Warning light

A hazard warning light for attachment to a vehicle is designed to give the illusion of a rotating lamp of high intensity and is actuable by the driver of one vehicle to alert following cars to the existence of an emergency e.g. a car crash. The light incorporates electronic circuitry.

The invention relates to a warning light, primarily intended for use with 
vehicles but of value in many mobile or fixed situations where it is 
necessary to give a warning that something untoward has happened. For 
convenience, the invention will be described more particularly with 
reference to its application to land vehicles, typically automobiles. 
Experience has taught us that many road accidents, especially multiple 
accidents, occur because travelling cars following a stationary vehicle do 
not realise that the first vehicle has stopped, e.g. crashed. The driver 
of a stopped vehicle has only one safe means to show to following cars 
that there is a hazard to following vehicles - he actuates both the left 
and right turn indicators of his vehicle simultaneously. To a following 
vehicle, however, this signal can have many interpretations but not 
necessarily its intended purpose. The first following car can mask or hide 
the turn indicators of the crashed car and to the driver of the second 
following car or a car in a different lane the stationary car appears to 
be turning as only one flashing indicator is visible. The risk can be 
accentuated where the second vehicle is a large one such as a lorry, bus 
or a coach. In this way multiple pile ups occur. 
It is one object of the invention to provide an improved hazard warning 
light system. It is another object to provide on each vehicle a light 
designed to give the illusion of turning. 
According to one aspect of the invention there is provided a hazard warning 
light comprising a housing having a front light transmitting face, the 
housing containing a support plate having a plurality of light bulbs, 
reflective surfaces being present behind the bulbs, in which the bulbs are 
arranged to operate in pairs as to give the illusion of turning. 
Most preferably the lamps are arranged to give an illumination 
substantially equal to that of a fog light, and are each 5 watts or more. 
Most preferably the hazard warning light is mounted at the rear of a 
vehicle and is preferably associated with a rear fog light which every 
vehicle should have. 
Preferably the hazard light is associated with a fog lamp and the warning 
light may be used together or independently of the fog lamp. The 
illumination caused by the illusion of turning should match that of the 
standard 21 watt fog light. 
The hazard warning light may be actuated in a variety of ways e.g. by a 
specific switch e.g. on the vehicle dashboard or by being in circuit with 
an existing switch such as the horn or it may be wired up to operate even 
when the driver is incapacitated, e.g. by an impact switch. 
The front face of the housing is arranged to transmit light. While the face 
may be transparent, it is preferred that the face be coloured, and red and 
blue are preferred colours. 
The strength of the light bulbs and reflective surfaces and/or the light 
transmitting properties of the front face are so chosen that the illusion 
of turning lights will reach a distance related to the safe stopping 
distance for vehicles travelling at high speed: according to the British 
Highway Code for a vehicle travelling at about 112 km.p.h. (70 m.p.h.) the 
safe stopping distance is 96 meters (315 feet). 
Preferably the light bulbs are arranged in pairs and in circuit with a 
clock unit and a counter unit, the clock pulses being arranged to generate 
logic output in selected pins of the counter unit, the outputs being 
arranged to energise a transistor to illuminate each pair of bulbs. Most 
preferably each output is passed to a buffer transistor and to cause a 
current below about 200 m/A, which is passed to the illuminating 
transistor. The invention further includes, as another aspect, the circuit 
for use in actuating an electrical device. 
The invention includes the light described herein as an accessory to be 
mounted on a vehicle and a vehicle or stand including one or more such 
lights.

The light of FIG. 1 comprises a housing formed of a back cover 1 and a 
front glass-like face 2. Both parts are moulded of plastics and the face 2 
consists of a grid-like surface arranged to defract and refract light. A 
support plate 3 is mounted in the housing and has a central hole 4 to 
receive a 21 watt fog lamp. There are six individual sockets 5 spaced 
about the hole 4 and each is to receive a 5 watt bulb, B1 to B6. Each bulb 
is surrounded by an annular reflective surface 6, generally cup like in 
shape. Behind the support plate 3 is a printed circuit board 7. Two fixing 
screws, not shown, are used to hold the parts in assembly and the light is 
secured to a support, for example, the rear bumper of a car, coach, fire 
engine, ambulance, police car, etc. Wires 8 lead from the printed circuit 
board through the back of the housing 1 to a dashboard, not shown, having 
a switch 9 to actuate either the fog lamp or the hazard light or both. 
The bulbs B1 to B6 are arranged to operate in pairs as shown: B1 and B4; B2 
and B5; B3 and B6. The bulbs are arranged to switch on in the sequence B1 
and B4; B2 and B5; B3 and B6, while the circuit is energised. 
As shown in FIG. 2, the circuit consists of an integratead circuit timer T 
and an integrated circuit counter C co-operating through buffer circuits: 
TR1, TR2 and TR3 to three electronic switches: TR4, TR5 and TR6. 
When the circuit is switched on, the timer T produces clocking pulses at 
pin 3, the frequency of which is determined by the component values of 
resistor R1, capacitor C1 and resistor R2. These clock pulses are fed into 
pin 14 of the counter C. On receiving the first clock impulse, the counter 
produces a logic output on pin 3. On receiving the second clock pulse, the 
logic output disappears on pin 3 and appears on pin 2. On receiving a 
third clock pulse, the logic output disappears on pin 2 and appears on pin 
4. On receiving a fourth clock pulse, logic disappears at pin 4 and 
appears on pin 7 and is fed through capacitor C3 to the reset pin 15 thus 
logic appears on pin 3 starting the sequence again. 
The logic outputs of counter C are connected through resistances R5, R6 and 
R7 to the base of buffer transistors TR1, TR2 and TR3. When a logic 
voltage is applied to one of these buffer transistors, say TR1, TR1 
conducts and a positive voltage appears on TR1 emitter. The current in the 
collector circuit of TR1 is limited to approximately 200 m/A by resistor 
R8. The emitter of TR1 is directly connected to TR4 base, and when a 
current is set up in TR1, TR4 conducts heavily causing lamp 1 and lamp 4 
to light up with the intensity of 10 watts. Because the lamps operate in 
pairs which are switched on and off quickly, they give an illumination 
substantially equal to that of a 21 watt fog lamp. 
D1 is incorporated in the circuit for a dual purpose. The primary purpose 
is to protect the circuit from wrong polarity, and secondly if a 12 volt 
Zener diode is used, the unit is then able to work on a 24 volt system. 
Decoupling is carried out by C5. 
By virtue of the circuit described, the lamps may be energised with little 
current generating little heat, and they will be of long life and will 
give a very bright illumination. 
One or more lights as described may be mounted on the rear bumper of a 
vehicle. In use, when the vehicle is crashed or follows a crashed car the 
driver actuates the switch 9 to operate the light. The drivers of 
following cars will notice the light in sufficient time to stop without 
crashing and causing a multiple pile up. This has been proven in practice 
on several occasions on motorways. 
Although the invention has been described in relation to a car, it may be 
used with sea and air vehicles and also to indicate fixed hazards such as 
in lighthouses, road works, etc. In the latter cases the light may be 
mounted on a fixed stand.