Patent Application
20210125969
The invention relates to a flexible light strip, to an automotive light unit comprising this flexible light strip, an embossing tool and a method to manufacture the light strip.
For automotive lighting application there is a need for styling signaling functions. This can be for rear signaling function like turn lights, position lights or stop lights as well for front signaling function like the position and day running light (DRL). These functions are often provided with styled lines in combination with for example light blades.
A lamp design requires a dedicated source that follows the styling wishes of the car- or set maker. A typical source can be a solid state light source such as a LED source arranged in a line array on a substrate as carrier for the solid state light sources. Typical line arrangements are provided as light strips based on flexible foil technology where surface mounted (SMD) LED packages are attached to the flexible foil. The SMD LED packages can be RBG packages but also a single color LEDs with or without single addressability. LED packages can contain one or more LEDs depending on the required color and function. SMD LED packages are also known as L1 package. The flexible foil is a carrier based typically on copper tracks laminated with a polymer or a flexible plastic substrate screen printed with a silver circuit on for example polyester.
For car lamp design flexibility in the source is a must to meet the design requirements which translates to directionality of the light and following the curvature of the light exit window of the lamp. A lamp design requires a specific design of the flexible foil to meet the styling shapes of the lamp has to be designed for every particular case. A flexible foil provides the possibility to bend in a certain shape which is possible for only one axis perpendicular to the length and parallel to the width of the strip. The width axis of a flexible foil cannot be bended along its because the flexible foil is ridged in this direction. In case of demanding flexible foils comprising a curvature along an axis perpendicular to the carrier foil (bended width), these foils have to be explicitly manufactured as permanently curved foils which prevents any application of these curved foils as linear strips for other applications. Therefore the light strips have to be designed for its particular application limiting the technology to the provided design without having any possibility to reshape the specific design of the same flexible foil in order to adapt the flexible foil to other different applications where other different designs are required. The limitation of the design of the flexible foils to a particular application increases manufacturing costs for the particular light strip.
Therefore there is a demand to provide a light strip allowing bending the light strip also over its width enabling one and the same light strip to be used in different automotive lamps that typically would require a dedicated design of flexible foils for each of the different automotive lamps.
DE 10 2014 215938 A1 discloses an optoelectronic assembly which has a carrier strip and optoelectronic components are provided on the carrier strip. The carrier strip has a first longitudinal section for receiving a first optoelectronic component, at least one second longitudinal section for receiving a second optoelectronic component, and a folding section arranged between the first longitudinal section and the second longitudinal section. The folding section has at least two fold lines. The carrier strip has electrical layers to electrically connect and drive the optoelectronic components.
EP 3 094 161 A1 discloses a lighting device including a laminar support member. The laminar support member has bending lines portioning the support member in a plurality of stripes. The stripes include electrically-powered light radiation sources.
EP 3 136 829 A1 discloses a system for mounting electrical components thereon. The system includes an elongated printed circuit board that is configured to couple a plurality of electronic components. The elongated printed circuit board includes segments with the electronic components on it and other segments in between. The other segments having a smaller width than the width of the segments of the components. The segments with smaller width are bendable.
It is an object of the present invention to provide a light strip allowing bending the light strip also over its width enabling one and the same light strip to be used in different lamp designs, especially automotive lamps that typically would require a dedicated design of flexible foils for each of the lamps.
The invention is defined by the independent claims The dependent claims define advantageous embodiments.
According to a first aspect a flexible light strip is provided. The flexible light strip comprises multiple solid state lighting units as light sources and a flexible carrier for the solid state lighting units attached to the flexible carrier, wherein the carrier is a suitable wiring connecting the solid state lighting units to enable suitable driving of the solid state lighting units to illuminate an environment with the flexible light strip, wherein the flexible carrier comprises multiple buffer areas arranged between adjacent solid state lighting units, where the buffer area extends along a width of the flexible carrier from one edge to the opposite edge of the flexible carrier and being adapted to be able to be compressed and expanded on demand.
