Patent Publication Number: US-11031191-B2

Title: Circuit breaker linking system for movable contact

Description:
The present invention relates to a device for switching an electric current. 
     The invention relates in particular to the field of electrical switching devices intended to interrupt an electric current, such as circuit breakers or switches. 
     Switching devices with separable contacts include a switching mechanism using the accumulation of energy, the function of which is to move the electrical contacts of the device between an open state and a closed state, for example in response to an action by a tripping device or a user. 
     An example of such a mechanism is described in FR-2 985 600-B1. 
     By way of example, a pivoting mobile electrical contact is moved by a switching shaft mechanically coupled to a trip hook by means of a linking system. To close the contacts, an energy accumulator comprising a spring is actuated in order to move the linking system. 
     The switching mechanism is therefore the subject of many mechanical stresses on each opening and closing of the contacts. 
     Such mechanisms have been satisfactory for a long time. However, in some contemporary applications, it is desirable to be able to have switching mechanisms with improved durability, for example in order to increase the number of opening and closing cycles that are admissible over the life of the product. 
     There is therefore a need for a device for switching an electric current in which the switching mechanism has improved reliability. 
     To this end, one aspect of the invention relates to a device for switching an electric current that includes separable fixed and mobile electrical contacts and a mechanism capable of switching the contacts between a closed state and an open state, the mechanism including: 
     a switching shaft that is coupled to a mobile electrical contact; 
     a trip hook that is pivotably mounted on a fixed support of the mechanism; 
     a linking system coupling the switching shaft to the trip hook. 
     The linking system includes a first pair of connecting rods and a second pair of connecting rods, the first connecting rods being pivotably mounted on the trip hook, the second connecting rods being mounted so as to pivot with a crank of the switching shaft, the first connecting rods being connected to the second connecting rods by means of a single axis of articulation which forms a pivot link between the first connecting rods and the second connecting rods. The axis of articulation combines both the function of ensuring the pivot link and maintaining the spacing of the pairs of rods. 
     Thus, the reliability of the switching mechanism is increased, in particular by virtue of better durability of the linking system. In particular, the risk of accidental breakage of the pivot link between the first connecting rods and the second connecting rods is reduced by virtue of the use of the linking axis. 
     According to some advantageous but non-mandatory aspects, such a device can incorporate one or more of the following features, either alone or in any technically permissible combination:
         Each of the ends of the axis of articulation includes a head, each head including an overwidth forming a retaining portion for preventing separation of the first connecting rods and second connecting rods from one another.   The axis of articulation includes a peripheral groove formed at the base of each head.   The depth of the peripheral groove is between 0.2 mm and 0.6 mm and, preferably, equal to 0.4 mm.   The height of each head is less than or equal to 5 mm, preferably between 2 mm and 3 mm.   The greatest width of the head is between 9 mm and 10 mm, preferably between 9.6 mm and 9.8 mm.   The axis of articulation is mounted in a linking system so as to have a radial play of less than or equal to 0.1 mm for the first and second connecting rods.   Each of the first connecting rods is mounted on a first area of the axis of articulation having a first diameter, and each of the second connecting rods is mounted on a second area of the axis of articulation having a second diameter, which is different from the first diameter.   The axis of articulation is made of a steel alloy, for example a steel alloy with chromium and molybdenum.   The axis of articulation is formed by a one-piece part.   Each of the second connecting rods has a shape bent in an arc.       

    
    
     
       The invention will be better understood and other advantages thereof will become more clearly apparent in the light of the following description of one embodiment of an electrical device provided solely by way of example and with reference to the appended drawings, in which: 
         FIG. 1  schematically illustrates a switching device with separable contacts, which is shown in a middle sectional plane, including a switching mechanism according to some embodiments of the invention; 
         FIG. 2  schematically illustrates a linking system forming part of the switching mechanism of  FIG. 1 , in an isometric perspective view; 
         FIG. 3  schematically illustrates the linking system of  FIG. 2  in a side view represented by the arrow Ill: 
         FIG. 4  schematically illustrates an axis of the linking system of  FIG. 2  in a longitudinal sectional view. 
     
    
    
       FIG. 1  shows part of an electrical switching device  2  for interrupting an electric current, such as a circuit breaker or a contactor. The electric current is switched in air and by means of separable electrical contacts. 
     According to some examples, the device  2  is a low-voltage, high-intensity multipole circuit breaker. 
