Thermal circuit-breaker

Abstract

The invention relates to a circuit-breaker comprising: - an unlocking lever (100) electrically isolated from the current to be interrupted, this unlocking lever being movable between: - an upright position in which a lock is in abutment against one of its ends, in order to keep the circuit-breaker in a non-circuit-breaking state, and - a retracted position in which the lock is no longer in abutment against this end, which allows the circuit-breaker to move into a circuit-breaking state, - a current loop through which the current to be interrupted flows, and - a magnetic target (162) facing the current loop, this magnetic target exerting a force on the unlocking lever, which force mechanically urges the unlocking lever towards its retracted position, this magnetic target (162) being attached, without any degree of freedom, to the unlocking lever.

Description

[0001] Thermal circuit breaker

[0002] [1] The invention relates to a thermal circuit breaker.

[0003] [2] A thermal circuit breaker interrupts a current when its intensity exceeds a predetermined threshold. To achieve this, thermal circuit breakers often use a bimetallic strip through which the current to be interrupted flows. The higher the intensity of the current to be interrupted, the more the bimetallic strip heats up and bends. When the bimetallic strip reaches a certain degree of curvature, the circuit breaker trips. Due to the thermal inertia of the bimetallic strip, it takes a certain amount of time for the deformation of the bimetallic strip to reach the degree of curvature that causes it to trip. Thus, such a circuit breaker operates correctly when the intensity does not reach excessively high values ​​too quickly.

[0004] [3] However, in the event of a short circuit, the current intensity increases very quickly and reaches very high values ​​before the circuit breaker trips. If nothing is done to make the circuit breaker trip more quickly in the event of a short circuit, these very high current intensity values ​​can damage the circuit breaker and especially the electrical circuit it protects.

[0005] [4] To overcome this drawback, known thermal circuit breakers implement a short-circuit protection mechanism that reduces the time required for the thermal circuit breaker to switch from its non-tripped state to its tripped state in the event of a short circuit. Such a protection mechanism is described in application US4990882A. In application US4990882A, the protection mechanism comprises a current loop and a magnetic target located opposite this current loop. The current loop is crossed by the current to be interrupted. Thus, the current loop generates a magnetic field whose intensity increases as a function of the intensity of the current to be interrupted. In application US4990882A, the magnetic field generated by the current loop repels the magnetic target. In this application US4990882A, the magnetic target and the bimetallic strip form a single part.Thus, in the event of a short circuit, the bimetallic strip deforms more quickly under the combined action of its heating and the magnetic field generated by the current loop. Under these conditions, even in the event of a short circuit, the circuit breaker switches to its tripped state before being damaged.

[0006] [5] The thermal circuit breaker of application US4990882A works particularly well. However, the current loop is bulky and it is difficult to reduce its dimensions without significantly degrading the operation of the protection mechanism. Similarly, it is difficult to reduce the dimensions of the magnetic target without degrading the operation of the thermal circuit breaker. It is also difficult to adjust the sensitivity of the short-circuit protection mechanism, i.e. the threshold beyond which the force exerted on the magnetic target substantially accelerates switching to the tripped state.

[0007] [6] The invention aims to remedy at least one of these drawbacks.

[0008] [7] The invention is set forth in the attached set of claims.

[0009] [8] The invention will be better understood on reading the description which follows, given solely as a non-limiting example and made with reference to the drawings in which:

[0010] - figure 1 is an illustration, in perspective, of a circuit breaker,

[0011] - figure 2 is a view, in vertical section, of the circuit breaker of figure 1,

[0012] - figure 3 is a perspective view of a fixed support and a mobile support of the circuit breaker of figure 1,

[0013] - Figure 4 is a perspective view of a locking subassembly of the circuit breaker of Figure 1, and

[0014] - figure 5 is a perspective view of the bimetallic strip and a bar of the circuit breaker of figure 1.

[0015] [9] In this description, the terminology, conventions and definitions of the terms used in this text are introduced in a chapter I. Then, a detailed example of an embodiment is described in a chapter II with reference to the figures. In a chapter III, variants of these embodiments are presented. Finally, the advantages of the different embodiments are specified in a chapter IV.

