EP0827173B1

EP0827173B1 - Circuit breaker

Info

Publication number: EP0827173B1
Application number: EP96906042A
Authority: EP
Inventors: Haruhisa Toda; Kohei Kurata; Sinsaku Yamasaki
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1996-03-15
Filing date: 1996-03-15
Publication date: 2006-10-18
Anticipated expiration: 2016-03-15
Also published as: KR100336946B1; JP3814671B2; EP0827173A4; WO1997035333A1; KR19990008310A; DE69636639T2; DE69636639D1; EP0827173A1; TW353756B

Abstract

A circuit breaker having a small-sized handle arm (59), wherein a handle (62) is prevented from moving to the open circuit position when a movable contact (44a) and a stationary contact (43a) are fused. A toggle link mechanism (58) includes a link (54) opposed to the handle, and the link (54) is provided with a cam (54a). When the handle (62) is moved to the open circuit position at the time of fusing of the contacts, the cam (54a) is engaged with a bent portion (59a) of the handle arm (59) and prevents the movement of the handle (62) to the open circuit position.

Description

This invention relates to a circuit interrupter.

BACKGROUND ART

Fig. 11 is a sectional view illustrating a conventional circuit interrupter disclosed in Japanese Utility Model Publication No. 1-42286. In this figure, the reference numeral 1 is a cover and 2 is a base, both of which are made of a synthetic resin. 3 is a housing composed of the cover 1 and the base 2, 4 is a stationary contact secured to the base 2 and having at one end thereof a terminal portion 5 for allowing an external conductor (not shown) to be connected thereto and at the upper surface of the other end thereof a stationary contact element 6. 7 is a movable contact having a movable contact element 8 opposing to the stationary contact element 6, 9 is a movable contact arm pivotally supporting the movable contact 7 by a pivot pin 10, 11 is a contact pressure spring disposed between the movable contact arm 9 and the movable contact 7 for always biasing the movable contact 7 toward the stationary contact element 6, 12 is a crossbar made of an electrically insulating material for connecting each of the movable contact arms 9 disposed in parallel for all of the poles. 13 is an arc extinguishing device for extinguishing an electric arc generated between the contact elements 6 and 8 and is provided with a plurality of arc extinguishing magnetic plates 15 inside of a pair of arc extinguishing side plates 14. 16 is a lower link pivotally supported at its one end to the movable contact arm 9 by a shaft 17, 18 is an upper link pivotally connected at one end to the other end of the lower link 16 and at the other end to a cradle 19 by shafts 20 and 21, respectively. 22 is a toggle link mechanism composed of the lower link 16, the upper link 18 and the shaft 20, the shaft 20 serving as a knee. 23 is a handle arm supported at its one end (not shown) to be pivotable to a predetermined position relative to the toggle link mechanism 22, 24 is a toggle spring made of a synthetic resin and operable from the exterior of the cover 1 and is interconnected to the handle arm 23. 27 is a bimetal connected to the movable contact 7, 28 is a stationary iron core secured to the bimetal 27, 29 is a movable iron core disposed opposite to the stationary iron core 28, 30 is a trip bar rotatable and having the movable iron core 29 secured thereto, 31 is a rotatable latch usually engaged at one end by the cradle 19 and at the other end by the trip bar 30, 32 is a cradle shaft for rotatably supporting the cradle 19, 33 is a stopper for latching the cradle 19 upon the tripping and is engaged with a frame 34 to be secured thereto. The frame 34 also supports the support point or the fulcrum for positioning the cradle shaft 32 and for pivoting the latch 31.
The operation will now be described. If the contact elements are in the open position as shown in Fig. 12, when the handle 26 is moved to the closed position (to the right), the toggle mechanism 22 is extended to bring the movable contact element 8 into contact with the stationary contact element 6 which is the closed position shown in Fig. 11. Then, when the handle 26 is turned into the open position (to the left), the toggle mechanism 22 is collapsed to cause the movable contact element 8 to separate from the stationary contact 6 into the open position shown in Fig. 12. On the other hand, when an overcurrent flows through the circuit in the above described closed position shown in Fig.11, the bimetal 27 or the movable iron core 29 is actuated to release the engagement between the cradle 19 and the latch 31 (see Fig.13), so that the cradle 19 is rotated in the clockwise direction about the cradle shaft 32. Therefore, the connection point between the cradle 19 and the upper link 18 or the center of the shaft 21 moves beyond the line of action of the toggle spring 24, then the toggle link mechanism 22 is collapsed by the spring force of the toggle spring 24, so that the cross bar 12 causes the movable contact elements 8 of all the poles together to separate from the stationary contact elements 6 in each pole, reaching to the tripped position shown in Fig. 13.
With the circuit interrupter as above discussed, in an unlikely event that the movable contact 7 is welded in the closed position by an abnormal current and a non-separable state takes place, by moving the handle 26 into the closed position as shown in Fig. 14, the toggle spring 24 is expanded beyond the normal length allowing the handle 26 to be moved and held in the open position, where the open position indicated by the handle 26 does not correctly reflect the actual closed position of the movable contact 7.
Also Japanese Patent Publication No. 1-39176 discloses a conventional circuit interrupter in which the operating lever (corresponding to the handle arm) and the movable contact assembly engages each other when the contact elements are welded together so as not to permit the handle to move into the open position.
In the above circuit interrupter, while it is possible to prevent the handle from moving into the open position when the movable contact is welded in the closed position by an abnormal current, there was a problem that the handle arm becomes large because the handle arm is arranged to directly engage the movable contact assembly.
The document "US-A-5 304 765" discloses a circuit interrupter according to the preamble of claim 1.

