GB2054290A

GB2054290A - Vehicle trailer lighting system

Info

Publication number: GB2054290A
Application number: GB7923963A
Authority: GB
Original assignee: CURREY B
Current assignee: CURREY B
Priority date: 1979-07-10
Filing date: 1979-07-10
Publication date: 1981-02-11
Also published as: GB2054290B

Abstract

A lighting system for a motor vehicle trailer has a number of photo transistors (30) each disposed in a respective one of attachment devices (12) in the vicinity of one of the tail, stop and indicator lights (22, 23, 24, 25) at the rear of a motor vehicle. Each photo transistor (30) is connected by way of a plug and socket arrangement (15) to a corresponding electronic switching circuit (17, 31-40) so as to control one or more corresponding lights (26, 27, 28, 29) on the tailboard (21) of the trailer. <IMAGE>

Description

SPECIFICATION Trailer Lighting System The invention relates to a lighting system for trailers of motor vehicles.

Motor vehicle trailers such as simple loadcarrying trailers, boat trailers, horse boxes, camping trailers are towed behind the motor vehicle and attached to the vehicle by means of a tow ball connection attached to a tow bar of the vehicle. It is necessary for there to be some form of electrical connection between the motor vehicle and the trailer such that operation of the rear vehicle lights (side lights, stop lights, indicator lights) is repeated by corresponding lights at the rear of the trailer.

Normally an electric socket is attached to the motor vehicle tow-bar and appropriate electrical connections are made to the socket terminals from the vehicle. An electrical plug on the trailer engages the socket and electrical connections are carried to the trailer rear lights by means of a cable from the plug.

One disadvantage of the known arrangement is the comparative complexity of the electrical connections required since it is necessary to take connections between the socket and wiring within the motor vehicle. This is often outside the scope of the ordinary motorist so that an auto-electrician is employed with the attendant expense. A further disadvantage is that the operation of two pairs of indicator lights increases the indicator light flash rate so that it may be necessary, for example, to comply with legal requirements, to fit a replacement flasher unit.

An aim of the present invention is to provide a trailer lighting system which eliminates the need for a complex electrical connection to be made by the motorist between the motor vehicle and the trailer. A further aim is to provide a system which allows greater versatility and permits, if necessary or desirable, the use of an electrical supply independent of the motor vehicle battery.

According to the present invention there is provided a lighting system for a motor vehicle trailer comprising an opto-electric transducer operative in response to reception of light from an associated rear light member of the motor vehicle to provide a switching signal, and a switching device operative in response to said switching signal to actuate one or more corresponding lighting members for the rear of the trailer.

Preferably at least four transducers are provided, one for each vehicle indicator lamp and one each for a stop lamp and a side lamp of the vehicle respectively, each transducer being provided with a respective one of switching devices. In this case normally the switching devices associated with the vehicle side lamp and stop lamp actuate corresponding respective pairs of side lamps and stop lamps for the rear of the trailer.

The or each opto-electric transducer may comprise a photo transistor and the or each switching device may comprise a switching transistor.

The invention will hereinafter be further described by way of example with reference to the accompanying drawings in which: Figure 1 is a schematic diagram showing a rear tail light assembly on a motor vehicle and connections, by means of a system in accordance with the present invention, with a trailer rear light assembly; Figure 2 is a circuit diagram of part of the lighting system of Fig. 1; Figure 3 is a circuit diagram of an alternative embodiment of a lighting system in accordance with the present invention; and Figure 4 is a cross-sectional diagram showing one arrangement for connecting a photo transistor to a vehicle rear lamp assembly.

Referring firstly to Fig. 1, two vehicle rear light clusters are indicated by numerals 10 and 11. Photo transistors are attached to the light clusters by means of fixing devices 1 2 and are connected through a cable 1 3 to a socket 14 fixed to the rear of the vehicle.

