Electricity: motive power systems – Motor-reversing
Reexamination Certificate
1999-10-01
2001-04-17
Donels, Jeffrey (Department: 2837)
Electricity: motive power systems
Motor-reversing
C049S028000
Reexamination Certificate
active
06218797
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to apparatus and methods employed in conjunction with crossing guard mechanisms. The present invention more particularly relates to use of mechanical and electrical means to enable the safe repair of a crossing guard mechanism, such as a mechanism employed at a railroad crossing.
2. Background Information
It has been known to position crossing guard mechanisms adjacent to certain designated areas to resist the passage of pedestrians, drivers and other individuals into those areas. A crossing guard mechanism positioned adjacent to a locomotive crossing, for example, hinders the unsafe passage of individuals over the railroad tracks when arrival of a train is imminent. Unfortunately, a common problem arises with a crossing guard mechanism when its guard arm is struck by a vehicle, for example, or another disturbance affects the mechanism and the guard arm becomes detached from the mechanism. This event can also adversely affect the control and operating circuitry of the crossing guard mechanism. An example of a highway crossing gate control circuit is provided by U.S. Pat. No. 5,502,367 to Jones, which is incorporated herein in its entirety by reference.
A complication created by this situation is how to move a counterweight arm of the crossing guard mechanism to its “up” or horizontal position in a safe and efficient manner. The counterweight arm is normally employed in a crossing guard mechanism to counterbalance the weight of the guard arm at a common connection point between the two arms. The common connection point provides the mechanical advantage needed to permit the guard arm to be raised and lowered as required. To repair a disabled crossing guard mechanism, the guard arm connection point must be lowered to an accessible position or its “down” position. A connection point on the counterweight arm can then be aligned with a connection point on the guard arm to permit reconnection of the guard arm to the guard mechanism.
Difficulty arises in this situation from the weight of the counterweight arm. The weight of this counterweight arm is proportional to the length of the guard arm and is substantial. The crossing guard system generally becomes unbalanced and disrupted as a result of the unexpected removal of the guard arm. Once the system is unbalanced, substantial mechanical advantage is required to raise the counterweight arm. Furthermore, the operator must be able to raise the counterweight arm in a manner which does not substantially jeopardize his safety and which protects the crossing guard equipment, including its control circuitry, in the event of loss of electrical power to the mechanism while moving the counterweight arm or arms to the “up” position. Without taking protective measures, the counterweight arm can fall in a relatively rapid and uncontrolled manner, possibly endangering the operator and/or causing damage to the crossing guard mechanism.
Maintenance systems have been implemented within crossing guard mechanisms, but these systems generally utilize relatively expensive relays and a number of different components. Many maintenance systems are included within and connected to the normal control and operating circuitry of the crossing guard mechanism. This interdependence between the maintenance system and the usual crossing guard functions inherently lowers the reliability of the normal function of the mechanism.
What is needed therefore are a maintenance system and an associated method which provide safety and reliability advantages that are not obtainable in other designs that rely on a constant source of electrical power to engage relatively complex components such as electromechanical brakes or relays, for example. What is also needed are a maintenance system and an associated method that can be performed simply and reliably to service a crossing guard mechanism. Furthermore, a maintenance system and method are needed that are substantially independent from the operation of the electrical control and operation circuitry of the crossing guard system.
SUMMARY OF THE INVENTION
The present invention provides a crossing guard maintenance system and associated method for use with a crossing guard control system. The crossing guard control system has a motor mechanically coupled to a crossing guard arm and to a counterweight arm or arms to move the arms between their respective up and down positions. This motor is normally electrically connected to the control system, until its polarity is reversed by the maintenance system to provide electrical power for moving the arms. The motor is preferably a permanent magnetic motor.
In the maintenance system of the present invention, a function switch is provided with a “normal” position in which it electrically connects the motor to the crossing guard control system; and, a “maintenance” position in which it energizes the maintenance system of the present invention. This function switch is preferably provided as a double pole double throw switch. A diode is electrically connected to the function switch when in its “maintenance” position. The diode acts as a flyback mechanism to provide a path for current through the motor in the event that the motor becomes a DC generator in a failure mode. Connection of the diode to the motor can be considered to form a motor/diode circuit.
The present invention also discloses a momentary switch that connects the motor/diode circuit to an external electrical power source when the momentary switch is closed. Therefore, when open, the momentary switch does not provide a path for electrical current to flow to the motor/diode circuit; when closed, the momentary switch provides current flow to the motor/diode circuit. The momentary switch can be provided as a pushbutton type switch for alternating between the open and closed positions of the momentary switch. The diode is preferably connected between the motor and the momentary switch to protect the momentary switch from electrical arcs when electrical power supplied to the motor/diode circuit is interrupted by opening the momentary switch.
In addition, the present invention discloses a method for reconnecting a guard arm removed from a crossing guard mechanism having both guard and counterweight arms. The method also includes disconnecting the motor from the crossing guard control system; connecting the motor to a maintenance system as previously described; raising the counterweight arm to an “up” position; maintaining the “up” position of the counterweight arm, such as by use of a lock pin; aligning a common mechanical connection point between the counterweight and guard arms; and, reconnecting the guard arm to the crossing guard mechanism.
Jogging the momentary switch in the method of the present invention is also disclosed for permitting the counterweight arm to be raised after a guard arm failure event. As an additional step, the method of the present invention can include switching the function switch to its “normal” position to resume normal operation of the crossing guard mechanism once maintenance is completed.
It is an object of the present invention to move a counterweight arm of a crossing guard mechanism to its “up” or horizontal position in a safe and efficient manner.
It is an additional object of the present invention to provide substantial mechanical advantage to the crossing guard system by reversing the polarity of the motor employed in the system.
It is an additional object of the present invention to resist injury to an operator performing maintenance on a crossing guard system.
It is an additional object of the present invention to resist damage to the crossing guard system control and operation circuitry.
It is an additional object of the present invention to reduce interdependence between normal crossing guard control and operation functions and the maintenance system to improve the reliability of the control and operation circuitry.
These and other objects of the present invention will be more fully understood from the
Drafts Charles R.
Williamson N. Rodger
Donels Jeffrey
Duda Rina I.
Eckert Seamans Cherin & Mellott , LLC
Houser Kirk D.
Radack David V.
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