Apparatus for electrically operating a circit breaker

Abstract: An apparatus for electrically operating a circuit breaker com­ prises an electrically powered pawl (25), which is driven by an electric motor for causing a ratchet (5) to rotate, and a release mechanism (26, 30) for causing the electrically powered pawl (25) to move out of engagement with the ratchet (5) when the ratchet rotates to a predetermined angle. A guide bar (14) on which a spring (16) is mounted is secured on a main frame (3). A slider (12) is slidably provided on the guide bar, which slider engages with a handle (2) of the circuit breaker (1) and switches the circuit breaker when it slides on the guide bar, being driven into slide motion by a cam (11) which rotates with the ratchet gear (5) in a unitary motion. The slider com­ presses the spring on the guide bar. When the slider reaches a position where the circuit breaker switches 0FF, the release mechanism (26, 30) causes the electrically powered pawl (25) to move out of engagement with the ratchet (5).

Description: This invention relates to an apparatus for electrically operating a circuit breaker in which a spring is compressed by means of a rotating motor and a mechanical energy stored within the spring is released to shut off the circuit breaker. One of such apparatuses according to an internal, not public prior art in-house model for electrically operating a circuit breaker is arranged as shown in Fig. 7 to Fig. 10. The OFF-operation of this apparatus to open the circuit will be described with reference to Fig. 7 to Fig 10. A frame 3 of this apparatus is secured in front of a circuit breaker 1. An electric motor 4 is secured on the frame 3 and the rotation of the motor 4 is transmitted to a main shaft 6 which drives a ratchet gear 5 via a reduction gear 8. The main shaft 6 is connected to the motor via a one way clutch 7. The ratchet gear 5 is provided with a cam 11, which rotates together with the ratchet 5 in a unitary motion. The cam 11 engages with a roller 17 journaled for free rotation on a side wall 12b of a slider 12 for causing the slider 12 to slide. A guide rod 14 is secured to the frame 3. The guide rod 14 extends through a rod insertion hole 15 provided on a front wall 12a of the slider 12. Thus the slider 12 is guided by the guide rod 14 to slide thereon. A spring 16 is attached to the guide rod 14. The slider 12 is provided with two handle drive pins 13 to drive a handle 2 of the circuit breaker 1. When an OFF signal is supplied, the motor 4 drives the main shaft 6 in rotation via the reduction gear 8 and the one way clutch 7, thereby causing the ratchet gear 5 to rotate in a direction of an arrow A in Fig. 7. The cam 11 also rotates with the ratchet gear 5 in the direction A, then moves into contact engagement with the roller 17 for causing the slider 12 to slide in a direction of an arrow B. At this time the front wall 12a of the slider 12 compresses the spring 16 as shown in Fig. 8, while also throwing the handle 2 into OFF-position of the circuit breaker 1 by means of the handle drive pins 13. A stop lever 19 is swingably mounted on the side wall 12b of the slider 12. The side wall 12b is provided with a guide and stopper pin 23 to engage with an elongate hole of the stop lever 19. The stop lever 19 is urged against the side wall 12b by means of a twist spring 20 as shown in Fig. 10. The stopper pin 21 of the cam 11 engages with a bent portion of the stop lever 19 for causing the stop lever 19 to swing against the twist spring 20. Moving in the direction B, the slider 12 takes up a position where the circuit breaker 1 becomes OFF to open the circuit and then the stop lever 19 engages with an actuating lever of a limit switch 18. When the ratchet gear 5 further rotates, the cam 11 causes the stop lever 19 to swing in a direction of an arrow C against the twist spring 20. In this manner, the stop lever 19 actuates the limit switch 18 to stop the motor 4. The stopper pin 23 terminates swinging motion of the stop lever 19 as shown in Fig. 9, thereby preventing overrun of the cam 11 is prevented. The slider 12 is held by a latch mechanism 22 at a position shown in Fig. 9. The latch mechanism 22 is to hold both the slider 12 and the spring 16 at a position at which the spring 16 is urged. The latch mechanism 22 is arranged by a link 22a of the slider 12 and a latch (not shown) of the frame 3. Additionally the ratchet gear 5 is provided with a fixed pawl 33 to prevent reverse rotation thereof. In Fig. 10, operating a manual operation handle 9 in a pumping fashion permits rotation of the ratchet 5 in the direction A in Fig. 7 thus the off-operation of the circuit breaker can also be effected in a manner similar to the case operated by the motor 4. In the manual mode, the motor 4 is disconnected with the aid of the one way clutch 7. The ON-operation (the circuit will be closed) of this conventional apparatus to open the circuit will now be described with reference to Fig. 9 which shows OFF state of the circuit breaker. When the latch 22 is actuated upon ON signal, the slider 12 is set free from being latched and the stored mechanical energy of the compressed spring 16 is released. The slider is then pushed out by the spring 16 to slide in a direction of an arrow D while at the same time the stop lever 19 moves in the direction D, during which the slider 12 throws the handle 2 into ON position by means of the handle drive pins 13 as shown in Fig. 7. With the conventional apparatus for electrically operating a circuit breaker thus far described, it