression spring  16  and the action of the inclined surface of the head of the engagement protrusion  19   b , but can not rotate because the guide fitting  18  presses the pull fitting  15 .  
           [0010]    When the slider  19  is pulled leftward, the roller  25  is pushed up onto the upper surface of the slider  19  via the inclined plane of the cam surface  19   a , as shown in FIG. 13. This causes the latch rod  22  to be lifted and pulled out of the latch hole  26  to release from the upper rack  11 , thereby unlocking the sliding doors  1 ,  2 . When the movable element  5   a  moves for almost the predetermined distance x, the pull fitting  15  is released from the guide fitting  18 . As a result, the pull fitting  15  is rotated upward by the urging force of the compressing spring  16  and is released from the engagement protrusion  19   b  of the slider  19 . Even when the pull fitting  15  is released, the slider  19  remains in an advancement position due to the urging force of the back spring  20  and keeps the roller  25  pushed up.  
           [0011]    Then, the movable element  5   a  moves the sliding door  1  leftward up to a predetermined full-open position. Accordingly, the sliding door  2  moving along with the sliding door  1  via the direction changing mechanism  7  moves rightward, so that the sliding doors  1 ,  2  are opened. The sliding door  1  then moves rightward in response to a closing instruction, and when the sliding door  1  reaches the closing position in FIG. 12, the movable element  5   a  pushes the slider  19  via the push rod  14 . Consequently, the roller  25  falls off the upper side of the cam surface  19   a , and the latch rod  22  enters the latch hole  26  of the upper lack  11  to lock the sliding doors  1 ,  2 . At the same time, the guide fitting  18  pushes the pull fitting  15  to engage the engagement protrusion  19   b.    
           [0012]    In case of emergency, an emergency handle  28  in FIGS. 10 and 12 is turned 90° from a position indicated by a hidden line to a position indicated by a solid line in FIG. 12. The emergency handle  28  is connected to the latch plate  23  via a flexible cable wire  29 . When the emergency handle  28  is rotated, the latch plate  23  is raised to pull the latch rod  22  out of the latch hole  26 . As a result, the latch rod  22  is released from the upper rack  11 , thereby enabling the sliding doors  1 ,  2  to be opened manually.  
           [0013]    The above described side sliding door apparatus for the electric railcar disclosed in the patent publication turned out to have problems as described below.  
           [0014]    The emergency handle is connected to the unlocking mechanism via the cable wire. When the emergency handle is operated, the cable wire pulls the latch rod to unlock the sliding doors. The cable wire, however, tends to have a play due to tension or loosening, and therefore it is difficult to securely unlock the sliding doors.  
           [0015]    When the emergency handle is operated in the conventional apparatus, the sliding doors are unlocked, however remain closed. Thus, it is difficult to recognize that the sliding doors can be opened manually, thereby delaying for the passengers to quickly go out of the electric railcar.  
           [0016]    It is therefore an object of the present invention to improve the reliability in the operation of emergency opening means in a side sliding door apparatus for an electric railcar, thus making emergency escape easier.  
           [0017]    Further objects and advantages of the invention will be apparent from the following disclosure of the invention.  
         SUMMARY OF THE INVENTION  
         [0018]    To attain the above object, the present invention provides a side sliding door apparatus having sliding doors movably supported by a horizontal door rail. The sliding doors are locked when a latch member movably guided and supported on a railcar side engages a fixing member disposed on a sliding door side. Upon release of the latch member from the fixing member by an operation of an emergency handle, the sliding doors can be opened manually. A motion of the emergency handle is directly transmitted to the latch member to release the latch member from the fixing member. More specifically, according to the present invention, the motion of the emergency handle is rigidly transmitted to the latch member without going through a flexible cable wire or a movable link. Therefore, it is possible to reliably operate the sliding doors without a problem due to tensioning or loosening of a cable wire.  
