Patent Description:
Almost all aircraft are equipped with aircraft lights, including exterior aircraft lights, which are installed on the outside of the aircraft, and interior aircraft lights, which are installed within the aircraft. Exterior aircraft lights may include navigation lights, white anti-collision strobe lights, red-flashing beacon lights, take-off lights, taxi lights, runway turn-off lights, landing lights, logo lights, cargo loading lights, wing scan lights, engine scan lights, and search lights. Interior aircraft lights may include cabin illumination lights, washroom illumination lights, galley illumination lights, aisle guidance lights, passenger reading lights, and exit sign lights.

Such aircraft lights may comprise a light source and an overmolded optic, which encloses the light source. The overmolded optic may shape the light output, which is emitted by the aircraft light, when the light source is activated. Additionally, the overmolded optic may protect the light source from adverse external influences. The light output shaping capabilities of the overmolded optic are not always satisfactory.

It would be beneficial to provide an aircraft light whose optical system has enhanced light output shaping capabilities, while being easy to assemble.

According to an exemplary embodiment of the invention, an aircraft light comprises a support and a light source, which is arranged on the support.

The support may be a support board, in particular a printed circuit board comprising electrical lines for supplying electric power to the light source. The light source may be an LED, or it may comprise at least one LED.

The aircraft light further comprises a first optical element and a second optical element. The first and second optical elements are at least partially light transmissive, allowing light, which is emitted by the light source, to pass through the first and second optical elements.

<CIT> discloses an aircraft beacon light for being mounted to an aircraft fuselage. The aircraft beacon light includes: a support structure, having a carrier, and a stem for supporting the carrier and for spacing the carrier from the aircraft fuselage; and a lighting system, supported by the support structure. The lighting system has a plurality of light sources, light optics for re-directing at least a portion of the light emitted by the plurality of light sources, and a lens cover, with the plurality of light sources and the light optics being arranged between the carrier and the lens cover.

According to <CIT>, an aircraft beacon light includes a mounting plate having a central portion; a plurality of light sources arranged on the mounting plate around the central portion and facing away from the mounting plate; and a lens structure arranged over the plurality of light sources. The lens structure is configured to reflect a first portion of light emitted by the plurality of light sources laterally outwards via total internal reflection.

According to <CIT>, a lighting device includes a circuit board; an LED, soldered to the circuit board; an optical element, supported by the circuit board and positioned for re-directing at least part of the light in operation emitted by the LED; and a magnetic coupling between the circuit board and the optical element.

<CIT> discloses an exterior aircraft light unit, which includes a mounting structure, an LED arranged on the mounting structure, and an optical system, arranged on the mounting structure for creating an output light emission distribution of the exterior aircraft light unit. The optical system has, in a first cross-sectional plane extending through the LED, a first concave reflector and a second concave reflector, each of the first and second concave reflectors having a proximate end positioned adjacent to the mounting structure and a distal end positioned removed from the mounting structure. The first and second concave reflectors are arranged on opposite sides of the LED in the first cross-sectional plane, and a refractive optical element is arranged between the first and second concave reflectors in the first cross-sectional plane. The distal ends of both the first and second concave reflectors have back-tapered shapes, with the first and second concave reflectors curving towards each other at their distal ends.

The first and second optical elements being at least partially light transmissive means that each of the first and second optical elements comprises at least one portion, which is light transmissive. Neither the first optical element nor the second optical element needs to be light transmissive everywhere. In other words, each of the first and second optical elements may comprise at least one portion, which is opaque and not light transmissive.

The first optical element is arranged at least partially over the light source, covering the light source, and is fixed to the support board. The first and second optical elements are arranged so that the first optical element is interposed between the light source and the second optical element, so that at least a portion of light, which is emitted by the light source, when activated, passes through the first optical element and through the second optical element.

As a result of the first optical element being interposed between the light source and the second optical element, at least a portion of light, which is emitted by the light source, when the light source is activated, enters the first optical element, passes through the first optical element, and then enters the second optical element after leaving the first optical element. Thus, the term interposed is to be understood as the first optical element being interposed between the light source and the second optical element by being arranged in the path of light between the light source and the second optical element.

The first optical element being interposed between the light source and the second optical element may further include that the first optical element is arranged at a spatial position between the light source and the second optical element.

In an aircraft light according to the invention, the first optical element has a first engagement portion and the second optical element has a mating second engagement portion. When the second optical element is mounted to the first optical element, the first engagement portion and the second engagement portion establish a positive fit.

In consequence, the second optical element is fixed to the support board via the first optical element by establishing the positive fit between the first optical element and the second optical element.

Establishing the positive fit between the first optical element and the second optical element results in a positive mechanical engagement between the first and second optical elements.

The second engagement portion provided at the second optical element is in particular configured for fixing the second optical element to the first optical element by engaging with the first engagement portion of the first optical element, so that at least a portion of light, which is emitted by the light source, passes via the first optical element into the second optical element, when the second optical element is fixed to the first optical element.

In an aircraft light according to an exemplary embodiment of the invention, at least a portion of the light, which is emitted by the light source, passes a plurality of optical boundaries, which are formed by the inner and/or outer surfaces of the first and second optical elements.

