| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a circuit breaker having high dust preventing performance and capable of obtaining a sufficient quantity of discharge air when arc is generated. Ž<P>SOLUTION: This circuit breaker comprises a case 1 housing a pair of terminal parts; a fixed terminal plate 2 having a fixed contact point 2a; a movable contact 3 having a movable contact point 3a; a cross bar 33, to which the movable contact 3 is fitted to be turned together; and an over-current shut-off means 5 for forcibly separating between the contact points when over-current flows; inside thereof, a discharge plate 6 provided in an opening formed in the case 1 to cover the opening and formed with a discharge hole 6a for discharging gas of the arc, which is generated when the movable contact point 3a separates from the fixed contact point 2a, out of the case 1, and a dust preventing plate 7 to be bent by the gas pressure of the arc to open the discharge hole 6a. The dust preventing plate 7 comprises a fitting part 7b for fitting the dust preventing plate to the case 1 or the discharge plate 6, and a slit 7a is formed between an area facing the discharge hole 6a and the fitting part 7b. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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