SEALING JOINTS FOR ELECTRICAL CONNECTORS

FIELD OF THE INVENTION

The invention relates to grommet-type sealing joints for electrical connectors, and to electrical connectors which are sealed by means of such joints.

BACKGROUND OF THE INVENTION

In automotive applications, electrical connectors comprising a sealing joint are used. Grommet-type sealing joints commonly used in the art are integrally made of an elastomeric material, to efficiently protect electrical connection members at least from humidity and dust. An example of a grommet-type sealing joint 1 of the prior art is shown on Fig. 17. At least one electrical connection member (not shown) is to be inserted through a hole of the grid 7 and a corresponding hole 2 of the sealing joint 1. A connection member, or terminal member, typically comprises a metallic contact portion for connecting to a mating electrical connection element or circuit, and an opposite cable.

Such electrical connectors are submitted to extensive testing to make sure that, during assembly, upon insertion of a connection member through the joint, the mechanical integrity of the latter is not impaired, which would be detrimental to the sealing ability of the whole seal. Similar tests occur to evaluate the ability of the joint to withstand extraction of a connection member from the sealing joint, for example for replacement of the connection member.

Commonly used grommet-type joints have an insertion face and an extraction face opposite said insertion face, and at least one passageway formed by a hole extending therebetween. The passageway is for

receiving an electrical connection member extending therethrough in an assembled condition of the electrical connector. The passageway includes at least one sealing lip which has to surround the connector with elastic fit in order to provide a proper sealing of the joint.

Grommet-type joints of a particular kind are known in which each passageway is closed by a pierceable membrane which is provided in the passageway and extends perpendicularly to the axis of the hole, each membrane having a peripheral edge connected to a wall of the hole. As in most connectors not all the passageways are meant to be crossed by a terminal member, these membranes avoid the need for separate plugs to seal those of the passageways which are unused. The membranes remain not pierced in the unused passageways, thus avoiding the sealing of the joint to be impaired.

However, in such grommet-type joints provided with sealing membranes, the piercing of the membranes has to create a continuous tear to prevent fragments of the membranes from detaching. Indeed, most electrical connecting members have sharp edges which may cut a membrane in several zones and detach fragments which infiltrate some cavities of the connector housing where they may hinder the contact of the metallic contact portion of an electrical connector. A grommet-type joint comprising neatly pierceable membranes is described in EP 0 625 807 (see its Fig. 5), which has preferential opening portion (38) defined by a weaker cross-shaped portion .

SUMMARY OF THE INVENTION

It is an object of the invention to improve the ability of the pierced membranes to allow the insertion and/or the extraction of an electrical connector without

generating fragments, while having membranes able to withstand sealing tests typically in pressurized atmosphere, i.e. the membranes of the unused passageways shall not be torn. Accordingly, the invention provides a grommet- type joint of the above-defined type, in which the membrane comprises at least one thick portion as well as a preferential opening portion created by a local reduction of the membrane thickness, wherein said preferential opening portion presents at least two ends which are located in the vicinity of the peripheral edge of the membrane, and wherein the smallest value of the membrane thickness in the preferential opening portion is lower than or equal to 70% of the smallest value of the membrane thickness in at least one thick portion.

By this way, a membrane tear upon insertion of an electrical connector extends along a continuous line large enough to create a relatively extended free edge at a border of each thick portion, allowing a sufficient flexible displacement for each thick portion in order to allow the electrical connector to cross the membrane without excessive insertion strength to provide. With these features, the risk that the tear of the membrane propagates out of the preferential opening portion and/or generates fragments is very low.

Preferably, the smallest value of the membrane thickness in the preferential opening portion is comprised between 20% and 50% of the smallest value of the membrane thickness in at least one thick portion. This feature further ensures that the tear does not propagate out of the preferential opening portion.

In another aspect of the invention, each one of the at least two ends of the preferential opening portion which are located in the vicinity of the peripheral edge

of the membrane is connected to the wall of the hole by a part of gradually increased thickness. This feature ensures that the tear stops at each end of the preferential opening portion and therefore does not propagate beyond the wall into the body of the joint.

In the following description, a plane which is perpendicular to the axis of a hole formed in the body of the joint is named "a horizontal plane".

Fig. 1 is a cross-sectional view of a substantially flat membrane for a grommet joint of the invention, in a horizontal plane positioned in the depth of the membrane.

