CIRCUIT BREAKER

Abstract: A circuit interrupter comprising a contact arm rotatably supporting movable members by a movable member pin, wherein a housing side wall has a sloped surface facing to an end surface of the movable member pin, the arrangement being such that a predetermined gap is defined between the end surface of the movable member pin and the housing side wall when the movable members are in the open position, and that a small gap is defined between the end surface of the movable member pin and the housing side wall when the movable members are in the closed position. The housing side wall opposing to the end surface of the movable member pin is provided with a friction reducing member and the end surface of the movable member pin is a sphere-shaped. Also, a tubular bush is provided between the contact arm and a contact arm pin for reducing a play therebetween and preventing the movable members from laterally moving.

Description: TECHNICAL FIELD This invention relates to a circuit interrupter including a plurality of movable members parallel-disposed on a single pole and a flexible conductor connected to each of the movable members. BACKGROUND ART Fig. 5 is a schematical illustration showing a conventional circuit interrupter disclosed in Japanese Patent Laid-Open No. 4-118825 for example. Fig. 6 is a sectional view showing a contact member portion of the circuit interrupter shown in Fig. 5. Fig. 7 is an enlarged sectional view of the main portion taken along line VII - VII of Fig. 6 for illustrating the contact member portion of the circuit interrupter in a closed position. Fig. 8 is a sectional view, similar to Fig. 7, of the contact member portion of the circuit interrupter in an open position. In these figures, 1 is a housing made of a synthetic resin material, 2 are a plurality of stationary conductors disposed in parallel within the housing 1, and 3 are stationary contacts secured to the stationary conductors 2. 4 are movable contacts separating and contacting relative to the stationary contacts 2 in opposition thereto, and 5 are plurality of parallel-disposed (shown in Fig. 7) movable members to which the movable contacts 4 are attached. 6 is a contact arm for rotatably supporting and holding the movable members 5 by a movable member pin 7, and 8 is a contact arm pin for rotatably supporting the contact arm 6 from the housing 1. 9 is a conductor constituting a terminal, 10 is a flexible conductor for connecting the movable member 5 and the conductor 9, 11 is a contact spring, 12 is an operating mechanism portion connected to the contact arm 6 by a pin 13 for operating the movable contacts 4, 14 is a trip relay portion, and 15 is an arc extinguishing device. When an excessive current such as a fault current flows through an electric path of the conventional circuit interrupter and when it is desired that the circuit interrupter achieves an instantaneous interrupting operation, wherein the operating mechanism portion 12 operates to cause the contact 6 to rotate about the contact arm pin 8 to rotate the movable members 5 around the movable member pin 7, thereby separating the movable contacts 4 from the stationary contact 3. The electric arc generated at that time is extinguished by the arc extinguishing device 15. Also, when an excessive current such as a fault current flow through the electric path and when a short time interruption is desired rather than the instantaneous interruption for maintaining the selective co-ordination, the above instantaneous interruption is to be achieved after the prescribed guarantied time interval (maximum holding time of 0.5 seconds). Therefore, within the prescribed short-time period, even when a fault current flows, the circuit interrupter must maintain the closed position and both the contacts 3 and 4 should not melt or weld to each other by the fault current. In the conventional circuit interrupter as above described, since a predetermined gap G1 is defined between the side wall 1a of the housing 1 and the end surfaces 7a of the movable member pin 7 holding the parallel-disposed movable members 5 when the circuit interrupter is in the closed position, the movable members 5 and the movable member pin 7 are moved in the lateral direction as viewed in Fig. 7 by an amount corresponding to the above gap G1 before they initiate the short-time interruption movement from the closed position by a mutual electromagnetic force between the three phase currents flowing through the different pole units. This causes the movable contacts 4 attached to the movable members 5 to move laterally while maintaining the contact states with the stationary contact 3. Therefore, the contacts between them are unstable and arcs can be generated across the movable contacts 4 and the stationary contact 3 before the circuit interrupter initiates the short-time interruption. This invention has been made in order to solve the above-discussed problems and has as its object the provision of a circuit interrupter capable of achieving smooth opening and closing operation without the lateral movement of the contacts even when the short-time overcurrent flows through the circuit interrupter. DISCLOSURE OF THE INVENTION The circuit interrupter of the present invention comprises a housing, a plurality of stationary contacts disposed within the housing, a plurality of movable members each having a movable contact separable from the stationary contact and a contact arm rotatably supporting the movable members by a movable member pin, and is characterized in that the housing has a side wall including a sloped surface facing to a end surface of the movable member pin, the arrangement being such that a predetermined gap is defined between the end surface of the movable member pin and the side wall of the housing when the movable members are in the open position, and that a small gap is defined between the end surface of the movable member pin and the side wall when the movable members are in the closed position. Also, the side wall of the housing opposing to the end surface of the movable member pin may be provided with a friction reducing member. Also, the end surface of the movable member pin may be a sphere-shaped. Also, the contact arm may be rotatably supported by a contact arm pin, and a tubular bush may be provided between the contact arm and the contact arm pin for reducing a play therebetween and preventing the movable members from laterally moving. A circuit interrupter may comprise a housing, a plurality of stationary contacts disposed within the housing, a plurality of movable members each having a movable contact separable from the stationary contact, a contact arm rotatably supporting the movable members, and a contact arm pin for rotatably supporting the contact arm, and a tubular bush may be provided on the contact arm pin for preventing lateral movement. