Thermal circuit breaker

Abstract

The invention relates to a thermal circuit breaker in which: - a stationary end of a main bimetallic strip is attached, without any degree of freedom, to a lug of the circuit breaker; - a mechanism (38) for adjusting a thermal trip threshold of the circuit breaker includes: - a spring (132), mechanically separate from the main bimetallic strip, which exerts a return force, by means of a part (50, 100, 104) that does not carry the current to be interrupted, and which prevents the movement of a movable end of the main bimetallic strip; and - an adjustment screw (162) engaged with the spring so that rotating this screw allows the return force of the spring (132) to be adjusted without modifying the initial position of the stationary end (142) of the main bimetallic strip.

Description

Thermal circuit breaker [1] The invention relates to a thermal circuit breaker. [2] A thermal circuit breaker interrupts a current when its intensity exceeds a predetermined threshold. To achieve this, thermal circuit breakers use a main 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 bending, the circuit breaker trips. The current intensity at the moment when the bending of the bimetallic strip is sufficient for the circuit breaker to trip is subsequently called the "thermal tripping threshold" and noted as the "STH threshold". The S™ threshold depends on the thickness of the initial clearance that the moving end of the main bimetallic strip must take up before starting to force the part that will cause it to trip. Indeed, the greater the thickness of this clearance, the more the main bimetallic strip must bend to take up the clearance and therefore the higher the STH threshold.Thus, since the STH threshold depends on the thickness of this initial clearance, to adjust this threshold S™, it is known to use an adjustment mechanism which makes it possible to adjust the initial clearance. An example of such an STH threshold adjustment mechanism is described in application EP0526355A1. The STH threshold adjustment mechanism of application EP0526355A1 comprises an adjustment screw accessible from outside the circuit breaker housing. When this adjustment screw is turned, this modifies the initial position of the movable end of the main bimetallic strip and therefore the thickness of the initial clearance to be taken up. To do this, it is necessary to provide an electrical connection between this bimetallic strip and the circuit breaker input lug which is sufficiently flexible to accommodate the movement of the main bimetallic strip by the adjustment screw. Such flexibility is difficult to obtain for circuit breakers for which the rating is high.Indeed, in the latter case, all the conductive parts have a large cross-section to withstand the passage of high current. However, a large cross-section of the conductive parts goes against their flexibility. To overcome this contradiction, it has already been proposed to connect the stationary end of the main bimetallic strip to the input terminal by means of a conductive braid or a flexible blade. However, this known solution is not completely. satisfactory because it complicates the construction of the circuit breaker. In addition, this adjustment screw is not electrically isolated from the current to be interrupted, which can be a source of accident if the thermal trip threshold is set while the circuit breaker is crossed by the current to be interrupted. [3] State of the art on mechanisms for adjusting the thermal trip threshold of a circuit breaker can also be found in the following documents: US20060197645A1 and US4990882A. [4] In the context of thermal switches, prior art is known from US4429296A. [5] It is also emphasized that the S™ threshold is different from an electromagnetic tripping threshold, noted “SEM threshold”, which can also exist in a thermal circuit breaker. Indeed, due to the thermal inertia of the main bimetallic strip, it takes a certain amount of time for the deformation of the main bimetallic strip to reach the degree of curvature that causes it to trip. However, in the event of a short circuit, the current intensity increases very quickly and reaches very high values ​​before the curvature of the main bimetallic strip is sufficient to trip the circuit breaker. To overcome this drawback, known thermal circuit breakers additionally implement a short-circuit protection device 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 device is, for example, described in application DE2717115A1.In application DE2717115A1, the protection device 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 according to the intensity of the current to be interrupted. This produces an electromagnetic force which attracts the target and whose amplitude is proportional to the intensity of the generated magnetic field. When the amplitude of the electromagnetic force is greater than the restoring force of a spring, this causes the movement of a lever which trips the circuit breaker. The intensity of the magnetic field increases as quickly as the intensity of the current. Thus, in the event of a short circuit, it is not the main bimetallic strip which trips the circuit breaker but the short-circuit protection mechanism.The current intensity at the time the amplitude of the electromagnetic force is sufficient for the circuit breaker. trips is equal to the S EM threshold. The SEM threshold is typically five or ten times higher than the STH threshold. Similar to what has been described for the thermal trip threshold, there are also mechanisms for adjusting the S EM threshold. Since in the case of electromagnetic tripping, it is the exceeding of a spring return force by the amplitude of the generated electromagnetic force that causes the circuit to trip, it is known to adjust the SEM threshold by adjusting the return force of the return spring. Such a mechanism for adjusting the SEM threshold is, for example, described in application DE2717115A1. However, these mechanisms for adjusting the S EM threshold are different and independent from the mechanisms for adjusting the STH threshold. [6] The invention aims to propose a thermal circuit breaker equipped with a threshold adjustment mechanism S™ which can be used even when the rating is high and this without complicating the production of the circuit breaker and limiting the risks of electrical accidents. [7] The invention is set forth in the attached set of claims. [8] The invention will be better understood by reading the description which follows, given solely as a non-limiting example and made with reference to the drawings in which: - Figure 1 is an illustration, in perspective, of a circuit breaker, - figure 2 is a view, in vertical section, of the circuit breaker of figure 1, - figure 3 is a perspective view of a fixed support and a mobile support of the circuit breaker of figure 1, - figure 4 is a perspective view of a locking subassembly of the circuit breaker of figure 1, and - Figure 5 is a view, in vertical section, of a return mechanism of an unlocking lever, and - Figure 6 is a vertical sectional view of an STH threshold adjustment mechanism. [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.

