Abstract:
A door system for a railway car which provides for both high and low level access. The door system comprises a sliding door, a platform displaceable between raised and lowered positions for respectively clearing and covering the stairwell of the railway car, and a threshold extending laterally outwardly of the sliding door to provide a continuation of the platform when displaced to its lowered position. The threshold is releasably connected to the sliding door for co-linear movement with the sliding door when the platform is raised, while remaining stationary in a functional position when the platform is lowered for enabling high level boarding.

Description:
RELATED APPLICATIONS 
     This Application is a Continuation-In-Part of U.S. application Ser. No. 09/358,460 filed on Jul. 22, 1999, pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to door systems for railway vehicles and, more particularly, to door systems which provide for boarding from both high and low level platforms. 
     2. Description of the Prior Art 
     Railway vehicles are often used on railroad lines having passenger stations equipped with high boarding platforms extending at the vehicle floor level and others with low level boarding platforms extending at or near ground level. 
     Accordingly, efforts have been made to develop door systems providing for both high and low level access. For instance, U.S. Pat. No. 5,070,794 issued on Dec. 10, 1991 to Kunst et al. discloses a multi-sectioned sliding door assembly for use with a railway vehicle having a stairwell extending downwardly from the floor of the vehicle to a lower boarding level. The sliding door assembly comprises an upper sliding door displaceable to an open position for high level boarding and a lower sliding door disposed immediately below the upper sliding door and displaceable therewith to an open position for low level boarding. The upper sliding door is supported at the top by a sliding connection to a door overhead structure. An upper threshold is secured to an upper outer section of the lower sliding door to be positioned adjacent an elevated platform of a train station. The lower sliding door is connected via a slide assembly to the railway vehicle structure in the region of the upper threshold platform. In addition, the bottom of the lower door panel is guided in a lower threshold. A stairwell platform is hingedly connected to one side of an upper horizontal plane of the stairwell for covering the same during high level boarding. 
     Although the door assembly of the above mentioned patent is effective for enabling both high and low level boarding operations, it has been found that there is a need for a simpler system which requires fewer adjustments. 
     SUMMARY OF THE INVENTION 
     It is therefore an aim of the present invention to provide an improved door system providing for both high and low level access. 
     It is also an aim of the present invention to provide a door system which is relatively simple and economical to manufacture. 
     Therefore, in accordance with the present invention there is provided a door system for a railway vehicle having a door opening and a stairwell extending downwardly from a vehicle floor level to a bottom end of the door opening, the door system comprising a sliding door displaceable between open and closed positions for selectively closing the door opening, a stairwell platform displaceable between a retracted position for clearing the stairwell and an extended position for covering the stairwell, and a threshold extending laterally outwardly of the sliding door substantially at the vehicle floor level, the threshold being releasably connected to the sliding door for conjoint movement therewith when the stairwell platform is in the retracted position thereof, while remaining stationary in a functional position when the stairwell platform is in the extended position thereof for allowing high level boarding. 
     In accordance with a further general aspect of the present invention, there is provided a door system comprising a sliding door displaceable between open and closed positions, a stairwell platform displaceable between a retracted position for clearing a railway vehicle stairwell and an extended position for covering the stairwell, and a threshold extending laterally outwardly of the sliding door substantially at the vehicle floor level, the threshold being adapted to move with the sliding door and to be made stationary in a functional position thereof by engagement of the threshold with a retainer upon positioning of the stairwell platform to the extended position thereof. 