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view showing the contact member portions in the open position of the circuit interrupter of the first embodiment of the present invention; Fig. 2 is a sectional view showing the contact member portions in the closed position of the circuit interrupter shown in Fig. 1 Fig. 3 is a plan view showing the movable contact member of the circuit interrupter of another embodiment; Fig. 4 is a front view showing the movable contact member of the circuit interrupter of the other embodiment; Fig. 5 is a schematic view showing a conventional circuit interrupter; Fig. 6 is a sectional view showing the contact member portion of the conventional circuit interrupter; Fig. 7 is an enlarged sectional view of the main portion and taken along line VII - VII of Fig. 6 with the contact member portion in the closed position; and Fig. 8 is a sectional view showing the contact member portion iin the open position similar to Fig. 7. BEST MODES FOR CARRYING OUT THE INVENTION Figs. 1 and 2 enlarged sectional views of the main portion of the circuit interrupter of the first embodiment of the present invention, Fig. 1 showing the open position and Fig. 2 showing the closed position. In these figures, the reference numerals 1 to 7 depicts the same components as those of the conventional device as above described, so that their explanations are omitted. 1 a are side walls of the housing 1 and has formed therein a tapered surface having a slope for pulling out the mold from the mold die so as to have a dimension L1 on the side of the stationary conductor 2 and a dimension L2 on the side of the movable members 5. These sloped surface is tapered so that a predetermined gap G1 is defined between the movable member pin end surface 7a and the side wall 1 a of the housing 1 when the movable members 5 are in the open position as shown in Fig. 1 and that a gap G2 is defined between the movable member pin end surface 7a and the side wall 1 a of the housing 1 when the movable members 5 are in the closed position as shown in Fig. 2. It is preferable that the gap G1 is equal to or more than 2 mm and gap G2 is 0.05 - 0.5 mm for an air circuit interrupter of from 630 A frame to 6300 A frame, for example. 16 is a friction reducing member or a sliding piece, which is made for example of a phosphor bronze plate, a stainless steel plate, a wear-resisting treated carbon steel plate or the like, attached by bonding, inlaying or the like to the side walls 1a at the portions opposing to the end surfaces 7a of the movable pin 7 when the movable pin 7 is rotated during the opening and closing movement of the movable members 5. Also, the end surfaces 7a of the movable member pin 7 are formed into sphere-shaped in order to minimize the frictional force with respect to the sliding piece 16. In the circuit interrupter arranged as above described, the housing 1 has the side walls 1a each including a sloped surface facing to the end surface 7a of the movable member pin 7, the sloped surface being such that the predetermined gap G1 is defined between the end surface 7a of the movable member pin 7 and the side wall 1a of the housing 1 when the movable members 5 are in the open position, and that the small gap G2 is defined between the end surface 7a of the movable member pin 7 and the side wall 1a of the housing 1 when the movable members 5 are in the closed position, so that, when an excessive current such as a fault current flows through the electrical path in the closed state, the movable members are prevented from moving in the lateral directions, making the contacting relationship stable and no arc is generated across the movable contacts 4 and the stationary contact 3 before the short time interruption operation by the circuit interrupter. Also, when the movable members 5 and the movable member pin 7 are brought into the closed state by the opening and closing operation, the spherical end surfaces 7a disposed at the opposite ends of the movable member pin 7 are moved into the closing direction while maintaining the contact with the sliding pieces 16, the operation being smooth because the contact frictional force are small. When the movable members 5 are in the closed position, the gaps G2 between the end surfaces 7a of the movable member pin 7 and the sliding pieces 16 are very small but allowing the movable members 5 to move, so that even when the electromagnetic forces between the different pole units due to the short time current interact therebetween, the movable members 5 and the movable contacts 4 are allowed to move only by this small gap, eliminating the arcing between the contacts and improving the short time current carrying performance. Also, in recent years where a continuous power supply with the above arrangement is required, the improvements in the short time current carrying capacity which is indispensable to the selective interruption performance can be expected. Also, since the lateral movements of the movable contacts 4 due to the mutually acting electromagnetic forces between the different poles can be prevented, only a required minimum contact pressure for overcoming the electromagnetic repulsive force between the contacts is needed and there is no need to rely on the prevention of the lateral movement by increasing the contact pressure. This means for the operating mechanism portion 12 that the contact pressure which is the largest load during the closing operating can be reduced, improving the operating durability. Figs. 3 and 4 show the movable contact member portion of the circuit interrupter of another embodiment, Fig. 3 being a plan view and Fig. 4 is a front view. In the figures, the reference numerals 4 - 13 depict similar components to those of the conventional device, so that their explanation will be omitted. 