Patent Publication Number: US-2020303873-A1

Title: Electrical contact pin and plug connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/EP2018/085865, filed on Dec. 19, 2018, which claims priority under 35 U.S.C. § 119 to European Patent Application No. 17209060.7, filed on Dec. 20, 2017. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electrical contact pin and, more particularly, to an electrical contact pin having an outer thread for fastening the electrical contact pin to a plug connector. 
     BACKGROUND 
     In electronics, in particular in medium voltage electronics, electrical contact pins and plug connectors comprising such electrical contact pins are known. In the literature, the term “medium voltage” is not uniformly defined. According to the NEMA (National Electrical Manufacturers Association) and the IEEE (Institution of Electrical and Electronic Engineers), medium voltage describes voltages in the order of 0.6 kV up to 100 kV. Electrical contact pins and plug connectors, however, may be applied for all obtainable voltages. 
     In general, electrical contact pins applied in the field of medium voltages comprise a thread for installation in a plug connector. The plug connectors usually have a monolithic insulating sheath or an insulating layer or a screen in order to protect a technician or a person adjacent to an energized cable/connector and to allow lower clearance to grounded parts. 
     During the installation of the electrical contact pin to the plug connector, the contact member, with which the electrical contact pin is electrically connected, may be improperly positioned within the insulating sheath. Installation of the electrical contact pin may thus be complicated, the electrical contact pin may get stuck during the installation process, and in the worst case, the electrical contact pin may be damaged as the highly conductive metallic material of the pin is rather soft. 
     SUMMARY 
     An electrical contact pin for a plug connector includes an outer thread fastening the electrical contact pin to the plug connector and a centering element having a tapered section centering and/or positioning the electrical contact pin. The centering element extends from an end of the electrical contact pin. 
    
    
     
       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 side view of an angled plug; 
         FIG. 2  is a top view of the angled plug of  FIG. 1 ; 
         FIG. 3A  is a side view of an electrical contact pin according to an embodiment; 
         FIG. 3B  is a perspective view of the electrical contact pin of  FIG. 3A ; 
         FIG. 4  is a side view of an electrical contact pin according to another embodiment; 
         FIG. 5  is a perspective view of the electrical contact pin of  FIG. 3A  during assembly with a contact member; and 
         FIG. 6  is a sectional side view of a plug connector according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     In the following, specific embodiments of the inventive electrical contact pin as well as the inventive plug connector will be described based on the accompanying figures. The figures merely depict particular embodiments which are shown exemplarily but which do not limit the scope of protection defined by the claims. The technical features of the following embodiments may be arbitrarily combined and/or omitted if the technical effect obtained with the omitted technical feature is not relevant to the invention. The same technical features, as well as technical features having the same technical effect, will be referred to using the same reference numeral in each case. A repetitive description of technical features will be omitted, whereas differences between the embodiments will be emphasized. 
     In  FIG. 1  a plug connector  1 , which is embodied as an angled plug  3  is shown in an assembled state  1   a  in a side view. Here, only an insulating sheath  5  is shown. Further elements located inside the insulating sheath  5  will be described with reference to  FIG. 2 . 
     The plug connector  1  may be used to establish an electrical connection between a cable  7  and a schematically shown mating plug connector  9  which is connected to a further cable  7   a.    
     In other embodiments, the mating plug connector  9  may be a bushing on a switchgear or transformer. In the case of a so-called “elbow connector”, a further cable  7   a  may be used occasionally. The insulating sheath  5  protects a user from electrical hazards and injuries resulting from an electric shock. 
     The plug connector  1  may be considered according to relevant standards (e.g. IEC 60502-4). Two types of contacts of so-called “separable connectors” are differentiated: “plug-in” separable connectors or sliding contact connectors and “bolted” type (screwable) separable connectors. Concerning plug connectors, there are two types of separable connectors which are differentiated: screened and unscreened types. Both types use conductive inserts typically molded in insulating material, whereby screened connectors use an additional layer of conductive material on the outside. The conductive material is typically similar to the insulating material, but may be mixed with conductive filler. Furthermore, adapters as additional components may be used to adapt on size of connector body to different cable sizes. In the case of a screened connector, a screen may protect the user. 
