CN100466140C

CN100466140C - Contact system of breaker

Info

Publication number: CN100466140C
Application number: CNB200710019211XA
Authority: CN
Inventors: 刘洪武; 王云峰; 何艳峰; 管瑞良
Original assignee: Changshu Switchgear Manufacturing Co Ltd
Current assignee: Changshu Switchgear Manufacturing Co Ltd
Priority date: 2007-01-01
Filing date: 2007-01-01
Publication date: 2009-03-04
Anticipated expiration: 2027-01-01
Also published as: CN101030506A

Abstract

The invention is concerned with contact system of breaker belonging to low voltage electrical equipment process field. It relates to a couple of static contact poles, a group of movable contact groupware. The latter relates to a center main branch and a movable contact and a lock framework. The lock framework relates to a couple of the first and the second pintles, and a couple springs and top poles. A couple the first pintles set on the center main branch crossing through the end of top pole, and are axisymmetric by the center of center main branch. A couple the second pintles are axisymmetric by the center of center of movable contact and connect with the front end of top pole. The two ends of a couple springs connect with movable contact and a couple the first pintles. The lock framework keeps the movable contact move to the broken position end and locks it at the broken position. The movable contact and center main branch take hanging designs without revolving axis and keep the balance of two movable contacts and the conduct capability and reliability of breaker.

Description

The contact system of circuit breaker

Technical field

The present invention relates to a kind of contact system of circuit breaker, particularly the contact system of low voltage limit streaming circuit breaker plays the disengagement failure circuit, avoids fault current conducting once more, belongs to the low voltage electrical apparatus technology field.

Background technology

The task that circuit breaker is taken on is a protective circuit system when the circuit abnormal situation; for example when overload or short circuit take place in circuit; between the fixed contact (fixed contact) of the contact system of circuit breaker and movable contact (moving contact), just produce bigger electrodynamic repulsion force; make fixed contact and movable contact separated from one another, use the electric current in the blocking circuit.Yet, though electrodynamic repulsion force helps separate contacts, prevent that prospective short circuit current from reaching maximum, but because this electrodynamic repulsion force results from moment, and strength is stronger, make the movable contact arm scold out bump movable contact arm stop surfaces and falling after rise with very high speed, moving contact on the movable contact arm very likely contacts with fixed contact on the fixed contact arm (also claiming the stationary contact bar) once more, circuit is connected once more, cause short circuit current to reenter Circuits System, even the generation arc reignition, circuit breaker itself and even entire circuit system are caused damage.

For avoiding above-mentioned situation, must take to prevent the technological means of movable contact arm falling, specifically can be by being seen in the pertinent literature, for example US5310971 has disclosed a kind of rotary contact assembly (also claiming movable contact assembly) that utilizes friction between cam surface and the spring-loaded pin to reduce the restriction electric current of movable contact arm velocity of rotation when movable contact and fixed contact separation process end (end), its principle is: when the movable contact arm rotates under the electrodynamic repulsion force effect, the energy of movable contact arm is consumed by frictional force, thereby its speed is slowed down; And when the movable contact arm was opened fully, the semi-circular groove on the cam curved surface can make the movable contact arm latch in open position, thereby had prevented the falling of movable contact.But also there is following shortcoming: because of spring-loaded pin forms the process of snap close state owing to there is not guiding parts in the semi-circular groove that falls on the cam curved surface, therefore do not wait or because of the size of two moving contacts on the movable contact arm when the suffered repulsion of two contact arms of movable contact, site error or electrical wear etc. are former thereby cause when structure is asymmetric, pressure for two moving contacts of balance, the geometric center that occurs the movable contact arm in scolding open procedure easily is offset with respect to its back shaft, described pin is difficult to even can't slips into semi-circular groove, cause the unreliable or snap close failure of snap close.

