GB2161651A - Switch operating mechanism - Google Patents

Abstract

An operating mechanism for a circuit breaker comprises a drive shaft 3 to actuate a movable contact 2 when rotated; a follower lever 25 mounted for rotating about the axis of the drive shaft or about an axis parallel thereto between first (Fig. 4) and second positions; a drive lever 26 rotatably mounted on the drive shaft; a transmission linkage 28, 30 pivotally connected between the drive lever and the follower lever and having at least one toggle knee 31 between the connected ends; a support member 38 for limiting the amount of collapse of the transmission linkage when a latch 43 is engaged therewith so that the follower lever 25 is constrained to follow pivoting movement of the drive lever 26 and for allowing collapse of the linkage 28, 30 when unlatched; a latch member 49 for latching the drive lever 26 or the transmission linkage 28, 30 at a predetermined position when the follower lever 25 is in the second position to hold the follower lever in the second position; and a spring 7 for biasing the follower lever 25 towards the first position. <IMAGE>

Description

SPECIFICATION Operating mechanism for a switchgear This invention relates to an operating mechanism for opening and closing a switchgearsuch as a circuit interrupterora switch.

Figs. 1 to 3 are sectional side views illustrating one example of a conventional operating mechanism, Fig.

1 showing the open position ofthe operating mechan ism, Fig. 2 showing the closed position, and Fig. 3 showing the position ofthe mechanism as it is opening.

In the figures, lisa stationary contact, 2 is a movable contact which contacts and separates from the stationary contact 1 ,thereby opening and closing an electric circuit, and 3 is a pawl shaft on which a pawl lever4 and a drive leverS are securely mounted with a predetermined distancetherebetween. 6 is an electrically insulating rod which is rotatably connected to the pawl lever 4 and the movable contact 2 so as to transmit an operating force from the pawl shaft 3 to the movable contact 2,7 is an opening spring disposed between one end of the pawl lever 4 and a frame (not shown) for biasing the pawl shaft 3 in the clockwise direction,8 is a main link pivotally con nectedtothedrive leverS at one end bya pin 9 and carrying at the other end a roller 10 mounted on a pin 11, 12 is a closure cam mounted on the crankshaft 13 with its outer edge in contact with the roller 10,14 is a trip cam rotatably mounted on a stationary shaft 15, 16 is a connecting link pivoted at one end aboutthe trip cam 14 by a pin 17 and atthe other end to the main link 8 by the pin 11,18 is a roller rotatably mounted on the trip cam 14 by a pin 19,20 is a latch pivoted on the fixed shaft 21 and having one end thereof engageable with the roller 18,22 is a trigger pivoted on the fixed shaft 23 and having one end thereof in engagement with the latch 20, and 24 is a tripping electromagnet having a drive shaft24a which is in engagementwith one end ofthe trigger 22.

Next, the operation ofthe apparatus in Figures 1-3 will be explained. Fig. 1 illustrates the reset position in the open state. In Fig. 1,when a closing command is output, a closure drive mechanism (not shown) drives the crankshaft 13 and the closure cam 12 mounted on the shaft 13 in the counterclockwise direction. This rotation of the closure cam 12 causes the roller 10 which is in contact with the outer periphery ofthe closure cam 12 to be moved in the direction away from the crankshaft 13, andthe roller 10 is moved along an arc aboutthe pin 17 in the counterclockwise direction since the roller 10 is connected to the trip cam 14 through the connecting link 16.Therefore, a drive force is transmitted to the pawl shaft 3 through the main link 8 connected to the roller 10 and the drive lever 5 to rotate the pawl shaft 3 counterclockwise.

This counterclockwise rotation ofthe pawl shaft3 causes the movable contact 2 to be driven toward the stationary contact 1 through the pawl lever 4 con nected to the pawl shaft3 and the insulated rod 6 connected to-the pawl lever 4 to close the contacts 1 and 2. During this series of actions, the opening spring 7 connected to one end of the pawl lever4 is stretched.