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

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

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

[0013] 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.

[0014] The term "very high current" refers to a current whose intensity exceeds 1000 A or 4000 A.

[0015] 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.

[0016] 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.

[0017] The symbol “*” denotes scalar multiplication.

[0018] Chapter: Example of implementation mode

[0019] Figure 1 shows a thermal circuit breaker 2 that can be used to interrupt both alternating current and direct current. This circuit breaker 2 comprises: - a housing 4 made of electrically insulating material, - terminals 6 and 8 for current output and input, - a button 10 for manual operation of the circuit breaker.

[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: - an upper wall 12, - a lower wall 14, - a front wall 16 and a rear wall not visible in figure 1, and - vertical side walls 18 and 20 located on either side of the front wall 16.

[0021] The terminals 6 and 8 are fixed, without any degree of freedom, to the housing 4. These terminals 6, 8 are each intended to be connected to an electric cable or plugged into an electrical connector so that a current flows through the circuit breaker 2. In this example, the lugs 6 and 8 protrude from the lower wall 14 of the housing 4. In this example, each of the lugs 6, 8 has a threaded hole, respectively 30 and 32, to receive a clamping screw. These clamping screws make it possible to fix, on each lug 6 and 8, the end of an electric cable. Each lug 6 and 8 is here formed from a single block of material.

[0022] The button 10 is mounted protruding from the upper wall 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 an up position, shown in Figure 2, the circuit breaker 2 is in the tripped state. When the button 10 is pushed down, it reaches a down 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 maintain 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 untripped state. The button 10 can also be used to manually disarm the circuit breaker 2, i.e., manually switch the circuit breaker 2 from its untripped state to its tripped state.

[0023] Inside the housing 4, the circuit breaker 2 includes in particular components which allow the circuit breaker 2 to be automatically switched from the non-tripped state to the tripped state in the event of an overcurrent.

[0024] Figure 2 represents the different subassemblies of components and elements contained in the housing 4. With the exception of a mechanism 38 for adjusting the threshold S TH, these subassemblies and elements are identical or practically identical to those described in the application EP0526355A1. Thus, subsequently, the characteristics of these known subassemblies and elements are not described in detail unless they interact with the mechanism 38 for adjusting the threshold S TH.

[0025] More specifically, circuit breaker 2 includes the following subassemblies and elements: - a fixed support 42 of electrical contacts, - a mobile crew 44, - a locking subassembly 46, - a main bimetallic strip 48, - a 50 bar, and - a manual actuation subassembly 52.

[0026] 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.

[0027] 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.

[0028] Branch 70 is electrically isolated from branch 60, in the disconnected state, by an air gap 78 which extends vertically between these two branches. Here, air gap 78 further forms a disc located halfway up branches 60, 70.

[0029] The branches 60, 70 are made of electrically conductive material.

[0030] The mobile assembly 44 is, for example, identical to that described in application EP0526355A1. This assembly 44 comprises in particular: - a mobile support 80, - a spring mechanism 82, and - a lock 84.