       FIG. 2  shows a top view of the plug connector  1 . A ring-shaped elastic collar  11  is provided to protect a pin receptacle  13  from dust and/or water, and to insulate it from elements outside the pin receptacle  13 . The insulating sheath  5  is generally made from an elastic insulating material  15  and formed monolithically with the elastic collar  11 . 
     The insulating sheath  5 , as shown in  FIG. 1 , has a sheath receptacle  17  which is indicated by a dotted line. The sheath receptacle  17  is composed of the pin receptacle  13  and a contact receptacle  19 . A contact member  21  is received in the sheath receptacle  17 , wherein a connection region  23  is located in an angled portion  25  of the sheath receptacle  17  and is thus visible through the pin receptacle  13 , as shown in  FIG. 2 . 
     The connection region  23  of the contact member  21  is embodied as a cable lug  27  having a through hole  29  with an inner thread  31 , as shown in  FIG. 2 . The through hole  29  is not centered in the pin receptacle  13 , thereby rendering the installation of an electrical contact pin (to be described in the following figures) difficult. 
     An electrical contact pin  33  according to a first embodiment is shown in  FIGS. 3A and 3B . The electrical contact pin  33  extends along a longitudinal direction  35  indicated by a dash-dotted line. The electrical contact pin  33  comprises an outer thread  37 , which may be used to fasten the electrical contact pin  33  to the plug connector  1 , exemplarily to the plug connector  1  shown in  FIGS. 1 and 2 . 
     The electrical contact pin  33 , as shown in  FIGS. 3A and 3B , has a centering element  39 . The centering element  39  has a tapered section  41  which extends from an end  43  of the electrical contact pin  33  along the longitudinal direction  35 . The longitudinal direction  35  corresponds to the direction of extension  45  of the electrical contact pin  33 . The tapered section  41  is to be understood as a section which becomes progressively smaller towards one end, i.e. towards the end of the tapered section  41  away from the electrical contact pin  33 . A diameter of a cross-section of the tapered section  41  decreases as the distance from the electrical contact pin  33  increases. 
     A spacer  47  is disposed between the tapered section  41  and the outer thread  37 . The spacer  47  is embodied as a circumferential notch portion  49 , which is shown in more detail in a circle  51  in  FIG. 3A , which shows a cross-section  53  of the circumferential notch portion  49  as seen in the circumferential direction  50 . The circumferential notch portion  49  has a continuous cross-section  53   a.    
     At an end  44  opposite to the centering element  39 , a further centering element  55  is disposed, as shown in  FIGS. 3A and 3B . The further centering element  55  also has a tapered section  41 . Each of the two tapered sections  41  of the electrical contact pin  33  has a partially spherical shape  57  or a frustoconical shape  59  for the centering element  39  and the further centering element  55 , respectively. 
     The tapered section  41  may have a cross-section, i.e. the section in a plane perpendicular to the extension direction of the electrical contact pin  33 , that is essentially circular, wherein in this case, the tapered section  41  may have the shape of a cone with its flat base located at the end of the electrical contact pin  33 . The cone, in an embodiment, is a right circular cone (not an oblique cone) and may be embodied as an entire cone or a cone with a cut apex resulting in a truncated cone. In a different embodiment, the tapered section  41  may have a polygonal shape with n edges. The tapered section  41  may exemplarily be embodied as a pyramid, i.e. with four edges. The pyramid may comprise an apex or may be cut and be embodied as a truncated pyramid. When the cross-section of the tapered section  41  has a polygonal shape, a circumscribed circle may be constructed that contains all edges of the polygon. The diameter of the circumscribed circle becomes progressively smaller towards the end of the tapered section  41 , i.e. away from the electrical contact pin  33 . In the case of a polygon-shaped cross-section of the tapered section  41 , the maximum diameter of the centering element  39  corresponds to the circumscribed circle or the largest dimension of the centering element  39  in the plane of the cross-section. 
