MAGNETIC VACUUM CIRCUIT BREAKER

Abstract: A magnetic vacuum circuit breaker includes a sealed casing (1). Mounted in the casing (1) are a stationary contact (2), a movable contact (4), a linkage (100) connected to the movable contact (4), a tension spring (7′) for activating the linkage (100), and a stop device controllable by an electromagnet for normally hindering the linkage (100) from being activated by the tension spring (7′). A manual switch (200) is provided for moving the movable contact (4) to electrically connect with or disconnect from the stationary contact (2) to thus close or open the circuit. An automatically indicating device (300) can be driven by the linkage (100) to indicate the state of overload or short-circuit when the circuit is converted into the same state. In addition, when the circuit is overloaded or short-circuited, the linkage (100) is released from the stop device by the action of the electromagnet (10′, 11) so that the movable contact (4) is activated by the tension spring (7′) to separate from the stationary contact (2) to thus open the circuit. A pair of mutually attractable magnetic members (M1, 61) are used to transfer motions between the linkage (100) and the manual switch (200).

Description: This invention relates to a magnetic circuit breaker having a simple structure which opens a power circuit when the circuit is overloaded or short-circuited. Several different types of electrical circuit breakers are known. US-3 492 614 discloses a circuit breaking having a pair of contacts held together by a linkage which is connected to a latching mechanism biassed by tension springs. In the event of a circuit overload, a bimetal heats to release the latching mechanism and release the linkage to open the contacts. A circuit breaker according to the preamble of claim 1 is shown in Figure 1 and disclosed in greater detail in my U.S. patent No. 4 288 767. Referring to Figure 1, the circuit breaker of my U.S. patent 4 288 767 automatically opens a power circuit, when overloaded or short-circuited, by the complicated motion from a protection means 7 through a magnetic control means 10 to a magnetic contacting plate means 8. It is an object of this invention to simplify the structure of the automatic circuit breaker. In accordance with this invention, there is provided a circuit breaker comprising a casing, a contact device mounted sealingly in said casing and including a stationary contact and a movable contact normally contacting said stationary contact, a lower magnetic member disposed within said casing and capable of moving downwardly to separate said movable contact from said stationary contact, and a manual switch including a sub-casing fixed on an upper wall of said casing and an upper magnetic member movable relative to the lower magnetic member to apply or release a magnetic attractive force between said upper and lower magnetic members, characterised in that a linkage is disposed in said casing below the lower magnetic member and is connected to said movable contact and to said lower magnetic member, a tension spring interconnects said lower magnetic member and said linkage for biassing said movable contact to separate from said stationary contact, a stop device is connected to said linkage to normally prevent movement of said linkage, the stop device is responsive to a circuit overload or short-circuit to release said linkage for movement under the force of said tension spring to separate the movable contact from the stationary contact, an indicating device is drivable by said linkage to indicate an overload or short-circuit condition, and release of the magnetic attractive force between said upper and lower magnetic members causes said lower magnetic member to pivot downwards and move said linkage to separate said movable contact from said stationary contact, the magnetic attractive force between said upper and lower magnetic members being greater than the tension force of said tension spring. Other features and advantages of this invention will become apparent from the following detailed description of the preferred embodiments thereof, given with reference to the accompanying drawings in which: Fig. 1 is a sectional view showing a conventional automatic magnetic switch; Fig. 2 is a sectional view showing a magnetic vacuum circuit breaker of this invention when in a normal condition; Fig. 3 is a schematic view illustrating the linking-up motion of a linkage of the circuit breaker when overloaded or short-circuited; Fig. 4 is a schematic view indicating the partial analysis of the linking-up motion of the linkage; Fig. 5 is a schematic view illustrating the linking-up motion of the linkage when a manual switch is switched off; Fig. 6 is a top view showing the manual switch and an automatically indicating device of the circuit breaker, illustrating the position of a first arrow relative to a second arrow, the arrows being indicated on the automatically indicating device; Fig. 7 is a sectional view taken along the line 7-7 of Fig. 2, illustrating the operation between the manual switch and the automatically indicating device of the circuit breaker in broken lines; and Fig. 8 is a sectional view showing another magnetic vacuum circuit breaker of this invention. Referring to Fig. 2, there is shown a magnetic vacuum circuit breaker of this invention, in which the circuit is in a normal condition. The circuit breaker includes a sealed casing 1 in which a generally U-shaped stationary frame 101 is provided for mounting a linkage 100 thereon. Mounted in the left of casing 1 is a contact device which includes a stationary contact 2 electrically connected to left segment 3 of an electric wire screwed to casing 1, and a movable contact 4 electrically connected to