[0016]

[0010] Chapter I: Definitions, terminologies and conventions:

[0017]

[0011] In the figures, the same references are used to designate the same elements.

[0012] In the remainder of this description, the characteristics and functions well known to those skilled in the art are not described in detail.

[0018]

[0013] The figures are oriented relative to an orthogonal XYZ coordinate system, where the X and Y directions are horizontal and the Z direction is vertical. Terms such as "above", "below", "top", "bottom", "upper", "lower" are defined relative to the Z direction.

[0019]

[0014] The circuit breaker trip threshold designates the value of the current intensity from which the circuit breaker switches to its tripped state.

[0020]

[0015] The term “high intensity current” means a current whose intensity exceeds 1000 A or 4000 A.

[0021]

[0016] An electrically conductive material is a material whose electrical conductivity, at 20°C, is greater than 10 4 S / m or at 10 6 S / m.

[0022]

[0017] An electrically insulating material is a material whose electrical conductivity, at 20°C, is less than 10 10 S / m or at 10 14 S / m.

[0023]

[0018] Chapter: Example of embodiment

[0024]

[0019] Figure 1 shows a thermal circuit breaker 2 which can be used to interrupt both alternating current and direct current. This circuit breaker 2 comprises:

[0025] - a housing 4 made of electrically insulating material,

[0026] - terminals 6 and 8 for current input and output,

[0027] - a button 10 for manual operation of the circuit breaker.

[0028]

[0020] Typically, the housing 4 is a substantially parallelepipedal housing whose height is parallel to the Z direction, the width parallel to the X direction and the depth parallel to the Y direction. Most of the components of the circuit breaker 2 are housed inside this housing 4 so that they are protected from the outside by the housing 4. In particular, the housing 4 comprises:

[0029] - an upper face 12,

[0030] - a lower face 14,

[0031] - a front face 16 and a rear face not visible in figure 1, and

[0032] - vertical lateral faces 18 and 20 located on either side of the front face 16.

[0033]

[0021] The lateral face 18 comprises a protrusion 22 inside which is housed a subassembly 24 (Fig. 2) for displaying the state of the circuit breaker 2.

[0022] The lugs 6 and 8 are fixed, without any degree of freedom, to the housing 4. These lugs 6, 8 are each intended to be connected to an electric cable or plugged into an electrical connector so that a current passes through the circuit breaker 2. These lugs 6 and 8 project from the lower face 14 of the housing 4. In this example, each of the lugs 6, 8 comprises a threaded hole, respectively 30 and 32, to receive a tightening screw, respectively 34 and 36 (Fig. 2). These screws 34 and 36 make it possible to fix, on each lug 6 and 8, the end of an electric cable.

[0034]

[0023] The button 10 is mounted projecting from the upper face 12 of the housing 4. The button 10 allows the circuit breaker 2 to be manually moved between a tripped state and a non-tripped state. In the non-tripped state, the lugs 6 and 8 are electrically connected to each other so that current flows freely through the circuit breaker 2. Conversely, in the tripped state, the lugs 6 and 8 are electrically insulated from each other and current can no longer flow through the circuit breaker 2. For example, when the button 10 is in a high position, shown in Figure 2, the circuit breaker 2 is in the tripped state. When the button 10 is pushed downwards, it reaches a low position in which the circuit breaker is in its non-tripped state.The up and down positions are stable positions, i.e., once they are reached, it is no longer necessary to manually exert force on the button 10 to hold it in either the up or down position. Typically, the button 10 is used to manually reset the circuit breaker 2, i.e., manually switch the circuit breaker 2 from its tripped state to its non-tripped state.