is necessary to stop the motion of the cam 11 at a specific location so that the cam 11 and the roller 17 are positioned within a predetermined area after the OFF-operation is completed. For this purpose, a special type of brake such as reverse rotation was applied to bring the motor 4 to a stop, or mechanical strength of the bent portion which serves to stop the further swing motion of the stop lever 19 was increased, thereby preventing overrun of the cam 11 due to inertial rotation of the electric motor 4. Also in the case of malfunction of a limit switch 18 which operatively engages with the cam 11 to switch off the motor 4, there have been shortcomings in which the stopper portion of the cam 11 is damaged or the motor 4 burns out due to overload. SUMMARY OF THE INVENTION The present invention was made to solve the problems described above. An object of the invention is to provide an apparatus for electrically operating a circuit breaker in which an electric motor needs no special braking devices to set the circuit breaker to OFF-state thereof. Another object of the invention is to provide an apparatus for electrically operating a circuit breaker which can prevent burning of the electric motor, which tends to continue rotating against braking force of a stopper when a switch for closing and opening the motor circuit malfunctions. Still another object of the invention is to provide an apparatus for electrically operating a circuit breaker which eliminates influence of overrun of the motor due to inertial rotation after it is switched off, thereby preventing damage to the stopper portion. These objects are met by the invention as set out in claim 1. BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objects and advantages will be better understood from the following description with reference to the accompanying drawings, in which: Fig. 1 is a top view depicting the inside of an apparatus according to the invention: Fig. 2 is a cross sectional view taken along the line II-II of Fig. 1; Fig. 3 is a cross sectional view in part taken along the line III-III of Fig. 1; Fig. 4 is a diagram similar to Fig. 3 for illustrating a spring which is being compressed; Fig. 5 is a diagram similar to Fig. 3 for illustrating the spring which has been compressed; Fig. 6 is a diagram similar to Fig. 3 for illustrating the spring which has been compressed; Fig. 7 is a side view of a conventional apparatus for showing the spring which has been released compressive mechanical energy thereof completely; Fig. 8 is a side view of the conventional apparatus, showing the spring which is being compressed; Fig. 9 is another side view of the coventional apparatus for showing the spring which has been compressed completely; Fig. 10 is a general top view of Fig. 9. In these Figures, like elements have been given like numerals; and Fig. 11 shows a latch mechanism in OFF state of the circuit breaker, and Fig. 11b shows a latch mechanism in ON state of the breaker. DESCRIPTION OF THE PREFERRED EMBODIMENTS The OFF-operation (the circuit will be open ) of an apparatus for electrically operating a circuit breaker according to the invention will now be described with reference to Figs. 1 to 3. A main frame 3 of the apparatus is attached in front of a circuit breaker 1. On the frame 3 provided are an electric motor 4 and an electrically powered pawl. This electrically powered pawl 25 is rotatably supported by an eccentric shaft 25a and is connected to the electric motor 4 via a reduction gear 8. The tip end of the pawl 25 is always urged toward the ratchet gear 5 by means of a spring. A first release plate 26 is swingably supported on the frame 3 by means of a first pivot pin 27. The first release plate 26 has a release strip 29 formed integrally therewith. Similarly a second release plate 30 is swingably supported on the frame 3 by means of a second pivot pin 31. An elongate hole 30a at one side of the second release plate 30 is linked to a pin 26 of the first release plate 26. A cam 11 is attached to a ratchet gear 5 and rotates with the ratchet 5 in a unitary motion. The ratchet gear 5 is prevented from reverse rotation by means of a fixed pawl 33 which is urged by a spring (not shown) against the ratchet 5. The cam engages with a roller 17 which is journaled at a side wall 12b of the slider 12 to slide the slider 12. A guide rod 14 is secured to the frame 3 and extends through a rod insertion hole 15 provided on a side wall 12a of the slider 12. Thus the slider 12 is guided by the guide rod 14 to slide. A spring 16 is attached to the guide rod 14. The electric motor 4, when started upon an OFF-operation signal, drives the eccentric shaft 25a via a reduction 8 in eccentric motion about an axis P for causing the ratchet 5 to rotate in a direction of an arrow A. The cam 11 rotates with the ratchet 5 in the direction A, and then engages with the roller 17 for causing the slider 12 to slide in the direction of B, during which the slider 12 urges the spring 16 as shown in Fig. 5 while also throwing a handle 2 to an OFF-position by means of handle drive pins 13. A stop lever pin 21 of the cam 11 engages with a stop lever 19 for causing the the stop lever 19 to swing further against a twist spring 20, thereby the release pin 28 of the first release plate 26 actuating a limit switch 18 to bring the motor to a stop. Fig. 5 shows that the circuit breaker 1 is in OFF state thereof. A stopper pin 23 is provided on a side wall 12b of the slider 12. The stopper pin 23 is in insertion engagement with an elongate hole of the