IL101844A - Mechanism for an automatic circuit breaker - Google Patents

Description

MECHANISM FOR AN AUTOMATIC CIRCUIT BREAKER j oxy 'iya Aiia Tiay naa fjJA-in Τ ,βΤ-Ι 9/68 Ε .

FH 89/6 Abstract : 1. Mechanism for an automatic circuit breaker 2.1. The mechanism has a manual operation toggle (1) which is mounted inside a housing (2), is spring-loaded in the switch-off direction and to which a lever (3, 4) is swivellably coupled. During the switching-on process, a contact lever (5) which can be swivelled about an axle (2d) is supported on the lever counter to the force of a spring (7). The contact lever (5) works on a fixed contact piece (6) and can be clamped in the closed position in a self-retaining manner counter to the force of the spring (7). The aim of the invention is to simplify the support connection between the lever (3, 4) and contact lever (5) in order to obtain uniform trigger forces with only small deviations within a switch assembly . 2.2. For this purpose, a toggle joint lever which is formed from an extension lever (3) arid a bar (4) is arranged between the manual operation toggle (1) and contact lever (5) and is virtually extended in a stable position and assumes a precisely defined over dead-centre position of its two articulated arms as a result of the shape of the extension lever (3). The toggle joint lever (3, 4) is thus active as a rigid lever during the switching-on process and in the switch-on position. The toggle joint lever (3, 4) only jumps into an unstable position under the effect of the contact lever (5) which swivels back as a result of the force of the spring (7) as a result of an approximately right-angled loading of its joint (3b/4a) in the direction of the dead centre position which is initiated by means of a trigger lever (9). In this way, the rigid coupling between manual operation toggle (1) and contact lever (5) is cancelled so that the contact-side lever arm (5c) can swivel into its open position. 2.3. The mechanism according to the invention is particularly suitable for fault current and automatic cutout switches.

FH 89/6 17.03.1992 FH 89/6 Description: "Mechanism for an automatic circuit breaker" The invention relates to a mechanism for an automatic circuit breaker having the features of the preamble of Claim 1.

A mechanism of this kind is disclosed in DE-PS 500 098 for an electromagnetic excess current switch. The toggle-lever mechanism described therein consists of a plurality of articulated joints which press a spring-mounted contact lever against a fixed contact in the event of a switch-on movement at the hand lever. The articulated joints which form the toggle lever are ad-justed with respect to one another by means of a screw in order to maintain the over dead-centre position exactly. In the region of the articulated axis, a curve-shaped surface is directly formed onto a link or else applied as a separate part, on which a tappet of a trigger element acts. The curve, which is of very differently curved shape, is to be in each case at approximately the same distance from the tappet during the switch-on movement so that, in the case of excess current, said tappet can press the toggle joint through immediately after touching of contacts. In this mechanism, the curve can only be matched to the movement of the joint during the switching-on process with great difficulty and, depending on the contact consumption and the various tolerances of the components, deviates considerably from the ideal state. Therefore, a large trigger path of the tappet is required in order to eliminate the over dead-centre position of the toggle joint lever and to disconnect the switch even under unfavourable conditions. In modern current-limiting automatic cut-out switches with their short switch-off times, such long paths of the trigger - 2 - FH 89/6 elements are hardly ever provided. In addition, in each case the trigger point is too inaccurate. A further disadvantage consists in the adjustment of the over dead-centre position of the two articulated arms. In mass production, as is customary with automatic circuit breakers, such an additional adjustment point can hardly be realised. Apart from the additional costs, the levers with an adjustment screw become much too large and too heavy. In order to accelerate such a toggle joint lever, the trigger forces must also be greater, which in turn would result in stronger magnetic and thermal trigger elements .

Furthermore, DE 23 36 222 Al discloses a switching mechanism in which a resiliently arranged contact lever interacts with a manual operation toggle via a plurality of links which are connected to one another in an articulated fashion. In one of these links, a pin is held longitudinally guided in a slot, which pin itself can be hooked behind a rotatably mounted latch and thus locks the entire mechanism. The double-armed contact lever is transversely displaceably guided with a slot on a fixed axle and can be swivelled about it. On the side facing away from the contact point, a spring which tensions the entire mechanism in the switch-on position and generates the contact pressure engages on the contact lever. This switching mechanism is disadvantageous to the extent that a plurality of articulated arms are required which also are additionally locked with a latch mechanism. Small unlatching forces are therefore achieved here with only a large degree of expenditure in terms of components .

