Abstract:
An apparatus for operating a reciprocating arm vehicular safety device with a lock for preventing inadvertent deployment of the reciprocating arm. The apparatus has a rotor provided with retaining fingers for engaging the reciprocating, rotatable between locked and unlocked positions. When the reciprocating arm is retracted the rotor rotates to the locked position, and drive circuitry deactivates the device in response to stalling of the rotor drive motor.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to safety devices. In particular, this invention relates to a method and apparatus for deploying and retracting vehicle safety devices such as stop signs and crossing gates.  
         BACKGROUND OF THE INVENTION  
         [0002]    Vehicles such as school buses serve to pick up and discharge passengers. When passengers are discharged from the front door of the bus to the side of a road, the passengers may attempt to cross the road immediately in front of the bus. This poses a safety risk, particularly with school-age children, as the road immediately in front of the bus may be in the bus driver&#39;s blind spot, i.e. outside the bus driver&#39;s range of vision. Accordingly, safety measures such as crossing gates mounted on the front of the bus have been employed for many years. An example is shown in U.S. Pat. No. 5,406,250 issued Apr. 11, 1995 to Reavell et al., which is incorporated herein by reference.  
           [0003]    These crossing gates are typically hinged to the front of the bus at the side nearest the front door. In the retracted state, the crossing gate is held parallel to the front of the bus. When the bus stops and the front door is opened, the crossing gate is extended until it is substantially perpendicular to the front of the bus, effectively providing a barrier at the side of the road of typically at least one meter. Discharged passengers who wish to cross the road must walk around the crossing gate, causing them to pass through the driver&#39;s range of vision. After the passengers have passed beyond the front of the bus, the crossing gate is retracted.  
           [0004]    An example of a prior art retraction mechanism is U.S. Pat. No. 4,816,804 issued Mar. 28, 1989 to Reavell, which is incorporated herein by reference. The apparatus controlling the safety device, in the case of U.S. Pat. No. 4,816,804 a school bus stop sign, is automatically responsive to the opening and closing of the bus door such that when the door is opened, the apparatus swings the hinged sign to its extended position, and when the door is closed, the apparatus returns the sign to its retracted position. The apparatus comprises a unidirectional motor coupled to the hinged sign through an eccentric drive and a link arm. The link arm is provided with a preloaded, helical compression spring which absorbs the shock of mechanical leverage.  
           [0005]    However, apparatus such as these do not prevent inadvertent deployment of the safety device. Although a compression spring in the link arm can help to prevent excessive forces from damaging the mechanical linkages on the safety device, it is not able to prevent unintended deployment of the safety device when the device is exposed to high winds. Wind may catch the safety device, especially in the case of a gate, and partially or fully deploy the gate or even damage the device. Particularly if the bus is in motion, such accidental deployment of the gate is a significant hazard. Even when the bus is parked, the gate is more susceptible to breakage and damage from high winds when extended inadvertently.  
           [0006]    One solution to this problem has been to employ an electromagnetic device to hold a crossing gate in the retracted position. Such an electromagnetic device would be activated while the safety device is in the retracted position, and deactivated when the safety device is to be deployed. However, an electromagnetic device can only be employed while the bus is in operation, because the power required to energize the electromagnet is supplied by the vehicle electrical system. This is not a satisfactory solution for use when the bus is not in operation and the power is shut off and parked, for example where high winds or storms strike overnight. Furthermore, the electromagnetic device cannot detect when the gate does not fully retract (for example if an obstruction becomes trapped between the gate and the vehicle body), nor can it compensate for slight misalignment or deviations in the path of retraction.  