The surfaces of the first and second optical elements may contact each other, forming an optical boundary between the first and second optical elements.

In an unclaimed example, instead of a direct contact between the first and second optical elements, an air filled gap may be formed between the outer surface of the first optical element and the inner surface of the second optical element, thus providing two optical boundaries, namely a first optical boundary between the first optical element and the air filled gap and a second optical boundary between the air filled gap and the second optical element.

The first and second optical elements may be formed so that they comprise portions, which contact each other, and that they comprise other portions, in which a gap is formed between the first and second optical elements.

By providing multiple optical boundaries along the path of the light from the light source through the first and second optical elements, the light from the light source may be refracted multiple times between the light source and the environment of the aircraft light. This may result in enhanced light output shaping capabilities of the aircraft light. In consequence, a desired light output of the aircraft light may be achieved with relatively small first and second optical elements. Thus, the dimensions of the aircraft light may be reduced, and a small but still efficient aircraft light may be provided.

Further, fixing the second optical element to the first optical element by establishing a positive fit between the first optical element and the second optical element may contribute to a convenient assembly of the aircraft light. It may avoid the need for using additional components for supporting and fixing the second optical element, such as screws. As a result, the mechanical structure of the aircraft light may be kept simple, and the costs for producing and assembling the aircraft light may be kept low.

In an embodiment, the first engagement portion and the second engagement portion establish a peripheral positive fit, such as a positive fit along the outer periphery of the first engagement portion, between the first optical element and the second optical element. Such a peripheral positive fit may enable an effective mounting and fixing of the second optical element to the first optical element. It may further allow for forming a hollow space between the first optical element and the second optical element, which is present towards the inside of said peripheral positive fit.

The formation of a hollow space, which may be filled with air, between the first optical element and the second optical element provides additional optical boundaries along the path of light, emitted by the light source. This may result in an even larger flexibility in the light output forming capabilities of the aircraft light.

In an embodiment, the positive fit may be continuous along the periphery of the first and second engagement portions.

In an alternative embodiment, the positive fit between the first and second engagement portions may be broken / interrupted, so that the first and second engagement portions comprise one or more gaps between a plurality of partial engagement portions, which are formed along the peripheries of the first and second engagement portions.

In an embodiment, at least one of the first optical element and the second optical element is at least partially elastic. In particular, at least one of the first optical element and the second optical element may be elastic at least at its engagement portion. At least one of the first optical element and the second optical element may in particular be at least partially or even fully made of a flexible material. An elasticity of the engagement portion may facilitate engaging the two engagement portions with each other, in particular by passing one of the engagement portions over the other engagement portion.

In an embodiment, the first optical element is at least partially made of a material comprising solidified liquid silicon rubber.

In an embodiment, the second optical element is made of a flexible material, in particular from a material comprising solidified liquid silicon rubber, or from a rigid material, such as polymethyl methacrylate (PMMA), polycarbonate (PC), or glass.

Using a flexible material may facilitate the assembly of the first and second optical elements. A second optical element, which is made from a rigid material, may provide enhanced protection against adverse external mechanical influences, such as mechanical impact.

In an embodiment, the first engagement portion has a so called "dovetail"-configuration, in which the first engagement portion comprises at least one outwards slanted first engagement surface, and the second engagement portion comprises at least one mating second engagement surface. The first and second engagement surfaces may abut against each other constituting a positive fit, which fixes the second optical element to the first optical element, when the first and second engagement portions are in engagement with each other.

In an alternative embodiment, the first engagement portion comprises at least one inwards slanted first engagement surface and the second engagement portion comprises at least one mating inwards slanted second engagement surface.

In an embodiment, the slanted first and second engagement surfaces are slanted at an angle α of between <NUM>° and <NUM>°, in particular at an angle α of between <NUM>° and <NUM>°, with respect to the support board. Slanting the first and second engagement surfaces at an angle within said value range has been found to provide a reliable mechanical connection between the first and second optical elements and to allow a convenient engagement and disengagement of the second engagement portion with / from the first engagement portion.

In an embodiment, the second optical element is arranged outside the first optical element and encompasses / surrounds the first optical element, when the second optical element is mounted to the first optical element.

In an alternative embodiment, the second optical element is arranged at least partially within the first optical element, so that the first engagement portion of the first optical element embraces the second engagement portion of the second optical element for fixing the second optical element to the first optical element.

In an embodiment, the first engagement portion has a first annular engagement surface and the second engagement portion has a second annular engagement surface. An engagement between first and second annular engagement surfaces may allow for a highly uniform distribution of the engagement forces around the engagement portions. Also, a highly uniform light output shaping around the periphery of the aircraft light may be achieved in this way.

In an embodiment, the first engagement portion has a plurality of substantially planar first engagement surfaces and the second engagement portion has a plurality of substantially planar second engagement surfaces. The first engagement surfaces may be arranged next to each other, forming a continuous or interrupted first engagement portion, which has a first polygonal configuration. The second engagement surfaces may be arranged next to each other, forming a continuous or interrupted second engagement portion, which has a second polygonal configuration, matching the configuration of the first engagement portion.