The invention is based on the object of simplifying the toggle joint mechanism mentioned at the beginning and of improving it for a modern circuit breaker, in particular an automatic cutout switch and/or fault current cutout switch in such a way that the stable, virtually extended over dead-centre position of the toggle joint lever is predetermined in each case automatically and independently of the installation position of the switch without adjustment and setting operations, and, at the same time, the components of force and displacement required to eliminate the latching can be determined very exactly and can be permanently maintained in series production with only small deviations. At the same time, a uniform and exactly determined trigger curve which can be constantly followed irrespective of the state of the contact point is to be obtained at each point of the switch-on movement from the first touching of contacts up to the full switch-on position in which they are clamped in one another.

This object is achieved by means of a mechanism with the characterising features of Patent Claim 1. Further developments and advantageous embodiments of the invention are subjects of the subclaims.

The mechanism according to the invention is advantageous to the extent that in its virtually extended stable over dead-centre position the toggle joint lever is practically active as a rigid lever and its two articulated arms simply support one another without any additional parts. In this case, due to the special design of extension lever and round wire bar, the over dead-centre path can be maintained in. a dimensionally accurate manner in all switches with low tolerances in large scale series production. All the articulation components have a continuously high-quality surface finish so that only a small degree of bearing friction occurs in the articulation points and particularly in the toggle joint. In addition, the mechanism is hardly susceptible to knocks and its articulation points are insensitive with respect to dust or consumption particles. The trigger force can also be exactly predetermined over the entire trigger path since said force is predominantly determined by the extension movement, resulting from the over dead-centre path, as far as the dead-centre position against the force of the contact lever spring. On the other hand, the influence of the tension spring which folds in the - 4 - FH 89/6 two articulated arms in the direction of the over dead-centre position can be ignored due to its special arrangement in the switch-on position and thus also in the event of triggering.

A particular advantage of the invention consists in the fact that during the switching-on process a trigger cam of the extension lever and a shaft of the round wire bar together describe an only flatly curved orbit which is exactly predetermined by the contact lever. As a result, independently of the state of the contact point and of its changing consumption reserve during the switching-on process from the first touching of contacts up to the complete self-locking switch-on position, an exact and always constant trigger curve is defined. In particular in the case of so-called contact making, triggering occurs satisfactorily immediately and already before the toggle limit position is reached. It is also advantageous that the toggle joint lever does not jump into its unstable position until the dead centre position is exceeded, and it thus releases the contact lever for the switching-off movement whilst in the case of an inadequate trigger movement, for example after a brief thermal loading, it returns into the original stable over dead-centre position predetermined by the mechanism.

The invention is explained in greater detail below with reference to an exemplary embodiment illustrated in the drawing, in which Fig. 1 shows the mechanism with the components, required for an understanding of the invention, in the switch-on position, Fig. 2 shows said mechanism during the trigger process briefly after the dead-centre point has been passed.

Fig. 3 shows the switch-off position of the mechanism with manual operation toggle ready for switching on. In each case on a larger scale, - 5 - FH 89/6 Fig. 4 shows the over dead-centre position of the toggle joint lever in accordance with Fig. 1 in a diagrammatic view, Fig. 5 shows a movement diagram of the toggle joint lever over the trigger curve during the switching-on process and Fig. 6 shows a still larger scale view of the bearing of the round wire bar in the extension lever and its association with the trigger cam.

The mechanism, shown in its functional plane, in accordance with Figs. 1 to 3 has a manual operation toggle (1) which is constructed for manual switching and is arranged for the most part within a housing (2) (merely indicated) of the automatic circuit breaker and is mounted on an axle (2a) which is fixed to the housing and can be swivelled between two fixed stops (2b, 2c). The manual operation toggle is provided approximately diametrally opposite its handle (la) protruding out of the housing with a bore (lb) in which an extension lever (3) is swivellably coupled by means of an axle (3a). Together with a round wire bar (4) which functions as a support lever and is bent in a U-shape, the extension lever forms a toggle joint lever which is to be explained in greater detail and which constitutes the core of the invention.

The extension lever (3) is a plastic moulding with a bearing bore (3b) which determines the joint, for the one leg (4a) of the round wire bar (4), the other leg of which (4b) which is supported on one side on a stop face (3e) engages in a linking element (5a) of a rigid contact lever (5). The latter is held displaceably for example in its centre with an elongate hole (5b) on a further axle (2d) which is fixed to the housing and can be swivelled about said axle so that its contact-side lever arm (5c) can be placed in a closed position with a fixed contact piece (6). A spring (7) which is hooked into the housing with an eye (7a) and engages with a hook (7b) approximately between the linking element (5a) and - 6 - FH 89/6 elongate hole (5b) on the contact lever (5), pulls the latter in the switch-on position (Fig. 1) against the bar (4) of the toggle joint lever which, together with the extension lever (3), is in its stable, virtually extended over dead-centre position. In this arrangement, the bar shaft of the leg (4b) supports the linking element (5a), which engages around it in a half-shell shape, in a vibration-proof and reliable manner so that the spring (7) presses the contact lever (5), which is preferably constructed as a flat part and is displaceable on the axle (2d), in the clockwise direction against the fixed contact piece (6) and generates the contact pressure.

