SWITCH

Abstract: A notched hollow portion is provided in the vicinity of the connection of a fixed contact of a fixed contactor, and an arc runner which is electrically connected to the fixed contactor is provided at the end of the hollow portion closer to the contact, so that it can extend over the hollow portion. This enables a reduction in wear of the fixed contact and a great improve­ ment in its breaker performance.

Description: This invention relates to a switch which has a stationary contact element joined on a stationary contact and a movable contact element joined on a movable contact and disposed in a facing relationship to said stationary contact element, which stationary contact has a cut-out portion in the vicinity of the portion at which said contact element is joined, and an arc runner electrically connected to said stationary contact at an edge of said cut-out portion close to said contact element, between the cut-out portion and the contact element, which arc runner extends from the stationary contact towards the movable contact element side and above said cut-out portion, and has an L-shaped cross-section, comprising a vertical leg portion joined to the said stationary contact element and a horizontal leg portion connected to said vertical leg portion and extending above said cut-out portion of the stationary contact. Switches to which the present invention is applicable include electromagnetic contactors and circuit breakers. First, one example of a conventional electromagntic contactor will be described with reference to Fig. 1 In fig. 1, 1 is a mount bed molded from a plastic material, 2 is a stationary iron core of silicon steel laminations disposed on the mount bed, 3 is a movable core disposed in a facing relationship with the stationary core 2 and made of silicon steel laminations, 4 is an operating coil for providing a driving force which attracts the movable core 3 to the stationary core 2 against a trip spring (not shown), and 5 is a cross bar made of a plastic material and having a rectangular window, the bottom end of which has attached thereto the movable core 3. 6 is a movable contact inserted within the rectangular window of the cross bar 5 and held under pressure by a compression spring 7, 6A is a movable contact element disposed on the movable contact, 8 is a stationary contact facingly disposed with respect to the movable contact 6 for conducting a current, 8A is a stationary contact element disposed on the stationary contact 8, and 8c is a terminal portion for the stationary contact 8. ( is a terminal screw for connecting the electromagntic contactor main body to an external circuit, 10 is a base for mounting the stationary contact 8, and 11 is a cover for covering the upper portion of the electromagnetic contactor. The manner of the mounting of the stationary contact 8 and the stationary contact element 8A is shown in enlarged views of Figs. 2(a) and 2(b). In the conventional electromagnetic contactor of the above-described structure, when the operating coil 4 is de-energized, the unillustrated trip spring causes the movable core 3 to separate from the stationary core 2 and the cross bar 5 occupies the position shown in Fig. 1, whereby the movable contact element 6A and the stationary contact element 8A are separated to generate an electric arc 12, the arc 12 being extinguished at the zero current point to interrupt the electric current. In the conventional electromagnetic contactor, as shown in Fig. 2, the arc 12 is subjected to a driving force F₂ due to a magnetic field formed by a current I flowing through the movable contact 6 and a driving force F₁ due to a magnetic field formed by a current I flowing through the stationary contact 8. Since the driving forces F₁ and F₂ are substantially equal in intensity and opposite in direction, the arc 12 stays on the movable contact element 6A and the stationary contact element 8A. Thus, since the arc 12 is not driven, the legs of the arc do not move outside of the contact elements and the wear of the contact elements is large. A switch according to the preamble of Claim 1, in which the arc is moved from a stationary contact element to an arc runner, is known from US-A-4 086 460. With the above points in view, the present invention has as its object to reduce the contact element wear and to improve the interrupting capability by modifying the arrangement of the stationary contact itself. According to the present invention, the switch is characterised in that a single stationary contact element 8A is provided, adjacent the vertical leg of the arc runner and directly in line with the arc runner, and a channel 10A for communicating the cut-out portion 8D to the exterior space at the lower portion 8D to the exterior space at the lower portion of the cut-out portion is provided in a support member 10 for supporting said stationary contact, for exhausting gas generated during the extinction of an arc generated between said stationary contact and said movable contact to the exterior through said hollow cut-out portion and said channel. The contact element wear is reduced and the interrupting capability is improved by providing the hollow cut-out portion in the stationary contact in the vicinity of the stationary contact element, and the electrically integral arc runner. The contact runner shape according to the invention facilitates the transfer of the arc from the stationary contact element onto the arc runner. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial sectional view of a conventional electromagnetic contactor; Figs. 2(a) and 2(b) are enlarged views showing the stationary contact shown in Fig. 1; Fig. 3 is an explanatory view illustrating the behaviour of the arc on the stationary contact of a conventional electromagnetic contactor; Figs. 4 and 5 are views illustrating the operation of the stationary contact in a contactor according to an embodiment of the present invention; Fig. 6 is a side view showing modification of the stationary contact; and Fig. 7 is a side view illustrating a contactor according to an embodiment of the present invention. The present invention will now be described in conjunction with embodiments shown in Figs. 4, 5 and 6. Since the electromagnetic contactor of this embodiment has the same structure except for the configuration of the stationary contact 8, only the configuration of the stationary contact 8 is shown in Fig. 4. As seen from the figures, the stationary contact 8 is provided with a hollow cut-out portion 8D close to the contact element or on the left end as seen in Fig. 4. Therefore, an electric current I flowing through the stationary contact 8 is divided into currents I 1A and I 1B on both sides of the hollow portion 8D and the currents flow into an electric arc 12. Forces that act on the arc due to the above currents are illustrated by arrows in Fig. 4(b). In this figure, the forces due to currents I 1A and I 1B are shown as F 1A and F 1B , and the resultant force of F 1A and F 1B is shown as F₁. On the other hand, a force due to the current flowing through a movable contact (6) is shown by F₂. Since F₂ 2F 1A 2F 1B , F₂ is greater than F₁. Therefore, the arc 12 is driven toward the arc runner 8B of the stationary contact, so that the leg of the arc 12 on the stationary contact element 8A is transferred onto the arc runner 8B as shown by the arc 12A shown in Fig. 5. The arc 12, once transferred onto the arc runner 8B, is further driven by an electric current flowing through the arc runner 8B to rapidly travel on the arc runner 8B as shown by the arc 12B, whereby the arc 12 is further elongated and extinguished. Thus, with the above described electromagnetic contactor, the current zero point occurs while the are 12 is rapidly travelling along the arc runner 8B while being elongated, so that the charged particles of the arc 12 are quickly scattered and the leg portion of the arc 12 is efficiently cooled, thereby providing a superior interrupting capability. Also, since the leg of the arc 12 transfers from the stationary contact 8A onto the arc runner 8B, the wear of the stationary contact 8A is significantly reduced. As to the configuration of the stationary contact 8, an advantageous effect similar to that shown in fig. 4 is obtained even with the terminal configuration having a U-shaped end portion 8C shown in Fig. 6. Since, the arc runner 8B is positioned in the vicinity of the stationary contact 8, the arc 12A moving along the arc runner 8B is subject to a reaction force due to an electric current flowing through the stationary contact 8, whereby the arc travel speed is reduced. For this reason, it has been found that it is necessary to reduce the reaction force acting against the arc driving force due to a magnetic field formed by an electric current flowing through the stationary contact 8 to further improve the interrupting capability. The stationary contact 8 is mounted on a base 10 as shown in Fig. 7, and the base 10 is provided with a groove or channel 10A extending from below the follow cut-out portion 8D of the stationary contact 8 to the exterior. Then, arc gas within the arc extinguishing region is exhausted through the hollow portion 8D of the stationary contact 8 and through the channel 10A to the exterior. Therefore, the gas ionized after the generation of the arc is quickly exhausted from the hollow cut-out portion 8D through the channel 10A in the base 10 to the exterior, whereby the arc on the stationary contact element 8A rapidly transfers to the arc runner 8B. Thus, in the electromagnetic contactor shown in Fig. 7, since the arc gas is quickly exhausted, the arc rapidly moves along the arc runner 8B while it is being elongated, and when the current zero point arrives, the charged particles of the arc are quickly scattered, the leg portion of the arc is efficiently cooled, and a superior interrupting capability is provided. Also, since the leg of the arc quickly transfers from the stationary contact element 8A to the arc runner 8B to shorten the time during which the arc remains on the stationary contact element 8A to the arc runner 8B to shorten the time during which the arc remains on the stationary contact element 8A as well as decrease the arcing time, the wear of the stationary contact element 8A can be significantly reduced. The channel 10A may be formed by holes or grooves of various shapes. Further, although the description has been made in terms of the embodiments of the present invention applied to switches in which the contacts are operated by a magnet i.e., electromagnetic contactors, the present invention may equally be applicable to other switches such as circuit breakers.

