Circuit breaker

Abstract: A circuit breaker includes: a casing having a base and a main cover secured to the base, the casing accommodating a circuit breaking mechanism; a recesses formed in one surface of the main cover, the opposite surface of which is on the side of the base, the recess being adapted to receive an auxiliary device of the circuit breaking mechanism; and an auxiliary cover mounted on the main cover in such a manner as to close the recess. The circuit breaker is automatically tripped when the auxiliary cover is opened, thus permitting installation of the auxiliary device thereon with high security.

Description: BACKGROUND OF THE INVENTION This invention relates to a circuit breaker with auxiliary devices such as a warning switch and an auxiliary switch. A conventional circuit breaker as it is known from doc. US-A-4 754 247 will be described with reference to FIGS. 21 through 27. FIG. 21 is a perspective view showing the external appearance of the conventional circuit breaker. FIG. 22 is an exploded perspective view of the circuit breaker. FIG. 23 is a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "on" state. FIG. 24 is also a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "off" state. FIG. 25 is a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "trip" state. FIG. 26 is a sectional view taken along line 26-26 in FIG. 22, showing an auxiliary cover. FIG. 27 is a perspective bottom view of the auxiliary cover. In those figures, reference numeral 1 designates a circuit breaker casing comprising a base la, and a main cover 1b which is detachably secured to the base la; 2, an auxiliary device such as a warning switch and an auxiliary switch; 3, a recess formed in one surface of the main cover 1b which is opposite to the other surface which is on the side of the base la, for receiving the auxiliary device 2; 5, a movable piece which is swingably mounted inside the circuit breaker casing 1, having a movable contact 5a; and 6, a stationary piece with a stationary contact 6a which is brought into and out of engagement with the movable contact 5a; 7, a handle which is pushed back and forth to swing the movable piece 5 with the aid of a toggle link mechanism 8. The handle 7 comprises: a arcuate base 7a which is moved along the inner surface of the main cover 1b, and an operating protrusion 7b which is extended outwardly from the arcuate base 7a through an opening of the main cover 1b. Further in those figures, reference numeral 9 designates a lever operated in association with the toggle link mechanism 8; 10, a trip cover coupled to the lever 9 through an engaging metal part 11 and a latch 12; and 13, a tripping mechanism (of bimetal type or electromagnetic type) which is connected to a terminal board 14 on the side of load and connected through a flexible stranded wire 15 to the movable piece 5. The operation of the conventional circuit breaker thus constructed will be described. It is assumed that the circuit breaker is held turned on. When, under this condition, the handle 7 is moved in the direction of the arrow 16, the toggle link mechanism 8 is bent, whereby the movable piece 5 is raised. As a result, the circuit breaker is turned off as shown in FIG. 24. When, under this condition, the handle 7 is moved in the direction of the arrow 17 as shown in FIG. 24, the toggle link mechanism 8 is stretched, whereby the movable piece 5 is depressed. As a result, the circuit breaker is turned on as shown in FIG. 23. When over-current flows in the circuit breaker in "on" state as shown in FIG. 23, the tripping mechanism 13 is operated to turn the trip bar 10 in the direction of the arrow 18, so that the engaging metal part 11 and the latch 12 are disengaged, and the lever 9 is elastically raised. As a result, the toggle link mechanism 8 is bent to raise the movable piece 5. Thus, the circuit breaker is placed in "trip" state as shown in FIG. 25. The conventional circuit breaker designed as described above suffers from the following difficulty: Installation of the auxiliary device 2 in the recess 3 with the auxiliary cover 4 removed as shown in FIG. 22 may be hazardous, because when the circuit breaker is in "on" state as shown in FIG. 23, the line connected to it is hot, and it may be tripped unintentionally. Circuit breakers equipped with opening preventing devices are known in the art; doc. EP-A-0 358 482 discloses a circuit breaker with a means for preventing opening of the main cover while the circuit remains in an ON state. SUMMARY OF THE INVENTION Accordingly, an object of this invention is to provide a circuit breaker high in reliability on which an auxiliary device can be installed with high security. The foregoing object of the invention has been achieved by the provision of a circuit breaker which is so designed that, when the circuit breaker is in "on" state, opening its auxiliary cover is inhibited. According to a first aspect of the invention, the circuit breaker is so designed that it is placed in "trip" state when the auxiliary cover is opened. According to a second aspect of the invention, in