EP0665564A1 - Driving mechanism for a protective breaker - Google Patents

Abstract

The moving contact in a vacuum chamber (1) is operated by a rod (4) connected to a displacement device (5) which is driven by a conductive helical spring (6) of shape memory alloy. Excessive current on the protected line passes through the spring, producing enough heat to switch the alloy from the martensitic to the austenitic phase. An abrupt movement is executed through the dead point constituted by the longitudinal axis of the chamber. Reclosure can be effected by a sequencer (8) comprising three retractable and two non-retractable cams (81-83;84,85) and three pneumatic jacks (87-89).

Description

The present invention relates to a mechanism for actuating a protective switching chamber.

More specifically, it relates to a mechanism for actuating the movable contact of a protective cut-out chamber installed on an electrical line and which must be open when an overcurrent threshold occurs on the line, this mechanism comprising a driving member driving a contact displacement device.

When a fault occurs on the line, it is necessary to detect this fault, for example a short circuit, and open the breaking chamber then, once the fault current has disappeared, order the chamber to be closed. These detections and commands are carried out in a conventional manner using electronic systems, with external energy supply.

The present invention provides such a particularly simple and reliable mechanism, requiring no external control system.

To do this, in accordance with the invention, the drive member is a conductive helical spring made of shape memory alloy electrically linked to the line and the heating of which, when crossed by said overcurrent threshold, is such that said alloy passes from its martensitic phase to its austenitic phase and the mechanism allows the reclosing of the breaking chamber thanks to a sequencing device associated with the displacement device and ensuring an adjustable and timed cycle of openings and closings.

It thus uses the particular properties of shape memory alloys combined with an adequate dimensioning of the spring, so that it under the effect of a fault current, for example greater than ten times the nominal current, s' heats up to a level such that the alloy passes from the martensitic phase to the austenitic phase, this which causes the shape of the spring to change (from a state of relaxation to a state of compression or vice versa) and activates the displacement device causing the opening of the breaking chamber.

In addition, the mechanism includes a sequencing device which delays the reclosing and the possible reopening of the breaking chamber according to an adjustable cycle of openings and closings, for example according to a cycle O-2s-FO-10s-FO-20s -F, and when the fault remains present locks the mechanism in the open position.

According to the preferred embodiment of the invention, the displacement device is a snap action mechanism on either side of a neutral point, connected to the movable contact and movable from a first position where it pushes the contact in. closed position to a second position where it pulls the contact in the open position under the effect of the compression of the shaped alloy spring connected by one of its ends to this displacement device by means of a sliding rod at the inside the spring and abutting at this end when the spring is relaxed and by its other end connected to a fixed support part.

The displacement device comprises two integral arms rotating around an axis, the first being rotated by a tension spring and being connected to the movable contact by means of a pivoting rod and by an arrangement comprising a part guided in a guide rigidly connected to the contact, urged by a compression spring and comprising an oblong hole in which the pivot axis of the connecting rod can slide and the second being integral with the sliding rod.

The sequencing device comprises at least one retractable cam by means of a timing means on which are in traction a hook fixed to the free end of the sliding rod and engaged pushed a roller also attached to the free end of the sliding rod.

Preferably, the sequencing device comprises several retractable cams aligned on a rotary wheel subjected to a return spring and a hook pivoting on a fixed axis retaining one of these cams against the action of the return spring.

The sequencing device also includes two non-retractable end-of-travel locking cams.

In order to allow manual resetting of the mechanism, the sequencing device comprises an independent means of manual erasure of all the cams for resetting this device at the end of the cycle.

In order to allow automatic resetting of the mechanism, the sequencing device comprises an independent means of automatic erasure of all the cams for resetting this device during the cycle, comprising a pneumatic cylinder supplied with gas, by means of a valve controlled by a pneumatic timer, by a compression chamber where a piston slides linked to the displacement device.

The invention is described below in more detail using figures showing only a preferred embodiment of the invention.

Figure 1 is a vertical sectional view of a mechanism according to the invention mounted on a vacuum interrupting chamber.

Figure 2 is a vertical sectional view of the mechanism according to the invention in the closed position.

Figure 3 is a vertical sectional view of the mechanism according to the invention at the start of the open position.

Figure 4 is a vertical sectional view of detail of the mechanism according to the invention in the open position.

Figure 5 is a vertical sectional view of detail of the mechanism according to the invention during the first closure.

Figure 6 is a vertical sectional view of the mechanism according to the invention in the end position of the first closure.

Figure 7 is a vertical sectional view of the mechanism according to the invention in the second opening position.

Figure 8 is a vertical sectional view of the mechanism according to the invention in the third opening position.

Figure 9 is a vertical sectional view of the mechanism according to the invention in the fourth opening and locking position.

