Abstract:
A mat seal for an electrical connector, including: a front face, a rear face opposite to the front face, and a plurality of passageways each adapted to receive a cable to be inserted through the passageway, at least one cavity in at least one of the front face and the rear face, wherein at least two first passageways of the plurality of passageways open into one of the at least one cavity, and wherein at least one second passageway of the plurality of passageways opening into the front face and the rear face of the mat seal.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention refers to a mat seal for an electrical connector having a front face, a rear face opposite to the front face and a plurality of passageways each adapted to receive a cable to be inserted through said passageway. 
     Background 
     Such a mat seal is, for instance, known from U.S. Pat. No. 6,739,908 B2 disclosing a connector housing including a plurality of terminal receiving chambers, a mat seal mounted to an end surface of the connector housing and a mat seal holder for holding the mat seal wherein the mat seal is disposed between the connector housing and the mat seal holder. The mat seal holder has through holes which are in alignment with the plurality of passageways of the mat seal. Furthermore, the terminal receiving chambers of the connector housing are also aligned with the plurality of passageways of the mat seal. In order to mount terminals into the terminal receiving chambers of the connector housing the terminals first are connected, for example by a crimping process, to a cable and the so connected terminal with cable is inserted through the through holes of the mat seal holder and through the passageways of the mat seal into the terminal receiving chambers of the connector housing. One general object of a waterproof electrical connector is to have a good sealing ability of the mat seal, in particular around the cables which are accommodated within the passageways of the mat seal when the terminals are completely inserted into the terminal receiving chambers of the connector housing. Also it has to be ensured that the insertion force to insert the terminals and the cables through the mat seal is low with a low risk of damaging both the mat seal and the wires, in particular the connection between the cables and the terminals, during the insertion process. 
     Another mat seal is described in WO 2009/075850 A1 disclosing a mat seal having a thick portion and a thin portion. The mat seal is provided with broad passageways within the thick portion and with narrow passageways within the thin portion. This mat seal is, therefore, suitable for electrical connectors accommodating terminals and cables with different sizes. 
     A trend, in particular in the automotive industry, is to push weight and cost reduction for wire harnesses. Car manufactures are focusing to use smaller cables. Smaller cables necessitate mat seals having passageways with smaller diameters in order to guaranty sufficient sealing abilities. However, smaller cross section diameters increase the risk of cables being buckled during insertion through the mat seal. In addition, due to the very small diameters of the cables there is a risk that during the insertion of the terminal and the cables through the mat seal the cables are damaged or torn off from the terminal. 
     Using smaller terminals and smaller cables makes it possible to reduce the distance between adjacent terminals. This may results in difficulties when manufacturing the mat seals. The passageways are typically produced by injection molding tools having cores wherein the cores are forming the passageways through the mat seal. The thinner the passageways have to be formed the thinner the cores have to be. This results in a high risk of the cores being broken during the manufacturing process, for example, during the retraction of the cores out of the molded mat seal. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a mat seal and a molding tool for molding a mat seal avoiding the aforementioned drawbacks. 
     Thus, according to the invention, a mat seal for an electrical connector is provided having a front face, a rear face opposite to the front face, and a plurality of passageways each adapted to receive a cable to be inserted through said passageway. The mat seal further comprises at least one cavity in one of the front face and the rear face wherein at least two first passageways of the plurality of passageways open into one of said at least one cavity. Said plurality of passageways further comprises at least one second passageway opening into the front face and the rear face of the mat seal. The second passageways do not open into a cavity of the front face or the rear face. 
     Accordingly, the mat seal has a cavity in the front face and/or in the rear face so that the first passageways do not have to reach through the entire thickness of the mat seal, i.e. the distance between the front face and the rear face. The first passageways only reach through the mat seal between a ground of one of the cavities and one of the faces of the mat seal or the ground of the cavity in the other face of the mat seal. Hence, the first passageways are shorter in longitudinal direction than the entire thickness of the mat seal. This reduces the friction forces onto the cables while inserting the cables into the first passageways. 
     The first passageways may have a constriction with a circular cross section having a diameter of maximal 0.75 mm, in particular of maximal 0.50 mm. This enables the mat seal to be used for 0.13 sqm wires having an outer diameter of approximately 1 mm. 
     Due to the fact that at least two first passageways open into one cavity the design enables the use of molding tools for manufacturing the mat seal having cores of higher stiffness. There might be one tool element, such as an insert, for forming the cavity and cores for forming the first passageways. The cores for forming the passageways do not have to reach into a molding cavity as deep as if no cavities would be provided, so that the cores have a higher stability against lateral forces. 
     In particular, each first passageway extends along a longitudinal axis and each first passageway has a maximal diameter which is smaller than the minimal radial extension of the cavity. Therefore, it is ensured that no friction force is applied from the mat seal to the cable in the longitudinal region of the cavity. 
     In a preferred embodiment the first passageways open into one cavity in the front face and into one cavity in the rear face. It is also possible that several cavities are formed into the front face and several cavities are formed into the rear face wherein into each of the cavities more than one first passageway opens. 