[0035]

[0024] Inside the housing 4, the circuit breaker 2 comprises in particular components which make it possible to automatically switch the circuit breaker 2 from the non-tripped state to the tripped state in the event of an overcurrent and in the event of a short circuit. Here, these components are similar or identical to those described in application EP0526355A1 except that the circuit breaker 2 additionally comprises a short-circuit protection mechanism 40. As described in the introduction to the present application, this mechanism 40 makes it possible to accelerate the switching of the circuit breaker 2 to its tripped state in the event of a short circuit. Conversely, in the absence of a short circuit, the mechanism 40 has a negligible influence on the operation of the circuit breaker. Thus, the tripping threshold, noted Si hereinafter, beyond which the circuit breaker 2 automatically switches to its tripped state can be configured without taking into account the presence of the mechanism 40. For example, this threshold Si is less than 100 A or 60 A.Under these conditions, in the presence of a simple overcurrent corresponding to a current whose intensity exceeds the threshold Si while remaining below 500 A or 1000 A, the circuit breaker switches to its tripped state without intervention of the mechanism 40. More precisely, in the event of a simple overcurrent, the intervention of the mechanism 40 in the switching of the circuit breaker 2 is negligible and does not play a major role. Conversely, in the presence of a short circuit, the intensity increases very quickly and exceeds 1000 A, and can reach more than 4000 A. It is only in this case that the mechanism 40 plays a major role in accelerating the switching of the circuit breaker 2 to its tripped state and thus preventing the circuit breaker and the electrical circuit it protects from being damaged. For example, from 1000 A, the mechanism 40 assists in switching the circuit breaker.For this, here, from 1000 A, the mechanism 40 contributes more than 10% or 20% to the torque exerted on a lever 100 (Fig. 4) for unlocking which triggers the switching to the tripped state. Beyond 4000 A, here, the mechanism 40 is capable of switching, on its own, the circuit breaker to its tripped state.

[0036]

[0025] Figure 2 shows the different subassemblies of components and elements contained in the housing 4. With the exception of the mechanism 40, these subassemblies and elements are identical or practically identical to those described in application EP0526355A1. Thus, subsequently, the characteristics of these known subassemblies and elements are not described in detail unless they interact with the short-circuit protection mechanism 40.

[0037]

[0026] More specifically, the circuit breaker 2 comprises the following subassemblies and elements:

[0038] - a fixed support 42 of electrical contacts,

[0039] - a mobile crew 44,

[0040] - a locking subassembly 46,

[0041] - an electrical subassembly 48,

[0042] - a 50 bar, and

[0043] - a manual actuation subassembly 52.

[0044]

[0027] The fixed support 42 is fixed, without any degree of freedom, to the housing 4 and to the terminal 6. The support 42 is shown in more detail in FIG. 3. It comprises a branch 60 which extends vertically, in a plane P parallel to the directions Y and Z, from a proximal lower end 62 to a distal upper end 64. The end 62 is mechanically and electrically permanently connected to the terminal 6. The end 64 comprises a fixed electrical contact 66 facing the mobile assembly 44. Here, this contact 66 is a metal pad fixed, without any degree of freedom, on the end 64.

[0045]

[0028] The support 42 also comprises a branch 70 which extends vertically, in the plane P, parallel to the branch 60, from a proximal lower end 72 to a distal upper end 74. The end 72 is permanently electrically connected to the terminal 8. The end 74 comprises a fixed electrical contact 76 facing the mobile assembly 44. Here, this contact 76 is a metal pad fixed, without any degree of freedom, on the end 74.

[0046]

[0029] The branch 70 is electrically isolated from the branch 60, in the disconnected state, by an air gap 78 which extends vertically between these two branches. Here, the air gap 78 further forms a disc located halfway up the branches 60, 70.

[0047]

[0030] The branches 60, 70 are made of electrically conductive material.

[0048]

[0031] The mobile assembly 44 is, for example, identical to that described in application EP0526355A1. This assembly 44 comprises in particular:

[0049] - a mobile support 80,

[0050] - a spring mechanism 82, and

[0051] - a lock 84.

