The present invention relates to a holder for receiving a light source, comprising an extrusion profile of at least one thermoplastic polyurethane compound with a cavity running therein in longitudinal direction and bounded by longitudinal walls, which cavity provides a seat for placing the light source.

The invention relates particularly here to a holder for a ribbon-like light source, such as particularly an LED strip. Such an LED strip usually comprises a strip-like and somewhat flexible carrier which is covered longitudinally with a series of successive light-emitting diodes (LEDs). The carrier further comprises a metallization which provides an electrical wiring for the light sources and any other control electronics provided on the carrier.

The carrier with light sources is arranged in a holder in order to enable a practical assembly and connection thereof. With a view to applications in humid environments or in the open air, it is desirable here for the carrier to be sealed moisture-tightly in the holder.

A known holder comprises a sturdy U-shaped extrusion profile of a thermoplastic polyurethane (TPU) compound. The light source is received on a bottom thereof and the space in the cavity thereabove is filled with a fluid transparent plastic, which then cures. This process is however labour-intensive and time-consuming, not least due to the drying time required by the plastic used. Another known holder comprises a similar extrusion profile on the basis of a silicone compound. This has however been found to be insufficiently stable under the influence of UV radiation.

The present invention therefore has for its object, among others, to provide a holder in which a light source can be accommodated and which obviates these drawbacks to at least significant extent.

In order to achieve the stated object a holder of the type described in the preamble has for this purpose the feature according to the invention that a first of said walls provides an exit window for a light image to be generated by the light source, that the first wall lies on a support body which extends in the cavity, that the first wall is formed at least substantially from a transparent or at least translucent aliphatic polyurethane compound, and that for the support body use is made at least substantially of a transparent or at least translucent aromatic polyurethane compound.

The extrusion profile thus comprises a co-extrusion of different components which together will form the holder. For this reason the first wall, which forms an exit window for the light image to be generated by the light source, must be transparent. This will also be a visible side when used with the light source, whereby this layer is furthermore susceptible to the effects of ambient light and particularly degradation as a result of UV radiation. The aliphatic polyurethane compound used for the first layer is highly UV- resistant and transparent, and thereby meets these two requirements. The aliphatic polyurethane compound however cannot be extruded to be immediately form-retaining, but is instead still soft or even runny immediately after extrusion. The support body under the aliphatic top layer is composed of an aromatic polyurethane compound and exits the extrusion mould in a sufficiently form-retaining state. This provides support to the as yet incompletely cured aliphatic top layer lying thereon. Because this body takes a transparent or at least translucent form, light is let through to the aliphatic top layer. The further walls can likewise be composed of an aromatic polyurethane compound and can in that case likewise be extruded to be immediately form-retaining. It is however optionally also possible to opt for an aliphatic polyurethane compound for these walls, in which case the support body provides support thereto following the extrusion in similar manner as it does to the first layer. A preferred embodiment of the holder according to the invention therefore has the feature that the extrusion profile comprises a co-extrusion of at least the first wall and the support body.

With a view to a homogeneous light image of a series of successive light sources inside the holder a particular embodiment of the holder has the feature according to the invention that the first wall is provided with an optically scattering surface structure. The scattering top layer spreads the light incident from below and coming from the light source, whereby individual light sources are recognizable as such in the light image to lesser extent. Instead, the device emits a largely uniform light image in the longitudinal direction, both above and between the successive light sources. With a view to easy assembly, a further preferred embodiment of the holder has the feature according to the invention that the support body maintains a recess to one of the further walls, which recess provides the seat for the light source, particularly for accommodating a strip-like light source, such as particularly an LED strip covered with a series of light-emitting diodes (LEDs). The recess provides here an axially running infeed slot into which a strip-like light source can be introduced in simple manner afterward.

An LED strip usually comprises a flexible carrier on which individual LEDs are mounted. This carrier particularly allows transverse bending transversely of a longitudinal direction thereof, over a back side thereof. In a first further embodiment the holder has the feature according to the invention that said walls are flexible and that the further wall and the recess lie opposite the first wall. The holder is thus flexible in the longitudinal direction transversely of the exit window. A second further embodiment of the holder however has the feature according to the invention that said walls are flexible and the further wall and the recess lie adjacently of the first wall. This embodiment thus allows bending of the holder in the plane of the exit window.

In a further particular embodiment the holder has the feature according to the invention that the support body comprises on a side directed toward the seat an at least substantially U-shaped recess which opens toward the seat. The support body does not take a solid form here but a hollow form, with a limited wall thickness along the recess. On one hand, the limited wall thickness enhances a uniform and faster curing during extrusion and prevents the formation therein of inclusions which might otherwise disrupt the light image. On the other hand, the wall is still sufficiently strong to provide sufficient support to the longitudinal outer wall of the holder lying adjacently thereof.

Owing to the reduced wall thickness of the support body, the light coming from a light source lying thereunder travels a more similar optical path therein in all directions. This also enhances the uniformity of the light image. In a further embodiment of the holder this latter is further enhanced, characterized in that the U-shaped recess has internally, on a side lying opposite the seat, a curvature and particularly runs at least substantially in a semicircle.

From a viewpoint of optical output it is preferred that light emitted by a light source can exit as far as possible only via the exit window of the first layer. A further preferred embodiment of the holder therefore has the feature according to the invention that the further longitudinal walls are at least substantially lightproof, particularly reflective, more particularly in that a pigment has been added thereto. With the exception of the exit window in the first layer, the light is thus as far as possible trapped inside the holder and reflected so that as much light as possible will exit the holder via the exit window.