Again, Chinese patent publication number CN1848346A recommends to have a kind of contact system of circuit breaker, and the structure of the movable contact assembly of being recommended is: extending one piece of outwards outstanding bayonet lock by the pivot pin hub setting in the side side by the movable contact arm on the center of the rotating shaft that operating mechanism drove of circuit breaker; Dispose one piece of clamp, the inner edge of clamp is pressed on the bayonet lock, and forms a pair of forward and backward bayonet socket on the inner edge of clamp, establishes arc transiting surface between the forward and backward bayonet socket, with the rear end hub setting of clamp on axle; Set touch spring, the two ends of touch spring are connect with the front end and the rotating shaft of clamp respectively.When big fault current occurring in the circuit, electrodynamic repulsion force overcomes the effect of spring the movable contact arm is scolded out, and the movable contact arm clockwise rotates in rotating shaft, and the bayonet lock on the movable contact arm slides along the inner edge of clamp simultaneously.Increase along with the rotational angle of movable contact arm, when bayonet lock is crossed arc transiting surface on the clamp and is slided into bayonet socket position, back, the torque that the tension of spring makes the movable contact arm produce on bayonet lock becomes clockwise direction, thereby impel dynamic and static contact to separate with electrodynamic repulsion force, and can block the movable contact arm, keep the released state of dynamic and static contact.But, also there is drawback in this patent, promptly when the suffered repulsion of two contact arms of movable contact arm do not wait or the movable contact arm on when causing that because of two factors such as contact size, site error or electrical wear structure is asymmetric, can't realize regulating to the position of movable contact arm, can't ensure therefore on two moving contacts on the movable contact arm that suffered pressure balance makes the conductivity of circuit breaker, reliability influenced.

Summary of the invention

Task of the present invention is to provide a kind of under the short circuit situation, the movable contact of circuit breaker is arrived smoothly scold out the position terminal and can be latched in reliably and scold the open position end, can make movable contact arm realize adjusting automatically and the contact system of the circuit breaker of moving contact pressure balance on the guarantee activity contact arm again.

Task of the present invention is finished like this, a kind of contact system of circuit breaker, and it comprises a pair of stationary contact bar that is respectively applied for each the tool fixed contact that is electrically connected with binding post; One group of movable contact assembly, this movable contact assembly comprises: a center main bearing that be connected with the operating mechanism of circuit breaker and that rotate under operating mechanism drives, with, one is positioned at the movable contact on the described center main bearing movably, the a pair of movable contact arm of movable contact stretches out from the both sides of described center main bearing, the end of each movable contact arm disposes accordingly with described fixed contact respectively and is used for the moving contact connecting or separate with fixed contact, and, one the clamping mechanism of separation point position end after being used for remaining on movable contact on the center main bearing and the movable contact arm of movable contact is maintained repelling each other out with fixed contact, described clamping mechanism comprises a pair of first, second pivot and a pair of spring and be used for cross-over connection first, the push rod of second pivot, the rear end that a pair of first pivot passes push rod is arranged on the center main bearing, and the center with the center main bearing is symmetrical distribution, a pair of second pivot is fixed on the movable contact with the center of movable contact with being symmetrical distribution, and with the preceding client link of push rod, the two ends of a pair of spring are articulated in respectively on movable contact and a pair of first pivot.

Respectively offer the pair of pivot groove on the wall body that corresponds to each other of center main bearing of the present invention, the every pair of pivot channel is symmetrical distribution with the center of center main bearing, and the two ends of described a pair of first pivot are bearing on the pivot channel that corresponds to each other slidably.

Extended a pair of axle ear on the position of movable contact of the present invention in being in the center main bearing, this is symmetrical distribution to the axle ear with the center of movable contact, the front end of described push rod is provided with first and connects the chamber, the rear end is provided with pivot hole, the middle part of described a pair of second pivot is separately fixed on a pair of axle ear, two ends and first connect the chamber and wear connection, and described first pivot passes in pivot hole.

Of the present invention first connects in U-lag or the elongated slot any one of being shaped as in chamber, and the two ends of described a pair of second pivot extend respectively in first and connect in the chamber and first connect the chamber and wear to connect and connect first and have finite displacement in the chamber.

Pivot channel of the present invention is opened in the edge of the wall body of center main bearing.

Be arranged with one group of isolated part on the axis body of a pair of first pivot of the present invention, this group isolated part comprises first, second, third spacer ring.

Spring of the present invention is any one in two extension springs and the single extension spring.

