Patent Publication Number: US-9905950-B2

Title: Electric contact means and electrical cable assembly for the automotive industry

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of European Application No. 15153319.7, filed Jan. 30, 2015. 
     FIELD OF THE INVENTION 
     The present invention relates to an electric contact, and more particularly, to a socket or plug contact. 
     BACKGROUND 
     A large number of electric connections, particularly electrical plug connections, are known which serve to transmit electric currents, voltages and/or signals with a largest possible bandwidth. Particularly in the automotive industry, such connections must safeguard a faultless transmission of electric power, signals and/or data in thermally charged, polluted, moist or chemically aggressive surroundings. 
     Due to a wide range of applications for such connections, a large number of specifically configured electric plug contacts are known, particularly crimp-contacts. In the field of electrical power contacting for the automotive industry, aside from a crimp-contact, only circular high-voltage or high-current contacts are known which could easily be stamped out of milled metal strips. In a rectangular high-voltage or high-current contact, an electric contact is provided by many filigree contact lamellas, wherein all contact lamellas have the same design and are bound to a contact cage at both longitudinal end portions. Due to the position of the contact lamellas in the contact, an amperage varies per contact lamella; a balanced current distribution is not possible with such a contact. Furthermore, the many filigree contact lamellas lead to a non-robust, damageable contact. 
     A known contact comprises identical contact lamellas wherein some contact lamellas are located more closely to a conductor-crimping section of the contact than several other contact lamellas. When using the contact, because the current always takes the path of least resistance, this leads to the problem that the contact lamellas which are located more closely to the conductor-crimping section carry more electric current than those which are located further away from the conductor-crimping section. The contact lamella located closest to the conductor-crimping section carries the most current and the one furthest away from the conductor-crimping section only carries a very small amount or hardly any current. 
     SUMMARY 
     An object of the present invention, among others, is to provide a robust electric contact with a balanced current distribution. The disclosed electric contact has an electric contact section including a plurality of contact springs with different geometrical shapes and a connecting section connected to an electric conductor. 
    
    
     