[0052]

[0032] The movable support 80 is shown in more detail in Figure 3. The movable support 80 comprises a conductive plate 90 and two movable contacts 92 and 94 fixed, without any degree of freedom, on the plate 90. The plate 90 is made of electrically conductive material and the contacts 92 and 94 are metal pads. Thus, the contacts 92 and 94 are electrically connected to each other permanently via the conductive plate 90.

[0053]

[0033] The movable support 80 is movable between a closed position, shown in Figures 3 and 5, and an open position shown in Figure 2. In the closed position, the contacts 92, 94 bear directly on, respectively, the fixed contacts 66 and 76. Thus, in the closed position, the current can freely flow between the terminals 6 and 8. In the open position, the contacts 92, 94 are moved away, respectively, from the fixed contacts 66, 76 so that the current can no longer flow between the terminals 6 and 8.

[0034] The spring mechanism 82 permanently urges the movable support 80 towards its open position.

[0054]

[0035] The lock 84 is capable of switching between a locked position shown in Figures 3 and 5, and an unlocked position shown in Figure 2. In the locked position, the lock 84 holds the movable support 80 in its closed position against the return force of the spring mechanism 82. In the unlocked position, the lock 84 allows the movable support 80 to move towards its open position.

[0055]

[0036] The locking subassembly 46 is shown in more detail in Figure 4. The subassembly 46 is permanently electrically isolated from the current to be interrupted. It comprises an unlocking lever 100 pivotally mounted around a pivot axis 102 and a secondary bimetallic strip 104 for thermal compensation.

[0056]

[0037] The lever 100 extends vertically from a lower end 110 to an upper end 112. The end 110 is located below the axis 102 while the end 112 is located above this axis 102. At the axis 102, the lever 100 comprises a bar 114 which extends horizontally. The ends of this bar 114 are received in corresponding housings arranged in the front 20 and rear faces of the housing 4. This bar 114 and these housings are shaped to form a pivot connection which allows the lever 100 to pivot about the axis 102. More precisely, the lever 100 pivots about the axis 102 between an upright position, shown in FIG. 5, and a retracted position. In the upright position, the latch 84 abuts the upper end 112, which holds the latch in its locked position.In the retracted position, the lock 84 is no longer in abutment on the end 112, which frees the movement of the lock 84 towards its unlocked position. To move from the raised position to the retracted position, the lever 100 pivots around the axis 102 in the direction D shown in FIG. 4.

[0057]

[0038] The secondary bimetallic strip 104 makes it possible to limit the variations in the threshold Si caused by the variations in the temperature of the external environment in which the circuit breaker 2 is located. This bimetallic strip 104 extends along the lever 100 from a lower end 122 to an upper end 124. The lower end 122 is fixed, without any degree of freedom, on a rear face of the lever 100. The rear face of the lever 100 is that located on the side opposite the fixed support 42. The end 122 is located at the axis 102 or above the axis 102. In this embodiment, the end 122 is located at the axis 102. The upper end 124 is located above the end 112. The bimetallic strip 104 is designed to curve backwards, that is to say here in the direction X. Thus, when the temperature of the external environment increases, the end 124 moves in the X direction.

[0058]

[0039] The locking subassembly 46 also comprises a return mechanism 130 which permanently urges the lever 100 towards its upright position. In this embodiment, the mechanism 130 comprises two elastic strips 132 and 134. The distal end of these strips 132, 134 bears on the lateral face 20 of the housing 4. The proximal end of these strips 132, 134 is here fixed, without any degree of freedom, on the bimetallic strip 104.

[0059]

