Fuse Cartridge of the Type With Functioning Indicator

The present invention relates to fuse cartridges intended for the protection of electrical circuits and it concerns more particularly those which are equipped with a functioning indicator adapted permanently to inform on the state of the fuse or fuses incorporated.

It is known that the body of cartridges of this type generally comprise an insulating envelope which is closed by lateral connection heads provided with connection knives and which contains a mass of siliceous matter within which is embedded at least one meltable element connected to said heads. In parallel with this fuse, there is additionally provided between the heads a conductive wire of much reduced section which retains, against a spring or other elastic means, a striking element mounted in a cavity made in the envelope, which striking element, when it is released, is adapted to act against the actuation knob of a micro-switch connected to the supply of an alarm circuit.

It will be appreciated that, in normal operation, the whole of the current is conveyed by the fuse, with the result that the striking element, maintained by its conductive wire, is in the retracted position. On the contrary, in the event of accidental overintensity, the fuse and the conductive wire are destroyed by melting, with the result that, under the effect of its spring, the striking element actuates the micro-switch and the alarm circuit which is associated therewith.

This arrangement is well known in the art and has been described in detail in particular in French Patent No. 1 560 404 of Dec. 26, 1966 in the name of LUCIEN FERRAZ ET CIE.

It goes without saying that, if it is intended to obtain maximum safety of use, the alarm circuit should be maintained supplied for as long as the operator has not replaced the meltable cartridge and re-set the striking element. In practice, one must thus resort to micro-switches of the bistable type which comprise a position of rest and a position of functioning, the passage from one to the other being effected by means of a fleeting pressure on the actuation knob.

Now, micro-switches of the bistable type present much larger dimensions and clearly much higher cost than those of the monostable type. In addition, their functioning most often involves a more accentuated effort of actuation, which results in associating with the striking element a more powerful thrust spring and a retaining conductive wire of larger section.

It is a principal object of the present invention to overcome these drawbacks, and this by arranging the cartridge so that it is capable of being provided with a monostable micro-switch adapted to function in the manner of a bistable micro-switch.

To that end, the invention essentially consists in interposing between the striking element and the actuation knob of the micro-switch an intermediate lever which, due to its cam-shaped profile, is adapted to take two stable positions and thus to give to the actuation knob the two stable positions desired.

The accompanying drawing, given by way of example, will enable the invention, the characteristics that it presents and the advantages that it is capable of procuring, to be more readily understood.

FIG. 1 shows, in axial half-section, the general arrangement of a fuse cartridge according to the present invention.

FIGS. 2, 3 and 4 illustrate on a larger scale the structure and functioning of the functioning-indicator system of the cartridge according to FIG. 1.

In its general arrangement, the cartridge in question is similar to that described in detail in French Patent No. 1 560 404 mentioned above. There is found an insulating envelope 1, closed laterally by two connection heads 2 of which each is provided with a connection knife 3. The space thus defined by the body 1-2 contains a siliceous mass 4 in which is embedded at least one meltable blade 5 whose ends are rendered fast with the heads 2. The latter are in addition connected to one another by a conductive wire 6 of highly reduced section, which follows the inner wall of the envelope 1 and which is shaped to determine a central loop adapted to retain, against its spring 7, a striking element 8 mounted to slide in a lateral cavity in said envelope. With this striking element 8 is associated a micro-switch 9 borne by an insulating support 10 fixed to the body 1-2 by two small lateral square brackets 11, which micro-switch ensures control of an electrical alarm circuit connected to its terminals 9.

Whereas in the conventional construction the striking element 8, once released by melting of the conductive wire 8, acts directly against the actuation knob 12 of the micro-switch 9, according to the invention, there is interposed between said striking element and knob a rocking lever 13 profiled in the manner of a cam.

As is particularly visible in FIG. 2, the support 10 is largely hollowed out and supports in its hollow a fixed transverse pin 14 on which the lever 13 is idly mounted. The latter, provided with two arms 13a and 13b oriented perpendicularly to each other, is profiled in its central part to present two bearing surfaces 13c and 13d, themselves oriented square. The arm 13b is disposed immediately above the central boss 8a of the conventional cap 8b which covers the striking element 8, whilst part 13c forms bearing for the actuation knob 12 urged by elastic means 12a incorporated in the micro-switch 9.

When the cartridge has an electrical current passing therethrough whose intensity is less than nominal, the parts are in the standby position illustrated in FIG. 2. The lever 13 whose profile is such that it is substantially in equilibrium on its pin 14, is retained in this position by the friction resulting from the pressure exerted by the knob 12 against the bearing surface 13c; the bearing surface 13d is in abutment against a crosspiece 10a of the support 10. If the effect of the vibrations capable of being imparted to the cartridge is feared, this retaining may be improved either by providing a relief or tooth 13e at the end of the bearing surface 13c, or by offsetting the pin 14 with respect to the vertical axis of the actuation knob 12.

The release of the striking element 8 under the effect of simultaneous melting of the meltable blade 5 and of the retaining wire 6 provokes the displacement of the striking element 8 under the action of its spring 7 and an effect of thrust against the arm 13b of the lever 13, which rocks in the manner illustrated in FIG. 3 until it takes the position of signalization shown in FIG. 4. The knob 12 slides downwardly under the effect of its spring 12a with the result that the microswitch 9 controls the alarm circuit connected to its terminals 9a.

This position is perfectly stable, even if it is assumed that, for any reason, the boss 8a of the cap 8b of the striking element 8 ceases its action of thrust against the arm 13b. In fact, the knob 12, urged by its spring 12a, exerts its action against a profiled ramp 13f provided on the lever 13 between the bearing surfaces 13c and 13d, with the result that, in any case, said lever is maintained applied against a bearing 10b made to that end in the support 10.

It should be observed that, in addition to the electrical alarm circuit thus started, the functioning of the cartridge is rendered visible from the outside, as the 13a of the lever 13d has left the position according to FIG. 2 for which it was applied against the wall of the micro-switch 9, to take the oblique position in projection illustrated in FIG. 4.

It will be understood in any case that the inner mechanism of the micro-switch 9 may be absolutely any one, particularly of the bistable type, since it is the intermediate lever or cam 13 which gives the actuation knob 12 two perfectly stable positions.

It goes without saying that, to reset the micro-switch 9 after replacement of the fuse cartridge, it suffices to maneuver the lever 13 manually to pass it from the position of FIG. 4 to that according to FIG. 2.

It must, moreover, be understood that the foregoing description has been given only by way of example and that it in no way limits the domain of the invention which would not be exceeded by replacing the details of execution described by any other equivalents. In particular, it is imagined that the lever 13 may be provided to be sufficiently wide to ensure, alone, the actuation of two micro-switches 9, mounted side by side on the insulating support 10.