The present invention relates in general to railroad operations and in particular to systems and methods for controlling railroad highway crossing flashers.
In the railroad industry, a number of different monikers are used to refer to locations where the tracks of a rail line cross a road or highway, including “highway crossing”, “railway crossing”, “grade crossing”, “level crossing”, and “railway crossing”, among others. For purposes of the present discussion, the term “highway crossing” will be used, although any of the terms commonly used in the railroad industry will apply equally well to the following discussion. Whatever term is used, highway crossings are familiar worldwide.
Highway crossings provide a significant hazard to vehicles and pedestrians on the intersecting highway or road, as well as to the trains and their crews, passengers, and cargo. In particular, a moving train cannot quickly stop or significantly reduce its speed in response to an obstacle on the track, such as a pedestrian or vehicle, given its mass. Hence, a ubiquitous strategy has developed over the many years in which the railroads have operated, namely, maintaining clear tracks in advance of oncoming trains.
Active highway crossings are very familiar, at least to those living in the United States. Generally, an electrical track circuit, which transmits either a DC or AC signal through a circuit formed by the pair of rails of the track itself, detects the wheels of a train entering the block or section of track on the approach to the highway crossing. Depending on the speed of the train and its distance from the highway crossing, an associated electrical control system then lowers crossing gates, activates flashing lights, and/or activates bells, depending on the particular system configuration. The control system is typically maintained within a housing or cabinet in the vicinity of the highway crossings.
In conventional highway crossing flasher systems, all of the flashers are typically controlled by a common electrical control circuit. Consequently, the failure of that common electrical control system causes all the flashers to stop flashing. A similar problem exists with regards to the flashing lights on the crossing gates: a failure of the common electrical control circuit causes all the lights on the gate or gate to cease flashing. In both cases, safety at the highway crossing can be significantly compromised.
One embodiment of the principles of the present invention is a railroad crossing warning circuit, which includes a lamp and a signal generator for generating a first signal of a selected frequency. Divider circuitry divides the frequency of the signal to generate second signal at a flashing frequency. A switch responsive to the second signal controls current flow through the lamp and cause the lamp to flash at the flashing frequency.
Another embodiment is a railroad crossing flasher system, which includes first and second lamps, first control circuitry for controlling flashing of the first lamp, and second control circuitry for controlling flashing of the second lamp. The first control circuitry includes a first signal generator for generating a first base signal having a frequency, a first frequency divider for dividing the frequency of the first base signal to generate a first flashing signal having a flashing frequency, and a switch responsive to the first flashing signal for controlling current flow through the first lamp to selectively cause the first lamp to flash at the flashing frequency. The second control circuitry includes a second signal generator for generating a second base signal having a frequency, a second frequency divider for dividing the frequency of the second base signal to generate a second flashing signal having the flashing frequency, and a second switch responsive to the second flashing signal for controlling current flow through the second lamp to selectively cause the second lamp to flash at the flashing frequency. The first and second flashing signals are out-of-phase such that the first and second lamps alternately flash.
A further embodiment of the present principles is a crossing gate lamp control system including first and second crossing gate lamps. A signal generator generates a first signal of a selected frequency and divider circuitry divides the frequency of the first signal to generate first and second complementary output signals each at a flashing frequency. A first switch, which is responsive to the first complementary output signal, controls current flow through the first crossing gate lamp and causes the first crossing gate lamp to flash at the flashing frequency. A second switch, which is responsive to the second complementary output signal, controls current flow through the second crossing lamp and causes the second crossing gate lamp to flash at the flashing frequency alternately with the flashing of the first crossing gate lamp.
Embodiments of the present principles advantageously ensure that a failure of a single controlling circuit or element does not cause all the lamps of a railroad highway crossing warning system to fail. In other words, failures are isolated to a single, or at least a small number, of lamps. In addition, the operations of each pair of lamps, as well as the operations of all of the lamps in the crossing flasher system, are synchronized. These principles are applicable to both flashers, as well as the flashing lights on crossing gates.