           [0007]    It would accordingly be advantageous to provide a device for engaging a reciprocating arm such as a safety gate, such that in the retracted position the arm is positively engaged by mechanical means. It would further be advantageous to provide such a reciprocating arm with means for monitoring the position of the arm to detect when the arm is fully retracted and the locking mechanism is properly engaged.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention provides an apparatus for operating a vehicle safety device comprising a reciprocating arm, which allows the reciprocating arm to be locked in the retracted position. The reciprocating arm is mounted to a drive motor, which extends and retracts the arm, connected to a drive circuit. The locking mechanism comprises a rotor provided with at least one retaining finger defining a hook for engaging the reciprocating arm. The rotor is rotatably mounted to a drive motor in the path of retraction of the arm, and connected to the drive circuit. When the reciprocating arm has reached the retracted position, the drive circuit rotates the rotor in a locking direction, until the retaining finger engages the reciprocating arm. When the reciprocating arm is to be moved to the deployed or extended position, the drive circuit activates the rotor drive in the unlocking direction until the rotor releases the reciprocating arm, and then activates the reciprocating arm drive to deploy the arm.  
           [0009]    The invention further provides a means for monitoring the status of engagement of the rotor, so that if the reciprocating arm is not fully retracted when the rotor drive is activated to engage the reciprocating arm, the rotor will continue to rotate in the locking direction, and the reciprocating arm continues to retract, until the rotor drive engages the arm and the circuit senses that the rotor drive has stalled.  
           [0010]    The present invention thus provides an apparatus for operating a safety device comprising an arm having extended and retracted positions, comprising: a drive motor for moving the arm between the extended and retracted positions; and a lock for engaging the arm in the retracted position, comprising a rotor mounted in a path of retraction of the arm, having a locked position and an unlocked position, and comprising at least one retaining finger for engaging the arm in the locked position; a drive motor for rotating the rotor between the locked and unlocked positions; and a drive circuit for operating the arm drive motor and the rotor drive motor, comprising a circuit for sensing stalling of the rotor drive motor and deactivating the drive circuit in response thereto.  
           [0011]    The present invention further provides an apparatus for operating a safety device comprising an arm having extended and retracted positions, comprising: a drive motor for moving the arm between the extended and retracted positions; and a lock for engaging the arm in the retracted position, comprising a rotor mounted in a path of retraction of the arm, having a locked position and an unlocked position, and comprising a pair of opposed retaining fingers for engaging the arm in the locked position, the retaining fingers having hooked ends for engaging over edges of the arm in the locked position, a distance between the hooked ends being greater than a height of the arm; a drive motor for rotating the rotor between the locked and unlocked positions; and a drive circuit for operating the arm drive motor and the rotor drive motor; whereby when the rotor is rotated to the unlocked position the arm can be extended through an opening between the hooked ends of the retaining fingers.  
           [0012]    In further aspects of the apparatus of the invention: each retaining finger comprises a hooked end adapted to engage the arm; the rotor comprises two retaining fingers disposed in opposition; the arm comprises bevelled upper and lower edges; when the apparatus is in the retracted position the drive circuit periodically activates the rotor drive motor in a locking direction; to extend the arm, the arm drive motor is activated after the rotor drive motor; a stop is provided in a path of rotation of the rotor, whereby the rotor cannot rotate beyond the stop in an unlocking direction; and/or the stop comprises a slanted edge whereby the rotor can rotate beyond the stop in a locking direction.  
           [0013]    The present invention further provides a method of operating a safety device comprising an arm having extended and retracted positions, comprising the steps of: a. moving the arm from an extended position to a retracted position; b. rotating a rotor mounted in a path of retraction of the arm, the rotor having a locked position and an unlocked position and comprising at least one retaining finger for engaging the arm in the locked position; and c. sensing stalling of the rotor and deactivating the device in response thereto.  
