Title of Invention

AN ELECTRO MAGNETIC TRIP DEVICE FOR A CIRCUIT BREAKER AND ELECTRICAL PROTECTION APPARATUS COMPRISING SUCH A DEVICE

Abstract

The invention relates to an electro magnetic trip device (5), in particular for a circuit breaker D, comprising at least one core called the moving core associated to a rod, the assembly being mounted sliding inside a sheath (7), and induction coil (11) through which the current to be monitored flows and designed to generate, when this current exceeds a certain threshold, a magnetic field able to generate movement of the moving " core and the rod between a rest position and a position in which an end of the rod forming a striker commands tripping of the opening and closing mechanism (3) of the contacts (1, 2), a means for channeling the magnetic field generated by the coil (11) and an arcing horn (13) electrically connected to the stationary contact and designed to guide the arc in the direction of the arc extinguishing chamber C during breaking. The means for channeling the magnetic field is formed by the arcing horn (13) itself, said horn (13) being arranged so that the magnetic flux generated by the coil (11) and originating from the moving core flows successively through the stationary contact (1) of the apparatus and the arcing horn (13) before rejoining the moving core.

Full Text

The present invention relates to an electro magnetic trip device for a circuit breaker and an electrical protection apparatus comprising such a device. Low voltage circuit breakers generally comprise, in a manner know as such, magnetic tripping means designed to cause tripping of the circuit breaker mechanism when a sudden current increase occurs following for example a short-circuit, and thermal tripping means designed to cause tripping of the circuit breaker mechanism in the event of an overload resulting in a slow current increase. According to a known achievement described in the Patent documents FR 2,630,582 and FR 2,368,139, these magnetic tripping means comprise an induction coil mounted around a rod forming a striker associated to a moving core, the assembly being mounted sliding inside a sheath, the rod sliding inside a fixed core secured inside the sheath. The rod bears via one of its ends on the moving core. A spring mounted around the rod is interposed between the two cores and is designed to return the two cores to a separated position in the rest position of the trip device. This device comprised in addition a shell mounted around the assembly formed by the core and the striker and electrically connected to the stationary contact of the apparatus, said shell being designed to channel the magnetic field generated by the coil. In operation, when a sudden current increase occurs, a magnetic field is generated by the coil. When the current value exceeds a preset threshold, the moving core moves in the direction of the fixed core against the force of the spring and drives the rod in its movement, causing unlocking of the circuit breaker mechanism and opening of the contacts by the striker formed at the end of the rod. This type of magnetic trip device is however particularly bulky and cumbersome, due on the one hand to the presence of the shell and on the other hand to the large number of parts involved. This large number of parts results in the number of positioning constraints being relatively large. In particular, the magnetic threshold is dependent on the value of the air-gap between the two fixed and moving cores and the value of this air-gap has to be adjusted precisely. OBJECT OF THE INVENTION The present invention overcomes these drawbacks and proposes a magnetic trip device of simple design, of small dimensions, operation of which has been made more reliable, and an electrical protection apparatus such as a circuit breaker comprising such a device. The object of the present invention is to provide an electro magnetic trip device as described herein. Accordingly, the present invention provides an electro magnetic trip device, able to cause tripping of the opening mechanism of the stationary and movable contacts of the apparatus when a sudden current increase occurs following for example a short-circuit, comprising at least one core called the moving core associated to a rod said moving core and said rod being mounted sliding inside a sheath, a coil through which the current to be monitored flows and able to generate, when this current exceeds a certain threshold, a magnetic field designed to cause movement of the moving core and the rod between a rest position and a position in which an end of the rod forming a striker commands tripping of the said mechanism, a means for channeling the magnetic field generated by the coil and an arcing horn electrically connected to one of the contacts and designed to guide the arc in the direction of the arc extinguishing chamber during breaking, characterized in that the means for channeling the magnetic field are formed by said arcing horn, said arcing horn being electrically connected to the stationary contact and having a continuous arching horn extending parallel to the axis of the coil, said horn being arranged so that the magnetic flux generated by the coil and originating from the moving core flows successively through the stationary contact of the apparatus and the arcing horn before rejoining the moving core, and that it comprises a moving core only. According to another feature, the above-mentioned rod is securedly affixed to the moving core. Another object of the present invention is to achieve an electrical protection apparatus, in particular a circuit breaker, comprising the above features either along or in combination. BRIEF DESCRIPTION OF THE DRAWINGS But other features and advantages of the invention will become more clearly apparent from the following detailed description which refers to the accompanying drawings given for example purposes only and in which: Figures I and 2 are two schematic views respectively illustrating a magnetic trip device according to the prior art and a magnetic trip device according to the invention. Figure 3 is a partial perspective view, illustrating the inside part of a circuit breaker equipped with a magnetic trip device according to the invention. Figure 4 is a plane view of the previous figure, and Figure 5 is a cross-sectional view along V-V of the previous figure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In figures 3 to 5, a low voltage electrical circuit breaker D can be seen designed to be used to protect an electrical circuit against overloads or short-circuits. This circuit breaker D comprises mainly, in a manner known as such, a pair of separable contacts 1, 2 respectively stationary and movable, an operating mechanism 3 for opening and closing of