     Preferably, the minimal diameter of the at least two first passageways is smaller than the minimal diameter of the at least one second passageway. Hence, the mat seal can be used for cables of different diameters. The first passageways accommodates cables with smaller diameter and the second passageways accommodates cables with bigger diameter. 
     In an embodiment of the mat seal the mat seal comprises two or more first passageways and two or more second passageways. The distance between two adjacent first passageways is smaller than the distance between two adjacent second passageways. 
     The invention further refers to a molding tool for injection molding of a mat seal for an electric connector, comprising a first mold with a first cavity and a second mold with a second cavity, wherein said first cavity and said second cavity together form a mold cavity for forming the mat seal. Such molding tools are well known in the prior art. 
     The mold tool further comprises at least one insert with a plurality of receiving chambers, each receiving chamber receives a core reaching into the mold cavity for forming a first passageway through the mat seal. Alternatively, the insert and the cores can be made integrally in one piece. 
     At least one insert projects into the mold cavity for forming a cavity in a face of the mat seal. 
     When adapting the design of a mat seal such that the mat seal can be used for thinner cables the passageways through the mat seal have to be smaller in diameter. Especially, if standard designs of a mat seal shall be used further the thickness of the mat seal does not change. The same occurs if the mat seal shall be used for thin cables and for standard thicker cables as typically used. In order to form passageways for thinner cables through the mat seal very thin cores would have to be used which are fragile in regard to forces in a lateral direction, i.e. in a direction transversely to a longitudinal direction of the cores. 
     In order to increase the stiffness of the cores the inserts are used which have a bigger diameter or a bigger extension in a radial direction. So these inserts are a supports for the cores within the receiving chambers. The cores project out of the receiving chambers into the mold cavity. The length of the projecting portion of the cores is less than it would be if no insert would be used so that the cores have a higher stability against lateral forces without changing the diameter of the cores. 
     According to an embodiment of the molding tool at least one pair of inserts is provided, each pair of inserts comprises a first insert arranged in the first mold and a second insert arrange in the second mold. Each pair of inserts receives at least one pair of said cores, each pair of said cores comprising one first core received in the first insert and one second core received in the second insert. The first core and the second core of each pair of cores abut each other within the mold cavity for commonly forming a first passageway of the mat seal. Therefore, none of the cores reaches through the entire mat seal. Two cores are used to form one mat seal so that the required length of each core reaching into the mold cavity is further reduced. 
     The molding tool may further comprise at least one insertless core reaching into the mold cavity for forming a second passageway through the mat seal wherein the insertless core is received in a receiving chamber of the molding tool. The insertless cores are not received in a receiving chamber of an insert. The insertless cores are used to form second passageways typically of a greater diameter than the first passageways. 
     Hence, the minimal diameter of said cores received in said at least one insert is smaller than the minimal diameter of said at least one insertless core. 
     In order to increase the packaging of the passageways the molding tool may comprise two or more cores received in said at least one insert and two or more insertless cores. The distance between two adjacent cores received in said at least one insert is smaller than the distance between two adjacent insertless cores. 
     Each of said cores has a projecting portion projecting out of the respective receiving chamber into the mold cavity. 
     The projecting portion of said cores received in said at least one insert have a restriction with a circular cross section having a diameter of maximal 0.75 mm, in particular of maximal 0.50 mm. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A preferred embodiment is described, by way of example, in the following description and the accompanying drawings. 
         FIG. 1  is a perspective view of a mat seal; 
         FIG. 2  is a sectional view along the section line II-II according to  FIG. 1 ; 
         FIG. 3  is a perspective longitudinal sectional view of a molding tool for molding a mat seal; 
         FIG. 4  is an enlarged view of the molding cavity of the molding tool according to  FIG. 3 ; 
         FIG. 5  is a perspective view of an insert for a molding tool according to  FIG. 3  and 
         FIG. 6  is a perspective view of a core inserted into the insert according to  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  show a mat seal in different views and are described together. 
     The mat seal  1  has a front face  2  and a rear face  3  wherein the front face  2  and the rear face  3  are arranged parallel to each other. The thickness of the mat seal  1  is defined by the distance between the front face  2  and the rear face  3 . The mat seal has a circumference with three sealing beads  11 . The mat seal  1  is designed for being held between a housing of a connector and a mat seal holder. The front face  2  is intended to be in contact with the housing of the connector and the rear face  3  is intended to be in contact to the mat seal holder. The sealing beads  11  are held in sealing contact to the housing or the mat seal holder. 
     The mat seal  1  is penetrated by a plurality of first passageways  4  and second passageways  5 . The passageways  4 ,  5  are orientated along respective longitudinal axes L, L′ wherein all longitudinal axes L, L′ of all passageways  4 ,  5  are arranged parallel to each other and perpendicular to the front face  2  and the rear face  3 . 