A further but considerably weaker tension spring (8) engages on the extension lever (3). This tension spring is hooked into a hook extension (3c) and inside the housing in such a way that, by virtue of its pulling direction, particularly in the switched-off state (Fig. 3) a swivel moment is exerted on the extension lever (3) in the clockwise direction and thus in the direction of the over dead-centre position. In the switching positions in accordance with Fig. 2 and Fig. 3, the lever arm which is predetermined here by the line of action of the tension spring is considerably greater around the bearing point (lb/3a) of the extension lever than in Fig. 1, as can be readily seen from the figures. In contrast, in the switch-on position (Fig. 1) its direction of action almost coincides with the connecting line of its suspension point (at 7a) in the housing and the axle (3a) due to the selection of the contact points of the tension spring (8) so that the swivel moment virtually goes towards "zero" and the trigger force is not influenced. However, in this position the tension spring (8) continues to load the manual operation toggle (1) in the switching-off direction by exerting a right-handed rotational moment on the latter about the axle (2a) via the bearing point (lb, 3a) of the extension lever.

A trigger lever (9) which engages over the contact lever (5) is mounted on a further axle (2e) which - 7 - FH 89/6 is fixed to the housing and the trigger lever can be swivelled for example in the case of an automatic cutout switch in the clockwise direction in a known manner by a thermal or magnetic trigger element (not shown) . The trigger lever (9) has at its outer edge a region which is tuned to the switching movements and to the trigger characteristics and has a trigger contour (9a) and thus operates on a selectively arranged trigger cam (3d) of the extension lever (3), (Fig. 1, Fig. 5, Fig. 6). The latter is itself provided in the functional plane of the mechanism below the semicircular trigger cam (3d) with the precise stop face (3e) mentioned at the beginning, against which face the bar shaft (4b') of the round wire bar (4) rests in the over dead-centre position on one side in such a way that the bar shaft and trigger cam are arranged in the axial direction lying one behind the other and provided with the same degree of rounding in a congruent fashion (Fig. 1, Fig. 6). As a result, during the switching-on process they describe together an orbit, with a large radius, about the contact lever axle (2d). In particular this precisely defined orbit of the trigger cam (3d) and bar shaft (4b'), as illustrated in outline in Fig. 5 in its essential phases during the switching-on process by swivelling the manual operation toggle (1) from the "zero" position into the "I" position, considerably simplifies the matching of the trigger contour (9a) of the trigger lever (9). The actual functionally important trigger contour (9a) therefore also extends in an arcuate shape about the centre point of the contact lever axle (2d) concentrically with respect to the path of the cam so that triggering can take place from the first touching of contacts (position "B") up to the complete switching-on (position "I") at any time and in a non-delayed manner under the same conditions. Particularly in the case of so-called contact making the mechanism therefore unlatches immediately after the touching of contacts (5c, 6) irrespective of their state and consumption.

FH 89/6 It can also be seen from Fig. 5 that the articulation point (3.b/4a) between the extension lever (3) and the bar (4) passes through a very unstable curve during the switching-on process. Particularly in the last phase of the switching-on movement when the further articulation (lb/3a) on the manual operation toggle (1) swivels across the line connecting axle (2a) and bar shaft (4b') and indicated by a thin broken line, and the mechanism tensions itself, the joint (3b/4a) of the toggle joint lever runs back from the maximum point in a curve. This arc, which has a higher degree of curvature, at the articulation point (3b/4a) can, in contrast with the virtually linear orbit of the trigger cam (3d), only be followed with a trigger lever with difficulty and in any case requires a considerable idle motion of the trigger element until the toggle joint lever is pressed through .