       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 top view of a contact section of an electric contact according to a first embodiment of the invention; 
         FIG. 2  is a top view of a contact section of an electric contact according to a second embodiment of the invention; 
         FIG. 3  is a perspective view of a contact section of the electric contact according to a third embodiment of the invention; 
         FIG. 4  is a perspective view of a contact section of an electric contact according to a fourth embodiment of the invention; and 
         FIG. 5  is a top view of the contact section of  FIG. 4 , wherein electric resistivities of contact springs and electric resistivities of their corresponding bulks have been schematically indicated. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
     The present invention in the following will be described in more detail in conjunction with embodiments of an electric contact  1 . The contact  1  may be a contact for transmitting electrical power, such as via a copper or aluminium cable, and may be used in the automotive industry. However, the invention is not limited to such embodiments, but may be applied as defined by the invention to all contacts and all conductor materials. These embodiments are provided so that this disclosure will be thorough and complete and still fully convey the scope of the invention to those skilled in the art. 
     The electrical contact  1  of the present invention will be described with reference to  FIGS. 1-5 . The electrical contact  1  includes a contact section  10 , a mechanical transitional section  20 , and a connecting section  30 . The major components of the invention will now be described in greater detail. 
       FIG. 1  shows the first embodiment of a contact section  10  having four contact springs  110  equally distanced from one another and all having approximately the same length. Of course, it is possible to apply less or more than four equally distanced contact springs  110  in the contact section  10 . Here, the contact springs  110  of the contact section  10  are all bound to only one side of the contact body  100 . The contact body  100 , for example as a partial body  100  of the contact  1 , may be configured as an spring contact body  100 , a contact retainer  100 , a contact cage  100 , a receptacle  100 , or other bodies known to those with ordinary skill in the art. In the following, such a configuration with contact springs  110  fixed to only one side of the contact body  100  is also referred to as an arrangement  102  of contact springs  110 . 
     As shown in  FIG. 1 , the contact springs  110  are robust by having different widths, while the lengths and the thicknesses of the contact springs  110  remain equal. Compensation of the contact normal forces may herein be implemented by the widths of the contact springs  110 ; as a contact normal force of a contact spring  110  becomes lower, its width may be increased a little more, or as a contact normal force of a contact spring  110  becomes higher, its width may be increased a little less than explained in the following. This may alternatively or additionally also be carried out by different distances between the contact springs  110 . The contact springs  110  have contact areas  122 . The contact areas  122  may, for example, be a contact protrusion  122 , projection  122 , corrugation  122  etc., of the contact spring  110 . 
       FIG. 2  represents a second embodiment of the invention of the contact section  10  also having four contact springs  110  each with different widths. In the second embodiment, however, the contact springs  110  are not equally distanced from one another and do not have the same approximate lengths. The different lengths of the contact springs  110  may be carried out by increasing an area of the contact body  100  in a middle area of the contact section  10  in comparison to  FIG. 1 , wherein the tip ends of the contact springs  110  may be arranged in a straight line which may be parallel to an edge of the counter-contact  5 . Further, the middle area of the contact section  10  may be approximately rectangular, wherein the tip ends of the contact springs  110  may be arranged in a straight or in a curved line which may be angled with respect to the edge of the counter-contact  5 . 
     In order to not excessively weaken a rigidness of the contact section  10  due to the optionally stamped-out contact springs  110 , the contact springs  110  may be arranged in an alternatingly opposite manner in an open inner frame  16  of the contact section  10 , as shown in  FIG. 3 . This for example means that in a longitudinal direction L of the contact  1 , one contact spring  110  is connected to a side of the contact section  10  which is located more to the right (or more to the left, respectively), whereas the contact spring  110  which in longitudinal direction L is optionally positioned directly adjacent is then connected to an opposite side of the contact section  10 ; located more to the left (or more to the right, respectively). 
     As a result, the contact springs  110  arranged opposite to each other in a portion of the contact section  10  interlock or engage. Here, each side with the respective contact springs  110  constitutes an arrangement  102  of contact springs  110  wherein these two arrangements  102  intermesh and thereby constitute an array  104  of contact springs  110  shown in  FIG. 3 . One of the two arrangements  102  in a single array  104  may comprise one more contact spring  110  than the directly opposite and adjacent arrangement  102  of this array  104 . If for example two arrays  104 ,  104  are provided in a layer  12 ,  14  as in  FIG. 4  of the contact section  10 , the two inner sides of the two arrays  104  may comprise one contact spring  110  less than the two outer sides of the two arrays  104 . Of course, this may be carried out in a converse manner, as would be appreciated by one with ordinary skill in the art. 
     An inventive configuration of two arrays  104 ,  104  (or for example four arrangements  102 ,  102 ;  102 ,  102 ) of contact springs  110  in the contact section  10  is shown in  FIG. 3 , depicting the third embodiment of the invention. In a portion of the contact section  10 , contact springs  110  having smaller widths are provided in the proximity of the connecting section  30  (not shown in  FIG. 3  but indicated by the reference numeral in brackets). Contact springs  110  having larger widths are arranged further away from the connecting section  30 . The contact springs  110  and/or their contact areas  122  become wider with an increasing distance from the connecting section  30 . This may analogously be applied to the lengths of the contact springs  110 . 