SUMMARY OF THE INVENTION

The invention is defined in claim 1, and further modifications thereof are defined in the dependent claims.
According to the present disclosure, the circuit interrupter comprises, within an insulating housing composed of a base and a cover, a stationary contact, a movable contact separable from and opposing to said stationary contact, a toggle mechanism for driving said movable contact, a handle arm pivotally supported at a predetermined position relative to said toggle mechanisms, a trip device responsive t an overcurrent to actuate said toggle mechanism, and is characterized by a prevention portion engageable with said handle arm for preventing said handle to move into the open position. This allows the handle to be prevented from moved to the open position and the handle arm to be made relatively small-sized
The prevention portion may be a cam portion disposed in a handle side link of the toggle link mechanism for engaging with the handle arm upon the welding of said movable contact and said stationary contact to prevent the handle from moving into the open position. This allows the handle to be prevented from moving in the direction of the open position and the handle arm to be made relatively small.
The prevention portion which engages the handle arm of the handle side link of the toggle mechanism may be formed as an arc-shaped cam portion having its center on the pivot point of the handle side link. Since the pivot point of the handle side link and the center of the cam potion coincide, even when the handle side link pivots, the handle does not move in the direction toward the open position beyond the position in which it engages the cam portion, so that the welding of the contact elements can be clearly indicated.
Also, the cam portion which engages the handle arm of the handle side link may comprise a second cam portion, which engages the handle arm in the first period of the handle moving process in which the handle is being moved toward the open position upon the welding of the movable contact element to the stationary contact element, and a first cam portion, which engages the handle arm in the last period of the handle moving process in which the handle is being moved toward the open position upon the welding of the movable contact element to the stationary contact element. Therefore, when the circuit interrupter is moving the handle from the closed position to the open position into counterclockwise direction, the bent engaging portion of the handle arm engages the second cam portion of the handle side link, thereby to cause the connection portion between the handle side link and the movable contact side link to quickly collapse, whereby the opening operation can be made more reliable. When the weld state between the contact elements is weak, the movable contact can be pulled up by the clockwise moment to separate the contact elements. The further movement of the handle arm causes engagement with the first cam portion, whereby the handle is prevented from further moving toward the open position.
Also, the cam portion which engages the handle arm of the handle side link may be defined by a first cam portion of an arc having its center on the fulcrum of the handle side link and a second cam portion of an arc having its center at a position shifted from the fulcrum of the handle side link. Therefore, when the circuit interrupter is moving the handle from the closed position to the open position in the counterclockwise direction, the bent engaging portion of the handle arm engages the second cam portion of the handle side link, thereby to cause the connection portion between the handle side link and the movable contact side link to quickly collapse, whereby the opening operation can be made more reliable. When the weld state between the contact elements is weak, the movable contact can be pulled up by the clockwise moment to separate the contact elements. The further movement of the handle arm causes engagement with the first cam portion, whereby the handle is prevented from further moving toward the open position.
A further disclosed embodiment of the circuit interrupter may comprise, within an insulating housing composed of a base and a cover, a stationary contact, a movable contact separable from and opposing to said stationary contact, a cross bar connecting one end of the movable contact together, a toggle mechanism for driving the movable contact, a handle arm pivotably supported at a predetermined position relative to said toggle mechanism, a handle moving in relation to the handle arm and a trip device responsive to an overcorrect to actuate said toggle mechanism, and may be characterized by a stopper for engaging between the cross bar and the handle arm upon the welding of the movable contact element of the movable contact to the stationary contact element of the stationary contact for preventing the handle to move into the open position. This allows the handle to be prevented from moved to the open position and made relatively small-sized, and the stopper to abut against the rigid cross bar which is not easily destroyed, so that the mechanism is strong.
In this embodiment, a torsion spring for causing the stopper to always engage the handle arm may be provided. Thus, the handle arm is always biased in the clockwise direction to ensure the movement of the handle into the direction of the closed position, whereby position of the contact element of the circuit interrupter is ensured to precisely correspond to the state indicated by the handle.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:-

