GB1572673A

GB1572673A - Flashing light control unit

Info

Publication number: GB1572673A
Application number: GB2743077A
Authority: GB
Original assignee: Klaxon SA
Current assignee: Klaxon SA
Priority date: 1976-07-08
Filing date: 1977-06-30
Publication date: 1980-07-30
Also published as: DE2730444C3; FR2357404B1; FR2357404A1; DE2730444B2; IT1081524B; DE2730444A1

Description

(54) FLASHING LIGHT CONTROL UNIT (71) We, KLAXON S.A., a French Body Corporate, of 39 Avenue Marceau, Courbevoie, France do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a flashing light control unit for direction indicator lamps for motor vehicles.

Numerous types of flashing light control units are known, and it has recently been stated that it would be desirable for them to be controlled by an electronic circuit enabling them to be manufactured in large quantities and with satisfactorily reproducible operating characteristics. Furthermore, it is desirable to design these flashing light control units without difficulty in such a way that the breakdown of one of the indicator. lamps can be detected. preferably by an increase in the flashing frequency.

According to the invention we provide a flashing light control unit for indicator lamps of motor vehicles comprising a capacitor of which one plate is connected to the positive terminal of a d.c. source while the other plate is connected to the base of a first transistor via a first resistor, said base being connected to the positive terminal via a second and a third resistor in series. the collector of the said first transistor being connected to the positive terminal via a fourth resistor and to the base of a second transistor having its emitter connected to the emitter of the first transistor, and its collector-emitter circuit series connected with a fifth resistor and a relay coil, the contact of the said relay being interposed between the positive terminal and a point situated between the second and third resistor, the said point being connected to a manual selector switch for the indicator lamps.

In one version of the invention the said fifth resistor is mounted between the collector of the said second transistor and the positive terminal of the supply source, while the said relay coil is mounted between the common point of the emitters of the two transistors and the negative terminal of the supply source.

In an alternative version the said fifth resistor is mounted between the common point of the emitters of the two transistors and the negative terminal of the supply source, while the said coil is mounted between the collector of the second transistor and the positive terminal of the supply source.

With the device to which the invention relates the indicator lamps are on during the discharge of the capacitor, this latter being charged when the control centre is in the idle state. The lamps are caused to come on and go off in alternation by the voltage surges occurring at the common point of the emitters of the two transistors.

The invention will be clearly understood from a study of the following description by reference to the accompanying drawing, in which: Figure 1 is a circuit diagram of a flashing light control unit according to one version of the invention.

Figure 2 is a diagram of part of the device shown in Figure 1, with regard to an alternative version, and Figure 3 shows the voltage variations occurring over a period of time at point A in the circuit shown in Figure 1. both in the case of normal operation and in the event of the breakdown of a lamp.

The control unit shown in Figure 1 is intended for the control of two groups of two indicator lamps, L1 and L2 respectively. controlled by a manual switch C. A pilot lamp P is mounted in parallel on the two groups L1 and L2.

The control unit comprises a capacitor C1 of which one plate is connected to the positive terminal of the supply source and the other to a resistor R1. The resistor R1 is also connected to the positive terminal via two resistors R2 and R3 in series and to the base of a transistor T1 of which the collector is connected to the positive terminal via a resistor R4.

This collector of the transistor T1 is likewise connected to the base of a second transistor T2. The point M between the resistors R2 and R3 is connected to the common point c of the switch C.

In the version described the collector of the transistor T2 is connected to the positive terminal via a resistor R5 and the emitters of the transistors T1 and T2 are connected to a point E which in its turn is connected to one end of the coil of a voltage relay R11, the other end of the said coil being connected to the negative terminal of the supply source. The contact ml of the relay R11 is interposed between one end of the coil of a current relay R12, of which the other end is connected to the positive terminal, and the point M between the resistors R2 and R3. The contact m2 of the relay R12 is connected both to the positive terminal and to the collector of the transistor T2 via a resistor R6.

In an alternative version (not shown in the drawing) the resistor R5 is mounted between the point E and the negative terminal of the supply source while the coil of the relay R11 is mounted between the collector of the transistor T2 and the positive terminal of the supply source.

The device shown functions as follows: When the system is at rest, the switch C not having been thrown, the transistor T1 is rendered conductive by the resistors R2 and R3 and the capacitor C1 charges up via the resistor R1, the base-emitter junction of the transistor T1 and the coil of the relay R11. The potential at the point F Eo (Figure 3), is fixed by the resistor R4 and the relay R11 and is insufficient to energize the relay R11. The collector-emitter saturation voltage of the transistor T1, which is low during the conduction, blocks the transistor T2, so that the relay R11 is not fed and its movable contact ml remains open against the stop rl.

When the switch C on one of the groups of lamps L1 or L2 is actuated the resistor R2 is momentarily connected to ground via the low resistance of the lamps which have been selected. The transistor T1 is no longer polarized and becomes blocked. It follows that the transistor T2 is polarized by the resistor R4 and becomes conductive. The resistor R5 and the relay R11 are supplied with current. The potential El at the point E is fixed by the resistors R4 and R5 in parallel and the relay R11. The resistor R5 is much weaker than the resistor R4, so that the potential El is far higher than Eo. This new potential has the following results: - the transistor T1 is now blocked, because the potential of its base is lower than that of the emitter.

- the relay R11 is energized.

