GB2215924A

GB2215924A - Current monitor for vehicle indicator lights

Info

Publication number: GB2215924A
Application number: GB8806325A
Authority: GB
Inventors: David Anthony Ryder
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-03-17
Filing date: 1988-03-17
Publication date: 1989-09-27
Anticipated expiration: 2008-03-17
Also published as: GB8806325D0; GB2215924B

Abstract

A current monitor for monitoring the current supplied to vehicle indicator system by a plug-in flasher unit has a plurality of terminals 19, 20, 21 adapted to be received by respective sockets of a flasher unit support. The monitor also has a plurality of sockets each adapted to receive a respective terminal of the flasher unit. An electronic circuit 13 is connected to one of the sockets for monitoring the current passing through the flasher unit and providing an output signal in the event of the monitored current exceeding a predetermined threshold. The output signal is applied to output terminals 19, 23. The current monitor may be in the form of a simple adapter which can plug directly into a conventional flasher unit support and which itself defines sockets into which a conventional flasher unit can be plugged. When used with a trailer vehicle, the output signal will not appear if the trailer lights fail or become disconnected. <IMAGE>

Description

FLASHER UNIT CURRENT MONITOR The present invention relates to a current monitor for monitoring the current supplied to vehicle indicator system by a plug-in flasher unit.

Vehicles are generally supplied by manufacturers without a tow bar. If a customer wants a vehicle he is purchasing to have a tow bar or to fit a tow bar to an existing vehicle, it is necessary not only to fit the mechanical components of the tow bar assembly to the vehicle but also to extend the wiring of the vehicle to enable the lighting system of a trailer to be plugged into the vehicle lighting system. In particular, it is necessary to provide in the vehicle an indicator which alerts the vehicle driver in the event of failure of any of the indicator lights of the towing vehicle or the trailer.

The conventional approach to monitoring the operation of the indicator lights of.a towing vehicle and a trailer is to simply monitor the magnitude of the current supplied to the indicator lights.

Generally there will be two lights on each side of the towing vehicle, which if they are both operating will draw a predetermined current. When a trailer is connected to the lighting system of a towing vehicle, at least one further indicator light is added to each side of the combined vehicle and accordingly the current drawn by a combination of three lights is greater than the current drawn by two lights only.

This increase in current can be detected by a relatively simple electronic circuit. That circuit in turn can be used to energise a "telltale" indicator light or buzzer mounted inside the towing vehicle compartment. Thus the driver is alerted to the failure of any one of his indicator lights if when he operates his indicators the telltale light or buzzer is not energised.

Conventional flasher units are generally plug-in devices so that they can be easily replaced in the event of their failure. To simplify the conversion of the indicator light circuit of a vehicle when a tow bar is fitted to. that vehicle, it is known to replace a conventional flasher unit with a new flasher unit incorporating a current monitoring circuit and an auxiliary output terminal. A signal appears on the auxiliary output terminal in the event of the current drawn through the flasher unit exceeding a predetermined limit, that limit only being exceeded when the indicator lights of a towing vehicle are connected to the circuit. The auxiliary terminal of the replacement flasher unit is then connected to the telltale light or buzzer on the vehicle dashboard.The replacement of the entire flasher unit does however increase costs significantly, and it is therefore known to leave the existing flasher unit in place and insert a simple current monitoring circuit into the wire which supplies current from the flasher unit to the indicator lights. This does require however a fitter to locate and cut the correct wire coming from the flasher unit, and then to fit in series with that wire the current monitoring circuit, and then to take a further wire from the current monitoring circuit to a telltale light or buzzer. This is a time consuming process given that the fitter is operating in a restricted space occupied by many different wires.

In some cars a telltale light is already present in the car's instrument panel and is connected by a wire to a flasher unit socket intended to receive the auxillary terminal of a replacement flasher unit. If a simple current monitoring circuit is installed rather than a replacement flasher unit the telltale light connecting wire must be located and cut. This is another time consuming process.

It is an object of the present invention to provide a current monitor which can be used to quickly and easily convert a conventional flasher unit for use in a vehicle indicator system to which the indicator lights of a trailer can be connected.

According to the present invention there is provided a current monitor for monitoring the current supplied to a vehicle indicator system by a plug-in flasher unit having a plurality of terminals each of which is adapted to be received by a respective socket of a flasher unit support, the current monitor comprising a plurality of sockets each adapted to receive a respective terminal of the flasher unit, an electronic circuit connected to one of the sockets for monitoring the current passing through the flasher unit and providing an output signal in the event of the monitored current exceeding a predetermined threshold, a plurality of terminals each adapted to be received by a respective socket of the flasher unit support, and an output terminal to which the output signal is applied.