Fig. 1 is a sectional side view of a circuit interrupter which is the first embodiment of the present invention, shown in the closed position;
Fig. 2 is a sectional side view of the main portion showing the open position of the circuit interrupter shown in Fig. 1;
Fig. 3 is a sectional side view of the main portion showing the tripped position of the circuit interrupter shown in Fig. 1;
Fig. 4 is a sectional side view showing the position in which the handle is moved into the open position while the contact elements of the circuit interrupter shown in Fig. 1 is welded;
Fig. 5 is a sectional side view of the circuit interrupter which is the second embodiment of the present invention;
Fig. 6 is an enlarged sectional side view of the main portion of the circuit interrupter shown in Fig. 5 with its contact elements welded and with its handle moved in the open position;
Fig. 7 is an enlarged sectional side view showing the position in which the toggle link mechanism is moved from the position shown in Fig. 6;
Fig. 8 is a sectional side view of the circuit interrupter in the closed position which is the third embodiment of the present invention;
Fig. 9 is a sectional side view of the circuit interrupter shown in Fig. 8 with its contact elements welded and with its handle moved in the open position;
Fig. 10 is a sectional side view of the circuit interrupter of the fourth embodiment of the present invention;
Fig. 11 is a sectional side view of a conventional circuit interrupter in the closed position;
Fig. 12 is a sectional side view of the conventional circuit interrupter in the open position;
Fig. 13 is a sectional side view of the conventional circuit interrupter in the tripped position; and
Fig. 14 is a sectional side view of the conventional circuit interrupter in the position with the contact elements welded and the handle moved in the open position.

