Visual warning signal for a locomotive

A visual warning system for a locomotive is disclosed which includes a signal unit mounted on the locomotive and connected by sensing means to an audible warning device on the locomotive, such as a horn. The visual warning signal unit is thus actuated whenever the horn is sounded. The signal unit comprises a stroboscopic-type lamp assembly and flashing circuitry with a coating of phosphorescent material surrounding the lamp to extend the perceived duration of each flash of the lamp. The system may also include a delay for maintaining the flashing of the visual warning signal unit after the horn has been deactuated.

BACKGROUND OF THE INVENTION 
1. Field of the invention 
This invention relates to warning signals, and particularly signals for use 
on railroad locomotives. 
2. Description of the Prior Art 
To warn pedestrian and vehicular traffic of the approach of a locomotive at 
a railroad grade crossing, safety regulations have been established with 
respect to the operation of the locomotive. Present laws require the train 
operator or engineer when approaching a crossing to illuminate the 
locomotive headlamp, to ring the bell, and to sound the horn or whistle in 
a prescribed form. To further warn crossing traffic, road crossings also 
often have on-site protective devices such as cross-arms, stop lights, red 
signal lamps, and gates. The effectiveness of these warning devices is 
vital, since heavy freight or passenger trains traveling at track speed 
usually cannot be brought to a stop in time to avoid a collision with a 
vehicle or person who has not observed the existing signals and warnings. 
In many cases, the existing warning signals are inadequate. Statistics 
published by the U.S. Government, Department of Transportation, Federal 
Railroad Administration show that approximately 1500 to 1800 people are 
killed and between 3800 and 4000 are injured each year at railroad grade 
crossings. These accident rates have remained fairly constant over the 
last few years while train traffic has declined and vehicular traffic has 
increased. 
In an attempt to provide pedestrian and vehicular traffic with a better 
warning of the approach of a locomotive, additional signal lights have 
heretofore been placed on locomotives. Typically, such warning lights 
mounted on the front of locomotives have included mechanical apparatus for 
providing lateral movement to the lights or to oscillate the lights to 
increase the effect of the warning signal. However, it has been inherently 
expensive to manufacture such devices because of the intricate 
relationship between the various components and the need for a motorized 
source of power to drive the apparatus which moves the light in the 
desired pattern. In addition, the various components required precise 
assembly and adjustment to assure that the desired pattern of the light 
beam would be established at the proper range and position in the path of 
the locomotive. 
More recently, the mechanized devices have been replaced by electronic 
circuitry which turns the warning lights on and off. Examples of such 
electronic systems are shown in U.S. Pat. No. 3,113,293 issued to R. F. 
Breese et al., and U.S. Pat. No. 3,908,179 issued to A. C. Heehler et al. 
The electronic circuitry in these devices, however, comprised simple 
on-off devices which alternately supply power to the light and deactuate 
the light to produce a flashing effect. 
With all of the prior art visual warning signals for locomotives, the 
effectiveness of the signal has been limited by the brightness of the 
lamp. With mechanically or electrically oscillating signals, the distance 
over which the signal was effective has depended upon the relative 
strength of the lamp, and this, in turn, has been limited by the amount of 
power supplied to the lamp by the locomotive electrical system. An 
extremely bright lamp has been impractical since it would produce an 
extremely large drain on a locomotive electrical power supply. 
In addition any such warning signal is, of course, completely ineffective 
if it is not used. The continual flashing of a warning light on the 
locomotive is extremely distracting to the locomotive operator or 
engineer. Therefore, any such signal must be actuated each time the 
locomotive approaches a grade crossing. However, if the operator or 
engineer neglects to actuate the signal, any benefit of such a signal is 
lost. 
SUMMARY OF THE INVENTION 
The disadvantages and shortcomings of the prior art are overcome by the 
visual warning signal for locomotives of the present invention. 
It is among the objects of this invention to provide a visual warning 
system for a locomotive which is connected to an audible warning device on 
the locomotive, such as the horn, whereby the visual warning system is 
automatically actuated when the horn is sounded by the locomotive operator 
or engineer, as is required whenever the locomotive approaches a grade 
crossing, so that the operator or engineer is not required to selectively 
actuate the visual warning signal and so that the signal does not 
continually flash to the distraction of the operator. 