In addition, the stop face (3e) which is located underneath the unlatching cam and is matched to the two bearing points (3a, 3b) with a particularly high degree of dimensional precision is of particular significance since, in the virtually extended stable position of the toggle joint lever formed from the extension · lever (3) and bar (4), said stop face (3e) exactly predetermines the over dead-centre point path "X" (length of the distance "X" in Fig. 4 shown in a diagrammatically exaggerated view) . This over dead-centre path determines the trigger characteristics of the mechanism as a function of the spring forces and the lever arms of various length so that, in accordance with the respectively predetermined force ratios, a careful matching of the distance "X" will be necessary. In the final analysis, however, in mass production the precise dimension can be maintained with narrow tolerances since, apart from the metallic axle parts (axle 3a, bar shafts 4a', 4b') which are to be produced with precise diameters, only a moulding dimension of the extension lever (3) is significant. In contrast, all the other - 9 - FH 89/6 dimensional deviations of the mechanism and housing parts have practically no influence on this virtually extended over dead-centre position in the scope of customary production tolerances.

The toggle joint lever which acts in the switch-on position (Fig. 1, Fig. 4) as a rigid lever is also swivelled itself, with its bearing axle (3a) forming a second toggle joint, on the manual operation toggle (1) over the dead-centre point, in relation to the appropri-ate connecting line (not illustrated) between the toggle axle (2a) and the bar shaft (4b") which engages on the contact lever. The entire mechanism is thus mainly tensioned in equilibrium in terms of forces by means of the spring (7) which is arranged approximately parallel to the extension lever (3) and pulls on the contact lever (5) at an approximate right angle, the housing stop (2b) and the fixed contact piece (6) forming the mating bearing. In contrast, the influence of the tension spring (8) is only of secondary importance.

If the trigger lever (9) experiences a right-handed rotational moment - either in a creeping fashion due to a thermal trigger or abruptly due to a magnetic trigger - in the switch-on position in accordance with Fig. 1, its trigger contour (9a) presses against the trigger cam (3d) and the extension lever (3) describes a swivel movement about its axle (3a) in the counter clockwise direction. The bar shaft (4a') which is mounted in the extension lever also moves in the same direction while the bar shaft (4b') which supports the contact lever (5) is released from the stop face (3e). If the extension lever is ultimately swivelled so far on the trigger cam (3d) that the bar shaft (4a') which forms the toggle joint has covered the distance "X" as far as the dead-centre position, in which case the force acting on the trigger lever (9) has to overcome the higher tension of the spring (7) due to the slightly stretching articulated arms, the stable position is cancelled and the toggle joint lever jumps into its unstable position - 10 - FH 89/6 (Fig. 2). In this way, the entire tensioning of the mechanism is eliminated and the contact lever (5) swivels about the axle (2d) in the counter clockwise direction under the effect of the spring (7) which now provides the opening force. At the same time, the contact-side lever arm (5c) lifts up from the fixed contact piece (6) and reaches the switch-off position (Fig. 3).

If, in this process, the manual operation toggle (1) is not held tight, the tension spring (8) which engages on the extension lever (3) also pulls it approximately simultaneously into the position in accordance with Fig. 3, the manual operation toggle now coming to rest against the opposite stop (2c). In this process, the axle (3a) has moved on an orbit about the toggle axle (2a) and thus the contact point of the tension spring (8) on the hook extension (3c) has been moved to such an extent that a powerful right-handed rotational swivel moment pulls the extension lever (3), and thus also the bar (4), in the direction of the stable position. The bar shaft (4b') which is certainly guided in the linking element (5a) of the contact lever with adequate longitudinal play but is guided more tightly at the sides can only deflect to the extent that the extension lever comes to rest in every case with its stop face (3e) against the bar shaft (4b') and the toggle joint lever immediately resumes its virtually extended over dead-centre position (Fig. 3).

The mechanism is thus again ready to switch on. A corresponding, preferably manual left-handed rotational swivel movement on the handle (la) then pushes the extension lever (3) which also swivels on the axle (3a) in the opposite direction together with the round wire bar (4) as a practically rigid lever in the direction of the contact lever (5) which pushed at its linking element (5a) by the bar shaft (4b'), ultimately reaches the switch-on position, already described, in accordance with Fig. 1; provided the trigger lever (9) does not already unlatch the mechanism beforehand during the switch-on - 11 - FH 89/6 movement, for example, during contact making.

