Abstract:
A crossing arm for a vehicle having a longitudinal axis includes a plurality of hollow telescoping members. The telescoping members are mounted onto the vehicle and configured for extension parallel to the longitudinal axis. The members define a variable volume chamber, where the chamber has a minimum volume when the members are nested, and the chamber has a maximum volume when the members are extended. An actuator is in fluid communication with the plurality of telescoping members and is configured for delivering fluid to the chamber to move at least one telescoping member with respect to a second telescoping member to extend the crossing arm.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates generally to an automatic barrier, and more particularly, relates to an automatic, extendable barrier that is mounted on a vehicle. 
         [0002]    Buses often have a crossing arm that extends out from the front of the bus generally parallel to the longitudinal axis of the bus. The crossing arm is typically automatically deployed by the driver when the bus is temporarily stopped to pick up or let off passengers, particularly children. The crossing arm is intended to prevent passengers from walking immediately in front of the vehicle. When the crossing arm is deployed, passengers tend to walk around the barrier, a distance away from the front of the bus, where the driver can see them. 
         [0003]    The conventional crossing arms are typically actuated by a motor to pivot the arm from a first position, generally parallel to a front bumper of the bus, to a second position, generally parallel to the longitudinal axis of the bus. However, the linkage between the motor and the arm has a relatively high failure rate due to the typical loadings associated with a cantilevered system, including loadings imposed by the arm itself, external loadings on the arm, and vibration, among other things. 
         [0004]    Thus, there is a need for an improved barrier that is simple to operate and less vulnerable to failure. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The above-listed needs are met or exceeded by the present crossing arm for a vehicle including a plurality of hollow telescoping members. The telescoping members are mounted onto the vehicle and configured for extension with respect to a surface of the vehicle. The members define a variable volume chamber, where the chamber has a minimum volume when the members are nested, and the chamber has a maximum volume when the members are extended. An actuator is in fluid communication with the plurality of telescoping members and is configured for delivering fluid to the chamber to move at least one telescoping member with respect to a second telescoping member to extend the crossing arm. 
         [0006]    A crossing arm having a telescoping axis that is parallel to a longitudinal axis of a vehicle includes a centermost telescoping member centered about the telescoping axis, and at least one generally hollow second telescoping member that is concentrically disposed about the telescoping axis. One of the second telescoping members is configured to permit the reciprocable telescoping motion of the centermost telescoping member with respect to the second telescoping member. A generally hollow outermost telescoping member is concentrically disposed about the second telescoping member. The centermost telescoping member, the second telescoping member and the outermost telescoping member are in sealed fluid communication with an actuator configured for delivering fluid. The centermost telescoping member is extensible and retractable when the actuator is actuated. 
         [0007]    An alternate embodiment of crossing arm for a vehicle includes a plurality of hollow telescoping members. The telescoping members are mounted onto a side surface of the vehicle and configured for extension generally parallel to the longitudinal axis of the vehicle and from the side surface of the vehicle. The members are sealingly and slidingly attached to each other to define a variable volume chamber, where the chamber has a minimum volume when the members are nested, and the chamber has a maximum volume when the members are extended. An actuator is in fluid communication with the plurality of telescoping members and is configured for delivering fluid to the chamber to move at least one telescoping member with respect to a second telescoping member to extend the crossing arm. A fluid tank is mounted on the vehicle and in fluid communication with the actuator for delivering fluid to the actuator. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1A  is a side plan view of a front portion of a bus having the present bus crossing arm in the retracted position; 
           [0009]      FIG. 1B  is a side plan view of the front portion of the bus having the present bus crossing arm in the extended position; 
           [0010]      FIG. 2  is a schematic section view of the bus crossing arm and a pneumatic actuator; and 
           [0011]      FIG. 3  is a perspective view of a bus crossing arm having a guard. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIGS. 1A-2 , a front portion of a bus is indicated generally at  10 , and includes a wheel well cover  12  disposed at an exterior side surface  14  of the bus. Curving around from a front surface  16  to the side surface  14  of the bus is a bumper  18 . The bus  10  also includes a crossing arm  20  attached to the side surface  14  preferably adjacent the bumper  18 . Since the crossing arm  20  is preferably externally mounted to the side surface  14 , it is more easily integrated on an existing bus  10 . While the following description is made with respect to a bus  10 , it is contemplated that the crossing arm  20  can be incorporated on any vehicle. 
         [0013]    The crossing arm  20  is employed for the purpose of preventing people from passing too closely to the front of the bus  10  so that they can be observed crossing the path of the bus by the driver. The crossing arm  20  is telescopically moveable from a retracted position ( FIG. 1A ) to an extended position ( FIG. 1B ). In the extended position, the crossing arm  20  extends generally parallel to the longitudinal axis “A” of the bus, and generally perpendicular to the bumper  18 . 
         [0014]    In the preferred embodiment of crossing arm  20 , the crossing arm includes a plurality of telescoping members  22  that are generally cylindrical and hollow. The telescoping members  22  concentrically nest with each other about a telescoping axis “T” that is generally parallel to the longitudinal axis “A”, while in the retracted position. In the extended position, each of the telescoping members  22 , except for an outermost member  24 , extends from a proximal end  26  of the crossing arm  20  along the telescoping axis “T” to be generally horizontal with respect to the ground. 