The current monitor may be in the form of a simple adapter which can plug directly into a conventional flasher unit support and which itself defines sockets into which a conventional flasher unit can be plugged. Thus, the fitter simply has to pull out the conventional flasher unit, push in the adapter, connect a telltale light or buzzer to the current monitor output terminal, and then plug the conventional flasher unit back into the adapter.

This is a simple process requiring little skill and effort. Preferably the current monitor output terminal is accessible from both beneath and to one side of the adaptor so that a fitter can make connections to the terminal in the most appropriate manner given the particular circumstances. For example, the current monitor output terminal may comprise a first portion projecting from the underside of the adaptor and a second portion accessible through an opening on one side of the adaptor.

In some circumstances the conventional flasher unit is mounted ifl such a way that there is insufficient space available to place even a thin adapter between it and its conventional flasher unit support or the conventional flasher unit has terminals which are arranged in a non-standard configuration. To provide for such circumstances, the current monitor may comprise extension wires which extend to the current monitor from spacer terminals which are inserted into the flasher unit support and which in turn support the conventional flasher unit. The current monitor can then be placed adjacent the normal site of the flasher unit and it is still not necessary to cut any wires leading from the flasher unit support.

Preferably the current monitor comprises a double terminal for connection to the terminal of the flasher unit through which current is delivered to the indicator circuit. The double terminal may comprise a first terminal into which the flasher unit terminal is inserted, and a second terminal in alignment with that socket in which in use the flasher unit terminal is received in the flasher unit support, the first and second terminals being electrically isolated from each other, and the electronic monitoring circuit being connected between the first and second terminals.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic illustration of a conventional vehicle indicator system incorporating a trailer indicator monitoring circuit; Fig. 2 is a perspective view of a current monitor in accordance with the present invention; Fig. 3 is a perspective view of terminals incorporated in the current monitor of Fig. 2; Fig. 4 is a schematic side view of the components of the current monitor of Fig. 2; Fig. 5 is a circuit diagram of a current monitoring circuit incorporated in the current monitor of Fig. 2; and Fig. 6 is a schematic illustration of extension wires which can be used to connect the current monitor of Fig. 2 to a non-standard flasher unit and flasher unit support.

Referring to Fig. 1 a vehicle battery 1 is connected between an earth terminal and a conventional flasher unit 2. The flasher unit comprises a switch 3 which is normally open. The output of the flasher unit is passed to a current monitor 4 which is responsive to the magnitude of the current flowing therethrough. An indicator control switch 5 is movable between a neutral position as shown and alternate positions in which left hand indicator lights 6 or right hand indicator lights 7 are illuminated. For example, when the indicator control switch is moved upwards from the position shown in Fig. 1 current flows through an electronic flasher control circuit 8 in the flasher unit 2 and the control circuit 8 then closes and opens the switch 3 at an appropriate repetition rate. The lights 7 thus flash on and off.A light 9 is provided which flashes inside the vehicle compartment each time one of the lights 6 or 7 is energised.

A plug and socket arrangement 10 is provided for connecting lights 11 and 12 of a trailer to the vehicle indicator system. Thus the light 11 is energised whenever the lights 6 are energised, and the light 12 is energised whenever the lights 7 are energised. The addition of a third light to each of the left and right hand sets of indicator lights causes the current through current monitor 4 to increase in the event of a trailer lighting circuit being connected through the plug and socket 10. This increase in current is -detected by an electronic current measuring circuit 13 in the current monitor 4 and that circuit 13 in turn energises a telltale light 14 whenever one of the lights 11 or 12 is energised.If any one of the lights 6, 7, 11 or 12 fails the current through the current measuring circuit 13 cannot exceed a threshold set by the circuit 13 and accordingly the telltale light 14 cannot be energised. Thus the vehicle driver is made immediately aware of the failure of any indicator light in the system.

Referring now to Figs. 2 to 5, an embodiment of the present invention will be described. The embodiment comprises a casing defining four sockets 15, 16, 17 and 18 and four terminals 19, 20, 21 and 22. Further terminals 23, 24, 25 and 26 are located immediately inside the sockets 15, 16, 17 and 18 respectively.

