EP2256778B1 - Electric switching device with a thermal actuator - Google Patents

Abstract

The switch (1) has a tripping device comprising a strip (2) made from thermal bimetal and shape memory alloy. The strip is fastened to a free end of a retaining bracket (4) supported at a support end in a movable manner. The strip stays in effective connection with a latch (8), and a current path runs between input and output terminals (9, 10). The terminal (9) and a fastening end (3) of the strip are connected over a conductor piece (11) i.e. conductor strip, that has higher conductivity than the bracket, where the bracket is made from steel and the conductor piece is made from copper.

Description

The invention relates to an electrical switching device, in particular a circuit breaker, with a running between a first and a second terminal current path, with a thermal release comprising a strip of bimetallic strip or of a shape memory alloy, the strip with its attachment end at the free end of a on a Supporting movably mounted retaining leg is attached and at its actuating end is in operative connection with a switching mechanism, wherein the current path leads from the first terminal via a first conductor piece to the bearing end and on the free end of the retaining leg, as well as the attachment end and the operating end of the strip according to the preamble of claim 1.

A generic circuit breaker is for example in the DE 10 2008 006 863 A1 shown. It has an access and an output terminal with a current path passed through it by the switching device. The current path leads via a contact point, which is formed between a moveable contact lever mounted on a movable and a fixed contact piece, and at least one thermal, often additionally via an electromagnetic release, of which the thermal release in the event of an overcurrent and the electromagnetic release contribute to the elimination of the switching device when a short-circuit current occurs. The thermal trigger acts on triggering to a Verklinkungsstelle within a switching mechanism, which is coupled to the movable contact lever, to their unlatching a. If the Verklinkungsstelle unlatched, the contact lever is pivoted, so that the movable and the free contact piece are separated. The electromagnetic release opens when a short-circuit current occurs, the contact lever directly by impact; At the same time, the electromagnetic release also actuates the switch lock so that the switching device is permanently open.

For Justierungzwecken the bimetallic strip is mounted in generic electrical switching devices at the free end of a movably mounted holding leg. For reasons of space and installation, the current path, coming from the access terminal, first passes through a first conductor piece to the bearing end of the holding leg, then through the holding leg and the bimetal strip and finally further into the interior of the device. The bimetallic strip is traversed directly by the current of the current path, one speaks of a directly heated bimetallic strip. At high rated currents, there may be an undesirably high voltage drop and undesired heating due to the resistance of the first conductor piece and the holding leg.

A finite line protection switch is in the US Pat. No. 5,872,495 shown.

The present invention is therefore in the light of the prior art, the object of further developing a generic electrical switching device so that the electrical resistance between the access terminal and the bimetallic strip is reduced.

The problem underlying the invention is achieved according to the invention with the characterizing features of claim 1.

According to the invention, the first terminals and the fastening end of the strip are additionally connected via a second conductor piece, which has a higher conductivity than the holding leg. The second conductor piece effectively creates a bypass conductor with low electrical resistance, which is electrically connected in parallel to the holding leg. The resulting total resistance between the terminal and the attachment point of the bimetallic strip is thereby very small, because of the parallel connection smaller than the smallest individual resistance. Even at high rated currents now no excessive warming and no large voltage drop can occur.

According to a particularly advantageous embodiment of the invention, the switching device comprises an arc guide rail with a housing fixedly mounted extension, the free end forms the retaining leg for attachment of the strip and to U-shaped bent and is pivotally mounted on the bending point forming the bearing end. The advantage of this is that the bearing end is held fixed to the housing for the retaining leg by its connection with the housing fixed arc guide rail or the housing fixedly mounted extension of the arc guide, which is favorable for the reproducibility of the thermal adjustment of the thermal bimetallic release.

According to an advantageous embodiment of the invention, the holding leg is pivotable with an adjusting means for adjusting the thermal release. The adjusting means may for example be an adjusting screw.

According to a particularly advantageous embodiment of the invention, the second conductor piece is a conductor strip with a loop-like bulge. A conductor strip has a certain rigidity and strength and is therefore particularly well suited for automatic production, in which the individual parts are to be supplied very precisely by handling machines for mounting in the open housing. The loop-like bulge ensures that the second conductor piece can still give something, if the mounting end of the bimetallic strip is slightly pivoted when adjusting and thereby changes its distance from the access terminal.

According to a further advantageous embodiment of the invention, the second conductor piece is a movable stranded wire. This can very well follow a pivoting of the attachment end of the bimetallic strip due to their flexibility.