The polygonal configuration may be a triangular configuration, a rectangular configuration, in particular a quadratic configuration, a hexagonal configuration, an octagonal configuration or a polygonal configuration comprising five, seven or more than eight surfaces.

In an embodiment, the first and second optical elements may be formed as longitudinal structures, each comprising two longitudinal engagement surfaces, which extend in a stripe-like manner along a longitudinal direction.

In an embodiment, the first engagement portion is part of a light exit surface of the first optical element and the second engagement portion is part of a light entry surface of the second optical element. When the first and second engagement portions abut against each other, an optical interface may be formed between the first and second engagement portions, and light, which passes from the first optical element into the second optical element, may be refracted at said optical interface.

In an embodiment, the first optical element has a first refractive index, and the second optical element has a second refractive index, which is different from the first refractive index. The refraction - or a potential reflection - of the light may be controlled by adjusting the refractive indices of the first and second optical elements. The refractive indices may be adjusted by selecting the materials, which are used for producing the first and second optical elements.

Additionally or alternatively, a gap, in particular an air filled gap, may be formed between the first and second optical elements. The formation of such a gap may result in refracting light, which passes through the first and second optical elements, at a first optical interface, which is formed between the first optical element and the gap, and a second optical interface, which is formed between the gap and the second optical element. In such an embodiment, the refraction of the light may be controlled by adjusting the refraction indices of the first and second optical elements and/or by changing the width of the gap, which is formed between the first and second optical elements.

In an embodiment, at least one lens structure is formed in at least one of the first and second optical elements. The first optical element may comprise a first lens structure and/or the second optical element may comprise a second lens structure. By forming at least one lens structure in at least one of the first and second optical elements, the light output, which is emitted by the aircraft light, when the light source is activated, may be shaped with a high degree of design freedom. For example, the light output, which is emitted by the aircraft light, may be focussed very efficiently by passing the light through at least one lens structure, in particular by passing the light through two lens structures.

The lens structures may be refractive lens structures. The lens structures may also include reflective lens structures or reflective lens portions. In particular, a reflective lens structure, comprising at least one total internal reflection surface, may be formed in the second optical element.

In an embodiment, at least one of the first and second optical elements has rotational symmetry with respect to an axis of rotation. The light source may be positioned on said axis of rotation. Alternatively or additionally, the main direction of the light output, emitted by the aircraft light, may be oriented parallel to said axis of rotation.

The first optical element and/or the first engagement portion may be formed as a circular collar, which surrounds the light source.

In an embodiment, both, the first and second optical elements, have rotational symmetry, respectively. The first and second optical elements may be arranged coaxially with respect to each other on a common axis. Such a configuration may result in an aircraft light having rotational symmetry. Forming both, the first and second optical elements, with rotational symmetry may contribute to an effective engagement and disengagement of the first and second optical elements with respect to each other. It may further allow for providing a light output, which has rotational symmetry with respect to the common axis.

In an embodiment, a clearance is present between the second optical element and the support board, when the second optical element is mounted to the first optical element. Such a clearance may facilitate mounting the second optical element to the first optical element by allowing the second optical element to "overshoot", i.e. to move beyond, its final mounting position during the process of mounting the second optical element to the first optical element. Such an "overshooting" of the second optical element beyond its final position may allow the flexible portion(s) of the first and/or second optical element to deform effectively for allowing the first and second engagement portions to engage which each other.

The clearance between the second optical element and the support board may be in the range of between <NUM>,<NUM> and <NUM>,<NUM>, in particular in the range of between <NUM>,<NUM> and <NUM>,<NUM>, more particularly in the range of between <NUM>,<NUM> and <NUM>,<NUM>.

In a virtual plane, which is oriented parallel to the support board, the first optical element may have a diameter in the range of between <NUM> and <NUM>, in particular a diameter in the range of between <NUM> and <NUM>, more particularly a diameter of between <NUM> and <NUM>.

In a direction, which is oriented perpendicular to the support board, the first optical element may have a height in the range of between <NUM> and <NUM>, in particular a height in the range of between <NUM> and <NUM>, more particularly a height of about <NUM>.

In the virtual plane, which is oriented parallel to the support board, the second optical element may have a diameter in the range of between <NUM> and <NUM>, in particular a diameter in the range of between <NUM> and <NUM>, more particularly a diameter of about <NUM>.

In a direction, which is oriented perpendicular to the support board, the second optical element may have a height in the range of between <NUM> and <NUM>, in particular a height in the range of between <NUM> and <NUM>, more particularly a height in the range of between <NUM> and <NUM>.

The minimum wall thickness of the first and second optical elements may be in the range of between <NUM> and <NUM>, in particular in the range of between <NUM> and <NUM>.

