GB2068665A

GB2068665A - Vehicle brake lamp monitoring device

Info

Publication number: GB2068665A
Application number: GB8101425A
Authority: GB
Original assignee: Jaeger
Priority date: 1980-01-21
Filing date: 1981-01-16
Publication date: 1981-08-12
Also published as: FR2474269B1; IT8026924A0; DE3101633A1; IT1134890B; ES8204269A1; AR225340A1; GB2068665B; FR2474269A1; ES498811A0

Abstract

A device for operating and checking the satisfactory operation of brake warning lamps situated at the rear of the vehicle comprises a spindle 1 slidably mounted in a bush 2 and provided with a restoring spring 8 which causes the spindle to slide, when the brake pedal is depressed to remove pressure from one end of the spindle, so that a contact 6 carried by the other end of the spindle makes with contacts 9, 10 of an electronic circuit board 3, whereby to energise the brake lights. The circuit of board 3 is arranged to carry out the checking and is disposed, together with the contacts 6, 9, 10 and said other end ofthe spindle, in a common casing 5 of height sufficient to accommodate the travel of the spindle. <IMAGE>

Description

SPECIFICATION Vehicle brake lamp monitoring device The present invention relates to a device for operating and checking the satisfactory operation of brake warning lamps situated at the rear of a motor vehicle.

The satisfactory operation of brake warning lamps is an important factor in the safety of a vehicle, but their siting at the rear of the vehicle presents problems in warning the driver in the event of their failure.

In accordance with the present invention, there is provided a device for operating and checking the satisfactory operation of brake warning lamps situated at the rear of a vehicle, comprising a spindle slidably mounted in a bush and provided with a restoring spring and having an end portion for receiving pressure from a brake pedal, a movable contact carried on the other end portion of the spindle, and two contacts for connection to respective said brake warning lamps and co-operable with said movable contact and both fixed to a circuit board carrying an electronic circuit arranged to carry out said checking, said circuit board and said contacts and said other end portion of the spindle being disposed within a common casing having a height at least equal to the travel of said spindle in its bush.

An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a section through a device for operating and checking the satisfactory operation of vehicle brake warning lamps; Figure 2 is a diagram of an electronic control circuit of the device; and Figure 3 is a diagram showing association of the device with a brake pedal.

The device comprises a spindle 1 (Figure 1) which in use is mounted for one of its end portions to bear against a brake-actuating pedal 24 (Figure 3). This spindle is mounted to slide in a bush 2 and has a reduced-diameter portion which defines a collar 11 against which one end of a spring 8 bears, the other end of the spring bearing against an internally chamfered end portion 12 of the bush 2. The reduced-diameter end portion of the spindle 1 is equipped with a circlip 7 to which there is fixed an annular contact 6. This contact cooperates with three contacts fixed to a printed circuit board 3 which carried an electronic circuit.One of the three contacts (not illustrated) is connected to an electrical supply point for the device, and the other two contacts 9 and 10 are in use of the device connected respectively to left-hand and right-hand brake warning lamps 15 and 16 (Figure 2) situated at the rear of the vehicle. A cable 13 contains conductors connecting the circuit to the two warning lamps, to alarm elements 14, 21 and to an electrical supply of the vehicle. The reduced-diameter end portion of the spindle 1, the contacts and the printed circuit board are housed in a casing 5, closed by a plate 4, the dimensions of which are those normally occupied by a brake warning lamp contactor of conventional type mounted on motor vehicles. The height of the casing 5 is such as to accommodate the travel of the spindle 1 when this slides in the bush 2.The contactor is normally open, that is to say that in the position of rest of the brake pedal 24, the pedal exerts sufficient pressure on the spindle 1 to compress the spring 8 (Figure 3); the movable contact 6 is thus held away from the three fixed contacts and the electrical circuit to the warning lamps is not established. On the contrary, when the brake pedal is urged in the direction of the arrow F, it relaxes its pressure on the spindle 1 which is then restored into the "working" position by the spring 8 and electrical contact is established between the movable contact 6 and the three contacts fixed to the printed circuit 3. The electronic circuit is symmetrical, in that an alarm element and its control sub-circuit are associated with each of the brake warning lamps.Thus, the left-hand warning lamp 15 is provided with an alarm lamp 14which is connected between earth and the emitter of an NPN transistor 17, the collector of which is connected to the collector of a PNP transistor 18. The emitter of this transistor 18 is connected to a protective diode 28 itself connected to a positive pole of a d.c. electrical supply of the vehicle through an enabling contact. The bases of the transistors 17 and 18 are connected through respective resistors 19 and 20 to a point A between the warning lamp 15 and its control contact 9, the contact 6 a!so being connected to a positive pole of the electrical supply.

When the brake pedal is at rest, the contact 9 is open from contact 6; if the warning lamp 15 is in a satisfactory state of operation, its resistance is very low (of the order of 6Q when it is lit) and, the values of the resistors 19 and 20 being selected in such a manner (of the order of 1 kg) that the voltage at the base of the transistor 17 is nearly zero, a base current flows to the transistor 18 to saturate this transistor while the transistor 17 is blocked and the alarm lamp 14 is not activated.When the brake pedal 24 is actuated, the warning lamp 15 still being in a satisfactory state, the contact 9 closes to contact 6 and the positive supply voltage is applied to the base of transistor 17 to saturate this transistor whilst transistor 18 is blocked, and as the two transistors are connected in series and no collector current passes in the transistor 18, the alarm lamp 14 remains extinguished.

If the warning lamp 15 is defective, when the brake pedal 24 is at rest the contact 9 opens from contact 6 and the junction between resistors 19 and 20 is no longer connected to earth through lamp 15, so that transistor 17 conducts as well as transistor 18 (by virtue of an emitter-base current in each) and the alarm lamp 14 is activated. If the pedal 24 is then actuated, the transistor 18 is blocked on closing of the contact 9 and the alarm lamp 14 is extinguished.

As soon as the pedal is released, it is activated again.

The operation of the alarm lamp 21 associated with brake warning lamp 16 is identical; it is controlled by a sub-circuit composed of transistors 22 and 23 and resistors 26 and 27.

Claims

1. A device for operating and checking the satisfactory operation of brake warning lamps situated at the rear of a vehicle, comprising a spindle slidably mounted in a bush and provided with a restoring spring and having an end portion for receiving pressure from a brake pedal, a movable contact carried on the other end portion of the spindle, and two contacts for connection to respective said brake warning lamps and co-operable with said movable contact and both fixed to a circuit board carrying an electronic circuit arranged to carry out said checking, said circuit board and said contacts and said other end portion of the spindle being disposed within a common casing having a height at least equal to the travel of said spindle in its bush.

2. A device as claimed in claim 1, in which the electronic circuit comprises, associated with each said warning lamp, two transistors connected in series between an electrical supply point and an alarm element, the bases of the two transistors being connected to a point between the associated warning lamp and its said fixed contact.

3. A device as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.