     The electrical contact  1  may have a straight, angled, or curved configuration, and may be configured as a crimp-contact  1 . The contact  1  may alternatively be an electro- or ultrasonic-welding contact  1 . The contact  1  may be configured as a female-, socket- or plug-contact, a receptacle, a plug-in sleeve, a coupling, or other contacts known to those with ordinary skill in the art. The contact  1  may have a closed configuration in several parts, in one piece, in one material piece or in an integral form optionally made from a metal or metal alloy. The contact springs  110  may be directly stamped into an electric contact body  100  of the contact  1 . 
     Furthermore, the contact  1  comprises an electric and mechanical connecting section  30  for an electric conductor  2  of the electrical cable, and optionally a mechanical fastening section (not shown) for an electrical isolation (not shown) and, if suitable, for the conductor  2  of the cable. The electrical cable, wire, or conductor  2  provided with the inventive contact  1  may further be referred to as a cable assembly, a pre-assembled or ready-made cable, or an electrical wiring harness. 
     In the exemplary contact  1  of  FIGS. 4 and 5  the connecting section  30  and the fastening section are designed as crimping sections; the connecting section  30  is designed as a conductor-crimping section  30  and the fastening section is designed as an isolation-crimping section. A mechanical transitional section  20  is between the contact section  10  and the connecting section  30 , and between the contact section  30  and the fastening section, a mechanical transitional section is optionally arranged which separates crimping lugs or wings of the conductor  30  and the isolation-crimping section. The electric conductor  2  of the electrical cable may further be an electric (litz) wire, lead, strand, flex, cord etc. mechanically clamped, crimped, brazed, soldered, compacted, welded etc. on/at the connecting section  30  of the contact  1 . 
     A counter-contact  5 , as shown in  FIGS. 1 and 2 , may be made from a milled metal strip. The counter-contact  5  may be designed in an analogous manner to the contact  1 . In this context, the counter-contact  5  may be configured as a tab- 5  or pin-contact  5 , a fast-on tab  5 , a flat plug  5 , or other types of contacts known to those with ordinary skill in the art. 
     The contact  1  is configured for being plugged together with the electric counter-contact  5 , as shown in  FIGS. 1 and 2 . The electric and mechanical contact section  10  of the contact  1  is plugged together with the contact-section of the counter-contact  5 , wherein the respective contact springs  110  are provided for mechanically contacting the counter-contact  5 . 
     In order to obtain a balanced current distribution through the contact section  10  to the connecting section  30  and in the connecting section  30  to the herein electrically connected electric conductor  2 , according to the invention, a total electric resistance R has to be equalized for some or all electric contact springs  110 . This may be done with different materials and/or a different geometry of the contact section  10  and/or the contact springs  110 . The geometries, particularly a width and/or a length, of the respective contact springs  110  are adapted among themselves according to their position in the contact section  10  with regard to the connecting section  30 . 
     Since a contact spring  110  with a smaller width has a higher electric resistivity R cs  than a contact spring  110  with a larger width, the cross sections of the contact springs  110  in the contact section  10  are inventively adapted. According to the invention, contact springs  110  with smaller widths are located comparatively closely to the connecting section  30 , and contact springs  110  with larger widths are located comparatively far away from the connecting section  30 . 
     Further, a contact normal force of a contact spring  110  on the counter-contact  5  may have a significant influence on how much current may flow through such a (point or area) connection. Therefore, the lengths of the contact springs  110  may also be adapted. Here, a contact spring  110  with a smaller width has a lower contact normal force than a contact spring  110  with a larger width, so the length of a contact spring  110  with a larger width may be increased in order to obtain constant normal forces for the respective contact springs  110 . According to the invention, contact springs  110  with shorter lengths may be provided which are located comparatively closely to the connecting section  30 , and contact springs  110  with longer lengths are provided which are located comparatively far away from the connecting section  30 . Herein, the contact springs  110  with shorter lengths also have smaller widths, whereas the contact springs  110  with longer lengths also have larger widths. 
     The closer a contact spring  110  is to the connection section  30 , the smaller and the shorter the contact spring  110 . The farther away a contact spring  110  is from the connection section  30 , the wider and the larger the contact spring  110 . Here, each contact spring  110  is particularly designed in a way that a bulk resistivity R b  along an electrical path is equalized over the contact section  10  or a part of or the whole contact  1  by a resistivity R cs  of the respective contact spring  110 . 
     In general, a shape of a contact spring  110  is arbitrary. For example, a contact spring  110  may be i-shaped, v-shaped or u-shaped (filled). The contact spring  110  may be the shape of a tongue, an arm, a lamella, a nose, a strip, a bar or a rod. Here, a horizontal, a vertical and/or an elevation projection of a contact spring  110  or a distribution of a horizontal, a vertical and/or an elevation projection of a contact spring  110  is arbitrary; the distribution of a cross section or profile of the respective contact spring  110  may be chosen in accordance with the functions mentioned herein. Respectively, two or more contact springs  110  having similar positions in the contact section  10  with regard to the connection section  30 , i.e. having identical bulk resistivities R b  in the contact  1  or its contact body  100 , may be constructed in a geometrically identical manner having identical contact spring resistivities R cs . 