[0031] The movable support 80 is shown in more detail in Figure 3. The movable support 80 comprises a conductive plate 90 and two fixed movable contacts 92 and 94, 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.

[0032] The movable support 80 is movable between a closed position, shown in FIG. 3, and an open position shown in FIG. 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.

[0033] The spring mechanism 82 continuously biases the movable support 80 towards its open position.

[0034] The latch 84 is capable of switching between a locked position shown in FIG. 5, and an unlocked position. In the locked position, the latch 84 holds the movable support 80 in its closed position against the return force of the spring mechanism 82. In the unlocked position, the latch 84 allows the movable support 80 to move to its open position.

[0035] The locking subassembly 46 is shown in more detail in Figure 4. The subassembly 46 is not crossed by 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.

[0036] 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 provided in the front and rear walls 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, in the undisconnected state, the latch 84 abuts the upper end 112 which keeps it in its locked position. More precisely, in the upright position, the stop 116 formed by the end of the lock 84 is supported on the end 112 (Figures 5 and 6) of the lever 100 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 upright position to the retracted position, the lever 100 pivots around the axis 102 in the direction D shown in Figure 4.

[0037] The secondary bimetallic strip 104 makes it possible to limit the variations in the STH threshold 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 bend backwards, that is to say here in the X direction. Thus, when the temperature of the external environment increases, the end 124 moves in the X direction.

[0038] The locking subassembly 46 also includes a return mechanism 130 which permanently biases the lever 100 towards its upright position. This mechanism 130 is shown in detail in FIG. 5. In this embodiment, the mechanism 130 includes a helical spring 132. This spring 132 extends along an axis A132 from one end 134 directly resting on the rear face of the lever 100 to an opposite end 136. The axis AI 32 is parallel to the X direction. A hollow housing 138 is provided in the rear face of the lever 100 to receive the end 134 of the spring 132 and thus prevent it from sliding against this rear face. The spring 132 passes through a hole 139 provided in the bimetallic strip 104 so that the end 136 can bear against the side wall 18.

[0039] The main bimetallic strip 48 is crossed by the current to be interrupted when the circuit breaker 2 is in its undisconnected 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 bimetallic strip 48 is made of conductive material. The cross-section of the bimetallic strip 48 is dimensioned so that this bimetallic strip is not damaged during normal use of the circuit breaker 2. In particular, the bimetallic strip 48 is designed to withstand, for a very short period of time, to a very high current intensity. Here, the bimetallic strip 48 is in the shape of an inverted “U”. It therefore comprises two fixed lower ends 142 and 144 (Figure 3) and a movable upper end 146. The end 142 is mechanically and electrically permanently connected to the terminal 8. The mechanical and electrical connection between the terminal 8 and the end 142 does not need to be flexible to allow adjustment of the position of the bimetallic strip 48. Under these conditions, here, the end 142 is directly fixed without any degree of freedom on the terminal 8. For example, the end 142 is directly welded to a vertical face of the terminal 8. The end 144 is mechanically and electrically permanently connected to the branch 70 of the fixed support 42. This mechanical and electrical connection between the branch 70 and the end 144 does not need to be flexible to allow adjustment of the initial position of the end 146 of the bimetallic strip 48.Therefore, here, the end 144 is also directly fixed without any degree of freedom to the branch 70, for example, by welding.

[0040] The horizontal bar of the inverted "U" forms the upper end 146 of the bimetallic strip 48. As the current increases, the bimetallic strip 48 heats up due to the Joule effect. As the bimetallic strip 48 heats up, it bends from an initial state to a bent state. This moves its end 146 in the X direction from an initial position to an advanced position that triggers the switching of the circuit breaker 2 to its tripped state. At the same time, the ends 142 and 144 are stationary and each remain in their initial positions.

[0041] The bar 50 is shown in more detail in Figure 2. The bar 50 transmits to the locking subassembly 46 the movement, in the X direction, of the end 146 of the bimetallic strip 48 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 wall 16 and in the rear wall of the housing 4. The bar 50 extends horizontally between an end 152, opposite the end 146 of the bimetallic strip 48, and an end 154 opposite the end 124 of the bimetallic strip 104. There is generally a clearance between the ends 152, 146 and / or between the ends 154, 124 which must be taken up before the circuit breaker 2 can trip. Once this play has been taken up, when the end 146 pushes the bar 50 in the X direction, this moves, in the X direction and by the same distance, the end 124 of the bimetallic strip 104.Moving end 124 in the X direction pivots lever 100 toward. its retracted position. Thus, the bar 50 and the bimetallic strip 104 form a mechanical connection which mechanically connects the bimetallic strip 48 to the lever 100.