     In accordance with a still further general aspect of the present invention, there is provided a lock for releasably interconnecting first and second members, said lock including a catch provided on one of said first and second members and a latch assembly provided on the other one of said first and second members, said latch assembly including a housing, a slot defined in said housing, a spring-loaded latch member mounted in said housing, said latch member having a catch engaging portion extending outwardly of said housing through said slot for movement therein, and a safety member displaceable between a first position for preventing access to the interior of said housing through said slot when said latch member is urged in engagement with said catch and a second position for at least partly clearing said slot so as to allow said latch member to be displaced to an unlocked position in which said latch member and said catch are disconnected. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration a preferred embodiment thereof, and in which: 
     FIG. 1 is a fragmented perspective view of a dual level access door system used in combination with a railway vehicle in accordance with a preferred embodiment of the present invention; 
     FIG. 2 is a fragmented perspective view of the dual level access door system of FIG. 1, showing a sliding door displaced to an open position thereof together with an upper threshold for allowing low level embarkment and disembarkment of passengers; 
     FIG. 3 is a fragmented perspective view of the dual level access door system of FIG. 1, showing the sliding door displaced to the open position thereof independently of the upper threshold which has remained stationary in order to bridge the space between a stairwell platform and an elevated platform of a train station; 
     FIG. 4 is a longitudinal cross-sectional view of the sliding door, illustrating the construction of a lock mechanism used to selectively connect and disconnect the upper threshold to the sliding door; 
     FIG. 5 is an enlarged side view of the lock mechanism shown in an engaged position wherein the upper threshold is secured to the sliding door; 
     FIG. 6 is an enlarged side view of the lock mechanism illustrating how the lock mechanism is displaced to a disengaged position wherein the upper threshold is disconnected from the sliding door; 
     FIG. 7 is an exploded perspective view of a threshold latch assembly in accordance with a second embodiment of the present invention; 
     FIG. 8 is a rear plan view of the threshold latch assembly shown in a locked position thereof with the back plate of the latch housing omitted for clarity; and 
     FIG. 9 is a rear plan view of the threshold latch assembly shown in an unlocked position. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now referring to the drawings, and in particular to FIGS. 1 to  3 , a dual level access door system  10  suited for use in combination with a railway vehicle  12  and embodying the elements of the present invention will be described. 
     As seen in FIGS. 1 to  3 , the railway vehicle  12  has a stairwell  14  extending downwardly from a floor  16  and leading to a door opening  18  defined in a side wall  20  of the railway vehicle  12 . 
     A stairwell platform  22  is pivotally mounted at a lower edge thereof to a side wall  24  of the stairwell  14  by means of a hinge  26 . A latch  28  is provided for maintaining the stairwell platform  22  in a retracted or raised position thereof adjacent the side wall  24  during low level platform embarkment and disembarkment of passengers. By unlocking the latch  28 , the stairwell platform  22  can be manually swung down to an extended position, as shown in FIG. 3, wherein the stairwell platform  22  covers the stairwell  14  and provides a continuation of the floor  16  for allowing ingress and egress of passengers from an elevated boarding platform  30  of a train station. A lock  32  is provided on the floor  16  on the other side of the stairwell  14  for releasably securing the stairwell platform  22  in the extended or lowered position thereof. 
     The door system  10  further comprises a sliding door  34  having an upper section  35  fixedly secured to a lower section  37  by means of a connecting plate  39  bolted or otherwise secured to respective inner surfaces of the upper and lower sections  35  and  37 . The upper section  35  of the sliding door  34  is slidably mounted at an upper end thereof to a door overhead structure (not shown) forming part of the railway vehicle  12 . A strip (not shown) depends from the bottom side of the lower section  37  of the sliding door  34  for engagement in a corresponding longitudinal guiding groove (not shown) defined in the top surface of a lower threshold (not shown) secured to the railway vehicle  12 . The strip is made of a low friction material, such as nylon. An actuating mechanism (not shown) is provided for sliding the door  34  between open and closed positions. The sliding door  34  is slid open into a door receiving cavity  40  provided in the side wall  20  of the railway vehicle  12 . 
     An upper threshold  42  extends laterally outwardly of the sliding door  34  to provide a continuation of the stairwell platform  22  in order to bridge the space between an elevated boarding platform, such as at  30 , and the stairwell platform  22 . The upper threshold  42  is releasably connected to the sliding door  34  via a lock mechanism  44 . 
     When the stairwell platform  22  is held in the raised position thereof, the upper threshold  42  is secured to the sliding door  34 , via the lock mechanism  44 , for movement as a unit with the sliding door  34 , as seen in FIG.  2 . This enables passengers to ingress and egress at ground level via the stairwell  14 . 
     However, when the stairwell platform  22  is in its lowered position, as shown in FIG. 3, the upper threshold  42  is disconnected from the sliding door  34  and held in place by the stairwell platform  22 . The sliding door  34  can then be displaced into the door receiving cavity  40 , while the upper threshold  42  remains in a functional position thereof to bridge the space between the stairwell platform  22  and an elevated boarding platform, such as at  30 . 
     Referring now more specifically to FIGS. 4 to  6 , there will be described the construction and operation of the upper threshold  42  and of the associated lock mechanism  44 . 