     In an embodiment, an axis of symmetry (for example rotational axis) of the tapered section  41  coincides with an axis of symmetry of the electrical contact pin  33 . This allows for centering and/or positioning of the electrical contact pin  33  independently of an initial rotational orientation of the electrical contact pin  33 . 
     As shown in  FIGS. 3A and 3B , the electrical contact pin  33  further comprises an abutment member  61  having an abutment surface  63 . The abutment surface  63  faces towards the centering element  39  and is oriented essentially perpendicular to the longitudinal direction  35 . In a different embodiment of the inventive electrical contact pin  33 , the outer thread  37  and/or the abutment member  61  may be located in a central portion  62  of the electrical contact pin  33 . 
     The outer thread  37  may be provided along the entire electrical contact pin  33 , or only at sections thereof, in particular at the ends of the contact pin  33  or adjacent to the abutment member  61 . The electrical contact pin  33 , in particular the abutment member  61 , may be embodied symmetrically, such that the same geometry of the plug connector  1  is obtained independently of the direction in which the electrical contact pin  33  is inserted into the contact member  21 . 
     In the embodiment of the inventive electrical contact pin  33  shown in  FIGS. 3A and 3B , a maximum diameter  65  of the centering element  39  is smaller than a minor diameter  67  of the outer thread  37 . Both diameters  65 ,  67  are smaller than an outer diameter  69  of the outer thread  37 . The abutment member  61 , which is also embodied as a stop member  71 , has a diameter  73  which is larger than the outer diameter  69  of the outer thread  37 . The centering element  39  and the abutment member  61  have a rotationally symmetrical shape  75  and the shape of a cylinder  77  in the embodiments shown in  FIGS. 3A and 3B . Both elements  39 ,  61  may have a cross-section in the form of a polygon; in this case, the term “diameter” refers to a circumscribed circle of said cross-section. 
     The abutment member  61  may be embodied as a cylinder but may also have a polygon-shaped cross-section. In this case, the diameter of the circumscribed circle of the abutment member  61  cross-section is larger than the outer diameter of the outer thread  37 . 
     An electrical contact pin  33  according to a second embodiment, as shown in  FIG. 4 , differs from the first embodiment of  FIGS. 3A and 3B  in the shape of the centering element  39 , which has a frustoconical shape  59 , i.e. the centering element  39  as well as the further centering element  55  have a frustoconical shape  59 . The electrical contact pins  33  shown in the embodiments of  FIGS. 3A, 3B, and 4  are in each case embodied as a monolithic part  79 . It is, however, possible for the centering element  39  and/or the further centering element  55  to be manufactured individually and separately, and attached to the electrical contact pin  33  prior to installation of the electrical contact pin  33  in the plug connector  1 . 
       FIG. 5  shows the electrical contact pin  33  of  FIGS. 3A and 3B  during assembly to the contact member  21  of a plug connector  1 . For the sake of visibility, the insulating sheath  5 , the sheath receptacle  17 , the pin receptacle  13  and the contact receptacle  19  are not shown in  FIG. 5  (see  FIG. 1 ). 
     The electrical contact pin  33  is moved along an insertion direction  81  such that the centering element  39  approaches the through hole  29 , which is provided with an inner thread  83 .  FIG. 5  shows an embodiment of the contact member  21 , which also comprises a chamfered entrance edge  85 , i.e. a circumferentially beveled or chamfered edge surrounding the through hole  29 . If the electrical contact pin  33 , in particular its tapered section  41 , abuts the chamfered entrance edge  85  of the contact member, a centering and positioning force  87  is exerted on the end  43  of the electrical contact pin  33 . It is to be noted that the direction of the centering and positioning force  87  shown in  FIG. 5  is exemplary and may vary depending on where the tapered section  41  abuts the chamfered entrance edge  85  of the through hole  29 . 