the circuit breaker, opening the auxiliary cover is inhibited when the circuit breaker is in "on" state. BRIEF DESCRIPTION OF THE DRAWING(S) FIG. 1 is a perspective view showing the external appearance of a first embodiment of this invention. FIG. 2 is a perspective view showing the first embodiment with its auxiliary cover opened. FIG. 3 is a sectional view taken along line 3-3 in FIG. 1. FIG. 4 is a sectional view showing a second embodiment of the invention. FIG. 5 is a sectional view showing a third embodiment of the invention. FIG. 6 is a perspective view of an auxiliary cover of the third embodiment. FIG. 7 is a sectional view showing a fourth embodiment of the invention which is in "on" state. FIG. 8 is a sectional view showing an auxiliary cover of the fourth embodiment. FIG. 9 is a perspective bottom view of the auxiliary cover shown in FIG. 8. FIG. 10 is an exploded perspective view showing a fifth embodiment of the invention with its auxiliary cover removed. FIG. 11 is a sectional view of the auxiliary cover of the fifth embodiment. FIG. 12 is a perspective view showing a handle of the fifth embodiment. FIG. 13 is a sectional view showing a sixth embodiment of the invention which is in "off" state. FIG. 14 is a sectional view showing a seventh embodiment of the invention which is in "on" state. FIG. 15 is a sectional view of an auxiliary cover of the seventh embodiment. FIG. 16 is a perspective bottom view of the auxiliary cover shown in FIG. 15. FIG. 17 is a sectional view of an eighth embodiment of the invention which is in "on" state. FIG. 18 is a sectional view of the eighth embodiment which is in "off" state. FIG. 19 is a sectional view of a ninth embodiment of the invention which is in "trip" state. FIG. 20 is a perspective view of the ninth embodiment with its auxiliary cover removed. FIG. 21 is a perspective view showing the external appearance of a conventional circuit breaker. FIG. 22 is an exploded perspective view of the conventional circuit breaker. FIG. 23 is a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "on" state. FIG. 24 is also a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "off" state. FIG. 25 is a sectional view taken along line 23-23 in FIG. 21, showing the circuit breaker which is in "trip" state. FIG. 26 is a sectional view taken along line 26-26 in FIG. 22, showing an auxiliary cover. FIG. 27 is a perspective bottom view of the auxiliary cover. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment An example of a circuit breaker, which constitutes a first embodiment of this invention, will be described with reference to FIGS. 1 through 3. FIG. 1 is a perspective view showing the external appearance of the circuit breaker, FIG. 2 is a perspective view showing the circuit breaker with its auxiliary cover removed, and FIG. 3 is a sectional view taken along line 3-3 in FIG. 1. In those figures, parts corresponding functionally to those which have been described with reference to the conventional circuit breaker are therefore designated by the same reference numerals or characters. In FIG. 3, reference numeral 19 designates a rod engaged with the trip bar 10, the rod 19 being protruded above through the surface 101 of the main cover 1b; and 20, a spring for maintaining the rod 19 protruded as described above. In the case where the auxiliary cover 4 is closed as shown in FIG. 1, the rod 19 is pushed down against the elastic force of the spring 20. When the auxiliary cover 4 is opened as shown in FIG. 2, the rod 19 is allowed to stick out by the elastic force of the spring 20, so that the trip bar 10 is turned in the direction of the arrow 18, whereby the circuit breaker is tripped. Second Embodiment Another example of the circuit breaker, which constitutes a second embodiment, is as shown in FIG. 4. The circuit breaker includes a trip button 21 which is manually operated. The trip button 21 is so designed that it is able to stick out, and it is held inside the auxiliary cover 4. In the case where the auxiliary cover 4 is closed as shown in FIG. 4, the circuit breaker is tripped by pushing the trip button 21 through a hole 22 formed in the auxiliary cover 4. When the auxiliary cover 4 is opened as shown in FIG. 2, the trip button 21 is allowed to stick out by the elastic force of a spring 23, so that the trip bar 10 is swung in the direction of the arrow 18, whereby the circuit breaker is tripped. Third Embodiment Another example of the circuit breaker, which constitutes a third embodiment, will be described with reference to FIGS. 5 and 6. In the circuit breaker, the auxiliary cover 4 has a protrusion 24 which is adapted to elastically raise the trip bar 10. When the auxiliary cover 4 is opened, the protrusion 24 elastically raises the trip bar 10 to swing the latter 10 in the direction of the arrow 18, so that the circuit breaker is tripped. As was described above, in each of the first, second and third embodiments of the invention, the circuit breaker is automatically tripped upon opening of the auxiliary cover. Therefore, installation of the auxiliary device on the circuit