US2662136A - High speed trip device for electric circuit breakers - Google Patents

Description

1953 MASATOSHI KUWAYAMA 2,662,136

HIGH SPEED TRIP DEVICE FOR ELECTRIC CIRCUIT BREAKERS Filed March 14, 1951 INVENTOR fins/970s, 111w yam;

BY W, M I; fimsA rs Patented Dec. 8, 1953 HIGH SPEED TRIP DEVICE FOR ELECTRIC CIRCUIT BREAKERS Masatoshi Kuwayama, Taga, Japan, assignor to Hitachi Limited, Chiyoda-Ku, .Tokyo, Japan Application March 14, 1951, Serial No. 215,505

3' Claims.

This invention relates to an improvement in a high speed tripping device for electric circuit breakers.

It has heretofore been known in electric circuit breakers that the circuit should be cut-off as quickly as possible in order to prevent the arcover between the contacts and to avoid damages of elements. For this purpose, various quick tripping devices have been proposed, but most of known devices cons sts merely of a combination and special arrangement of a number of levers and link mechanisms so that they are complicated in construction and heavy in operation owing to frictions between many working parts.

In accordance with the present invention, the above mentioned defects are overcome by us ng a pair of cooperating rollers between the tripping elements and by adequately selecting the slope of the working surface of the tripping lever For a better understanding of my invention,

reference is taken to the accompanying drawing, in which,

Fig. 1 is an elevation showing an arrangement of rollers and cooperating elements taken for the explanation of the principle of operation of the high speed tripping device of this invention,

Fig. 2 is an elevation showing a construction and arrangement of the present device when the, circuit breaker is closed,

Fig. 3 is a view similar to Fig. 2 when the circuit breaker is opened,

Fig. 4- is a side view of the roller supporting mechanism, and

Fig. 5 15a partial elevation showing a construction of heretofore ordinary tripping device.

Now referring to Fig. 1, which shows the principle of the tripping mechanism of this invention, R represents a pair of tripping. rollers; A and B designate inclined plates acting on the rollers, and S- is a strip. placed between the rollers. If an external force P isv applied to either one or both of the inclined plates A and B in the direction of P, the rollers R will be turned in the direction as shown by the arrows a, thereby the strip 8 is forced out in the direction of the arrow I) and as the result the rollers are shifted by rolling in the same direction as the movement or the strip. If the external forces P are the same, the shifting force Q acting on the strip S through the rolling motion of the rollers will be proportional to sine 0 when the angle 0 between the inclined plates A and B is small. Owing to the fact that the operation between members of the mechanism consists entirely of the rolling friction, it is possible to reduce the value of sine 0 to less than ,5 If the strip S is held stationary by some means, the coefficient of friction between the strip and the rollers may be assumed much greater than the value of sine 0 so that the rollers R can be prevented from rolling in the directions of the arrows at and be held stationary against the external forces P.

The principle of the roller mechanism is utiliaed for the tr pping device of electric circuit breakers according to this invention. Figs. 2 to 4 illustrate a preferred construction and arrangement embodying this invention. Referring to these figures, i represents a link connected to an operating member of a circuit breaker (not shown), which is normally forced in the direction of W by the bias of opening force when the circuit breaker is in the closed condition. 2 is 'a movable latch member or latch lever pivoted at one end and connected at its middle to the link i, the free end of the lever 2 forming an inclined surface A which engages on the tripping roller R. 3' represents a frame work for supporting the rollers R, the axis 4 of each roller engaging in aguide groove 1 of the frame 3 and being held by a spring 6 which is stretched between the lug pin 5 and the roller axis The frame 3 is fixed to the base plate 8. S is an adjustable stopper pivoted at one end and fixed at the other end to the base frame 8 by means of adjusting screws l0 and H. The stopper 9 is provided with an inclined surface B acting against one of the rollers R and the inclination of the surface may be adjusted by the screws l0 and H.

[2 represents a stationary core of a tripping electromagnet; I3 is its magnetic bridge; it is a holding coil; 95 is a trip coil wound around the magnetic bridge IS, and it represents a movable iron piece which is-connected with the strip S at its upper end and engages at the lower edge with the corresponding edge F of a non-magnetic element It whichis fixed to the core it. it represents a tension spring acting to pull up the movable iron piece it. The line X-X illustrates the locus of movements of the free end of the latch lever 2.

Fig. 2 shows the position of operating memhers of the present device when the circuit break- .-.1' ii a closed condition, wherein the holdco the trip magnet is energ zed so that the rnov-.. -e piece 58 may be pulled by means flux 1 passing through the iron piece ii to fix the strip S, thereby preventing the rollmovement of the rollers B so that the turnof the latch lever in the direction of W can be prevented.

