Patent Description:
Electrical devices, such as cable wires extending through a cable insulation, are well-known in the art. Thermoset overmolding of electronics is also a known technology in connection with electrical devices, in particular in the automotive industry. Especially automotive industry applications require a tight electrical connection for ensuring a long life of the electrical device. Currently, printed circuit boards (PCB) may be directly contacted with a cable wire and, then, for sealing, a thermoset material is overmolded for sealing the whole arrangement.

Problems associated with the known technique are partially based on bad adhesion properties of the overmolding material at the cable insulation housing the cable wire. This may lead to creeping of the ambient medium along a gap between the overmolding material and the cable insulation which decreases the overall tightness significantly. In addition, clamping forces of any overmold tooling may damage the cable insulation and/or the cable wires. Further, sharp edges and/or rims of the thermoset overmolding element may lead to abrasion of the cable insulation due to wear.

However, the biggest disadvantage is based on the high creeping capability of the very low viscous thermoset overmolding material which may creep into any gaps between the cable wire and cable insulation. Said creeping and curing of the thermoset overmolding material within said gaps may increase the overall brittleness of the cable arrangement.

Exemplary electrical devices are known from <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

Further devices are disclosed in <CIT>, <CIT> and <CIT>.

Therefore, it is an object of the present invention to provide an electrical device with improved sealing properties and which may ensure its functionalities over a very long time.

This object may be achieved by the electrical device according to independent claim <NUM> and the method for manufacturing an electrical device according to independent claim <NUM>.

The present invention is at least partially based on the realization that providing a heat-shrink tube at a cable wire insolated with a cable insulation and filling that heat-shrink tube with a filling material may improve the sealing capabilities of the whole arrangement. In particular, mounting the heat-shrink tube filled with the sealing material to the cable wire insulated within the cable insulation and, then, applying heat to the heat-shrink tube may at least partially shrink the tube and, thus, shrinking of the tube may lead to forcing the filling material into any gaps between the cable insulation and the cable wire. This can be particularly advantageous in a case when the cable wire connects to a printed circuit board which is then embedded in a thermoset material, such as, for instance, a thermosetting polymer, e.g. polyester resin, phenol-formaldehyde Resin, epoxy resin, bulkmolding compound, etc., via a thermoset overmolding process.

Therefore, according to a first aspect of the present invention, an electrical device is disclosed. The electrical device according to the present application comprises at least one cable wire, a cable insulation arranged around the at least one cable wire such that a section of the at least one cable wire at least partially longitudinally protrudes out of the cable insulation, a heat-shrink tube at least partially arranged (in a longitudinal direction) around the cable insulation and at least partially arranged (in a longitudinal direction) around the section of the at least one cable wire protruding out of the cable insulation, and a sealing material at least partially provided inside the cable insulation thereby sealing any gaps between the cable insulation and the at least one cable wire. Additionally, the electrical device according to the present invention further comprises a sealing element arranged (in a longitudinal direction) at least partially around the heat-shrink tube and at least partially around the section of the at least one cable wire protruding out of the cable insulation. The sealing element may be formed by a thermoset overmolding process.

The sealing material which may be forced by heat-shrinking the heat-shrink tube into any gaps between the cable insulation and the at least one cable wire may prevent any thermoset material applied to the electric device via said thermoset overmolding process from creeping into said gaps between the at least one cable wire and the cable insulation.

Preferably the electrical device of the present invention may further comprise an electronic assembly embedded within the sealing element and electrically connected to the at least one cable wire. For instance, the electronic assembly may be a printed circuit board having electrical conductors which may be connected to the at least one cable wire.

In a further advantageous embodiment of the electrical device according to the present invention, after the overmolding process, the sealing material is adapted to be at least partially solid after curing, but to be at least partially liquid prior curing. After curing, the sealing material is configured to remain an elasticity which is suitable for ensuring at least some flexibility of the at least one cable wire and/or cable insulation without the risk of any damage to the at least one cable wire and/or the cable insulation. For instance, the viscosity of the sealing material after curing may be in a range from about <NUM> mPas to about <NUM> mPas, preferably from about <NUM> mPas to about <NUM> mPas, more preferably about <NUM> mPas.

In a further and preferred embodiment, the sealing material is a hotmelt adhesive, glue, wax or grease.

Advantageously, the heat-shrink tube is heat-shrunk by applying heat to the heat-shrink tube via, for example, a hot air gun, infrared lights, an oven, inserting in a preheated thermoset mold, etc..

Preferably, an inner layer of the heat-shrink tube is at least partially covered with the sealing material prior mounting the heat-shrink tube to the cable insulation.