[0042] The strip 50 is made, at least in part, of an electrically insulating material to electrically insulate the subassembly 46 from the electric current to be interrupted which passes through the bimetallic strip 48.

[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.

[0044] By way of illustration, the subassembly 52 is, for example, identical to that described in application EP0526355A1. It includes 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 to its tripped state.

[0045] The mechanism 38 for adjusting the STH threshold is shown in more detail in FIG. 6. This mechanism 38 is designed to exert an adjustable restoring force which opposes the movement of the end 146 in the X direction when the bimetallic strip 48 heats up. Thus, the greater this restoring force, the higher the STH threshold. For example, this threshold S™ is less than or equal to 100 A or 60 A. Unlike the adjustment mechanism such as that disclosed in application EP0526355A1, the mechanism 38 does not modify the initial state of the bimetallic strip 48. For this purpose, the mechanism 38 comprises the stop 116, the spring 132 as well as a nut 160 and an adjusting screw 162. The spring 132 already exerts a return force on the lever 100 which opposes the movement of this lever towards its retracted position and therefore the movement of the end 146 of the bimetallic strip 48 in the direction X.The screw 162 makes it possible to adjust the return force exerted by the spring 132 on the rear face of the lever 100 in order to be able to adjust the threshold STH. Here, the nut 160 is fixed, without any degree of freedom, on the wall 18 and centered on the axis AI. 32 . The screw 162 comprises a rod 164 and a head 166. The head 166 is shaped to be driven in rotation by the blade of a screwdriver. Here, the head 166 is received in a through hole 168 provided in the wall 18 so that this head 166 is accessible from outside the housing 4.

[0046] The rod 164 extends along the axis AI 32 Starting from the head 166 and going towards the inside of the housing 4, the rod 164 successively comprises: - a threaded portion 170, - a flat 172 which extends mainly in a plane perpendicular to the axis AI 32 , And - a 174 centering pin.

[0047] The threaded portion 170 is screwed inside the nut 160. The end 136 of the spring 132 bears directly on the flat 172. The pin 174 is received inside the coil of the spring 132 which forms its end 136 in order to keep the end 136 centered on the axis AI 32 and on the flat 172.

[0048] Under these conditions, when the head 166 is aimed, using a screwdriver, the flat 172 advances towards the inside of the housing 4, which compresses the spring 132 and increases the return force exerted by the spring 132 on the rear face of the lever 100. Thus, when the screw 162 is aimed, the threshold S™ increases. Conversely, when the head 166 is unscrewed, the spring 132 relaxes, which reduces the return force, without canceling it, exerted on the rear face of the lever 100. Consequently, the threshold STH decreases. The increase or decrease in the return force exerted by the spring 132 does not in any way modify the position of the lever 100 because the pivoting of the lever 100 in the opposite direction to direction D is blocked by the stop 116 when the lever 100 is in its upright position and the circuit breaker is in its non-disconnected state. The adjustment of the threshold STH using the mechanism 38 therefore does not modify the initial state of the bimetallic strip 48.

[0049] Typically, the mechanism 38 is used after the manufacture of the circuit breaker 2 is completed to reduce the variability, due to manufacturing tolerances, of the STH thresholds of a set of several circuit breakers 2. For this, preferably, the spring 132 is configured so that the mechanism 38 makes it possible to vary the return force over the largest possible range while respecting constraints on the maximum size of this spring 132.