stop lever 19 to stop swing motion of the stop lever 19. Simultaneously, the second release plate 30 is driven by pivotal motion of the first release plate 26 which is caused by movement of the release pin 28. The second release plate 30 then swings about a pin 31 to push the electrically powered pawl 25 at a pin thereof to be out of driven engagement with the ratchet gear 5. That is, the circuit breaker 1 becomes off with spring 16 being urged fully as shown in Fig. 5. When the cam 11 takes up a predetermined position, the limit switch 18 switches the electric circuit of the motor 4 while at the same time the electrically powered pawl 25 is released out of mechanical engagement with the ratchet 5, thereby preventing overrun of the cam 11 due to inertial rotation of the electric motor 4. Also with the spring being biased as shown in Fig. 5 and Fig. 6, a manual pawl 10 (Fig. 10) is pushed at a pin thereof by the release strip 29 to be out of driven engagement with the ratchet 5; therefore an operator cannot feel any resistance even if he operates a manual operation lever by means of a manual operation hadle 9 connected to the manual operation lever, thus confirming that the spring is certainly biased. A latch mechanism 22 is to maintain both slider 12 and the spring 16 at a position at which the spring 16 is urged fully and is formed of a link 22a of the slider 12 and a latch 22b on the frame 3 as shown in Fig. 11a and Fig. 11b. Fig. 11a shows the latch mechanism 22 when the circuit breaker 1 is in OFF state. The ON-operation of a circuit breaker which is performed by the apparatus according to the invention will now be described with reference to Fig. 5, Fig. 6 and Fig. 11 as follows. Fig. 11a shows the latch mechanism when the circuit breaker 1 is in OFF state. The link 22a, a spring 50, the latch 22b, and repulsive force of the spring 16 are in equilibrium. When a solenoid 32 is energized upon an ON operation signal to kick the latch 22b in a direction of K, the latch 22b rotates momentarily about pin 54, which supports the latch 22b rotatably on the frame 3, in a direction of E to move out of depressive engagement with the roller 51, thereby disabling latching. The latch mechanism 22 releases the slider 12 and the stored compressive spring energy of the spring 16 is dicharged to slide the slider 12 in the direction D. The stop lever 19 also moves in the direction D at the same time. At this time the slider 12 throws the handle 2 into the ON position by means of handle drive pins 13 as shown in Fig. 2. Fig. 11b shows the latch mechanism when the circuit breaker 1 is in ON state. In addition, operating the manual operation handle 9 in a pumping fashion can cause rotation of the ratchet 5 in the direction A in Fig. 2 thus the OFF-operation of the circuit breaker can also be effected in a manner similar to the case operated by the motor 4. When the stop lever 19 moves in the direction D in Fig. 5, the release pin 28 will be out of engagement with the limit switch 18 causing the first release plate 26, the second release plate 30 and a release strip 29 to return to their initial positions. Thus the electrically powered pawl 25 will again slip into mesh engagement with the ratchet 5 as shown in Fig. 3, while at the same time the limit switch 18 returns to its initial state. In the embodiment thus far described, the first and the second release plates 26 and 30 may be urged by a spring or a similar urging member so that they are maintained in a mechanical positional relation as shown in Fig. 3 for a stable operation.

Claims: An apparatus for electrically operating a circuit breaker (1) which closes a circuit when an ON operation signal is supplied thereto and opens the circuit when an OFF operation signal is supplied, comprising: a ratchet gear (5) having a cam (11) thereon, said cam (11) rotating with said ratchet gear (5) in a unitary motion; an electric motor (4) mechanically coupled to said ratchet gear (5) for driving said ratchet gear (5) into rotation when said OFF operation signal is supplied; and a limit switch (18) operated through a pivotally supported stop lever (19) driven by rotation of said cam (11) for switching off said electric motor (4) when said cam (11) rotates to a predetermined position; characterized by a pawl (25) driven by said electric motor (4) for driving said ratchet gear (5) into rotation; and a release mechanism (26, 30) driven into pivotal motion by rotation of said cam (11) for causing said pawl (25) to move out of engagement with said ratchet gear (5) when said cam (11) rotates to said predetermined position. The apparatus for electrically operating a circuit breaker (1) according to claim 1, wherein said release mechanism comprises: a first release plate (26) swingably provided on a frame (3); and a second release plate (30) swingably provided on said frame (3); wherein said first release plate (26) and said second release plate (30) are connected through a link in which an elongated hole (30a) on one release plate (30) engages with a pin (26a) on the other release plate (26), the second release plate (30) causing said electrically powered pawl (25) to move out of engagement with said ratchet gear (5) when said first release plate (26) is driven by said cam (11).

Inventors: IKEHATA YOJI MITSUBISHI DENKI, ONODA TADAYOSHI MITSUBISHI DEN, IKEHATA, YOJI MITSUBISHI DENKI KABUSHIKI KAISHA, ONODA, TADAYOSHI MITSUBISHI DENKI KABUSHIKI KAISHA
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1988
Main classification: H01H3
IPC codes: H01H33, H01H3, H01H71