The aircraft light may be an exterior aircraft light, which is mounted to the outside of an aircraft, in particular to a fuselage, to a wing, to a stabilizer or to a running gear of the aircraft. The aircraft light may in particular be at least one of a navigation light, a white anti-collision strobe light, a red-flashing beacon light, a take-off light, a taxi light, a runway turn-off light, a landing light, a logo light, a cargo loading light, a wing scan light, an engine scan light, and a search light. The expression of the aircraft light being at least one of a navigation light, a white anti-collision strobe light, a red-flashing beacon light, a take-off light, a taxi light, a runway turn-off light, a landing light, a logo light, a cargo loading light, a wing scan light, an engine scan light, and a search light means that the aircraft light has the functionality of at least one of a navigation light, a white anti-collision strobe light, a red-flashing beacon light, a take-off light, a taxi light, a runway turn-off light, a landing light, a logo light, a cargo loading light, a wing scan light, an engine scan light, and a search light. The aircraft light may be a multi-purpose exterior aircraft light, combining any subset of the stated functionalities.

The aircraft light may also be an interior aircraft light, which is mounted inside an aircraft. The aircraft light may in particular be at least one of a cabin illumination light, a washroom illumination light, a galley illumination light, an aisle guidance light, a passenger reading light, and an exit sign light. The expression of the aircraft light being at least one of a cabin illumination light, a washroom illumination light, a galley illumination light, an aisle guidance light, a passenger reading light and an exit sign light means that the aircraft light has the functionality of at least one of a cabin illumination light, a washroom illumination light, a galley illumination light, an aisle guidance light, a passenger reading light and an exit sign light. The aircraft light may be a multi-purpose interior aircraft light, combining any subset of the stated functionalities.

Exemplary embodiments of the invention further include an aircraft, such as an airplane or a rotorcraft, which is equipped with at least one aircraft light according to an exemplary embodiment of the invention. The additional features, modifications and effects, described above with respect to the exemplary embodiments of the aircraft light, apply to the aircraft in an analogous manner. The aircraft may be a passenger aircraft, such as a passenger airplane. The rotorcraft may be a helicopter or an unmanned aerial vehicle.

Exemplary embodiments of the invention also include a method of assembling an aircraft light according to an exemplary embodiment of the invention, wherein the method includes elastically deforming at least one of the first engagement portion of the first optical element and the second engagement portion of the second optical element and mounting and fixing the second optical element to the first optical element by establishing a positive fit between the first and second engagement portions of the first and second optical elements.

In an embodiment, the method of assembling an aircraft light further includes tilting and/or rotating the second optical element with respect to the first optical element for introducing the first engagement portion at least partially into the second optical element and establishing a positive fit between the first and second engagement portions of the first and second optical elements.

Further exemplary embodiments of the invention are described below with respect to the accompanying drawings, wherein:.

<FIG> depicts a schematic cross-sectional view through an aircraft light <NUM> according to an exemplary embodiment of the invention.

The aircraft light <NUM> comprises a light source <NUM>, which is arranged on a support board <NUM>, for example a circuit board, in particular a printed circuit board ("PCB").

The light source <NUM> may be an LED, or it may comprise an LED or a plurality of LEDs.

The aircraft light <NUM> further comprises a first optical element <NUM>, which is at least partially light transmissive. The first optical element <NUM> is supported by the support board <NUM>. The first optical element <NUM> is in particular fixed to the support board <NUM>. The first optical element <NUM> is arranged at least partially over the light source <NUM>, covering the light source <NUM>, so that at least a portion of the light, which is emitted by the light source <NUM>, when it is activated, passes through the first optical element <NUM>.

<FIG> depicts an enlarged schematic cross-sectional view of the light source <NUM>, the first optical element <NUM> and the support board <NUM>, and <FIG> depicts a schematic perspective view thereof.

The aircraft light <NUM> also comprises a second optical element <NUM>, which is at least partially light transmissive.

The first and second optical elements <NUM>, <NUM> being at least partially light transmissive means that each of the first and second optical elements <NUM>, <NUM> comprises at least one portion, which is light transmissive. Neither the first nor the second optical element <NUM>, <NUM> needs to be light transmissive everywhere. In other words, each of the first and second optical elements <NUM>, <NUM> may comprise at least one portion, which is not light transmissive.

<FIG> depicts a schematic cross-sectional view of the second optical element <NUM>. The second optical element <NUM> has a dome-like shape with an underside 10a and a convex light emission surface 10b, which extends in a dome-shape manner from the outer periphery of the underside 10a. The underside 10a of the second optical element <NUM> faces the support board <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>, as it is depicted in <FIG>.

The first optical element <NUM> has a first engagement portion <NUM> (see <FIG>), and the second optical element <NUM> has a mating second engagement portion <NUM>. The first engagement portion <NUM> and the second engagement portion <NUM> are configured for establishing a positive fit between the first optical element <NUM> and the second optical element <NUM>. The positive fit results in a positive mechanical engagement between the first optical element <NUM> and the second optical element <NUM>, which fixes the second optical element <NUM> to the first optical element <NUM>. In consequence, the second optical element <NUM>, when fixed to the first optical element <NUM>, is indirectly fixed to the support board <NUM> via the first optical element <NUM>.

As illustrated in <FIG>, the first optical element <NUM> is interposed between the light source <NUM> and the second optical element <NUM>, when the second optical element <NUM> is fixed to the first optical element <NUM>.