According to a particularly advantageous embodiment of the invention, the holding leg made of steel and the second conductor piece consists of copper. Steel is inexpensive and meets the requirements of dimensional stability and strength has but a relatively high specific resistance. Copper has the required high electrical conductivity, but with reduced mechanical strength.

Further advantageous embodiments and improvements of the invention and further advantages can be taken from the subclaims.

figure description

Figures and description serve to better understand the subject. Articles or parts of objects which are substantially the same or similar may be given the same reference numerals. The figures are merely a schematic representation of an embodiment of the invention.

Fig. 1

eine Ansicht eines erfindungsgemäßen elektromagnetischen Auslösers, und

Fig. 2

eine schematische Ansicht eines Installationsschaltgerätes mit einem er- findungsgemäßen elektromagnetischen Auslöser.

Showing:

Fig. 1

a view of an electromagnetic release according to the invention, and

Fig. 2

a schematic view of a service switching device with an inventive electromagnetic release.

In the figures, identical or equivalent components or elements are provided with the same reference numerals.

FIG. 1 schematically shows an insight into an open housing of an electrical installation device 1, here a circuit breaker. Between an access terminal 9 and an outlet terminal 10, a current path initially passes over a terminal rail 29, a first conductor piece 14 welded thereto, to the bearing end 5 of a retaining leg 4. At the free end 6 of the retaining leg 4 is a strip 2 of bimetallic strip with its attachment end. 3 welded. The opposite, free end 7 of the bimetallic strip 2 is connected to a strand 20. This leads the flow of current to a pivotably mounted in a bearing 21 contact lever 17, which carries a movable contact piece 18 at its free end. This forms together with a fixed contact piece 19 a Contact point. From the fixed contact piece 19 of the current path continues via a magnetic trigger 16 to the output terminal 10th

If the current in the main current path remains above the rated current for a long time, then one speaks of an overcurrent, bends the thermobimetallic strip 2 with its free, the fastening end opposite end due to the current heat caused in him by the overcurrent so far that he has an action line 22 acts on a switch lock 8 and there ensures that a Verklinkungsstelle is unlatched. The realization of the interaction of the bimetallic strip with the switching mechanism 8 can be realized in various ways, one possibility is in the already mentioned DE 10 2008 006 863 A1 shown. After unlatching the Verklinkungsstelle the rear derailleur acts on a line of action 24 on the contact lever 17 and pivots it in a clockwise direction, so that the movable contact piece 18 separated from the fixed contact piece 19 and the contact point is opened and kept open by the switching mechanism 8. A reconnection can be done via a switch knob 27 which cooperates via a line of action 26 with the switch lock 8 and when actuated a latching of Verklinkungsstelle allowed when the bimetallic strip 2 has bent back to its original position after the overcurrent has subsided. Since the Thermobimetallstreifen 2 is welded to the bottom of the support leg 4, by pivoting the retaining leg 4, the distance of the free operating end 7 of the bimetallic strip 2 of the Switch lock 8 adjustable.

If a short-circuit current flows through the current path, ie a current that increases to a multiple of the rated current in a very short time, the magnetic release 16 responds. This then proposes via a line of action 25 directly and quickly to the contact lever 17, at the same time it acts on an action line 23 on the switching mechanism 8 for its unlatching and for permanent keeping open the contact point.

In a quick impact of the contact point is formed between the moving contact pieces a switching arc. This commutes after a short time on a Festkontaktleitschiene 30 and an arc guide rail 12 and is led by both in an arc extinguishing chamber 15 to extinguish.

The arc guide rail 12 carries on its right, the contact point facing side, an extension 31. This has approximately a U-shape, with a first leg 32 which is directly connected to the arc guide rail 12, and a second leg which forms the holding leg 4 , The retaining leg 4 is formed by bending the extension 31 at a bending point which has also been referred to above as the bearing end 5 for the retaining leg 4. The arc guide rail 12 with the extension 31 may be made of one part. Advantageously, this is a stamped and bent part made of steel. Steel is preferred because of its magnetic property, strength and low cost. The guide rail 12 and the first leg 32 are fixed to the housing and held, which can be made possible in various ways, for example by clamping between webs on the inside of the housing. The retaining leg 4 must remain movable, as described above in connection with the adjustment of the bimetallic strip. The tight fit of the first leg 32 is important in terms of the constancy of the thermal tripping characteristics, since thereby the position of the bimetallic strip 2 relative to the switch lock 8 also remains fixed once it has been adjusted.