           [0019]    It is preferred that when the emergency handle is operated, at the same time, a part of the emergency handle pushes the fixing member disposed on the sliding door to form a space between the sliding doors. With this arrangement, the space is formed between the sliding doors when the emergency handle is operated. Thus, it is possible to visually recognize that the sliding doors can be opened, and to easily open the sliding doors manually by putting a hand in the space.  
           [0020]    Further, it is preferred that the emergency handle is arranged to recede easily when the fixing member on the sliding door side abuts against the emergency handle when the sliding doors are closed after the emergency handle is operated to manually open the sliding doors. With this arrangement, after being unlocked manually, when the sliding door is closed manually and abuts against the emergency handle, the emergency handle will not be damaged because the emergency handle recedes to absorb the impact. In this case, if the emergency handle returns to an original position before the operation, the sliding doors are locked again. Therefore, it is preferred to provide a braking mechanism to stop the emergency handle in front of the original position where the sliding doors are locked again when the emergency handle is receded due to the collision of the fixing member on the sliding door side. This prevents the sliding doors from being locked again.  
           [0021]    The braking mechanism may be comprised of a ball movably fitted in the emergency handle to receive a backpressure of a compression spring, and a guide member provided on a railcar side to follow a track of the ball when the emergency handle is operated. The guide member forms a guide surface on which the ball slides. When the ball approaches a step portion formed on the guide surface, the emergency handle receded due to the collision is stopped.  
           [0022]    It is preferred that the emergency handle presses the fixing member on the sliding door side with which the latch member is engaged. Also, the latch member may be comprised of a latch rod capable of sliding in an axial direction. The latch rod is inserted into a latch hole formed in the fixing member on the sliding door side to be engaged with the fixing member.  
           [0023]    The emergency handle may be comprised of a rotary handle having a cam section at one end and a handle at the other end. The cam section presses an arm integrated with the latch rod to pull the latch rod out from the latch hole.  
           [0024]    It is preferred that the emergency handle presses the fixing member on the sliding door side by the handle.  
           [0025]    It is possible to provide means for detecting an operation of the emergency handle. The detecting means transmits an operation signal to shut off power supply to an actuator so that the sliding doors can open and close manually. Thus, it becomes easy and safe to manually open the unlocked sliding doors. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    [0026]FIG. 1 is a side view showing a side sliding door apparatus in a locked state according to an embodiment of the present invention;  
         [0027]    [0027]FIG. 2 is a side view showing an emergency unlocking action of the side sliding door apparatus in FIG. 1;  
         [0028]    [0028]FIG. 3 is a side view showing an emergency unlocking action of the side sliding door apparatus in FIG. 1;  
         [0029]    [0029]FIG. 4 is a side view showing a state in which an emergency handle in FIG. 3 returns to an original position;  
         [0030]    [0030]FIG. 5 is a side view showing a side sliding door apparatus in a locked state according to another embodiment of the present invention;  
         [0031]    [0031]FIG. 6 is a side view showing an emergency unlocking action of the side sliding door apparatus in FIG. 5;  
         [0032]    [0032]FIG. 7 is a side view showing an emergency unlocking action of the side sliding door apparatus in FIG. 5;  
         [0033]    [0033]FIG. 8 is a side view showing a state in which an emergency handle in FIG. 7 returns to an original position;  
         [0034]    [0034]FIG. 9 is a plan view showing a braking mechanism in FIG. 5;  
         [0035]    [0035]FIG. 10 is a side view showing an entire structure of a conventional side sliding door apparatus;  
         [0036]    [0036]FIG. 11 is an enlarged view showing essential parts of the side sliding door apparatus in FIG. 10;  
         [0037]    [0037]FIG. 12 is a side view showing a locking action of the side sliding door apparatus in FIG. 10; and  
         [0038]    [0038]FIG. 13 is a side view showing an unlocking action of the side sliding door apparatus in FIG. 12. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0039]    Hereunder, embodiments of the invention will be explained with reference to the accompanying drawings. FIGS.  1  to  4  show a sliding door apparatus for an electric rail car according to the first embodiment of the present invention. Elements and parts corresponding to those of the conventional door apparatus shown in FIGS.  10  to  13  are denoted by the same reference numerals.  
