Patent Publication Number: US-7709758-B2

Title: Circuit breaker with interchangeable operating mechanism and suspended mobile contact assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application (under 35 U.S.C. §371) of PCT/EP2006/062004 filed May 3, 2006, which claims benefit of Italian application BG2005A000025 filed May 13, 2005, disclosure of which are incorporated herein by reference. 
     The present invention relates to a low-voltage switch with improved characteristics of interchangeability of the control, of maintenance and modification of performances and of operating configurations. 
     The term switch is intended as a switching device provided with protective means which cause automatic breaking in the presence of specific conditions of overload, short circuit or other electrical faults. 
     It is known that automatic switches and other switching devices include one or more electrical poles, associated with each of which is at least one fixed contact and at least one mobile contact which can be reciprocally coupled to/uncoupled from each other. Throughout the description the expression switch will be used to indicate without distinction an automatic switch or other types of switching devices. 
     Switches also comprise control means which allow movement of the mobile contacts, causing coupling and uncoupling of the corresponding fixed contacts. 
     The action of these control means on the mobile contacts generally takes place through a main shaft operatively connected to the mobile contacts or through the use of a mobile element from which said mobile contacts directly extend. The operative connection between said control and said main shaft or said mobile element takes place conventionally by means of a kinematic chain. 
     However, switches of known type have various drawbacks. Some of these derive from the fact that, normally, the operative connection between the control and the mobile element or main shaft requires a relatively high number of connecting means which are difficult to access and therefore difficult for an operator to replace when required. In fact, as is known, during the operating life of the switch, each of its components is virtually subject to deterioration or wear due, for example, to the considerable thermal and mechanical stresses to which the automatic switch or disconnector is normally subjected, during switching movements or tripping due to short circuit. However, the operating efficiency of the switch depends on the perfect state of preservation of all its parts. Therefore, on the basis of the state of effective efficiency, it may be necessary to carry out difficult and costly maintenance operations. 
     In particular, it is currently possible to replace or disassemble parts of the switch control only through specific working procedures which are outside the normal field of an operator in charge of maintenance. 
     As is known, the performances of the switch are closely related to the performances of each component, and in particular of the control, which on the basis of the power that can be stored in its storage members, allows, for example, improved dynamic response values which translate into higher values of making capacity and/or breaking capacity. In the case in which different plant engineering requirements become necessary, such as the necessity to benefit from the advantages of a storage control (i.e. from a servomotor remote control) and of a higher making or breaking capacity, in almost all current solutions it is necessary to replace the entire apparatus. Obviously, this limit has negative repercussions on the overall manufacturing and operating costs of the low-voltage switch. 
     Another drawback of conventional switches is represented by their functional rigidity, i.e. the fact that they can only be used correctly in limited ranges of application, with particular reference to the type of operating configuration of the control (direct or storage), the making capacity and the breaking capacity. In particular, for each application the switch must be fitted with a specific control which responds efficiently to the operating conditions. When these conditions vary, currently it is not possible to replace the control alone in order for the switch to be operative, but is almost always necessary to replace the entire switch. In substance, current technical solutions do not allow interchangeability of the control by an operator in charge of maintenance, as the work procedures require the use of industrial type equipment and specific knowledge of the complex connection, fastening and regulation operations. 
     On the basis of these considerations, the main task of the present invention is to provide a switch, which allows the drawbacks described to be overcome. 
     Within this task, an object of the present invention is to provide a switch, with improved characteristics of interchangeability of the control. 
     Another object of the present invention is to provide a switch in which the operative connection between the control and the main shaft of the mobile contacts or mobile element can be produced in a simple and reliable manner, without complex connection, fastening and regulation operations. 
     A further object of the present invention is to provide a switch that has a reduced number of parts which are relatively simple to assemble and install. 
     Yet another object of the present invention is to provide a switch whose constituent parts are easy to inspect without complex maintenance procedures. 
