This invention relates to a device for cutting off electric power to a circuit for protecting the same against excessive heat when generated therein during operation.

Illustrative of the several electric circuits that are heated during operation is the armature circuit of a starter motor of an automobile. Due to abnormal working of the starter motor, as for instance, during repeated use of the motor while starting, the armature gets heated beyond acceptable limits; and this can eventually lead to damage to the motor as well as to related components., apart from fire hazards endangering the vehicle Itself.

It is therefore an object of this invention to propose a device. which will protect electric circuits which are prone to damage by over heating, by cutting off, electric power supply whenever the heat generated exceeds a predetermined limit

The aforementioned object of this invention is not only to cut off power at the appropriate time, but also to ensure that power is cut off rapidly.

Various other features of this invention, not herein set fourth, will be apparent form
its further description given herein below.

The device, according to this invention , for cutting off electric power to a circuit for protecting the same against excessive heat when generated |therein during operation, comprises a conductor, for carrying electric current to said circuit, said conductor having first and second sections spaced from each other, to provide a gap there between a third section bridging the gap, while overlapping the first and second sections, to complete the path of current flowing through the conductor, the said third section being fastened to the first and second sections by metal fasteners of a predetermined melting point, whereby the conductor, together with the fasteners, on getting heated to the said predetermined point, results in the melting of the fasteners and consequent separation of the third section from the first and second sections, to open the gap, thus cutting off current flow through the said conductor-, and means provided for achieving rapid separation of the third section from the first and second sections.

This invention will now be described with the reference to the accompanying drawings in which Fig.l illustrates by way of example and not by way of limitation one of possible embodiments of this Invention and Flg.2 Illustrates also by way of example and not by way of limitation another possible embodiment of this invention.

A conductor E, for carrying electric current to a circuit, such as, for example, the armature circuit of the starter motor of an automobile, has first and second sections S1 S2 spaced from each other, to provide a gap G there between. A third section S3 bridges the gap, while overlapping the first and second sections S1 S2, to complete the path of current flowing through the conductor.

The third section S3 is fastened to the first and second sections S1 S2 by metal fasteners F1 F2. In the embodiment illustrated, these fasteners are shown as rivets, although other forms of fasteners are also possible.
The fasteners are made of a metal, such as, for example, solder, lead, tin, aluminum or eutectic alloy of a predetermined melting point, this melting point is selected to be the value of the temperature of the conductor at which po1mer supply to the conductor Is to be cut off to protect the circuit, such as, the armature circuit of the starter of an automobile.

Whenever the current carrying conductor E, together with the fasteners, gets heated to the said predetermined point, the fasteners melt, resulting in the separation t)f the third section S3 from the first and second sections SI S2 , to open the gap G. Once the gap is opened, the current path through the conductor is broken, to cut off power supply to the said circuit.

In order to ensure that the third section S3 separates rapidly from the first and second sections S1 S2, means are provided for achieving rapid separation. One form to such means will constitute two springs T1 T2. These springs have one o? their ends fixed respectively to the sections SI S2 leaving the other of their ends urged against the section S3. During separation of the section S3, the springs Tl T2 ensure that separation takes place rapidly.

Is an alternative, another form of such means will consist of a dead weight W attached to, or forming part of, the base portion of the section S3, this weight being sufficient to pull the said section downwards, equally rapidly, in the event of separation of the section S3 taking place.

A variation of what is illustrated In Fig.1 Is Illustrated In Fig.2 in which the insulating mats Ml and M2 are sandwiched between the sections, SI, S3 and S2, S3 respectively so much so that current flow is established from section SI to Section S3 through the fastener Fl only and not directly from section SI to Section S3. So also current flow from section S3 to section S2 is established only through the fastener F2 and not directly from section S3 to section S2. This is so because of the Intervening insulating mats Wt and M2. This embodiment Illustrated In Fig .2 would otherwise have the same features as that of the embodiment Illustrated In Fig.l. However, the pur1se of the second embodiment is to constrain current while passing form section s1 to s3 and from section s3 to section s2, to flow only through f1 and f2 thereby ensuring a higher density of current flow throughf1 and f2

From the foregoing description, it will be observed that various other embodiments of this invention are possible without departing from its scope and ambit.

I We Claim;

1. A device for cutting off electric power to a circuit for protecting the same against excessive heat when generated therein during operation, comprising a conductor, for carrying electric current to said circuit, said conductor having first and second sections spaced from each other, to provide a gap therebetween; a third section bridging the gap, while overlapping the first and second sections, to complete the path of current flowing through the conductor, the said third section being fastened to the first and second sections the metal fasteners of a predetermined melting point, whereby the conductor, together with the fasteners, on getting heated to the said predetermined point, results in the melting of the fasteners and consequent separation of the third section from the first and second sections, to open the gap, thus cutting off current flow through the said conductor; and means provided for achieving rapid separation of the third section from the first and second sections.

2. A device as claimed in Claim 1 wherein insulating mats are sandwiched between the first and third sections and the second and third sections respectively such that the current flow from the first section to the third section and from the third section to the second section is established only through the said fasteners.

3. A device as claimed in Claim 1 wherein such means constitute springs, one set of the ends of which are respectively fixed to the first and second sections, while another set of such ends are urged against the third section.

4. A device as claimed in Claim 1 wherein such means constitutes a dead
weight attached to the third section.

5. A device for cutting off electric power to a circuit for protecting the same against excessive heat when generated therein during operation. Substantially as herein described with reference to, and as illustrated in the accompanying drawings.