     According to the invention, the electric resistivity R cs  of the respective contact spring  110  is particularly adjusted between an electric and mechanical contact area  122  and its connection or junction to the contact body  100 . An amount of material and its geometry between the contact area  122  and the connection of the contact spring  110  to the contact body  100  determines the electric resistivity R cs  for the contact spring  110  itself; i.e. the material of the contact spring  110  aside/on the off-side of the residual contact body  100 . 
     This electric resistivity R cs  is adjusted taking an electrical resistivity R b,n  of a corresponding bulk n=1 to 6 or the electrical resistivities R b,n , . . . of the corresponding bulks n=1 to 6 of the contact body  100  and/or the connection section  30  into account, as shown in  FIG. 5 . According to the invention, the determined electric resistivity R cs  for a contact spring  110  due to their position (corresponding bulk n=1 to 6 or bulks n=1 to 6) in the contact body  100 , conversely determines the amount of material and a geometry between the contact area  122  and the connection of the contact spring  110  to the contact body  100 , i.e. a form of the contact spring  110 . This relates to a contact spring  110  which is connected to the contact body  100  in its longitudinal direction at one side to the contact body  100 . If a contact spring  110  is for example designed as a contact lamella  110 , i.e. if it is connected to the contact body  100  in its longitudinal direction at two sides of the contact body  100 , according to the invention this has to be carried out for both branches of the contact lamella  110 . 
     In the shown embodiments of the invention, each contact spring  110  is provided at only one side of the contact body  100 , particularly in an integral configuration or in one material piece with the contact  1 . According to the invention, contact springs  110 , are configured and installed in the contact body  100  in such a way that no primarily preferred path exists for the current which may flow through the contact springs  110 . All current paths through the respective contact spring  110  and away from this contact spring  110  should be approximately equally ‘attractive’ for the current. 
     Since contact springs  110  with smaller widths have higher electric resistivities (R cs ) the widths of the contact springs  110  according to the invention are set or selected in such a way that, when taking into account that a current flows through the contact body  10  and/or the contact  1 , the total electric resistance R=R cs +R b  of the respective contact spring  110  (index cs) and its corresponding bulk (index b) or bulks (index b) are approximately equal for all contact springs  110 . Furthermore, since contact springs  110  with larger widths have higher contact normal forces, their lengths may be increased in order to generate consistent contact normal forces by all contact springs  110  which may be pressed onto the counter-contact  5 . 
     On the one hand, the widths of the contact springs  110  increase continuously starting close to the connecting section  30  of the contact body  100  along the longitudinal direction L of the contact  1 ; the further away the contact spring  110  in question is from the connecting section  30 , the wider is its configuration. On the other hand, the lengths of the contact springs  110  may increase continuously starting close to the connecting section  30  of the contact body  100  along the longitudinal direction L of the contact  1 ; the further away the contact spring  110  in question is from the connecting section  30 , the longer is its configuration. This may analogously be applied to the widths and/or lengths of the contact springs  110  between their respective contact areas  122  and their respective connections or junctions to the contact body  100 . 
     The fourth embodiment of the inventive contact body  100 , the inventive contact section  10  and/or the inventive contact  1  which may be configured as a crimp contact  1  is depicted in  FIGS. 4 and 5 . The contact body  100  may be configured as a contact retainer  100  comprising an upper  12  and a lower layer  14  constituting the contact section  10 . The contact body  100  may accept counter-contact  5  in a 90°- and/or 270°-direction. Plug directions P, connection directions P or orientations P are indicated by an arrow having a continuous line in  FIG. 4 . Furthermore, the contact body  100  may be configured in such a way that the counter-contact  5  may be plugged in a 0°-direction (this plug direction P is indicated by an arrow with a dashed line in  FIG. 4 ). Other contact bodies  100  are applicable which may allow for different plug directions P (not shown). 
     Each layer  12 ,  14  of the contact retainer  100  shown in  FIG. 4  comprises at least one arrangement  102  of contact springs  110 . Each layer  12 ,  14  may also comprise at least one array  104  of contact springs  110 . Each layer  12 ,  14  particularly comprises two arrays  104 ,  104 ) of contact springs  110 , arranged side by side.  FIGS. 4 and 5  presently show five contact springs  110  in each array  104 , wherein each array  104  is composed of two arrangements  102  and wherein one arrangement  102  comprises two (inner longitudinal side of the respective inner frame  16 ,  16 ) and the complementary arrangement  102  of this array  104  comprises three contact springs  110  (outer longitudinal side of the respective inner frame  16 ,  16 ). As would be appreciated by one with ordinary skill in the art, the number of contact springs  100  could vary. 
     Those contact springs  110  of the arrangements  102 ,  102 ;  102 ,  102  or arrays  104 ,  104  having similar positions in the contact section  10  have approximately the same geometries, i.e. the same width, the same length and the same thickness. This presently applies to the contact springs  110  having nearly identical longitudinal positions in the contact section  10 . According to  FIG. 4 , four contact springs  110  of the twenty contact springs  110  of the contact section  10  respectively have similar positions in the contact section  10 . These positions are characterized by approximately identical bulk resistivities R b ; the lengths of the corresponding bulk or bulks of these four contact springs  110  are optionally approximately identical and may comprise an approximately identic geometry. 
       FIG. 5  illustrates the electric resistivities R cs,m  of the respective contact springs  110 , m (m=pos.  111  to  115 ) and the electric resistivities R b,n  of the corresponding bulk n or bulks n (n=pos.  1  to  6 ). The inventive equivalent total resistances R for each possible way of the current which may flow through the contact section  10  and into the connecting section  30  are as follows:
 
