Patent Publication Number: US-2023132857-A1

Title: Switching Contact Assembly for an Electrical Switching Element and Electrical Switching Element

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of German Patent Application No. 102021128179.2, filed on Oct. 28, 2021. 
     FIELD OF THE INVENTION 
     The invention relates to a switching contact assembly for an electrical switching element, such as a contactor or a relay, and an electrical switching element. 
     BACKGROUND 
     In switching contact assemblies and electrical switching elements, an overtravel spring is generally used to ensure reliable contacting of a contact bridge with mating contacts. 
     In an attempt to downsize electrical switching elements, it is necessary to make the switching contact assemblies smaller as well. However, downsizing the overtravel spring is a problem. With smaller overtravel springs, it is difficult or impossible to precisely adjust the spring force with which the contact bridge is pressed against mating contacts, because existing overtravel springs have relatively high tolerances for the spring force that can be generated per spring length. 
     SUMMARY 
     A switching contact assembly for an electrical switching element includes a contact bridge, a base, and a spring assembly. The contact bridge is attached to the base with the spring assembly between the contact bridge and the base. The contact bridge attached to the base is resilient in a direction opposite a switching direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying Figures, of which: 
         FIG.  1    is a perspective view of an electrical switching element; 
         FIG.  2    is a perspective view of a switching contact assembly according to an embodiment; 
         FIG.  3    is an exploded perspective view of the switching contact assembly of  FIG.  2   ; 
         FIG.  4    is a sectional perspective view of the switching contact assembly of  FIG.  2   ; and 
         FIG.  5    is a sectional perspective view of the switching contact assembly of  FIG.  2   . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The invention shall be further explained hereafter on the basis of an embodiment with reference to the figures. Individual features that are advantageous by themselves can be added or omitted in the embodiment described. 
       FIG.  1    shows an electrical switching element  1  in a schematic representation. The electrical switching element  1  can be a relay la or a contactor lb. The electrical switching element  1  comprises power contacts  3  and drive contacts  5 , wherein it is possible for power contacts  3  to be switched by way of drive contacts  5 . 
     The representation shown is purely by way of example and other configurations of electrical switching element  1  can have a different number of power contacts  3  and drive contacts  5  and/or different positioning of the power contacts  3  and drive contacts  5 . The power contacts  3  can be configured as fixed contacts  3  permanently installed in switching element  1  and immovable. The drive contacts  5  can be configured as a plurality of coil terminals  5  which can be connected to a drive, e.g. a coil of switching element  1 . 
     A switching contact assembly  7  for switching the power contacts  3 , which is shown in  FIG.  2   , is disposed in electrical switching element  1 . In addition to the switching contact assembly  7 , the electrical switching element  1  has a drive. 
     As shown in  FIG.  2   , the switching contact assembly  7  comprises a contact bridge  9 , a base  11 , and a spring assembly  13 . Contact bridge  9  comprises mating power contacts  3   a  which, when switching contact assembly  7  is actuated, i.e. when moving along a switching direction  19 , switch power contacts  3  (see  FIG.  1   ), i.e. electrically connect them with one another by way of contact bridge  9 . Mating power contacts  3   a  can therefore be configured as movable contacts  3   a  which are movable relative to fixed contacts  3 . 
     The base  11  can consist of electrically non-conductive material and can therefore represent a galvanic isolation. In an embodiment, the contact bridge  9  can be galvanically isolated from other elements. 
     Contact bridge  9  is furthermore attached to base  11  by way of spring assembly  13 . An actuating element  17  extending along an axis  15  is likewise attached to base  11 , as shown in  FIG.  2   , and allows switching contact assembly  7  to be actuated/moved in the switching direction  19 . Contact bridge  9  is attached to base  11  in a manner resilient in switching direction  19 . Contact bridge  9  is attached to base  11  also in the direction opposite to switching direction  19 , which shall be discussed in the following figures. 
