Circuit breaker

Abstract: In a trip relay mechanism (50) of circuit breaker wherein a latch (23A), a latch lever (25A) and a trip bar (34) are urged to engage with each other; the trip bar (34) is disposed between the latch (23A) and the latch lever (25A) in the direction of power source side -­ load side of the circuit breaker and they (23A, 25A, 34) are urged by one double-torsion spring (35), and further the trip bar (34) is separated into a main part (34B) extended over each pole and a latching part (34A) for engaging the latch lever (25A).

Description: The present invention relates to a circuit breaker according to the pre-characterizing part of claim 1. Such a circuit breaker is known from e.g. EP-A-176 025 or US-A-3 460 075. More particularly it relates to an improvement of a trip relay mechanism which transmits an operation of an automatic trip device to a cradle. FIGs.12-17 show a conventional circuit breaker, FIG.12 is a front view of the circuit breaker, and FIG.13 is a cross-sectional view taken on line XIII-XIII of FIG.12. In these figures, a case 1 comprises a base la and a cover 1b, and therein a central pole 1A having an opening/closing mechanism and adjacent poles 1B and 1B having no opening/closing mechanism are provided. A fixed conductor 2 of power source side is fixed on the base la, and a fixed contact 3 is fixed on the fixed conductor 2. A movable conductor 7 having a movable contact 6 thereon is pivotally mounted on a second contact arm 10b by a first pin 11. The movable conductor 7 is connected to an automatic trip device 4 via a flexible wire 8 and a connection bar 9. The automatic trip device 4 has therein a thermal-electromagnetic mechanism (not shown) or a solid-state trip device (not shown). A fixed conductor 5 of load side is provided out of the automatic trip device 4. A contact arm 10 comprises a first contact arm 10a which is connected to an opening/closing operation mechanism described later and the second contact arm 10b. Both contact arms 10a and 10b are pivotally held by a shaft 12. The first contact arm 10a of each pole is linked by a crossbar 13. A J-shaped aperture 14, which is long in an opening/closing direction of the movable contact 6, is formed on the first contact arm 10a, and an oblong hole 15, which is long in a crossing direction against the opening/closing direction and catches a second pin 16 together with the J-shaped aperture 14, is formed on the second contact arm 10b. The second pin 16 is urged by a tension spring 17 to the first pin 11. A compression spring 18 is provided between the movable conductor 7 and the second contact arm 10b in order to give contact pressure to the movable contact 6. Via an urge of a tension spring 20d, an operation handle 19 is linked with the opening/closing operation mechanism 20 which comprises a cradle 20a, an upper link 20b and a lower link 20c etc. A stopper pin 21 is provided on the cradle 20a. The first contact arm 10a is connected with the lower link 20c by a connection pin 22. A trip relay mechanism 50 which comprises several mechanical parts is provided between the cradle 20a and a trip rod 32 of the automatic trip device 4. FIG.16 is an enlarged view of the trip relay mechanism 50 in FIG.13. Such a trip relay mechanism is also shown in e.g. US-A-3 171 929. In FIG.16, an engaging part 23a of a latch 23 is engaged with an end of the cradle 20a thereby to position the cradle 20a into a predetermined position. The latch 23 is rotatably held by a pin 24. A roller 125 which is mounted on a latch lever 25 is engaged with the latch 23 so as not to allow the latch 23 to rotate by the cradle 20a. The latch lever 25 is also rotably held by a pin 26. A lever 27a which is fixed to a trip bar 27 is engaged with a top end of the latch lever 25 so as not to allow the latch lever 25 to disengage from the latch 23 and to rotate thereby. The trip bar 27 is also rotatably held by a pin 28. By a torsion spring 29 which is mounted on the pin 24, the latch 23 and the latch lever 25 are urged in an anti-clockwise direction. The trip bar 27 is urged by a tension spring 30 such that the lever 27a of the trip bar 27 is engaged with the latch lever 25. As shown in FIG.12, the trip bar 27 is extended over respective poles 1B, 1A and 1B and is held by a side frame 31a of a frame 31 fixed on the base la. The trip relay mechanism 50 (FIG.13), which comprises the latch 23, the latch lever 25 and the trip bar 27, and the opening/closing operation mechanism 20 etc. are