A kind of contact system of circuit breaker, it comprises a pair of stationary contact bar that is respectively applied for each the tool fixed contact that is electrically connected with binding post; One group of movable contact assembly, this movable contact assembly comprises: a center main bearing that be connected with the operating mechanism of circuit breaker and that rotate under operating mechanism drives, with, one is positioned at the movable contact on the described center main bearing movably, the a pair of movable contact arm of movable contact stretches out from the both sides of described center main bearing, the end of each movable contact arm disposes accordingly with described fixed contact respectively and is used for the moving contact connecting or separate with fixed contact, and, one the clamping mechanism of separation point position end after being used for remaining on movable contact on the center main bearing and the movable contact arm of movable contact is maintained repelling each other out with fixed contact, described clamping mechanism comprises a pair of first, second pivot and a pair of spring and be used for cross-over connection first, the push rod of second pivot, the rear end that a pair of first pivot passes push rod is arranged on the center main bearing, and the center with the center main bearing is symmetrical distribution, a pair of second pivot is fixed on the front end of push rod, and the center with movable contact is be symmetrically distributed ground and movable contact connection, and the two ends of a pair of spring are articulated in respectively on movable contact and a pair of first pivot.

Extended a pair of second on the position of movable contact of the present invention in being in the center main bearing and connected the chamber, should connect the chamber to second and be symmetrical distribution with the center of movable contact, the front end of described push rod is provided with first and connects the chamber, the rear end is provided with pivot hole, the middle part of described a pair of second pivot and a pair of second connects the chamber and wears connection, two ends and first connect the chamber and fix, and described first pivot passes pivot hole.

Of the present invention second connects in U-lag or the elongated slot any one of being shaped as in chamber, and the middle part of described a pair of second pivot extends respectively in second and connects in the chamber and second connect the chamber and wear connection, and connects second and to have finite displacement in the chamber; Described first to connect the chamber be to be used for for the fixing fixing hole in the both ends of second pivot.

Advantage of the present invention: by the interaction between first, second pivot and the push rod, in the time of making moving contact and fixed contact be in contact position, the mechanical force moment that spring produces shows as the direction of moving contact being pressed to fixed contact; When scold out dynamic and static contact,, make moving contact can arrive the separation point position end smoothly owing to connect the guide effect of chamber to second pivot; Movable contact arm is near the separation end of travel time, because the effect between the push rod and second pivot, make push rod to movable contact arm have one with the consistent opplied moment of movable contact arm rotation direction, and this moment produces the mechanical force moment that prevention activity contact arm is opened greater than spring, so total moment is consistent with movable contact arm rotation direction, thereby guarantees that movable contact arm remains on the separation point position and do not return; Realizing making movable contact to live with unsettled form ground by a pair of first pivot places between the two corresponding wall bodies of center main bearing, it is the suspension type design that movable contact and center main bearing adopt the irrotationality rotating shaft, make a pair of moving contact on the movable contact arm former thereby when causing that structure is asymmetric because of size, site error or electrical wear etc., automatically the pressure of two moving contacts of balance has guaranteed circuit breaker electric conductivity and reliability.

Description of drawings

Fig. 1 is a first embodiment of the present invention structure chart.

Fig. 2 is a second embodiment of the present invention structure chart.

Fig. 3 is the schematic diagram of the movable contact arm of movable contact shown in Figure 1 when closed mutually with the stationary contact bar.

Schematic diagram when Fig. 4 repels each other out for the movable contact arm of movable contact shown in Figure 1 and stationary contact bar.

Fig. 5 is the schematic diagram of movable contact shown in Figure 2.

Embodiment

Embodiment 1

Ask for an interview Fig. 1, a pair of stationary contact bar 1 is respectively applied for binding post and is electrically connected, and the end of each stationary contact bar 1 is combined with fixed contact 11.The center main bearing 2 that is connected with the operating mechanism of circuit breaker and is driven by operating mechanism is corresponding between a pair of stationary contact bar 1, though among the figure to analyse and observe the wall body that mode has only provided the center main bearing 2 of the right one side, but can not bring puzzlement to understanding, because the identical wall body of a pair of shape and structure constitutes one by a pair of connection post 22, constitute bearing chamber 221 between a pair of connection post 22, a pair of movable contact arm 31 of the movable contact 3 that will mention below is protruding from the accent in bearing chamber 221.Play the edge that the pivot channel 21 of first pivot, 4 guide effects is opened in the wall body of center main bearing 2, be symmetrical distribution, that is to say 180 ° spaced apart with the center of center main bearing 2.The shape of pivot channel 21 both can be that U-lag also can be the groove such as the dovetail groove of rectangular channel or other similar type, because the both sides wall body of center main bearing 2 is all to have offered the fully corresponding pivot channel 21 in a pair of position on the wall body of the left and right sides, therefore the two ends of a pair of first pivot 4 just can probe in pivot channel 21, and can move about, promptly a pair of first pivot 4 can be made finite displacement in the flute length scope of pivot channel 21.The middle part correspondence of movable contact 3 is at 221 positions, described bearing chamber, its a pair of movable contact arm 31 should be protruding from the both sides accent in bearing chamber 221 as described above, until corresponding to aforesaid a pair of stationary contact bar 1, so that ensure that the moving contact 311 on a pair of movable contact arm 31 is corresponding with the fixed contact 11 on a pair of stationary contact bar 1.