         [0040]    [0040]FIG. 1 is a side view showing essential parts of the side sliding door apparatus in a locked state. In FIG. 1, as is the case with the prior art, two sliding doors  1 ,  2  are suspended via moving bodies  4  from a door rail (not shown) mounted horizontally along a side of an electric railcar. The two sliding doors move horizontally in reverse directions in FIG. 1 to open and close an entrance of the electric railcar.  
         [0041]    A linear motor  5  as an actuator for opening and closing the sliding doors  1 ,  2 , a locking mechanism for locking the closed sliding doors  1 ,  2 , and an unlocking mechanism for unlocking the sliding doors  1 ,  2  are provided for respective ones of the two sliding doors  1 ,  2  (in FIG. 1, the linear motor  5  and other parts are shown only in the left sliding door  1 ). Therefore, even if the linear motor  5  for one of the two sliding doors  1 ,  2  breaks down, the linear motor  5  for the other one can open and close. A description of the sliding door  1  will be described next. Structures and operations of the sliding door  1  are identical with those of the sliding door  2 .  
         [0042]    In FIG. 1, the moving body  4  is fixed to the sliding door  1  by two bolts  30 , and a movable element  5   a  of the linear motor  5  is connected to the moving body  4 . In a state in which the sliding door  1  is closed as shown in FIG. 1, the sliding door  1  is locked by a locking mechanism  13 . The locking mechanism  13  is comprised of a latch rod  22  as a latch member slidably supported in a vertical direction on the railcar side, and a lock spring  24  comprised of a tension coil spring as a forcing member for urging the latch rod  22  toward the sliding door  1 . The latch rod  22  is comprised of a circular rod, and is guided into a hollow square guide cylinder  21  to move in and out a latch hole  26  formed in the moving body  4  as a fixing member of the sliding doors. A latch plate  23  is secured to a head of the latch rod  22 , and the lock spring  24  extends between the latch plate  23  and the guide cylinder  23  with being pressed. The latch rod  22  inserted into the latch hole  26  is engaged with the moving body  4  to lock the sliding door  1  in a closed state.  
         [0043]    A reference numeral  31  denotes a lock switch (a limit switch) as lock detecting means. The lock detecting means  31  fixed on the railcar side is turned on to transmit a locking signal to the railcar in the locked state as shown in FIG. 1. A reference numeral  32  denotes a door-closing switch as door closure detecting means. The closure detecting means  32  is turned on to transmit a door closure signal to the railcar in the closed state as shown in FIG. 1. An electromagnetic solenoid  33  is provided as an unlocking mechanism for driving the latch rod  22  against the force of the lock spring  24 . The electromagnetic solenoid  33  is fixed vertically on the railcar, and when the electromagnetic solenoid  33  is off, a plunger  33   a  thereof located at the lower end of a stroke is positioned in the vicinity of a lower surface of the latch plate  23 .  
         [0044]    In FIG. 1, release holding means  34  is provided for holding the latch rod  22  in a state released from the moving body  4 . The release holding means  34  is comprised of a slider  19  as locking means for locking the latch rod  22  in a position released from the moving body  4 , and a back spring  20  having a tension coil spring as forcing means for forcing the slider  19  toward the latch rod  22 . The slider  19  is supported on the railcar side to slide horizontally in FIG. 1, and contacts a roller  25  integrated with the latch rod  22  via a cam surface  19   a  to prevent the latch rod  22  from entering the latch hole  26 . The roller  25  is rotatably mounted on a mounting plate  35  integrated with a head of the latch head  22 . The back spring  20  has one end thereof hooked on the slider  19  and the other end thereof hooked on the railcar. Therefore, in the closed state shown in FIG. 1, the slider  19  is pushed rightward in FIG. 1 by a push rod  14  mounted at an end of the movable element  5   a . Also, the cam surface  19   a  is released from the roller  25 , and the back spring  20  is pressed.  