The state in which the closing operation has been completed is illustrated in Fig. 2. In Fig. 2, when a circuit opening command is issued, the electromagnet 24 is energized and the drive shaft 24a is drawn upwards in Fig. 2. Then,the trigger 22 which is in engagement with the drive shaft 24a is rotated clockwise so as to disengage from the latch 20. Since the portion of the latch 20 which engages the roller 18 is located abovethefixed shaft 21 in Fig. 2, the latch is always biased in the counterclockwise direction by a force resulting from the tension of the opening spring 7 and is rotated counterclockwise when the trigger 22 is disengaged, thereby disengaging from the roller 18 mounted on the trip cam 14.Since the pawl shaft 3 is biased in the clockwise direction bythe opening spring 7, the roller 10 connected to the pawl shaft3 through the main link 8 is subjected to a force directed toward the right in Fig. 2 due to the relative position of the pawl shaft 3 and the closing cam 12. Therefore, the trip cam 14which in connected to the main roller 10 through the connecting link 16 is always subjected to a counterclockwise rotational force in the closed position, and is rotated counterclockwise when the latch 20 is disengaged. This rotation of the trip cam 14 causes the pin 17 which istheconnecting portionwith the connecting link 1 6to be rotated towards the right in Fig. 2.As a result, a restricting force which restricts the main roller 10 is removed, and the main roller 10 moves to the right. Accordingly, the pawl shaft 3 which is connected to the main roller 10 through the main link8 rotates clockwise, and as the pawl shaft 3 rotates the movable contact 2 connected to the pawl shaft 3 through the pawl lever 4 and the insulated rod 6 is driven toward the circuit open direction. This state is shown in Fig. 3. Thereafter, the trip cam 14 and the latch 20 are rotated clockwise by unillustrated respective energizing mechanisms to be reset as shown in Fig. 1.

As described above, the drive mechanism of the switchgear is usually constructed from a four joint linkage, so that a drive force is transmittedto the movable contact 2 through thefourjoint linkage during the opening operation, and the contact closed state is maintained by holding thefourjoint linkage in a state of tension. To initiate the circuit opening operation, the tension of one portion ofthefourjoint linkage is released,wherebythetensionoftheentire linkage is released, thereby driving the movable contact 2 in the direction of the circuit open position by the opening spring.

As a meansfor releasing the tension, a structure for displacing the fixed joint ofthe four joint linkage is used in the conventional device. More particularly, the tension ofthefour jointlinkage is released by rotating the trip cam 14 counterclockwise upon opening to move in pin 17 to the right in Fig. 2, the pin 17 being one of the fixed joints ofthefourjoint linkage composed of the drive lever5, the main link 8, the connecting link 16, and the trip cam 14.

Therefore, with the above arrangement, shown in The drawing(s) originally filed was (were} informal and the print here reproduced is taken from a later filed formaf copy.

Figs. 1 and 2, the load which acts on the pin 17 significantly varies in accordance with the operation of the four joint link orthe movement ofthe roller 10, and the counterclockwise rotational force acting upon the trip cam 14 therefore also varies greatly. Furth ermore, when the trip cam 14 and the latch 20 are to be operated from the engaging state to the released state under a loaded condition, it is necessary in the conventional design thatthe load acting upon the engaging portion not be excessively high. This is because if an excessive load is applied to the engaging portion, the engaging surface may be deformed and the force needed for driving may be increased, resulting in unreliable operation.Therefore, in accord ance with the conventional design,the arrangement is such thatthe parts such as the trip cam 14, the latch 20, and the trigger 22, are arranged in series so thatthe load on the respective parts gradually decreases.

Therefore, the number of the parts is large, the structure is complicated, and the assembly of the parts requires significant efforts and time.