held by and between the two side frames 31a and 31a. Next, operation of this circuit breaker is described. FIGs. 12, 13 and 16 show a closed state of the circuit breaker. In FIG.13, a current flows through the fixed conductor 2 of power source side, the fixed contact 3, the movable contact 6, the movable conductor 7, the flexible wire 8, the connection bar 9, the automatic trip device 4 and the fixed conductor 5 of load side. When the operation handle 19 is moved to a direction shown by an arrow 33 thereby to open the circuit breaker, the contact arm 10 is lifted up by the opening/closing operation mechanism, and thereby the movable contact 6 together with the movable conductor 7 are disconnected from the fixed contact 3 as shown in FIG.14. At that time, since the second pin 16 is caught in a left end 14a of the J-shaped aperture 14 by receiving an urge of the tension spring 17, both the first contact arm 10a and the second contact arm 10b are pivotally lifted up by the opening/closing operation mechanism 20 around the shaft 12 until the second contact arm 10b collides with the stopper pin 21 and stops thereat. Under the closed state shown by FIG.13 and an open state shown by FIG.14, since the trip rod 32 is not projected out of the automatic trip device 4, the trip relay mechanism 50 (FIG.13) maintains a state shown in FIG.16, and the cradle 20a is latched by the latch 23. When an overcurrent flows through the circuit breaker, the automatic trip device 4 operates and the trip rod 32 projects out of the automatic trip device 4 as shown in FIG.17. As a result, the trip bar 27 is rotated clockwise against an urge of the tension spring 30 and the lever 27a is disengaged from the latch lever 25, and thereby the latch lever 25 is allowed to rotate clockwise. Then, the latch 23 is rotated clockwise by a lifting force of the cradle 20a against an urge of the torsion spring 29, and simultaneously the latch lever 25 is also rotated clockwise by the latch 23 against the urge of the torsion spring 29. Consequently, the trip relay mechanism 50 instantaneously gets settled in a state shown by FIG.17 and the cradle 20a jumps up to rotate anti-clockwise. By this rotation of the cradle 20a, the opening/closing operation mechanism 20 is operated, and thereby the contact arm 10 is lifted up to disconnect the movable contact 6 from the fixed contact 3 as shown in FIG.15. At that time, in the same way as in the open state shown by FIG.14, since the second pin 16 is caught in the left end 14a of the J-shaped aperture 14 by receiving the urge of the tension spring 17, both the first contact arm 10a and the second contact arm 10b are pivotally lifted up by the opening/closing operation mechanism 20 around the shaft 12 until the second contact arm 10b collides with the stopper pin 21 and stops thereat. Thus, the overcurrent is interrupted and now the circuit breaker is in a trip state. In the above-mentioned circuit breaker, the latch 23, the latch lever 25 and the trip bar 27 are disposed by a predetermined positional relationship in order to minimize a moment for disengagement of the trip bar 27, thereby to minimize a required force upon the trip rod 32 to disengage the cradle 20a from the latch 23. That is, in FIG.16, predetermined intervals are required between each fulcrum and each point of application about the latch 23 and the latch lever 25, and more specifically between the engaging part 23a of the latch 23 and an axis of the pin 24, between the axis of the pin 24 and a contacting point 23h, between the contacting point 23h and an axis of the pin 26 and between the axis of the pin 26 and a contacting point 25h. To keep these intervals, the latch 23, the latch lever 25 and the trip bar 27 are disposed in this' order from the power source side to the load side. Therefore, size of the circuit breaker becomes inevitably long in the direction of power source side - load side. Further, since the trip bar 27 must be mounted in the trip relay mechanism 50 (FIG.13) and extended over all poles of the circuit breaker as shown in FIG.12, it is difficult to assemble the trip bar 27 into the circuit breaker. Furthermore, since the tension spring 30 and the torsion spring 29 are required, it takes a skill and long time for a worker to assemble the trip relay mechanism 50, and a cost thereof comes to high because of plenty of parts. It is thus an object of the present invention to offer a circuit breaker having a shortened length in the direction of power