         [0045]    A reference numeral  28  denotes an emergency handle, namely a manually operating rotary handle. The emergency handle  28  has a Z-shape with a cam section  28   a  at one end thereof and a handle  28   b  at the other end as shown in FIG. 1. The emergency handle  28  is rotatably supported on the railcar side. Normally, the emergency handle  28  is positioned horizontally with being restricted in a position by a stopper  37 . A switch operating section  28   c  is integrated with the operating handle  28 . In the state shown in FIG. 1, an unlock arm  38  is positioned in the vicinity of the cam section  28   a , and the unlock arm  38  is bent to be integrated with the mounting plate  35 . A reference numeral  39  denotes an emergency handle switch for detecting the operation of the emergency handle  28 . In the state shown in FIG. 1, the actuator  39   a  is in ON state while pressed by the switch operating section  28   c.    
         [0046]    A normal opening and closing operation will be explained with reference to FIG. 1. In response to an opening instruction in the closed state shown in FIG. 1, the electromagnetic solenoid  33  is turned on and the plunger  33   a  is pulled to protrude upward. The plunger  33   a  lifts the latch rod  22  via the latch plate  23  to release the latch rod  22  from the latch hole  26 . The latch rod  22  is released from the moving body  4  to unlock the sliding door  1 . On this occasion, the lock switch  31  is actuated to transmit an unlocking signal to the railcar side. The unlock spring  24  is tensioned to generate a force for urging the latch rod  22  downward.  
         [0047]    After a predetermined time since the unlocking signal is transmitted from the lock switch  31 , the linear motor  5  is turned on, and the movable element  5   a  starts moving leftward in FIG. 1. On this occasion, the door closure switch  32  is turned off to transmit an opening signal to the railcar. Upon movement of the movable element  5   a , the slider  19  pushed by the push rod  14  moves in the same direction as the movable element  5   a  by an urging force of the back spring  20  to cause the cam surface  19   a  to move below the roller  25 . In this state, the slider  19  abuts against a front surface of a housing for the linear motor  5  and then stops.  
         [0048]    After a predetermined period of time since a closing signal is sent from the door closure switch  32 , the electromagnetic solenoid  33  is turned off. This causes the latch rod  22  lifted by the plunger  33   a  to move downward due to an urging force of the lock spring  24 , but stops when the roller  25  abuts against the cam surface  19   a , so that the sliding doors  1 ,  2  remain unlocked.  
         [0049]    In response to a closing instruction in the opened state, the movable element  5   a  moves rightward to bring the push rod  14  to contact with the slider  19 . As the movable element  5   a  further moves from this point, the push rod  14  presses the slider  19  rightward to release the cam surface  19   a  from the roller  25 . This causes the latch rod  22  to move downward by the urging force of the lock spring  24 , so that the end thereof abuts against the moving body  4 . With the rightward movement of the moving body  4 , the latch rod  22  falls into the latch hold  26  to lock the sliding door  1  while sliding on the upper surface of the moving body  4 . As a result, the side sliding door apparatus is brought again into the locked state shown in FIG. 1. In the meantime, the back spring  20  is stretched to restore the urging force for the next sliding door opening action.  
         [0050]    An emergency opening operation will be explained with reference to FIGS.  2  to  4 . FIG. 2 shows an initial stage of an operation of the emergency handle  28 . When the emergency handle  28  is slightly rotated clockwise in a direction indicated by an arrow, the cam part  28   a  pushes up the unlock arm  38 , and accordingly, the latch rod  22  starts exiting the latch hole  26 . On this occasion, an emergency handle switch  39  is turned off, and an emergency operation signal is transmitted to the railcar side. This shuts off the power to the linear motor  5 .  