With the first optical element <NUM> being interposed between the light source <NUM> and the second optical element <NUM>, at least a portion of the light, which is emitted by the light source <NUM>, when it is operated, enters the first optical element <NUM>, passes through the first optical element <NUM>, and then enters the second optical element <NUM> after leaving the first optical element <NUM>. Thus, the term interposed is to be understood as the first optical element <NUM> being arranged in the path of light between the light source <NUM> and the second optical element <NUM>.

The first optical element <NUM> being interposed between the light source <NUM> and the second optical element <NUM> may include that the first optical element <NUM> is arranged at a spatial position between the light source <NUM> and the second optical element <NUM>, as it is depicted in <FIG>.

The first optical element <NUM> may, in combination with the support board <NUM>, surround and/or enclose the light source <NUM>, as it is depicted in <FIG>, and the second optical element <NUM> may, in combination with the support board <NUM>, surround and/or enclose the first optical element <NUM>, as it is depicted in <FIG>. As a result, the light source <NUM> and/or the first optical element <NUM> are separated and protected from the environment by the second optical element <NUM>. The second optical element <NUM> may in particular be configured for protecting the light source <NUM> and/or the first optical element <NUM> from mechanical impact and/or from other adverse influences from the environment, such as water, dirt, and moisture.

The complete enclosure of the light source <NUM> and/or the first optical element <NUM> by the second optical element <NUM>, however, is an optional feature. Embodiments in which the light source <NUM> and/or the first optical element <NUM> are not completely enclosed by the second optical element <NUM> are also considered as comprising a first optical element <NUM>, which is interposed between the light source <NUM> and the second optical element <NUM>.

The support board <NUM> may be formed as and/or may be attached to a heat sink <NUM> (see <FIG>), which is configured for dissipating heat, which is produced when the light source <NUM> is operated.

In the exemplary embodiment depicted in the figures, the first engagement portion <NUM> has a so called "dovetail"-configuration, in which the first engagement portion <NUM> is slanted outwards with respect to a central axis through the light source <NUM>. The first engagement portion <NUM> includes at least one outwards slanted first engagement surface <NUM>. The second engagement portion <NUM> comprises at least one mating outwards slanted second engagement surface <NUM>, which is formed as part of an undercut within the second optical element <NUM> (see <FIG> and <FIG>).

In an alternative configuration, which is not explicitly shown in the figures, the first engagement portion <NUM> may comprise at least one inwards slanted first engagement surface, and the second engagement portion <NUM> may comprises at least one mating inwards slanted second engagement surface.

In the exemplary embodiment depicted in <FIG>, the second optical element <NUM> is arranged outside the first optical element <NUM> and encompass the first optical element <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>.

In an alternative embodiment, which is not explicitly shown in the figures, the second optical element <NUM> may be arranged partially within the first optical element <NUM>, so that the first engagement portion <NUM> of the first optical element <NUM> embraces the second engagement portion <NUM> of the second optical element <NUM> for fixing the second optical element <NUM> to the first optical element <NUM>.

In the depicted exemplary embodiment of <FIG>, the slanted first and second engagement surfaces <NUM>, <NUM> may be slanted at an angle α of between <NUM>° and <NUM>°, in particular at an angle of between <NUM>° and <NUM>°, with respect to the support board <NUM>.

As best seen in the perspective view, which is depicted in <FIG>, the first engagement portion <NUM> may be formed as a circular collar, surrounding the light source <NUM>.

In such a configuration, the first and second optical elements <NUM>, <NUM> may have rotational symmetry with respect to an axis A, which extends perpendicular to the support board <NUM>. The light source <NUM> may be located on the axis A at the center of the aircraft light <NUM>.

In the exemplary embodiment depicted in <FIG>, the first and second engagement surfaces <NUM>, <NUM> are annular engagement surfaces. They extend continuously around the center of the aircraft light <NUM>. The first and second annular engagement surfaces <NUM>, <NUM> may in particular extend along a circle, which is centered around the axis A. Alternatively, the first and second annular engagement surfaces <NUM>, <NUM> may extend along an elliptical path or along another curved path, as long as the curved shapes of the first and second annular engagement surfaces <NUM>, <NUM> match.

In an alternative embodiment, which is not explicitly shown in the figures, the first optical element <NUM> may have a polygonal periphery. In such an embodiment, the first engagement portion <NUM> may include a plurality of substantially planar first engagement surfaces, which, in combination, form the polygonal periphery of the first optical element <NUM>.

In such an embodiment, the second engagement portion <NUM> may be formed with an equal number of mating substantially planar second engagement surfaces.

When the second engagement portion <NUM> is mounted to the first engagement portion <NUM>, the first engagement surfaces of the first engagement portion <NUM> may engage with the corresponding second engagement surfaces, which are formed at the second engagement portion <NUM>.

In yet another embodiment, the first and second optical elements <NUM>, <NUM> may be formed as longitudinal structures, each comprising two longitudinal engagement surfaces, which extend in a stripe-like manner along a longitudinal direction.

In the embodiment shown in <FIG>, a continuous contact is established between the first and second engagement surfaces <NUM>, <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>.