[0050] Typically, the STH threshold is between 1.1 * l n and 1.4*l n , where the nis the nominal intensity of the current flowing through the circuit breaker 2. The adjustment of the STH threshold comprises, for example, a coarse adjustment and then a fine adjustment. During the coarse adjustment, the screw 162 is turned until the STH threshold corresponds to a tripping time of the circuit breaker 2 which is located in a desired time range [tmin; tmax] and, preferably, towards the middle of this range [tmin; tmax]. The tripping time is defined as being the time necessary for the circuit breaker 2 to switch from its non-tripped state to its tripped state when it is continuously crossed by a current whose intensity is equal to N*l n , where N is a number generally chosen equal to two, four or six. Once the coarse adjustment is completed, circuit breaker 2 is continuously crossed by a current whose intensity is equal to 1.1*l n. If, under these conditions, the circuit breaker 2 does not switch to its tripped state after a predetermined duration generally greater than or equal to 1 min or 5 min or 1 hour, the setting of the S™ threshold is complete. Conversely, if the circuit breaker 2 switches before the end of this predetermined duration, the screw 162 is turned again to slightly increase the STH threshold while maintaining a tripping time within the range [tmin; tmax]. This last step can be repeated several times until the appropriate setting is found.

[0051] Typically, once the STH threshold adjustment is complete, the head 166 of the screw 162 is sealed, for example with epoxy resin, to permanently immobilize the screw 162 and prevent any further adjustment. If a circuit breaker structurally identical to circuit breaker 2 but of a different rating is to be manufactured, then it is preferable to replace the bimetallic strip 48 with another main bimetallic strip that has different mechanical properties and strength. Here, the mechanism 38 is not used to change the rating of circuit breaker 2.

[0052] Furthermore, in this embodiment, the circuit breaker 2 further comprises a short-circuit protection mechanism 180. This mechanism 180 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 180 has a negligible influence on the operation of the circuit breaker. Thus, the STH threshold can be set without taking into account the presence of the mechanism 180. Under these conditions, in the presence of a simple overcurrent corresponding to a current whose intensity exceeds the STH threshold while remaining less than 500 A or 1000 A, the circuit breaker switches to its tripped state without intervention of the mechanism 180. More precisely, in the event of a simple overcurrent, the intervention of the mechanism 180 in the switching of the circuit breaker 2 is negligible and does not play a predominant 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 180 plays a predominant role in accelerating the switching of the circuit breaker 2 to its tripped state and thus preventing the circuit breaker and the electrical circuit that it protects from being damaged. For example, from 1000 A, the mechanism 180 assists in switching the circuit breaker. For this, here, from 1000 A, the mechanism 180 contributes more than 10% or 20% to the torque that is exerted on the unlocking lever 100 to trigger the switching. to the tripped state. Beyond 4000 A, here, the 180 mechanism is capable of switching, on its own, the circuit breaker to its tripped state.

[0053] Here, the short-circuit protection mechanism 180 comprises a single current loop 182 (Figures 2 and 3) and a magnetic target 184 (Fig. 4) opposite the loop 182. This mechanism 180 is for example identical to that described in the application filed on July 17, 2023 under number FR2307635 by the company Crouzet.

[0054] Loop 182 is shown in detail in Figure 3. Loop 182 is crossed by the current to be interrupted when circuit breaker 2 is in its non-disconnected state. Loop 182 winds around an axis 186 parallel to direction X. Loop 182 generates a magnetic field parallel to direction X when it is crossed by a current. The norm of the magnetic field generated by loop 182 increases as a function of the intensity of the current passing through it. More precisely, in this embodiment, loop 182 is formed, successively by winding around axis 186 in an anticlockwise direction, by branch 70, contacts 76, 94, plate 90, contacts 92, 66 and branch 60. In Figure 3, an example of the direction of flow of the current is represented by arrows located in the parts crossed by this current.

[0055] The target 184 is shown in more detail in Figure 4. The magnetic field generated by the loop 182 exerts a force F on the target 184 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. The target 184 is made of a magnetic material which is attracted by the loop 182 when a current flows through it. The target 184 is directly fixed, without any degree of freedom, on the lower end 110 of the lever 100. Firstly, it is the configuration of the loop 182 and the target 184 which determines the electromagnetic tripping threshold SEM of the circuit breaker 2.

[0056] During operation of the circuit breaker, the current passes successively through the terminal 8, the bimetallic strip 48, the branch 70, the plate 90, the branch 60 and then the terminal 6. In the event of an overcurrent, the current intensity exceeds the threshold S™. The bimetallic strip 48 heats up by the Joule effect and the end 146 moves in the X direction. This moves the bar 50 in the X direction and therefore the end 124 of the bimetallic strip 104. When the force exerted by the end 146 of the bimetallic strip 48 on the bar 50 exceeds the return force of the spring 132, the movement of the end 146 of the bimetallic strip 48 drives the lever 100 from its raised 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 being crossed by a very high current. In this case, the amplitude of the force F remains limited so that it is mainly the deformation of the bimetallic strip 48 which causes the switching to the tripped state.