DETAILED DESCRIPTION

Fig. 1 is a sectional side view of a circuit interrupter which is the first embodiment of the present disclosure showing the closed position with its one portion cut away to show the interior. Fig. 2 is a sectional side view of the main portion showing the open position of the circuit interrupter shown in Fig. 1, and Fig. 3 is a sectional side view of the main portion showing the tripped position of the circuit interrupter shown in Fig. 1. In the figures, 40 is a cover and 41 is a base, both made of a synthetic resin. 42 is a housing composed of the cover 40 and the base 41, 43 is a stationary contact secured to the base 41 and having a stationary contact element 43a. 44 is a movable contact having a movable contact element 44a opposing to the stationary contact element 43a and is pivotally supported by a pivot pin 45. 46 is a cross bar made of an insulating material connected to one end of the respective movable contacts 44 provided at each poles. 47 is a contact pressure spring disposed between the movable contact 44 and the cross bar 46 for always biasing the movable contact 44 toward the stationary contact element 43a. 48 is a flexible conductor with its one end connected to the movable contact 44 and the other end connected to a trip device (not shown). 49 is an arc extinguishing device for extinguishing an electric arc generated between the contact elements 43a and 44a and is provided with a plurality of arc extinguishing magnetic plates 51 disposed within a pair of arc extinguishing side plates 50.
52 is a movable contact side link (hereinafter simply referred to as a lower link) pivotally connected at one end to the cross bar 46 by a shaft 53, 54 is a handle side link (herein after simply referred to as an upper link) pivotally connected at one end to the other end of the lower link 52 and at the other end to a cradle 55 by shafts 56 and 57, and a prevention portion is provided at the upper link 54. This prevention portion is defined by a cam portion 54a of an arc section having a radius of R and a center at the center of the shaft 57 which is the fulcrum of the upper link 54. 58 is a toggle link mechanism composed of the lower link 52, the upper link 54 and the shaft 56, the shaft 56 being a knee portion. 59 is a handle arm having a bent engaging portion 59a and pivotally supported at one end 59b as a pivot point on an unillustrated frame so as to be pivotable into a predetermined position relative to the toggle link mechanism 58. 60 is a toggle spring connected at one end to the handle arm 59 through a spring holding pin 61 and the other end to the shaft 56. 62 is a handle made of a synthetic resin and operable from the outside of the cover 40 cooperable with the handle arm 59. 63 is a latch, which comprises a latch engaging portion 63a engaging the cradle 55 and a recess portion 63b in which a latch support shaft 64 is received, and engageable with the trip device (not shown) to be rotated about the latch support shaft 64. 65 is a cradle support shaft pivotally supported by the unillustrated frame, and 66 is a stopper pin for the upper link 54 and the movable contact 44.
The operation will now be described. In Fig. 2, wherein the contact elements are in the open position, when the handle 62 is turned to the closed position (to the right) in the state where the cradle 55 is latched by the latch 63, the toggle mechanism 58 is extended to cause the movable contact element 44a to contact with the stationary contact element 43a to bring the mechanism into the closed position shown in Fig. 1. Then, when the handle 62 is turned toward the open position (to the left) and when the axis of the toggle spring 60 moves beyond the line of action (dead point) passing through the shafts 56 and 57, the toggle link mechanism 58 collapses to pull up the lower link 52 to separate the movable contact element 44a from the stationary contact element 43a to bring the open position shown in Fig. 2. On the other hand, when an overcorrect flows through the circuit in the closed position shown in Fig. 1, the trip device (not shown) actuates to release the engagement between the cradle 55 and the latch 63 (see Fig. 3), the cradle 55 is rotated in the clockwise direction about the cradle support shaft 65. Therefore, the connection point between the cradle 55 and the upper link 54 or the point of the shaft 57 is moved beyond the line of action of the toggle spring 60, so that the toggle link mechanism 58 collapses due to the spring force of the toggle spring 60, and the movable contact element 44a is separated from the stationary contact element 43a for each pole concurrently, thereby to become the tripped position shown in Fig. 3.
Fig. 4 illustrates the state in which a pulse-like massive current for example flows in the closed position so that a welding phenomenon took place between the stationary contact element 43a and the movable contact element 44a while the engagement between the cradle 55 and the latch 63 is not released, whereby the movable contact element 44a fails to separate from the stationary contact element 43a. In this position, the toggle link mechanism 58 is held in the closed position, and when the handle 62 is moved in the counterclockwise direction toward the open position in order to put the circuit interrupter in the open position as required for the inspection and maintenance as illustrated in Fig. 4, then the toggle spring 60 is expanded to allow the handle arm 59 to be rotated in the counterclockwise direction into the open position. However, while the handle 62 is being moved in the counterclockwise direction, the bent engaging portion 59a of the handle arm 59 abuts against and engages the cam portion 54a of the upper link 54 of the toggle link mechanism 58 held in the closed position, thereby to preventing the handle arm 59 from further moving toward the open position.
The arrangement may be such that the bent engaging portion 59a of the handle arm 59 abuts against and engages the lower link of the toggle link mechanism 58 maintained at the closed position. Thus, since the toggle mechanism 58 and the preventing portion or, more particularly, the cam 54a and the bent engaging portion 59a of the handle arm 59 abut against and engage with each other, the handle arm can be made smaller as compared to that in the case where the movable contact assembly and the handle arm abut against and engage with each other.
Fig. 5 is a sectional side view of the circuit interrupter which is the second embodiment of the present disclosure with its one portion removed to show the interior thereof and illustrates the state in which the handle is moved toward the open position while the contact elements of the circuit interrupter are welded to each other. Fig. 6 is an enlarged sectional side view of the main portion of the circuit interrupter shown in Fig. 5 with its contact elements welded and with its handle moved in the open position. In the figures, 100 is an upper link, the configuration of which cam portion engaging the bent engaging portion 59a of the handle arm 59 comprises a first cam portion 100a having a radius of curvature R1 with its center at the center C1 of the shaft 57 and a second cam portion 100b having a radius of curvature R2 with its center at a position as the center C2 shifted by a distance L from the center C1 of the shaft 57 toward the lower link 52. For example, in the case of a circuit interrupter of 400 A (Amper) frame, the position of the center C2 is within the range of L = 2.5 ~ 3 mm and at a rotational angle θ = about 20° as measured in the clockwise direction relative to a dot-and-dash line passing through the center C1 and the center C3 of the shaft 56.