The contact ml of the relay R11 then assumes the operating position tl, the lamps come on and the resistor R2 is restored to the positive value of the supply voltage. The capacitor C1 then begins to discharge via the resistors R1 and R2. As soon as the contact ml closes the relay R12 is energized and its contact m2 assumes the operating position t2. The resistor R6 is in parallel with the resistor R5. The potential at the point E is approximately equal to R11 E2 = UA X R1 + R5 x R6 RS x R6 which defines the operation at the normal flashing frequency.

The discharge of the capacitor C1 ceases when the potential of the base of the transistor T1 reaches the potential E2 at the point E increased by the conduction threshold of the transistor T1. At this moment the transistor T1 becomes conductive, which causes the transistor T2 to be blocked. The potential at the point E returns to the value Eo and the relay R11 is no longer energized. The lamps go out and the capacitor C1 re-charges via the resistor R1, the base-emitter junction of the transistor T1, the coil of the relay R11 and the resistor R2 connected to ground via the lamps The charging ceases again when the current becomes insufficient to maintain conduction in the transistor T1. The discharge process then begins as before (as indicated by the full line in Figure 3).

If one of the lamps switched over fails to function, the current passing through the lamps which have come on is insufficient to energize the relay R12, of which the contact M2 remains open. The potential at the point E, throughout the time when the lamps are on, remains equal to Ril A = UA X Ril + R5 This potential is of a lower absolute value than the preceding potential. The voltage difference between this new potential and the idle potential is therefore lower than in the case of normal operation. The discharge time and the charging time are therefore shortened, the corresponding curve being that shown by dotted lines in Figure 3. The flashing frequency has increased.

The relay R12 is simply a switch sensitive to the current passing through the lamps which have been switched over and which are alight. In the version shown in Figure 2 it is replaced by a transistor T3 of which the collector is connected to the resistor R6 and of which the emitter is connected to the positive terminal of the supply source. The base of the transistor T3 is connected to one end of a shunt S and also to the contact ml of the relay R11, while the other end of the shunt S is connected to the positive terminal of the supply source.

WHAT WE CLAIM IS: 1. Flashing light control unit for indicator lamps of motor vehicles comprising a capacitor of which one plate is connected to the positive terminal of a d.c. source while the other plate is connected to the base of a first transistor via a first resistor, said base being connected to the positive terminal via a second and a third resistor in series, the collector of the said first transistor being connected to the positive terminal via a fourth resistor and to the base of a second transistor having its emitter connected to the emitter of the first transistor, and its collector-emitter circuit series connected with a fifth resistor and a relay coil, the contact of the said relay being interposed between the positive terminal and a point situated between the second and the third resistor, the said point being connected to a manual selector switch for the indicator lamps.

2. Control unit as claimed in claim 1, wherein the said fifth resistor is mounted between the collector of the said second transistor and the positive terminal of the supply source, while the said relay coil is mounted between the common point of the emitters of the two transistors and the negative terminal of the supply source.

3. Control unit as claimed in claim 1. wherein the said fifth resistor is mounted between the common point of the emitters of the two transistors and the negative terminal of the supply source, while the said coil is mounted between the collector of the second transistor and the positive terminal of the supply source.

4. Control unit as claimed in claim 1, 2 or 3, wherein a switch sensitive to the current passing through the lamps which have been selected and which are alight is connected between the contact of the relay and the positive terminal of the supply source, the said switch controlling a sixth resistor mounted between the collector of the second transistor and the positive terminal of the supply source.

5. Control unit as claimed in claim 4, wherein the said switch consists of a current relay of which the contact is mounted between the said sixth resistor and the positive terminal and of which the coil is mounted between the contact of the first relay and the positive terminal.

6. Control unit as claimed in claim 4, wherein the said switch comprises a transistor of which the collector is connected to the said sixth resistor, of which the emitter is connected to the positive terminal of the supply source and of which the base is connected both to the contact of the first relay and to one end of a shunt of which the other end is connected to the positive terminal.

7. A flashing light control unit for lights, substantially as described herein with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Ril A = UA X Ril + R5 This potential is of a lower absolute value than the preceding potential. The voltage difference between this new potential and the idle potential is therefore lower than in the case of normal operation. The discharge time and the charging time are therefore shortened, the corresponding curve being that shown by dotted lines in Figure 3. The flashing frequency has increased. The relay R12 is simply a switch sensitive to the current passing through the lamps which have been switched over and which are alight. In the version shown in Figure 2 it is replaced by a transistor T3 of which the collector is connected to the resistor R6 and of which the emitter is connected to the positive terminal of the supply source. The base of the transistor T3 is connected to one end of a shunt S and also to the contact ml of the relay R11, while the other end of the shunt S is connected to the positive terminal of the supply source. WHAT WE CLAIM IS:

1. Flashing light control unit for indicator lamps of motor vehicles comprising a capacitor of which one plate is connected to the positive terminal of a d.c. source while the other plate is connected to the base of a first transistor via a first resistor, said base being connected to the positive terminal via a second and a third resistor in series, the collector of the said first transistor being connected to the positive terminal via a fourth resistor and to the base of a second transistor having its emitter connected to the emitter of the first transistor, and its collector-emitter circuit series connected with a fifth resistor and a relay coil, the contact of the said relay being interposed between the positive terminal and a point situated between the second and the third resistor, the said point being connected to a manual selector switch for the indicator lamps.