[0057] In the event of a short circuit, the current intensity increases very rapidly so that a very high current intensity is reached very quickly. In the presence of a very high current intensity, the force F exerted on the target 184 is significant, which triggers the switching to the disconnected state more quickly 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.

[0058] Chapter III: Variants:

[0059] Variants of the STH threshold adjustment mechanism:

[0060] The return force of the spring 132 may be exerted on a part other than the unlocking lever 100. For example, this other part is another part that can be moved by the Joule effect, such as the bar 50 or the bimetallic strip 104. Thus, as a variant, the spring 132 exerts its return force directly on the bimetallic strip 104 or on the bar 50. In this case, preferably, in a similar manner to the stop 116, a stop, for example arranged in the housing 4, prevents any movement of this part under the sole action of the spring of the adjustment mechanism when the circuit breaker is in its non-tripped state. However, conversely, when the return force is directly exerted on the bar 50 or the bimetallic strip 48, the adjustment mechanism may not include a stop functionally equivalent to the stop 116. In this case, the modification of the return force of the spring of the STH threshold adjustment mechanism may slightly modify the initial position of the end 146.This does not modify the initial positions of the ends 142 and 144. The modification of the initial position of the end 146 is small because the stiffness of the bimetallic strip 48 is greater than the stiffness of the spring of the mechanism 38.

[0061] In another variant, the spring 132 exerts its restoring force directly on the bimetallic strip 48. For this, one end of the spring 132 bears directly on the bimetallic strip 48. In this case, the screw 162 is not necessarily isolated from the current flowing through the circuit breaker. However, the screw 162 can also be isolated from this current by other means. By way of illustration, the spring is then made of an electrically insulating material so that the screw is electrically isolated from the current flowing through the bimetallic strip 48. In this variant, preferably, a stop functionally equivalent to the stop 116 is provided. For example, this stop is arranged in the housing 4 so that the rear face of the end 146 bears on this stop in the absence of current flowing through the circuit breaker. The rear face of the end 146 is the one facing the side opposite the fixed support 42.

[0062] The spring of the return mechanism 130 and the spring of the threshold adjustment mechanism 38 S™ may be mechanically distinct from each other. In this case, the spring of the adjustment mechanism is only used to exert a return force on the end 146 of the main bimetallic strip and not to return the lever 100 to its upright position. This is the case, for example, if the spring of the adjustment mechanism bears directly on the bar 50 or the bimetallic strip 48.

[0063] Other embodiments of the spring 132 are possible. For example, instead of using a helical spring, the spring may be an elastic blade bent into a “U” shape having one branch of the “U” fixed without any degree of freedom on the rear face of the lever 100. The other branch of the “U” has a tapped hole in which the threaded portion of the screw shank is received. The screw shank also has a non-threaded portion mounted to rotate freely inside a bearing provided in the housing 4. This bearing prevents any translational movement of the screw along the axis AI 32 . Thus, the rotation of the screw brings the branches of the “U” closer or closer together, which makes it possible to adjust the restoring force exerted on the part. In this case, the nut 160 is omitted. The spring can also be a simple flexible strip, for example, mounted projecting from a rear face of the unlocking lever 100.

[0064] If necessary, the spring 132 can be changed to obtain different trigger characteristics, depending on the properties of the spring.

[0065] Other embodiments of the head 166 are possible. For example, alternatively, the head 166 forms a knob that can be turned directly by hand by a user. In this case, the STH threshold can be adjusted without the need to use a tool such as a screwdriver.

[0066] Alternatively, the head 166 of the screw 162 is not accessible from outside the housing 4. In this case, typically, to access the head 166, the housing 4 must first be opened. Once the adjustment of the STH threshold is complete, the housing 4 is closed, making access to the screw 162 from the outside impossible. In such a variant, the hole 168 is omitted.

[0067] Other embodiments of the stop 116 are possible. For example, as a variant, the stop 116 is also produced in the housing 4 and is not solely formed by the end of the lock 84 which bears on the end 112 of the unlocking lever 100.

[0068] Other circuit breaker variants:

[0069] Lugs 6 and 8 can also each be formed from several blocks of material fixed to each other without any degree of freedom.