Fig. IA is a cross-sectional view of the membrane of Fig. 1, in the mid-plane IV-IV drawn in Fig. 1 passing by the axis A of the hole.

Fig. IB is a cross-sectional view of the membrane of Fig. 1, in the mid-plane V-V drawn in Fig. 1 passing by the axis A of the hole.

Fig. 2 is a cross-sectional view of a substantially flat membrane having a different shape of preferential opening portion for a grommet joint of the invention, in a horizontal plane positioned in the depth of the membrane.

Fig. 2A is a cross-sectional view of the membrane of Fig. 2, in the mid-plane IV- IV drawn in Fig. 2 passing by the axis A of the hole.

Fig. 2B is a cross-sectional view of the membrane of Fig. 2, in the mid-plane V-V drawn in Fig. 2 passing by the axis A of the hole. Fig. 3 is a cross-sectional view of a substantially flat membrane having a different shape of preferential opening portion for a grommet joint of the invention, in a horizontal plane positioned in the depth of the membrane.

Fig. 3A is a cross-sectional view of the membrane of Fig. 3, in the mid-plane IV- IV drawn in Fig. 2 passing by the axis A of the hole.

Fig. 3B is a cross-sectional view of the membrane of Fig. 3, in the mid-plane V-V drawn in Fig. 2 passing by the axis A of the hole.

Fig. 4 is a cross-sectional view of an embodiment presenting an alternative shape for the junction zone of the membrane of Fig. 1, in the mid-plane V-V drawn in Fig. 1 passing by the axis A of the hole.

Fig. 5 is a cross-sectional view of another embodiment presenting an alternative shape for the junction zone of the membrane of Fig. 1, in the mid-plane V-V drawn in Fig. 1 passing by the axis A of the hole. Fig. 6 is a cross-sectional perspective view of a membrane having another shape for a grommet joint of the invention, from a mid-plane passing by the axis of the hole.

Fig. 6A is a cross-sectional view of the membrane of Fig. 6, in the mid-plane of Fig. 6.

Fig. 7 is a cross-sectional perspective view of a membrane having another shape for a grommet joint of the invention, from a mid-plane passing by the axis of the hole. Fig. 7A is a cross-sectional view of the membrane of Fig. 7, in the mid-plane of Fig. 7.

Fig. 8 is a cross-sectional perspective view of a membrane having another shape for a grommet joint of the invention, from a mid-plane passing by the axis of the hole.

Fig. 8A is a cross-sectional view of the membrane of Fig. 8, in the mid-plane of Fig. 8.

Fig. 9 is a cross-sectional view of a membrane having another shape for a grommet joint of the

invention, in a mid-plane passing by the axis of the hole and perpendicular to the direction of the preferential opening portion.

Fig. 10 is a cross-sectional view of a membrane having a shape similar to the shape in Fig. 9, except that it exhibits a narrower preferential opening portion.

Fig. 11 is a cross-sectional perspective view of a membrane having another shape for a grommet joint of the invention, from a mid-plane passing by the axis of the hole.

Fig. HA is a cross-sectional view of the membrane of Fig. 11, in the mid-plane of Fig. 11.

Fig. 12 is a cross-sectional perspective view of a membrane having another shape for a grommet joint of the invention, from a mid-plane passing by the axis of the hole.

Fig. 12A is a cross-sectional view of the membrane of Fig. 12, in the mid-plane of Fig. 12.

Figs. 13 to 15 are respective cross-sectional views of three membranes having other shapes for a grommet joint of the invention, in a mid-plane passing by the axis of the hole and perpendicular to the direction of the preferential opening portion.

Fig. 16 is a detail of a preferential opening portion of a membrane for a grommet joint of the invention, showing a part of gradually increased thickness which prevents the propagation of a tear from going out of the preferential opening portion.

Fig. 17 is a perspective view of an known electrical connector including a grommet-type sealing joint .

A conventional electrical connector 5 shown on Figure 17 comprises a grommet-type sealing joint 1 which consists of an elastomer body. The present invention may

be implemented into the membranes which close the holes of the elastomer body.

The sealing joint 1 is made of a single elastomer material. However, the membrane could also be made of a flexible material which is different from the elastomer material of the body. The joint is to be arranged in the rear skirt 3 of the connector housing 6, and held in place by a grid 7 which bears on the joint rear side. Terminal members are to be introduced through the holes of the grid 7 to cross the holes 2 of the sealing joint 1 until there are inserted in the corresponding cavities 4 in the connector housing 6 to establish an electrical contact with mating connection elements.