     The spacer  47  increases the distance between the centering element  39  and the outer thread  37  and allows for a larger angle of acceptance. The angle of acceptance is to be understood as an angle of the electrical contact pin  33  with respect to a normal direction of the inner thread  83  of the contact element into which the electrical contact pin  33  is inserted. In other words, with the spacer  47 , the electrical contact pin  33  may be reliably centered and/or positioned by the centering element  39 , even if an angular misalignment of the electrical contact pin  33  is present. The notch portion  49  prevents the outer thread  37  from being blocked at the inner thread  83  of the contact member  21 , wherein the continuous cross-section of the notch  49  avoids notch stress maxima which could result in cracks and further damage to the electrical contact pin  33 . 
     In all cases, an insertion force  89 , which is exerted on the electrical contact pin  33  in the insertion direction  81 , is split and one resulting component of the insertion force  89  is the centering and positioning force  87 , which is directed towards a central axis  91  of the through hole  29 . As can be seen at the further centering element  55 , the central axis  91  may be positioned at a distance from a center point  93  of the electrical contact pin  33 . The center point  93  is to be understood as the point through which the longitudinal direction  35 , shown in  FIG. 3A , extends through the further centering element  55 . For the sake of visibility, the longitudinal direction  35  is not shown in  FIG. 5 . 
     Upon further insertion of the electrical contact pin  33  into the through hole  29 , the outer thread  37  of the electrical contact pin  33  engages with the inner thread  83  of the through hole  29  and the electrical contact pin  33  may be screwed into the contact member  21 . The electric contact pin  33  may be screwed into the through hole  29  until the abutment surface  63  of the abutment member  61  abuts an electrical contact surface  95 , which is arranged circumferentially around the chamfered entrance edge  85  of the through hole  29 . 
     The abutment member  61 , more precisely the abutment surface  63  of the abutment member  61 , may be applied to establish a mechanical contact between the electrical contact pin  33  and the contact member  21  over an even area or surface. Such a flat abutment between both the contact pin  33  and the contact member  21  establishes the electrical connection between the contact pin  33  and the contact member  21 . Although the outer thread  37  of the electrical contact pin  33  is in mechanical and electrical contact with the inner thread  83  of the contact member, electrical current mainly flows through the abutment surface between the electrical contact pin  33  and the contact member  21 . The abutment member  61  may further comprise a flange section or a flange-like structure in order to increase the contact surface between the abutment member  61  and the contact member  21 . Further extensions of the abutment member  61  may be embodied to increase the contact surface. 
     In an embodiment, the inner thread  31  is recessed, such that the abutment surface  63  of the abutment member  61  abuts a surface surrounding the inner thread  31  in a central portion of the contact member  21 . The central portion of the contact member  21  is determined with respect to the extension of the (received) electrical contact pin  33 . 
     The abutment of the abutment member  61  automatically limits an insertion depth of the electrical contact pin  33  into the contact member  21 . The abutment member  61  may also be embodied monolithically with the electrical contact pin  33 . If the abutment is established, the abutment member  61  also acts as stop member  71 . 
     In an embodiment, in the assembled state, the electrical contact pin  33  is flush with the contact member  21 . The flush alignment may be realized by the abutment member  61 , wherein an overall length from the end of the centering element  39  to the abutment surface  63  of the abutment member  61  may equal a thickness of the contact member  21  into which the electrical contact pin  33  is screwed. Once the abutment between the abutment member  61  and the contact member  21  is established, the flush position of the electrical contact pin  33  is achieved. 
     The centering element  39  may be applied solely during the process of inserting the electrical contact pin  33  into the corresponding contact member  21 . Consequently, the mechanical and electrical requirements of the centering element  39  may differ from the requirements related to mechanical and/or electrical properties of the electrical contact pin  33 . For example, the centering element  39  may comprise a material different from the material of the electrical contact pin  33 . In order to avoid damage to the inner thread  83  of the contact member  21 , the centering element  39  may comprise a polymer with a lower hardness then the material of the inner thread  83  of the contact member  21 . A misaligned introduction of the electrical contact pin  33  into the contact member  21  may thus not damage the inner thread  83 . A polymer of the centering element  39  may therefore be considered as sacrificial material which does not negatively affect the integrity of the inner and/or outer thread. 