In alternative embodiments, the first and second engagement portions <NUM>, <NUM> may comprise a plurality of first and second engagement surfaces <NUM>, <NUM>, respectively. Gaps may be formed between adjacent engagement surfaces <NUM>, <NUM>, such that, contrary to the exemplary embodiment depicted in <FIG>, no continuous engagement is established between the first and second optical elements <NUM>, <NUM> along the circumference of the first and second engagement portions <NUM>, <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>. Instead, in such a configuration, a plurality of contact zones, at which the first and second engagement portions <NUM>, <NUM> engage with each other, may be formed along the circumference of the first and second engagement portions <NUM>, <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>.

The at least one first engagement surface <NUM> may be or may be part of a light exit surface of the first optical element <NUM>, and the second engagement surface <NUM> may be or may be part of a light entry surface of the second optical element <NUM>.

The portions, in which the first engagement surface <NUM> and the second engagement surface <NUM> of the first and second optical elements <NUM>, <NUM> contact each other, constitute optical boundaries, which may cause a refraction of the light, which is emitted by the light source <NUM> and passes through the first and second optical elements <NUM>, <NUM>.

The first optical element <NUM>, which is depicted in <FIG>, comprises an inner portion <NUM>, which is formed in a dome-like shape covering the light source <NUM>. A gap <NUM> is formed between the inner portion <NUM> and the circular first engagement portion <NUM>, which surrounds the inner portion <NUM> in a distance a.

The distance a between the inner portion <NUM> and the annular first engagement portion <NUM> may be in the range of between <NUM> and <NUM>.

Said gap <NUM> between the inner portion <NUM> and the annular first engagement portion <NUM> results in the formation of a hollow, usually air filled, space <NUM> between the first and second optical elements <NUM>, <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>.

The surfaces of the first and second optical elements <NUM>, <NUM>, which define the hollow space <NUM>, provide additional optical boundaries for refracting light, which is emitted by the light source <NUM> and passes through the first optical element <NUM>, through the hollow space <NUM>, and through the second optical element <NUM>.

The surfaces of the first and second optical elements <NUM>, <NUM>, which define the hollow space <NUM> and constitute the optical boundaries, may be shaped such that the refraction of the light at the optical boundaries results in a desired light output, which is emitted by the aircraft light <NUM>, when the light source <NUM> is activated. An example of a light output of an aircraft light <NUM> according to an exemplary embodiment of the invention is indicated schematically by the light rays <NUM> depicted in <FIG>.

The first optical element <NUM> has a first refractive index and the second optical element <NUM> has a second refractive index. The refractive indices of the first and second optical elements <NUM>, <NUM> are defined by the materials, which are used for forming the first and second optical elements <NUM>, <NUM>. For controlling and enhancing the refraction of light at the optical boundaries of the first and second optical elements <NUM>, <NUM>, the materials of the first and second optical elements <NUM>, <NUM> may be chosen so that the second refractive index differs from the first refractive index.

The inner portion <NUM> or another portion of the first optical element <NUM> may be formed as a first lens structure for focussing the light, which passes through the first optical element <NUM>. Additionally or alternatively, the second optical element <NUM> may be formed as a second lens structure.

The first and second optical elements <NUM>, <NUM> and, in particular the lens structures formed in the first and second optical elements <NUM>, <NUM>, may be refractive optical elements. The first and second optical elements <NUM>, <NUM> may also comprise at least one total internal reflection surface, which is configured such that the light, which is incident on said surface from inside the respective optical element, does not exit from the optical element, but is totally reflected at said at least one total internal reflection surface.

At least one of the first optical element <NUM> and the second optical element <NUM> may be made at least partly of an elastic material. In particular, at least one of the first and second engagement portions <NUM>, <NUM> of the first and second optical elements <NUM>, <NUM> may be made from an elastic material, in order to enable deforming at least one of the first and second engagement portions <NUM>, <NUM>.

Deforming at least one of the first and second engagement portions <NUM>, <NUM> may allow for or facilitate a convenient engaging of the first and second engagement portions <NUM>, <NUM> with each other.

In the exemplary embodiment depicted in <FIG>, the second optical element <NUM> may be fixed to the first optical element <NUM> by deforming at least one of the first and second engagement portions <NUM>, <NUM>, in order to allow passing the second engagement portion <NUM> over the first engagement portion <NUM>, so that the first engagement portion <NUM> may be introduced into the undercut, which is formed as part of the second engagement portion <NUM>.

The first optical element <NUM> may, for example, be at least partially made of a material comprising a solidified liquid silicon rubber. The second optical element <NUM> may, for example, be at least partially made of a material comprising a solidified liquid silicon rubber, or from a rigid material, such as polymethyl methacrylate (PMMA), polycarbonate (PC), or glass.

The dimensions of the first and second optical elements <NUM>, <NUM> may be set such that there is a clearance <NUM>, i.e. a vertical gap, between the underside 10a of the second optical element <NUM> and the support board <NUM>, when the second optical element <NUM> is mounted to the first optical element <NUM>. Such a clearance <NUM> may make the mounting of the second optical element <NUM> to the first optical element <NUM> easier by allowing the second optical element <NUM> to "overshoot" its final mounted position during the process of mounting the second optical element <NUM> to the first optical element <NUM>. Such an "overshooting" of the second optical element <NUM> beyond its final position may help the flexible portion(s) of the first and second optical elements <NUM>, <NUM> to deform sufficiently for allowing the first and second engagement portions <NUM>, <NUM> to engage which each other.