         [0051]    [0051]FIG. 3 shows a state in which the emergency handle  28  is turned upright 90° from the position in FIG. 2 in a direction indicated by an arrow. In this state, the latch rod  22  is completely pulled out from the latch hole  26 , and the sliding door  1  is unlocked. In this case, the emergency handle  28  transmits its rotation directly to the unlock arm  38  integrated with the latch rod  22 , thereby eliminating delayed or insufficient locking operation. In the process of the rotation, the emergency handle  28  slightly presses the moving body  4  as the fixing member on the sliding door side leftward via the handle  28   b . This forms a space S between the sliding door  1  and the sliding door  2 . Thus, it is possible to recognize that the sliding door  1  is unlocked, and the sliding door  1  can easily be opened manually by inserting a hand into the space S.  
         [0052]    [0052]FIG. 4 shows a state in which the emergency handle  28  is returned to the original position. When the emergency handle  28  is returned to the original position, the emergency handle switch  39  is pressed to supply the power to the linear motor  5  to close the sliding door  1 , so that the sliding door  1  is locked automatically as mentioned above. Incidentally, although there are two sliding doors in the illustrated embodiment, the present invention should not be limited to this, and applicable to a side sliding door apparatus having only one sliding door.  
         [0053]    FIGS.  5  to  9  show a side sliding door apparatus for an electric railcar according to the second embodiment of the present invention. In the first embodiment, the handle  28   b  of the emergency handle  28  is upright after rotated by 90° from the wait position as shown in FIG. 3, and the handle  28   b  is in contact with an end face of the moving body  4  in parallel. A flat end face of the cam part  28   a  contacts a lower surface of the unlock arm  38  in parallel. When the sliding door  1  is manually opened in this unlocked state, if the sliding door  1  is manually closed for some reason, the moving body  4  collides with the handle  28   b  of the emergency handle  28  from the left side in FIG. 3. This causes the emergency handle  28  to try to rotate counterclockwise and recede. However, the emergency handle  28  in FIG. 3 tends to receive a large impact as described below.  
         [0054]    Specifically, in the unlocked state in FIG. 3, the flat end face of the cam part  28   a  of the emergency handle  28  contacts the lower surface of the unlock arm  38 . Also, the center of the contact surface between the cam part  28   a  and the unlock arm  38  in the horizontal direction in FIG. 3 is located just above an axis  36  that is a pivot of the emergency handle  28 . Therefore, in order to rotate the emergency handle  28  counterclockwise, the unlock arm  38  must be pushed up against the force of the lock spring  24 , thereby creating a large resistance. The handle  28   b  contacts the end face of the moving body  4  in parallel as well. Therefore, when the moving body  4  collides with the handle  28   b , an application point of an impact force F is not constant. Assuming that the impact force F is applied to the handle  28   b  at a top end face of the moving body  4  as shown in FIG. 3, an arm length of the rotational moment around the axis  36  is small, thereby making it difficult to rotate the emergency handle  28 . For the reasons stated above, in the state shown in FIG. 3, when the sliding door  1  collides with the emergency handle  28 , a large impact is applied to the handle  28   b  to damage the emergency handle  28 . The second embodiment of the present invention is intended to solve this problem.  
         [0055]    In FIG. 5, the cam part  28   a  of the emergency handle  28  has a pointed tip formed in a triangle shape. The end face of the cam part  29   a , which contacts the unlock arm  38  in the unlocked state, is rounded in an arc shape. When the emergency handle  28  is slightly rotated clockwise in a direction indicated by an arrow in the locked state in FIG. 5, the cam part  28   a  starts pushing up the unlock arm  38 . On this occasion, the emergency handle switch  39  is turned off, and an emergency operation signal is transmitted to the railcar side. This shuts off the power supply to the linear motor  5 .  