In contrast to an aliphatic polyurethane, many aromatic polyurethane compounds are sensitive to UV light. On the other hand, aromatic polyurethane compounds can be extruded to be sturdier and more form-retaining. A preferred embodiment of the holder therefore has the feature that the further longitudinal walls comprise at least substantially an aromatic polyurethane compound and are provided with UV protection, particularly in the form of a UV-resistant coating or UV-resistant additive. The further walls thus already provide strength immediately after extrusion, and are furthermore protected against degradation as a result of UV radiation.

The invention will be further elucidated hereinbelow with reference to an exemplary embodiment and an accompanying drawing. In the drawing:

Figure 1 is a perspective view of a first exemplary embodiment of the holder according to the invention;

Figure 2 is a cross-section of the first exemplary embodiment of the holder according to the invention; and

Figure 3 is a cross-section of a second exemplary embodiment of the holder according to the invention.

It is otherwise noted here that the figures are purely schematic and not always drawn to (the same) scale. Some dimensions in particular may be exaggerated to greater or lesser extent for the sake of clarity. Corresponding parts are designated in the figures with the same reference numeral.

Figure 1 shows an isometric view of a first exemplary embodiment of a holder according to the invention. The holder is intended and configured to accommodate a light source therein, as illustrated in cross-section in figure 2. The holder comprises an extrusion profile which is formed integrally by co-extrusion of different thermoplastic polyurethane (TPU) compounds at increased temperature. For a first wall 10 use is made here of a transparent aliphatic TPU block polymer, while for the further walls 20 an opaque aromatic TPU is opted for. TPUs comprise block copolymers with hard and soft blocks, whereby a great variety of mechanical properties can be achieved; from rubber-like to tenacious high-grade plastics. TPUs generally have a high tensile strength and very good flexibility and tenacity at low temperatures. Owing to the good damping and high wear resistance, TPUs are also suitable for industrial applications. A high resistance to oils and greases moreover make TPUs suitable for automotive applications.

The soft elements in the block copolymer can be ether- or ester-based, and the hard blocks can be aromatic or aliphatic. Suitable TPU compounds for the present application are for instance polyether-based polyurethanes with a typical hardness of between 50 shore A and 75 shore D and commercially available under the brand name Elastollan® from the BASF company. A white pigment is added to the TPU for the further walls 20, as is a UV blocker which protects the layer 20 against degradation under the influence of UV radiation. The aliphatic TPU of the first layer is naturally sufficiently resistant to UV radiation.

The walls 10, 20 mutually enclose a body cavity 15 which extends axially in the profile. The profile further comprises a support body 30 which was formed in the body cavity 15 together with the walls 10, 20. The support body 30 comprises at least substantially a transparent aromatic TPU and thus lies enclosed, shielded from UV radiation, beneath the top layer 10 and between the opaque side walls 20. Support body 30 maintains a recess 25 to one of the further walls 20. As can be seen clearly in cross-section in figure 2, this recess 25 provides a seat for a light source 40, 45.

In this example this is a strip-like light source, such as the LED strip shown here. Such an LED strip usually comprises a somewhat flexible, elongate plastic carrier 40 on which a series of individual light-emitting diodes (LEDs) 45 is arranged at a regular pitch in longitudinal direction. Also present on carrier 40 is a metallization to which the individual LEDs are electrically connected. Just as the cavity 15 and the support body 30, the recess 25 also extends over the whole length in the profile so that the strip can be accommodated therein over the whole length. In practice this is done by sliding the strip into the profile from one of the two end surfaces of the profile.

On a side facing toward the seat support body 30 has an at least substantially U- shaped recess which opens toward the seat 25. On a side thereof lying opposite the seat the U-shaped recess has internally a curvature which runs at least substantially in a semicircle. Support body 30 hereby has a reduced wall thickness w around the recess, which thickness is however still sufficient to provide adequate support. This enhances the drying and curing of the support body during extrusion, and counteracts the formation therein of inclusions which could otherwise optically disrupt the light image.

For the purpose of a uniform light image a surface structure which scatters the light entering from below is further arranged in the first layer 10. The individual LEDs 45 of the LED strip 40 thereby give off the appearance of a continuous line of light. This surface structure can already be provided simultaneously with the extrusion by machining the top layer 10 with a profiled roller or adding a granular additive thereto.

A specific aliphatic TPU component which has a naturally mat and diffuse surface can also be selected for the first wall.

In the embodiment shown in figure 2 the recess 25 lies opposite the first layer 10 and the shown assembly is bendable rearward around the line B-B. Figure 3 shows a similar exemplary embodiment, wherein the recess 25 however lies adjacently of the first layer 10 and the holder is thereby laterally bendable. In both cases the transparent first layer 10 provides an exit window along which the light from light source 45 can exit. The white side walls 20 reflect any light incident thereon so that this light finally likewise exits via the first layer as far as possible.

Although the invention has been further elucidated above with reference to only a single exemplary embodiment, it will be apparent that the invention is by no means limited thereto. On the contrary, many variations and embodiments are still possible within the scope of the invention for a person with ordinary skill in the art. Instead of an integrally extruded TPU profile, use can also be made for the further walls of the holder in particular of a sufficiently stiff U-profile as premade product, for instance of aluminium, another metal or another plastic, into which a co-extrusion of the support body together with the first layer is in that case placed while a recess is maintained for the light source. For the further walls of the holder it is optionally also possible to apply a co-extrusion of UV-stable aliphatic TPU, which is in that case likewise supported by the support body in the same way as the first wall.