     A still further object of the present invention is to provide a switch which is simple to produce, with moderate costs. 
     This task, these and other objects which will be more apparent hereunder are obtained by a low-voltage switch comprising:
         an outer casing containing for each pole at least one fixed contact and at least one mobile contact which can be reciprocally coupled to/uncoupled from each other,   a mobile element defined by a shaped body comprising at least one seat for each pole of the switch, said seat being suitable to house the mobile contact of the relative pole;       

     The switch according to the invention is characterized by the fact that it comprises:
         first removable connection means which connect a control mechanism to the mobile element, said control mechanism comprising mechanical means supported by a structural part;   second removable connection means which connect the structural part of the control mechanism to the outer casing;   means to support the mobile element connected to the structural part of the control mechanism through third removable connection means, said supporting means being connected to the mobile element through a hinge connection.       

     The first, second and third removable connection means allow connection of the operating parts of the switch improving the characteristics of interchangeability of the control. These connection means can be positioned in or removed from their operating position without particular operations on the other constituent parts of the switch, with obvious advantages from a practical point of view. 
    
    
     
       Further characteristics and advantages will be more apparent from the description of a non-exclusive preferred embodiment of the switch according to the present invention, illustrated by way of a non-limiting example in the accompanying drawings, in which: 
         FIG. 1  schematically shows the structure of a switch according to the present invention; 
         FIGS. 2 and 3  show perspective views respectively of a first and of a second possible embodiment of a control mechanism of a switch according to the invention; 
         FIGS. 4 and 5  show first perspective views of component parts of an outer casing of a switch according to the invention; 
         FIGS. 6 and 7  show second perspective views of the parts of an outer casing of a switch indicated in  FIGS. 4 and 5 ; 
         FIGS. 8 and 9  show perspective views of a possible embodiment of a mobile element of a switch according to the invention; 
         FIG. 10  shows a sectional view of a possible connection of a mobile element to the supporting means of a switch according to the invention; 
         FIG. 11  shows a sectional view of a possible embodiment of said first removable connection means of a switch according to the invention; 
         FIGS. 12 and 13  show respectively a first and a second exploded view of a first embodiment of a switch according to the invention; 
         FIG. 14  shows a perspective view of the switch indicated in  FIGS. 12 and 13 ; 
         FIGS. 15 and 16  show respectively a first and a second exploded view of a second embodiment of the switch according to the invention; 
         FIG. 17  shows a perspective view of the switch indicated in  FIGS. 15 and 16 . 
     
    
    
     With reference to the aforesaid figures, the switch  1  according to the invention comprises an outer casing  2  containing one or more electrical poles, each defined by at least one fixed contact  10  which couples to/uncouples from at least one mobile contact  20 . The outer casing  2  also houses a mobile element  50  composed of a shaped body made of insulating material, preferably thermosetting resin, which comprises at least one seat  25  for each pole of the switch  1 . 
     The switch  1  is characterized in that it comprises first removable means  64  which connect a control mechanism  60  or  61  to the mobile element  50  in order to allow movement. The control mechanism  60  or  61  essentially comprises mechanical means supported by a structural part  70 . This is connected to the outer casing  2  of the switch  1  through second removable connection means  65 . 
     The switch  1  also comprises means to support the mobile element  50  which simultaneously provide a physical center for rotation of said element, utilizing a hinge connection illustrated hereunder in a possible embodiment thereof. The supporting means are connected to the control mechanism  60  or  61  and in particular to the structural part  70  thereof through third connection means  66 , advantageously also removable. 
       FIG. 1  schematically shows a switch  1  according to the invention. As is evident, replacement of a first control mechanism  60  with a second of a different type  61  does not require disassembly of the entire switch  1 , but the operation in question is performed simply by utilizing the first,  64 , second  65  and third  66  removable connection means. The technical solutions employed and illustrated hereunder allow easy access to all the removable connection means, permitting operators to replace the control easily through simple and rapid operations. 