Electrical connections from the photo transistors are taken, by way of a plug 1 5 complementary to socket 14, and by way of a cable 1 6 to respective switching circuits represented as a whole by block 1 7. Of course the plug and socket arrangement 14, 1 5 is not essen tial since a disconnection could be made at the rear light clusters as will be made clear hereinafter with reference to Fig. 4. Connections from the respective switching circuits are taken by way of a cable 1 8 to appropriate lamps of lighting clusters 1 9 and 20 of a tailboard 21 of a trailer (not shown).In the arrangement of Fig. 1 the fixing devices 1 2 (with corresponding photo transistors) are attached one to an indicator light 22, one to a stop light 23, and one to a side light 24 of cluster 1 0. A single fixing device 1 2 is attached to the indicator light 25 of cluster 11.

Thus the single brake or stop light 23 serves to actuate a pair of stop lights 26 on the tailboard 21, a single side light 24 serves to actuate a pair of side lights 27 on the tailboard whilst indicator lights 22 and 25 serve to actuate indicator lights 28 and 29 respectively on the tailboard 21. Although use of single lights 23 and 24 to actuate corresponding pairs of lights on tailboard 21 simplifies the arrangement there is a disadvantage in that the failure of one of such- vehicle lights 23 or 24 makes both corresponding lights on the tailboard 21 of the trailer inoperational. It may therefore be desirable in the interest of safety to provide each of the vehicle lights on both clusters with a fixing device 1 2 and photo transistor, each vehicle light being then operative to control a corresponding one of the lights on the trailer tailboard.

In Fig. 2 there is illustrated one switching circuit of the arrangement of Fig. 1. A photo transistor 30 is connected between positive and negative rails 31 and 32 respectively. A current limiting resistor 33 is connected between line 31 and the collector of photo transistor 30 and a connection is made between the collector of photo transistor 30, by way of a resistor 34, to the base of an NPN transistor 35. A base bias resistor 36 ensures that transistor 35 conducts current between rails 31 and 32 through a resistor 37 as long as photo transistor 30 is not conducting.

Transistor 35 serves to control an NPN switching transistor 38 which in turn controls current flow through, in this example, trailer stop lights 26 connected in parallel with one another. A base current limiting resistor 39 is connected between transistors 35 and 38 whilst a bias resistor 40 is connected between the emitter and base of transistor 38. The power supply for the circuit of Fig. 2 may be derived from the vehicle or may be from a separate battery in the trailer. It will be understood that four circuits similar to that of Fig. 2 are employed in the system of Fig. 1 and in general one such switching circuit is provided for each photo-transistor employed.

Fig. 3 illustrates one alternative switching circuit in which, in contrast to the arrangement of Fig. 2, the power supply for the trailer lamps is isolated from the power supply for the switching transistors. In this case a relay 41 is used to switch power to parallel connected lamps 26. Current through a coil 42 of the relay is controiled by a switching transistor 43 which is in turn controlled by photo transistor 30. A diode 44 is connected across coil 42 to eliminate the effects of selfinduced emf ("kickback" voltage) at switchoff. The coil 42 serves to actuate contacts 45 of the relay 41.

Fig. 4 illustrates in detail and in partial cross-section one arrangement by which a photo transistor 30 may be attached in close proximity to one of the vehicle rear lights. A tubular plastics base position 46 is fixed to rear light 23 for example by adhesive and has an external screw-threaded portion 47. A tubular cap 48 is adapted for screw-thread engagement with base portion 46 and has an internal screw-thread 49 corresponding to the thread 47 of the base portion 46. A holder 50 for the photo transistor 30 has an annular portion 51, which engages behind an annular flange 52 of the cap 48. Connections are taken off by way of a cable 53 and a short protective sleeve 54 extends between cable 53 and holder 50. It will be clear that by screwing cap 48 onto base portion 46 the photo transistor 30 is placed in the desired position relative to lamp 23.Other arrangements for attachment of the phototransistor to one of the rearlights are also, of course, possible. For example instead of a screw thread attachment between cap 48 and base 46 a bayonet fitting could be employed which wouid have the advantage of more rapid fitting and disengagement.