     As seen in FIG. 4, the upper threshold  42  is slidably mounted on a support member  46  inserted in position within the lower portion  37  of the sliding door  34  for movement therewith. The upper threshold  42  is provided with a pair of spaced-apart parallel rail engaging members  48   a  and  48   b  adapted to receive therebetween an horizontal rail  50  formed at an upper end of the support member  46 . The rail  50  extends along an outer side of the sliding door  34  in a direction of motion thereof. An insert  52  made of a low friction material and having an inverted U-shaped portion is fixedly mounted on the rail  50  to provide an adequate sliding surface for the upper threshold  42 . According to a construction of the present invention, the upper threshold  42  and the support member  46  are made of aluminum, whereas the insert  52  is made of plastic. 
     The outer longitudinal side  54  of the upper threshold  42  extends downwardly to form a guide  56  with the rail engaging member  48   b.  A roller assembly  58  is mounted in the door receiving cavity  40  for engagement within the guide  56  so as to provide a support surface for the upper threshold  42  and at the same time prevent the sliding door  34  from swinging. As seen in FIGS. 1 to  3 , a support  60  is mounted to the structure of the railway vehicle  12  on the side of the door opening  18  opposed to the door receiving cavity  40  to support the upper threshold  42  when the same is displaced to the functional position thereof. 
     Accordingly, the upper threshold  42  is supported at opposed ends thereof when displaced to its functional position. 
     As seen in FIGS. 4 to  6 , the lock mechanism  44  comprises a pivotal latch  64  having first and second end portions  66  and  68 . A pivot pin  70  is provided intermediate the first and second end portions  66  and  68  of the latch  64  to pivotally connect the same to an outer surface  72  of the rail engaging member  48   a  for rotation in a plane parallel to the sliding door  34 . The latch  64  has an inverted V-shaped top surface formed of a first segment  74  and second segment  76 . A spring blade  78  is secured at one end thereof to the first segment  74  and engaged at opposed end thereof with an undersurface  80  of the upper threshold  42  for normally urging an engaging portion or pin  82  extending at right angles from the first end  66  of the latch  64  in the upper end of a vertical slot  84  defined at one end of the connecting plate  39 . In this position, the first segment  74  is substantially parallel to the undersurface  80  of the upper threshold  42  and the latter is connected to sliding door  34  for movement therewith. Accordingly, when the door actuator (not shown) is powered to displace the sliding door  34  to its open position, as seen in FIG. 2, the force applied to the sliding door  34  by the door actuator will be transmitted to the upper threshold  42  via the connecting plate  39 . No relative motion will occur between the upper threshold  42  and the rail  50  and, thus, the sliding door  34  and the upper threshold  42  will move as a unit to allow ground level boarding. 
     It is understood that other catch mechanisms could be used as an alternative to the above described vertical slot  84 . 
     As seen in FIGS. 1,  2  and  6 , the stairwell platform  22  is provided with a pin engaging surface  86 . When the stairwell platform  22  is lowered to its extended position as depicted by arrow  87  in FIG. 6, the pin  82  is engaged by the engaging surface  86 , thereby causing the latch  64  to pivot about the pivot pin  70  in a clockwise direction against the spring force exerted by the spring blade  78  so as to displace the pin  82  in a downward direction, as depicted by arrow  88 . This causes the pin  82  to move out of the vertical slot  84 , thereby disconnecting the latch  64  and, thus, the upper threshold  42  from the connecting plate  39 . The stairwell platform  22  is further provided with a pin abutment surface  90  extending at right angles to the pin engaging surface  86  to prevent the upper threshold  42  from being retracted with the sliding door  34 . Therefore, the stairwell platform  22  acts as a retainer having an abutment surface adapted to maintain the upper threshold  42  stationary while the door  34  is being opened. Accordingly, when the sliding door  34  is displaced to its open position, the upper threshold  42  will remain stationary and the rail  50  will slide between the rail engaging members  48   a  and  48   b.    
     A guard (not shown) may be provided to preclude unauthorized access to the pin  82 . Another guard (not shown) could be mounted to the outer surface of the sliding door  34  to protect the upper threshold  42  from the elements while the sliding door  34  is closed. 
     FIGS. 7 to  9  illustrate a second embodiment of a latch assembly  110  adapted to be securely mounted to an inwardly facing surface of the upper threshold  42  (FIG. 1) for releasably locking the same to the sliding door  34  (FIG.  1 ). 