For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
Highway crossing 100 is equipped with conventional crossing gates 103a-103b), flasher systems 104a-104b, train motion detectors 105a-105d, and a housing 106 holding conventional highway crossing control systems such as a crossing controller, an event recorder, a cellular communications system, back-up batteries, and battery chargers. Audible warning components, such as bells, may also be provided.
Typically, there are a minimum of eight (8) flashers per highway crossing disposed in pairs. At exemplary highway crossing 100, flasher systems 104a-104b each include three pairs of flashers 107, with two pairs disposed back-to-back on a vertical support and one pair supported by an gantry over the roadway 101 and facing oncoming road traffic. The flashers (lamps) of each pair of flashers 107 alternately flash. Each gate 103 includes three (3) lamps 108, with the tip lamps constantly on when the gate is lowered and the inner pair of lights alternately flash.
One significant disadvantage of conventional flasher control system 200 arises from the use of a common controlling element 202. Specifically, a single fault failure mode of common controlling element 202 results in a failure of all of the lamps of the crossing system (e.g., all lamps 107 of
An exemplary embodiment of the principles of the present invention is flasher control system 300 of
Another significant advantage of flasher control system 300 is that all lamps are synchronized. As discussed further below, all XLFs 301 are activated when power is applied by energy source 201. The leading edge (“pulse”) starts XLFs 301 substantially simultaneously, which synchronizes the alternating flashes of each pair of XLFs 301, as well as the operation of all XLFs 301 in system 300.
A block diagram of a representative XLF 301 is shown in
The principles of the present invention are not limited to embodiments using precision clock signal generator 302, down counter 303, and/or flip-flops 304. In alternate embodiments, other circuits or components may be used, such as microcontrollers, timers, or other circuits suitable for generating synchronized control signals.
One particular exemplary circuit suitable for use as an XLF 301 is shown in
Depending on the desired phase, either the Q or/Q output of flip-flop 304b, as selected by setting the jumper discussed below, drives the gate of a field effect transistor (FET) 305. In response, FET 305 switches the current through the corresponding lamp 107, which is represented by an LED in
In the embodiment of XLF 301 shown in
The principles of the present invention are also applicable to controlling crossing gate lamps 108a-108c on each crossing gate 103a or 103b. In this case, the tip lamp 108a is steady-state on when the corresponding crossing gate 103 is lowered, while the corresponding lamps 108b and 108b alternately flash.
As shown in
An exemplary circuit suitable for implementing XLF 401 is shown in
The Q output of flip-flop 404b drives the gate of a FET 405a and the associated/Q output drives the gate of a FET 405b. When the corresponding gate 103 is down, and the XLF 401 is active, the Q and/Q outputs of flip-flop 404b cause the associated lamps 108b and 108c to alternately flash. In particular, when the Q output is high and the/Q output is low, FET 405a is on and FET 405b is off, such that current flows only through lamp 108c, which turns on. When the Q output is low and the/Q output is high, FET 405 is off and FET 405b is on, such that current flows only through lamp 108b, which turns on.
XLFs 401 operate in a similar matter to XLFs 301, with each circuit triggered by the application of power from energy source 201. As a result, the initial pulse of power from energy source 201 to XLF 401a and 401b synchronizes the flashing of flashing crossing gate lamps 108a and 108b.
In sum the embodiments of the present inventive principles ensure that failures are localized, such that even if some flashers become inoperable, other flashers will remain in operation. As a result, reliability and safety at highway crossing are enhanced.
Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed might be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.
It is therefore contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.
Number | Name | Date | Kind |
---|---|---|---|
4934633 | Ballinger | Jun 1990 | A |
5808545 | Brueggemann | Sep 1998 | A |
7075427 | Pace | Jul 2006 | B1 |
7164892 | Derome | Jan 2007 | B2 |
7688222 | Peddie | Mar 2010 | B2 |
9018850 | Nguyen | Apr 2015 | B2 |
9193367 | Hilleary | Nov 2015 | B2 |
10556604 | Plant | Feb 2020 | B2 |
10883705 | Fox | Jan 2021 | B2 |
Number | Date | Country | |
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20200346676 A1 | Nov 2020 | US |