The present invention was made to remove such disadvantages, and has as its objectthe provision of an operating mechanism foraswitchgearin which a foldable joint is provided in a transmission linkage connecting the drive lever and the follower lever, and the transmission linkage is supported by a support member such thatthe amount of movement of the foldablejoint is not largerthan a predetermined amount, thereby making the mechanism simple and reliable in operation.

BRIEF DESCRIPTION OFTHE DRAWINGS Figs. 1 to 3 are side views showing a conventional operating mechanism, Fig. 1 showing the circuit open position, Fig. 2 showing the circuit closing position, and Fig. 3 showing the position in which the mechan ism is being opened. Figs. 4to 6 are side views showing the operating mechanism of one embodiment ofthe present invention, Fig. 4 showing the circuit open position, Fig. 5 showing the circuit closed position, and Fig. 6 showing the position in which the mechanism is being opening.

One embodiment ofthe present invention will now be described. Figs. 4to 6 are side views illustrating one embodiment ofthe operating mechanism ofthe present invention, of which Fig. 4 shows the open state, Fig. 5 shows the closed state, and Fig. 6 shows the state in which the mechanism is opening.

In the figures, 25 is a follower lever mounted on the pawl shaft 3,26 is a drive lever having secured at one end thereof a boss 27 through which it is rotatably mounted on the pawl shaft3. 28 is a first link rotatably connected to one end ofthefollower lever 25 through a pin 29,30 is a second link which is rotatably connectedat one end to thefirst link 28 through the pin 31 and connected at the other end to the drive lever 26 through a pin 32, the second link 30 having a roller 34 supported by a pin 33 in thevicinity ofthe portion connected to the first link 28.Thefirst link 28 and the second link 30 together constitute a transmission link 35.36 is a spring for biasing the transmission link35 toward the expanded position ofthe transmission link 35,37 is a stopperfor restricting the rotational range of the levers 25 and 26 by abutting against one end of either the fo[lower lever 25 or the drive lever 26,38 is a support member which has a projection 38a and a roller41 pivoted on a pin 40, at one end the other end thereof being rotatably supported by a fixed shaft 39.

In the supported state, the main body portion ofthe support member 38 abuts against the roller34to limit the amount of movement ofthe joint between the first link 28 and the second link 30.42 is a spring for biasing the support member in the counterclockwise direc tion, 43 is a engaging means which is a latch for engaging and disengaging the support member38 and for latching the support member 38 when disengaged.The engaging means 43 is rotatably mounted on a fixed shaft 44 and latches the support member38whenitstip portion abutsagainstthe roller41.45 is a pin secured on the latch 43 for preventing the excessive rotation of the latch 43 beyond a predetermined amount by engaging with the projection 38a when the support member 38 and the latch 43 are engaged. 46 is a triggerwhich is disposed on the latch 43 and which is pushed by the actuation ofthe drive shaft 24a ofthe electromagnet 24to rotate clockwise together with the latch 43,47 is a spring for biasing the latch 43 in the counterclockwise direction, 48 is a roller rotatably mounted on the pin 33,49 is a latch member rotatably mounted on the fixed shaft 50 which engages and disengages from roller 48, and 51 is a spring for biasing the latch member49 in the counterclockwise direction. 1 -7 are components which are identical to those in the previously-described conventional design, an therefore a description thereof is omitted.