Figure 10 is a vertical sectional view of detail of the sequencing device of the mechanism according to the invention.

Figure 11 is a vertical sectional view of detail of the sequencing device of the mechanism according to the invention during manual reset.

Figure 12 is a vertical sectional view of detail of the sequencing device of the mechanism according to the invention during an automatic reset.

The actuation mechanism is generally represented in FIG. 1 where it is mounted on a protective cut-out chamber installed on an electric line and having to be open at the appearance of an overcurrent threshold on the line (equal by example at 10 times the nominal current) according to the example shown a vacuum interrupting chamber 1 connected to a first electrical outlet 11. The assembly is supported by an insulator 2 on a support structure 3. The movable contact of the chamber vacuum 1 is integral with an operating rod 4 connected to a displacement device 5 driven by a motor member consisting of a helical spring 6 made of alloy with shape memory (called AMF spring) with a force of for example around 400N and electrically linked to the line by means of a braid 7 connecting it by one of its ends to the outlet of the rod 4. Its heating, when crossed by said overcurrent threshold, is such that said alloy passes from its martensitic phase to its austenitic phase. In the martensitic phase, the spring 6 has a relaxed shape as shown in FIG. 1.

The mechanism allows the closing chamber 1 to be closed again by means of a sequencing device 8 associated with the displacement device 5 and ensuring an adjustable and timed cycle of openings and closings, according to the example represented according to a cycle O -2s-FO-10s-FO-20s-F, and, when the fault remains present, it locks the mechanism in the open position.

The mechanism is housed in an envelope 9 which supports a second socket 10 connected by another conductive braid 12 at the other end of the AMF spring 6.

The mechanism and the different phases of this cycle will be described below in more detail.

The displacement device 5 will first be described, with reference to Figures 2 and following.

It comprises a set of arms that are integral and rotatable about a horizontal axis, one of which 13 is connected to the outlet of the rod 4 and the other 14 of which is connected to the AMF spring 6. The arm 13 is connected to the outlet of the rod 4 by a connecting rod 15 pivoting at one of its ends on the arm 13 and at the other of its ends in an arrangement with oblong hole 16 and with compression spring 17. The oblong hole 16 is produced in a piece 18 vertically guided in a guide 19 rigidly fixed to the end of the rod 4 and urged downwards by the compression spring 17. The pivot axis 21 between the arm 13 and the connecting rod 15 is connected to the end of a spring of traction 20 whose other end is fixed at a fixed point. In the closed position, as shown in Figure 2, the axis 21 is pulled by the tension spring 20 slightly to the left of the vertical axis forming the longitudinal axis of the cutting chamber 1 and passing through the axis of rotation of the arms 13 and 14. The pivot 22 is then pushed at the top of the hole oblong 16. In this position, the connecting rod 15 is in abutment against a fixed abutment piece 32.

The other arm 14 is connected at its end to the free end of a rod 23 sliding inside the AMF spring 6 and carries to this connection a roller 24 and a hook 34 pivoting on a horizontal axis both cooperating with the sequencing device 8 as will be seen later. The rod 23 carries at its end inside the AMF spring 6 a stop 25 engaged with an end piece 26 secured to the AMF spring 6. The other end of the spring 6 is connected to a fixed support part 27.

This device forms a snap action mechanism on either side of the dead center constituted by the vertical axis forming the longitudinal axis of the breaking chamber 1 and passing through the axis of rotation of the arms 13 and 14 and, in the first position shown in Figure 2, it pushes the movable contact of the switching chamber 1 in the closed position. The stop piece 32 is adjustable and allows the opening force to be calibrated.

A third arm 28 is integral with arms 13 and 14. It is in turn connected to a piston rod 29 urged by a return spring 29A and which slides in a fixed cylindrical chamber 30 supplied with gas, preferably air , in a closed circuit by a bellows or equivalent arrangement compresses gas into a compression volume 31 provided in the housing 9 by means of a non-return valve 30A. The function of this piston 29 and of this compression chamber 30 will appear further on in the description.

When a fault current appears and the overcurrent threshold is exceeded, the AMF 6 spring goes to its austenitic phase and takes its compressed form as shown in Figure 3. It therefore pulls the rod 23 by its end stop 25 and therefore rotates the integral arms 13, 14 and 28 against the force of the tension spring 20 until that the connecting rod 15 and / or the arm 13 abuts against a second fixed abutment piece 33. During this movement, the pivot 22 moves in the oblong hole 16 and the spring 17 is decompressed. An accelerated movement is thus achieved thanks to the inertia of the moving masses. The stop 33 is preferably a shape memory alloy and converts kinetic energy into heat, thus minimizing the rebound effects of the movable contact of the chamber 1. Thanks to the accumulated kinetic energy, the displacement of the movable contact and the 'opening of the breaking chamber 1 are then made at a relatively high instantaneous speed, for example of the order of 1 m / s. Thanks to the neutral mechanism with push spring 17, a maximum opening speed is guaranteed when the overcurrent threshold appears, and the heating of the AMF spring 6 is thus of limited duration.