     In another embodiment, the centering element  39  and/or the spacer  47  are embodied monolithically with the electrical contact pin  33 . A monolithic embodiment has the advantage that it is easily produced and does not require further assembly steps. 
     The plug connector  1  is shown in the assembled state  1   a  in  FIG. 6 . The insulating sheath  5  has a T-shape  97  and receives the contact member  21  in the contact receptacle  19 , wherein the connection region  23  of the contact member  21  extends into the pin receptacle  13 , which is oriented essentially perpendicular to the contact receptacle  19 . A third embodiment of the electrical contact pin  33  is received and fixed in the connection region  23  by engaging the outer thread  37  with the inner thread  83  of the through hole  29 . 
     This assembly may also be applied in an elbow connector. The plug connector  1 , in the shown embodiment, has the contact member  21  oriented essentially perpendicular to the electrical contact pin  33 . This embodiment results in the angled plug  3 , wherein the contact member  21  is connected to and oriented parallel to a cable, which is essentially perpendicular to the electrical contact pin  33 . Angled plugs  3  allow for an electrical connection when installation space is limited. 
     In another embodiment of the T-connector, a through hole may be provided instead of the inner thread  83 , wherein the outer thread  37  may engage with and may be fixed to a separate element, e.g. a bushing located on the opposite end  44 . 
     The abutment member  61  and the outer thread  37  are arranged in the central portion  62  of the electrical contact pin  33 , as shown in  FIG. 6 . The abutment member  61  is embodied differently than in the previous figures and is provided with a screw nut  99  for attaching the electrical contact pin  33  to the contact member  21 . 
     The centering element  39  was applied to center the electrical contact pin  33  in an initial stage of the assembly (see  FIG. 5 ) and subsequently projects through the through hole  29  towards a first contact side  101  of the plug connector  1 , as shown in  FIG. 6 . On a second contact side  103  of the plug connector  1 , the electrical contact pin  33  extends from the connection region  23  of the contact member  21 , wherein the further centering element  55  may be applied for centering and/or positioning an additional element  105  that is also to be attached to the electrical contact pin  33 . The additional element  105  may be embodied as a further connector, an insulating member  107  or an extension embodied as a coupling piece. In an embodiment, the electrical contact pin  33  projects symmetrically through the contact member  21 , i.e. it extends symmetrically to both sides of the contact member  21 . The electrical contact pin  33  may be inserted into the contact member  21  so far that it projects through the contact member  21  in both directions along the extension of the electrical contact pin  33 . The electrical contact pin  33  may therefore be centered in the plug connector  1 . 
     One end of the electrical contact pin  33  may be applied as a central pin of the plug connector  1 , wherein the second end of the electrical contact pin  33  may represent a second connection possibility, which, to protect a user against electrical hazards, may be provided with a basic insulating plug or an insulating back plug. Such a plug connector  1  is known as a T-plug, which may allow one single cable to be simultaneously connected to two other cables. 
     However, typically, a separable connector may be connected to a bushing e.g. on a switchgear or transformer. T-plugs may thus enable an additional connection of components, e.g. to another T-plug, which can then be connected to another plug, and/or a surge arrester. The entire T-plug may be located within a T-shape  97  of the insulating sheath  5 , wherein the electrical contact pin  33  through and is electrically connected to the contact member  21  and provides two ends that allow an electrical connection with the contact member  21 . 
     It is to be noted that, in contrast to commonly known plug-in connectors, the electrical contact pin  33  or screwable T-connector is itself not primarily intended to transmit current, but to establish a “fixed” mechanical connection between the cable lug  27  and e.g. a conductor of a bushing. The electrical contact is made via the surfaces of the cable lug  27  and the bushing. 
     It is to be noted that the plug connector  1  shown in  FIG. 6  represents just one of a multitude of possible plug connectors  1 , wherein in particular the shape of the insulating sheath  5 , the shape and/or size of the pin receptacle  13  and/or contact receptacle  19  may be embodied differently in further possible embodiments. 
     The electrical contact pin  33  and the plug connector  1  allow for easy installation, reduced installation times and an increased durability against damage during assembly.