In the present embodiment, the applicant with a pair of second pivot of being recommended 7 be arranged on 3 of movable contacts corresponding to or claim to be positioned on the position of center main bearing 2, specifically be on movable contact 3, respectively to extend a pair of axle ear 313, and guarantee that this is symmetry and is the diagonal angle distribution the center of axle ear 313 with movable contact, the middle part of a pair of second pivot 7 is installed with on (interting) a pair of axle ear 313, and the two ends of second pivot 7 slightly lean out an ear 313 and are presented to first of push rod 6 front ends and connect in the chamber 62.That is recommended in the present embodiment first connects chamber 62 and is the U-lag of open-ended, if U-lag is become elliptical slot that seals or the rectangular channel that seals, should be considered as equivalence so.Second pivot 7 can be made finite displacement in the flute length scope, promptly foregoing have spacing moving.Need to prove, present embodiment 1 and below all to have adopted the center of rotation with moving contact 3 among the embodiment 2 that will mention be symmetrically arranged two pairs of push rods 6, if every pair of push rod 6 constitutes with one respectively, also can realize effect of the present invention, so can not limit the present invention with the variation of the version of push rod 6.

With the location status shown in scheming is example, be processed with extension spring groove 312 respectively at the upside of a movable contact arm 31 and the downside of another movable contact arm 31, an end that shows as a pair of spring 5 of two extension spring forms is hung respectively on a pair of extension spring groove 312, the other end is then hung respectively on a pair of first pivot 4, the middle part of every first pivot 4 is a pair of push rod 6 and first for sheathed two pieces, second, the

3rd spacer ring

41,42,43, also promptly by first,

second spacer ring

41,42 and second, the 3rd spacer ring 43 separates two pieces of push rods 6, wherein one piece of push rod 6 is positioned at first, second spacer ring 41, between 42, another piece push rod 6 is positioned at second, the 3rd spacer ring 42, between 43.The pivot hole 61 of push rod 6 rear ends can be around the revolution of first pivot 4, and first size that connects chamber 62 of push rod 6 front ends should satisfy for the axle head of second pivot 7 hold into degree.Need to prove, if change the spring 5 of the two extension spring forms in the present embodiment into single extension spring form, and the extension spring groove 312 that changes on the movable contact arm 31 is extension spring hole (spring fixed hole), one end hook of the spring 5 of single extension spring form is put in the extension spring hole, the other end is fixed on first pivot 4, so also should be considered as equivalence, so can not limit the present invention with the variation of the version of spring 5.

By above-mentioned assembling as can be known, movable contact 3 be by a pair of first pivot 4 and be aided with spring 5 effect and with vacant state ground or claim with suspension type be located on the center main bearing 2, and do not resemble prior art for example CN1848346A instruction with the center and center main bearing 2 (this patent claim rotating shaft) direct hub setting of bearing pin with movable contact 3 (this patent claims movable feeler lever), therefore, there is size even moving contact 311 occurs, site error or when causing the asymmetric situation of structure because of electrical wear, still the pressure of a pair of moving contact 311 of autobalance well, guarantee with a pair of fixed contact 11 between contact effect, embody circuit breaker conductivity and reliability.