The flexible light strip might be made of any material providing an electrical insulation for the embedded or coated wiring and a certain flexibility in order to be bended without leading to cracks within the flexible carrier. In an embodiment the flexible carrier is a flexible foil comprising the suitable wiring or the flexible carrier is the wiring itself, preferably established by conductive rails, separated from each other in order to avoid a short between the wiring or conductive rails. The term “foil” denotes a thin sheet of material as a carrier with a thickness thin enough to enable bending of the carrier. The flexible foil is based typically on copper tracks laminated with a polymer or a flexible plastic substrate, e.g. polyester, screen printed with a silver circuit on top of the flexible substrate. Foils might be made for instance of Kapton, a polyimide foil which is resistant to high temperatures, or of Pyralux (polyimide-fluoropolymer-foil). These materials are formable into a certain shape and remain in this formed shape. The conductive rails (or wires) are massive wires, which have to be suitably prepared to be bendable without increasing the risk of shorts between the conductive rails or occurring cracks within the rails. The conductive rails (or wires) might be made of copper or any other suitable conductive material, preferably copper coated with layers of nickel or gold. Suitable diameters of such conductive rails may range from 0.2 mm to 0.7 mm, typically about 0.4 mm.
The term “solid state lighting unit” denotes any lighting source that uses semiconductor light-emitting diodes (LEDs), organic light-emitting diodes (OLED), polymer light-emitting diodes (PLED) or laser diodes to illuminate the environment. The term “solid state” refers commonly to light emitted by solid-state electroluminescence, as opposed to incandescent bulbs (which use thermal radiation) or fluorescent tubes. On the flexible carrier the solid state lighting units are electrically connected in series, parallel or a combination of both. The corresponding wiring is laid out accordingly. In case of a flexible foil as the carrier the wiring might be embedded into the foil or deposited as a coating on top of the foil. Commonly the solid state lighting units are attached to the flexible carrier and connected to the wiring by surface mounting technologies, e.g. so-called SMD LED packages might be used. The solid state lighting units may provide a mixture of red/green/blue light or a single color. The solid state lighting units might be addressable with or without single addressability. The solid state lighting units may comprise one or more solid state light sources depending on the required color and function. For instance SMD LED packages are also known as L1 packages.
The buffer area has to be compressed and expanded on demand in order to enable bending of the light strip around an axis perpendicular to the surface of the light strip (bending along its width). Without such buffer areas the light strip made of a flexible material is only bendable around an axis parallel to the surface of the light strip unduly limiting the shaping options for such light strips. In order to provide the required compressibility and expansibility the material of the flexible carrier as a flexible foil might be elastic material providing the compressibility and expansibility even in a flat geometry of the entire light strip. Alternatively for carriers as flexible foils or conductive rails the buffer area might be shaped three-dimensional to provide a material buffer enabling to compress and expand the buffer area by compressing or expanding the three-dimensional structure of the buffer area. In both cases the buffer area extends along a width of the flexible carrier from one edge to the opposite edge of the flexible carrier not to limit the bendability of the light strip. The three-dimensional shape of the buffer area may comprise sharp or rounded edges providing the buffer function.
The light strip according to the present invention might be used for illumination of the environment in any cases, e.g. room illumination, decorative illumination, street illumination or as signal lamp, where the lamp design requires styled lines of light sources to provide a certain light impression.
The light strip according to the present invention allows bending of the light strip also over its width enabling use of the same light strips in different lamp designs, e.g. in automotive lamps, that typically would require a dedicated design of flexible carriers for each of the lamps. The lighting strip can be used in multiple different applications without modification of the manufacturing steps of the light strip therefore reducing the manufacturing costs per light strip. Additionally former required blades to shape the light emitting area in case of extended emitting areas to a certain impression can be avoided since the bendable light strip already provides the demanded shape of the light emitting area.
In an embodiment each of the solid state lighting units is followed by at least one of the buffer areas along a length of the light strip. A high number of buffer areas increase the flexibility of the light strip along a bending axis perpendicular to the surface of the light strip. In case of a buffer area between each solid state lighting units, the bendability is optimized.
In another embodiment the buffer area is shaped as a buckling area in order to decrease the distance between adjacent solid state lighting units in a non-bended state of the light strip along its length. A buckling area comprises at least one three-dimensional shape, e.g. like a bulge, a bump, a buckle or any other suitable shape. The buckling area can be compressed on one side towards one of the edges of the flexible carrier and can be simultaneously expanded on the other side towards the other edge of the flexible carrier in order to enable bending of the flexible carrier (and therefore the light strip) around an axis perpendicular to the surface of the flexible carrier. The buckling area is advantageous, because this kind of bending mechanism does not provide unduly stress to the wiring embedded in or arranged on top of the flexible carrier and therefore reduces the risk of failing wiring.