The invention avoids the risk that the membranes generate fragments upon tearing, which would migrate into the cavities 4, that would insert between mating terminals and that would prevent from a good electric connection.

In a first embodiment shown on Figures 1, IA and IB, a substantially flat membrane 10 closes a passageway formed by a hole 2 in the body of the sealing joint 1. The membrane 10 comprises a single thick portion 11 which substantially has the shape of a disk and which is centred on the axis A of the hole 2 which has a tubular shape in the vicinity of the membrane. The edge of the top surface of the thick portion 11, i.e. of the surface directed towards the insertion face of the joint, is delimited by an open-ring groove 13 which defines the preferential opening portion 12. The open-ring groove 13 is defined by an annular groove which does not make a complete turn, and follows an arc of circle centred on the axis A in the vicinity of the wall 20 of the hole 2.

Preferably, the open-ring groove 13 is obtained by molding the membrane 10.

The thick portion 11 comprises a junction zone

HA by which it is connected to the wall 20. The junction zone HA corresponds to the part of the thick portion 11 which extends between the two ends of the open-ring groove 13. Each portion 11 or 12 of the membrane 10 is symmetrical with respect to a mid-plane V-V passing by the axis A and which is defined as the plane of symmetry for the open-ring groove 13.

The angular extent α of the junction zone HA is lower than or equal to 45°, and preferably comprised between 15 and 35 degrees. The angle α is defined as the angle between two lines which are respectively drawn between the centre of the membrane and the two ends of the open-ring groove 13.

The membrane thickness in the preferential opening portion 20 is uniform, and the thickness value θ is lower than or equal to 70% of the smallest value g of the membrane thickness in the thick portion 11. This ensures that the tear of the membrane upon introduction of a terminal member always occurs in the preferential opening portion 12.

Preferably, the smallest value θ of the membrane thickness in the preferential opening portion 12 is comprised between 20% and 50% of the smallest value g of the membrane thickness in the thick portion 11.

The membrane thickness in the thick portion 11 is uniform, and the junction zone HA has the same thickness g as the main part of the thick portion H.

As shown on Figures 2, 2A and 2B, another embodiment of a substantially flat membrane for a sealing joint of the invention comprises two thick portions H each having substantially the shape of the letter T which

are symmetrical with respect to a mid-plane IV- IV passing by the axis A of the hole 2 which has a tubular shape in the vicinity of the membrane. The preferential opening portion 12 comprises a zone which extends along a centre- line 9 passing by the axis A and contained in the mid- plane IV-IV.

Each portion 11 or 12 of the membrane 10 is also symmetrical with respect to a second mid-plane V-V passing by the axis A perpendicularly to the first mid- plane IV- IV. Each one of the two thick portions 11 comprises a junction zone HA by which it is connected to a wall 20 of the hole 2. The angular extent α of each junction zone HA is lower than or equal to 45°, and is preferably comprised between 15° and 35°. As can be seen on Figures 2 and 2A, the preferential opening portion 12 extends over the length of the diameter of the hole 2 in the direction of the centre-line 9.

As shown on Figures 3, 3A and 3B, another embodiment of a membrane for a sealing joint of the invention comprises four thick portions 11 and one preferential opening portion 12 which has the shape of the letter H. Like in the embodiment shown on Figure 2, the mid-planes IV- IV and V-V are planes of symmetry for the membrane. Two thick portions 11, each of which having a substantially rectangular shape, are symmetrical with respect to the first mid-plane IV- IV, and each one has a junction zone HA which presents an angular extent a lower than or equal to 45°. Like in the previous embodiments shown on

Figures 1 and 2, the top and bottom surfaces of each thick portion 11 are flat and parallel to a horizontal plane, therefore providing a constant thickness g for the thick portions 11.

The other embodiment shown on Figure 4 differs from the embodiment of Figure 1 in that the junction zone

HA presents a reinforcement thickness 110 which consists of a gradual increase of the thickness of the membrane up to the connection with the wall 20.

The other embodiment shown on Figure 5 differs from the embodiment of Figure 1 in that the grove 13 which is provided in the top surface of the membrane and which delimits most of the thick portion 11 makes a full circle.