Claims: A switch which has a stationary contact element (8A) joined on a stationary contact (8) and a movable contact element (6A) joined on a movable contact (6) and disposed in a facing relationship to said stationary contact element, which stationary contact has a cut-out portion (8D) in the vicinity of the portion it which said contact element is joined, and an arc runner (8B) electrically connected to said stationary contact at an edge of said cut-out portion close to said contact element, between the cut-out portion and the contact element, which arc runner extends from the stationary contact towards the movable contact element side and above said cut-out portion, and has an L-shaped cross-section, comprising a vertical leg portion joined to the said stationary contact element and a horizontal leg portion connected to said vertical leg portion and extending above said cut-out portion of the stationary contact, characterised in that a single stationary contact element (8A) is provided, adjacent the vertical leg of the arc runner and directly in line with the arc runner, and a channel (10A) for communicating the cut-out portion (8D) to the exterior space at the lower portion of the cut-out portion is provided in a support member (10) for supporting said stationary contact, for exhausting gas generated during the extinction of an arc generated between said stationary contact and said movable contact to the exterior through said hollow cut-out portion and said channel. A switch as claimed in claim 1, characterized in that said vertical leg portion of the arc runner extends to a position closer to the movable contact element than the contact interface between the stationary contact element and the movable contact element. A switch as claimed in claim 1 or 2, in which the stationary contact carries at one end thereof the stationary contact element and at the other end thereof a connecting terminal, the movable contact extends in a direction away from said connecting terminal, and the said stationary contact has the said cut-out portion between the stationary contact element and the connecting terminal, for causing the direction of current relative to said stationary contact to cross the direction of extension of said stationary contact. A switch as claimed in claim 1, 2, or 3 characterized in that said movable contact extends in the direction opposite to the direction of extension of said stationary contact.

Inventors: MASUDA, SHIGERU MITSUBISHI DENKI KABUSHIKI KAISHA, MORI, TEIJIRO MITSUBISHI DENKI CHUO KENKYUSHO, NISHIZAKO, SHIZUTAKA MITSUBISHI DENKI K. K., OKADO, HIROYUKI MITSUBISHI DENKI KABUSHIKI KAISHA, OTSUKA, SHIGEHARU MITSUBISHI DENKI K. K.
Applicants: MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1983
Main classification: H01H9
IPC codes: H01H9