In another embodiment a maximum height of the buffer area above an area of the flexible carrier between the buffer areas defines the maximum local bending angle for the light strip relative to a linear shape of the light strip when being non-bended provided by each buffer area. The maximum height is half of the length of the buffer area along the length of the light strip. Longer buffer areas provide a larger bendability. Longer buffer areas result in less space for mounting the solid state light units. When using brighter solid state lighting units, the length of the buffer areas can be increased providing an increased bendability of the light strip. Bright solid state lighting units might be high power LEDs but also MID or LOW power LEDs depending on the application light flux requirements. Also the pitch between neighbored solid state lighting units is relevant for adjusting the possible bending radius. Therefore the use of small solid state lighting units leading to smaller areas between the buffer areas enables a shorter bending radius.
In another embodiment the buffer area is shaped as a gable roof comprising two roof sections sloping in opposite directions and placed such that the highest edges meet to form a roof ridge. The gable roof geometry of the buffer area provides good compressibility and good expansibility combined with a decreased effort during manufacturing. The simple geometry can be manufactured easily, which additionally ensures a good manufacturing yield.
In another embodiment a roof angle at the roof ridge provided by the two roof sections is essentially 90 degree in a non-bended state of the light strip along its length. This will ensure a symmetric bending of the flexible foil since this roof angle is present at the middle of the width of the flexible foil when being bended.
In another embodiment the buffer areas are made of a ductile material providing the advantageous properties for the compressing and expanding function of the buffer areas. A ductile material will remain in the bended status without applying any force to hold the flexible carrier in its desired bended shape. Therefore a ductile material will reduce the handling effort during manufacturing of the lamp equipped with the light strip. In case of the carrier as conductive rails common conductive materials such as copper are ductile materials.
According to a second aspect an automotive light unit is provided. The automotive light unit comprises at least one flexible light strip according to the present invention. For automotive lighting application there is a need for styling signaling functions. Flexible styling is enabled by the light strip according to the present invention without further need to shape the lamp impression by additional components like blades etc. The claimed automotive light unit is able to follow the styling wishes of car and set makers. The automotive lamp unit according to the present invention might be used as tail light, stop light, indicator light, daytime running light but also for general lighting where light strips are used.
According to a third aspect an embossing tool to manufacture a light strip according to the present invention is provided. The embossing tool comprises at least one male sub-tool and at least one female sub-tool each comprising embossing surfaces facing towards within the embossing tool, where the embossing surfaces comprise at least one positive and one corresponding negative shape adapted to a demanded shape of a buffer area of the light strip, which comprises multiple solid state lighting units as light sources, a flexible carrier for the solid state lighting units and suitably shaped buffer areas within the flexible carrier between adjacent solid state lighting units to be able to be compressed and expanded on demand. The embossing tool according to the present invention provides the demanded structure of the buffer area and guaranties a proper alignment of the embossed structure of the buffer area. The flexible pre-carrier might be inserted into the embossing tool manually or automatically to manufacture the final flexible carrier comprising the buffer areas as buckling areas. There could be multiple embossing tools arranged in line to simultaneously emboss multiple buffer areas on the flexible carrier. The embossing tool according to the present invention enables easy manufacturing of the demanded shape of the buffer areas. In particular the embossing tool and the corresponding embossing process according to the present invention can be applied to carriers arranged as flexible foils or arranged as conductive rails or wires.
In an embodiment of the embossing tool, the male and female sub-tools are shaped as rotatable cylindrical wheels with lateral surfaces as the embossing surfaces comprising multiple positive and corresponding negative shapes, where the positive and negative shapes are suitable located onto the cylindrical wheels in order to receive each other during rotating the cylindrical wheels. Here the speed of manufacturing can be increased simultaneously by easy handling of the embossing tool. The rotatable cylinders avoid the need of more than one separate embossing tool as would be the case for fast inline production.
In another embodiment of the embossing tool diameters of the cylindrical wheels are suitably adapted to provide releasing of a received pair of the positive and negative shapes simultaneously to receiving a following pair of the positive and negative shapes in order to continuously feed the flexible carrier through the embossing tool without requiring additional motors to pull or push the flexible carrier through the embossing tool.