         [0056]    When the emergency handle  28  is further rotated in the direction indicated by the arrow from the operating position indicated in FIG. 6, the unlock arm  38  is further pushed up to cause the latch rod  22  to exit the latch hole  26  and unlock the sliding door  1 . At the same time, the emergency handle  28  presses the moving body  4  leftward at a rounded corner of an L-shape connection where the cam part  28   a  and the handle  28   b  are connected to each other. FIG. 7 shows the unlocked state after the emergency handle is rotated from the wait position by 45°. The cam part  28   a  is brought into contact with the stopper  37  to restrict a position of the emergency handle. In this state, a space S is formed between the sliding door  1  and the sliding door  2 , so that they can be opened manually.  
         [0057]    [0057]FIG. 8 shows a state in which the emergency handle  28  is returned to the original position. When the emergency handle  28  is returned from the position at 45° to a position at 0°, the emergency handle switch  39  is turned on to supply the power to the linear motor  5 , which moves the sliding door  1  in the closing direction to be automatically locked by the normal closing action.  
         [0058]    In the second embodiment, in the unlocked state in FIG. 7, the arc surface of the end of the cam part  28   a  is in contact with the unlock arm  38 , and the point of contact is deviated counterclockwise in FIG. 7 from a position just above the axis  36 . If the manually opened sliding door  1  is closed manually again and a force G is applied to the emergency handle  28  due to collision with the moving body  4 , the emergency handle  28  receded due to the collision moves in such a direction that the cam part  28   a  moves away from the unlock arm  38 . Thus, the emergency handle  28  can easily rotate counterclockwise without being disturbed by a reactive force of the lock spring  24  acting on the emergency handle  28  via the cam part  28   a . Further, since the force G of the moving body  4  is applied on the arc surface at the corner of the emergency handle  28 , the arm length of the rotational moment around the axis  36  due to the collision force G is constant, so that the emergency handle  28  can rotate (recede) stably. As a result, in the second embodiment, when the sliding door  1  collides with the emergency handle  28 , the collision force G is reduced as compared with the first embodiment (G&lt;F). Therefore, the collision force G is more unlikely to damage the emergency handle  28 .  
         [0059]    If the emergency handle  28  returns to the position at 0° in a case where the emergency handle  28  recedes from the operating position at 45° due to the collision with the sliding door  1 , the sliding door  1  is automatically locked as mentioned above, thereby making it impossible to be opened manually. To solve this problem, the side sliding door apparatus is provided with a braking mechanism  40  for stopping the emergency handle  28  receding due to the collision with the sliding door  1  in front of such a position that the sliding door  1  is locked again.  
         [0060]    [0060]FIG. 9 is an enlarged plan view showing the braking mechanism, wherein the emergency handle  28  in FIG. 5 is viewed from above. In FIG. 9, the switch operating section  28   c  is formed like a square cylinder protruding toward the cam part  28   a . A rounded hole is formed in the switch operating section  28   c  to penetrate through the switch operating section  28   c  in an axial direction such that the emergency handle  28  is positioned just above the axis  36  in the locked state in FIG. 5. A ball  41  is fitted in a back of the rounded hole in FIG. 5, i.e. in an upper end of the rounded hole in FIG. 9, such that the ball can enter and exit the round hole, and the ball  41  receives a back pressure from a compression spring  42 . The compression spring  42  is pressed by an adjusting screw  43  comprised of an embedded bolt screwed into a female screw threaded in the rounded hole from the lower side in FIG. 9. The adjusting screw  43  is fixed by a lock nut  44 .  