       FIGS. 2 and 3  show two possible configurations of the control mechanism which will be used as references during the description. In particular,  FIG. 2  relates to a control of the power storage type  60  normally used in applications which require, for example, high values of rated current, making capacity and/or the possibility of benefiting from servomotor remote controls. The structural part  70  of the mechanism  60  comprises a first side  71  and a second side  72  between which a transverse wall  74  is preferably interposed. At the side of this wall a loading lever  35  is positioned with the function of actuating a device  36  to load the springs of the kinematic means. In the solution shown, the first side  71  also comprises a side opening  77  positioned to allow passage of a signaling member  79  of the state of the switch  1 . 
       FIG. 3  instead shows a control mechanism of the direct type  61  which is normally used for less complex plant engineering solutions. In this case, a control lever  76  is interposed between the two sides  71  and  72  of the structural part  70  for making, breaking or resetting the switch  1  by an operator. As will be illustrated hereunder, although having a different structural configuration from the power storage control  60 , the direct control mechanism  61  is still connected to the other operating parts of the switch  1  according to the same assembly methods with obvious advantages. 
       FIGS. 4 ,  5 ,  6  and  7  are perspective views showing a possible embodiment of the outer casing  2  of the switch  1  according to the invention. This is preferably composed of a bottom  3  which couples to a lid  4  to produce volumes inside which the actual electrical components of the switch  1  are housed. The structure of the casing  2  can advantageously be completed through a protective mask  5  which is applied to the lid  4  and which can be easily removed by an operator to gain access to the internal parts of the switch  1 . 
     The bottom  3  comprises a first coupling surface  6   a  emerging from which are a series of protrusions  5   a , designed to be inserted in cavities  7   b  provided on a second coupling surface  6   b  of the lid  4 . Similarly, also emerging from this second surface  6   b  are further protrusions  5   b , which can be inserted in relative cavities provided on the first coupling surface  6   a . In substance, the two coupling surfaces  6   a  and  6   b  have a shape at least partly geometrically corresponding which allows mutual penetration of the parts forming the casing  2 . 
     With reference to  FIG. 6 , constraint of the coupling is also guaranteed by a series of fastening screws  9  which ensure adequate resistance of the casing  2  to the stresses to which it is subjected during normal operation of the switch  1 . As shown, the fastening screws  9  are inserted in holes  13  produced both on the bottom  3  and on the lid  4  and, alternatively, can be replaced by other functionally equivalent means, such as bolts or tie-rods. 
     Alternatively, the outer casing can be produced in metal sheet, as is commonly the case in switches of the “break” or “ACB” (air circuit breaker) type. 
       FIGS. 12 and 15 , which will be described in detail hereunder, show the internal side of the bottom  3 , on which the fixed contacts  10 , each electrically connected to an electrode  21 , are provided. The fixed contacts  10  shown each comprise an active part  10   a  which comes into contact with a relative active part  20   a  provided on the mobile contacts  20 . Both the fixed contacts  10  and the mobile contacts  20  can advantageously comprise an arc chute  11  which has the task of deflecting the electric arc in order to limit deterioration of the active parts of the contacts. 
     As known in the art, if metal casings are used, insulating elements are interposed between the fixed contacts and the casing. 
     With reference once again to  FIG. 7 , the lid  4  can advantageously be produced in an insulating material to improve electrical insulation between the metal parts forming the switch. When coupled to the bottom  3 , the lid  4  produces at least one arc chamber  200  for each pole of the switch. Preferably, arc breaking elements are housed inside each arc chamber  200 , with the function of facilitating quenching of the arc generated after separation of the contacts of the switch  1 . Each arc chamber  200  comprises at least one upper opening  203  which forms the path for discharge of gases generated subsequent to creation of the electric arc. The lid  4  also has side openings  204  which allow an operator to gain access to the inside of the mobile element  50  and/or allow the passage of shafts or bars signaling the state (i.e. open, closed, tripped). 