Embodiment 2

Ask for an interview Fig. 2 and Fig. 5, in the present embodiment, the applicant has adopted that to connect chamber 62 fixing with first of a pair of push rod 6 front ends respectively with the two ends of a pair of second pivot 7, the structure that this moment, first on each push rod 6 connected chamber 62 becomes two ends that are used for for second pivot 7 by the U groove of embodiment 1 or elongated slot and interts fixing fixing hole, and change the axle ear 313 among the embodiment 1 into second and connect chamber 314 (Fig. 5 is clear to be shown), the middle part of a pair of second pivot 7 is contained in second and connects on the chamber 314.Connecting chamber 314 for second, both can adopt the U-lag of the open-ended that is provided by this example, also can be elliptical slot that seals or the rectangular channel that seals, and makes finite displacement for second pivot 7 at the flute length extent and scope.By the description of present embodiment as can be known,, have two kinds of forms in the present invention, promptly be installed with at movable contact 3 (embodiment 1) and push rod 6 both and appoint and select on the one for the position arrangement of second pivot 7.All the other are with the description to embodiment 1.

Because embodiment 2 is in one's power and the course of action of the contact system of circuit breaker of the present invention that provided by Fig. 2 and Fig. 5 is identical with embodiment 1, therefore the applicant is only in conjunction with Fig. 2, Fig. 3 narrates course of action of the present invention, when circuit is in normal condition, a pair of moving, quiet 311,11 are in the state of closing that touches shown in Figure 2, two axle heads of second pivot 7 are located in first of push rod 6 front ends respectively and connect in the chamber 62, but and first connect between the bottom in chamber 62 and do not have active force, because the effect of spring 5, the two ends of first pivot 4 are pressed on the bottom land of pivot channel 21, the other end of spring 5 acts on the movable contact arm 31, produce one and be directed downwards the power A that draws along spring 5, this pulling force produces a moment, guarantees the contact pressure of moving contact 311 and fixed contact 11.

When circuit was short-circuited, short circuit current flow through stationary contact bar 1 and movable contact 3, produces electrodynamic repulsion force between the two, and this electrodynamic repulsion force becomes the thrust that helps movable contact 3 to rotate.This moment, the tension of spring 5 was presented as the countertorque that hinders movable contact 3 rotations.In movable contact 3 rotating process, second pivot 7 is shifted to bottom land from first free position that connects chamber 62 of push rod 6, and the arm of force of spring 5 pulling force is also reducing gradually.When movable contact 3 rotates certain position, second pivot 7 begins to contact with first bottom land that connects chamber 62 of push rod 6, and make the upwards jack-up of pivot 4 of winning by

push rod

6,6 pairs of movable contacts 3 of push rod this moment have the power B of an effect, its effect shows as the moment that stops movable contact 3 to be opened, and countertorque was actually by two parts and formed this moment: the opplied moment of the countertorque of

spring

5 and 6 pairs of movable contacts 3 of push rod.Along with the continuation of rotating, the acting force arm of power A reduces, and the acting force arm of power B also reduces, and total countertorque reduces.Be rotated further, the action direction line of power B passes the pivot of movable contact 3, and this moment, the opplied moment of power B was 0.Be rotated further from this position, the opplied moment of power B begins to transfer to and the consistent moment of movable contact 3 rotation directions, near open position, the moment values of power B is greater than the moment values of power A, this moment, total reaction square direction was consistent with movable contact 3 rotations, made movable contact 3 can remain on open position and did not return.

Adopt the circuit breaker tool of contact system of the present invention to have an enormous advantage, in closure, the countertorque of spring 5 provides the contact pressure of dynamic/static contact necessity; Scolding out for the previous period the resistance of countertorque for stoping contact to be scolded out; In the back a period of time of scolding out, countertorque is the moment consistent with the moving contact rotation direction, prevents that described movable contact 3 fallings from causing that electric arc triggers again.And this structure can achieve the above object to movable contact 3 snap closes without any need for other auxiliary components.

Claims

1, a kind of contact system of circuit breaker, it comprises a pair of stationary contact bar (1) and one group of movable contact assembly that is respectively applied for each the tool fixed contact (11) that is electrically connected with binding post,

This movable contact assembly comprises:

One center main bearing (2) that be connected with the operating mechanism of circuit breaker and that under operating mechanism drives, rotate; With,

One is positioned at the movable contact (3) on the described center main bearing (2) movably, the a pair of movable contact arm (31) of movable contact (3) stretches out from the both sides of described center main bearing (2), and the end of each movable contact arm (31) disposes accordingly with described fixed contact (11) respectively and is used for the moving contact (311) connecting or separate with fixed contact (11); And,