[0040] The electrical subassembly 48 is shown in more detail in Figure 3. This subassembly 48 is crossed by the current to be interrupted when the circuit breaker 2 is in its non-disconnected state. For this purpose, it is permanently electrically connected, on one side, to the terminal 8 and, on the opposite side, to the branch 70 of the fixed support 42. The subassembly 48 comprises a main bimetallic strip 140 crossed by the current to be interrupted when the circuit breaker 2 is in its non-disconnected state. For this purpose, the bimetallic strip 140 is made of conductive material. The cross-section of the bimetallic strip 140 is dimensioned so that this bimetallic strip is not damaged during normal use of the circuit breaker 2. In particular, the bimetallic strip 140 is designed to withstand, for a very short period of time, a high intensity current. Here, the 140 bimetallic strip is in the shape of an inverted “U”.The free end of one vertical branch of the “U” is directly connected to the terminal 8 and the free end of the other vertical branch of the “U” is directly connected, via a horizontal track, to the lower end 72 of the branch 70. The free ends of the branches of the inverted “U” are fixed, without any degree of freedom, respectively, to the terminal 8 and to the horizontal track. Thus, the horizontal bar of the inverted “U” forms the upper end of the bimetallic strip 140. When the current intensity increases, the bimetallic strip 140 heats up by the Joule effect. When the bimetallic strip 140 heats up, it bends which moves its upper end 142 in the X direction.

[0060]

[0041] The bar 50 is shown in more detail in Figure 5. The bar 50 transmits to the locking subassembly 46 the movement, in the X direction, of the end 142 of the bimetallic strip 140 to pivot the lever 100 towards its retracted position. For this purpose, here, the bar 50 is slidably mounted in horizontal grooves arranged, respectively, in the front face and in the rear face of the housing 4. The bar 50 extends horizontally between an end 152, opposite the end 142 of the bimetallic strip 140, and an end 154 opposite the end 124 of the bimetallic strip 104. There is generally a clearance between the ends 152, 142 and / or between the ends 154, 124 which must be taken up before the circuit breaker 2 can trip. Once this clearance has been taken up, when the end 142 pushes the bar 50 in the direction X, this moves, in the direction X and by the same distance, the end 124 of the bimetallic strip 104.Moving the end 124 in the X direction pivots the lever 100 to its retracted position. Thus, the bar 50 and the bimetallic strip 104 form a mechanical connection which mechanically connects the bimetallic strip 140 to the lever 100.

[0061]

[0042] The strip 50 is made, at least in part, of an electrically insulating material to electrically insulate the subassembly 46 from the subassembly 48.

[0062]

[0043] The bar 50 also includes a central opening crossed by the subassembly 52 so that the latter is mechanically connected to the mobile assembly 44.

[0063]

[0044] By way of illustration, the subassembly 52 is, for example, identical to that described in application EP0526355A1. It comprises in particular the button 10 as well as the various parts which make it possible to reset the circuit breaker 2 in response to a downward movement of the button 10 and, in response to a movement in the opposite direction of the button 10, to switch the circuit breaker 2 into its tripped state.

[0064]

[0045] The short-circuit protection mechanism 40 comprises a single current loop 160 and a magnetic target 162 opposite the loop 160.

[0065]

[0046] Loop 160 is shown in detail in Figure 3. Loop 160 is crossed by the current to be interrupted when circuit breaker 2 is in its non-disconnected state. Loop 160 is wound around an axis 164 parallel to direction X. Loop 160 functions like a turn of a coil and generates a magnetic field parallel to direction X when a current flows through it. The standard of the magnetic field generated by loop 160 increases as a function of the intensity of the current flowing through it. In this embodiment, to save space, already existing parts of the circuit breaker 2 are used to form the loop 160. More precisely, in this embodiment, the loop 160 is formed, successively by winding around the axis 164 in an anticlockwise direction, by the branch 70, the contacts 76, 94, the plate 90, the contacts 92, 66 and the branch 60.In Figure 3, an example of the direction of current flow is represented by arrows located in the parts crossed by this current. As illustrated in Figure 3, the current begins by rising vertically in the branch 70 located to the right of the axis 164, then passes above the axis 164 by crossing the plate 90, then descends vertically in the branch 60 located to the left of the axis 164.