source side - load side, wherein a trip relay mechanism is simplified and easy to assemble. Solution of this object is achieved by what is claimed in claim 1. A circuit breaker according to the present invention thus comprises a case; a fixed contact fixedly mounted to said case; a movable contact which is pivotally mounted to said case and is movable to be connected with said fixed contact; opening/closing operation means which is pivotally mounted to said case for disconnecting/connecting said movable contact from/with said fixed contact and is urged to disconnect said movable contact from said fixed contact; a latch which is pivotally mounted to said case and is urged to engage with said opening/closing operation means; a latch lever which is pivotally mounted to said case and is urged to engage with said latch; a trip bar which is pivotally mounted to said case and is urged to engage with said latch lever; and an automatic trip device for causing said trip bar to disengage from said latch lever when a current greater than a predetermined value flows through said circuit breaker thereby to cause said movable contact to disconnect from said fixed contact. The circuit breaker is furthermore characterized in that a pivot of said trip bar is disposed between a pivot of said latch and a pivot of said latch lever in a direction of power source side - load side of said case. In other words, as it is shown in Fig. 16 of the drawings and as it was discussed above, in a known trip relay mechanism according to e. g. US-A-3 171 929 the trip bar is disposed at the position being most adjacent to load side, as the respective pivots of the latch, the latch lever and the trip bar are arranged in this sequential order from power source side to load side. Thus, a conventional circuit breaker necessitates a structure wherein the trip bar is arranged at the end position of the trip relay mechanism. This is not to say compulsory but at least natural when the transmission order of the trip operation is considered. Said transmission order in case of a conventional circuit breaker is given as trip rod - trip bar - latch lever - latch 23. In contrary thereto, the present invention gives a new arrangement without being tied to the conventional arrangement and said new arrangement provides a length reduction of the whole circuit breaker, as the pivot of the trip bar is arranged between the pivots of latch and latch lever when seen in power source side - load side direction. Advantageous modifications are subject matter of the subclaims. The following is a more detailed description of the present invention to be taken in conjunction with the accompanying drawings, in which: FIG.1 is a front view showing an embodiment of a circuit breaker of the present invention; FIG.2 is a cross-sectional view taken on line II-II of FIG.1; FIG.3 is an enlarged perspective view showing a trip relay mechanism of an embodiment of the present invention; FIG.4 is a cross-sectional view showing the trip relay mechanism in a state before tripping of a circuit breaker between a cradle and an automatic trip device; FIG.5 is a cross-sectional view showing the trip relay mechanism in a state just after tripping of a circuit breaker from a state shown in FIG.4; FIG.6 is a perspective view showing a latch of an embodiment of the present invention; FIG.7 is a perspective view showing a latch lever of an embodiment of the present invention; FIG.8 is a perspective view showing a trip bar of an embodiment of the present invention; FIG.9 is a perspective view showing a double-torsion spring of an embodiment of the present invention; FIG.10 is a reverse perspective view of FIG.7; FIG.11 is a perspective view showing a latch lever and a roller of another embodiment of the present invention; FIG.12 is the front view showing the conventional circuit breaker; FIG.13 is the cross-sectional view taken on line XIII-XIII of FIG.12; FIG.14 is the partial enlarged view of FIG.13 when the circuit breaker is open; FIG.15 is the partial enlarged view of FIG.13 when the circuit breaker is tripped; FIG.16 is the cross-sectional view showing the trip relay mechanism before tripping of the conventional circuit breaker between the cradle and the automatic trip device ; and FIG.17 is the cross-sectional view showing the trip relay mechanism just after tripping of the conventional circuit breaker from the state shown in FIG.16. It should be noted that the illustrations in FIGs. 1 to 11 and 12 to 