Chamber 1 being open, the line current is cut and the AMF spring 6 cools until it returns to its relaxed shape as shown in FIG. 4.

The sequencing device 8 then comes into action.

As can be seen in the figures, this sequencing device 8 comprises three retractable cams 81, 82, 83 and two non-retractable end-of-travel locking cams 84, 85 aligned on a rotary wheel subjected to a not shown return spring whose action tends to drive the wheel in the direction of arrow F. A hook 86 pivoting on a fixed axis retains one of these cams against the action of the return spring.

The first three cams 81, 82, 83 are each retractable by means of a time delay means constituted by a pneumatic cylinder 87, 88, 89 as will be explained below.

In the closed position shown in FIG. 2, on the first cam 81 are in traction the hook 34 of the rod 23 and the fixed hook 86 and in pushing engagement the roller 24 of the rod 23.

During the compression of the AMF spring 6 and the opening of the chamber 1, as shown in FIG. 3, the rod 23 is pulled by this spring 6 and the hook 34 pulls on the first cam 81 causing the wheel of the device to rotate sequencer in the opposite direction to the arrow F. The fixed hook 86 then comes into engagement with the second cam 82, maintaining the wheel in this second position.

Once the AMF spring has been extended, as shown in FIG. 4, the spring 20 tends to rotate the arm 14 in the direction of the arrow F but the latter is blocked by the thrust stop of the roller 24 against the first cam 81 retained by the cylinder 87. This cylinder has a calibrated air expulsion orifice for delaying the retraction of the cam 81 according to a period of time of, for example, 2 seconds.

This situation is shown in detail in FIG. 5. After said lapse of time, the jack 87 releases the cam 81 which retracts towards the inside of the wheel by pivoting around the axis 81A. The roller 24 therefore passes this first cam 81, the arm 14 being driven in rotation by the action of the spring 20. The rotation then continues until the bialle 15 comes to bear on the stop 32 and the hook 34 comes s 'hook onto cam 82, as shown in figure 6.

In the position of Figure 6 thus reached, the integral arms 14, 13, 28 have returned to their initial position and the movable contact of the chamber 1 is pushed back into the closed position firstly and secondly by means of the kinetic energy accumulated the spring 17 is recompressed and the neutral point reengineered by the displacement device 5. The first timed reclosing is thus carried out.

The AMF spring 6 is therefore again connected to the line and if the fault current is still present, it begins to heat again and to change shape and the opening phase previously described begins again as shown in FIG. 7. This time, it is the second cam 82 which is pulled by the hook of the rod 34. The fixed hook 86 engages the third cam 83. During the following cooling of the AMF spring 6, it is the timer jack 88 having an orifice expelling air set for example at 10 seconds, which regulates the retraction of the cam 82 and the return to the closed position of the chamber 1.

If the fault current is still present, the opening and closing phases start again in the same way, the opening phase being represented in FIG. 8. It is now the third cam 83 which is moved and the jack 89 which delays its retraction to for example 20 seconds, for reclosing, the fixed hook 86 retaining the fourth non-retractable cam 84.

If the fault current is still present, then the opening and locking phase takes place. The opening phase is identical to the previous ones, but once the AMF spring 6 has cooled and returned to its relaxed position, as shown in FIG. 9, the non-retractable cam 84 blocks the roller 24 and the mechanism is locked in the position of opening of the chamber 1.

In the previously described case where the fault current has resulted in four opening phases, the mechanism is therefore locked and its reset takes place manually. To do this, as visible in FIG. 10, the cams are linked to a disc 90 secured to a pole 91. This disc 90 is rotating on the same horizontal axis as the wheel supporting the cams 81 to 85. The latter are supported with pivoting 81A to 85A at the end of spokes of this wheel with an intermediate articulation 81B to 85B connected to the disc 90. More precisely, each fixed spoke 81C to 85C of the wheel supports at its end an intermediate support arm 81D to 85D with pivoting along a horizontal axis and it is at the end of this intermediate arm that each cam is pivotally connected. In the operating position, the intermediate arms 81D to 83D are retained in alignment with the fixed spokes 81C to 83C thanks to the thrust of the timing cylinders 87 to 89 whose rod is connected to the end of the retractable cams 81 to 83 opposite to that pivoting around the axes 81A to 83A. As for the locking cams 84 and 85, they are pivotally retained at their free end on a fixed support, not shown.