The operation ofthe apparatus illustrated in Figures 4-6will nowbedescribed. In Fig. 4,the support member38 engages with the latch 43 and is maintained in a predetermined positon. In this state, when a clockwise rotational force is applied to the drive lever 26 byan unillustrated drive means, the rotational force is transmitted to thefollower lever 25through the transmission linkage 35. Thetransmission linkage 35 is maintained in the state wherein the nodal point which is the pin 31 at the center of the transmission linkage 35 is shifted upwards in Fig. 4.Therefore, when this rotational force isto be transmitted, the linkagetendsto fold further upward, but the roller 34 abuts againstthe main body of the support member 38to preventthe further folding movement. Thus, the transmission linkage 35 transmits the rotational force provided to the drive lever 26to the follower lever 25 with the predetermined folding force and the folded amount maintained. Upon the clockwise rotation of the follower lever 25, the pawl shaft 3 on which the follower lever 25 is mounted also rotates clockwise. As a result,the movable contact 2 is swung towardthe stationary contact 1 by the pawl lever4 and the insulating rod 5to closethecontacts 1 and 2. During this operation, the opening spring 7 mounted atone end of the pawl lever4 is executed and energized. As the drive lever 26 rotates clockwise, the latch member 49 rotates counterclockwise until it engages with the roller 48 in the closed state of the contacts 1 and 2, and the opening mechanism can thereof be maintained in the circuit closed position againstthe opening force of the opening spring 7 even after the drive force biasing the movable contact 2 in the contact closing direction is removed. This condition is shown in Fig. 5. In Fig 5, when a trip command is supplied to this switchgear, the electromagnet 24 is energized and the output shaft 24a protrudes to the rig htto rotate the trigger 46 clockwise. Therefore, the latch 43 on which the trigger 46 is mounted simultaneously rotates clockwise and disengages from the roller41.Atthis time, the follower lever 25 is subjected to a counterclockwise opening force due to the opening spring 7, and this force is transmitted to the drive lever 26 through the transmission linkage 35. However, the drive lever 26 cannot be rotated since it is latched by the latch member 49 th rough the roller 48, and therefore the opening force due to the opening spring 7 causes the collapse ofthe transmission linkage 35 to push upwards the support member38 engaged with the roller34againstthespring force ofthe spring 42.

Furthermore, the follower lever 25 rotates counterc lockwise while folding the transmission linkage 35 against the biasing force of the spring 36 until the other end ofthe follower lever25 abuts againstthe stopper 37. By this operation, the movable contact 2 is driven towards the circuit open position, thereby opening the switchgear. Also, with the folding operation ofthetransmission linkage 35, one end ofthe second link abuts againstthe latch member49to push it down to disengage the latch member 49 from the roller 48. As a result, the drive lever 26 is allowed to rotate counterclockwise, so the drive lever 26 rotates counterclockwise simultaneously with the folding movement of the transmission linkage 35 when the follower lever 25 rotates counterclockwise.Afterthis, when the follower lever 25 abuts againstthe stopper 37 to stop its rotation, thetransmission linkage 35 is expanded by the biasing force ofthe spring 36, so that the drive lever 26 rotates further in the counterclockwise direction. Also, since the force pushing the support member38 upwards is eliminated as the transmission linkage 35 expands, the support member 38 rotates counterclockwise due to the biasing force ofthe spring 42. This rotation of the support member 38 causes the latch 43 to engage with the roller 41, thereby completing the reset of the operating mechanism . This position is shown in Fig. 6.

In the operating mechanism constructed as described above, since the transmission linkage 35 is supported by the support member38 such that the amountoffolding ofthetransmission linkage 35 is limited to a predetermined amount while the mechanism is shifting from the reset position to the circuit closed position, orwhilethe closed position is being maintained, the number of parts can be decreased.

Therefore, the assembly of the mechanism is simplified and the accuracy ofthe positional relationships among the parts is increased, thereby providing an advantagethat reliable operation can be achieved with a simple structure. Further, in accordance with this embodiment, by constituting the mechanism such thatthe latch 43 for latching the support member 38 can be disengaged by a command signal from the exterior, the opening oftheswitchgearuponthe occurrence of a fault during the circuit closing operation or during the closed state can be achieved.

Further, with the arrangement in which one support member 38 supportsthe linkage inthe state in which the four I'nint linkage composedoftbe follower lever 25,the drive lever 26, and the transmission linkage 35 is undertension during the circuit closing operation or in the circuit closed state, the structure can be made very simple as compared to the structure in which a supportstructure is provided for each state. It is necessary for safety purposes that the above support be provided by the support member 38 only when the circuit opening command is not supplied.

