ROAD VEHICLE LIGHTING SYSTEMS
First Claim
1. A road vehicle lighting system comprising in combination first and second dipped beam headlamps, a main beam headlamp, a dip switch having a first position in which it energizes the dipped beam headlamps, and a second position in which it energizes the main beam headlamp, a light projector for projecting forwardly a well defined, divergent beam of light of generally rectangular cross-section, circuit means coupling said light projector to said dip switch whereby said light projector is energized in both positions of the dip switch, a light receiver for receiving light from a light source in front of the road vehicle, a winding which when energized movesa pair of shutters, one of the shutters serving to cut off said divergent beam of light progressively, and the other of said shutters serving progressively to block light from said light source in front of the road vehicle from entering said light receiver, said light receiver incorporating a photo-cell on which light from said light source falls under the control of said other shutter, a bridge network having an output coupled to said winding, said photo-cell serving to determine the resistance of one limb of said bridge network whereby to determine the position of said shutters, so that said one shutter cuts off sufficient of the projected beam to ensure that said beam does not fall on said light source, the system further including circuit means which is energized under the control of said dip switch at the same time as said main beam headlamp for increasing the minimum strength of the signal which must fall on said photo-cell to energize the winding and thereby move said shutters, whereby said receiver is less sensitive to oncoming light when the dip switch is in its second position than when the dip switch is in its first position.
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Accused Products
Abstract
A road vehicle lighting system has first and second dipped beam headlamps, one main beam headlamp and a projector receiver unit which replaces the second main beam headlamp. The unit projects a divergent beam of light, and cuts off sufficient of that beam to prevent dazzling an oncoming driver. The normal dip switch is employed but is arranged to energize the projector-receiver unit in both positions of the dip switch, and when the dip switch is in its second position the minimum strength of the signal required by the receiver to operate the projector receiver unit is increased.
1 Citation
2 Claims
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1. A road vehicle lighting system comprising in combination first and second dipped beam headlamps, a main beam headlamp, a dip switch having a first position in which it energizes the dipped beam headlamps, and a second position in which it energizes the main beam headlamp, a light projector for projecting forwardly a well defined, divergent beam of light of generally rectangular cross-section, circuit means coupling said light projector to said dip switch whereby said light projector is energized in both positions of the dip switch, a light receiver for receiving light from a light source in front of the road vehicle, a winding which when energized movesa pair of shutters, one of the shutters serving to cut off said divergent beam of light progressively, and the other of said shutters serving progressively to block light from said light source in front of the road vehicle from entering said light receiver, said light receiver incorporating a photo-cell on which light from said light source falls under the control of said other shutter, a bridge network having an output coupled to said winding, said photo-cell serving to determine the resistance of one limb of said bridge network whereby to determine the position of said shutters, so that said one shutter cuts off sufficient of the projected beam to ensure that said beam does not fall on said light source, the system further including circuit means which is energized under the control of said dip switch at the same time as said main beam headlamp for increasing the minimum strength of the signal which must fall on said photo-cell to energize the winding and thereby move said shutters, whereby said receiver is less sensitive to oncoming light when the dip switch is in its second position than when the dip switch is in its first position.
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2. A system as claimed in claim 1 in which the circuit means operable at the same time as the main beam headlamp is energized comprises a circuit connection across one element of the bridge network, said circuit connection including the main beam headlamp, so that when the main beam headlamp is illuminated, the setting of the bridge network is altered.
Specification