When the operator pulls down the pole 91 as shown in Figure 11, it therefore rotates according to arrow F1 the disc 90 and therefore the joints 81B to 85B which are linked to it. The arms 81D to 85D are therefore moved towards the inside of the wheel and the cams 81 to 85 are deleted, releasing the fixed hook 86, the hook 34 and the roller 24. The displacement device is released is closed chamber 1 and the return spring urging the cam support wheel returns the latter according to arrow F to the original position shown in FIG. 2.

If the fault current disappears during the course of the phases described above, during the next reclosing phase, the AMF spring 6 is no longer crossed by an overcurrent and therefore no longer takes its compressed form and the chamber 1 remains closed. The line is then in normal operation and the sequencing device alone must be reset to return to the original position shown in FIG. 2. The mechanism includes an automatic reset arrangement intended for this operation.

This arrangement includes the piston 29 already described. By sliding in the fixed cylindrical chamber 30, it compresses gas in the compression volume 31. This compression takes place each time the chamber 1 is opened. timing slightly higher than the total time of the timed sequences produced by a valve 92A controlled by a pneumatic timer 92B and connected by a pipe on the one hand to the compression volume 31 and on the other hand to a jack 92, this compressed gas supplies this cylinder 92 visible in FIG. 10. This cylinder 92 is fixed to the disk 90 and its rod is linked to the support wheel for the cams 81 to 85. When supplied with pressure, this jack 92 rotates the support wheel and the cams 81 to 83 are. moved inward, as shown in Figure 12, the joints 81B to 83B being slid in oblong slots 81E to 83E arranged in the disc 90. The hooks 34, 86 and the roller 24 are thus released and the wheel of the sequencer returns to the original position by the action of its return spring. A spring 93 then returns the cams to the active position.

It should be noted that this automatic erasure is only to be provided for the three retractable cams 81 to 83 as visible in FIG. 12, since the cycle is interrupted before locking by the last two cams 84 and 85. The support wheel advantageously is therefore formed of two distinct parts, one carrying the three retractable cams 81 to 83 and the other carrying the two locking cams 84 and 85, the automatic reset arrangement relating only to the first three cams 81 to 83.

Claims (8)

1) Mechanism for actuating the movable contact of a protective breaking chamber (1) installed on a high or medium voltage electrical line and having to be open at the appearance of an overcurrent threshold on the line, this mechanism comprising a drive member driving a contact displacement device (5) and characterized in that the drive member is a helical spring (6) made of shape memory alloy electrically linked to the line and the heating of which, when is crossed by said overcurrent threshold, is such that said alloy passes from its martensitic phase to its austenitic phase and in that it allows reclosing of the breaking chamber (1) thanks to a sequencing device (8) associated with the device movement (5) and ensuring an adjustable and timed cycle of openings and closings. 2) Device according to claim 1, characterized in that the displacement device (5) is a snap action mechanism on either side of a neutral point, connected to the movable contact and movable from a first position where it pushes the contact in the closed position to a second position where it pulls the contact in the open position under the effect of the compression of the shaped alloy spring (6) connected by one of its ends to this displacement device (5) by the 'through a rod (23) sliding inside the spring (6) and abutting at this end when the spring (6) is relaxed and by its other end connected to a fixed support part (27). 3) Device according to claim 2, characterized in that the displacement device (5) comprises two arms (13, 14) rotatable together around an axis, the first (13) being rotated by a tension spring ( 20) and being connected to the movable contact by means of a pivoting connecting rod (15) and by an arrangement comprising a part (18) guided in a guide (19) rigidly connected to the contact, urged by a compression spring (17) and comprising an oblong hole (16) in which the pivot axis (22) of the connecting rod ( 15) and the second (14) being integral with the sliding rod (23). 4) actuating device according to claim 2, characterized in that the sequencing device (8) comprises at least one cam (81, 82, 83) retractable by means of a timing means (87, 88, 89 ) on which are in traction a hook (34) fixed to the free end of the sliding rod (23) and in pushing engagement a roller (24) also fixed to the free end of the sliding rod (23) . 5) An actuating device according to claim 4, characterized in that the sequencing device (8) comprises several retractable cams (81, 82, 83) aligned on a rotating wheel subjected to a return spring and a pivoting hook (86) on a fixed axis retaining one of these cams against the action of the return spring. 6) An actuating device according to claim 5, characterized in that the sequencing device (8) also comprises two non-retractable cams (84, 85) for end-of-travel locking. 7) An actuating device according to claim 6, characterized in that the sequencing device (8) comprises an independent means of manual erasure of all the cams for resetting this device at the end of the cycle. 8) An actuating device according to claim 6 or 7, characterized in that the sequencing device (8) comprises an independent means of automatic erasure of the cams for resetting this device during the cycle, comprising a jack (92) tire supplied with gas, via a valve 92A controlled by a pneumatic timer 92B, by a compression chamber (31) where a piston (29) slides linked to the displacement device (5).

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