INFILTRATION

The present invention refers to an assembly with a cap, co-molded on an eyelet metallic terminal, for the protection against infiltration of liquids in a connection of electric cables with a branch node.

This solution was specially developed for the electric cables of hybrid vehicles. The electrical cables that connect to the batteries of a hybrid vehicle typically have a section of 50 mm , having to conduct very intense currents. These electric cables, fitted with caps, must be able to be placed under the car floor mat. For this reason, the overall dimensions must be limited as much as possible in height.

This terminal is connected to a junction node, placed under the floor of the car itself. The node has its own structure and is equipped with its own sealing gaskets. From the upper part of the floor, in correspondence with said junction node, both part of the plastic body that constitutes the structure of the node itself, and a threaded pin that allows the locking of the eyelet terminal, incorporated in the cap itself, by means of a self locking nut.

Purpose of the cap is electrically isolating the junction and preventing any liquid from entering the junction, to avoid short circuits and/or oxidation.

The co-molded cap is so defined because the end of the cable, equipped with said metal eyelet terminal crimped to the cable itself, is inserted into the mold of an injection molding machine and coated with a thermoplastic rubber which forms the cap itself.

Therefore the cap in question is an element, made of thermoplastic rubber that completely wraps the end of the cable, leaving the eyelet of the terminal free so that said threaded pin can be inserted in said eyelet which allows the terminal itself to be fixed by means of a self-locking nut. The upper part of the cap, which is open to allow the insertion of the self-locking nut and the key with which to tighten, is subsequently closed by inserting a cap, said cap being obtained from the cap itself upon injection molding.

Once said cable is mounted on the threaded pin, the possible critical points from which water can enter are the following:

- sheet side area, i.e. the lower part of the cap that comes into contact with the floor sheet, where infiltrations between the cap and the sheet itself could occur; - closing cap area on the self-locking nut, where infiltrations could occur between the outer edges of the cap itself and the seat where it is inserted;

- cable side area, in which infiltrations could occur between the cable itself and the co molded cap, said criticality being due to the fact that the material of the cap is not compatible with the material of the insulation with which the cable is coated, so it does not occur the welding between the two materials in contact.

As for the area on the sheet metal side, it should be emphasized that the sheet metal of a car floor has a thickness of only 0.8 mm, so it can undergo slight deformations when the terminal is locked to the junction node located under the car floor and this fact obviously introduces a new criticality with regard to sealing.

US-A1-2016/294107, JP-A-H11 167911, CN-U-202

167 732 e CN-Y-201 069 796 disclose caps according to the preamble of Claim 1.

Object of the present invention is solving the above prior art problems by providing means suitable for protecting a connection of electric cables from infiltration of liquids. The above and other objects and advantages of the invention, which will appear from the following description, are achieved with a group with a co molded cap with a metal terminal in accordance with claim 1. Said assembly comprises a cap co-molded on a metal terminal connected to a conducting metal element by tightening a nut which is screwed onto a threaded pin integral with said conducting metal element, in which said conducting metal element is part of a junction node located on one side of a sheet metal while said metal terminal is positioned on the opposite side of said sheet, and is characterized in that it is made of thermoplastic rubber and comprises: a main body which has a central through hole, through which said threaded pin is inserted on which said nut is screwed, said main body coming into contact with said sheet, first means being provided for ensuring the seal against liquids between said body main and said sheet;

- a cap, connected by means of a flexible strap to said main body of the cap, said cap being able to fit into a circular seat obtained on the upper part of the main body of the cap, second means being provided for ensuring the seal against liquids between said body principal and called little cap;

- a sleeve that covers the end of said cable, third means being provided to ensure liquid tightness between said main body and said electrical cable.

Preferred embodiments and non-trivial variants of the present invention form the subject of the dependent claims. It is understood that all the attached claims form an integral part of the present description.

It will be immediately obvious that innumerable variations and modifications (for example relating to shape, dimensions, arrangements and parts with equivalent functionality) can be made to what has been described without departing from the scope of the invention as appears from the attached claims.

The present invention will be better described by some preferred embodiments, provided by way of non-limiting example, with reference to the attached drawings, in which:

- FIG. 1 (a, b) show an embodiment example of the terminal according to the present invention; - FIG. 2 shows the assembly of the terminal according to the invention;

- FIG. 3 shows the way in which the seal is carried out with the floor of the car;

- FIG. 4 shows the way in which the sealing is effected in the upper part of the cap.

Referring to FIGS. 1 and 2, (1) designates a terminal of an electric cable (2). Said terminal (1) includes a metal eyelet (3) and is covered with a co-molded cap (4), according to the invention. Said eyelet (3) is crimped on the end of the electric cable (2), having removed the covering of the cable (2) itself, in order to allow the metal contact.

In particular, FIG. la shows the electric cable (2), metal terminal with eyelet (3) and cap (4), as it is extracted from the injection molding machine, while in FIG. lb said electric cable (2), equipped with said metal terminal with eyelet (3), and said cap (4) are shown separately. According to a preferred embodiment, the eyelet terminal (3) is provided with one or more "ears" (3a), for example two, in turn preferably provided with slots (3b) for better incorporation into the cap (4) same. The cap (4) comprises, in turn, a main body

(5), of circular shape, which has a central hole

(6) through and coaxial, through which a threaded pin (7) is inserted which allows fixing, by means of a self-locking nut (8), of the eyelet terminal (3), ensuring the metal contact. On the side of the cable (2) there is a sleeve (4a) that covers the end of the cable (2) itself.