         [0061]    The arc guide member  45  for forming a guide surface on which the ball  41  slides is fixed to the railcar side along a track of the ball  41  when the emergency handle  28  is rotated. An end of the ball  41  pressed to the guide member  45  by the compression spring  42  in the locked state in FIG. 5 falls into a hole  45   a  formed in the guide member  45 , and the ball stays there. The adjusting screw  43  is moved in the axial direction to adjust a pressure of the ball  41  against the guide member  45 . As shown in FIG. 9, a step  45   b  is formed on the guide surface of the guide member  45  on which the ball  41  contacts, and the guide member  45  has a greater thickness on a side where the hole  45   a  is formed than on the opposite side. The step  45   b  is located at a position where the ball  41  approaches just before the emergency handle  28  is returned counterclockwise from the operating position in FIG. 7 to cause the latch rod  22  to start entering into the latch hole  26 . A higher side and a lower side of the guide member  45  are formed continuously at an inclined surface of the step  45   b.    
         [0062]    In the braking mechanism  40  described above, when the emergency handle  28  is operated in the locked state in FIG. 5, the ball  41  is released from the hole  45   a  of the guide member  45  to roll down on the step  45   b . The ball  41  is positioned at the lower side of the guide surface in the unlocked state in FIG. 7. When the emergency handle  28  recedes counterclockwise in response to the collision with the sliding door  1 , the ball  41  slides on the guide member  45  toward the step  45   b . When the ball  41  approaches the step  45   b , however, the emergency handle  28  is damped to stop the ball  41  in front of the higher side of the guide member  45 . Therefore, the emergency handle  28  does not return to the locking position in FIG. 5. As a result, even when the manually opened sliding door  1  is closed manually, the sliding door  1  will not be automatically locked by the return of the emergency handle  28 .  
         [0063]    In the second embodiment shown in FIG. 5, a pull fitting  15 , a compression spring  16 , a headed pin  17 , a guide fitting  18 , and an engagement protrusion  19   b  of the slider  19  are provided in place of the back spring  20  of the first embodiment. These component parts are identical with those of the prior art described with reference to FIGS. 12 and 13, and a brief description thereof will be given.  
         [0064]    In response to the opening instruction given to the sliding door  1  in the closed state in FIG. 5, the electromagnetic solenoid  33  unlocks the sliding door  1 . The unlocking signal from the unlock switch  31  causes the movable element  5   a  of the linear motor  5  to start moving leftward as in the case of the above described first embodiment. On this occasion, in the state in FIG. 5, the pull fitting  15  pulls the slider  19  via the engagement protrusion  19   b  to a position below the roller  25 . When the slider  19  reaches the position just below the roller  25 , the pull fitting  15  is released from the guide fitting  18  and opens upward to be released from the engagement protrusion  19   b.    
         [0065]    In the closing action of the sliding door  1 , the rightward movement of the movable element  5   a  causes the push rod  14  to push the slider  19  via the engagement protrusion  19   b , so that the slider  19  is released form the roller  25 . Further, when the pull fitting  15  approaches the guide fitting  18 , the pull fitting  15  is depressed to engage the engagement protrusion  19   b  again. In the second embodiment, the back spring  20  does not need to be extended (FIG. 1) in the closing action. Therefore, the capacity of the linear motor  5  can be reduced.  
         [0066]    As described above, according to the present invention, the motion of the emergency handle is directly transmitted to the latch member of the locking mechanism. Thus, it is possible to unlock the sliding doors manually and securely without any play. At the same time, the emergency handle presses the sliding doors to form the space therebetween. Thus, it can be recognized visually that the sliding doors are unlocked, thereby facilitating the passengers to quickly escape from the electric railcar.  
         [0067]    While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.

Summary:
A sliding door apparatus has a sliding door movably supported on a horizontal door rail for opening and closing an entrance of a vehicle, i.e. railroad car. The sliding door is locked when a latch member engages a fixing member disposed on the sliding door. When an emergency handle is operated, the latch member is released from the fixing member, and the sliding door can be opened manually. A motion of the emergency handle is directly transmitted to the latch member to release the latch member from the fixing member. Therefore, it is possible to operate the sliding door reliably without a problem associated with the flexible wire.