breaker can be achieved with high security and with high reliability. Fourth Embodiment Another example of the circuit breaker, which constitutes a fourth embodiment of the invention, will be described with reference to FIGS. 7, 8 and 9. FIG. 7 is a sectional view showing the circuit breaker which is in "on" state, FIG. 8 is a sectional view showing an auxiliary cover of the circuit breaker, and FIG. 9 is a perspective bottom view of the auxiliary cover. In those figures, parts corresponding functionally to those which have been described with reference to the conventional circuit breaker are therefore designated by the same reference numerals or characters. In FIGS. 7 through 9, reference numeral 59 designates the aforementioned auxiliary cover, which has a guide 59a for guiding the arcuate base 7a of the handle 7, and an opening 59b through which the operating protrusion 7a is extended outside; and 60, recesses formed in the inner surface of the auxiliary cover, with which the end of the arcuate base 7a of the handle 7 is engaged when the latter 7 is at the "on" position. As was described above, the auxiliary cover 59 has the recesses 60. Hence, when the handle 7 is set at the "on" position, the end of the arcuate base 7a of the handle is engaged with the recesses 60. That is, when the circuit breaker is in "on" state, the auxiliary cover 59 cannot be opened engaging with the handle 7. Fifth Embodiment Another example of the circuit breaker, which constitutes a fifth embodiment of the invention, will be described with reference to FIGS. 10, 11 and 12. FIG. 10 is an exploded perspective view showing the circuit breaker; 11, a sectional view of an auxiliary cover of the circuit breaker; and FIG. 12 is a perspective view of the handle of the circuit breaker. In FIGS. 10 through 12, parts corresponding functionally to those which have been described with reference to the first embodiment are therefore designated by the same reference numerals or characters. In FIGS. 10 through 12, reference numeral 61 designates a pair of pins which are protruded respectively from two opposite side walls of an opening 59b formed in the aforementioned auxiliary cover 59 of the circuit breaker; and 62, a pair of cuts formed in the arcuate base 7b of the handle 7 on both sides of the operating protrusion 7b, respectively, in such a manner that each of them has a width large enough to receive the pin 61. As was described above, in the circuit breaker, the auxiliary cover 59 has the pair of pins 61. Hence, only when the handle 7 is at the "trip" position as shown in FIG. 10, the pins 61 are aligned with the cuts 62; that is, the auxiliary cover 59 can be opened only when the circuit breaker is in "trip" state. In the case where the circuit breaker is in "on" or "off" state, the pins 61 are engaged with the edges of the arcuate base 7a of the handle 7, thus inhibiting the opening of the auxiliary cover 59. That is, the auxiliary cover 59 can be opened only when the circuit breaker is in "trip" state. When an auxiliary device is installed on the circuit breaker, the latter is maintained unchanged in operation; i.e., the circuit breaker is maintained in "trip" state, thus facilitating the installation of the auxiliary device. Sixth Embodiment Another example of the circuit breaker, which constitutes a sixth embodiment of the invention, will be described with reference to FIG. 13, in which parts corresponding functionally to those which have been described with reference to the fourth embodiment are therefore designated by the same reference numerals or characters. In FIG. 13, reference numeral 63 denotes an actuator which is set in the surface 101 of the main cover 1b in such a manner that it is movable back and forth and urged by a spring 64 so as to be locked; and 65, a locking portion formed in the inner surface of the auxiliary cover 59, to which the actuator 63 is locked. In the sixth embodiment, the main cover 1b has the actuator 63 as was described above. Hence, only when the handle 7 is at the "off" position as shown in FIG. 13, the actuator is retracted against the elastic force of the spring 64 being pushed by the end of the arcuate base 7a of the handle 7. That is, only when the circuit breaker is in "off" state, the auxiliary cover 59 can be opened. In other words, when the circuit breaker is in "on" or "trip" state, the actuator 63 is locked to the locking portion 65 by means of the spring 64, thus inhibiting the opening of the auxiliary cover 59. With the sixth embodiment, the auxiliary cover can be opened only when the circuit breaker is in "off" state. Hence, in installing an auxiliary device on the circuit breaker, the latter is maintained unchanged in operating state; i.e., the circuit breaker is maintained turned off, thus expediting the installation of the auxiliary device. Seventh Embodiment Another example of the circuit breaker, which constitutes a seventh embodiment of the invention, will be described with reference to FIGS. 14, 15 and 16. FIG. 14 is a sectional diagram showing the circuit breaker which is in "on" state, FIG. 15 