Circuit breaker

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.

First, a conventional circuit breaker is described in general 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 1a and a cover 1b, a handle 2 which is for setting the circuit breaker by manual action, a link mechanism 3 which is constituted by a number of link levers, 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 1a of the housing 1, as shown in FIG. 2. The trip-bar 6 is made of an insulating material. A plunger 8a of a magnet 8 which is an electromagnet of a magnetic tripping mechanism, pulls down 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 downward, 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 1a, and such trip-bar 6 and base 1a 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-bar 6 and the bi-metal 9.

US-A-2,689,287 shows an overload relay unit being capable of switching a plurality, e. g. three, power lines by using a single trigger means acting on all three power lines. Said trigger means is comprised of a so-called rocker element of a bar configuration, said rocker element being pivotally hinged between two side frames of the relay unit. The hinge itself is constituted by two pins protruding from the end faces of the bar-like rocker element such that they are held in corresponding recesses of the side frames. The two pins in turn are constituted by a single pivot pin extending lengthwise through the bar-like rocker element such that the free ends of the pivot pin protrude from the rocker element's end faces, thus constituting the two pins. The single pivot pin is held within the rocker element by embedding it into the rocker element's material upon e. g. molding same from plastic material.

US-A-3,422,381 shows a multi-pole circuit breaker according to the pre-characterizing part of claim 1. This known circuit breaker also comprises a single trigger element being comprised of a bar-like member which is rotatably supported between two side frames of the circuit breaker. The rotatable support is achieved by two pivot-pin parts being integrally formed on the two end faces of the bar-like member, said pivot-pin parts are held in suitable brackets of the side frames.

Both US-A-2,689,287 and US-A-3,422,381 show the drawback that - as in case of the general circuit breaker according to FIGs. 1 and 2 - there is the risk of inaccuracy upon fabricating the bar-like member together with its hinging parts at the end faces, either by embedding a pivot pin in or by forming pivot pins integrally with the bar-like member. Thus, tripping characteristics of this known circuit breakers may be poor. In addition, upon exchange or replacement, respectively, of a bar-like member upon e. g. wear or the like, always the bar-like member plus its related pivot or hinge means must be replaced, this being a drawback from an economical point of view. Finally, assembly and disassembly or vice versa, respectively, of the circuit breakers described above is a rather troublesome job.

Accordingly, it is an object of the present invention to provide a circuit breaker which is easy to manufacture and to assemble, but has simultaneously a high degree of operating accuracy and reliability.

Solution of this object is achieved by what is featured in claim 1.

The subclaims contain advantageous modifications of the invention.

The following is a detailed description of embodiments of the present invention, taken in conjunction with the accompanying drawings, in which:

• FIG.1 is a cross-sectional side view showing the conventional circuit breaker;
• FIG.2 is a cross-sectional front view showing the position of the 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; and
• FIG.8 is a side view showing the state of pinching the trip-bar pin by a pincher in accordance with the present invention.

A preferred embodiment of a circuit breaker in accordance with the present invention is described in the following with referrence to FIGs. 3 to 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 1a and a cover 1b, a handle 2, a link mechanism 3 constituted by a number of link 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 1a of the housing 1. The frame 10 has two side plates 10a and 10a which oppose each other as shown in FIG.4. Furthermore, two holes 11 and 11 are respectively disposed on both side plates 10a 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 pinching parts 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 parts of the trip-bar pin 15, are pinched by the pinching parts 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 the above-mentioned embodiment, since the trip-bar 6 pinches the trip-bar pin 15 by pinchers 14a and 14a of the pinching parts 14 and 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 axial position 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 10 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 substantially eliminated. Though in the above-mentioned embodiments the trip-bar 6 has the pinchers 14a and 14a and the trip-bar pin 15 has the grooves 16, these pinchers 14a and 14a and grooves 16 are not always necessary.