[0066]

[0047] The target 162 is shown in more detail in Figure 4. The magnetic field generated by the loop 160 exerts a force F on the target 162 which forces the lever 100 towards its retracted position. Thus, the higher the intensity of the current to be interrupted, the greater the amplitude of the force F and the more easily the lever 100 switches towards its retracted position. Here, the force F exerted on the target 162 is considered negligible or weak as long as the current intensity is less than 1000 A. Conversely, the action of the force F on the target 162 becomes significant for high intensity currents. Thanks to this, in the event of a short circuit, the lever 100 switches more quickly towards its retracted position and the circuit breaker 2 therefore switches more quickly towards its tripped state in the event of a short circuit. For this purpose, the target 162 is made of a magnetic material which is attracted by the loop 160 when a current passes through it.For example, the target 162 is made entirely of a ferromagnetic material such as a soft ferromagnetic material. Here, the target 162 is directly fixed, without any degree of freedom, on the lower end 110 of the lever 100. More precisely, the target 162 is centered on the axis 164 and extends mainly in a plane perpendicular to this axis 164. For example, the target 162 is substantially a parallelogram whose width and length are contained in a vertical plane parallel to the directions Y and Z in the upright position of the lever 100. When the loop 160 is crossed by a current, the target 162 is attracted by the magnetic field generated by the loop 160 which urges the lever 100 towards its retracted position.

[0067]

[0048] During operation of the circuit breaker, the current passes successively through the terminal 8, the bimetallic strip 140, the branch 70, the plate 90, the branch 60 and then the terminal 6. In the event of an overcurrent, the current exceeds the threshold Si. The bimetallic strip 140 heats up by the Joule effect and the end 142 moves in the X direction. This moves the bar 50 in the X direction and therefore the end 124 of the bimetallic strip 104. This movement of the bimetallic strip 104 drives the lever 100 from its upright position to its retracted position. When the lever 100 reaches the retracted position, the latch 84 switches from its locked position to its unlocked position. This switching causes, in response, the movement of the movable support 80 from its closed position to its open position. The circuit breaker 2 is then in its tripped state.In the case of an overcurrent, the current intensity increases slowly enough for the circuit breaker 2 to switch to its tripped state well before a high current flows through it. In this case, the amplitude of the force F remains limited so that it is mainly the deformation of the bimetallic strip 140 which causes the switching to the tripped state.

[0068]

[0049] In the event of a short circuit, the current intensity increases very rapidly so that a high current intensity is reached very quickly. In the presence of a high current intensity, the force F exerted on the target 162 is significant, which triggers switching to the disconnected state more rapidly than in the event of a simple overcurrent. Indeed, in this case, the lever 104 is pushed towards its retracted position mainly by the action of the attractive force F.

[0069]

[0050] Chapter III: Variants:

[0070]

[0051] Variants of the protection mechanism:

[0071]

[0052] Alternatively, the protection mechanism 40 comprises several current loops wound, in the same direction, around the axis 164. In this case, each loop corresponds to a turn of a coil.

[0072]

[0053] The target 162 may be made of other materials. For example, as a variant, the target 162 is a permanent magnet in the case where the circuit breaker is used in a context where it is permissible for it to permanently generate a magnetic field.

[0073]

[0054] Other methods of connecting the target 162 are possible. For example, in one variant, the target 162 is fixed to the unlocking lever 100 at a location between the pivot axis 102 and the upper end 112. For example, for this, the axis 102 is moved downwards to a level located below the current loop 160 so that this current loop and the target remain facing each other even if the target is located above the pivot axis 102. In this variant, the lower end 110 of the lever can be merged with the bar 114.

[0074]

[0055] Other variants of the circuit breaker:

[0056] The fixed and / or movable contacts are not necessarily materialized by metal studs but may simply correspond to electrical contact zones located on the distal ends of the branches 60 and 70 and / or on the plate 90.

[0075]

[0057] Alternatively, there is no thermal compensation. In this case, the secondary bimetallic strip 104 is simply replaced by a part of the same shape which does not bend in response to variations in the temperature of the external environment.

[0076]

[0058] Other embodiments of the return mechanism 130 are possible. For example, the mechanism 130 and the bimetallic strip 104 form a single block of material. In another variant, the strips 132, 134 are replaced by a helical spring. Such a helical spring can bear directly on the lever 100 instead of bearing on the bimetallic strip 104.