         [0015]    A centermost telescoping member  28  has an enclosed distal end  30 , a proximal end  32 , and a body  34  extending between the ends. The distal end  30  is preferably rounded to eliminate sharp corners. A generally annular lip  36  is disposed on an exterior surface  38  of the body  34  at the proximal end  32 . 
         [0016]    Adjacent to and concentric with the centermost telescoping member  28  is the second telescoping member  40 . The second telescoping member  40  is generally similar to the centermost telescoping member  28  in that it has a distal end  42 , a proximal end  44 , and a body  46  extending between the ends. However, the distal end  42  of the second telescoping member  40  has an opening  48  defined by a generally annular shoulder  50 . The opening  48  permits the centermost telescoping member  28  to protrude out from the distal end  42 , and to slide relative to the second telescoping member  40 . 
         [0017]    A generally annular lip  52  is disposed on an exterior surface  54  of the second telescoping member  40 . The second telescoping member  40  is slidable within an adjacent telescoping member  22 . 
         [0018]    In  FIG. 2 , three telescoping members  22  are shown, however it should be understood that any number of telescoping members can be incorporated. In the embodiment with three telescoping members  22 , the second telescoping member  40  of is moveable within the outermost member  24 . 
         [0019]    The outermost member  24  forms an outer housing  56  of the crossing arm  20 . The outermost member  24  is generally cylindrical, having a distal end  58 , a proximal end  60 , and a body  62  extending between the ends. At the distal end  58 , the outermost member  24  has a generally shoulder  64 , similar to the shoulder  50  on the second telescoping member  40 . The proximal end  60  is sealingly engaged with a hose  66 . 
         [0020]    The crossing arm  20  is actuated by an actuator  68 , as known in the art and commercially available. The actuator  68  is supplied with fluid, typically air, from an air tank  70  mounted on the bus  10 , however it is contemplated that the actuator can use any type of fluid (i.e. liquid or gas). The actuator  68  pushes the fluid through the hose  66 , which is connected to a chamber  70  formed within the crossing arm  20 . 
         [0021]    The telescoping members  22  define the generally fluid-tight chamber  72  having a variable volume. When fluid is pushed into the crossing arm  20 , the telescoping members  22  are preferably deployed in sequence with the centermost telescoping member  28  extending outward (in the direction of the arrow) first, then the second telescoping member  40 , in sequence until all members are fully telescoped. With the telescoping members  22  extended, the chamber  72  has increased volume as compared to the retracted position. 
         [0022]    The driver preferably initiates the actuator  68  with an input device  74  located in the cab of the bus  10 . It is contemplated that the actuator  68  can be configured to actuate only when the bus  10  is stopped. The actuator  68  is preferably configured to regulate the force with which the telescoping members  22  are pneumatically deployed outward. Further, the length of extension of the crossing arm  20  can be determined for each individual bus  10 , or can be based on regulations for bus operation. 
         [0023]    The shoulders  50 ,  64  on the larger diameter telescoping members  22  allow each smaller telescoping member  22  to engage the shoulder with the smaller member&#39;s lip  36 ,  52 , thereby preventing the smaller member from disengaging from the crossing arm  20 . It is contemplated that other mechanical stops can be used instead of a lip/shoulder engagement. 
         [0024]    When the telescoping members  22  are retracted, the actuator  68  will draw out the fluid from the chamber  72  and put it back in the tank  70 . This creates a vacuum in the chamber  72 , and each telescoping member  22  will withdraw into the nested position to create a smaller chamber volume. 
         [0025]    The telescoping members  22  are preferably plastic, and more preferably high impact plastic. However, any rigid lightweight material can be used. 
         [0026]    Preferably, the crossing arm  20  is near perfectly horizontal in the extended position when mounted on the side surface  14  of the vehicle  10  horizontally. In other words, the telescoping members  22  preferably do not sag when they are extended. It is preferable for the crossing arm  20  to be straight and rigid on windy days when the arm is likely to be buffeted about by cross winds. 
         [0027]    It is contemplated that additional lips or other mechanical structures can be added along the length of the telescoping members  22  to keep the crossing arm  20  generally aligned with the telescoping axis “T”. For example, an additional shoulder/lip at the distal end of each telescoping member  22  (with the exception of the centermost member  28 ) will counteract the bending moments of the telescoping members  22  distal from it. The shoulder/lip at the distal end of the outer member  22  would interface with the shoulder/lip of the proximal inner tube, thus preventing the segments from shooting out of the crossing arm, and also reinforcing the chamber seal. Alternately, the lip can be thicker along the length of the telescoping member  22 . Further, the amount of fluid deployed into the chamber could also act to keep the deployed arm generally straight. 
         [0028]    Referring now to  FIG. 3 , a guard structure  76  is attached to or integrally formed with the crossing arm  20 , and specifically, the outermost member  24 . The guard structure  76  is configured to prevent objects from snagging on the crossing arm  20  or getting caught between the crossing arm and the bus  10 . 
         [0029]    The guard structure  76  includes a generally “wedge”-shaped body  78  that extends from the crossing arm  20  to the side surface  14  of the bus  10 . The body  78  includes a front surface  80 , a back surface  82  configured for attachment to the vehicle  10 , a side surface  84  attached to the crossing arm  20 , an upper surface  86  and a lower surface  88 . The front surface  80 , the upper surface  86  and the lower surface  88  are preferably smooth. 
         [0030]    While particular embodiments of the present crossing arm have been shown and described, it will be appreciated by those skilled in the art that changes and modifications may be made thereto without departing from the invention in its broader aspects and as set forth in the following claims.