The current measuring circuit 13 of Fig. 1 is illustrated in more detail in Fig. 5. The circuit energises the telltale light 14 whenever the current through a series resistor 27 exceeds a predetermined threshold. Energisation of the telltale light 14 is controlled by a transistor 28 which is responsive to the voltage developed across the resistor 27.

The terminals 20, 21 and 22 are positioned in alignment with the conventional terminal position on three terminal flasher units. Thus, the adapter of Fig. 2 can be simply inserted into sockets vacated by conventional three terminal flasher units. The flasher unit in turn can be plugged into the sockets 16, 17 and 18. The terminals 21 and 25 are isolated from each other by an insulat ing block 29 arranged between extension terminals 30, 31. An output 32 of the current monitoring circuit of Fig. 5 is connected to the terminal 23. The signal on terminal 23 can be picked up either from terminal 19 to which it is connected or from terminal 23.Thus, depending on the particular arrangement of the flasher unit being considered, either a female terminal socket can be pushed on terminal 19, or a female terminal socket can be pushed into the socket 15 to engage the terminal 23. If the structure of the flasher unit support is such that the terminal 19 would prevent insertion of the adapter into the flasher unit support that terminal can simply be removed by the fitter.

The arrangement of the various terminals and sockets in the adapter shown in Fig. 2 is such that it can be used with a particular standard arrangement of flasher unit terminals. Fitters will occasionally come across non-standard flasher units and flasher unit supports and in those circumstances it would be useful if the same adapter could nevertheless be used to make the necessary connections. An arrangement of extension wires is illustrated in Fig. 6 which enables the use of the adapter of Fig. 2 in such circumstances. The arrangement illustrated in Fig. 6 can also be used where there is insufficient available height to fit the adapter between the conventional flasher unit and its support.

Referring to Fig. 6, simple extension terminals 33 and 34 are used to extend the positive supply and earth connections to the flashing unit 35. The output terminal 36 of the flasher unit is received in a first terminal 37 defined by a double terminal, the other half 38 of the double terminal being received in the socket of a flasher unit support 39, into which the terminal 36 is normally inserted. A flying lead 40 is connected to the terminal 37 and is inserted into the socket 17 (not visible in Fig.6) and the flying lead 41 connected to the terminal 39 is connected to the terminal 21. The operation of the resultant circuit is thus exactly the same as in the case of the arrangement described as reference to Fig.2 to 5.

In both of the illustrated embodiments of the invention the conventional flasher unit has three terminals, that is a first terminal carrying the battery voltage, a second terminal connected to earth, and a third terminal providing the output to the indicator system. The present invention is equally applicable however to flasher unit having two or four or more terminals, the crucial feature being the interposition of a current monitoring circuit in series with the flasher unit output terminal.

Claims

1. A current monitor for monitoring the current supplied to a vehicle indicator system by a plug-in flasher unit having a plurality of terminals each of which is adapted to be received by a respective socket of a flasher unit support, the current monitor comprising a plurality of sockets each adapted to receive a respective terminal of the flasher unit, an electronic circuit connected to one of the sockets for monitoring the current passing through the flasher unit and providing an output signal in the event of the monitored current exceeding â predetermined threshold, a plurality of terminals each adapted to be received by a respective socket of the flasher unit support, and an output terminal to which the output signal is applied.

2. A current monitor according to claim 1, comprising an adaptor which can plug directly into a conventional flasher unit support and which itself defines sockets into which a conventional flasher unit can be plugged

3. A current monitor according to claim 1 or 2, wherein the current monitor output terminal is accessible from both beneath and to one side of the adaptor.

4. A current monitor according to claim 3, wherein the current monitor output terminal comprises a first portion projecting from the underside of the adaptor and a second portion accessible through an opening on one side of the adaptor.

5. A current monitor according to any preceding claim, comprising extension wires which extend to the current monitor from spacer terminals which may be inserted into a flasher unit support and which in turn may support a conventional flasher unit.

6. A current monitor according to any preceding claim, comprising a double terminal for connection to the terminal of the flasher unit through which current is delivered to the indicator system, the double terminal comprising a first terminal into which the flasher unit terminal is inserted, and a second terminal in alignment with that socket in which in use the flasher unit terminal is received in the flasher unit support, the first and second terminals being electrically isolated from each other, and the electronic monitoring circuit being connected between the first and second terminals.

7. A current monitor substantially as hereinbefore described with reference to the accompanying drawings.