right segment 5 of the electric wire and normally contacting stationary contact 2. A slidable rotary member 6 carrying a first magnetic block 61 has a longitudinal slide slot S1 for being mounted pivotally on stationary frame 101 above linkage 100. The slidable rotary member 6 is normally located at its uppermost position. A first tension spring 7′ connects linkage 100 to slidable rotary member 6 for biasing movable contact 4 to separate from stationary contact 2. Connected to the right of linkage 100 is a stop device which is provided for normally hindering linkage 100 from being activated by first tension spring 7′. A manual switch 200 is mounted on the upper wall of casing 1. An automatically indicating device 300 is provided for indicating the state of overload or short-circuit when the circuit is in the same state. It should be noted that a vacuum is normally maintained within casing 1 for the purpose of duration. Alternatively, casing 1 may be filled with an inert gas. The stop device includes a first crank C1, an electromagnet having a core 10′ and a coil 11, an inverted V-shaped armature 12 disposed rotatably between first crank C1 and the electromagnet, and a second tension spring 13 for biasing armature 12 to separate from the electromagnet. First crank C1 is mounted pivotally on stationary frame 101 by a first stationary pivot P1. The left arm of first crank C1 is provided with a raised stopper 8′ for normally blocking part of linkage 100 to hinder linkage 100 from being activated by first tension spring 7′. The right arm of first crank C1 is provided with a pin 9 at the free end thereof. An torsion spring (not shown) is installed on first stationary pivot P1 for biasing first crank C1 to rotate clockwise. Coil 11 is formed from part of right segment 5 of the electric wire. Inverted V-shaped armature 12 consists of a right arm normally biased to separate from core 10′ by second tension spring 13, and a left arm normally abutting on pin 9 so as to permit stopper 8′ to hinder linkage 100 from being activated. Manual switch 200 includes a sub-casing 14 fixed on the upper wall of casing 1, a rotary knob 15 having an axle 16 mounted rotatably in sub-casing 14, and a first permanent magnet M1 secured to the lower end of axle 16. Normally, the magnetic poles N-S of first permanent magnet M1 registers with the magnetic poles S-N of first magnetic block 61 to generate magnetic attractive force therebetween through a first bridging magnet B1 and in turn to turn first magnetic block 61 to its uppermost position, thereby closing the circuit. Automatically indicating device 300 includes a push rod 17 secured to axle 16, a second magnetic block 18 mounted on linkage 100, and a forked rotary member 19. Push rod 17 has a generally barb-shaped free end 171 with a rounded end surface (see Fig. 7). Second magnetic block 18 is normally located at its lowermost position. Forked rotary member 19 includes a horizontal arm 191 having a forked free end 20, and a longitudinal arm 192. A second permanent magnet M2 is secured to lower branch 21 of forked free end 20. Referring to Fig. 6, two aligned words "TRIP" and "NORMAL" are indicated on the outer surface of automatically indicating device 300 on the opposite sides of a transparent glass window 24. In addition, indicated on upper branch 22 of forked free end 20 are a first arrow A1 directing to the side of the word "TRIP", and a second arrow A2 indicated below first arrow A1 and directing to the side of the word "NORMAL". Second arrow A2 is visible from window 24 when forked rotary member 19 is located at its uppermost position. A third tension spring 23 is connected to horizontal arm 191 of forked rotary member 19 for biasing second permanent magnet M2 to move away from second magnetic block 18 to thus rotate forked rotary member 19 counterclockwise. Linkage 100 includes in turn from the left to the right: (1) a second crank C2, mounted pivotally on stationary frame 101 at the left end of linkage 100 by a second stationary pivot P2, including a left crank arm connected to slidable rotary member 6 by first tension spring 7′ and having a conducting portion 25 for normally connecting movable contact 4 to the left end of right segment 5 of the electric wire, and a right crank arm; (2) a four-bar sub-linkage, consisting of a first coupler L1 at the left upper portion, a second coupler L2 at the left lower portion, a third crank C3 mounted pivotally on stationary frame 101 by a third stationary pivot P3 at the right lower portion, and a rotatable frame at the right upper portion. It is connected rotatably to slidable rotary member 6 by a third coupler L3 at a first movable pivot R1 interconnecting second coupler L2 and third crank C3. Also, it is connected rotatably to a second movable pivot R2 of the right crank arm of second crank C2 by a fourth coupler L4 at a third movable pivot R3 interconnecting first coupler L1 and second coupler L2; (3) a T-shaped crank C3′, mounted pivotally on stationary frame 101 by third stationary pivot P3, including a left crank arm forming the rotatable frame of the four-bar sub-likage, an intermediate crank arm, and a right crank arm; (4) a fourth crank C4, disposed at the right upper end portion of linkage 100, mounted pivotally on stationary frame 101 by a fourth stationary pivot P4, carrying second magnetic block 18 on the upper end of the crank arm thereof, connected to the intermediate crank arm of T-shaped crank C3′ by a fifth coupler L5 having a horizontal slide slot S2 in which a crank pin of fourth crank C4 is received slidably; and (5) a fifth crank C5, mounted pivotally on stationary frame 101 at the right upper end of linkage 100 by a fifth stationary pivot P5, having a free end which is normally blocked by