Another object of this invention is to provide a high intensity 
stroboscopic-type lamp assembly for use in a visual warning system on a 
locomotive to greatly increase the effective distance of the warning 
signal over that possible by conventional lamps having simple electronic 
on-off oscillating or triggering circuitry. 
Another object is to provide a stroboscopic-type visual warning signal unit 
for a locomotive in which the unit includes a coating of phosphorescent 
material on a portion of the housing around the lamp, the phosphorescent 
coating effectively extending the perceived duration of each flash of the 
stroboscopic-type lamp. 
These and other objects are accomplished by the locomotive visual warning 
system of the present invention which includes a signal unit mounted on 
the locomotive. The visual warning signal unit includes a 
stroboscopic-type lamp and associated flashing circuitry. Means for 
triggering the signal unit are connected to sensing means on an actuatable 
audible warning device on the locomotive, such as a horn. The visual 
warning signal unit begins flashing whenever the audible warning device 
sounds. The system may also include delay means for maintaining the 
flashing of the visual warning signal unit after deactuation of the 
audible warning device. Preferably, the signal unit also has a coating of 
phosphorescent material surrounding the lamp. The system may also include 
switch means connected to the locomotive power supply and the visual 
warning signal unit for actuating the visual signal independently of the 
actuation of the audible warning device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring more particularly to the drawings and initially to FIGS. 1-6, 
there are shown conventional railroad locomotives having the visual 
warning system of the present invention. A general purpose locomotive 10 
(FIGS. 1,2) which is capable of running in either direction may have 
visual warning signal units at both ends of the locomotive, a unit 11 
mounted at the front end and a unit 12 mounted at the rear end. Each unit 
11 or 12 may be either a unidirectional signal unit 13 (FIG. 1) mounted on 
the end of the locomotive directly below the headlamp 14, or a 
multidirectional unit 15 (FIG. 2) mounted on top of the locomotive near 
the end. For a switcher locomotive 16, as shown in FIGS. 3 and 4, a front 
signal unit 11 and a rear signal unit 12 may also be provided. The units 
11 and 12 may be unidirectional units 13 (FIG. 3) installed on each end of 
the locomotive or multidirectional units 15 mounted on top at each end of 
the locomotive. 
Sometimes it may not be necessary to install signal units at both ends of 
the locomotive. Many locomotives operate predominantly in one direction, 
such as the traditional "covered wagon" locomotive 17 shown in FIGS. 5 and 
6. The locomotive 17 has a single front visual warning signal unit 11 
which may be either a unidirectional unit 13 (FIG. 5) located on the front 
of the locomotive directly below the headlamp 18 or a multidirectional 
unit 15 (FIG. 6) located on top of the locomotive near its forward end. 
With locomotives which operate in both directions, a single multidirection 
unit may be mounted on top in the middle of the locomotive. 
The unidirectional unit 13 is shown in greater detail in FIGS. 7 and 8. The 
unit comprises a stroboscopic-type flash lamp 20 mounted in a base 21 
having a standard octal socket and covered with a protective glass cover 
22. The lamp 20 is typically a flash tube filled with xenon or other inert 
gas such as argon or krypton. To direct the light produced by the lamp 20 
toward the direction of travel, a parabolic reflector 23 is mounted behind 
the base 21. The base 21 and reflector 23 are mounted on a circular lamp 
assembly support 24 to which is attached a cylindrical casing 25 
containing the stroboscopic-type flashing circuitry. The flashing 
circuitry in the casing 25 is connected by wires or cables (not shown) to 
the locomotive electrical supply circuitry as hereinafter described. The 
support 24 is mounted over a heavy metal cylindrical base 26 which may be 
of cast aluminum or rolled steel. The base 26 is attached to the end of 
the locomotive by L-shaped mounting ears 27 having holes 28 for the 
insertion of fasteners. 
