The present invention relates generally to a device for detecting whether any one of a number of fuses in an electrical system has blown out.
A machine, such as an automobile, which incorporates a large number of electrical devices, such as ignition loads, radio sets, various different lamps, etc., requires a relatively large number of fuses for protecting the loads from excessive current, and for guarding against fire and so on caused by short circuits. Various devices have been proposed for detecting whether any of thses fuses have been blown out. For example, a fuse blowing detector such as shown in FIG. 1 of the accompanying drawings has been suggested. In this device, an automobile has an electric system which includes loads L1, L2, L3 fed from a battery 1 through an accessory switch SW1, loads L4 and L5 fed through an ignition switch SW2, and loads L6 and L7 fed directly from the battery. These loads L1-L7 are fused by fuses F1-F7 respectively. Several switches are shown as controlling supply of power to some of the loads, such as S1, S3, S4, and S6. The fuse blowing detector shown in FIG. 1 includes wires to each of the junctions between a fuse and its load, and a slidable changeover switch 2 which has a plurality of fixed contact points 2a connected to the other ends of these wires. The slidable contact 2b is capable of contacting each of these fixed contacts, by the movement of a slide lever 3 and an indicator lamp 4 having one terminal connected to the slidable contact 2b and an other terminal to the earth of the vehicle.
In operation, the ignition switch SW2 and the accessory switch SW1 are closed, and the slide lever 3 is moved to and fro. If all the fuses are intact, the lamp 4 is lighted each time slidable contact 2b and a fixed engage 2a contact. However, if any one of the fuses is blown, contact between slide lever 3 and the corresponding fixed contact, does not cause lamp 4 to light, thereby signalling blowing of the fuse.
This detector, however, has certain disadvantages because the use of a mechanical part, such as the slide lever 3, makes the detector prone to malfunctions. Another disadvantage is that the number of movements of the slide lever 3 for each test sequence is equal to the number of fuses. Further, use of only one lamp has made it difficult to know which fuse is defective.