The clearance <NUM> between the second optical element <NUM> and the support board may be in the range of between <NUM>,<NUM> and <NUM>,<NUM>, in particular in the range of between <NUM>,<NUM> and <NUM>,<NUM>, more particularly in the range of between <NUM>,<NUM> and <NUM>,<NUM>.

In a virtual plane, which is oriented parallel to the support board <NUM>, the first optical element <NUM> may have a diameter D<NUM> in the range of between <NUM> and <NUM>, in particular a diameter D<NUM> in the range of between <NUM> and <NUM>, more particularly a diameter D<NUM> of between <NUM> and <NUM>.

In a direction, which is oriented perpendicular to the support board <NUM>, i.e. in a direction, which is parallel to the axis A, the first optical element <NUM> may have a height H<NUM> in the range of between <NUM> and <NUM>, in particular a height H<NUM> in the range of between <NUM> and <NUM>, more particularly a height H<NUM> of about <NUM>.

The inner portion <NUM> of the first optical element <NUM> may have a diameter b in the range of between <NUM> and <NUM>, in particular a diameter b in the range of between <NUM> and <NUM>, more particularly a diameter b of about <NUM>.

In a virtual plane, which is oriented parallel to the support board <NUM>, the second optical element <NUM> may have a diameter D<NUM> in the range of between <NUM> and <NUM>, in particular a diameter D<NUM> in the range of between <NUM> and <NUM>, more particularly a diameter D<NUM> of about <NUM>.

In a direction, which is oriented perpendicular to the support board <NUM>, i.e. in a direction, which is parallel to the axis A, the second optical element <NUM> may have a height H<NUM> in the range of between <NUM> and <NUM>, in particular a height H<NUM> in the range of between <NUM> and <NUM>, more particularly a height H<NUM> in the range of between <NUM> and <NUM>.

The minimum wall thickness d of the first and second optical elements <NUM>, <NUM> may be in the range of between <NUM> and <NUM>, in particular in the range of between <NUM> and <NUM>.

<FIG> shows a schematic top view of an aircraft <NUM>, in particular of a passenger air plane <NUM>, from a position above the aircraft <NUM>. The aircraft <NUM> is equipped with a variety of exterior aircraft lights <NUM>-<NUM>.

Each of the exterior aircraft lights <NUM>-<NUM> may be provided as an aircraft light <NUM> according to an exemplary embodiment of the invention, as it has been described before. However, not all of the exterior aircraft lights <NUM>-<NUM> need to be aircraft lights <NUM> according to exemplary embodiments of the invention. The aircraft <NUM> may in particular comprise a mixture of exterior aircraft lights according to exemplary embodiments of the invention and other types of exterior aircraft lights.

The exemplary aircraft <NUM> depicted in <FIG> is equipped with three navigation lights <NUM>, two logo lights <NUM>, two wing scan lights <NUM>, two engine scan lights <NUM>, two runway turnoff lights <NUM>, two cargo loading lights <NUM>, three white anti-collision strobe lights <NUM>, two red-flashing anti-collision beacon lights <NUM>, a landing light <NUM>, and a take-off light <NUM>.

It is pointed out that these kinds of lights and their numbers are exemplary only. The aircraft <NUM> does not need to be equipped with all the exterior aircraft lights <NUM>-<NUM>, which are depicted in <FIG>, and the aircraft <NUM> may have additional lights, such as taxi lights, which are not shown in <FIG>.

The three navigation lights <NUM> are positioned in the left and right wing tips <NUM> as well as in the tail <NUM> of the aircraft <NUM>. In normal flight conditions, each one of the navigation lights <NUM> emits light in one of the colors green, red and white, thus indicating to the aircraft environment if they are looking at the port side, starboard side or tail side of the aircraft <NUM>. The navigation lights <NUM> are normally switched on during all phases of the flight and in all flight conditions.

The logo lights <NUM> are directed to the vertical stabiliser <NUM> of the aircraft <NUM> and are provided for illuminating the same, in particular for illuminating the logo (not shown), which is commonly provided on the vertical stabiliser <NUM>. The logo lights <NUM> are normally switched on for the entire duration of the flight during night flights. It is also possible that the logo lights <NUM> are only used during taxiing on the airport and are normally switched off during the flight.

The wing scan lights <NUM> and the engine scan lights <NUM> are positioned on the left and right sides of the aircraft fuselage <NUM>, in front of the roots of the wings <NUM> of the aircraft <NUM>. The wing scan lights <NUM> and the engine scan lights <NUM> are normally off during the flight and may be switched on periodically or upon reasonable cause by the pilots or by the aircrew, in order to check the wings <NUM> and the engines <NUM> of the aircraft <NUM>.

The runway turn-off lights <NUM> are positioned in the roots of the wings <NUM>. They are directed forwards and are normally switched off during the flight and switched on during taxiing, at least at night. The cargo loading lights <NUM> are positioned on the left and right sides of the aircraft fuselage <NUM>, behind the wings <NUM> and in front of the tail structure of the aircraft <NUM>. They are normally switched off during the flight of the aircraft <NUM>.