The operation of the switching system will now be described. Assuming connections have been made, as illustrated in Fig. 1, between the various rear lights of the vehicle (including, though not illustrated, the number plate light) and corresponding switching circuits then the illumination of one such rear light will actuate the corresponding photo transistor 30. Thus, in the circuit of Fig. 2 the.illumina- tion of rear light 23 causes photo transistor 30 to conduct so that the voltage at the base of transistor 35 is reduced towards zero and transistor 35 ceases to conduct. The voltage at the base of switching transistor 38 consequently rises and transistor 38 conducts so that lamps 26 on tailboard 21 are illuminated.

In the arrangement of Fig. 3 illumination of photo transistor 30 results in the injection of base current into switching transistor 43 which thus conducts current through relay coil 42 to actuate and close relay contacts 45 thus connecting the battery supply to parallel connected lamps 26.

The system allows for simple set-up by any person almost irrespective of electrical knowledge. Furthermore it will be seen that the indicator flash rate will be unaffected by the arrangement since the tailboard indicators merely reproduce, by way of the switching devices, the flashing of the vehicle indicator lights.

Of course the invention is not limited to the arrangements described above. For example other opto-electric transducers could be used instead of photo-transistors. It is not essential for the opto electric transducer to be mounted on the vehicle rear light assembly and if required light could easily be conducted by fibre optic to the photo transducers which might be conveniently located within a circuit box. Furthermore, the optical information could be taken from behind the vehicle tail light assembly thereby avoiding any alteration in the external appearance of the vehicle tail light assemblies.

Claims

1. A lighting system for a motor vehicle trailer comprising an opto-electric transducer operative in response to reception of light from an associated rear light member of the motor vehicle to provide a switching signal, and a switching device operative in response to said switching signal to actuate one or more corresponding lighting members for the rear of the trailer.

2. A lighting system as claimed in claim 1 in which a plurality of opto-electric transducers are provided, each transducer being, in use, disposed for reception of light from a respective one of rear light members of the motor vehicle, and each transducer being operative to provide a switching signal for the actuation of a corresponding one of switching devices of the system.

3. A lighting system as claimed in claim 1 or 2 in which the or each transducer is a photo transistor.

4. A lighting system as claimed in any preceding claim in which the or each switching device comprises a switching transistor controllable between conducting and non-conducting states by that opto-electric transducer associated therewith, thereby to permit or discontinue current flow through the or each corresponding lighting member for the rear of the trailer.

5. A lighting system as claimed in Claim 4 in which the or each switching transistor is connected in series with a respective coil of a relay such that when the switching transistor is placed in a contacting state current flows through said coil to actuate contacts of the relay to allow current flow through the or each corresponding trailer lighting member.

Claim 6 is deleted, and Claims 7 and 8 are renumbered 6 and 7 respectively.

5. A lighting system as claimed in claim 4 in which the switching transistor is connected in series with a coil of a relay such that when the switching transistor is placed in a contacting state current flows through said coil to actuate contacts of the relay to allow current flow through the or each corresponding trailer lighting member.

6. A lighting system as claimed in any preceding claim in which each opto-electric transducer is provided with a fixing device whereby the transducer may be held in close proximity to the associated rear light member of the motor vehicle.

7. A lighting system for a motor vehicle trailer substantially as hereinbefore described with reference to and as illustrated in Figs. 1, 2 and 4 of the accompanying drawings.

8. A lighting system for a motor vehicle trailer substantially as hereinbefore described with reference to and as illustrated on Figs. 1, 3 and 4 of the accompanying drawing.

CLAIMS (21 Apr 1980)

1. A lighting system, for a motor vehicle trailer, comprising an opto-electric transducer, a fixing device whereby the transducer may be mounted in close proximity to an associated rear light member of a motor vehicle and in which the transducer is operative in response to reception of light from the aid associated rear light member to provide a switching signal, and a switching device operative in response to said switching signal to activate one or more corresponding lighting members for the rear of a trailer.

2. A lighting system as claimed in claim 1 in which a plurality of opto-electric transducers are provided, each transducer having its respective said fixing device enabling it to be mounted for reception of light from a respective one of rear light members of the motor vehicle, and each transducer being operative to provide a switching signal for the actuation of a corresponding one of switching devices of the lighting system.