Communications: electrical – Land vehicle alarms or indicators – External alarm or indicator of movement
Reexamination Certificate
1994-09-22
2001-04-03
Lefkowitz, Edward (Department: 2736)
Communications: electrical
Land vehicle alarms or indicators
External alarm or indicator of movement
C340S464000, C340S467000
Reexamination Certificate
active
06211779
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to emergency signalling devices, and more particularly to an signalling method and apparatus for an emergency vehicle having a signalling frequency corresponding to the speed of the vehicle.
BACKGROUND OF THE INVENTION
Emergency vehicles such as police cars, ambulances and fire trucks are required to perform under a wide range of driving conditions and at a wide range of speeds. For example, during the time that a police car is in pursuit of a suspect car, the police car may be driven at a high rate of speed for a given time, at a reduced speed while crossing critical intersections, and stopped once the vehicle is halted.
Under these varying conditions, the primary responsibility of the emergency signalling system is to warn the public of the presence of the vehicle, since the emergency vehicle is often driven in a non-standard manner during such extraordinary times. To effectively warn the public, conventional lights and sirens provide recognizable patterns and various colors or tones.
In essence, the flashing or strobing lights of the vehicle are broadcasting information to potential observers such that once detected, the observer is warned of the abnormal driving conditions that may soon be encountered so that appropriate precautionary measures may be taken. For example, light bars, composed of anywhere from two to twelve light elements, wherein each element is ordinarily capable of flashing at a rate of between 60 and 240 flashes per minute (one to four hertz), may be attached to vehicles to broadcast the warning information, as standardized by the Society of Automotive Engineers (SAE J-845, SAE J-595, SAE J-1318) for emergency warning lights. The lights may be filtered so that non-white colors allow the observer to differentiate between the white and red lights of ordinary vehicles and also to differentiate between the types of emergency vehicles. In short, the combination of flashing or strobing lights, at a particular pattern and of a distinguishable color signifies to the public the presence of an active emergency vehicle.
In general, a warning issued by an emergency signalling device attempts to maximize the effectiveness of the warning by including enough information to overcome observational difficulties that are potentially present in the general public. For example, emergency sirens often sweep through a range of frequencies at varying rates. The maximum and minimum frequencies are arranged so as to be within the most efficient detection portion of the human audio spectrum. The purpose of sweeping through a range of frequencies is to ensure that potential human observers will hear the siren over background noises and because many potential observers suffer from hearing loss at certain frequencies.
The rate of sweeping between the frequencies is also chosen to impart information, usually indicative of urgency, to the public. For example, a frequency pattern known as a “Wail” sweeps from approximately a 500 hertz tone to a 1500 hertz tone in ten to thirty sweeps per minute. A frequency pattern known as a “Yelp” sweeps between the same audible tones but at a much faster rate of approximately 150 to 250 sweeps per minute. Thus, the “Yelp” pattern is able to rapidly impart the signalling information, even to persons having limited ability to hear certain frequencies, so that a faster reaction than with the “Wail” tone is possible.
Parallel concepts are available in emergency lighting devices as well. For example, light bars provide a variety of colors in a single light package. These varying colors aid the stimulation of unoccupied visual channels in human observers and overcome visual deficiencies such as color blindness present in some potential observers. Additionally, having a greater number of flashing light elements provides a greater number of flashes to the eye, which potentially results in faster reaction times.
However, even when such flashes are noticed, the speed of the vehicle is somewhat uncertain until the vehicle itself is visually detected from a relatively close range. To some extent, with audible sirens an increase or decrease in volume in conjunction with the frequency shift resulting from the Doppler effect provide some hint of vehicle's relative speed and direction (i.e., velocity) to most observers, however there is no consistent pattern provided thereby that such observers can ordinarily recognize in any significant time. Moreover, non-stationary observers influence these effects with their own velocity, making it even more difficult to deduce an emergency vehicle's velocity from its siren when in motion relative to it. This is because the frequency shift and amplitude change over time will be different to a stationary observer, to an observer moving toward the vehicle and to an observer moving away from the vehicle.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and apparatus for increasing the effectiveness of emergency signalling devices on vehicles by varying the frequency of the device in dependence on the speed of the vehicle.
A further object of the invention is to provide a method and apparatus of the above kind that enables an observer to determine the speed of a vehicle by observing signals produced by the signalling device.
Another object of the invention is to provide a method and apparatus as characterized above that varies the frequency between a maximum and minimum rate.
Briefly, the invention provides an emergency signalling device for broadcasting emergency signals from a vehicle. Mounting means connect the signalling device to the vehicle, and a detector converts the speed of the vehicle to a first electrical signal having information therein corresponding to the speed of the vehicle. Circuitry converts the first electrical signal to a second electrical signal having a repetition rate corresponding to the speed of the vehicle, and circuitry is also provided for maintaining the repetition rate between maximum and minimum rates. Means connect the second electrical signal to the signalling device for broadcasting emergency signals having a variable range of repetition rates corresponding to the speed of the vehicle between maximum and minimum signalling rates.
In one preferred embodiment, the emergency signalling device is provided in an emergency lighting device mounted to the surface of a motor vehicle. The signalling device includes a base and related apparatus for mounting to the surface of the motor vehicle, a flashing light mounted to the base, and a light transmissive housing supported by the base for enclosing and protecting the light. A detector detects the speed of the vehicle, and circuitry responsive thereto controls a flash rate of the flashing light so that the rate varies with the speed of the vehicle between minimum and maximum flash rates.
A method of operating emergency signalling devices mounted to a motor vehicle is also provided, the method comprising the step of generating an emergency signal that is characterized by a repetition of at least one audio tone or the flashing of lights. The rate of repetition of the emergency signal is maintained at a minimum value for speeds of the motor vehicle below a predetermined lower limit and at a maximum value for speeds of the motor vehicle above a predetermined upper limit, and the repetition rate of the emergency signal is adjusted to create a proportional relationship between the repetition rate and the speed of the vehicle for speeds between the lower and upper limits.
Other objects and advantages will become apparent from the following detailed description when taken in conjunction with drawings, in which:
REFERENCES:
patent: 1543704 (1925-06-01), Evelyn
patent: 1589071 (1926-06-01), Hahnle
patent: 2681957 (1954-06-01), Schneider
patent: 2794082 (1957-05-01), Germaine
patent: 2903684 (1959-09-01), McClintock
patent: 3431556 (1969-03-01), Johnson
patent: 3631390 (1971-12-01), Murphy
patent: 3691525 (1972-09-01), McClellan, Sr. et al.
pa
Gibb Richard G.
Graham Paul D.
Federal Signal Corporation
Lefkowitz Edward
Leydig , Voit & Mayer, Ltd.
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