In the state shown in Fig. 5, when a pulse-like massive current for example flows in the closed position and a welding phenomenon took place between the stationary contact element 43a and the movable contact element 44a while the engagement between the cradle 55 and the latch 63 is not released, whereby the movable contact element 44a fails to separate from the stationary contact element 43a. In this position, when the handle 62 is moved in the counterclockwise direction toward the open position in order to put the circuit interrupter in the open position as required for the inspection and maintenance, as illustrated in the detailed enlarged, sectional side view of the main portion of Fig. 6, then the toggle spring 60 is expanded to allow the handle arm 59 to be rotated in the counterclockwise direction into the open position. However, while the handle is being moved in the counterclockwise direction or at the first period in which the handle 62 is being moved in the direction toward the open position, the bent engaging portion 59a of the handle arm 59 abuts against and engages the cam portion 100b of the upper link 100. At this time, a pressing force F2 toward the center C2 acts at the contact point between the second cam portion 100b and the bent engaging portion 59a of the handle arm 59. Since this force F2 is direction toward the center C2, the upper link 100 is subjected to a clockwise moment M = F2 x L about the fulcrum of the center C1 of the shaft 57, causing the shaft 56 connecting the upper link 100 and the lower link 52 to rotate in the direction of an arrow D. While this causes the lower link 52 to be lifted up in the direction of an arrow E as shown in Fig. 7 and the movable contact 44 is apt to separate from the stationary contact 43, the movable contact is permitted to move only by an amount corresponding to a gap G (see Fig. 6) and stay there because the contact elements are welded together. Since the portion of the shaft 56 bends, the bent engaging portion 59a of the handle arm 59 is moved to the position where it is engaged by the first cam portion 100a and, at this time, or at the last period of the movement of the handle 62 into the open position, the pressing force F1 acts at the contacting point between the first cam portion 100a and the handle arm 59 is prevented from moving further toward the open position.
According to the second disclosed embodiment, during the process of the circuit interrupter shifting the handle 62 from the closed position to the open position, the bent engaging portion 59a of the handle arm 59 engages the second cam portion 100b of the upper link 100, to quickly collapse the connection portion between the upper link 100 and the lower link 52, so that the opening operation is more reliable. Also, when the weld is limited only in a small area, the movable contact 44 is lifted up by the clockwise moment M = F2 x L to separate the movable contact element. Also, since the upper link 100 rotates in the direction of collapse and the first cam portion 100a and the bent engaging portion 59a engage with each other, the upper link 100 rotates until the upper link 100 lifts up the movable contact 44, but the handle 62 prevents the upper link 100 to move in the direction of closed beyond the point at which it abuts the cam portion 100a.
Fig. 8 is a sectional side view of the circuit interrupter in the closed position which is the third embodiment of the present disclosure, with one portion thereof removed to show the interior. In the figure, 1 ~ 66 are similar components to those of the above described first embodiment and their explanation is omitted. 70 is a stopper, which is pivotally supported by the stopper support shaft 65 of the cradle 55 and having an arm portion 70a at one end and having a stopper shaft 71 for engaging with the bent engaging portion 59a of the handle arm 59 secured at the other end.
Fig. 9 illustrates the state in which a pulse-like massive current for example flows in the closed position so that a welding phenomenon took place between the stationary contact element 43a and the movable contact element 44a while the engagement between the cradle 55 and the latch 63 is not released, whereby the movable contact element 44a fails to separate from the stationary contact element 43a. In this position, when the handle 62 is moved in the counterclockwise direction from the position shown in Fig. 8 toward the open position in order to put the circuit interrupter in the open position as required for the inspection and maintenance, then the toggle spring 60 is expanded to allow the handle arm 59 to be rotated in the counterclockwise direction into the open position (see Fig. 9). However, while the handle 62 is being moved in the counterclockwise direction, the bent engaging portion 59a of the handle arm 59 causes the rotation of the shaft 71 which is in abutment with the bent engaging portion 59a of the handle arm 59 in the counterclockwise direction, and causes the arm portion 70a of the stopper 70 to rotate in the counterclockwise direction until it abuts against and engages a projection portion 46a of the structurally rigid cross bar 46, whereby the handle arm 59 is prevented from being further moved toward the open position. The handle arm can be made smaller than that used in the conventional design in which the movable contact assembly and the handle arm abut against and engage with each other.
Fig. 10 is a sectional side view of a circuit interrupter. In the figure, 72 is a torsion spring, which is connected to the stopper shaft 71 for causing the stopper shaft 71 to always abut against the bent engaging portion 59a of the handle arm 59 thereby to always biasing the stopper 70 in the clockwise direction.
According to this embodiment, the biasing force of the torsion spring 72 acting on the stopper 70 is a biasing force causing the handle arm 59 and the handle 62 to rotate in the clockwise direction.
The present invention has been made in order to solve the described problem with prior art devices, and advantageously provides an arrangement in which the handle cannot be moved to the open position when the movable contact element and the stationary contact element are welded together and in which the handle arm is relatively small.
Also, another advantage is to provide an arrangement in which the handle cannot be moved to the open position when the movable contact element and the stationary contact element are welded together, the handle arm is relatively small and in which the mechanism is strong.