[0070] Other embodiments of the short-circuit protection mechanism are possible. For example, the protection mechanism 180 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. The target 162 can 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 admissible for it to permanently generate a magnetic field.

[0071] In a simplified embodiment, the short circuit protection mechanism is omitted.

[0072] The fixed and / or mobile 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.

[0073] Alternatively, there is no thermal compensation. In this case, for example, 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.

[0074] Alternatively, the main bimetallic strip may have other conformations such as, for example, a "W" or inverted double "U" conformation.

[0075] What has been described here applies regardless of the conformation of the lock 84.

[0076] Other embodiments of the bar 50 are possible. For example, as a variant, the bar pivots when pushed by the bimetallic strip 48 instead of sliding.

[0077] Alternatively, the circuit breaker comprises a single fixed contact and a single moving contact which mechanically bears on this fixed contact in its closed position. In this case, the moving contact is permanently connected to one end of the bimetallic strip 48, 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 moving support between its open and closed positions while keeping it permanently electrically connected to the bimetallic strip 48. Thus, in this embodiment, when the circuit breaker is in its undisconnected state, the current to be interrupted passes successively through the bimetallic strip 48, the flexible conductor, the moving contact and then the fixed contact.

[0078] The circuit breaker may also include other sub-assemblies, such as, for example, a sub-assembly that includes an auxiliary contact that allows the circuit breaker status to be displayed.

[0079] Several of the variants described above can be combined in a single embodiment.

[0080] Chapter IV: Advantages of the embodiments described:

[0081] The adjustment mechanism described here makes it possible to adjust the threshold S™ without moving the stationary end 142 of the main bimetallic strip. Therefore, it is no longer necessary for the electrical connection between this stationary end 142 and the lug 8 to be sufficiently flexible to accommodate a movement of this stationary end. Therefore, the cross-section of this connection can be chosen by taking into account only the constraints imposed by the desired value of the threshold STH and without taking into account any additional constraints on the flexibility of this connection. This therefore simplifies the design of this circuit breaker. In addition, since it is no longer necessary for this electrical connection to be flexible, it is possible to fix the stationary end 142, without any degree of freedom, on the lug 8, which is more robust and simpler to achieve.

[0082] The fact that the spring 132 exerts its return force, not directly on the movable end 146 of the bimetallic strip 48, but on a part displaced by the end 146 which is not crossed by the current to be interrupted, simplifies the production of the STH threshold adjustment mechanism because it is not crossed by this current to be interrupted.

[0083] The fact that the part moved by the Joule effect is the unlocking lever 100 makes it possible to exert the restoring force on a part which is not crossed by the current to be interrupted and which already exists in the circuit breaker. This therefore simplifies the construction of the circuit breaker.

[0084] The fact that the same spring 132 is used as the spring of the return mechanism 130 and the adjustment mechanism 38 simplifies the construction of the circuit breaker.

[0085] Fixing the stationary end 142 of the main bimetallic strip directly onto the terminal 8 simplifies the construction of the circuit breaker.

[0086] The fact that the adjustment screw 162 is accessible from outside the housing allows adjustment of the STH threshold after complete assembly of the circuit breaker.

[0087] The use of two fixed contacts 66, 76 and the movable assembly 80 comprising the contacts 92, 94 to interrupt the current makes it possible to avoid the use of a flexible electrical conductor which permanently electrically connects the movable support to the main bimetallic strip. The use of two fixed contacts and two movable contacts also makes it possible, at an equal distance between the fixed 42 and movable 80 supports, to double the length of the air gap that the current must cross to circulate in the air. More precisely, to circulate, the current must first cross a first air gap between the contacts 76, 94 then a second air gap between the contacts 92, 66. Thus, the breaking capacity of the circuit breaker is increased.

[0088] 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 variations in the STH threshold depending on the temperature of the external environment.

[0089] Using a current loop to move a magnetic target allows the circuit breaker to trip more quickly in the event of a short circuit and therefore effectively protects electrical circuits even in the event of a short circuit.

