Patent Publication Number: US-2020303861-A1

Title: Insulation Displacement Connector For Sheathed Insulated Cables

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of Italian Patent Application No. 102019000003963, filed on Mar. 19, 2019. 
     FIELD OF THE INVENTION 
     The present invention relates to a connector and, more particularly, to an insulation displacement connector for sheathed insulated cables. 
     BACKGROUND 
     Insulation displacement connections have been extensively developed in the household appliances sector as well as in electronic appliances and more generally in the area of electrical signal transmission. Connections of this type are mostly used for electrical connections not exceeding 25 A and effectively allow a reduction in production costs and easier connection during the production process. In this application there is no need for preliminary operations on the wires or cables that have to be processed, such as stripping the insulation from the cable, thus making it possible to effectively increase production speed and reduce production costs. Thanks to this technology, different types of connection systems have been developed that allow wires or cables to be electrically connected to a connector, which normally includes an electrical terminal and a housing that houses this electrical terminal. 
     These connectors are commonly known as RAST connectors (from the German “Raster Anschluss Steck Technik”). This connector is based on a standard (RAST standard) that indicates a type of connection based on multiple connectors characterized by a certain “pitch”. Usually the abbreviation is followed by a number representing the particular spacing between the different interconnecting lines. For example, a RAST 5 interconnection comprises a connector with 5 mm pitch contacts. The RAST standard touches on a number of connector features, including external dimensions, color coding on the housing, polarization mechanisms to prevent mis-assembly, and locking mechanisms to increase interconnection stability. 
     These connectors must be able to pass specific tests that simulate the extreme conditions these connectors may encounter. Over time, these tests have become more and more selective in order to obtain connectors that are increasingly safe and able to meet the latest standards. 
     For example, as described in the UL 749 standard, new household dishwashers are required to have components of a defined flammability class or must pass the “Nichrome Wire Test” by 2020. During this test, the connector is used as a trigger point, energizing a nickel-chromium coil inserted in place of one of its contacts, energized at 11 A for 20 minutes. Most connectors on the market today create flame in the surrounding areas when subjected to such a test. For this reason, in many situations it is essential to make the connector fireproof in order to pass the test in an appliance. 
       FIG. 1  shows a RAST-type connector  100  with 5 mm pitch known in the prior art. The connector  100  shown in  FIG. 1  is commonly known as an “AMP multifitting mark II”, the technical characteristics of which can be found in the catalogue “RAST CONNECTOR SYSTEM IDC &amp; CRIMP CONNECTOR SYSTEM AND RAST TAB HEADER” (catalogue number 1-1773727-3, Revised 4-14) from TE Connectivity Ltd. This connector  100  has four interconnecting lines. 
     The connector  100 , as shown in  FIG. 1 , includes a single body with an upper portion  101  where the cables are coupled to the connector  100  and a lower portion  102  where the connector  100  is electrically connected to an external element. Inside the connector  100 , there is a terminal configured to allow electrical connection between the connector  100  and at least one cable to which the connector  100  is connected. 
     The cable includes a conductive inner section and an insulating cover commonly referred to as a sheath. The internal conductive section may comprise either a single wire or a plurality of twisted wires (strands) allowing even distribution of the current density passing through the cable. 
     SUMMARY 
     An insulation displacement connector connecting to a sheathed insulated cable has a housing including a first portion and a second portion mechanically engaging the first portion. The first portion is made of a different material than the second portion. 
    
    
     