stopper 8′ so that it can't be activated by first tension spring 7′ to rotate closkwise, connected to the right crank arm of T-shaped crank C3′ by a sixth coupler L6 at an intermediate portion of fifth crank C5. It is noted that the pivot interconnecting T-shaped crank C′ and first coupler L1 fails to contact third coupler L3. When the circuit is in a normal condition, T-shaped crank C3′ and hence fifth crank C5 tend to rotate clockwise due to the tension force of first tension spring 7′. Accordingly, stopper 8′ can obstruct linkage 100 from movement. When overloaded or short-circuited, the linking-up motion of linkage 100 is shown in the phantom lines of Fig. 3. At the time, the right arm of armature 12 will be attracted by the electromagnet to rotate clockwise so that the left arm of armature 12 pushes first crank C1 to rotate counterclockwise, thereby causing stopper 8′ to separate from the free end of fifth crank C5 and in turn to permit first tension spring 7′ to activate linkage 100. In the above-mentioned motion of linkage 100, since slidable rotary member 6 is fixed, first movable pivot R1 interconnecting third coupler L3 and third crank C3 is fixed in the position shown in Fig. 4 due to the fact that two interconnecting cranks can't rotate. When fifth crank C5 is released, first tension spring 7′ will pull movable contact 4 away from stationary contact 2. At the time of pulling movable contact 4, second crank C2 rotates clockwise so as to rotate second movable pivot R2 to the right. Then, fourth coupler L4 and hence first coupler L1 push T-shaped crank C3′ to rotate clockwise, thereby rotating fourth crank C4 counterclockwise via fifth coupler L5 to move second magnetic block 18 to its uppermost position to thus attract second permanent magnet M2 downwardly, and simultaneously rotating fifth crank C5 clockwise via sixth coupler L6. When second permanent magnet M2 is attracted toward second magnetic block 18, forked rotary member 19 turns to its lowermost position where first arrow A1, which directs to the side of the word "TRIP", is visible from window 24. Subsequently, when the circuit is restored to normal condition, since the magnetic attractive force between armature 12 and the electromagnet has been eliminated, the right arm of armature 12 is pulled by second tension spring 13 to separate from the electromagnet causing the left arm of armature 12 to separate from pin 9. At this time, the left arm of first crank C1 is rotated by the torsion spring installed on first stationary pivot P1 to the position shown in Fig. 2. Manual switch 200 may be then reset. To reset manual switch 200, firstly, referring to Fig. 6, manual switch 200 is switched off so that the magnetic poles N-S of first permanent magnet M1 can rotate on a horizontal plane, thereby moving away from registry with the magnetic poles S-N of first magnetic block 61. First magnetic block 61 thus falls to its lowermost position. Secondly, manual switch 200 is switched on so that first magnetic block 61 is attracted by first permanent magnet M1 back to its uppermost position. On the other hand, referring to Fig. 7, when manual switch 200 is switched off, push rod 17 will be moved from the position shown in the phantom lines to the position shown in the solid lines. Longitudinal arm 192 of forked rotary member 19 is thus pushed to move from the position shown in phantom lines to the position shown in solid lines so as to turn forked rotary member 19 upwardly by the assistance of third tension spring 23, thereby permitting second magnetic block 18 to fall back to its lowermost position due to the fact that the magnetic attractive force is eliminated. Then, when manual switch 200 is switched on, push rod 17 can't contact longitudinal arm 192 of forked rotary member 19. Thus, the circuit breaker can be completely restored to the normal condition shown in Fig. 2. Referring to Fig. 5, when an emergency is encountered by the circuit, manual switch 200 can be instantly switched off so as to open the circuit. In operation, when manual switch 200 is switched off, slidable rotary member 6 falls to its lowermost position, as described above. Since stopper 8′ blocks fifth crank C5, T-shaped crank C3′ can't rotate. Thus, the downward movement of slidable rotary member 6 and hence third coupler L3 will cause third crank C3 and first coupler L1 to turn downwardly so that second crank C2 is rotated clockwise to separate movable contact 4 away from stationary contact 2. It should be understood that the upper wall of casing 1 is preferably provided with bridging magnets B1 and B2 respectively disposed between first permanent magnet M1 and first magnetic block 61 as well as between second permanent magnet M2 and second magnetic block 18 in order to concentrate the magnetic flux to thus enhance the attractive force therebetween. In addition, longitudinal and horizontal slide slots S1 and S2 are respectively used to facilitate smooth movement of first and second magnetic blocks 61, 18 at the very inception of starting. Alternatively, the stop device may be replaced with other arrangement, such as a bi-metal device or other electromagnetic relays. Referring to Fig. 8, which shows another embodiment of this invention. The second embodiment is similar to the first embodiment in construction except that it has a simpler automatically indicating device. In Figs. 2 and 8, like parts are indentified by the same reference numerals. In this embodiment, automatically indicating device 300 is completely received sealingly within casing 1 along with linkage 100 and the stop device. T-shaped crank C3' has an elongated intermediate crank arm having a curved end surface on which two arrows A1 and A2 are indicated in a manner the same as the first embodiment.