[0077]

[0059] Alternatively, the main bimetallic strip may have other conformations such as, for example, a “W” or inverted double “U” conformation.

[0078]

[0060] The main bimetallic strip can also be placed between the terminal 6 and the branch 60.

[0079]

[0061] What has been described here applies regardless of the configuration of the lock 84.

[0080]

[0062] Other embodiments of the bar 50 are possible. For example, as a variant, the bar pivots when pushed by the bimetallic strip 140 instead of sliding.

[0081]

[0063] Alternatively, the circuit breaker comprises a single fixed contact and a single movable contact which mechanically bears on this fixed contact in its closed position. In this case, the movable contact is permanently connected to one end of the bimetallic strip 140, for example, by a flexible electrical conductor such as a metal braid or a flexible conductive wire. This conductor is sufficiently flexible so as not to hinder the movement of the movable support between its open and closed positions while keeping it permanently electrically connected to the bimetallic strip 140. Thus, in this embodiment, when the circuit breaker is in its non-disconnected state, the current to be interrupted passes successively through the bimetallic strip 140, the flexible conductor, the movable contact and then the fixed contact.

[0082]

[0064] Several of the variants described above can be combined in the same embodiment.

[0083]

[0065] Chapter IV: Advantages of the embodiments described:

[0066] Placing the magnetic target 162 on the unlocking lever 100 makes it easier to reduce the size of the short-circuit protection mechanism 40. Indeed, in this case, the magnetic target 162 is not crossed by the current to be interrupted. Therefore, it is not necessary to configure this target 162 so that it can withstand, without damage, the passage of a high intensity current. This therefore makes it possible to reduce the dimensions of the target without degrading the operation of the circuit breaker. This also makes it possible to use magnetic materials to produce the target 162 which are not necessarily good electrical conductors.The fact that the constraints on the dimensions and material of the target 162 are less, also makes it easier to adjust the sensitivity of the circuit breaker with regard to short circuits, in particular by adjusting the dimensions and material of the target.

[0084]

[0067] In addition, placing the target 162 on the unlocking lever 100 makes it possible to limit the size of the circuit breaker compared to the embodiment described in application US4990882A where the target and the main bimetallic strip form a single piece. Indeed, in the latter case, the current loop must necessarily be located behind the main bimetallic strip, which increases the size of the circuit breaker. In addition, this also makes it possible to limit the weight of the circuit breaker because it is not necessary to add a significant additional mass of conductive material to create the current loop.

[0085]

[0068] Fixing the target 162 on the lower end 110 of the unlocking lever brings the target closer to the terminal 6, which makes it possible to limit the size of the current loop 160 and therefore to further limit the size of the circuit breaker.

[0086]

[0069] Using the fixed 42 and mobile 80 supports to form the current loop 160 makes it possible to limit the size of the circuit breaker because these supports 42, 80 then fulfill two functions, namely, the support function for the contacts 66, 76, 92, 94 and the current loop function. In addition, the use of two fixed contacts 66, 76 and two mobile contacts 92, 94 to interrupt the current makes it possible to avoid the use of a flexible electrical conductor which permanently electrically connects the mobile support to the main bimetallic strip. The use of two fixed contacts and two mobile contacts also makes it possible, at an equal distance between the fixed 42 and mobile 80 supports, to double the length of the air gap that the current must cross to circulate. More precisely, to flow, the current must first cross a first air gap between contacts 76, 94 then a second air gap between contacts 92, 66.This increases the breaking capacity of the circuit breaker.

[0087]

[0070] Using the branches 60, 70 of the fixed support 42 to form the current loop 160 simplifies the production of the circuit breaker.

[0071] The use of the secondary bimetallic strip 104 makes it possible to limit the sensitivity of the circuit breaker to variations in the temperature of the external environment. In particular, this limits the variations in the threshold Si as a function of the temperature of the external environment.