The bottom side of the membrane is not flat on its whole surface, as the junction zone HA consists of a local reinforcement thickness provided on the bottom surface. The junction zone HA is not as thick as the one of Figure 1, and has the smallest thickness value g of the membrane in the thick portion 11. The thickness of the membrane in the preferential opening portion 12 is uniform and its value θ may reach up to 70% of the thickness value g of the junction zone HA. The other embodiment of a membrane shown on

Figures 6 and 6A comprises two thick portions 11 which are symmetrical with respect to the mid-plane 8 passing by the centre-line 9 along which the preferential opening portion 12 extends. Both thick portions 11 of the membrane extend between the preferential opening portion 12 and the wall 20 of the hole along a tilted direction forming an angle β with a horizontal plane.

The thickness g of the membrane in both thick portions 11 is substantially uniform, and the two opposite surfaces Sl and S2 of the thick portion 11 are substantially plane and parallel to each other. In the same manner, the thickness in the preferential opening portion 12 has substantially a constant value θ, and the surfaces Sl and S2 of this portion 12 are substantially

parallel to a horizontal plane. In any area of the membrane, the two respective surfaces Sl and S2 on the two opposite sides of the membrane extend while being parallel to the centre-line 9, i.e. at any point of a surface Sl or S2 a line can be drawn which is contained in said surface and is parallel to the centre-line 9.

The preferential opening portion 12 essentially consists of a band, the thickness θ and width I of which are substantially constant. In another embodiment of a membrane shown on

Figures 7 and 7A, the two thick portions 11 are not symmetrical with respect to the mid-plane passing by the centre-line 9. A first thick portion 11, which is located on the right side of the drawing, extends substantially in the direction of a horizontal plane, whereas the second thick portion 11 extends substantially along a tilted direction with respect to the horizontal plane.

The first thick portion presents a first plane surface 16 which extends in a same common horizontal plane into a first surface of the preferential opening portion 12. This horizontal plane intersects a plane defined by the top surface Sl of the second thick portion along a line 19 parallel to the centre-line 9. In other words, the top surface Sl of the membrane is defined by two plane surfaces which intersect in the line 19, one of these plane surfaces being defined by the top surface Sl of the second thick portion which is tilted by an angle β with respect to a horizontal plane.

On the bottom side of the membrane, the first thick portion presents a second plane surface 17 which joins the preferential opening portion 12 by forming a shoulder HB. The preferential opening portion 12 presents the smallest thickness θ in the area where it forms the shoulder Hb with the first thick portion. The

preferential opening portion 12 comprises a part 12A in which the membrane thickness increases gradually while going towards the second thick portion. It also comprises a band located between the shoulder HB and the line 19, the thickness θ and width I of which are substantially constant .

In another embodiment of a membrane shown on Figures 8 and 8A, most of the structure of the membrane is similar to the embodiment of the membrane shown on Figures 7 and 7a. The only differences bear on the cross- section and shape of the preferential opening portion 12. The preferential opening portion 12 only consists of a part 12A in which the membrane thickness increases gradually while going towards the second thick portion, i.e. towards the thick portion 11 which is tilted with respect to a horizontal plane.

The region of the preferential opening portion

12 which presents the smallest thickness value θ consists basically in the end of the part 12A which joins the second plane surface 17 of the first thick portion by forming the shoulder HB.

Alternatively, the preferential opening portion

12 could include a band of constant thickness and width, like the one shown on Figure 7, between the part 12A and the first thick portion located on the right of the drawing.

In two other embodiments of membranes shown respectively on Figures 9 and 10, both thick portions 11 present a same thickness g and extend in a horizontal plane.

In the embodiment shown on Figure 9, the preferential opening portion 12 includes a band of constant thickness and width and a part 12A which has a substantially constant width p and a gradually increasing

thickness .

In the embodiment shown on Figure 10, the preferential opening portion 12 does not include such a band of constant thickness, and only consists of a part 12A which has substantially constant width p and a gradually increasing thickness.

For both embodiments shown on Figures 9 and 10 respectively, either one or both of the top and bottom surfaces respectively Sl and S2 of the membrane in a thick portion 11 may be tilted with respect to a horizontal plane.

In the two embodiments of a membrane shown respectively on Figures 8 and 10, the tear of the membrane is likely to initiate at a point in the region of the preferential opening portion 12 which presents the smallest thickness value θ. In other words, the region where the tear of the membrane is the most likely to initiate consists in the thinnest end of the part 12A of gradually increased thickness. In another embodiment of a membrane shown on

Figures 11 and HA, the surface S2 of the bottom face of the membrane has the shape of a bell in a sectional view perpendicular to the centre-line 9. The top of the bell is directed towards the side of the sealing joint by which the terminal members are inserted. The surface Sl of the top face of the membrane presents a substantially flat top portion 14 extending along a horizontal plane. This flat top portion 14 intersects the top surfaces of the thick portions 11 in edge-lines 19 which are parallel to the centre-line 9.