 R=/≈R   cs,111   +R   b,6   +R   b,5   +R   b,4   +R   b,1 =/≈
 
=/≈ R   cs,112   +R   b,3   +R   b,2   +R   b,1 =/≈
 
=/≈ R   cs,113   +R   b,5   +R   b,4   +R   b,1 =/≈
 
=/≈ R   cs,114   +R   b,2   +R   b,1 =/≈
 
=/≈ R   cs,115   +R   b,4   +R   b,1   =/≈R.  
 
     According to this system of equations and with given bulk resistances R b,n ; R b,1 , R b,2 , R b,3 , R b,4 , R b,5 , R b,6 , for each contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115 , the inventively required electric resistivities R cs,m ; R cs,111 , R cs,112 , R cs,113 , R cs,114 , R cs,115  may be calculated. Furthermore, a geometry of the respective contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115  may be calculated and chosen from the calculated electric resistivities R cs,m ; R cs,111 , R cs,112 , R cs,113 , R cs,114 , R cs,115 . 
     The electric resistance of a contact spring  110 , m is given as follows:
 
 R   cs,m =(ρ· l   cs,m)   /A   cs,m ,
 
     ρ being a specific electric resistance of the material of the contact  1 , l cs,m  being a (medium) length of the respective contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115 , and A cs,m  being a (medium) cross section of the respective contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115 . 
     Since a material thickness of the contact  1  is at least partially equal, an adaption of a geometry of the respective contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115  may be accomplished by an adaption of the width of the respective contact spring  110 ;  111 ,  112 ,  113 ,  114 ,  115 . Further, according to the formula for the electric resistance R cs ,m of a contact spring  110 , m, an electric resistance R b,n ; R b,1 , R b,2 , R b,3 , R b,4 , R b,5 , R b,6  for the bulks n (n=pos.  1  to  6 ) may also be estimated or calculated.