In a further aspect of the present invention, a method for manufacturing an electrical device is disclosed. The method according to the present invention comprises providing at least one cable wire and a cable insulation arranged around the at least cable wire such that a section of the at least one cable wire at least partially longitudinally protrudes out of the cable insulation, providing (in a longitudinal direction) a heat-shrink tube at least partially around the cable insulation and at least partially around the section of the at least one cable wire protruding out of the cable insulation, providing a sealing material at least partially within the heat-shrink tube, and applying heat to the heat-shrink tube such that the heat-shrink tube at least partially shrinks thereby forcing the sealing material into the cable insulation for sealing any gaps between the cable insulation and the at least one cable wire. The method of the present invention further comprises thermoset overmolding at least partially the heat-shrink tube and at least partially the section of the at least one cable wire protruding out of the cable insulation for forming a sealing element.

Thus, by applying heat to the heat-shrink tube preferably prefilled with sealing material may shrink the heat-shrink tube thereby forcing the sealing material into any gaps between the at least cable wire and the cable insulation for sealing the same.

Sealing of any gaps with the sealing material originally provided within the heat-shrink tube may prevent any thermoset material applied via the thermoset overmolding process from creeping into the cable insulation. Thus, the cable insulation can be maintained elastic and the cable wires can be prevented from any damage caused by thermoset material creeped into the cable insulation.

In a further advantageous embodiment, the method of the present invention may further comprise providing at least one electronic assembly within the sealing element and electrically connecting the at least one conductor with the at least one cable wire. Preferably, the electronic assembly is electrically connected to the at least one cable wire prior thermoset overmolding the electronic assembly with a thermoset material for sealing the electronic assembly. For example, the electronic assembly may be a printed circuit board.

Preferably, the sealing material is adapted to be at least partially liquid during the overmolding and sealing process for ensuring that the sealing material is able to flow into any gaps between the at least one cable wire and the cable insulation. After curing, the sealing material may be at least partially solid. Alternatively, the sealing material may be adapted to stay at least partially soft.

Further, it may be preferred that the sealing material is a hotmelt adhesive, wax or grease.

In addition, it may be advantageous that the step of applying heat to the heat-shrink tube includes applying heat to the heat-shrink tube of a temperature in a range (depending on the sealing material) between about <NUM> and about <NUM>.

It may be further preferred that an inner layer of the heat-shrink tube is at least partially covered with the sealing material prior mounting the heat-shrink tube to the cable insulation and the at least one cable wire.

Further features and aspects of the present invention will become apparent to those ordinary skilled in the art by studying and executing the present disclosure and by consideration of the appended drawings, in which:.

<FIG> shows a sectional view of an inventive electrical device <NUM>. The electrical device <NUM> includes a cable wire <NUM> extending within a cable insulation <NUM> along a longitudinal direction <NUM> such that a section of the cable wire <NUM> at least partially longitudinally protrudes out of the cable insulation <NUM>. A heat-shrink tube <NUM> is arranged such that, in a longitudinal direction, it at least partially surrounds the cable insulation <NUM> and at least partially surrounds the section of the cable wire <NUM> protruding out of the cable insulation <NUM>. The heat-shrink tube <NUM> is at least partially filled with a sealing material <NUM> which is provided between the heat-shrink tube <NUM> and the cable insulation <NUM> and between the at least one cable wire <NUM> and the cable insulation <NUM> (see <FIG>). However, it is also in the scope of the present invention that the heat-shrink tube <NUM> directly contacts the cable insulation <NUM> without any sealing material <NUM> therebetween.

The sealing material <NUM> may be a hotmelt adhesive, such as, for example, wax, grease. The sealing material <NUM> may be configured to stay continuously soft and elastic. Alternatively, the sealing material <NUM> is configured to stay at least partially soft at least during the overmolding and sealing process but may be solid after the sealing material has filled any gaps between the at least one cable wire <NUM> and the cable insulation <NUM>. In the latter case, the sealing material <NUM> is configured to include an elasticity to provide a suitably flexibility for the at least one cable wire <NUM> and/or the cable insulation <NUM>.

The electrical device <NUM> of <FIG> further includes a sealing element <NUM> made of a thermoset material and formed by a thermoset overmolding process. Specifically, as can be seen in <FIG>, the sealing element <NUM> is arranged at least partially around the heat-shrink tube <NUM> and at least partially around the section of the cable wire <NUM> extending out of the cable insulation <NUM>. In the preferred embodiment shown in <FIG>, the electrical device <NUM> further includes an electronic assembly <NUM>, such as, for instance, a printed circuit board, that is electrically connected to the section of the cable wire <NUM> protruding out of the cable insulation <NUM>. Preferably, the sealing element <NUM> is configured to entirely encapsulate the electronic assembly <NUM> for sealing the same against the ambient, such as, for example, air or a fluid. For instance, the electronic assembly <NUM> may be part of a fluid sensing device and may be drown in an aggressive fluid, such as urea.