     The device  2  includes a fixed electrical contact  4  and a mobile electrical contact  6  that, in some examples, bears pivotably mounted contact fingers  8  arranged opposite the fixed contact  4 . The contacts  4  and  6  are connected to opposite electrical connecting terminals of the device  2 . 
     The mobile contact  6  is reversibly movable, for example by pivoting with respect to a fixed frame of the device  2 , between an open position and a closed position of the contacts, corresponding to an electrically open state and an electrically closed state, respectively, of the device  2 . The axis of rotation of the mobile contact  6  is denoted by the reference X 6  in the present case. 
     The device  2  also includes a switching mechanism  10  adapted to switch the contacts  4  and  6  between the open and closed states by moving the mobile contact  6  between the open and closed positions. 
     For example, the mechanism  10  is controllable by means of a tripping device  12  of the device  2  and/or by a manual control element, such as a lever or a push button. 
     According to some embodiments, the device  2  is a multipole device adapted to interrupt a polyphase electric current. The device  2  then includes multiple poles, each of which is associated with one electrical phase and includes a pair of contacts  4  and  6 . As a variant, the device  2  is single-pole. 
     According to some implementations, the mechanism  10  is a switching mechanism using mechanical energy accumulation. The operating principle of a switching mechanism using this technology is described in FR-2 985 600-B1, for example. 
     The mechanism  10  in particular includes a switching shaft  20  coupled to the mobile contact  6 , in the present case by means of a pivot link. The shaft  20  is rotatably mobile about its longitudinal axis in relation to a fixed frame, or fixed support, of the device  2 . 
     If the device  2  includes multiple poles, the shaft  20  is common to all of these poles and is mechanically coupled to each mobile contact  6 . 
     The mechanism  10  also comprises a trip hook  40  and a linking system  22  coupling the switching shaft to the trip hook. For example, the linking system  22  is articulated by a pivot link to a crank arm  24  borne by the shaft  20 , as described hereinafter. 
     The mechanism  10  also includes an opening pawl  26  associated with a bolt  28 , also called “half-moon”. 
     The opening pawl  26  is mounted so as to pivot in relation to the frame and cooperates with the trip hook  40 . A spring  29  is engaged between, firstly, the shaft  20  and, secondly, an axis integral with the frame of the device  2 . 
     A closing bolt  30 , also called “half-moon”, and an intermediate lever  31  mechanically cooperate with an actuator controlled by the tripping device  12 , such as an electromagnetic actuator having a coil, and/or with the manual control element. In  FIG. 1 , the association between the tripping device and the lever  31  is schematically depicted by rods, although in practice this mechanical cooperation can be produced in quite a different manner. 
     The bolt  30  is also mechanically associated with a closing pawl  32 , mounted so as to pivot in relation to the frame. 
     The mechanism  10  moreover includes a mechanical energy accumulation device  34 , including at least one spring. For example, the device  34  stores mechanical energy when the spring is compressed and releases this mechanical energy through the relaxation of the spring. 
     A drive mechanism  36 , in the present case including one or more linking parts articulated and/or mounted so as to pivot in relation to the fixed frame, is mechanically coupled to the device  34 . The drive mechanism  36  acts on the linking system  22  in order to strike it and drive it towards a closed position. This way, by moving, the linking system  22  in turn drives the trip hook  40 . 
     In the present case, the trip hook  40  is mounted so as to pivot in relation to the frame and is articulated to the linking system  22  by a pivot link. 
     To make it easier to understand the present description, the other components of the device  2  are neither illustrated nor described in detail. 
     In the embodiments illustrated, the pivot and rotational movements of the elements of the mechanism  10  take place about axes of rotation that are fixed in relation to the frame and that extend parallel to one another, in the present case in directions perpendicular to the plane of the image in  FIG. 1  and parallel to the axis X 6 . 
     Examples of operation of the mechanism  10  will now be described briefly. 
     In a stable open position, illustrated by  FIG. 1 , the device  34  is armed, that is to say that the spring is compressed and stores energy. The bolt  30  keeps the closing pawl  32  in a first position. 
     To close the contacts  4  and  6 , the closing bolt  30  is tilted, for example by the action of the tripping device  12  or of the push button, which releases the closing pawl  32 . 
     The movement of the closing pawl  32  actuates the device  34  and the energy accumulated in the device  34  is released, by a relaxation movement of the spring, and this, by means of the drive mechanism  36 , actuates the linking system  22 , for example by striking it, so as to move the mobile contact  6  by means of the shaft  20 , until the mobile contact  6  comes into contact with the fixed contact  4 . 
