Electric lamp and discharge devices: systems – Special application – Vehicle
Reexamination Certificate
1999-05-07
2001-05-15
Vu, David (Department: 2821)
Electric lamp and discharge devices: systems
Special application
Vehicle
C315S077000, C340S468000, C307S010100
Reexamination Certificate
active
06232722
ABSTRACT:
TECHNICAL FIELD
This invention relates to an adapter to be installed between a towing vehicle tail light system and a trailer tail light system.
BACKGROUND OF THE INVENTION
It is necessary to control the lighting system of a trailer in response to the lighting system of a towing vehicle. Devices for interfacing the lighting systems of towing vehicles and their respective trailers are well known. Most trailer lighting systems have combined the turn and brake signals in a single lamp with a single filament. Most modern day towing vehicles have separate turn signal and brake lamps. Thus, some kind of adapter circuitry is needed in order to interface the two systems, which would otherwise be incompatible.
Many devices known in the art accomplish this interface by using some kind of logic and switching circuitry. In essence the trailer lighting system is wired in parallel to the vehicle lighting system. Such a system uses the same power signal to illuminate both the trailer lamps and the towing vehicle lamps. To ensure that the signal, which reaches the trailer lamps, will be sufficient to adequately illuminate them, the original power signal through the vehicle lamps must have an increased amount of current. There are many disadvantages to such a system. For example, the flashers on the towing vehicle must be replaced with heavy-duty flashers to endure the increased current through them.
Devices have been developed that illuminate the vehicle and trailer lamps with separate power signals. This can be accomplished through the use of solid state switching devices, such as transistors, relay coils, or other types of signal detection devices. However, the known devices have many disadvantages. For example, they are susceptible to short circuit conditions, or are unable to disable a trailer lamp when both the brakes and a turn signal are engaged.
SUMMARY OF THE INVENTION
In accordance with one aspect of the invention, an electrical adapter apparatus interfaces the electrical circuitry of a towing vehicle lighting system with the electrical circuitry of a trailer lighting system. The electrical adapter apparatus includes a plurality of vehicle signal inputs. The vehicle signal inputs are capable of receiving electrical signals from the towing vehicle lighting system, such as taillights, stop lights and turn signal lights. A power supply input is connectable to a power supply. The adapter has a circuit with a plurality of three terminal transistors. Each of the three terminal transistors has a first transistor terminal being coupled to one of said vehicle signal inputs, a second transistor terminal being electrically grounded and a third transistor terminal being connected to the power supply input. Preferably the plurality of three terminal transistors includes a first transistor having its first terminal connection to a brake signal input. A second transistor has its first terminal connected to a right turn signal input. A third transistor has its first terminal connected to the brake input. A fourth transistor has its first terminal connected to a left turn signal input.
The adapter circuit also has a plurality of two-direction relays. Each of the two direction relays has two terminals. Each of said two direction relay terminals is connected to a respective third transistor terminal and the power input through separate resistive paths.
Preferably the plurality of two direction relays includes a first and second direction relay. The first relay has a first terminal connected to the third terminal of the first transistor and its second terminal connected to the third terminal of the second transistor. The second relay has its first terminal connected to the third terminal of the third transistor and its second terminal connected to the third terminal of the fourth transistor.
Each tvo-direction relay is associated with a relay contact. Each relay contact is openable and closeable to be selectively connected to said power supply input to a plurality of trailer signal outputs. The plurality of relay contacts preferably includes a first and second contact with respective first terminals operably connectable to the power supply input and respective second terminals connected to respective right and left stop turn lamp outputs to the trailer.
In one embodiment the electrical adapter apparatus includes a third vehicle signal input with an additional transistor having its first terminal connected to said third vehicle signal input its second terminal connected to ground and its third terminal connected to a first terminal end of an additional relay. The additional relay has its second terminal connected to the power supply input.
An additional relay contact is operably connected to the relay with its first terminal connected to the power supply input and said second tenninal to an additional trailer signal output such as the trailer tail light.
The present invention is an improved adapter circuitry for interfacing a towing vehicle and a trailer lighting system, which have a different number of lamps. This adapter circuitry illuminates the vehicle and trailer lamps with separate power sources. This provides sufficient current to the trailer lamps without requiring an increased current through the vehicle lamps. In addition, driving the two lighting systems with a separate power source keeps the lighting systems isolated from each other, thereby reducing the possibilities of a short circuit. Also, the present invention utilizes solid state switching devices and relay circuits to account for trailer lamps, which share brake and turn signals. When both the vehicle brake and turn signals are engaged, the trailer lamp flashes 180° out of phase with the respective vehicle lamp, instead of being overridden by just the brake signal. The current invention solves the problem of interfacing non-compatible lighting systems, while improving the trailer lamp output current, reducing the system's vulnerability to short circuit conditions, and accounting for the trailer's shared brake and turn lamps.
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Bryant Richard C.
Johnson Richard
Alemu Ephrem
Draw-Tite, Inc. (by Richard Johnson)
Reising, Ethington, Barnes, Kisselle, Learman & McCulloch, P.C
Vu David
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