Under the sheet metal (9) of the car floor there is a junction node (10), in which converge one or more electric cables (11) electrically connected to a metal element (12) which has the function of ensuring contact electric cable between said one or more electric cables (11) and said electric cable (2). Said junction node (10) is made of insulating material and is equipped with gaskets (not shown) designed to prevent infiltration of liquids inside the node (10) itself.

The upper part of the node (10) partially inserts into a hole in the sheet metal (9) of the floor, leaving said metal element (12) in a slightly raised position from which said threaded pin (7) protrudes. By inserting the pin (7) in the hole of the eyelet terminal (3) and tightening the self-locking nut (8), an efficient electrical connection is obtained between the electric cable (2) and said metal element (12).

While the flat part of the eyelet terminal (3) comes into contact with said conducting metal element (12), the ears (3a) of the eyelet terminal (3), which are embedded in the thermoplastic rubber which constitutes the cap (4), have the function of distributing the compression force, due to the tightening of the nut (8), thus strongly compressing the main body (5) of the cap (4) against the sheet metal (9) which constitutes the floor of the sealing, according to a mechanism that will be specified below. Said conducting metallic element (12) is adequately isolated from the sheet metal (9) of the floor by the insulating material structure of the node (10). A cap (13) is connected to the main body (5) of the cap (4), by means of a flexible lace (14), said cap (13) being able to fit into a circular seat (15) obtained on the upper part of the main body (5) of the cap (4). Said insertion of the cap (13) on the circular seat (15) takes place by bending the flexible lace (14).

The sheet metal (9) of the car floor normally has a thickness of only 0.8 mm so that, by tightening the self-locking nut (8), you risk deforming the sheet itself. To avoid this drawback, the lower part of the main body (5) of the cap (4) is shaped in such a way as to take the form of a suction cup, adapting to the plane of the sheet (9) and exerting adequate pressure in the contact area between main body (5) of the cap (4) and sheet metal (9) of the floor, in order to ensure water tightness

In FIGS. 3 (a, b) shows the way in which the cap (4) carries out the water tightness in the first of the areas of possible infiltration of liquids, i.e. between the lower edge (5a) of the main body (5) and the sheet (9) of the floor.

In particular, in FIG. 3a shows the main body (5) of the cap (4) with the pin (7) inserted in the eyelet (3), but with the nut (8) not yet tightened while in FIG. 3b shows the same main body (5) after tightening the nut (8).

As can be seen from FIG. 3a, when the lower circular edge (5a) of the main body (5) is in contact with the plate (9), but the nut (8) has not yet been tightened, there is a gap (G) between the lower surface of the ring terminal (3) and the upper surface of the conducting metal element (12), for example 2 ÷ 3 mm. When the self-locking nut (8) is tightened, the lower surface of the ring terminal (3) and the upper surface of the conducting metal element (12) come into contact. Said contact is made possible by a controlled deformation of said lower circular edge (5a) of the main body (5). Said deformation consists in a shortening of the edge (5a) itself and a rotation of this towards the outside by an angle (a) between 8° and 12°. An important role is also played by a rounding

(5c), with a radius of curvature between 0.5 mm and 1.5 mm of the internal edge of the edge (5a) which favors a unique sliding towards the outside of the edge (5a) itself.

Finally, an important role is played by the ears (3a, 3b) of the eyelet terminal (3), as said ears (3a, 3b) allow the compression exerted by the nut (8) to approach the peripheral parts of the main body (5), avoiding the risk of shearing the central area of the main body (5) itself.

In FIG. 3b the upper edge of the sheet metal (9) of the floor and the profile of the edge (5a) are shown with dashed lines in the position they had before tightening the self-locking nut (8). In order for the material that makes up the cap (4) to stretch out at its best in this phase, the inside of the main body (5) of the cap (4) must be discharged as much as possible, so that the edge (5a) has the necessary elasticity. In practice, for the edge (5a) of the main body (5) to behave like a suction cup, it must have the following characteristics :

- a thickness (S) comprised between 5% and 15% of the diameter (D) of the main body (5) of the cap (4);

- a height (h) comprised between 10% and 30% of the diameter (D) of the main body (5) of the cap (4);

- an inclination (b) of the internal surface between 7° and 13°. FIG. 4 shows the cap (13) which fits into said circular seat (15), obtained on the upper part of the main body (5) of the cap (4).

Inside the cap (13) a profile has been obtained that is suitable for coupling with the profile of said seat (15), in order to create an effective seal.

These profiles are characterized by the presence of shapes similar to one or more O-rings (17) that couple with corresponding seats (18) with an interference between 0.1 mm and 0.3 mm.

Finally, in the third critical area, i.e. the area on the cable side (2), where infiltrations between the cable (2) itself and the co-molded cap (4) could occur, the criticality is due to the fact that the material of the cap (4) is not compatible with the material of the insulation with which the cable (2) is coated, so that no welding takes place between the two materials in contact. The problem is solved with a suitable increase in the overlap length between said sleeve (4a) and the cable (2) itself. Experimentation has shown that an efficient infiltration seal is obtained with an overlap length between 2 and 3 times the external diameter of the cable (2). The cap (4) must have the following characteristics:

- withstand a high temperature of about 150 ° C continuously; - maintain good flexibility down to -40 ° C;

- have good resistance to abrasions and chemicals;

- have a good mechanical resistance unaltered over time;

- have a good dielectric strength; - resist tearing and tearing;

- reduce the vibrations in the over-molded pieces;

- be self-extinguishing.

A suitable material for making the insulating cap (4) is a TPU thermoplastic polyurethane elastomer, called Elastollan, which is burned in red RAL 3000 and is manufactured by BASF.