One is used for movable contact (3) is remained on the clamping mechanism of the separation point position end after center main bearing (2) is gone up and make the movable contact arm (31) of movable contact (3) to maintain to repel each other out with fixed contact (11);

It is characterized in that,

Described clamping mechanism comprises a pair of first, second pivot (4,7) and a pair of spring (5) and be used for cross-over connection first, second pivot (4,7) push rod (6), the rear end that a pair of first pivot (4) passes push rod (6) is arranged on the center main bearing (2), and the center with center main bearing (2) is symmetrical distribution, a pair of second pivot (7) is fixed on the movable contact (3) with the center of movable contact (3) with being symmetrical distribution, and with the preceding client link of push rod (6), the two ends of a pair of spring (5) are articulated in respectively on movable contact (3) and a pair of first pivot (4).

2, the contact system of circuit breaker according to claim 1, it is characterized in that respectively offering pair of pivot groove (21) on the wall body that corresponds to each other of described center main bearing (2), every pair of pivot channel (21) is symmetrical distribution with the center of center main bearing (2), and the two ends of described a pair of first pivot (4) are bearing on the pivot channel (21) that corresponds to each other slidably.

3, the contact system of circuit breaker according to claim 1, it is characterized in that having extended on the position of described movable contact (3) in being in center main bearing (2) a pair of axle ear (313), this is symmetrical distribution to axle ear (313) with the center of movable contact (3), the front end of described push rod (6) is provided with first and connects chamber (62), the rear end is provided with pivot hole (61), the middle part of described a pair of second pivot (7) is separately fixed on a pair of axle ear (313), two ends and first connect chamber (62) and wear connection, and described first pivot (4) passes in pivot hole (61).

4, the contact system of circuit breaker according to claim 3, it is characterized in that described first connects in U-lag or the elongated slot any one of being shaped as in chamber (62), the two ends of described a pair of second pivot (7) extend respectively in first and connect in the chamber (62) and first connect chamber (62) and wear to connect and connect in the chamber (62) first and have finite displacement.

5, the contact system of circuit breaker according to claim 2 is characterized in that described pivot channel (21) is opened in the edge of the wall body of center main bearing (2).

6, according to the contact system of the described circuit breaker of arbitrary claim in the claim 1 to 3, it is characterized in that being arranged with one group of isolated part on the axis body of described a pair of first pivot (4), this group isolated part comprises first, second, third spacer ring (41,42,43).

7, the contact system of circuit breaker according to claim 1 is characterized in that described spring (5) is any one in two extension springs and the single extension spring.

8, a kind of contact system of circuit breaker, it comprises a pair of stationary contact bar (1) and one group of movable contact assembly that is respectively applied for each the tool fixed contact (11) that is electrically connected with binding post,

This movable contact assembly comprises:

It is characterized in that,

Described clamping mechanism comprises a pair of first, second pivot (4,7) and a pair of spring (5) and be used for cross-over connection first, second pivot (4,7) push rod (6), the rear end that a pair of first pivot (4) passes push rod (6) is arranged on the center main bearing (2), and the center with center main bearing (2) is symmetrical distribution, a pair of second pivot (7) is fixed on the front end of push rod (6), and the center with movable contact (3) is be symmetrically distributed ground and movable contact (3) connection, and the two ends of a pair of spring (5) are articulated in respectively on movable contact (3) and a pair of first pivot (4).

9, the contact system of circuit breaker according to claim 8, it is characterized in that having extended a pair of second on the position of described movable contact (3) in being in center main bearing (2) connects chamber (314), should connect chamber (314) to second and be symmetrical distribution with the center of movable contact (3), the front end of described push rod (6) is provided with first and connects chamber (62), the rear end is provided with pivot hole (61), the middle part of described a pair of second pivot (7) and a pair of second connects chamber (314) and wears connection, it is fixing that two ends and first connect chamber (62), and described first pivot (4) passes pivot hole (61).

10, the contact system of circuit breaker according to claim 9, it is characterized in that described second connects in U-lag or the elongated slot any one of being shaped as in chamber (314), the middle part of described a pair of second pivot (7) extends respectively in second and connects in the chamber (314) and second connect chamber (314) and wear connection, and connects in the chamber (314) second and to have finite displacement; Described first connects chamber (62) for being used for for the fixing fixing hole in the both ends of second pivot (7).