is a sectional view of an auxiliary cover of the circuit breaker, and FIG. 16 is a perspective bottom view of the auxiliary cover. In those figures, parts corresponding functionally to those which have been described with reference to the fourth embodiment are therefore designated by the same reference numerals or characters. In FIGS. 14 through 16, reference numeral 66 designates an actuator which is swingably mounted inside the auxiliary cover 59, the actuator 66 being urged by a spring 67 so as not to be locked; and 68, a locking portion formed in the surface 101 of the main cover. The actuator 66 is locked to the locking portion 68. In the seventh embodiment, the auxiliary cover 59 has the actuator 66 in the above-described manner. Hence, only when the handle 7 is at the "on" position as shown in FIG. 14, the actuator 66, being pushed by the end of the arcuate base 7a of the handle 7, is engaged with the locking portion 68. Therefore, only when the circuit breaker is in "on" state, the auxiliary cover 59 cannot be opened. When the circuit break is in "off" or "trip" state, the actuator 66, being swung by the spring 67 as shown in FIGS. 15 and 16, is disengaged from the locking portion 68, thus permitting the opening of the auxiliary cover 59. Eighth Embodiment Another example of the circuit breaker, which constitutes an eighth embodiment of the invention, will be described with reference to FIGS. 17 and 18. FIG. 17 is a sectional view showing the circuit breaker which is in "on" state, and FIG. 18 is also a sectional view of the circuit breaker which is in "off" state. In FIGS. 17 and 18, parts corresponding functionally to those which have been described with reference to the fourth embodiment are therefore designated by the same reference numerals or characters. In FIGS. 17 and 18, reference numeral 69 designates mounting screws which detachably mount the auxiliary cover 59 on the main cover 1b; and 70, a slider which is movable back and forth together with the handle 7. The slider 70 is so shaped that it covers the mounting screws 69 only when the handle is at the "on" position. In the eighth embodiment, the slide 70 is provided for the handle 7 in the above-described manner. Hence, when the handle is at the "on" position, the slider 70 covers the mounting screws 69, thus inhibiting removal of the mounting screws 69; that is, the auxiliary cover 59 cannot be opened. When the handle is at the "off" position, the mounting screws 69 are not covered by the slider 70 as shown in FIG. 18, and therefore the mounting screws 69 can be removed to open the auxiliary cover 59. Similarly, when the handle is at the "trip" position, the mounting screws 69 are not covered by the slider 70, and therefore the auxiliary cover 59 can be opened. Ninth Embodiment Another example of the circuit breaker, which constitutes a ninth embodiment of the invention, will be described with reference to FIGS. 19 and 20. FIG. 19 is a sectional view of the circuit breaker which is in "trip" state, and FIG. 20 is a perspective view of the circuit breaker with its auxiliary cover removed. In FIGS. 19 and 20, parts corresponding functionally to those which have been described with reference to the fourth embodiment are therefore designated by the same reference numerals or characters. In FIGS. 19 and 20, reference numeral 71 denotes an actuator which is swingably mounted on the surface 101 of the main cover 1b, the actuator being urged by a spring 72 so as to be locked; and 73, a locking portion formed on the inner surface of the auxiliary cover 59. The actuator 71 is locked to the locking portion 73. In the ninth embodiment, the actuator 71 is provided on the main cover 1b in the above-described manner. Hence, when the circuit breaker is tripped, as shown in FIG. 19 the actuator 71, being swung against the elastic force of the spring 71 by the movable piece 5, is disengaged from the locking portion 73, so that the auxiliary cover 59 can be opened. In the case where the circuit breaker is in "on" or "off" state, the amount of rise of the movable piece 5 is so small that the actuator 71 is not swung; that is, the actuator 71 is kept locked to the locking portion 73 by the spring 72. Therefore, the auxiliary cover 59 cannot be opened. That is, the auxiliary cover 59 can be opened only when the circuit breaker is in "trip" state. Hence, in installing an auxiliary device on the circuit breaker, the latter is maintained unchanged in operation (the circuit breaker is maintained in "trip" state), thus expediting the installation of the auxiliary device. In some circuit breakers, the amount of rise of the movable piece is the same in tripping the circuit breaker and in turning it off. In this case, the auxiliary cover 59 cannot be opened only when the circuit breaker is in "off" state. As was described above, in the fourth through ninth embodiments, it is inhibited to open the auxiliary cover when the circuit breaker is in "on" state. Therefore, installation of an auxiliary device on the circuit breaker can be achieved with high security and with high reliability.