     In the embodiment shown, spring assembly  13  of switching contact assembly  7  comprises two spring elements  21  bearing directly against one another. A first spring element  21   a  of spring assembly  13  is inserted into a second spring element  21   b  of spring assembly  13 , as shown in  FIGS.  2  and  3   . The spring elements  21   a,    21   b  can have the same or different spring constant and/or spring stroke. These can have a smaller installation space than spiral springs for the same spring force, at least along the spring direction, which presently corresponds to the switching direction. In addition, a spring assembly  13  can generate a predetermined spring force within tighter tolerances than a spiral spring while having the same spring length. The spring assembly  13  can be configured as an elliptical spring. 
     A spring element  21 , second spring element  21   b  of spring assembly  13  in the embodiment shown, is configured as a contact bridge retainer  23 . Contact bridge retainer  23  holds contact bridge  9  at base  11 . Various devices can be used to attach the second spring element  21   b  to the base  11 . Purely by way of example, the second spring element  21   b  can be clipped on, adhesively bonded, riveted or screwed on. 
     Another spring element, first spring element  21   a  of spring assembly  13  in the embodiment shown, is arranged between contact bridge retainer  23  and contact bridge  9 . The first spring element  21   a  and/or the second spring element  21   b,  i.e. also the contact bridge  9 , can be a punched and bent part, i.e. manufactured to be punched out of sheet metal. 
     The spring assembly  13  can also be formed by more than two spring elements that bear directly against one another. The spring force of the spring assembly  13  can be scaled with the number of spring elements. 
     The spring elements  21   a,    21   b  can be deflectable away from the contact bridge  9 . Two symmetrical spring legs may be provided for every spring element  21   a,    21   b  and can be deflectable symmetrically. In particular, the at least two spring elements  21   a,    21   b  can each bear directly against one another with their central region or section. The spring elements  21   a,    21   b  can bear entirely directly against one another along a longitudinal extension. The longitudinal extension of a spring element  21   a,    21   b  or the contact bridge  9  corresponds to a direction that lies in a plane that is spanned by the deflecting spring assembly. Accordingly, a transverse direction can be defined which can be defined to be perpendicular to this plane spanned by the deflecting spring assembly  13 . 
     The second spring element  21   b  can have a configuration that is similar to a cage or can form a cage in which the first spring element  21   a  is received. The first spring element  21   a  can be received in a positive-fit manner in the second spring element  21   b.  The first spring element  21   a  may be received loosely in the second spring element  21   b  and can therefore be detached therefrom. If the first spring element  21   a  is received in the second spring element  21   b  in a positive-fit manner, the positive-fit connection be established in particular along the longitudinal extension of the spring assembly  13 . The second spring element  21   b  can also be received in the first spring element  21   a  in a positive-fit manner in a motion relative to the first spring element  21   a  in and in a direction opposite to the transverse direction. For this purpose, the second spring element  21   b  can have a cross section that is U-shaped, at least in sections, when viewed in the longitudinal extension. 
     A region of the first or the second spring element  21   a,    21   b,  around which the respective spring legs can be deflected or deflect in or in a direction opposite to the switching direction  19 , can be regarded to be the bending axis. The bending axis can therefore be formed by a volume area of the first and/or the second spring element  21   a,    21   b  and not just denote a (one-dimensional) line. 
     As shown in the exploded drawing of switching contact assembly  7  according to the invention in  FIG.  3   , contact bridge retainer  23  comprises two contact bridge retaining legs  27  which are spaced apart from one another in a transverse direction  25  of contact bridge  9  that is oriented to be transverse to switching direction  19 . Contact bridge  9  is attached to contact bridge retainer  23  by way of contact bridge retaining legs  27 . The contact bridge retaining legs  27  extend away from a central region of the second spring element  21   b  configured as a contact bridge retainer  23  and can be bent in the switching direction  19  away from the central region. 
     Contact bridge retaining legs  27  form a lug  27   a  in which a post  28  of contact bridge  9  is received. This prevents a further motion of contact bridge  9  in switching direction  19 . The contact bridge retaining legs  27  can then each represent a mechanical stop for the contact bridge  9 . The contact bridge  9  is held to be movable up to this stop. In a state of rest of the spring assembly, the posts  28  of the contact bridge  9  can bear against the stops. 