17, respectively, are in the same scale; however, this is only for ease of preparing the drawings. Hereafter, preferred embodiments of the present invention is described with reference to the accompanying drawings. FIGs.1-10 show an embodiment of the present invention. FIG.1 is a front view of the circuit breaker, and FIG.2 is a cross-sectional view taken on line II-II of FIG.1. In these figures, a case 1 comprises a base la and a cover lb, and therein a central pole 1A having an opening/closing mechanism and adjacent poles 1B and 1B having no opening/closing mechanism are provided. A fixed conductor 2 of power source side is fixed on the base la, and a fixed contact 3 is fixed on the fixed conductor 2. A movable conductor 7 having a movable contact 6 thereon is pivotally mounted on a second contact arm 10b by a first pin 11. The movable conductor 7 is connected to an automatic trip device 4 via a flexible wire 8 and a connection bar 9. The automatic trip device 4 has therein a thermal-electromagnetic mechanism (not shown) or a solid-state trip device (not shown). A fixed conductor 5 of load side is provided out of the automatic trip device 4. A contact arm 10 comprises a first contact arm 10a which is connected to an opening/closing operation mechanism described later and the second contact arm 10b. Both contact arms 10a and 10b are pivotally held by a shaft 12. The first contact arm 10a of each pole is linked by a crossbar 13. A J-shaped aperture 14, which is long in an opening/closing direction of the movable contact 6, is formed on the first contact arm 10a, and an oblong hole 15, which is long in a crossing direction against the opening/closing direction and catches a second pin 16 together with the J-shaped aperture 14, is formed on the second contact arm 10b. The second pin 16 is urged by a tension spring 17 to the first pin 11. A compression spring 18 is provided between the movable conductor 7 and the second contact arm 10b in order to give contact pressure to the movable contact 6. Via an urge of a tension spring 20d, an operation handle 19 is linked with the opening/closing operation mechanism 20 which comprises a cradle 20a, an upper link 20b and a lower link 20c etc. A stopper pin 21 is provided on the cradle 20a. The first contact arm 10a is connected with the lower link 20c by a connection pin 22. A trip relay mechanism 50 which comprises several mechanical parts is provided between the cradle 20a and a trip rod 32 of the automatic trip device 4. FIG.3 is an enlarged perspective view of the trip relay mechanism 50, and FIGs. 4 and 5 are cross-sectional views of the trip relay mechanism 50. In FIG.3, a frame 31 comprising both side frames 31a and 31a is fixed on the base la (FIG.2). A shaft 24A is held by the side frames 31a and 31a. A latch 23A is cradle-shaped as shown in FIG.6 and has concavities 23b and 23b therein for holding the shaft 24A (FIG.3) and an engaging part 23C on one arm thereof for engaging a roller 125 (FIG.3). A latch lever 25A is fork-shaped with opposing side wings 25a and 25f as shown in FIG.7. The side wings 25a and 25f have an oblong hole 25b and a cut-off part 25C for holding end portions 125a and 125b of the roller 125, respectively. Further, the side wing 25a has an engaging part 25d for engaging a projection 34a of a trip bar 34 (FIG.3) and a hook 25e for hooking an end portion 35c of a double-torsion spring 35. In FIG.3, the latch lever 25A is rotatably held by a pin 26A on the side frame 31a. A latching part 34A of the trip bar 34 comprises the projection 34a for preventing rotation of the latch lever 25A by the latch 23A, apertures 34b and 34b, a ditch 34c for catching another end portion 35d of the double-torsion spring 35 and an actuating part 34d to be pushed by the trip rod 32 (FIG.2). As shown in FIG.8, the trip bar 34 comprises the latching part 34A made of a pressed metal or nonmetal and a main part 34B made of a molded resin, corresponding to respective required functions. This detachable construction of the trip bar 34 is advantageous to present miniaturization and low cost thereof. When this trip bar 34 is assembled into the circuit breaker, firstly the latching part 34A is assembled in the frame 31 (FIG.3) as a member of the trip relay mechanism 50 (FIG.4), and secondly the frame 31 is fixed on the base la of the case 1, and thirdly the main part 34B which is extended over all poles 1B, 1A and 1B (FIG.1) is fixed on the latching part 34A by screwing two screws 134 into two female