           [0014]    In further aspects of the method of the invention: the rotor comprises at least one retaining finger comprising a hooked end adapted to engage the arm and stall the rotor drive motor; the rotor comprises two retaining fingers disposed in opposition; and/or the method comprises the additional step of, when the apparatus is in the retracted position, periodically activating the rotor drive motor in a locking direction. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    In drawings which illustrate by way of example only a preferred embodiment of the invention,  
         [0016]    [0016]FIG. 1 is a perspective view illustrating the reciprocating arm of the invention mounted to the front of a school bus,  
         [0017]    [0017]FIG. 2 is a front elevation showing the locking mechanism in the locked position,  
         [0018]    [0018]FIG. 3 is an end elevation showing the locking mechanism in the locked position,  
         [0019]    [0019]FIG. 4 is a front elevation showing the locking mechanism in the unlocked position,  
         [0020]    [0020]FIG. 5 is a partially exploded top cross-section showing the locking mechanism in the unlocked position, and  
         [0021]    [0021]FIG. 6 is a schematic diagram showing the drive circuit. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0022]    [0022]FIG. 1 illustrates a typical school bus  10 , having safety devices in the nature of a stop sign  12 , and a crossing gate  20  mounted on the front of the bus  10 , typically to the front bumper  16 . Both of these safety devices deploy to the extended position when the front door  14  of the bus  10  is opened to take on or discharge passengers. When the front door  14  of the bus  10  is closed, the stop sign  12  and crossing gate  20  are returned to the retracted position. The invention will be described in the context of the crossing gate  20 , however it will be appreciated that the invention can be applied to other reciprocating or retractable devices and the invention is not limited in this regard.  
         [0023]    The crossing gate  20  is mounted to the front of the bus  10  near the door  14 . The arm  22  of the crossing gate  20  is sufficiently long that, when extended, it creates a barrier which effectively prevents discharged passengers from walking through the driver&#39;s blind spot immediately in front of the bus  10 . The gate  20  is mounted to a gate drive motor  24  that deploys and retracts the arm  22 , which is typically housed in a sealed housing that in turn is mounted to the exterior of the bus. One suitable mechanism for deploying and retracting a crossing gate of this type, by way of example only, is described in U.S. Pat. No. 5,406,250 issued Apr. 11, 1995 to Reavell et al, which is incorporated herein by reference. FIG. 1 illustrates the retracted position of the gate  20  in solid lines and the extended or deployed position of the gate  20  in phantom lines.  
         [0024]    The invention comprises a novel gate lock  30  for engaging and supporting the arm  22  in the retracted position, illustrated in FIGS.  2  to  5 . The gate lock  30  comprises a rotor  40  having at least one retaining finger, and preferably two retaining fingers  42 ,  44  disposed in opposition about a hub  41 . The retaining fingers  42 ,  44  are preferably formed integrally from a single piece of resilient material, such as ⅛″ spring steel wire, with a central loop  43  which engages around a hub  41 . Each retaining finger  42 ,  44  respectively comprises a hooked end  42   a ,  44   a  dimensioned to engage over the top and bottom edges, respectively, of the gate arm  22 , as best seen in FIG. 3. The hooked ends  42   a ,  44   a  of the rotor  40  are oriented forwardly of the hub  41 , and the distance between the hooked ends  42   a ,  44   a  is greater than the height of the gate arm  22 , so that the gate arm  22  can retract into the space between the hooked ends  42   a ,  44   a  when the gate lock  30  is in the unlocked position, as shown in FIG. 4.  
         [0025]    The rotor  40  is mounted on a rotating shaft  36  which is driven by a gate lock motor  34  through transmission  35 , housed in a gate lock motor housing  32  which is affixed to the exterior of the bus  10  in any suitable fashion, for example by brackets  38  welded or otherwise attached to the housing  32 , and at any suitable position. The shaft  36  extends through a front face  32   a  of the housing  32 , which is preferably removable for servicing the motor  34  and transmission  35 .  
         [0026]    When the rotor  40  is mounted to the shaft  36 , the retaining fingers  42 ,  44  extend radially outwardly from the hub  41 . A channel is formed between the hooked ends  42   a ,  44   a  of the retaining fingers  42 ,  44  having a sufficient breadth to receive the gate arm  22  when the gate lock  30  is in the unlocked position (i.e. the retaining fingers  42 ,  44  are substantially offset from the horizontal orientation), and the hooked ends  42   a ,  44   a  protrude forwardly of the hub  41  so that the fingers  42 ,  44  can engage the gate arm  22  when the gate lock  30  is in the locked position (i.e. the retaining fingers  42 ,  44  are in a substantially horizontal orientation). The gate lock motor  34  drives the gate lock  30  rotationally between the locked and unlocked positions, in the manner described below.  