     When the spring assembly  13  is at rest, it can be preloaded. Contact bridge  9  is supported by spring assembly  13  in the direction opposite to switching direction  19 . The contact bridge retaining legs  27  can be oriented parallel to the switching direction  19  and face each other along the transverse direction  25 . 
     As shown in  FIG.  3   , contact bridge retainer  23  comprises four attachment projections  29  for attaching it to base  11 . Attachment projections  29  extend from a central region  31  of contact bridge retainer  23  in or in a direction opposite to transverse direction  25 . One contact bridge retaining leg  27  each is located between two attachment projections  29 . Contact bridge retaining leg  27  is bent substantially in switching direction  19 . 
     The attachment projections  29  can be, for example, lugs that are punched out and particularly extend to be perpendicular to the switching direction  19 . The second spring element  21   b  configured as a contact bridge retainer  23  can then be connected to the base  11  and at the same time the first spring element  21   a  can be inserted (in a positive-fit manner) into the second spring element  21   b.  The attachment projections  29  can be provided in pairs, but switching contact assemblies with an odd number of attachment projections  29  are also conceivable. 
     The orientation of the attachment projections  29  may be perpendicular to the switching direction  19 , so that a spring force of the spring assembly  13  acting in the switching direction  19  acts perpendicular to the attachment of the second spring element  21   b  to the base  11  by way of attachment projections  29 . This has the advantage that, when the switching contact assembly  13  is actuated in the switching direction  19 , precisely the connection between the second spring element  21   b  and the base  11  cannot be released at the base  11 . 
     The bending axis can extend between two attachment projections  29  so that the deflecting spring legs are mounted in that region of those spring elements  21   a,    21   b  that also comprises the bending axis. This has the advantage that the attachment of the second spring element  21   b  to the base  11  and therefore the spring assembly  13  to the base  11  is not or only slightly stressed by a deflection of the spring assembly  13 . If the bending axis and an axis of the attachment are not disposed on top of one another or close together, then the deflection of a spring leg of the first or the second spring element  21   a,    21   b  can lead to an excessive force being applied to the attachment axis, since, if the bending axis and the attachment axis are spatially separated, a lever with two lever arms can form and a force acting at the spring leg force can be increased. This can mechanically stress the attachment of the spring assembly  13  to the base  11  or even lead to a defect in the attachment (for example, the attachment projections breaking out of the attachment openings). 
     In an assembled state  33 , shown in  FIG.  2   , first spring element  21   a  is received in second spring element  21   b  that is configured as a contact bridge retainer  23 , in that both contact bridge retaining legs  27  of contact bridge retainer  23  are each disposed in a recess  35  of first spring element  21   a.  This prevents a relative motion of first spring element  21   a  against contact bridge retainer  23  along a longitudinal direction  37 . Furthermore, such a relative motion in transverse direction  25  is blocked by the reception of contact bridge retaining legs  27  in recesses  35 . 
     In switching direction  19 , first spring element  21   a  is supported on contact bridge  9  at two mounting points  40  in a manner resilient in a direction opposite to switching direction  19 . 
     Entire spring assembly  13  is therefore supported in a resilient manner on contact bridge  9  by way of mounting points  40 , wherein a motion of contact bridge  9  in switching direction  19  is restricted by contact bridge retaining legs  27  configured as lugs  27   a.  Such a mounting point  40  for the contact bridge  9  can be located at each end of the contact bridge  9  located in and opposite to the longitudinal direction. The mounting points  40  can be punctiform or linear, wherein the linear form is may cause less wear as compared to punctiform contact, and the mounting point  40  of the first spring element  21   a  is not pressed into the material of the contact bridge  9  even after a large number of switching cycles. 
     Each mounting point  40  provided by the first spring element  21   a  can mount the contact bridge  9  in a resilient manner independently of other mounting points  40  by way of a spring leg or several spring legs forming a spring leg assembly. Two mounting points  40  may be provided, while three mounting points  40  are also conceivable. 