screws 34e formed on the latching part 34A, through corresponding two holes 34f formed in the main part 34B. Thus, the main part 34B can be assembled in a final step of assembly of the circuit breaker. The main part 34B and the latching part 34A may be coupled by pressurizing each other. FIG.9 is a perspective view of the double-torsion spring 35. A pair of coiled portions 35a are inserted around the shaft 24A (FIG.4), and a bridge portion 35b of the double-torsion spring 35 is engaged with an upper bosom portion 23e (FIG.3, 4 or 6) of the latch 23A. In FIG.4, the latch 23A is urged anti-clockwise by the bridge portion 35b so as to engage the latch 23A with the cradle 20a, and the latch lever 25A is urged anti-clockwise by the end portion 35c so as to engage the latch lever 25A with the latch 23A, and moreover the trip bar 34 (the latching part 34A) is urged anti-clockwise by the end portion 35d so as to engage the latching part 34A with the latch lever 25A. A stopper pin 36 is mounted on the side frame 31a (FIG.3) in order to stop the rotation of the latch lever 25A. Next, operation of this circuit breaker is described. FIGs.1, 2 and 4 show a closed state of the circuit breaker. In FIG.2, a current flows through the fixed conductor 2 of power source side, the fixed contact 3, the movable contact 6, the movable conductor 7, the flexible wire 8, the connection bar 9, the automatic trip device 4 and the fixed conductor 5 of load side. When the operation handle 19 is moved to a direction shown by an arrow 33 thereby to open the circuit breaker, the contact arm 10 is lifted up by the opening/closing operation mechanism, and thereby the movable contact 6 together with the movable conductor 7 are disconnected from the fixed contact 3 as shown in FIG.14 (prior art). At that time, since the second pin 16 is caught in a left end 14a of the J-shaped aperture 14 by receiving an urge of the tension spring 17, both the first contact arm 10a and the second contact arm 10b are pivotally lifted up by the opening/closing operation mechanism 20 around the shaft 12 until the second contact arm 10b collides with the stopper pin 21 and stops thereat. In the closed state shown by FIG.2 and an open state shown by FIG.14, since the trip rod 32 is not projected out of the automatic trip device 4, the trip relay mechanism 50 (FIG.2) maintains a state shown in FIG.4 by receiving urges of the double-torsion spring 35 upon the latch 23A, the latch lever 25A and the trip bar 34, and thereby the cradle 20a is latched by the latch 23A. When an overcurrent flows through the circuit breaker, the automatic trip device 4 operates and the trip rod 32 projects out of the automatic trip device 4 as shown in FIG.5. Thereby, the latching part 34A of the trip bar 34 is rotated clockwise against the urge of the double-torsion spring 35, and the projection 34a of the latching part 34A is disengaged from the engaging part 25d of the latch lever 25A. Then, the latch lever 25A is allowed to rotate clockwise, and thereby the latch 23A is rotated clockwise by a lifting force 37 (FIG.4) of the cradle 20a against the urge by the bridge portion 35b of the double-torsion spring 35. Simultaneously the latch lever 25A is also rotated clockwise by the latch 23A against the urge by the end portion 35c of the double-torsion spring 35. Consequently, the trip relay mechanism 50 instantaneously gets settled in a state shown by FIG.5 and the cradle 20a jumps up to rotate anti-clockwise. Thereafter, the trip rod 32 immediately returns to the state as it was before, and thereby the latch 23A, the latch lever 25A and the latching part 34A of the trip bar 34 return to the state shown by FIG.4 by receiving the urge of the double-torsion spring 35. Thereafter, when the operation handle 19 (FIG.2) is operated by a resetting procedure, the cradle 20a is engaged with the latch 23A with a click. In the above-mentioned circuit breaker, the latch 23A, the latch lever 25A and the latching part 34A of the trip bar 34 are disposed by a predetermined positional relationship in order to minimize a moment for disengagement of the latching part 34A thereby to minimize a required force upon the trip rod 32 to disengage the cradle 20a from the latch 23A. That is, in FIG.4, predetermined intervals are secured between each fulcrum and each point of application about the latch 23A and the latch lever 25A, and more specifically between the engaging part 23a of the latch 23A and an axis of the pin 24A, between the