     The linking system  22  continues to move towards its closed position until it passes a predefined position of alignment, called “dead centre”, in the forward direction, driving the trip hook  40  and the opening pawl  26  towards a stop position in which the linking system  22  is prevented from returning backwards. 
     The mechanism  10  is then in a stable closed position. 
     To reopen the device  2 , the locking between the opening pawl  26  and the bolt  28  is broken, for example by moving the lever  31  by means of the actuator  12  or by means of a manual action directly on the bolt  28 . The opening pawl  26  pivots, which releases the stop of the trip hook  40 . 
     The linking system  22  is then no longer kept in abutment by the hook  40  and can return to its initial position under the action of the restoring force exerted by the spring  29 . Once the linking system  22  has returned behind the dead centre position, the contact  6  is driven towards its open position. The mechanism  10  is returned to the stable open position. 
       FIG. 2  and  FIG. 3  show examples of the linking system  22  that are compliant with some embodiments of the invention. 
     The linking system  22  includes a first pair of connecting rods  42  and a second pair of connecting rods  44  articulated to one another, on which are formed the pivot links for articulation to the trip hook  40  and the shaft  20 . 
     In the example illustrated, the trip hook  40  also bears an aperture  46  that is used to receive a pivot link to the frame and a stop  48 , which in the present case projects on either side of the trip hook  40 . For example, the trip hook  40  has an essentially flat shape. 
     According to some examples, in the closed position of the mechanism  10 , described above, the stop  48  blocks the first pair of connecting rods  42  so as to block the position of the linking system  22 . During the opening movement, the stop  48  forces the first pair of connecting rods  42  to separate under the action of the spring  29 , so as to return the linking system  22  towards the open position. 
     The first pair  42  of connecting rods includes two similar or identical connecting rods  50  and  52  arranged parallel opposite one another. According to some examples, the connecting rods  50  and  52  have a planar shape. 
     A first end, in the present case a lower end, of each of the connecting rods  50  and  52  is pivotably mounted on the trip hook  40 , and more specifically on a distal end  54  of the trip hook  40 . 
     This pivot link, in the present case, is formed by means of a rigid axis  56 , such as a journal, which extends perpendicularly to the connecting rods  50  and  52 . The reference X 56  denotes the axis of rotation associated with this pivot link. The axis X 56  is parallel to the axis X 6  in the present case. 
     According to some examples, the linking system  22  can also include a ring  58  mounted between the connecting rods  50  and  52  on a spacer  59  that secures the connecting rods  50  and  52  to one another. The spacer  59  extends parallel to the axis X 56  in the present case. 
     For example, the spacer  59  and the ring  58  are struck by the drive mechanism  36  when the energy is released by the device  34 . 
     In the example of the mechanism  10  that is described above, the dead centre position of the linking system  22  corresponds to the position of alignment of the pairs of connecting rods  42  and  44  among one another along one and the same straight line, the pairs of connecting rods  42  being bent by comparison with the pairs of connecting rods  44  in the other positions. 
     The second pair  44  of connecting rods includes two similar or identical connecting rods  60  and  62  arranged parallel opposite one another. According to some examples, the connecting rods  60  and  62  have a planar shape. 
     According to some optional but nevertheless advantageous embodiments, each of the second connecting rods  60  and  62  has a shape bent in an arc, which improves the distribution of the mechanical stresses and increases the mechanical endurance of the system  22 . 
     A first end, in the present case an upper end, of the connecting rods  60  and  62  is adapted to be pivotably mounted on the shaft  20 , and more specifically on an arm of the crank  24 , in the present case in an aperture formed in this arm of the crank  24 . 
     This pivot link is formed by means of a rigid axis  64 , which extends perpendicularly to the connecting rods  60  and  62 , preferably by projecting in relation to the outer lateral faces of the connecting rods  60  and  62 . The reference X 64  denotes the axis of rotation associated with this pivot link. The axis X 64  is parallel to the axis X 56  in the present case. The rigid axis  64  is placed on said first end of the connecting rods  60  and  62 . 
     According to some examples, the rigid axis  64  is permanently secured to the connecting rods  60  and  62 . In other words, the rigid axis  64  remains motionless in relation to the connecting rods  60  and  62 . 