17 is a tubular bushing disposed on a contact arm pin 8 which is a rotational center of the rotatable movable members 5 and the flexible conductors 10. The bush 17 is in intimate contact at its inner circumferential surface with the contact arm pin 8 and its opposite end surfaces are in abutment with the side plates 6a of the contact arm 6. Thus, the bush 17 is brought into contact with substantially no play therebetween with the contact arm 6 and a shunt holders 18 which holds and positions the entire movable member portion within the housing 1, so that the movable members 5 and the flexible conductors 10 are allowed to freely rotate about the contact arm pin 8 without any resistance but not allowed to make any translational or rotational movement in the axial direction of the contact arm pin 8 as shown by an arrow Y. Therefore the lateral movements of the movable members 5 and the movable contacts 4 are suppressed. That is, in this embodiment, as different from the first embodiment shown in Figs. 1 and 2, by preventing the lateral movement of the contact arm pin 8 which is the rotational center of the movable members 5 and the flexible conductors 10, the lateral movement of the movable members 5 and the movable contacts 4 due to the mutually acting electromagnetic forces between the poles can be prevented as in the first embodiment, eliminating the arcing between the contacts and improving the short time current carrying performance. Also, this embodiment illustrated in Figs. 3 and 4 in which the bush is disposed between the contact arm pin 8 and the contact arm 6 and the embodiment illustrated in Figs. 1 and 2 in which the gap defined between the side walls of the housing 1 and the movable member pin 7 is made small may be used together in combination or independently. As has been described, according to the circuit interrupter of the present invention, the housing having a side wall including a sloped surface facing to a end surface of the movable member pin, the arrangement being such that a predetermined gap is defined between the end surface of the movable member pin and the side wall of the housing when the movable members are in the open position, and that a small gap is defined between the end surface of the movable member pin and the side wall when the movable members are in the closed position. Therefore, even when an excessive current such as a fault current flows, the movable members are prevented from moving in the lateral directions, making the contacting relationship stable and no arc is generated across the contacts before the short time interruption operation by the circuit interrupter. Also, the operation can be smooth because the contact frictional force is small. Also, even when the electromagnetic forces between the different pole units due to the short time current interact therebetween, the movable members and the movable contacts are allowed to move only by the small gap, eliminating the arcing between the contacts and improving the short time current carrying performance. Also, the side wall of the housing opposing to the end surface of the movable member pin is provided with a friction reducing member or the end surface of the movable member pin is a sphere-shaped, so that the opening and closing movement of the movable members is not influenced. Further, a tubular bush is provided between the contact arm and the contact arm pin for reducing a play therebetween and preventing the movable members from laterally moving, so that the lateral movement of the movable members due to the mutually acting electromagnetic forces between the poles can be prevented, eliminating the arcing between the contacts and improving the short time current carrying performance. APPLICABILITY IN INDUSTRY The circuit interrupter of the present invention, in which the contacting relationship is stable and no arc is generated across the contacts before the short time interruption operation by the circuit interrupter, the operation is smooth, the short time current carrying performance is improved and in which the opening and closing operation durability is improved, can be used as the circuit interrupter for power distribution.

Claims: A circuit interrupter comprising a housing (1), a plurality of stationary contacts (3) disposed within said housing, a plurality of movable members (5) each having a movable contact (4) separable from one of said stationary contacts and a contact arm (6) rotatably supporting said movable members by a movable member pin (7), characterized in that said housing has a side wall (1a) including a sloped surface facing to an end surface (7a) of said movable member pin, the arrangement being such that a predetermined gap (G1) is defined between said end surface of said movable member pin and said side wall of said housing when said movable members are in the open position, and that a small gap (G2) is defined between said end surface of said movable member pin and said side wall when said movable members are in the closed position. A circuit interrupter as claimed in claim 1, wherein said side wall of said housing opposing to said end surface of said movable member pin is provided with a friction reducing member (16). A circuit interrupter as claimed in claim 1 or 2, wherein said end surface of said movable member pin is sphere-shaped. A circuit interrupter as claimed in any one of claims 1 to 3, wherein said contact arm is rotatably supported by a contact arm pin (8), and wherein a tubular bush (17) is provided between said contact arm and said contact arm pin for reducing a play therebetween and preventing said movable members from laterally moving.

Inventors: KAWAKAMI JUNICHI, OKASHITA HIROSHI, KAWAKAMI, JUNICHI, OKASHITA, HIROSHI, KAWAKAMI, Junichi, Mitsubishi Denki KK, OKASHITA, Hiroshi, Mitsubishi Denki KK
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 2000
Main classification: H01H9
IPC codes: H01H1, H01H71, H01H73