Claims

A circuit interrupter comprising, within an insulation housing (42) composed of a base (41) and a cover (40), a stationary contact (43), a movable contact (44) separable from and opposing said stationary contact (43), a toggle mechanism (58) for driving said movable contact (44), a handle arm (59) pivotably supported at a predetermined position relative to said toggle mechanism (58), a handle (62) interconnected to said handle arm (59) and a trip device responsive to an overcorrect to actuate said toggle mechanism (58), wherein said handle (62) is prevented from moving into the open position when a stationary contact element (43a) of said stationary contact (43) and a movable contact element (44a) of said movable contact (44) are welded to each other, wherein
said toggle mechanism (58) is provided with a prevention portion (54a) engageable with an engaging portion (59a) of said handle arm (59) for preventing said handle (62) from moving into the open position when said contacts (43, 44) are welded to each other, characterized in that: said prevention portion (54a) is configured to engage said engaging portion (59a) of said handle arm (59) at a position on the same side of said toggle link mechanism (58) as said stationary contact (43) and said moveable contact (44).
A circuit interrupter as claimed in claim 1, wherein said prevention portion (54a) is disposed on a handle side link (54) and comprises a first cam portion (100a) of an arc having its center on the fulcrum of said handle side link (54) and a second cam portion (100b) of an arc having its center at a position shifted from the fulcrum of said handle side link (54) toward a movable contact side link (52).
A circuit interrupter as claimed in claim 2, wherein said second cam portion (100b) engages said handle arm (59) in a first period of the handle moving process in which said handle (62) is being moved toward the open position when said movable contact element (44a) is welded to said stationary contact element (43a), and wherein said first cam portion (100a) engages said handle arm (59) in the last period of said handle moving process.
A circuit interrupter as claimed in claim 1, wherein said handle arm (59) is provided with an engaging portion (59a) bent from the rotational plane of said handle arm (59) to provide a raised surface on the same side of said handle arm (59) as said stationary contact element (43a) of said stationary contact (43) and said moveable contact element (44a) of said moveable contact (44).