     The connecting rods  60  and  62  forming the second pair of connecting rods  44  are kept at a distance from one another in the direction X 64  so as to allow one end  66  of the trip hook  40  to pass between the connecting rods  60  and  62 . 
     This end  66  forms a projecting hooking portion that cooperates with the opening pawl  26 , for example by abutting against the opening pawl  26  in the closed position. 
     The connecting rods  50  and  52  are connected to the connecting rods  60  and  62  by means of a single axis of articulation  68  that forms a pivot link between the connecting rods  50  and  52  of the first pair  42  and the connecting rods  60  and  62  of the second pair  44 . The reference X 68  denotes a straight line providing the axis of rotation associated with this pivot link. 
     The axis of articulation  68  extends along this axis X 68 , which is called “direction X 68 ” below to avoid any confusion with the axis of articulation  68 . 
     According to some examples, the connecting rods  60  and  62  are arranged on either side of the connecting rods  50  and  52  and are in contact with the contacting rods  50  and  52  over a portion of their length. The connecting rod  50  is adjacent to the connecting rod  60  and the connecting rod  52  is adjacent to the connecting rod  62 . 
     The pivot link formed by the axis of articulation  68  is formed on the other end of each of the connecting rods  50 ,  52 ,  60  and  62 , that is to say formed on the second end of the connecting rods  50  and  52  and on the second end of the connecting rods  60  and  62 . In practice, the second end of each connecting rod is situated opposite the first end of said connecting rod. 
     As illustrated by the figures, the connecting rods  60  and  62  are, at their second end, interconnected only by the axis  68 . In other words, to maintain a constant spacing between the pairs of rods  40  and  42 , it is not necessary to add a fixed axis connecting the second ends of the connecting rods  60  and  62 . 
     Thus, in the examples illustrated, the pivot link formed by the axis of articulation  68  is situated on the lower end of the connecting rods  60  and  62  and on the upper end of the connecting rods  50  and  52 . In these examples, the articulation is therefore formed essentially in the middle of the linking system  22 . 
     As illustrated in  FIG. 4 , the axis of articulation  68  includes a body of elongate, preferably cylindrical, shape. The axis of articulation  68  in the present case has a rotational symmetry around the direction X 68 . Other shapes are possible, however. 
     In practice, the corresponding ends of the connecting rods  50 ,  52 ,  60  and  62  comprise a through-aperture allowing the passage of the body of the axis of articulation  68 . 
     Preferably, each of the ends of the axis of articulation  68  includes a head  70  and  72  formed in one piece with the body of the axis of articulation  68 . 
     In the example illustrated, the head  70  juts out from the side of the outer face of the connecting rod  60  and the head  72  juts out from the side of the outer face of the connecting rod  62 . 
     Preferably but nonetheless optionally, the height of each head  70  and  72 , denoted by “h”, measured perpendicularly to the face of the connecting rod  60  or  62  from which the head juts out, is less than or equal to 5 mm, preferably between 2 mm and 3 mm. 
     Each head  70  and  72  includes an overwidth forming a retaining portion in order to prevent separation of the connecting rods  50  and  52  of the first pair  42  and the connecting rods  60  and  62  of the second pair from one another, that is to say separation in the direction X 68 . 
     In other words, each head  70 ,  72  is wider than the body of the axis of articulation  68 . 
     For example, if the axis of articulation  68  is cylindrical, the diameter of each head  70 ,  72  is greater than the diameter of the body of the axis of articulation  68 , for example at least 1.1 times greater than the diameter of the body of the axis of articulation  68 . 
     The axis of articulation  68  allows a constant separation to be kept between the connecting rods  50  and  52  and also between the connecting rods  60  and  62  even while the linking system  22  is moving. 
     As an illustrative example, the resistance to the lateral wrenching of a connecting rod in the direction X 68  in relation to the other connecting rods at the axis of articulation  68 , expressed by the minimum force necessary for such wrenching, is greater than or equal to 800 daN. 
     According to some examples, the greatest width of the head  70 ,  72 , in the present case measured perpendicularly to the direction X 68 , is between 9 mm and 10 mm, preferably between 9.6 mm and 9.8 mm. 
     For example, the radius R 1  is between 4.5 mm and 5 mm and the radius R 2  is between 3 mm and 5 mm. 
     For example, each head  70  and  72  has a conical shape, the base of which, in contact with the body of the axis of articulation  68 , has a radius R 2  strictly less than the radius R 1  measured at the top of the head  70 ,  72 . 