Also, by arranging the follower lever 25 and the drive lever26to rotate about a common axis, a common shaft can be used for the levers 25 and 26, making the entire structure simple and compact.

Furthermore, by providing a single nodal point at approximately the center of the transmission linkage 35, the force for holding this nodal point can be made small, and the error in the nodal point holding force due to manufacturing error of the transmission linkage 35 can be made small.

Moreover, by engaging the transmission linkage 35 and the support member 38 through the roller 34, the friction loss during the operation of the operating mechanism is decreased, the operation is smooth, and the energy necessaryfor operating can be reduced.

Also,the engaging portion of the support member 38 against which the transmission linkage 35 abuts can be made an arobf a circle having a center on the rotating axis, wherebythe change in theamountof folding ofthe foldable joint ofthe transmission linkage 35 can be eliminated to keep the amount of folding as small as possible, enabling the supporting force applied to the support member 38to be decreased.

As has been described, the present invention provides an operating mechanismfora switchgearin which a foldable joint is provided in a transmission linkage connecting the drive lever and the follower lever, and the transmission linkage is supported by a support member such that the amount of movement ofthefoldablejoint is not largerthan a predetermined amount, thereby reducing the number of parts, making the mechanism simple and reliable in operation, and increasing the accuracy of the positional relationships among the parts, so that an operating mechanism for a switchgearwhich is simple in structure and reliable in operation can be provided.

Claims (8)

1. An operating mechanismfora switch,com- prising: a follower lever pivotable about a first axis and coupled to a movable contact for opening and closing the latter, a drive lever pivotable relative to the follower lever, about the first axis or an axis parallel thereto, a transmission linkage pivotably, connected between the follower lever and drive lever and including at leastonetoggle knee wherebythe said levers and transmission linkageform afoldable linkage, a support member, and means for releasably holding the support member in an operative position in which the support member restrains folding ofthe transmission linkage wherebythe follower lever is constrained to follow pivoting ofthe drive lever for moving the movable contact, the support memberwhen released being movable to a- pasition allowing folding of the linkage whereby the follower lever can move relative to the drive lever for opening the movable contact.

2. An operating mechanism for a switchgear comprising: a drive shaftto which a movable contact is coupled to actuate said movable contact when rotated; a follower lever mounted to said drive shaftfor rotating about the axis of said shaft between first and second positions; a drive lever rotatably mounted on a shaft having an axis substantially parallel to said drive shaft; a transmission linkage pivotally connected between said drive leveranH said follower lever and having at least one toggle knee betwen the connected ends; a support member, including latch means capable ofengaging and disengaging, for maintaining the amount of collapse of said transmission linkage equal to or less than a predetermined amountwhen said latch means is in the engaging position;; a latch memberforlatchingsaiddriveleverorsaid transmission linkage at a predetermined position when said follower lever is in the second position to hold said follower lever in said second position; and a spring for biasing said follower lever in the direction toward said first position.

3. An operating mechanism for a switchgear as claimed in claim 2, wherein said latch means of said support member includes a latching memberwhich actuates in accordance with an external command.

4. An operating mechanismfora switchgearas claimed in claim 1,2 or3 wherein said followerlever and said drive lever rotate about a common axis of rotation.

5. An operating mechanism for a switchgear as claimed in claim 4, wherein the portion of said support memberwith which said transmission linkage engages has the shape of an arc having its center on said axis of rotation.

6. An operating mechanism fora switchgearas claimed in any preceding claim wherein said toggle knee of transmission linkage is provided at one location substantially midway ofthe connected ends of said transmission linkage.

7. An operating mechanism for a switchgear as claimed in any preceding claim, wherein said transmission linkage and said support member are in engagementthrough a roller.

8. An operating mechanism forswitchgear, substantially as herein described with reference to Figs 4 to 6 ofthe accompanying drawings.