       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 a connector according to the prior art; 
         FIG. 2  is a perspective view of a connector according to an embodiment of the invention; 
         FIG. 3  is a perspective view of a first portion of the connector of  FIG. 2 ; and 
         FIG. 4  is a perspective view of a second portion of the connector of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The present invention is described below in particular embodiments with reference to the accompanying drawings. The same numbers and/or references indicate the same and/or similar and/or corresponding parts of the system. The present invention, however, is not limited to the particular embodiments described in the detailed description below and illustrated in the figures, but rather the embodiments described simply exemplify the various aspects of the present invention, the purpose of which is defined by the claims. Further changes relating to the present invention will become clear to a person skilled in the art. Finally, those areas considered to be known to those skilled in the art have not been described in order to avoid unnecessarily obscuring the invention described. 
     As will be clear from the below description, although a particular general shape of connector is illustrated in the figures, clearly the same inventive concept presented here can be applied to any other type of connector having different shapes and characteristics from those described in the figure; to, for example, any of the connectors in the above-mentioned catalogue. 
     A connector  10  according to an embodiment of the invention is shown in  FIG. 2 . The connector  10  is a form of insulation displacement connector connecting to a plurality of sheathed insulated cables. The connector  10  has a housing configured to house a plurality of terminals inside the housing and isolate the terminals with respect to an area exterior of the connector  10 . The terminals are electrically connected to the sheathed insulated cables. 
     The housing of the connector  10 , as shown in  FIG. 2 , includes an upper first portion  11  and a lower second portion  12 . The connector  10  is formed by mechanical coupling between two different elements represented by the first portion  11  and the second portion  12 . The fact that the connector  10  is formed by two different mechanically coupled portions  11 ,  12  makes it possible to have a connector  10  formed of two bodies of different material, therefore having different mechanical and chemical properties. For example, if it has been established that the higher thermal stress occurs in a particular area of the connector  10 , one part  11 ,  12  may be made more resistant to flammability and one part  11 ,  12  less resistant. For example, the upper portion  101  of the connector  100  shown in the  FIG. 1  ignited when subjected to the “Nichrome Wire Test”. The first portion  11  shown in  FIG. 2 , in an embodiment, is thereby formed of a material offering a higher flammability resistance than that of the second portion  12 . 
     In an embodiment, particularly flammability-resistant materials are used in the first portion  11 . By way of example, without being limited to the particular choice of materials listed here, the first portion  11  may include at least one of the following compositions: polyamide with 30% glass fiber, polybutylene terephthalate with 30% glass fiber, polyethylene terephthalate and polyphenyl sulfide, which is a liquid crystal polymer, or another type of polymer that is by nature self-extinguishing. 
     In various embodiments, the second portion  12  may be made of polyamide, polyolefin or polybutylene terephthalate. 
     The geometrical characteristics of the first and second portions  11  and  12  that enable coupling between these portions will be described in greater detail below with reference to  FIGS. 3 and 4 .  FIG. 3  shows the first portion  11  which, in an embodiment, is made of a material that offers higher flammability resistance than the flammability resistance of the second portion  12 . 
     As shown in  FIG. 3 , the first portion  11  has a female coupling system in a lower part that can connect the first portion  11  to the second portion  12  mechanically. The coupling system includes a plurality of contact surfaces  112  against which projections on the second portion  12 , which will be described later, can be secured. Although not shown in the figure because they are hidden inside the first portion  11 , as will be clearer from the remainder of this description, additional contact surfaces  112  on the first portion  11  are located in different planes in order to provide an effective mechanical fixing between the first portion  11  and the second portion  12 . 
     In another embodiment, the first portion  11  may include a female coupling system comprising one or more engaging holes that allow one or more end portions of the second portion  12  to be inserted into these holes, so that the first portion  11  can be mechanically fixed to the second portion  12 . It is clear that these holes, located for example on the inner or outer side walls of the first portion  11 , can be used in combination or alternatively with the contact surfaces  112 . The term side surfaces refers to all those surfaces perpendicular to the front surface (front view in  FIG. 3 ) and extending along the coupling direction between the first portion  11  and the second portion  12 . 
     As shown in  FIG. 3 , the first portion  11  includes a pair of grooves  199  which are configured to accommodate a pair of external coupling elements  123  shown in  FIG. 4 . 
     As shown in  FIG. 4 , the second portion  12  includes a male coupling system including a plurality of projecting elements  121 - 122  extending from the main body of the second portion  12  along a direction in which the second portion  12  is mechanically coupled to the first portion  11 . These projecting elements  121 - 122  therefore enable the second portion  12  to be mechanically coupled to the female coupling system of the first portion  11 . The second portion  12  includes a pair of second projecting elements  124  and  125 . 
     As shown in  FIG. 4 , the plurality of projecting elements  121 - 122  extend perpendicularly from the main body of the second portion  12  and each have a catch  121   a - 122   a,  also referred to as a projection  121   a - 122   a,  configured so as to contact the contact surfaces  112  of the female coupling system of the first portion  11 . The projecting elements  121 - 122  are able to be deformed in a direction perpendicular to the direction of extension of the projecting elements  121 - 122  so that the catches  121   a - 122   a  can contact the contact surfaces  112  of the first portion  11 . 
     During the coupling operation, the catches  121   a - 122   a  will contact the surface of the first portion  11 , causing the projecting elements  121 - 122  to flex, resiliently deforming, and then return to their perpendicular positions once the catches  121   a - 122   a  contact the contact surfaces  112 , substantially providing a kind of snap-fastening system. The projecting elements  121 - 122  are thus able to block relative movement between the first portion  11  and the second portion  12  by their terminal portions including the catches  121   a - 122   a.  Therefore, when finally positioned between the first portion  11  and the second portion  12 , the projections  121   a - 122   a  will be correctly positioned at a predetermined position along the contact surfaces  112 . 
     It is clear that, in other embodiments, the number of projecting elements  121 - 122  can be varied as desired, depending on requirements. The projecting elements  121 - 122  may also be positioned in different planes in order to ensure better mechanical coupling. 
     Although the present invention has been described with reference to the embodiments described above, it will be clear to those skilled in the art that it is possible to make various modifications, variations and improvements to the present invention in the light of the teaching described above and within the scope of the appended claims without departing from the subject-matter and scope of protection of the invention. 
     For example, although it has been shown that the first portion  11  has a female coupling system and the second portion  12  has a male coupling system, it is possible to make the coupling system in the opposite way, i.e. with the first portion  11  having a male coupling system and the second portion  12  having a female coupling system. 
     For example, although a particular mechanical connection between the first portion  11  and the second portion  12  has been described, it is clear that this mechanical connection is not limited to the particular embodiment described in the figure, but can be any mechanical connection known to those skilled in the art. 
     Finally, it is clear that the example shown in the figures describes a multiple connector configured to allow coupling to four cables (thus having four interconnecting lines), but it is possible to apply the invention to larger or smaller connectors having more or fewer interconnecting lines. Similarly, if the connector is larger or smaller than those shown in the figures, it may have a number of projections on the second portion which is greater or smaller than that described in the figures. 
     In addition it is clear that, although it has been shown that the connector  10  is made by mechanical coupling between two elements (the first and second portions  11 ,  12 ), the connector  10  can also comprise more than two elements having different flammability-resistance characteristics. 
     The present invention is based on the discovery that the thermal stresses to which a connector  10  is subjected are not uniform, and therefore some portions of the connector  10  must withstand higher loads while other portions are subject to lower loads. Instead of making the entire connector  10  from extremely expensive and high-temperature-resistant material, it will be possible to limit this to the only portion where high thermal stress is expected, thus reducing the cost of the connector  10 . Thanks to mechanical engagement between the first portion  11  and the second portion  12 , it will therefore be possible to easily mechanically connect the two portions  11 ,  12 , providing a connector  10  which is geometrically identical to one having a uniform body (as known in the prior art), but which has different properties. The connector  10  has high flammability resistance and is therefore able to pass the various tests required to meet current safety parameters.