Circuit breaker

1. FIELD OF THE INVENTION

The present invention relates to a circuit breaker, and especially to a construction of the circuit breaker having a trip-bar which is driven by a releasing mechanism.

2. DESCRIPTION OF THE RELATED ART

A conventional circuit breaker is described referring to FIG.1 and FIG.2. FIG.1 is a cross-sectional side view of the conventional circuit breaker, and FIG.2 is a cross-sectional front view showing the state of position of a trip-bar on a base of the conventional circuit breaker configuration.

As shown in FIG.1, the conventional circuit breaker comprises a housing 1 which is constituted by a base la and a cover lb, a handle 2 which is for setting the circuit breaker by manual action, a link mechanism 3 which is constituted by link levers 3a, 3b, 3c, 3d, 3e, 3f and other levers not-shown in figures, a movable contact 4 and a fixed contact 5. A trip-bar 6 is held rotatably at its both ends by metal bushes 7 and 7 on the base la of the housing 1, as shown in FIG.2. The trip-bar 6 is made of an insulating material. A planger 8a of a magnet 8 which is an electric magnet of a magnetic tripping mechanism, implicates a fork 6b of the trip-bar 6. An adjusting screw 9a of a bi-metal 9 of a thermal tripping mechanism, touches an arm part 6c of the trip-bar 6.

In such conventional circuit breaker, the movable contact 4 is driven by the action of the handle 2, and contact point 4a of the movable contact 4 and contact point 5a of the fixed contact 5 changes from on to off state, and vice versa. When an overcurrent flows on the circuit of the closed state in FIG.1, the bi-metal 9 is bent by heating, and the arm part 6c of the trip-bar 6 is pushed by the adjusting screw 9a of the bi-metal 9. Accordingly, the movable contact 4 is separated from the fixed contact 5 by rotation of the trip-bar 6 with intermediating the link mechanism 3. On the other hand, when a large current flows on the circuit breaker of the closed state in FIG.1, the plunger 8a of the magnet 8 is attracted and charged, and the fork 6b of the trip-bar 6 is drawn below, so that the movable contact 4 is separated from the fixed contact 5 by rotation of the trip-bar 6, by intermediation by the link mechanism 3.

As mentioned above, in the conventional circuit breaker, the trip-bar 6 is held on the base la, and such trip-bar 6 and base la are respectively plastic mold parts. Accordingly, in case that the accuracy of the trip-bar dimension is poor, there may be a problem of instability in tripping characteristic of the circuit breaker because of the scatterings of the positions of the trip-bnr 6 and the bi-metal 9.

OBJECT AND SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an improved circuit breaker having stable tripping characteristic by precisely setting the positions of a trip-bar and bi-metal.

A circuit breaker in accordance with the present invention comprises:

• a frame having two side plates opposing each other.and disposed on a housing, said side plates having respective holes disposed at each other opposing position,
• a trip-bar which has center through hole disposed at the center lengthwise of the trip-bar and two cuttings disposed at predetermined distance corresponding to the width of the frame, and is rotatably held by the frame, and
• a trip-bar pin which is inserted the center through-hole of the trip-bar and the two holes on the side plates of the frame.

BRIEF DESCRIPTION OF THE DRAWING

• FIG.1 is the cross-sectional side view showing the conventional circuit breaker.
• FIG.2 is the cross-sectional front view showing the position of trip-bar on the base of the conventional circuit breaker.
• FIG.3 is a cross-sectional side view showing a improved circuit breaker in accordance with the present invention.
• FIG.4 is a perspective view showing a frame of the circuit breaker in accordance with the present invention.
• FIG.5 is a perspective view showing a trip-bar and a trip-bar pin of the circuit breaker in accordance with the present invention.
• FIG.6 is a magnified perspective view showing cutting parts of the trip-bar of the circuit breaker in accordance with the present invention.
• FIG.7 is a magnified perspective view showing the trip-bar pin of the circuit breaker in accordance with the present invention.
• FIG.8 is a side view showing the state of pinching the trip-bar pin by a pincher in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of a circuit breaker in accordance with the present invention is described in the following with referrence to FIG.3, FIG.4, FIG.5, FIG.6, FIG.7 and FIG.8.