         [0027]    Thus, in the unlocked position shown in FIG. 4, the hooked ends  42   a ,  44   a  of the fingers  42 ,  44  are clear of the gate arm  22  and provide an opening in the direction of extension of the gate  20 , to thereby allow deployment and retraction of the gate  20 . In the locked position, shown in FIGS. 2 and 3, the hooked ends  42   a ,  44   a  of the fingers  42 ,  44  respectively engage the top and bottom edges of the gate arm  22 , thus restraining the gate  20  from moving from the retracted to the deployed position.  
         [0028]    Preferably the front face  32   a  of the gate motor housing  32  is provided with a stop  33  having a sloped edge  33   a  and a stop edge  33   b , positioned in relation to the rotor  40  such that when the gate lock  30  is rotating in the unlocking direction (clockwise in the embodiment shown) one of the retaining fingers  42 ,  44  (the retaining finger  42  in the embodiment shown) contacts the stop edge  32   b  to prevent rotation beyond a certain point, preferably the point where the rotor  40  is oriented substantially vertically but at least at a point where the hooked ends  42   a ,  44   a  of the fingers  42 ,  44  disengage from the gate arm  22 . When the gate lock  30  is rotating in the locking direction and the retaining finger  42  contacts the stop  33  (i.e. where the gate arm  22  is not fully retracted), the retaining finger  42  will glide over the sloped edge  33   a  of the stop  33 , flexing forwardly as it ramps up the incline, until the finger  42  passes over the stop  33 , which allows the rotor  40  to complete a full revolution if the gate arm  22  is not fully retracted.  
         [0029]    In an alternative embodiment, a spring loaded one-way trip wire (not shown) may be provided on the front face  32   a  of the housing  32  to provide a stop for the arm  22  in the unlocking direction (but not in the locking direction), which will avoid wearing of the rotor  40  as it ramps over the stop  33 . In a further alternative embodiment, the stop  33  can be omitted entirely and the rotor  40  can be allowed to rotate in the unlocking direction throughout the interval that the gate arm  22  is extended, with the gate drive motor  34  reversing its direction when retraction of the gate arm  22  commences.  
         [0030]    Preferably, the gate drive motor  24  and the gate lock motor  34  are controlled using a common electrical source, for example the vehicle generator (not shown), and are coupled to a common drive circuit  50 , illustrated in FIG. 6. The stop sign  12  may also be activated by the same drive circuit  50 , via motor  13 . In one preferred embodiment of the drive circuit  50 : C 1  C 2  are capacitors, 2400 micro farad 16 volt; CR 1 , CR 2 , CR 3  are diodes, 1N540; CR 4  and CR 5  are red and green LEDs, respectively; K 1 , K 2 , K 3 , K 4 , K 5  are relays, single pole double throw 12 volt coil, having wipers W, normally open contacts NO and normally closed contacts NC; M 1  M 2  M 3  are motors, 12 volt; R 1 , R 2 , R 3  are resistors, 10 ohm 10 watt; R 4  is a resistor, 5 ohm 10 watt; and R 5  is a resistor, 1000 ohm ¼ watt.  
         [0031]    The drive circuit  50  operates as follows: In the quiescent state all relays are relaxed. No current is flowing in the drive circuit  50  or the motors  13 ,  24 ,  34 . When the door  12  is opened, the control signal 12 volt door switch DS goes to 12 volts, relay K 1  is picked and held, and K 1 W goes to 12 volts. C 1  is charged to 12 volts via the path K 1 NO, K 1 W, K 2 C 1 , K 2 C 2  and C 1 . K 3  is picked via the path K 1 NO, K 1 W, K 3 C 2 , K 3 C 1  and C 2 . When C 2  charges, K 3  drops out. K 4  and K 5  are picked and held. A 12 volt signal is applied to the common side of the 3 motors  13 ,  24 ,  34 . Ground is applied to the other side of the motor  13  via R 2 ; and motor  34  via R 3  and CR 3 . CR 5  illuminates to indicate to the driver that the crossing gate  20  and stop sign  12  are being deployed.  