       FIGS. 8 and 9  show a possible embodiment of a mobile element  50  according to the invention, and more specifically of an element for a three-pole switch. This does not prevent the technical solutions presented hereunder from also being used for switches with a different number of poles. The mobile element  50  is defined by a shaped body, preferably produced in one piece, which comprises a seat  25  for each pole of the switch  1 . Housed in each seat  25  is a mobile contact  20  which can be produced in one piece or in a plurality of components adjacent to one another, as clearly shown in  FIG. 7 . These seats  25  are produced to be mutually adjacent and in particular positioned so that the mobile contacts  20  housed therein have a common axis of rotation  100 . This axis is physically formed of transverse rotation pins (not visible in the figures) which are arranged in suitable housings  23  produced on each of the seats  25 . 
     In a preferred embodiment, the seats  25  are defined essentially by a front wall  26 , a rear wall  27 , substantially opposite the front wall  26 , by a first side wall  28  and a second side wall  29 , substantially opposite each other. These walls are mutually positioned to produce at least a first and a second opening, through which the relative mobile contact  20  and electrical connection means  47  project (see  FIG. 9 ). The latter, formed for example of a copper braid, electrically connect the mobile contact  20  to an electrode  22 , in turn connected to the electrical network in which the switch  1  is installed. If the switch  1  operates according to the known double break principle, other electric contacts suitable to couple with a further series of fixed contacts identical to the ones indicated above can advantageously project from the second opening. 
     The mobile element  50  comprises circular connecting parts  55   a  and  55   b  positioned between two adjacent seats  25 . In the solution shown in  FIGS. 8 and 9 , these circular connecting parts  55  emerge for a portion thereof with respect to the spatial volume occupied by the seats  25 . This solution must obviously be considered solely as a possible and not entirely exclusive embodiment of the mobile element  50 . 
     Each of these connecting parts  55  comprises at least one radial recess the function of which will be illustrated hereunder. More specifically, the mobile element  50  shown in  FIGS. 6 and 7  comprises a first connecting part  55   a  and a second connecting part  55   b,  respectively comprising a first radial recess  51  and a second radial recess  52 . 
     In a preferred embodiment thereof once again illustrated in  FIG. 7 , the supporting means are formed of at least a first supporting arm  80  and of a second supporting arm  81  having at least two ends placed opposite each other. In particular, each of them comprises at least a first operating end  85  which connects to the mobile element  50  and a second retention end  86  which couples to the structural part  70  of the control mechanism  60  and  61 . According to a preferred embodiment, the two supporting arms  80  and  81  have a three lobed configuration comprising a third retention end  86   a  adjacent to said second end  86 . 
     As mentioned above, the supporting means have a dual function of supporting the mobile element  50  with respect to the outer casing  2 , and simultaneously providing a center of rotation for said element. The latter function is produced through a hinged connection which permits rotation of the mobile element  50  with respect to the supporting arms  80  and  81  and more generally with respect to the fixed parts of the switch  1 . 
       FIGS. 8 and 10  show a possible embodiment of this hinged connection. Advantageously, it is implemented inside said radial recesses  51  and  52  provided in the connecting parts  55   a  and  55   b  of the mobile element  50 . 
     With reference in particular to  FIG. 6 , the hinged connection comprises for each supporting arm  80  and  81  a rotation pin  110  and  111  which is inserted in a first hole  84  produced on the first operating end  85  and in a second hole provided on the mobile element  50 . The rotation pins  110  and  111  preferably have at least a first calibrated longitudinal portion  112  which couples to the inner surface of the first hole  84  produced on the relative supporting arm  80  or  81 . Each pin advantageously also comprises a second retention portion  113  which is coupled by friction or by screwing in the second hole of the mobile element  50 . In practice, the retention portion  113  allows the rotation pin to be positioned in relation to the mobile element  50 , while the calibrated portion allows rotation of the element with respect to the supporting arms  80  and  81  that support it. From the point of view of assembly, the solution described is extremely advantageous as each rotation pin has limited axial dimensions which facilitate positioning inside the element  50  at the radial recesses  51  and  52 .  FIG. 11  shows a sectional view of the connection in question and allows the advantages of this solution to be observed. The rotation pins are placed in their operating positions making use of gaps  114  produced on the side walls of the housing seats  25 . The limited axial dimension of the rotation pins  110  and  111  advantageously also improves the mechanical reliability of the connection without detriment to the electrical insulation properties. 