The assembly comprising the lamp 20 and reflector 23 is mounted in a 
housing 30 which extends from the casing 26 and surrounds the lamp cover 
22 and reflector 23. The housing 30 comprises a frusto-conical interior 
surface 31 which is coated with a phosphorescent material as hereinafter 
explained, and a cylindrical outer surface of the base 26. The housing 30 
is covered by a clear plastic convex lens 33 mounted over the open forward 
end of the housing 30 to protect the interior of the housing from damage 
by weather while permitting the exit of light from the lamp 20. The lens 
33 is mounted on a hinge 34 to permit the lens 33 to be opened to gain 
access to the interior of the housing 30 such as when necessary for 
changing the lamp 20. The lens 33 is held in the closed position by a 
clasp 35. 
The stroboscopic-type flash lamp 20 and the associated flashing circuitry 
are otherwise conventional and well-known, and are widely used for 
photographic, stroboscopic and like purposes. The known flashing circuitry 
essentially comprises a capacitor arranged to be charged by the power 
supply and to be subsequently discharged through the flash tube to result 
in a short or instantaneous ionic discharge current through the tube of 
high peak value, accompanied by a flash of high instantaneous light 
intensity. 
Due to the extremely short duration of the flash produced by the lamp, the 
interior surface 31 of the housing 30 is coated with a phosphorescent 
paint or other similar material. When the lamp 20 flashes, the 
phosphorescent coating on the interior surface 31 absorbs a portion of the 
light produced by the lamp and then slowly emits this light after the lamp 
has darkened. The coating effectively increases the perceived duration of 
the flash and thus make the warning light more effective. 
An alternative design for the unidirectional signal unit 13 is the unit 15 
shown in FIGS. 9 and 10 which is capable of displaying a visual warning in 
all directions. The multidirectional unit 15 comprises a stroboscopic-type 
lamp 37, typically a xenon flash tube, mounted in a base 38 having a 
standard octal socket and protected by a glass cover 39. The base 38 and 
cover 39 are mounted on a generally cylindrical base 40 which contains a 
casing 41 containing the stroboscopic-type flashing circuitry. At its 
lower end, the base 40 has a plurality of L-shaped mounting ears 42 having 
holes 43 to allow the unit to be mounted on the top of a locomotive by 
appropriate fasteners. 
Extending upwardly from the base 41 is a clear plastic dome 45, typically 
of Lexan polycarbonate resin material. To permit changing of the lamp 37 
if necessary, the dome 45 is removably attached to the base 41, such as by 
mechanical engagement of the lower rim of the dome into a corresponding 
groove in the upper portion of the base. The interior of the dome 45 is 
divided into quadrants by reflecting partitions 46 which extend 
perpendicularly to each other as shown in FIG. 10. The partitions 46 have 
a central U-shaped recess 47 to provide clearance for the lamp cover 39. 
Each side of each of the partitions 46 is coated with phosphorescent paint 
or other phosphorescent material similarly to the coating of the interior 
surface 31 of the housing 30 of the unidirectional warning unit 13. 
To permit either form of signal unit to be automatically actuated as the 
locomotive approaches a grade crossing, the visual warning system of this 
invention includes means attached to the locomotive horn, bell, whistle, 
or other audible warning device to actuate the visual signal unit whenever 
the audible warning unit is actuated, since an audible signal is generally 
always sounded as the locomotive approaches the crossing. Most locomotives 
use as an audible warning device a horn, such as the horn 50 shown in FIG. 
8. The typical horn 50 is connected to a conduit 51 leading from the 
locomotive air supply, which is typically 140 psi, through a horn 
actuating valve 52. The valve 52 has control means 53 for actuation of the 
valve and thus for actuation of the horn by the locomotive operator or 
engineer. Between the valve 52 and the locomotive horn 50, the present 
invention provides T-fitting 54. An electrical pneumatically operated 
pressure switch 55 is connected to the T-fitting 54. When the valve 52 is 
actuated using the control means 53 and air is supplied to the horn 50, 
the pressure switch 55 is actuated by the increase in air pressure through 
the T-fitting 54. 
The connection of the pressure switch 55 in the actuating means for the 
visual warning unit is shown in the electrical schematic diagram of FIG. 
