Note: Descriptions are shown in the official language in which they were submitted.
CA 02297884 2000-02-03
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DAYTIME RUNNING LIGHT CIRCUIT
TECHNICAL FIELD OF THE INVENTION
This invention relates to daytime running lights for a vehicle, particularly a
truck.
CA 02297884 2000-02-03
BACKGROUND OF THE INVENTION
A recent safety trend for vehicles, such as automobiles and trucks, has been
to provide daytime running lights. Many automobiles provide reduced power to
light headlights during the day, for example. Such daylight running lights
makes it
much easier for on-coming traffic to see a vehicle, particularly in hazy
conditions.
While daylight running lights are desirable, they have added additional
circuitry to the vehicle, increasing cost and complexity. A need exist for an
inexpensive, yet reliable system for providing daytime running lights.
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CA 02297884 2000-02-03
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, a device is provided for
operating a light on a vehicle during daylight. The device includes a first
circuit to
provide power to the light during daylight and a second circuit to provide
power to
the light at predetermined intervals. A switching device is provided to
disconnect
the first circuit from the light and connect the second circuit to the light.
In
accordance with another aspect of the present invention, the light is a turn
signal
lamp. In accordance with another aspect of the present invention, the
switching
device includes a relay having contacts moving between a first position to
connect
the first circuit to the light and a second position to connect the second
circuit to
the light. In accordance with another aspect of the present invention, the
second
circuit is a turn signal circuit in the vehicle. A hold device can be used to
maintain
the switching device connecting the second circuit to the lamp.
In accordance with another aspect of the present invention, a method is
provided for utilizing the turn signal on a vehicle for use as a daytime
running light.
The method includes the step of providing power to the turn signal
continuously
during daylight by maintaining a switching device in a first position and
providing
power to a solenoid in the switching device when the turn signal is activated
to
move the switching device to a second position connecting the turn signal to
the
turn signal circuit in the vehicle. The method further includes the step of
holding
the switching device in the second position during operation of the turn
signal
circuit.
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CA 02297884 2000-02-03
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention and its advantages will be
apparent from the following Detailed Description when taken in conjunction
with
the accompanying drawings, in which:
FIGURE 1 is a perspective view of a circuit board in a vehicle, including a
daytime running light circuit, comprising part of a circuit forming a first
embodiment of the present invention; and
FIGURE 2 is a schematic of the first embodiment.
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CA 02297884 2000-02-03
DETAILED DESCRIPTION
With reference now to the figures, there will be described a daytime running
light circuit 10 which forms a first embodiment of the present invention. The
circuit
is mounted within a vehicle 12, preferably a truck, and utilizes the left turn
signal
S 14 and right turn signal 16 of the vehicle to provide both daytime running
lights and
conventional turn signal operation. With reference to FIG. 2, the operation of
the
circuit will be described. The left turn signal 14 has a lamp 18 and the right
turn
signal 16 has a lamp 20. The lamp 18 is mounted in a socket 22 which grounds
one
end of the lamp filament or contact to a ground line 24 and connects the other
end
10 of the filament or second contact to a line 26. Line 26 extends to a
contact in a
switching relay 28. The contact on relay 28 shifts between a first position
connecting the line 26 to a line 30 and a second position, connecting the line
26 to a
line 32, depending upon whether current is flowing through the solenoid 34 in
the
relay with sufficient energy to close the relay. When power is not provided to
solenoid 34, the contact will connect lines 26 and 30. Only when sufficient
current
flows through the solenoid 34 will the contact disconnect the line 30 from
line 26
and connect line 26 to line 32.
Line 30 extends to a disable relay 36. Disable relay 36 has a contact which,
in a first position, connects power line 38 to the line 30 and, in a second
position,
disconnects power line 38 from line 30 and connects power line 38 to a non-
connected terminal 40. The normal position of disable relay 36 will be the
first
position connecting power line 38 to line 30 unless sufficient current is
flowing
through the solenoid 42 of the disable relay 36 to move the contact to the
second
position. Power line 38 is connected through a fuse 44 to a vehicle ignition
controlled battery voltage point. In a typical vehicle, this will be + 12
volts DC.
As can be understood, with the switching relay 28 and disable relay 36
unactuated, a positive voltage is provided through line 38 to line 30 to line
26 to
light the lamp 18 in the left turn signal 14. This would be normal operation
during
daylight hours to provide daylight running lights. The right turn signal 16
has
similar circuit connections to line 30 through a switching relay 46 having a
solenoid
48 to light the lamp 20 during daylight hours as well.