the contacts actuated by a handle 4, an electromagnetic trip device 5 designed to trip the mechanism 3 of the circuit breaker D and thus cause opening of the contacts 1, 2 when a short-circuit current occurs, and a thermal trip device 6 (not represented) designed to trip the mechanism 3 when a current overload occurs. In figure 1, a magnetic trip device 5 according to the prior art can be seen. This device 5 comprises a core called the fixed core 6, fixed in a sheath 7, a moving core 8 mounted sliding inside said sheath 7, a rod 9 mounted sliding inside the fixed core 6 parallel to the direction of sliding of the moving core 8, a spring 10 interposed between the two cores 6, 8 and an induction coil 11 mounted around the sheath 7. This device further comprises a shell 12 moimted around the sheath 7 so as to channel the magnetic flux generated by the coil 11, and an arcing horn 13 electrically connected to the stationary contact 1 of the circuit breaker and enabling the arc to be guided in the direction of the arc extinguishing chamber C during breaking. The above-mentioned rod 9 comprises a first end 9a bearing on the moving core 8 and a second end 9b forming a striker. In operation, when the current is greater than a certain threshold, the coil 11 generates a magnetic field designed to counteract the force of the spring 10 and to move the moving core 8 in the direction of the fixed core 6. This moving core 8 then drives the rod forming the striker in its movement, which rod acts on the trip bar 14 of the apparatus and causes unlocking of the mechanism 3. The flux generated by the coil 11 passes through the shell 12 (as illustrated by the arrows), and is channeled by said shell 12 so as to obtain a maximum efficiency of the magnetic field. During breaking, the arcing current flows through the arcing horn 13 and then towards the arc extinguishing chamber C. The breaking capacity associated to such a device is about 20 kA. Unlike the prior art device, the magnetic trip device 5 according to the invention, as illustrated in figures 2 to 5, does not comprise a shell to channel the magnetic field. This function is performed by the arcing hom 13 itself securedly affixed to the stationary contact, through which arcing hom the corresponding magnetic flux flows when the coil 11 generates a magnetic field, said arcing hom therefore channeling this flux. According to the embodiment described in figures 2 to 5, the device no longer comprises a fixed core, which results in the magnetic threshold being independent from the air-gap between the fixed core and moving core contrary to what was the case in the prior art. Thus, the expression "a moving core only" should be interpreted as meaning that the device does not comprise a fixed core. In this embodiment, the spring 10 is fitted between a part of the sheath 7 and the moving core 8. The rod 9 is securedly affixed to the moving core 8. It can be seen in the figures that the arcing hom is continuous and extends parallel to the axis of the coil over a certain length, which enables the arc to make a single switching. Operation of the device is the same as that of the prior art device and will therefore not be described anew, with the difference that on the one hand the moving core 8 is no longer attracted by the fixed core 6, the magnetic force generated by the coil 11 being sufficient to move the movable contact 8. The breaking capacity is limited to 10 kA. A magnetic trip device has therefore been achieved by means of the invention, which trip device is of simple design, economical and of reduced dimensions due to the fact that a smaller number of parts are used. This reduction of the number of parts also results in a reduction of the number of positioning constraints making operation of the device more reliable. In particular, as the magnetic threshold is independent from the air-gap, the latter no longer has to be adjusted precisely. Also, the length of the moving core can be reduced due to the fact that the latter no longer operates in conjunction with the shell. Naturally, the invention is in no way limited to the embodiments described and illustrated which have been given for example purposes only. On the contrary, the invention extends to encompass all the technical equivalents of the means described and combinations thereof provided that the latter are performed according to the spirit of the invention. WE CLAIM: 1. An electro magnetic trip device, able to cause tripping of the opening mechanism of the stationary and movable contacts of the apparatus when a sudden current increase occurs following for example a short-circuit, comprising at least one core called the moving core (8) associated to a rod (9), said moving core and said rod being mounted sliding inside a sheath (7), a coil (11) through which the current to be monitored flows and able to generate, when this current exceeds a certain threshold, a magnetic field designed to cause movement of the moving core and the rod between a rest position and a position in which an end of the rod forming a striker commands tripping of the said mechanism, a means for channeling the magnetic field generated by the coil and an arcing horn (13) electrically connected to one of the contacts and designed to guide the arc in the direction of the arc extinguishing chamber during breaking, characterized in that the means for channeling the magnetic field are formed by said arcing horn (13), said arcing horn (13) being electrically connected to the stationary contact and having a continuous arching horn extending parallel to the axis of the coil, said horn being arranged so that the magnetic flux generated by the coil (II) and originating from the moving core (8) flows successively through the stationary contact (1) of the apparatus and the arcing horn (13) before rejoining the moving core (8), and that it comprises a moving core only. 2. The device as claimed in claim 1, wherein said rod (9) is securedly affixed to the moving core (8). 3. An electrical protection apparatus comprising an electro magnetic trip device as claimed in claim 1 or 2. 4. An electro magnetic trip device substantially as herein described with reference to Figures 2 to 5 of the accompanying drawings

Documents:

0196-mas-2001 abstract-duplicate.pdf

0196-mas-2001 abstract.jpg

0196-mas-2001 abstract.pdf

0196-mas-2001 claims-duplicate.pdf

0196-mas-2001 claims.pdf

0196-mas-2001 correspondence-others.pdf

0196-mas-2001 correspondence-po.pdf

0196-mas-2001 description (complete)-duplicate.pdf

0196-mas-2001 description (complete).pdf

0196-mas-2001 drawings.pdf

0196-mas-2001 form-1.pdf

0196-mas-2001 form-18.pdf

0196-mas-2001 form-26.pdf

0196-mas-2001 form-3.pdf

0196-mas-2001 form-5.pdf

0196-mas-2001 others.pdf

0196-mas-2001 petition.pdf