Claims: A circuit breaker comprising a casing (1), a contact device mounted sealingly in said casing (1) and including a stationary contact (2) and a movable contact (4) normally contacting said stationary contact (2), a lower magnetic member (61) disposed within said casing (1) and capable of moving downwardly to separate said movable contact (4) from said stationary contact (2), and a manual switch (200) including a sub-casing (14) fixed on an upper wall of said casing (1) and an upper magnetic member (M1) movable relative to the lower magnetic member (61) to apply or release a magnetic attractive force between said upper and lower magnetic members (M1,61), characterised in that a linkage (100) is disposed in said casing (1) below the lower magnetic member (61) and is connected to said movable contact (4) and to said lower magnetic member (61), a tension spring (7') interconnects said lower magnetic member (61) and said linkage (100) for biassing said movable contact (4) to separate from said stationary contact (2), a stop device is connected to said linkage (100) to normally prevent movement of said linkage (100), the stop device is responsive to a circuit overload or short-circuit to release said linkage (100) for movement under the force of said tension spring (7') to separate the movable contact (4) from the stationary contact (2), an indicating device (300) is drivable by said linkage (100) to indicate an overload or short-circuit condition, and release of the magnetic attractive force between said upper and lower magnetic members (M1,61) causes said lower magnetic member (61) to pivot downwards and move said linkage (100) to separate said movable contact (4) from said stationary contact (2), the magnetic attractive force between said upper and lower magnetic members (M1,61) being greater than the tension force of said tension spring (7'). A circuit breaker as claimed in Claim 1, characterised in that said stop device comprises a crank (C1) including a left arm formed with a stopper (8') and biased to block part of said linkage (100) for normally preventing said linkage (100) from being moved by said tension spring (7'), and a right arm having a free end which is provided with a pin (9); an electromagnet having a core (10') and a coil (11) surrounding said core (10') and electrically connected to an electric wire, and an inverted V-shaped armature (12) disposed rotatably between said electromagnet and said crank (C1) and normally spaced from said electromagnet, said armature (12) including a right arm normally located adjacent said core (10') of said electromagnet and biased away from said electromagnet, and a left arm normally loosely abutting said pin (9) of said crank (C1) to permit said stopper (8') to block said linkage (100) against movement by said tension spring (7'), whereby when the circuit is overloaded or short-circuited said right arm of said armature (12) is attracted toward said electromagnet, said left arm of said armature (12) pushes said pin (9) to rotate said crank (C1) and in turn to separate said stopper (8') from said linkage (100), thereby permitting movement of said linkage (100) to separate said movable contact (4) from said stationary contact (2). A circuit breaker as claimed in Claim 1 or 2, characterised in that a vacuum is maintained within said casing (1). A circuit breaker as claimed in claim 1 or 2, characterised in that said casing (1) is filled with an inert gas. A circuit breaker as claimed in any preceding claim, characterised in that said casing (1) includes a bridging magnet (B1) disposed on said upper wall of said casing (1) between said upper and lower magnetic members (M1,61) to concentrate magnetic flux and thereby enhance the magnetic attractive force between said magnetic members.

Inventors: LEE, WEN-FONG
Applicants: LEE, WEN-FONG
Application year: 1987
Main classification: H01H36
IPC codes: H01H33, H01H71