As shown in FIG.3, the circuit breaker in accordance with the present invention comprises a housing 1 which is constituted by a base la and a cover lb, a handle 2, a link mechanism 3 constituted by link levers 3a, 3b, 3c, 3d and other not-shown levers, a movable contact 4 and a fixed contact 5. A trip-bar 6 is rotatably held by a frame 10, and the frame 10 is fixed on the base la of the housing 1. The frame 10 has two side plates 10a and 10a which opposes each other as shown in FIG.4. Furthermore, two holes 11 and 11 are respectively disposed on both side plates l0a and 10a at each other opposing position. A trip-bar pin 15 is to be inserted throuth these holes 11 and 11. The trip-bar 6 has three arms 6c, three forks 6b and a center through-hole 12 in which the trip-bar pin 15 is to be inserted as shown in FIG.5. And also, two cutting parts 13 and 13 are disposed with a predetermined pitch lengthwise of the trip-bar 6. Such predetermined pitch is selected to correspond to the width of the frame 10, and assembling relation of the trip-bar 6 and the frame 10 is shown by single-dotted chain line 10a and 10a in FIG.5. Between the cutting parts 13 and 13, two pincheing part 14 and 14 are disposed on the trip-bar 6 for pinching the trip-bar pin 15 to fix the latter to the trip-bar 6. The trip-bar 6 is generally made by plastic mold, and the pincher has appropriate elasticity. Top part 15a of the trip-bar pin 15 fits into the bottom part 12a of the center hole 12, and shallow grooves 16 and 16 which are parts of smaller diameter or offset part of the trip-bar pin 15, are pinched by the pinchers 14 and 14.

Setting up is practiced as follows. The trip-bar 6 is placed on the frame 10 making coincidence of the cutting parts 13 and, 13 with the side plates 10a and, 10a, and also making coincidence of the holes 11 and, 11 on the side plates 10a and, 10a with the center through hole 12 of the trip-bar 6. After the setting, the trip-bar pin 15 is inserted into the center hole 12 in the arrow-marked direction in FIG.5. As a result, the trip-bar pin 15 is rotatably'supported by the holes 11 and 11 on both side plates 10a and 10a, and the trip-bar 6 is fixed on the trip-bar pin 15 as shown in FIG.3. Accordingly, the trip-bar 6 can be rotated around the hole 11 on the side plate 10a of the frame 10.

In above-mentioned embodiment, since the trip-bar 6 pinches the trip-bar pin 15 by pincher 14a of the pinching part 14, sufficient strength of fixing the trip-bar 6 and the trip-bar pin 15 is obtainable, and the trip-bar 6 does not become loose in supporting the frame 10. Furthermore, by fitting the grooves 16 and 16 into the pinchers 14a and 14a, looseness of relative axialposition between the trip-bar 6 and the trip-bar pin 15 can be minimized, and a high prevision positioning of the trip-bar 6 of the circuit breaker is achievable.

FIG.8 shows an other embodiment, wherein projections 17 and 17 of pinching surfaces of the both pinchers 14a and 14a shown in FIG.8 can prevent slipping off of the trip-bar pin 15 from the trip-bar 6, and the fixing strength of the trip-bar 6 and the trip-bar pin 15 can be increased.

In case that the holes 11 of the frame ]0 is manufactured by metal presswork, the holes 11 are precisely positioned on the frame 10. As a result, leaning of the trip-bar 6 against the frame 10 can be substantically eliminated, Though in the above-mentioned embodiments the trip-bar 6 has the pinchers 14a and the trip-bar pin 15 has the grooves 16, these pinchers 14a and grooves 16 are not always necessary.