     In the following, two first passageways  4 ,  4 ′ are described representing all first passageways  4 ,  4 ′. The first passageways  4 ,  4 ′ open into one common cavity  6  in the front face  2  and into one common cavity  7  in the rear face  3 . The first passageways  4 ,  4 ′, hence, have a shorter length in longitudinal direction than the thickness of the mat seal  1 . In other words, the distance between the front face  2  and the rear face  3  is bigger than the length of the first passageways  4 ,  4 ′. The first passageways  4 ,  4 ′ reach from a ground  8  of the cavity  6  of the front face  2  to a ground  9  of the cavity  7  of the rear face  3 . 
     Further, the cavities  6 ,  7  do have a greater extend lateral to the longitudinal axes L, L′ than the first passageways  4 ,  4 ′. The greatest diameter of the first passageways  4 ,  4 ′ is smaller than the smallest lateral extension of the cavities  6 ,  7  perpendicular to the longitudinal axes L, L′. Thus, when a terminal with a connected cable is pushed through one of the first passageways  4 ,  4 ′ neither the terminal nor the cable comes into contact with the mat seal  1  in the region of the cavities  6 ,  7 . Further, the length of the first passageways  4 ,  4 ′ is less than the thickness of the mat seal  1 . Both provides for a reduced friction force which acts from the mat seal  1  to the terminal or the cable. 
     Compared to this, the second passageways  5  do not open into a cavity but directly into the front face  2  and the rear face  3  so that the friction forces are higher than the friction forces within the first passageways  4 . In addition, the minimal diameter of the first passageways  4  is smaller than the minimal diameter of the second passageways  5  so that the second passageways  5  are suitable for bigger cables than the first passageways  4 . 
       FIGS. 3 and 4  depict a molding tool for molding a mat seal according to  FIGS. 1 and 2 . The molding tool comprises a first mold  12  and a second mold  13 . The first mold is a combination of a first mold module  14  and a second mold module  15  together forming a first cavity  16 . The second mold  13  forms a second cavity  17 . The first cavity  16  and the second cavity  17  together form a mold cavity  18  in the form of the mat seal according to  FIGS. 1 and 2 . The mat seal  1  is also shown in  FIG. 3 . In  FIG. 4  the mold cavity  18  is shown without mat seal. The first mold  12  and the second mold  13  can be opened and closed. In  FIGS. 3 and 4  the molds  12 ,  13  are shown in the closed position. For opening the molds  12 ,  13  are moved apart from each other parallel to the longitudinal axes L, L′. 
     The first mold  12  further comprises several first inserts  19 , one of which is described representing all first inserts  19 . The second mold  13  comprises several second inserts  20 , one of which is described representing the other second inserts. 
     The first insert  19  and the second insert  20  each have an insert head  29 ,  30 , which can also be seen in  FIG. 5 , showing the first insert  19 . The insert heads  29 ,  30  project into the mold cavity  18  for forming the cavities in the front face  2  and the rear face  3  respectively of the mat seal according to  FIGS. 1 and 2 . 
     The first insert  19  has receiving chambers  21  extending along the longitudinal axis L for forming the first passageways  4 . The receiving chambers  21  receive first cores  22 , one of which is shown in  FIG. 3 . In the same manner the second insert  20  has receiving chambers  23  receiving second cores  24 . The first cores  22  and the second cores  24  each have a projecting portion  31 ,  32  aligned to the longitudinal axis L and projecting out of their respective receiving chamber  21 ,  23  for forming the first passageways  4 . For forming each of the first passageways for a pair of inserts, i.e. the one first insert  19  and one second insert  20  are provided. Further, a pair of receiving chambers  21 ,  23  are provided, one receiving chamber  21  in the first insert  19  and one receiving chamber  23  in the second insert  20 , wherein the receiving chambers  21 ,  23  of the pair of receiving chambers are aligned along one longitudinal axis L. The receiving chambers  21 ,  23  receive cores, i.e. a first core  22  in the receiving chamber  21  of the first insert  19  and a second core  24  in the receiving chamber  23  of the second insert  20 . Within the mold cavity  18  the first core  22  and the second core  24  abut each other. 
     For forming the second passageways  5  the first mold  12 , namely the second mold module  15 , and the second mold  13  are provided with receiving chambers  25 ,  27  wherein the receiving chambers  25 ,  27  are directly provided within the first mold  12  and the second mold  13  respectively without any inserts. The receiving chambers  25 ,  27  receive cores  26 ,  28 , each having a projecting portion  33 ,  34  which project out of their respective receiving chamber  25 ,  27  into the mold cavity  18 . A pair of cores  26 ,  28  are aligned along a longitudinal axis and abut each other within the mold cavity  18  in order to form a second passageway  5  of the mat seal  1 . 
     Especially, as can be seen from  FIG. 4 , the projecting portions  31 ,  32  of the cores  22 ,  24  for forming the first passageway  4  are shorter and project over a smaller distance into the mold cavity  18  as the projecting portions  33 ,  34  of the cores  26 ,  28  forming the second passageways  5 . The cores  22 ,  24  for forming the first passageways  4  are supported in a radial direction by the inserts  19 ,  20  so that these cores  22 ,  24  have a increased radial stability. Therefore, the cores  22 ,  24  can have a smaller diameter than the cores  26 ,  28  for forming the second passageways  5 .