According to a third aspect a method to manufacture a light strip according to the present invention comprising multiple solid state lighting units as light sources, a flexible carrier for the solid state lighting units and suitably shaped buffer areas between adjacent solid state lighting units is provided. The method comprises the steps of
Providing a flexible pre-carrier as carrier for the solid state lighting units, wherein the pre-carrier is a wiring suitable to connect the solid state lighting units to enable suitable driving of solid state lighting units when being attached to the carrier, wherein the flexible pre-carrier comprises multiple flat pre-buffer areas along the flexible pre-carrier separated from each other to enable placing of the solid state lighting units in between the pre-buffer areas, which extend along a width of the flexible pre-carrier from one edge to the opposite edge of the flexible pre-carrier;
providing an embossing tool for an embossing process comprising a male sub-tool and a female sub-tool each comprising embossing surfaces facing towards within the embossing tool, where the embossing surfaces comprise at least one positive and one corresponding negative shape adapted to the demanded shape of the buffer area of the light strip;
inserting at least the pre-buffer areas of the flexible pre-carrier into the embossing tool between the embossing surfaces;
transferring the flat pre-buffer area into the demanded shape of the buffer area by the positive and corresponding negative shapes receiving each during the embossing process; and
repeating the previous inserting and transferring steps for the following non-treated pre-buffer areas of the flexible pre-carrier until all demanded buffer areas are shaped by the embossing process to be able to be compressed and expanded on demand.
The flexible pre-carrier and the pre-buffer area denote the flexible carrier and the buffer areas before shaping the buffer areas by embossing. In particular the method according to the present invention can be applied to carriers arranged as flexible foils or arranged as conductive rails or wires.
In an embodiment the method further comprises the step of attaching the solid state lighting units to the embossed flexible carrier in order to provide the light strip equipped for illuminating the environment. The mounting (attaching) of the solid state lighting units after the embossing process prevents any damage of the solid state lighting units by the embossing process. In case of damages to the flexible carrier during embossing the damaged carrier can be selected out without wasting attached solid state lighting units.
In another embodiment of the method the flexible pre-carrier already carries one or more solid state lighting units between adjacent pre-buffer areas of the flexible pre-carrier before inserting the pre-buffer areas into the embossing tool, where the embossing surface of the male or female sub-tool comprises a recess suitable to receive the attached solid state lighting unit during embossing the pre-buffer areas in order to provide the light strip for illuminating the environment. Mounting (attaching) of solid state lighting units is easier in case of a flat flexible carrier as being present before executing the embossing process.
In another embodiment of the method the male and female sub-tools are shaped as cylindrical wheels with lateral surfaces as the embossing surfaces comprising multiple positive and corresponding negative shapes suitable located onto the embossing surfaces in order to receive each other during rotating the cylindrical wheels, where the inserting and transferring steps are executed by simultaneously rotating the cylindrical wheels with the flexible pre-carrier inserted between the cylindrical wheels. This embodiment allows for an even faster and easier embossing process.
It shall be understood that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.
Further advantageous embodiments are defined below.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.
The invention will now be described, by way of example, based on embodiments with reference to the accompanying drawings.
In the drawings:
In the Figures, like numbers refer to like objects throughout. Objects in the Figs. are not necessarily drawn to scale.
Various embodiments of the invention will now be described by means of the Figures.
In a further embodiment of the method the male and female sub-tools 110, 120 are shaped as cylindrical wheels 110, 120 with lateral surfaces as the embossing surfaces 130, 140 comprising multiple positive and corresponding negative shapes 131, 141 suitable located onto the embossing surfaces 130, 140 in order to receive each other during rotating the cylindrical wheels 110, 120, where the inserting and transferring steps 230, 240 are executed by simultaneously rotating the cylindrical wheels 110, 120 with the flexible pre-carrier 3p inserted between the cylindrical wheels 110, 120.
While the invention has been illustrated and described in detail in the drawings and the foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.
From reading the present disclosure, other modifications will be apparent to persons skilled in the art. Such modifications may involve other features which are already known in the art and which may be used instead of or in addition to features already described herein.
Variations to the disclosed embodiments can be understood and effected by those skilled in the art, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality of elements or steps. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.
Any reference signs in the claims should not be construed as limiting the scope thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17191284.3 | Sep 2017 | EP | regional |
This application is a § 371 application of International Application No. PCT/EP2018/074114, filed Sep. 7, 2018, which claims the benefit of EP Patent Application No. 17191284.3, filed Sep. 15, 2017, which are incorporated by reference as if fully set forth.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/074114 | 9/7/2018 | WO | 00 |