12. The visual warning system of the present invention is powered by the 
locomotive electrical supply 57 which is typically 74 volts DC. The visual 
warning system may comprise a front visual warning signal unit 11 and a 
rear unit 12, each having its respective lamps 58 and 59 and associated 
stroboscopic-type flashing circuitry 60 and 61. Each of the signal units 
11 and 12 may be either unidirectional units, such as unit 13, or 
multidirectional units, such as unit 15, mounted either on or near the 
front and the rear of locomotive, as shown in FIGS. 1-4. One terminal from 
each of the flashing circuitries 60 and 61 is connected directly to the 
negative side of the locomotive electrical supply 57. The other terminal 
from each of the flashing circuitries 60 and 61 is connected to the 
locomotive headlamp selector switch 62. Standard railroad safety 
regulations require the headlamp to be illuminated as the locomotive 
approaches the crossing. The switch 62 which is existent in conventional 
locomotive electrical systems is used to select which of the front or rear 
locomotive headlamps, such as headlamps 14 in FIGS. 1 and 2, are actuated 
depending on the direction of travel of the locomotive. If the forward 
direction of the locomotive is toward the front of the unit, the front 
headlamp is selected by the operator at the switch 62, and the front unit 
flashing circuitry 60 is connected to the positive side of the locomotive 
electrical supply 57 through the switch 62, so that the front mounted 
signal lamp 58 flashes when the horn sounds. Alternatively, if the 
locomotive is traveling in the opposite direction, the rear headlamp would 
be selected on the switch 62 actuating the rear warning unit 12. 
The horn actuated switch 55 is connected across the electrical supply 57 in 
series with a time delay relay 64. The relay 64 operates a contact 65 
connected between the headlamp selector switch 62 and the positive side of 
the locomotive electrical supply 57. The time delay produced by the relay 
64 is adjustable and begins as soon as switch 55 opens. Thus when switch 
55 closes, the time delay relay 64 is energized to close the contact 65, 
and after the switch 55 opens, the contact remains closed for an 
adjustably set predetermined period of time, so that the visual warning 
unit 11 or 12 selected by the switch 62 remains activated for a sufficient 
period of time after the horn has been sounded to give an adequate visual 
warning to pedestrians and the operators of vehicles at the crossing to 
which the locomotive is approaching. 
The stroboscopic-type flash lamp may have a luminous intensity of as much 
as 12,000,000 candle power in the ultraviolet and visual region of the 
spectrum. Because, however, the signal unit uses a stroboscopic-type 
flashing circuit, the unit when actuated requires only approximately 1.9 
amperes of current from the 74 volt DC locomotive electrical supply. This 
added 1.9 ampere load is insignificant and can be assumed by the headlamp 
circuit with no difficulty. 
If desired, a manual push button switch 66 may be provided parallel to the 
horn actuated pneumatic pressure switch 55 to permit the visual warning 
system to be activated without sounding the locomotive horn. When the 
manual button switch 66 is closed and opened, the relay 64 is energized, 
closing the contact 65 for an adjustably set time. 
Instead of the time delay relay 64 and contact 65, a solid state time delay 
device may be utilized. Both electromechanical and solid state electrical 
timer devices are well-known and commercially available. 
In lieu of the horn actuated pneumatic pressure switch 55, a sound actuated 
switch could be employed. Such a switch would be located in the horn or 
bell area, and would close or open when a predetermined level of sound is 
exceeded. The sound actuation level would be selected so that the 
locomotive horn or bell would provide the sound needed to actuate the 
switch. 
If only one visual warning unit is used, such as a single multidirectional 
unit 15 mounted in the middle of the locomotive, the connection through 
the headlamp selector switch 62 would be omitted so that the single 
warning unit would be actuated whenever either switch 55 or 66 is closed, 
and contact 65 is closed. 