         [0032]    When K 3  drops out ground is applied to motor  24  via K 3 NC, K 3 W and R 1 . Motors  13  and  34  immediately rotate at full speed. Motor  24  is delayed until K 3  drops out, after which it rotates at full speed. All motors  13 ,  24 ,  34  rotate to the forward stops: the full extension position in the case of gate drive motor  24  and stop sign drive motor  13 ; and the finger  42  abutting stop edge  33   b  in the case of rotor drive motor  34 . All motors  13 ,  24 ,  34  stall at the forward stops, with R 1 , R 2  and R 3  limiting the current flow thru the motors  13 ,  24 ,  34 .  
         [0033]    When the door  12  is closed by the driver, the  12  volt signal is removed from the door switch DS. K 1 , K 2  and K 5  drop out, and K 1 W goes to ground. C 1  discharges and picks K 2 . C 2  discharges thru CR 2  and does not pick K 3 . K 5 W applies 12 volts to the common side of motors  13 ,  24 ,  34 . Ground is applied to motor  13  via the path K 2 W, K 2 NO, K 4 NC, K 4 W and R 2 ; to motor  24  via the path K 2 W, K 2 NO, K 4 NC, K 4 W K 3 NC, K 3 W and R 1 ; and to motor  34  via the path K 2 W, K 2 NO, K 4 NC, K 4 W, R 3  and R 4 . CR 4  illuminates to indicate to the driver that the stop sign  12  and gate  20  are retracting. All motors  13 ,  24 ,  34  rotate in the reverse direction. Motor  34  rotates at reduced speed because CR 3  is back biased and current must flow thru R 4 , so the crossing gate  20  retracts slowly. As motor  34  is freely rotating it shows a high back EMF to the drive voltage, therefore the junction R 4  and motor  34  is at a low voltage. This potential is fed onto the K 2 C 2  via CR 1  and holds K 2  activated.  
         [0034]    Motors  13  and  24  rotate at full reverse speed, and encounter their reverse stops (the fully retracted position of the stop sign  12  in the case of motor  13 , and the fully retracted position of the gate arm  22  in the case of motor  24 ), where they stall. As motor  34  reaches its reverse stop (engagement with the gate arm  22 ) and stalls, the resistance of motor  34  decreases. Less voltage is applied across motor  34  and the voltage at junction R 4  and motor  34  increases. The increase in voltage is sensed at C 2  via CR 1  and balances the 12 v sensed at C 1  via K 1 W and K 1 NC. K 2  drops out, so K 2 NO goes to floating potential and current flow ceases thru the motors. The indicator CR 4  goes out to indicate to the driver that retraction is complete, and the circuit is returned to quiescent state.  
         [0035]    Thus, under control of a 12 volt signal, all three motors  13 ,  24 ,  34  rotate until physical forward stops are encountered. When the control signal is negated, all three motors  13 ,  24 ,  34  rotate in the reverse direction until physical reverse stops are encountered. Upon the crossing gate drive motor  34  reaching its fully retracted position, the voltage is removed from the motors  13 ,  24 ,  34 . No limit switches or position sensing devices are required, and only the current draw of the stalled crossing gate drive motor  34  is monitored.  