The white anti-collision strobe lights <NUM> are positioned in the left and right wing tips <NUM> as well as at the tail <NUM> of the aircraft <NUM>. The white anti-collision strobe lights <NUM> emit respective sequences of white light flashes during normal operation of the aircraft <NUM>. It is also possible that the white anti-collision strobe lights <NUM> are only operated during night and in bad weather conditions.

The anti-collision beacon lights <NUM> are positioned on the top and the bottom of the aircraft fuselage <NUM>. They are arranged at the height of the wings <NUM> in the longitudinal direction of the aircraft <NUM>. While one of the anti-collision beacon lights <NUM> is disposed on the top of the aircraft fuselage <NUM>, the other one of the anti-collision beacon lights <NUM> is disposed on the bottom of the aircraft fuselage <NUM> and is therefore shown in phantom. The anti-collision beacon lights <NUM> are normally switched on during the flight. Their output is perceived as a sequence of red light flashes in a given viewing direction.

The landing light <NUM> and the take-off light <NUM> are attached to the front running gear (not shown) of the aircraft <NUM>, which is normally stored within the aircraft fuselage <NUM> and is deployed during landing, taxiing and take off. As the landing light <NUM> and the take-off light <NUM> are also arranged on the bottom of the aircraft <NUM>, they are also shown in phantom in <FIG>.

<FIG> depicts a schematic cut-open view of an aircraft <NUM> in accordance with an exemplary embodiment of the invention, depicting a cockpit <NUM> and a passenger cabin <NUM>, which is also referred to as aircraft passenger cabin <NUM>.

The aircraft passenger cabin <NUM> is equipped with a plurality of passenger seats <NUM>. The passenger seats <NUM> are arranged next to each other forming a plurality of passenger seat rows. Each passenger seat row comprises two groups of passenger seats <NUM>, respectively including three passenger seats <NUM>. The two groups of passenger seats <NUM> are separated from each other by a center aisle <NUM>, which extends along a longitudinal axis L of the aircraft <NUM>.

Smaller aircraft may comprise less then three passenger seats <NUM> in each group of passenger seats <NUM>. Larger aircraft <NUM> may comprise more than two groups of passenger seats <NUM> in each row, which are separated by a plurality of aisles <NUM> extending parallel to each other along or parallel to the longitudinal axis L of the aircraft <NUM>.

The aircraft passenger cabin <NUM>, which is depicted in <FIG>, is further equipped with four lavatories 208a-208d. The lavatories 208a-208d are provided at four locations within the aircraft passenger cabin <NUM>. A first lavatory 208a is located at the front portside end of the aircraft passenger cabin <NUM>, a second lavatory 208b is located at the front starboard end of the aircraft passenger cabin <NUM>, a third lavatory 208c is located at the rear portside end of the aircraft passenger cabin <NUM>, and a fourth lavatory 208d is located at the rear starboard end of the aircraft passenger cabin <NUM>. Additionally or alternatively, lavatories 208a-208d may be provided at other locations of the aircraft passenger cabin <NUM> as well.

The aircraft passenger cabin <NUM> is further equipped with a galley <NUM>, in order to allow for preparing meals and drinks for the passengers.

Interior aircraft lights according to exemplary embodiments of the invention may be installed within the passenger cabin <NUM> as cabin illumination lights <NUM> for illuminating the passenger cabin <NUM>.

At least one of the lavatories 208a-208d may be provided with an interior aircraft light according to an exemplary embodiment of the invention, which in this case serves as a washroom illumination light <NUM>.

At least one interior aircraft light according to an exemplary embodiment of the invention may be employed in the galley <NUM> as a galley illumination light <NUM>. Interior aircraft lights according to exemplary embodiments of the invention may further be employed as aisle guidance lights <NUM>, which extend along the aisle <NUM> between the passenger seats <NUM>, and/or as exit sign lights <NUM> for indicating the exits of the aircraft <NUM>.

Interior aircraft lights according to exemplary embodiments of the invention may also be installed as individually switchable personal passenger reading lights <NUM> above the passenger seats <NUM>.

Claim 1:
Aircraft light (<NUM>) comprising:
a support board (<NUM>);
a light source (<NUM>), arranged on the support board (<NUM>);
a first at least partially light transmissive optical element (<NUM>), which is arranged over the light source (<NUM>) and which is fixed to the support board (<NUM>); and
a second at least partially light transmissive optical element (<NUM>);
wherein the first optical element (<NUM>) is interposed between the light source (<NUM>) and the second optical element (<NUM>);
wherein the first optical element (<NUM>) has a first engagement portion (<NUM>) and the second optical element (<NUM>) has a mating second engagement portion (<NUM>);
wherein the first engagement portion (<NUM>) and the mating second engagement portion (<NUM>) establish a positive fit between the first optical element (<NUM>) and the second optical element (<NUM>); and
wherein at least a portion of light (<NUM>), which is emitted by the light source (<NUM>) in operation, passes through the first optical element (<NUM>) and through the second optical element (<NUM>).