The effect of the phosphorescent coating on the housing interior surface 31 
or the sides of the partitions 46 is graphically shown in FIG. 13. The 
data of FIG. 13 was recorded from oscilloscope tracings in tests in which 
a photovoltaic cell was connected to a visual warning unit of the present 
invention. The voltage output of the cell is proportional to the amount of 
light received by the cell. Line 68 indicates the recording of a flash 
from a warning unit without the phosphorescent material. The light output 
from the unit peaks at 0.56 to 0.575 volts and has a duration of a 
slightly over 3 milliseconds. Line 69 is a recording of a flash from a 
unit with phosphorescent material. The peak light output from this unit is 
just below 0.6 volts and lasts approximately 4 milliseconds. Therefore, 
the flash unit with phosphorescent material yields approximately a 25% 
increase in perceivable flash duration. 
Tests using a typical stroboscopic-type flash unit and its ancillary 
equipment under normal operating conditions has shown such a unit to have 
a life expectancy exceeding 5 million flashes. At a design flash rate of 
about 60 flashes per minute, flash tube life expectancy is thus in excess 
of 1,400 operating hours. 
The effect of the flashing visual warning signal of the present invention 
is to draw the attention to the approaching locomotive. Peripheral vision 
is the portion requiring stimuli by this situation since the driver or 
pedestrian is more intent viewing forward toward the path in which he is 
traveling. The human eye requires very little activation to pick up a 
peripheral vision image and attract the subject's attention to the source 
of the light. One of the strongest attractions to the peripheral vision is 
a flashing light such as a turn indicator or a roadside neon sign. When 
the image of an object, such as an intense flash, is perceived by the 
peripheral vision, the eyes swing involuntarily toward the flash so that 
the object can be perceived in detail. A flashing light of great 
brilliance such as approximately 12,000,000 candle power provided by this 
invention and with persistence is a powerful stimulus to the peripheral 
vision, a greater stimulus than a steady light. 
While the extremely short pulse duration of the stroboscopic-type lamp is 
its principal advantage in stroboscopic and photographic uses, it has also 
proven in the past to be its main shortcoming when used as a visual 
warning. The human eye also possesses a phenomenon known as persistence 
whereupon a bright light or shape is retained in memory. Treating the 
inside of the housing or the partitions with a phosphorescent material 
greatly increases the persistence effect of the visual warning. 
In operation, as the locomotive approaches the grade crossing, the operator 
in accordance with standard safety regulations illuminates the headlamp in 
the direction of travel by actuating the headlight selector switch 62 and 
actuates the control means 53 to sound the horn in a prescribed form, 
usually two long, one short, finally one long peal, the last occurring as 
the locomotive passes over the crossing. When the horn sounds, the horn 
actuated pneumatic pressure switch 55 closes as it senses air being 
supplied to the horn 50 through the T-fitting 54 (FIG. 11). The closing of 
the switch 55 allows current to flow through the relay 64, closing the 
contact 65 (FIG. 12). After the control means 53 is released and the horn 
stops, the switch 55 opens, but the time delay maintains the contact 65 
closed for a predetermined duration, preferably about 15 seconds. While 
the contact 65 is closed, power is supplied to the visual warning signal 
unit 11 or 12 selected by the headlamp selector switch 62 according to the 
direction of travel of the locomotive, or if only one unit is used, power 
is supplied to that visual warning unit. The lamp in the selected unit is 
activated and flashes, preferably at a rate of one flash per second during 
the 15 second period and is reactivated for 15 seconds of flashing each 
time the horn is sounded. In practice, with the headlamp illuminated as 
required by law and the horn being sounded also as required by law, each 
peal of the horn will automatically initiate about 15 seconds of periodic 
flashing by the lamp in the visual warning signal unit with automatic 
shut-off at the end of this period. The visual warning would commence well 
in advance of the approach of the locomotive to the crossing and would 
last until well after the locomotive has passed through the crossing. The 
unit thus operates automatically only when needed, and does not operate to 
the distraction of the operator except when the locomotive approaches a 
crossing. 
While the invention has been shown and described with respect to specific 
embodiments thereof, these are intended for the purpose of illustration 
rather than limitation, and other modifications and variations will be 
apparent to those skilled in the art all within the intended scope and 
spirit of the invention. Accordingly, this patent is not to be limited to 
the specific embodiment herein shown and described nor in any other way 
which is inconsistent with the extent to which the progress in the art has 
been advanced by this invention.