Claims: A circuit breaker comprising: a casing (1) including a base (1a) and a main cover (1b) secured to the base, the casing accommodating a circuit breaking mechanism (5 to 13); a recess (3) formed in one surface of the main cover (1b), the opposite surface of which is on the side of the base, the recess (3) being adapted to receive an auxiliary device (2) of the circuit breaking mechanism; and an auxiliary cover (4) mounted on the main cover (1b) in such a manner as to close said recess (3); characterized in that means are provided for preventing opening of the auxiliary cover (4) while the circuit breaker remains in an ON state. The circuit breaker according to claim 1, wherein said means includes a link mechanism (19, 20; 21, 22, 23; 24) for putting the circuit breaker into either one of an OFF state and a TRIP state in conjunction with the opening operation of the auxiliary cover (4). The circuit breaker according to claim 1, wherein said means includes a lock mechanism (60; 61, 62; 63, 64, 65; 66, 68) for locking the auxiliary cover (4) to the main cover (1b) when the circuit breaker is in the ON state. The circuit breaker according to claim 3, wherein said lock mechanism permits the auxiliary cover (4) to open from the main cover (1b) when the circuit breaker is in either one of the OFF state and the TRIP state. The circuit breaker according to claim 1, wherein said means includes a mechanism (70) for covering a fixing screw (69) when said circuit breaker is in the On state, the fixing screw (69) securing the auxiliary cover (4) to the main cover (1b). The circuit breaker according to claim 5, wherein said mechanism (70) permits removal of the fixing screw (69) when the circuit breaker is in either one of the OFF state and the TRIP state.

Inventors: FUJII HIROSHI, FUJIWARA KOUHEI, HOSOGAI SETSUO, IIO TSUKASA, KOBAYASHI YOSHIAKI, MURATA SHIROU, TANIBE TOSHIYUKI, YAMAGATA SHINJI, YAMASAKI SHINSAKU, FUJII, HIROSHI, FUJIWARA, KOUHEI, HOSOGAI, SETSUO, IIO, TSUKASA, KOBAYASHI, YOSHIAKI, MURATA, SHIROU, TANIBE, TOSHIYUKI, YAMAGATA, SHINJI, YAMASAKI, SHINSAKU, Fujii, Hiroshi, c/o Mitsubishi Denki K.K., Fujiwara, Kouhei, c/o Mitsubishi Denki K.K., Hosogai, Setsuo, c/o Mitsubishi Denki K.K., Iio, Tsukasa, c/o Mitsubishi Denki K.K., Kobayashi, Yoshiaki, c/o Mitsubishi Denki K.K., Murata, Shirou, c/o Mitsubishi Denki K.K., Tanibe, Toshiyuki, c/o Mitsubishi Denki K.K., Yamagata, Shinji, c/o Mitsubishi Denki K.K., Yamasaki, Shinsaku, c/o Mitsubishi Denki K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1993
Main classification: H01H9
IPC codes: H01H71