Now if the trip coil i5 01 the electro-magnet is energized, the link I is shifted from the path of the iron piece it toward the magnetic bridge 53 and releases the iron piece lfi.

the result, the strip S can no more prevent the bias of turning of the rollers B, and the latter are shifted downwards by rolling in accordance with the operating force of the latch lever 2 and the strip '55 located between the rollers will be shifted downwards at a speed twice that oi the rollers. Thus the lever 22 interlocked by means of the rollers is released and the circuit breaker is allowed for circuit opening operation. After the completion oi the above operation the mow able iron. piece [5 is pulled up by the spring I8 and meanwhile the rollers R are pulled up by the spring ii, thus all parts are re-set to the positions as shown in Fig. 2. In re-closing the circult breaker, the latch lever 2 forces down the rollers R by its free end and moves to the interlocking position shown in 2 and is re-set to that position by the rollers.

5 represents an example of heretofore usual trip ing mechanism taken for the comparison with this invention, wherein 2| designates a link pivoted at 22; 23 is bell-crank lever pivoted at M, and 25 is an iron piece pivoted at 25 serving the tripping iron core of a tripping electr0-magnet 7!? having a trip coil 28. In such a mechanism, the movement of the latch lever 2 in the direction of W is prevented by a roller R put on the top of the lever 2 I, which engages one end of the bellcrank lever 23, the other end of the later being engaged with the iron core 25. Owing to a number of pivots, levers and links and multi-stage operations, there occurs frictional resistances between co-operating members in each stage. In order to avoid the uncertainty of operation, it is necessary to selectthe smaller reduction ratio one stage so that a longer time is required for the effective tripping operation with. such multi-stage mechanism due to the increased time. Thus it is actually difficult to att the object of h' h speed tripping operation for C uit breaker of a large capacity.

On the other hand, according to the tripping device this invention there is no part causing a large frictional resistance except a small roiling friction and it is possible to establish a high reduction ratio of one stage such as to & Moreover the operating parts can be made very li ht since there is no intermediate members such as fixed pivotal and link levers and the like. According to the results of comparative tests efiected with the heretofore trip mechanism and the present device or this invention adopted for a circuit breaker of 161 K. V., the former required more than 0.02 second for the starting of latch lever after the movable core has started, while the latter showed it required only 0.002 second. Another advantage of the present device is that there occurs absolutely no slip between the cooperating members since the coefficient of friction between the strip S and the rollers R is much greater than the coefilcient oi slope between the surfaces A and )3.

Further advantage of the present device is that the weight of working parts and the friction between them can be reduced to the minimum, thereby effecting a desired high speed tripping operation.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. A high speed trip device for electric circuit breakers, comprising a pair of cooperating rollers having their axes in parallel spaced relation, opposed inclined surface members biasing said rollers to roll in opposite directions, at least one of said members being a latch lever of the circuit breaker, a strip contiguous between said pair of rollers and connected with a movable armature of a tripping electro-magnet, said armature acting to prevent the bias of said rollers from operating said latch lever, and said armature operable upon energization of said tripping elect1'o magnet to allow one of said rollers to move from restraining engagement with said latch lever, whereby the circuit breaker is allowed to operate.

2. A trip device according to claim 1, including means for adjusting the angle of inclination of the inclined surface of the other of said members.

3. A high speed trip device for electric circuit breakers, comprising a latch lever of the circuit breaker pivotally supported to be movable between a first latched position and a second unlatched position, a pair of cooperating rollers having their axes parallel spaced relation and being free to rotate in opposite directions, a fixed base plate having upstanding parallel frames extended normal to the axes of said rollers and ovided with parallel spaced guide slots matching the spacing of said rollers, said rollers being freely rotatively and slidably supported in said guide slots, said latch lever having an inclined surface engaging one of said rollers, springs operating between said rollers and said frames biasing said rollers to an extreme position in slots in which said latch lever is in its first latched position, a stopper mounted on said base plate and having an inclined surface engaging the other of said rollers, a strip contiguous between said pair of rollers and connected with a movable armature of a tripping electro-magnet, said armature acting to prevent the bias of said rollers from operating said latch lever, and said armature operable upon energization of said tripping electro-magnet to allow one of said rollers to move from restraining engagement with said latch lever, whereby the circuit breaker is allowed to operate by freeing the latch lever to move to its second unlatched position.

MASATOSHI KUWAYAMA.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,510, i Henry Sept. 30, 1924 1,799,985 McCoy Apr. 7, 1931 1,815,637 Viele July 21, 1931 1,953,789 Thumim Apr. 3, 1934

Images