FIG. 2 shows in an isolated detail view of the extension 31 and its connection to the access terminal 9. One recognizes the one-piece execution of arc guide rails 12, first leg 32 and retaining leg 4 as a stamped and bent part made of steel. At the upper bending point, which forms the bearing end 5, the steel strip is slotted. This results in two parallel partial strips. One of these partial strips is bent as a holding leg 4 down. The adjacent partial strip is again bent downwards after a short course, pointing horizontally in the direction of the access clamp 9. It thus forms the first conductor piece 14, which is at a contact point 33 with the busbar of the access terminal 9, the terminal rail 29, welded.

At the contact point 33, a second conductor piece 11 is additionally attached. This is here a copper bar, which may be soldered to the pad 33, for example. The other end of the second conductor piece 11 is at the free end 6 of the Holding leg 4 attached, for example, also soldered. So that the mobility of the retaining leg 4 is not hindered, the second conductor piece 11 is made slightly longer than necessary, and carries in the central region a loop-shaped bulge 28. A first portion of the second conductor piece 11 thus extends from the contact point 33 from parallel to the first conductor piece 14, approximately up to the height of the retaining leg 4. Then the loop-like bulge 28 joins, at the end of which a straight section extends again approximately parallel to the retaining limb 4 towards the free end 6. The loop-like bulge ensures that the second conductor piece 11 is not a hindrance to pivoting of the retaining leg 4 in the course of adjustment in the way. In the schematic representation of Fig. 1 For example, the second portion is shown generally as a conductor piece guided around the adjustment screw 13.

Of course, there are other possibilities of realization than those in the Fig. 2 illustrated conceivable. For example, a movable strand could be provided. However, such would be more difficult to assemble with automatic assembly machines than a solid sheet. In a hand assembly, however, a strand would be an advantageous alternative.

Without the second conductor piece of the current path would come from the access terminal 9 via the contact point 33 and the first conductor piece 14 to the bearing end 5 and from there via the holding leg 4 to the free end 6, where the bimetallic strip 2 is welded and the current path in the Thermobimetal transgresses. The second copper conductor piece 11 creates a bypass connection that provides a lower resistivity parallel conductor path. This is, as already explained above, advantageous in particular at high rated currents. Without the second conductor piece 11, the steel conductor pieces would strongly heat up at high rated currents because of the relatively high resistivity of steel. The heat would radiate to the bimetallic strip 2, as a result, this could already bend strongly at rated current and cause too early triggering, which should be avoided.

LIST OF REFERENCE NUMBERS

1

Electrical switching device

2

Strip of bimetallic strip

3

attachment end

4

holding leg

5

bearing end

6

free end

7

actuating end

8th

switch lock

9

first connection terminal

10

second connection terminal

11

second conductor piece

12

arc guide

13

adjusting

14

first conductor piece

15

Arc chute

16

magnetic trigger

17

contact lever

18

movable contact piece

19

solid contact piece

20

braid

21

depository

22

line of action

23

line of action

24

line of action

25

line of action

26

line of action

27

shift knob

28

belly

29

clamping rail

30

fixed contact guide rail

31

extension

32

first leg

33

contact point

Claims (6)

1. Electrical switching device (1), in particular a circuit breaker, having a current path which runs between a first and a second connecting terminal (9, 10), having a thermal release comprising a strip (2) in the form of a thermal bimetallic strip or a shape memory alloy, with the attachment end (3) of the strip (2) being attached to the free end (6) of a holding limb (4), which is mounted such that it can move on a bearing end (5), and the operating end (7) of said strip being operatively connected to a switching mechanism (8) with the current path leaving from the first terminal (9) via a first conductor piece (14) to the bearing end (5) and, further, via the free end (6) of the holding limb (4), as well as the attachment end (3) and the operating end (7) of the strip (2),
   characterized in that the first terminal (9) and the attachment end (3) of the strip (3) are additionally connected via a second conductor piece (11), which has higher conductivity than the holding limb (4).
2. Electrical switching device (1) according to Claim 1, characterized in that the switching device (1) has an arc guide rail (12), having a projection (13) which is mounted fixed to the housing and whose free end forms the holding limb (4) for attachment of the strip (2), and for this purpose is bent in a U-shape and is mounted such that it can pivot at the bend point which forms the bearing end (5).
3. Electrical switching device (1) according to Claim 1, characterized in that the holding limb (4) can be pivoted by means of an adjusting means (13) in order to adjust the thermal release.
4. Electrical switching device (1) according to Claim 1, characterized in that the second conductor piece (11) is a conductor strip with an outward bulge like a loop.
5. Electrical switching device (1) according to Claim 1, characterized in that the second conductor piece (11) is a moving braid.
6. Electrical switching device according to Claim 1, characterized in that the holding limb is composed of steel, and the second conductor piece (11) is composed of copper.

Images