Claims (9)

- 12 - FH 89/6 Patent claims;

1. Mechanism for an automatic circuit breaker, in which, by means of a manual operation toggle (1) and a toggle joint lever (3, 4) which is swivellably coupled thereto and is located in a stable position with virtually extended over dead-centre position of its two articulated arms (3, 4), a contact lever (5) which can be swivelled about an axle (2d) fixed to the housing and is supported on the toggle joint lever (3, 4) during the switching-on process can be placed counter to the force of a spring (7) with its contact-side lever arm (5c) in the closed position with a fixed contact piece (6) and can be clamped in this position in a self-retaining manner, as well as with a separately swivellably mounted trigger lever (9) by means of which an approximately right-angled loading of the toggle joint can be brought about in the direction of the dead-centre position by means of the trigger cam (3d) which is constructed on one articulated arm and the support effect of the toggle joint lever (3, 4) can be cancelled so that the contact lever (5) can swivel into the open position with its contact-side lever arm (5c) by the force of the spring (7), characterised in that the toggle joint lever formed from an extension lever (3) and a U-shaped round wire bar (4) is located in the stable position in each case in a precisely defined over dead-centre position solely by virtue of the shape of its two articulated arms (3, 4) and their mutual association, and in that the extension lever (3) mounted on the manual operation toggle (1) has a roller-shaped trigger cam (3d) which is arranged in the axial direction, so as to be congruent with the one leg (4b) of the round wire bar (4) which acts on the contact lever (5), in such a way that during the switching-on process and also during manual switching-off at the manual operation toggle (1) the trigger cam (3d) and the leg (4b) are together guided by the contact lever (5) around its axle (2d) on an exactly defined orbit with a large radius and the trigger lever (9) has about the same - 13 - FH 89/6 central point (axle 2d) a circular trigger contour (9a) which is matched thereto.

2. Mechanism according to Claim 1, characterised i.n that the U-shaped round wire bar (4) is rotatably mounted in the extension lever (3) with its leg (4a) which serves as articulation point, whilst its other leg (4b) which is in engagement with the contact lever (5) is arranged in a parallel plane with respect to the trigger cam (3d) in the axial direction directly next to the latter.

3. Mechanism according to Claims 1 and 2, characterised in that the two articulated arms (3, 4) of the toggle joint lever are clamped to one another in a supporting fashion in the almost extended stable position by means of a moment of a spring (tension spring 8), which moment acts on said articulated arms in the direction of their over dead-centre position.

4. Mechanism according to Claims 1 to 3, characterised in that the extension lever (3) mounted on the manual operation toggle (1) is pulled in the direction of the over dead-centre position of the toggle joint lever (3, 4) by means of a tension spring (8) which engages tangentially on said extension lever and at the same time loads the manual operation toggle (1) in the switch-off direction.

5. Mechanism according to one of Claims 1 to 4 , characterised in that the over dead-centre position of the toggle joint lever (3, 4) is predetermined in a dimensionally precise manner in the stable position by means of stop means (stop face 3e, bar shaft 4b') which are associated with one another in a defined manner, of the two articulated arms.

6. Mechanism according to Claim 5, characterised in that the leg (4b), which engages on the contact lever (5), of the round wire bar (4) is supported in the over dead-centre position on one side on its bar shaft (4b') by a dimensionally precisely matched stop face (3e) of the extension lever (3) - with respect to its two bearing points (3a, 3b) . - 14 - FH 89/6

7. Mechanism according to one of Claims 1 to 6 , characterised in that the stop face (3e) for the bar shaft (4b') is formed together with the trigger cam (3d) on the extension lever (3) - with respect to the functional plane of the automatic circuit breaker -between the contact lever (5) and said trigger cam (3d), the trigger cam (3d) and the bar shaft (4b') being arranged located one behind the other in the axial direction on the side of the trigger lever (9) with the same radial contour.

8. Mechanism according to one of Claims 1 to 7, characterised in that the preferably rigid contact lever (5) which is mounted with an elongate hole (5b) on the axle (2d) which is fixed to the housing has in its lever arm lying opposite the contact point (5c, 6) a linking element (5a) which is matched to the wire diameter of the bar (4) and to the switching movements, within which element the leg (4b) of the bar (4) which engages on the contact lever (5) is guided and is stabilised so as to rest there with its bar shaft (4b') during the switching-on process and is stabilised in the switch-on position counter to the force of the spring (7).

9. Mechanism according to one of Claims 1 to 8, characterised in that the stable position of the two articulated arms (3, 4) is not cancelled until the entire over dead-centre position path (distance "X") in the articulation point (3b, 4a) has been covered by means of an, if appropriate, creeping unlatching movement which is initiated by the thermal, magnetic or by a different trigger element of the automatic circuit breaker and transmitted by the trigger lever (9) to the trigger cam (3d), and the toggle joint lever assumes its unstable position under the effect of the opening contact lever (5) while in the case of an incomplete unlatching movement to near to the dead-centre point, the two articulated arms (3, 4) return to their original over dead-centre position under the effect of the tension spring ( 8 ) .