<FIG> shows an enlarged view of section A (see dash-dotted circle) of <FIG>. As can be seen in <FIG>, the sealing material <NUM> is provided within a gap between the at least cable wire <NUM> and the cable insulation <NUM>. In particular, the sealing material <NUM> can be forced into the portion between the at least one cable wire <NUM> and the cable insulation by heat-shrinking the heat-shrink tube <NUM>. The resulting shrinkage of the heat-shrink tube <NUM> may change the inner volume of the heat-shrink tube thereby forcing the sealing material <NUM> into any gaps between the at least one cable wire <NUM> and the cable insulation <NUM>.

For ensuring that the sealing material <NUM> is mainly forced into said gaps, the heat-shrink tube <NUM> may be first heated at the side where it surrounds the cable insulation <NUM>. Then, the heat-shrink tube <NUM> may be heated from the side opposite thereto, namely where the heat-shrink tube <NUM> surrounds the at least one cable wire <NUM> protruding and extending out of the cable insulation <NUM>, wherein the heating may be advanced in direction of the cable insulation <NUM>.

<FIG> shows an exemplary flow chart of a method for manufacturing an electrical device <NUM> according to the present invention.

The method of <FIG> starts at step <NUM> and then proceeds to step <NUM> where at least one cable wire <NUM> and a cable insulation <NUM> arranged around the at least one cable wire <NUM> are provided such that a section of the at least one cable wire <NUM> at least partially longitudinally protrudes out of the cable insulation <NUM>.

In a next step, a heat-shrink tube <NUM> is provided such that, in a longitudinal direction, it at least partially surrounds the cable insulation <NUM> and at least partially surrounds the section of the at least one cable wire <NUM> protruding out of the cable insulation <NUM>. In addition, prior providing, the heat-shrink tube <NUM> is filled with a sealing material <NUM>. Specifically, an inner layer of the heat-shrink tube <NUM> is at least partially covered with the sealing material <NUM>.

Alternatively, before providing the heat-shrink tube <NUM> about the cable insulation <NUM> and the section of the at least one cable wire <NUM> extending out of the cable insulation <NUM>, the sealing material <NUM> may be applied to the portion where the heat-shrink tube <NUM> will be provided and mounted. Then, after applying the sealing material <NUM> to the cable insulation <NUM> and the cable wire <NUM>, the heat-shrink tube <NUM> is provided around the sealing material <NUM>.

Then, in a next step <NUM>, heat is applied to the heat-shrink tube <NUM> such that the heat-shrink tube <NUM> at least partially shrinks thereby forcing the sealing material <NUM> into the cable insulation <NUM> for sealing any gaps between the cable insulation <NUM> and the at least one cable wire <NUM>.

In a final step <NUM>, the heat-shrink tube <NUM> and the section of the at least one cable wire <NUM> protruding out of the cable insulation <NUM> is thermoset overmolded with a thermoset material for forming a sealing element <NUM>. Then, the method ends at step <NUM>.

In a preferred embodiment, an electronic arrangement <NUM>, such as a printed circuit board, may also be embedded within the thermoset sealing element <NUM>.

The electrical device <NUM> according to the present invention may be applicable to, for example, all kinds of sensors. For example, the electronic assembly <NUM> may carry an ultrasound transducer configured to be immersed in an aggressive liquid, such as urea. With the present invention, a proper electrical connection between the electronic assembly <NUM> embedded within the sealing element <NUM> for sealing the same and an associated control unit may be ensured.

Claim 1:
An electrical device (<NUM>) for connecting at least one cable wire (<NUM>) to a printed circuit board, the electrical device comprising:
- the at least one cable wire (<NUM>);
- a cable insulation (<NUM>) arranged around the at least one cable wire (<NUM>) such that a section of the at least one cable wire (<NUM>) at least partially longitudinally protrudes out of the cable insulation (<NUM>);
- a heat-shrink tube (<NUM>) at least partially arranged around the cable insulation (<NUM>) and at least partially around the section of the at least one cable wire (<NUM>) protruding out of the cable insulation (<NUM>);
- a sealing material (<NUM>) at least partially provided inside the cable insulation (<NUM>) thereby sealing any gaps between the at least one cable wire (<NUM>) and the cable insulation (<NUM>); and characterised by comprising:
- a sealing element (<NUM>) arranged at least partially around the heat-shrink tube (<NUM>) and at least partially around the section of the at least one cable wire (<NUM>) protruding out of the cable insulation (<NUM>), the sealing element (<NUM>) being formed by a thermoset overmolding process.