axis of the shaft 24A and a contacting point 23h, between the contacting point 23h and an axis of the pin 26A and between the axis of the pin 26A and a contacting point 25h. Thereby, the cradle 20a, for which comparatively large force is required to disengage itself from the latch 23A, is disengaged from the latch 23A by actuating the actuating part 34d of the trip bar 34 by means of the trip rod 32 with small force. Since a center of rotation of the trip bar 34 (namely an axis of the shaft 28A) is disposed between a center of the latch 23A (namely the axis of the shaft 24A) and a center of the latch lever 25A (namely the axis of the pin 26A) in a power source side - load side direction, length of the trip relay mechanism in said direction, and hence length of the circuit breaker in said direction, becomes shorter than that of the conventional circuit breaker. FIG.10 is a rear perspective view of the latch lever 25A. FIG.11 is a rear perspective view showing another embodiment of the latch lever. In FIG.11, the latch lever 225A has a side wing 225f wherein an oblong hole 225g for catching the end portion 125b of the roller 125 and a circle hole 225h which is connected to the oblong hole 225g for passing the roller 125 therein are formed. A reverse side wing 225a has the similar configuration to the side wing 25a of FIG.7. Since the side wing 225f has no such cut-off part 25c as shown in FIG.10, it is stronger than the side wing 25f against a mechanical shock given thereto. Therefore, there is no liability of deforming even when the side wing 225f collides with the stopper pin 36 (FIGs.3-5). The circle hole 225h may be substitutively formed in the reverse side wing 225a. While specific embodiments of the invention have been illustrated and described herein, it is realized that other modifications and changes will occur to those skilled in the art.

Claims: A circuit breaker comprising: a case (1); a fixed contact (3) fixedly mounted to said case; a movable contact (6) which is pivotally mounted to said case (1) and is movable to be connected with said fixed contact (3); opening/closing operation means (20) which is pivotally mounted to said case (1) for disconnecting/connecting said movable contact (6) from/with said fixed contact (3) and is urged to disconnect said movable contact (6) from said fixed contact (3); a latch (23A) which is pivotally mounted to said case (1) and is urged to engage with said opening/closing operation means (20); a latch lever (25A) which is pivotally mounted to said case (1) and is urged to engage with said latch (23A); a trip bar (34) which is pivotally mounted to said case (1) and is urged to engage with said latch lever (25A); and an automatic trip device (4) for causing said trip bar (34) to disengage from said latch lever (25A) when a current greater than a predetermined value flows through said circuit breaker thereby to cause said movable contact (6) to disconnect from said fixed contact (3), characterized in that a pivot (28A) of said trip bar (34) is disposed between a pivot (24A) of said latch (23A) and a pivot (26A) of said latch lever (25A) in a direction of power source side - load side of said case (1). The circuit breaker of claim 1, wherein said trip bar comprises a main part (34B) extending over each pole of said circuit breaker and a latching part (34A) which is detachably connected with said main part (34B) for engaging with said latch lever (25A). The circuit breaker of claim 1 or 2, wherein said latch (23A), said latch lever (25A) and said trip bar (34) are urged by a single double-torsion spring (35). The circuit breaker of claim 1, 2 or 3, wherein said latch is cradle-shaped and said latch lever is fork-shaped. The circuit breaker of anyone of claims 1 to 4, wherein said latch lever (25A) comprises opposing two wings (225a, 225f) each having oblong holes (25b, 225g, 225h) and a roller (125) held therein. The circuit breaker of anyone of claims 1 to 5, further comprising a double-torsion spring (35) which is mounted around said pivot (24A) of said latch (23A) and urges said latch (23A), said latch lever (25A) and said trip bar (34). The circuit breaker of claim 6, wherein said latch (23A), said latch lever (25A), said trip bar (34) and said double-torsion spring (35) constitute a trip relay unit.

Inventors: TODA HARUHISA C O FUKUYAMA SEI, TODA, HARUHISA C/O FUKUYAMA SEISAKUSHO
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1988
Main classification: H01H71
IPC codes: H01H71