Claims

Claims 1. Thermal circuit breaker capable of automatically switching, when the intensity of the current flowing through it exceeds a thermal tripping threshold, from a non-disconnected state in which it can be crossed by the current to a disconnected state in which it interrupts the flow of the current flowing through it, this circuit breaker comprising: - a first and a second fixed terminal (8, 6), each of these fixed terminals being capable of being connected to an electrical cable or plugged into an electrical connector, - a main bimetallic strip (48) intended to be crossed by the current to be interrupted, this main bimetallic strip comprising: - a stationary end (142) electrically permanently connected to the first terminal and fixed, without any degree of freedom, on this first terminal (8), and - a movable end (146), this bimetallic strip being capable of bending, when the intensity of the current passing through it is greater than the thermal tripping threshold, from an initial state in which its immobile and movable ends each occupy respective initial positions, to a curved state in which its immobile end remains in its initial position and only its movable end reaches an advanced position which triggers the switching of the circuit breaker to its tripped state, and - a mechanism (38) for adjusting the thermal trigger threshold comprising: - a spring (132), mechanically distinct from the main bimetallic strip, which exerts a restoring force which opposes the movement of the movable end (146) of the main bimetallic strip from its initial position to its advanced position, and - an adjustment screw (162) resting on one end of the spring so that the rotation of this screw allows the adjustment of the return force of the spring (132) without modifying the initial position of the stationary end (142) of the main bimetallic strip, - a part (50, 100, 104) moved by the Joule effect, this part not being crossed by the current to be interrupted and mechanically connected to the moving end of the main bimetallic strip to be moved by this moving end as the main bimetallic strip bends towards its curved state, and characterized in that the spring (132) comprises, on the side opposite its end on which the adjustment screw rests, an end resting on this part (100) moved by the Joule effect.

2. Circuit breaker according to claim 1, in which: - the circuit breaker comprises an unlocking lever (100) mounted to pivot around a pivot axis (102) and which is not crossed by the current to be interrupted, this unlocking lever being movable, in rotation around its pivot axis, by the movable end of the main bimetallic strip: - from an upright position in which it maintains the circuit breaker in its un-tripped state, towards - a retracted position in which it releases the movement of the circuit breaker in its tripped state, - the part moved by the Joule effect is this unlocking lever.

3. Circuit breaker according to claim 2, wherein the circuit breaker comprises a mechanical connection (50, 104) capable of transferring the movement of the movable end 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, this bar (50) being capable of sliding in grooves when the main bimetallic strip bends.

4. Circuit breaker according to claim 2 or 3, in which: - the circuit breaker comprises a return mechanism (130) which permanently urges the unlocking lever towards its upright position, this return mechanism comprising a spring for this purpose, and - the spring of the adjustment mechanism (38) and the spring of the return mechanism (130) form only one and the same spring (132).

5. Circuit breaker according to any one of the preceding claims, in which the part moved by the Joule effect is made of electrically insulating material or permanently electrically insulated from the current to be interrupted by an electrically insulating material.

6. Circuit breaker according to any one of the preceding claims, in which the first lug (8) is formed from a single block of material and the stationary end of the main bimetallic strip is directly fixed, without any degree of freedom, on this first lug.

7. A circuit breaker according to any preceding claim, wherein: - the circuit breaker comprises a housing (4) inside which the main bimetallic strip and the spring of the adjustment mechanism are housed, and - the adjustment screw is accessible from outside this housing.

8. A circuit breaker according to any preceding claim, wherein the adjustment mechanism comprises a stop (116) which prevents any modification of the initial position of the movable end (146) of the main bimetallic strip in response to a modification of the restoring force of its spring when the circuit breaker is in its non-tripped state.

9. A circuit breaker according to any preceding claim, wherein the circuit breaker comprises: - a fixed support (42) comprising a first fixed contact (66) electrically permanently connected to the second terminal (6) and a second fixed contact (76) electrically permanently connected to the first fixed terminal (8), this second fixed contact being electrically insulated from the first fixed contact in the disconnected state, - a movable support (80) comprising first and second movable contacts (92, 94) electrically connected permanently to each other, this movable support being movable between a closed position in which the first and second movable contacts bear on, respectively, the first and second fixed contacts to allow a current to pass between the first and second terminals, and an open position in which the first and second movable contacts are spaced from the first and second fixed contacts to interrupt the flow of current between the first and second terminals, and - a spring mechanism (82) permanently urging the movable support towards its open position.

10. A circuit breaker according to any preceding claim, wherein the circuit breaker comprises: - 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.

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