     With reference again to  FIG. 10 , the operating ends of the supporting arms  80  and  81  and the radial recesses  51  and  52  of the element  50  are coupled in an extremely accurate way in order to limit clearances. Moreover, the surfaces of the arms  80  and  81  and the inner surfaces of the radial recesses  51  and  52  are compatible with each other to limit phenomena of friction. This contact area in practice acts as a bearing, as it supports the mobile element  50  while allowing rotation also for operating configurations in which the mobile element  50  is installed according to non-horizontal planes. 
     In  FIGS. 1 ,  8  and  11  a possible embodiment of first connection means  64  according to the invention can be observed. In particular, they comprise a first connecting rod  91  and a second connecting rod  92  which are operatively connected to the mobile element  50  and to the control mechanism  60  or  61  through a transverse driving pin  131 . As shown, the connecting rods  91  and  92  are inserted in hollow sectors  57  produced on the front walls of the seats  25  of the mobile element  50  and perforated crosswise to house the transverse driving pin  131 . With reference to  FIG. 10 , the mobile element  50  is perforated crosswise for the entire length thereof to define a through tunnel  54  in which the transverse driving pin  131  is made to slide to reach its operating position. As mentioned above, the outer casing  2  advantageously also comprises side openings  204  which advantageously allow removal or positioning of the transverse driving pin  131 . According to a preferred embodiment of the invention, during normal operation of the switch  1 , the transverse driving pin  131  is constrained in its correct operating position by the supporting arms  80  and  81  which each have a protruding tooth  88  that stops the pin  131  longitudinally in proximity of the ends thereof, as indicated in  FIG. 11 . In this embodiment, removal and positioning of the pin  131  will thus be performed by varying the mutual position of the element  50  with respect to the arms  80  and  81  so that each protruding tooth  88  does not block movement of the pin, permitting it to slide along the through tunnel  54 . 
       FIG. 12  is a first exploded view of a first embodiment of the switch  1  according to the invention, comprising a power storage control mechanism  60 . In particular, in this figure a possible embodiment of said second ( 65 ) and said third removable connection means  66  (indicated in  FIG. 1 ) can be observed. 
     The second connection means  65  preferably comprise a plurality of axial tie rods  62  which connect the storage control mechanism  60  to the bottom  3  of the outer casing  2 . The tie rods  62  are inserted in through holes  33  produced on the bottom  3  and subsequently screwed to the inside of threaded cavities  34 , provided on suitable fastening protrusions  78  (see also  FIGS. 2 and 3 ) of the structural part  70  of the control mechanism  60 . The axial tie rods  62  can naturally be replaced by other functionally equivalent means and are easily removable when required to allow replacement of the control mechanism. 
     As indicated above, the third connection means  66  are instead provided for the purpose of connecting the supporting means to the structural part  70  of the control mechanism  60  in a removable way. In the solution shown in  FIG. 12 , the supporting arms  80  and  81  are preferably connected to the control mechanism  60  on the outer side of each side  71  and  72  using removable screws  73  or other functionally equivalent elements. 
     From the description hereinbefore, the versatility of the switch  1  according to the invention, on which control mechanisms with different characteristics, operating configurations, making and breaking capacities can be mounted, can be clearly understood. 