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CA 02297884 2000-02-03
Daytime running lights will be only used during daylight. Therefore, a
circuit is provided to disable the daytime running lights during darkness,
when the
headlights of the vehicle will typically be turned on. This is achieved by
connecting
the solenoid 42 of the disable relay 36 to power line 38 and through the
headlight
switch 50 to ground. When the headlight switch is turned on, typically at dusk
or
during the night, a circuit path will be closed to provide current flow
through the
solenoid 42 to actuate the disable relay 36 and remove power to the left and
right
turn signals through line 30. Diode 52 provides isolation from the park brake
switch 54 for other circuits connected to the headlight switch 50 and prevents
noise
from other electrical circuits affecting the disable relay 36.
Similarly, it is common to deactivate the daytime running lights when the
parking brake is set. The parking brake is usually set only when the vehicle
is
stopped. A switch 54 forming part of a parking brake will also provide a
mechanism for current flow through the solenoid 42 to activate the disable
relay 36
to disconnect the daytime running lights. Diode 56 provides isolation from the
headlight switch 50 for other external circuits connected to the park brake
switch
54 and also protection from noise in the same manner as diode 52.
During vehicle operation, whether during daylight or at night, the left and
right turn signals 14 and 16 can be operated in the conventional manner, as
will be
described. A conventional turn signal switch (not shown) is provided which
includes a cab mounted turn signal switch for operator selection of left or
right turn
signal operation, and a flasher unit which alternately provides power to the
selected
turn signal and removes the power from the turn signal at a predetermined
frequency to provide the necessary turn signal flashing sequence.
When the vehicle operator selects the left turn signal, the output from the
flasher is provided to points 32 and 60. The initial power provided from the
output
of the turn signal flasher when the turn signal is initially activated flows
through
diode 62 into line 64. It immediately begins to charge a capacitor 66 while
providing current flow through a solenoid 68 in a holding relay 70. After the
capacitor 66 has been charged slightly, current flow through the solenoid 68
will be
adequate to move the contact 72 in the relay 70 from the position shown in
FIG. 2
which disconnects line 74, to a second position, connecting line 74 to line
76. Line
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CA 02297884 2000-02-03
74 can be seen to be connected to the vehicle battery through a circuit
protection
device, such as a polymeric positive temperature co-ei~cient circuit
protection
device 78 of the type sold by Raychem Corporation of Menlo Park, California as
the Models RGE and RLJE PolySwitch.
When line 74 is connected to line 76 by the contact 72, battery voltage is
provided to solenoid 34 of switching relay 28. The other side of the solenoid
34 is
connected to ground through line 80. This current flow will cause the contact
82 of
the switching relay 28 to move to the second position, connecting line 26 to
point
32, representing the output of the turn signal flasher unit. The flasher unit
provides
power in intermittent fashion, determined by the cycle rate of the flasher
unit, to
flash the left turn signal 14. In the intervals during the flashing sequence
in which
power is not provided to the turn signal 14, charge stored in the capacitor 66
will be
sufficient to maintain current flow through the solenoid 68 to hold the
contact 72
connecting lines 74 and 76. Only when the operator switches off the left turn
signal
switch in the cab will there no longer be intermittent power provided at
points 32
and 60, and the capacitor 66. While capacitor 66 maintains sufficient energy
to
activate the solenoid 68 for a short interval, it will soon lose significant
charge,
causing the solenoid 68 to release the contact 72 to the position shown in
FIG. 2.
Diode 62 prevents capacitor 66 from discharging through the flasher circuit
and
turn signal lamps. It will be noted that the turn signal action occurs whether
the
daytime running light circuits are on or not.
The right turn signal 16 is similarly actuated by providing output from the
flasher unit to points 84 and 86. Point 86 connects to diode 88, line 90,
capacitor
92 and solenoid 94 of a holding relay 96. Relay 96 provides power to the
switching
relay 46 through line 98 when the right turn signal is activated in the same
manner
as described previously with the left turn signal. Diode 88 prevents capacitor
92
from discharging through the flasher circuit and turn signal lamps.
It can be seen from the description above that a running light circuit has
been provided which utilizes the turn signals already on the vehicle. The
daytime
running light circuit does not interfere with the normal operation of the turn
signals.
This is achieved by the addition of very few additional and inexpensive
elements,
such as relays, diodes and capacitors. Of course, during daylight operation,
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CA 02297884 2000-02-03
selection of one turn signal for normal turn signal operation does not elect
the non-
selected turn signal and the non-selected turn signal lamp continues to be lit
by the
daytime running circuit independent of the turn signal operation of the
selected turn
signal. A key to making the circuit practical is selecting the holding relays
70 and
96 to have a low current draw and drop-out voltage.
Although a single embodiment of the present invention has been illustrated
in the accompanying drawings and described in the foregoing detailed
description, it
will be understood that the invention is not limited to the embodiment
disclosed, but
is capable of numerous rearrangements, modifications and substitutions of
parts and
elements without departing from the scope and spirit of the invention.