         [0036]    If the gate arm  22  is not fully retracted when the gate drive motor  24  stalls, for example if the gate arm  22  is obstructed and prevented from fully retracting, the gate arm  22  is not in position to block rotation of the gate lock drive motor  34  and stall the gate lock drive motor  34 , so the gate lock  30  will continue to rotate in the locking direction and CR 4  will remain illuminated. The gate drive motor  24  thus continues to force the gate  20  in the retraction direction. All three motors  13 ,  24 ,  34  thus continue to operate until the gate lock  30  is securely in position engaging the gate arm  22 . This ensures that the driver does not falsely assume the gate is properly retracted and locked merely because the gate lock is indicated as being in the locked position. It will be noted that the top and bottom edges of the gate arm  22  are preferably bevelled, as shown in FIG. 3, so if the gate arm  22  is only slightly shy of the fully retracted position the hooked ends  42   a ,  44   a  will strike the edges of the gate arm  22  and cam down the bevelled edges of the gate arm  22  to draw the gate arm  22  to the fully retracted position.  
         [0037]    In the preferred embodiment, only the gate lock motor  34  and the gate motor  24  are located in housings mounted on the exterior of the bus; the drive circuit  50  is housed within the cabin of the vehicle  10 . Optionally the drive circuit  50  may provide further LEDs to indicate the state of the safety device; for example, for the gate lock  30 , a green LED to indicate when the gate lock  30  is in the locked state and a red LED to indicate when the gate lock  30  is in the unlocked state; and for the crossing gate  20  itself, a green LED to indicate when the gate arm  22  is retracted, and a red LED to indicate when the gate arm  22  is extended.  
         [0038]    A breakaway link assembly such as that described in U.S. Pat. No. 4,816,804 issued to Reavell, which is incorporated herein by reference, may be used in the safety device to sense external pressure on the gate arm  22 . When external force is applied to the gate arm  22  in either the deployed or retracted positions, for example in windy conditions, the force is transferred to the link assembly. The circuit senses the mechanical external force and checks the drive torque to avoid mechanical damage of the motor  34  or transmission  35 . When the external force is removed from the gate arm  22 , the circuit senses this change and the motor  34  is still connected and continues to drive the gate  20  at its maximum torque.  
         [0039]    In operation, while the bus  10  is moving the gate arm  22  is in the retracted position and engaged by the gate lock  30 , which is in the locked position with the channels engaging the top and bottom edges of the gate, as shown in FIGS. 2 and 3. When the bus  10  stops and the door  12  is opened by the driver, the stop sign, gate and gate lock motors  13 ,  24 ,  34  are activated in the manner described above, causing the gate lock  30  to rotate in the unlocking direction and the gate arm  22  to extend to the deployed position. The gate lock  30  continues to rotate until the retaining finger  42  contacts the stop edge  33   b  of the stop  33 . The gate arm  22  is then deployed until fully extended.  
         [0040]    It can be seen in the preferred embodiment that the gate lock  30  does not need to be rotated fully 90° to release the gate arm  22 . However, the hooked ends  42   a ,  44   a  of the fingers  42 ,  44  should engage the gate arm  22  with sufficient overlap that a slight rotation of the rotor  40  due to normal motion of the vehicle  10  will not release the gate arm  22  inadvertently.  
         [0041]    Because the gate lock  30  must be moved to an unlocked state in order to release the gate arm  22 , there is a slight delay in deploying the crossing gate  20 . Where the safety device is used together with a stop sign safety device  12  or warning lights, the stop sign  12  and/or warning lights are activated first, with the gate lock  30 , to warn oncoming motorists to stop. As the stop sign  12  is being deployed, the gate lock  30  is simultaneously moved to the unlocked state, then the gate arm  22  moved to the deployed position.  
         [0042]    Much of the operation of the motor drive circuit  50  can be effected by a microprocessor-based circuit, as will be apparent to those skilled in the art, although this is likely to be a more costly alternative. In a microprocessor-based embodiment, as an additional safety precaution, at all times when the bus ignition is on but the gate  20  is not being deployed or retracted, the motor drive circuit can intermittently pulse the gate lock drive motor  34  to move the gate arm  22  in the retracting direction, in order to verify that the gate arm  22  is properly secured.  
         [0043]    Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention. The invention includes all such variations and modifications as fall within the scope of the appended claims.