SCHOOL BUS STOP ARM AND DRIVE UNIT THEREFOR
A school bus stop arm and drive unit therefor are disclosed. The stop arm includes a stop sign and a drive unit for moving the stop sign between a retracted position and a deployed position. In some embodiments the stop sign is illuminated. In some embodiments the drive unit includes a controller.
1 . A stop arm for a school bus comprising:
a stop sign; and
a drive unit mountable to a side of the school bus for selectively moving the stop sign between a deployed position and a retracted position, said drive unit comprising:
a motor operably coupled to the stop sign to perform said selective movement,
one or more position sensors operable to detect the presence of the stop sign in the deployed and retracted positions, and
a controller operably coupled to the motor for controlling operation of the motor, the controller configured to, during operation of the motor, (i) monitor one or more operating characteristics of the motor for conditions indicative of an obstruction to movement of the stop sign, (ii) monitor the position sensor for a confirmation signal indicative of the presence of the stop sign in the deployed or retracted position, and (iii), based on the conditions indicative of an obstruction and the confirmation signal, determine if the stop sign has reached one of the deployed and retracted positions or is being obstructed.
2 . The stop arm of claim 1 , wherein the controller is further configured to, on start-up, initiate operation of the motor in a retracting direction to drive the stop sign towards the retracted position and terminate operation in the retracting direction upon detection of conditions indicative of an obstruction and confirmation that the stop sign is in the retracted position from the confirmation signal.
3 . The stop arm of claim 1 , wherein the one or more position sensors comprise a single sensor system to detect both the deployed and retracted positions.
4 . The stop arm of claim 1 , wherein the one or more position sensors comprise at least one limit switch.
5 . The stop arm of claim 4 , wherein the at least one limit switch comprises two limit switches to provide a confirmation signal indicative of the presence of the stop sign in one of a retracted position, a deployed position, transition between the retracted and deployed positions, and an over-travelled position.
6 . The stop arm of claim 1 , wherein the one or more operating characteristics of the motor is at least one of an operating current of the motor and a counter-electromotive force of the motor.
7 . The stop arm of claim 1 , wherein the drive unit comprises a housing defining an interior space of said housing and an enclosed sub-compartment divided from a remainder of the interior space, the motor being positioned within the sub-compartment, wherein at least one of:
(a) the position sensor is contained within said sub-compartment;
(b) a PCB, on which the controller and/or the position sensor are mounted, is contained within said sub-compartment; and
(c) a motor-driven output shaft extends from the sub-compartment in a downward direction through a lower wall of said sub-compartment.
8 . The stop arm of claim 1 , wherein the controller is further configured to apply low impedance between leads of the motor when the controller determines that the stop sign has reached the deployed or retracted position.
9 . The stop arm of claim 1 , wherein the controller is further configured to limit the counter-electromotive force of the motor when the controller determines that the stop sign has reached the deployed or retracted position.
10 . The stop arm of claim 1 , wherein the controller is further configured to apply low impedance between leads of the motor when the controller is in an unpowered state.
11 . The stop arm of claim 1 wherein the controller is further configured to limit the counter-electromotive force of the motor when the controller is in an unpowered state.
12 .- 68 . (canceled)