Claims

Claims 1. Thermal circuit breaker comprising: - a first and a second fixed terminal (6, 8), each of these fixed terminals being capable of being connected to an electrical cable or plugged into an electrical connector, - a fixed support (42) comprising a first fixed contact (66) electrically permanently connected to the first terminal, - a movable support (80) comprising a first movable contact (92), this movable support being movable between a closed position in which the first movable contact rests on the first fixed contact to allow a current to pass between the first and second terminals, and an open position in which the first movable contact is moved away from the first fixed contact to interrupt the passage of current between the first and second terminals, - a lock (84) capable of switching between: - a locked position in which it holds the mobile support in its closed position, and - an unlocked position in which it allows the mobile support to move to its open position, - an unlocking lever (100) pivotally mounted around a pivot axis (102) and electrically insulated from the current to be interrupted, this unlocking lever extending from a first end (112) to a second end (110) and being movable, in rotation around its pivot axis, between: - an upright position in which the lock is abutted on its first end to maintain the lock in its locked position, and - a retracted position in which the lock is no longer in contact with the first end of the unlocking lever, which frees the movement of the lock towards its unlocked position, - a main bimetallic strip (140) through which the current to be interrupted passes, this main bimetallic strip being able to bend to move the unlocking lever from its upright position to its retracted position when the intensity of the current passing through it exceeds a threshold, - a current loop (160) crossed by the current to be interrupted, this current loop generating a magnetic field which is a function of the intensity of the current which crosses it, and - a magnetic target (162) opposite the current loop, this magnetic target exerting on the unlocking lever a force which mechanically forces the unlocking lever towards its retracted position so that the lock switches towards its unlocked position all the more quickly as the intensity of the current which passes through the current loop is high, characterized in that the magnetic target (162) is fixed, without any degree of freedom, on the unlocking lever.

2. Circuit breaker according to claim 1, in which: - the second end (110) of the unlocking lever is located, relative to the pivot axis, on the side opposite its first end (112), and - the magnetic target (162) is directly fixed on this second end.

3. A circuit breaker according to any preceding claim, wherein - the fixed support (42) comprises a second fixed contact (76) permanently electrically connected to the second fixed terminal (8), this second fixed contact being electrically insulated from the first fixed contact in the open position of the mobile support, - the mobile support comprises a second mobile contact (94) which rests on the second fixed contact in the closed position of the mobile support and which is distant from the second fixed contact in the open position of the mobile support, this second mobile contact being electrically connected permanently to the first mobile contact, and - the fixed support and the movable support are shaped to form the current loop when the movable support is in its closed position.

4. Circuit breaker according to claim 3, in which the fixed support comprises: - a first electrically conductive branch (60) which extends, in a plane of the fixed support, from a proximal end (62) permanently electrically connected to the first terminal (6), to a distal end (64) at which the first fixed contact is located, and - a second electrically conductive branch (70) which extends, in the plane of the fixed support, parallel to the first branch, from a proximal end (72) permanently electrically connected to the second terminal, to a distal end (74) at which the second fixed contact is located, this second branch being electrically insulated from the first branch in the open position of the mobile support by an air gap (78) which extends between these two branches, the meeting of the first and second branches and of the mobile support in its closed position forming the current loop.

5. Circuit breaker according to any one of the preceding claims, in which the circuit breaker comprises a secondary bimetallic strip (104) to compensate for temperature variations in the external environment, this secondary bimetallic strip being electrically isolated from the current to be interrupted.

6. Circuit breaker according to any one of the preceding claims, in which the circuit breaker comprises a mechanical connection capable of transferring the movement of the main bimetallic strip when it bends, to the unlocking lever to move the unlocking lever from its upright position to its retracted position, this mechanical connection comprising a bar (50) made of electrically insulating material to electrically insulate the unlocking lever (100) from the current to be interrupted which flows in the main bimetallic strip.

7. Circuit breaker according to claim 6, in which the bar (50) is able to slide in grooves when the main bimetallic strip bends.

8. A circuit breaker according to any preceding claim, wherein the circuit breaker comprises a spring mechanism (82) continuously biasing the movable support towards its open position.

Images