     The latch assembly  110  comprises a housing  112  formed by a back plate  114  and a front cover  116  adapted to be secured to the back plate  114  to form therewith an enclosure for the latch mechanism. The latch mechanism includes a latch member  118  having a main body  120  provided with a first rounded end portion  122  pivotally mounted on a sleeve  124  which is, in turn, mounted on a pivot pin  126  extending at right angles from an inner surface of the front cover  116 . A radial slot  128  is defined in the pivot pin  126  and the sleeve  124  for receiving one end of a spring blade  130 . The spring blade  130  engages a top surface of a cavity  132  defined in the main body  120  of the latch member  118  for normally urging the same upwardly against a pin  134  extending at right angles from an inner surface of the back plate  114 . A rounded recess  136  is formed on the periphery of the main body  120  for receiving the pin  134 , which acts as a stopper for the latch member  118 . As seen in FIGS. 8 and 9, the inner surface of the front cover  116  can be integrally molded with a raised portion  138  matching the contour of the rounded end portion  122  of the main body  122  of the latch member  118 . 
     The main body  122  is provided at a distal end thereof with a catch engaging assembly  140  extending outwardly of the housing  112  through a slightly arcuate slot  142  defined in the front cover  116 . The catch engaging assembly  140  includes a hollow cylindrical lever  144  secured to the main body  122  by a peg  146 , as is well know in the art. A sleeve  148  is mounted at a distal end portion of the lever  144  and retained thereon by a bolt  150  threadably engaged with the lever  144 . The sleeve  148  is provided at one end thereof, adjacent an outer surface of the front cover  116 , with an annular flange  152 . 
     A shim  154  is mounted against the inner surface of the front cover  116  to take up wear. A circular hole  156  is defined in the shim  154  for receiving the pin  134 , thereby allowing to properly locate the shim  154  in the housing  112 . The shim  154  defines a slightly arcuate slot  158  which is identical to slot  142  and which is in register therewith when the shim  154  is properly installed in the housing  112 . 
     A safety member  160  is pivotally mounted on the pin  134  for preventing access to the interior of the housing  112  when the catch engaging assembly  140  is urged against the upper end of the slot  142 , as illustrated in FIG.  8 . The safety member  160  includes two identical spaced-apart side plates  162  connected at the bottom thereof by a web member  164 . The side plates  162  are spaced so as to receive the distal end of the main body  120  therebetween. The side plates  162  define an arcuate open ended slot  166  into which the lever  144  is engaged. When the latch member  118  will be pivoted downwardly against the biasing force of the spring blade  130 , the lever  144  will engage the sides of the slot  166 , thereby causing the safety member  160  to pivot about the pin  134  so as to clear the slot  142  and allow the catch engaging portion  140  of the latch member  118  to be disengaged from the slot  84  (FIG. 5) defined in the door  34 . The safety member  160  will be pivoted by the lever  144 , as long as the same remains in contact with a first portion  168  of the sides of the slot  166 . The slot  166  is provided with a second side portion  170  which has a curvature corresponding to that of the slot  142 . Therefore, when the lever  144  will engage said second side portion  170  of the slot  166 , no movement will be communicated to the safety member  160  and the same will remain stationary. 
     In use, the spring blade  130  will normally urge the latch member  118  upwardly with said catch engaging assembly  140  thereof engaged in the upper end of the slot  142 , as illustrated in FIG.  8 . In this position, the catch engaging assembly  140  will also be engaged in the slot  84  (FIG. 5) defined in the connecting plate  39 , thereby connecting the upper threshold  42  to the sliding door  34 . However, when the stairwell platform  22  will be lowered, the engaging surface  86  thereof will engage the sleeve  148  and displace the catch engaging assembly  140  downwardly out of engagement with the slot  84 , thereby allowing the sliding door  34  to move independently of the upper threshold  42 . The downward displacement of the catch engaging assembly  140  will be associated with the pivotal movement of the safety member  160 , as illustrated in FIG.  9 . However, when the stairwell platform  22  will be pivoted back to its raised position, the spring blade  130  will automatically pivot the latch member  118  and the safety member  160  upwardly to the position illustrated in FIG.  8 . In this position, the safety member  160  will cover the slot  142 , thereby preventing the latch mechanism from being damaged and passengers from being injured as a result of one of their members being caught in the latch mechanism. 
     The above described door system advantageously simplifies the sliding assembly of the door and reduces the number of adjustments which are required to maintain the functionality of the door system. Furthermore, by slidingly connecting the sliding door  34  to an overhead structure of the railway vehicle  12  and connecting the bottom of the sliding door  34  to a lower threshold  38  via a strip, such as a weather-strip, binding of the sliding door  34  will be prevented upon racking and twisting of the railway vehicle  12 . Finally, the fact that the sliding door  34  always moves as a single unit, allows the same to be more firmly supported by the railway vehicle structure.