     Other shapes are nevertheless possible, for example a cylindrical shape of constant diameter, which is nevertheless greater than the diameter of the body of the axis  68 , however. 
     Preferably, the heads  70  and  72  are identical. 
     According to some examples, each of the connecting rods  50  and  52  is mounted on a first area of the axis of articulation  68  having a first diameter D 1  and each of the connecting rods  60  and  62  is mounted on a second area of the axis of articulation  68  having a second diameter D 2 , which is different from the first diameter D 1 . For example, the diameter D 1  is greater than the diameter D 2 . Thus, the body of the axis of articulation  68  in the present case includes at least two areas of diameter D 1  and at least two areas of diameter D 2 . For example, the diameter D 1  is equal to 9.5 mm and the diameter D 2  is equal to 9 mm. 
     These areas of different dimensions form receiving areas of the connecting rods that prevent the connecting rods from sliding along the axis of articulation  68  in the course of the movement of the linking system  22 . For example, the widening of the diameter between the second area and the first area prevents the connecting rods  60  and  62  from sliding towards the centre of the axis of articulation  68 . This assists the stability of the linking system  22  and increases the resistance to wrenching. 
     The axis of articulation  68  can preferably turn freely around the direction X 68  in relation to the connecting rods  50 ,  52 ,  60  and  62 . 
     For example, the axis of articulation  68  is mounted in the linking system  22  so as to have a radial play of less than or equal to 0.1 mm and greater than 0 mm with the connecting rods  50 ,  52 ,  60  and  62 . 
     The radial play is measured perpendicularly to the direction X 68  in the present case. 
     In particular, the radial play is chosen in each of the receiving areas on the basis of the diameter of the through-aperture of the corresponding connecting rod  50 ,  52 ,  60  and  62 . For example, the connecting rods of one and the same pair of connecting rods  42 ,  44  have such a through-aperture having one and the same diameter. 
     In many embodiments, the axis of articulation  68  is formed by a one-piece part. 
     According to some examples, the axis of articulation  68  is made of metal. Preferably, the axis of articulation  68  is made of a steel alloy, and more preferably of a steel alloy with chromium and molybdenum. Preferably, this steel alloy has previously undergone heat treatment in the mass to obtain a hardness of between 340 and 400 on the Vickers scale HV30. 
     Thus, the mechanical behaviour of the axis of articulation  68  is improved, which increases the endurance of the linking system  22  and reduces the risk of premature breakage, while providing the axis of articulation  68  with sufficient rigidity so as not to bring about unexpected deformations among the pairs of connecting rods  42 ,  44 . 
     Optionally but nevertheless advantageously, the axis of articulation  68  includes a peripheral groove  74  formed at the base of each head  70  and  72 , preferably arranged concentrically with the direction X 68  and formed level with the face of the connecting rod  60 ,  62  from which the head  70  or  72  juts out. 
     The groove  74  makes it easier to obtain axial play in the direction X 68  between the axis of articulation  68  and the connecting rods  50 ,  52 ,  60  and  62  with a desired value. 
     For example, the depth of the groove  74 , measured perpendicularly to the direction X 68 , is between 0.2 mm and 0.6 mm and, preferably, equal to 0.4 mm. 
     Owing to the embodiments of the invention, the reliability of the switching mechanism  10  is increased, in particular owing to better durability of the linking system  22 . In particular, owing to the use of the axis of articulation  68 , the risk of accidental breakage of the pivot link between the connecting rods  50 ,  52 ,  60  and  62  is reduced, while permitting a pivot movement by the pair of connecting rods  42  in relation to the pair of connecting rods  44  that is necessary for the operation of the mechanism  10 . 
     In particular, the axis of articulation  68  combines at once the function of providing the pivot link and the keeping of the separation between the pairs of connecting rods  42 ,  44 . 
     On the other hand, the use of the axis of articulation  68  allows the linking system  22  to have a shape that makes it compatible with existing switching mechanisms, enabling it to be used in many ranges of electrical switching devices without needing to completely modify the architecture of the switching mechanisms of these devices. 
     The better mechanical behaviour thus allows a higher level of endurance to be obtained for the mechanism  10 . The device  2  is therefore capable of withstanding a greater number of mechanical opening and closing cycles over its life. 
     The device  2  can thus advantageously be used in critical applications requiring a high level of reliability, in which it is likely to be called upon frequently, for example data centres or renewable energy production systems. 
     The embodiments and variants envisaged above can be combined to produce new embodiments.