Electric switching device

Technical Field:

The present invention relates to an electric switching device especially for vehicle lighting includ¬ ing a first consumer of electric current, a second consumer of electric current, a first electrical cir¬ cuit, which contains at least one manual switch, and a second electrical circuit, parallel to the first elec¬ trical circuit, which contains a relay device, which includes at least one relay.

Technical Problem:

Problems such as undesired drops in voltage often arise when relatively strong currents must be redirect¬ ed via manually accessible switches. An additional problem is that the use of' normal relay connections is, for reasons of safety, often not satisfactory. These problems arise when, for example, two alternating con¬ sumers, such as the incandescent filaments in dimmable headlamps for vehicles, are to be supplied with current.

The object of the present invention is to solve the problems mentioned above.

The Solution:

The problems mentioned above are eliminated according to the present invention by means of a device characterized by having a relay maneuver circuit, be¬ longing to the relay device, containing a semiconductor.

Brief Description of the Drawings:

The device is described here in connection with two embodiments which are shown in associated drawings. Fig. 1 shows a simplified picture of the electrical installation under discussion, located in a car; fig. 2 shows the circuit diagram for a basic embodiment of the

device; fig. 3 shows the circuit diagram for an embodi¬ ment which is suitable for complementing the existing electrical systems of most vehicles; and fig. 4 shows the construction of this embodiment.

Best Mode of Carrying out the Invention:

As may be seen in fig. 1, the length of the cur¬ rent circuit from a battery 1 to a main switch 2 and a light switch 3, which are installed at the position of the operator in a car, and onwards to the headlamps 4 and 5, is considerable compared to the direct distance from the battery to the headlamps. For that reason, it is not uncommon that the electrical resistance in the current circuit exceeds 1 ohm, which, when using, strong halogen lamps in the headlamps leads to a voltage drop of 2 to 3 volts, or, 15 to 25%. In accordance with the invention, this voltage drop is lessened to almost zero by providing a second current circuit which, via a relay 6, follows the shortest path from the battery to the headlamps. This would constitute known art if the current circuit via light switches and other electrical switches were used to supply control current to the relay 6.

Such a device, which is known in and of itself, has however the weakness that the very important light function depends upon the reliability of the relay. In contrast to this is the device according to fig. 2, where the current circuit battery - main switch - switch - headlamp is intact and is itself functionally sufficient, whereas the relay 6 is contained in a second current circuit which is parallel to it.

As is seen in fig. 2, the switch 3 includes a switch arm 18. Each of the headlamps 4 and 5 include a bright light lamp 8 and a dim light lamp 9. When the main electrical switch 2 is closed and the switch 3 is positioned so that the points "a" and "b" shown in fig. 2 are in direct electrical contact with each other via the switch arm 18, the dim light lamps 9 are lit. Fig. 2 shows the switch 3 in this position. When the main

electrical switch 2 is closed and the switch 3 is posi- . tioned so that the points "a" and "c" as shown in fig. 2 are in direct electrical contact with each other via the switch arm 18, the bright light lamps 8 are lit. In this latter case current is also led through the dim light lamps 9, but since the resistance of the control coil of the relay 6 is much greater than the resistance of the dim light lamps 9, the voltage drop over the dim light lamps 9 will be very small. The control coil of the relay 6 is connected via a diode 7 between the lead-in wires for the bright light lamps 8 and the dim light lamps 9 of the headlamps in such a way that the coil receives current when the bright light lamps 8 are lit and the dim light lamps 9 are unlit. The relay thereby closes , the second current circuit, which is parallel to and much shorter than the first. The voltage drop in the lead-in wires is thereby reduced to almost zero at the same time as the reliability is increased many times over since the relay 6 remains closed even if the current circuit via the switch 3 were to happen to be broken. Only by means of manually switching the switch 3 to the dim light position will the difference in voltage over the coil of the relay 6 become so small that the relay 6 will open, thereby also causing the second current circuit to be opened.

The simple basic form shown in fig. 2 is, how¬ ever, insufficient for the needs of vehicles which are completely equipped with light signals and a stepping relay. The circuit shown in fig. 3 is therefore provid¬ ed. The battery, the switch, and the lamps for bright and dim lights are shown using the same designations as in fig. 2, whereas corresponding relays and diodes, now each two in number, are designated 6a, 6b and 7a, 7b.

The corresponding switch 19 includes a switch arm 20 which is such that it can effect simultaneous elec¬ trical contact between the point which is designated as "a" in fig. 3, and the points which, in fig. 3, are designated "b" and "c". A neutral position is defined as the placement of the switch 19 for which the point

"a" has electrical contact with neither the point "b" or the point "c". A parking light position is defined as the position of the switch 19 at which the point "a" is in electrical contact with the point "b " but not with the point "c", via the switch arm 20. A headlamp position is defined as the position of the switch 19 for which the point "a" is in simultaneous electrical contact with both the point ^,r b" and the point "c" via the switch arm 20.

A capacitor 11 and thyristor 12 are also included and are connected to the lead-in wires of parking light lamps 10. An existing stepping relay 21 has a contact 13 for a light signal, the control circuit of which is influenced by a contact 14, and a contact 15 which alternately closes the circuits of the bright and the dim light lamps under the influence of the contact 14, provided that the switch 19 is in the headlamp posi¬ tion. The operation is as follows: as long as the switch 19-'is in the neutral position, the relays 6a, 6b are unaffected by a light signal being given by the contacts 13 and 14, since the anode of the thyristor 12 is at zero electrical potential. Neither are the relays influenced by the light signal being given when the switch 19 is in the parking lamp position, since the firing circuit of the thyristor over the capacitor 11 is connected only to the dim light lamps and is not affected by the voltage of the light signal. Only when the switch 19 is in the headlamp position will the parking lamps 10 as well as the dim light lamps 9 receive voltage, with the result that the thyristor 12 becomes conductive. In this case not only is a circuit system according to the basic form shown in fig. 2 established with the relay 6a and the diode 7a for the bright light lamps 8, but an analogous system with the relay 6b and the ^' diode 7b for the dim light lamps 9 is additionally established. The two systems control each other since the contact 15 of the stepping relay 21 alternately causes the one relay coil to become almost without voltage by lighting the lamps which are asso-

ciated with the other. When the switch 19 is in the neutral position, the thyristor 12 once again becomes non-conductive so that the coils of the two relays become unenergized.

A practical embodiment of the device is shown in fig. 4. The relays 6a, 6b are mounted on a printed circuit which carries remaining components between the relays. The wires for each lamp terminate at a plate which carries two thin perpendicularly arranged springs 16, 17, sized so as to be inserted into the lamp contact together with the pins of the lamp.