The membrane is symmetrical with respect to the mid-plane passing by the centre-line 9. As shown on Figure HA, each thick portion 11 has a thickness the value of which increases gradually from the centre to the

wall of the hole.

The lowest value g of the thickness is measured in the vicinity of a edge-line 19. The lowest value θ of the preferential opening portion 12 is measured in the mid-plane region, i.e. the region of the membrane which is crossed by the mid-plane. The crack which initiates the tear of the membrane is likely to occur on the bottom surface of the portion 12 approximately in the mid-plane region . In another embodiment of a membrane shown on

Figure 12, the bottom surface of the membrane also has the shape of a bell in cross-sectional view. The preferential opening portion 12 consists of a band, the thickness θ and width I of which are substantially constant. The top surface of the membrane presents a top which has the shape of a channel extending along the centre-line 9 and which is bordered by two ribs 15.

The two ribs 15 provide a greater arcuate transverse deformation of the membrane in the band of the preferential opening portion 12 upon insertion of a terminal member, therefore increasing the ability of the membrane to be torn by the deformation of its portion 12. As the membrane becomes increasingly deformed while remaining substantially symmetrical with respect to the mid-plane passing by the centre-line 9, the crack which initiates the tear is likely to occur on the bottom surface of the portion 12 approximately in the mid-plane region .

In another embodiment of a membrane shown on Figure 13, the membrane is symmetrical with respect to a mid-plane passing by a centre-line and by the axis of the hole. The preferential opening portion 12 consists of a band, the thickness θ and width I of which are substantially constant.

The thickness g of each thick portion 11 is substantially constant, as the bottom and top surfaces of each thick portion are substantially plane and parallel to each other. Each thick portion 11 is tilted of an angle β with respect to a horizontal plane, and forms a shoulder HB on its bottom surface in the area where it joins the band of the preferential opening portion 12.

In two other embodiments of membranes shown respectively on Figures 14 and 15, the preferential opening portion 12 substantially extends along a mid- plane passing by the axis A of the hole, and consists of a band which has a constant thickness θ and presents a relatively narrow width. The membrane comprises two thick portions 11 located on both sides of the mid-plane and which are axially shifted from each other along the axis of the hole.

In each thick portion 11, either a top or a bottom surface Sl or S2 extends along a plane which is tilted of an angle β with respect to the horizontal plane. In the embodiment shown on Figure 14, the other top or bottom surface of each thick portion 11 extends along a horizontal plane. The membrane thickness in said portion 11 gradually increases while from the centre to the wall of the hole, and its smallest value g is measured in the vicinity of the mid-plane.

In the embodiment shown on Figure 15, the top and bottom surfaces of each thick portion 11 are substantially parallel to each other. Therefore, the membrane thickness g in said portion 11 is substantially constant. The top and bottom surfaces extend along a plane which is tilted of an angle β with respect to the horizontal plane. The preferential opening portion 12 substantially extends along a mid-plane passing by the axis A of the hole, and consists of a band which has a

constant thickness and presents a relatively narrow width, as for the membrane of the Figure 14.

According to another aspect of the invention, the detail shown on Figure 16 represents an improvement which can be implemented into any membrane in a sealing joint of the invention. The connection between a preferential opening portion 12 and the wall 20 of the hole is made by providing a part 21 of gradually increased thickness in a direction towards the wall. The propagation of the tear in the preferential opening portion 12 is very likely to stop in the part 21, at an end crack 22 which extend through the thickness of the membrane. In this part 21, the thickness value tS at the location of the end fissure 22 is substantially greater than the thickness θ of the preferential opening portion 12.

Other shapes can be used for the cross section of the part 21 of gradually increased thickness, for instance a straight line shape could be preferred instead of the curved line shape drawn in Figure 16 for the top surface of said part 21. In any case, the thickness increase is provided so that the tear of the membrane has no risk to propagate beyond the part 21, in the wall.

It must be understood that the embodiments of membranes above described are not limitative and that the features of any embodiment may be combined with some features of another embodiment while obtaining a sealing joint in the scope of the invention.