     When switching contact assembly  7  strikes with mating power contacts  3   a  in switching direction  19  against power contacts  3 , contact bridge  9  moves towards base  11 , wherein this motion is guided by posts  28  sliding in lugs  27   a  in a direction opposite to switching direction  19 . In the process, spring assembly  13  is deflected in a direction opposite to switching direction  19 . 
     As shown in  FIG.  3   , base  11  of switching contact assembly  7  is assembled from two parts  39 ,  39 ′. A first part  39  comprises positioning elements  41 . In the embodiment shown, they are configured as positioning pins  43  and are used to position the two parts  39  of base  11  relative to one another and to attach the at least two parts  39 ,  39 ′ of base  11 . The positioning elements  41  can have different cross sections, for example round, square or trilobular (triangular). For this purpose, positioning pins  43  are inserted into corresponding positioning openings  45  of a second part  39 ′. The base  11  can also be configured such that it can be assembled from three or more parts  39 , wherein at least two parts create the positive-fit connection between the base  11  and the spring assembly  13  when being assembled. The positioning elements  41  can be separate elements (similar to a dowel) but are monolithically connected to one of the at least two parts  39  of the base  11 . 
     The first part  39  of base  11  comprises a projection  47  which is oriented to be substantially perpendicular to switching direction  19 . Second part  39 ′ comprises a recess which is oriented to be substantially perpendicular to switching direction  19  and which is referred to as a further recess  49  to distinguish it from recess  35  in first spring element  21   a.    
     In assembled state  33 , projection  47  engages in further recess  49 , as shown in  FIG.  4   . Firstly, this serves to connect two parts  39 ,  39 ′ as well as, secondly, to increase a creepage distance between spring assembly  13  (it is electrically connected to contact bridge  9 ) and an actuating element  53  configured as an axis  51 . 
     A disk-shaped head  56  of actuating element  53  is inserted into corresponding axis receptacles  57  of parts  39 ,  39 ′, wherein in assembled state  33  of base  11 , a positive-fit connection forms between axis receptacles  57  and actuating element  53 . Actuating element  53  is held by base  11 , as shown in  FIG.  4   . 
       FIG.  4    shows switching contact assembly  7  according to the invention in a sectional view. It can be seen that positioning pins  43  are inserted into corresponding positioning openings  45  and projection  47  is inserted into further recess  49 . A positive-fit connection  59  is formed between axis receptacles  57  and actuating element  53 . 
     Contact bridge  9  is supported by way of spring assembly  13  in a resilient manner against base  11 , wherein spring assembly  13  is supported by two mounting points  40  on contact bridge  9  and a motion of contact bridge  9  in switching direction  19  is restricted by contact bridge retaining leg  27  that is configured as a lug  27   a.    
       FIG.  5    shows switching contact assembly  7  according to the invention in a partially sectioned view. Base  11  is shown there in assembled state  33 , in which two of four attachment projections  29  can be seen. Attachment projections  29  are received in attachment openings  55  that are provided by each part  39 . Attachment projections  29  require no additional tools to insert them into corresponding openings in the base  11 . Such attachment openings  55  of the base  11  can be configured to be complementary to the cross section of the attachment projections  29 . The base  11  can be made of a plastic material or can comprise at least one plastic material.  58   
     Furthermore, attachment projections  29  comprise latching and/or barbed hooks  58  with which they are attached in attachment openings  55 . The latching and/or barbed hooks  58  can displace the material on the inside of the attachment opening  55  and engage in the material of the attachment opening  55 . The at least one latching and/or barbed hook  58  of the attachment projection  29  can then prevent the attachment projection  29  from being able to be removed from the attachment opening  55 . The plugging process can therefore be non-reversible. 
     The attachment of contact bridge  9  to base  11  is therefore perpendicular to switching direction  19 . When switching contact assembly  7  is actuated, the connection between attachment projections  29  and base  11  can therefore be prevented from detaching. 
     The switching contact assembly  7  and electrical switching element  1  which ensure a sufficiently high and sufficiently precisely adjustable spring force in the smallest possible installation space.