       FIG. 13  is a second exploded view of the switch indicated in  FIG. 12  in which the methods for the assembly thereof can be observed. In an initial step, the supporting arms  80  and  81  are mounted in the radial recesses  51  and  52 , followed by positioning of the mobile contacts  20  in the seats  25  and connection of the two supporting arms  80  and  81  in the radial recesses  51  and  52 . In this step the mobile contacts  20  are preferably already connected to the relative electrodes  22  through the specified electrical connection means  21 . Subsequently, the mobile element  50  is placed inside the outer casing  2 , produced by coupling the bottom  3  and the lid  4  to then be connected to the control mechanism  60 . In particular, the connecting rods  91  and  92  are fastened to the element  50  at the level of the hollow sectors  57  thereof and with the use of the transverse driving pin  131 . The supporting arms  80  and  81  are then fastened to the sides  71  and  72  of the structure  70  of the control  60  using the removable fastening means  73  at the retention ends  86  and  86   a  provided on said arms. The control  60  is then placed in the correct operating position using the axial tie rods  62  which connect it stably to the bottom  3 . The sides  71  and  72  of the control  60  are shaped to correspond with the rear wall of the lid which in practice acts as a spacer between said control and the bottom  3 . The presence of the lid  4  made of insulating material also contributes towards improving insulation of the control with respect to the electrical parts. 
     If the casing is made of sheet metal, as for example in the typical construction of an ACB, the sides of the control structure can be shaped to correspond directly with the bottom of said casing. 
       FIG. 14  shows the switch  1  at the end of the main assembly steps described above. In particular, one of the side openings  204  produced on the side  31  of the lid  4  which allows access to be gained to the inside of the lid, to permit positioning or removal of the transverse driving pin  131  connecting the control  60  to the mobile element  50 , can be observed. With this illustration, it is possible to observe how all the connection means described are easily accessible to operators without requiring disassembly of the casing. The switch  1  is therefore suitable to be easily preset for applications of different types, thanks to the noteworthy characteristics of interchangeability of the control that distinguish it. 
       FIGS. 15 and 16  are respectively a first and a second exploded view of a second embodiment of a switch  1  according to the invention comprising a control of the direct type  61 . In  FIG. 15  it is possible to observe how the first, second and third connection means used in the previous case can also be utilized to position the control mechanism of the direct type. Similarly,  FIG. 16  shows how the assembly steps of the switch for the two different types of control are exactly the same. 
     In substance, therefore, a control mechanism of direct type  61  can easily be replaced with one of the power storage type  60 , or vice versa, using simple operations and in particular by separating the supporting arms  80  and  81  from the sides  70  and  71  of the control mechanism  60 , removing the transverse driving pin  131  and uncoupling the control mechanism  60  from the bottom  3  of the casing  2  by removing the tie rods  62 . 
     With reference to the first connection means  64 , it must be observed that the interchangeability of the control is also guaranteed by the presence of a plurality of hollow sectors  57  which is particularly advantageous as it allows positioning of the connecting rods  91  and  92  at variable distances according to the type of control used. Alternatively to the hollow sectors  57 , perforated radial protrusions for insertion of the transverse driving pin  131  could be provided. 
     However, said transverse driving pin  131  must be arranged in an eccentric position with respect to the axis of rotation of the mobile element  50  provided by the hinge connection. In this way, subsequent to a movement of the transverse driving pin  131  a torque is generated that makes the element  50 , and consequently the mobile contacts  20 , rotate. 
     The technical solutions adopted for the switch according to the invention thereby allow the tasks and objects set to be completely fulfilled. The switch has an easy to assemble compact inner structure composed of a limited number of components. The use of supporting means makes it possible to limit the friction areas, improving the mechanical efficiency of the switch. The use of removable connection means between operating parts of the switch allows easy interchangeability of the control, permitting the switch to be used in different applications. 
     The switch thus conceived is susceptible of numerous modifications and variants, all coming within the scope of the inventive concept; moreover, all details can be formed of other technically equivalent details. In practice, the materials used and the dimensions and contingent shapes can be any, according to requirements and to the state of the art.