Light pipe assembly

A light pipe assembly includes a lamp assembly and a light pipe. The lamp assembly has a housing that holds a light source configured to emit light. The light pipe is elongated between an attachment end and an opposing distal end. The attachment end is received in the housing of the lamp assembly. The light pipe receives light emitted by the light source. Additionally, the light pipe includes surface elements that are configured to permit the light to emanate from the light pipe between the attachment and distal ends. The surface elements are arranged in a pattern that provides a predetermined distribution of light emanating from the light pipe.

BACKGROUND OF THE INVENTION

A light pipe is a typically cylindrical, transparent structure through which light is channeled or transmitted along the longitudinal axis of the light pipe by total internal reflection. Total internal reflection prevents the light from passing from inside the light pipe to outside of the light pipe. Total internal reflection occurs when light impinges on an interface between the light pipe and the atmosphere surrounding the light pipe at an angle that is greater than a critical angle. The critical angle is a function of the indices of refraction for the medium of the light pipe and the medium of the surrounding atmosphere.

The light transmitted by light pipes is generated by a light source. The light source is usually contained in a lamp assembly to which the light pipe is fastened. A typical lamp assembly includes a housing that contains a light source such as a light emitting diode (“LED”). The light pipe should be secured to the lamp assembly to prevent accidental separation of the light pipe from the lamp assembly. In many applications where light pipes are used, the space to accommodate the light pipe and associated lamp assembly is limited. For example, the space available for the light pipe and lamp assembly in interior automobile lighting may be limited. Therefore, typically very little space is available for structures and features that secure the light pipe to the lamp assembly. Current known securing structures include mechanisms such as clamps and epoxies. But, because the light pipe typically has a smooth, cylindrical exterior, the light pipe may easily disconnect from a lamp assembly when known securing structures are used to secure the light pipe to the lamp assembly.

Known light pipes include a white strip or other surface element on the light pipe or inside the light pipe that reflects light impinging on the surface element. At least some of the reflected light strikes the interface between the outside surface of the light pipe and the surrounding atmosphere at an angle that is less than the critical angle of the light pipe-atmosphere interface. This light emanates from the light pipe as emitted light. In order to direct the reflected light in the proper direction, the strip or surface element need to be properly aligned with respect to the lamp assembly.

As the light emanates from the light pipe, the intensity of the emitted light may decrease along the length of the light pipe. For example if too much light escapes from the light pipe in locations near a light source, the light emanating from an opposing end of the light pipe may not be as bright or intense as the light emanating from other parts of the light pipe. Such an uneven distribution of emitted light may be undesirable.

Thus, a need exists to provide a light pipe that more evenly emits light along the length of the light pipe. Moreover, a need also exists for a coupling between the light pipe and lamp assembly that orients the light pipe with respect to the lamp assembly.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a light pipe assembly is provided. The light pipe assembly includes a lamp assembly and a light pipe. The lamp assembly has a housing that holds a light source configured to emit light. The light pipe is elongated between an attachment end and an opposing distal end. The attachment end is received in the housing of the lamp assembly. The light pipe receives light emitted by the light source. Additionally, the light pipe includes surface elements that are configured to permit the light to emanate from the light pipe between the attachment and distal ends. The surface elements are arranged in a pattern that provides a predetermined distribution of light emanating from the light pipe.

In another embodiment, another light pipe assembly is provided. The light pipe assembly includes a lamp assembly and a light pipe. The lamp assembly includes a housing and a light source. The housing has a mating portion. The light source is configured to emit light. The light pipe extends between an attachment end and an opposing distal end. The light pipe is configured to receive light emitted by the light source. The attachment end of the light pipe is coupled with the mating portion of the housing and includes orientation features to align the light pipe with respect to the housing and to secure the light pipe to the housing.

In another embodiment, a light pipe assembly includes a lamp assembly and a light pipe. The lamp assembly has a housing that holds a light source configured to emit light. The light pipe extends between an attachment end and an opposing distal end. The attachment end is received in the housing of the lamp assembly. The light pipe receives light emitted by the light source and includes light-reflective surface elements. The surface elements reflect the light received by the light pipe in directions out of the light pipe between the attachment and distal ends. The surface elements include a plurality of reflective strips interconnected by a reflective line.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is an isometric view of a light pipe assembly100implemented in accordance with one embodiment. The light pipe assembly100includes a light pipe102and a lamp assembly104. The light pipe102is elongated along a longitudinal axis110between an attachment end112and a distal end114. The light pipe102may be formed from a light transmissive material, such as an acrylic material. In one embodiment, the light pipe102is an extruded cylindrical rod formed of a translucent acrylic material. Other shapes of the light pipe102may be used, including shapes having bends or undulations in the general elongated shape of the light pipe102shown inFIG. 1. The diameter or other cross-sectional dimensions of the light pipe102may depend on the particular application to which the light pipe102is used. For example, one or more embodiments described herein may be particularly suitable for automotive applications and for use with household appliances. Such applications may require relatively small diameters of the light pipe102.

The lamp assembly104includes a light source106held in a housing108. The light source106includes one or more individual sources of light that emit the light into the light pipe102. For example, the light source106may be a single light emitting diode or include a plurality of light emitting diodes. A single light source106may include more than one type of light generating component. The housing108may be formed from a dielectric material such as a polymer. Alternatively, the housing108may be formed from a metal. The attachment end112of the light pipe102is received in the housing108to secure the light pipe102to the lamp assembly104and to orient the light pipe102with respect to the lamp assembly104such that light emitted by the light pipe102is directed in a desired or predetermined direction. The light source106emanates light toward the attachment, end112of the light pipe102. The light is transmitted through the light pipe102generally from the attachment end112toward the distal end114.

A band or pattern116of individual surface elements118is provided on the light pipe102. The surface elements118may be separated from one another such that the surface elements118are not interconnected with one another. The surface elements118may be printed or otherwise adhered to an outer surface120of the light pipe102. Alternatively, the surface elements118may be formed on the inside of the light pipe102. For example, the surface elements118may be formed inside the light pipe102as the light pipe102is extruded. In one embodiment, the surface elements118reflect the light that impinges on the surface elements118. For example, at least some of the light that is transmitted through the light pipe102may strike the surface elements118and be reflected or scattered by the surface elements118. The surface elements118reflect the light and may cause the light to emanate from the light pipe102as emitted light122. The light122may emanate from the light pipe102in a direction transverse to the longitudinal axis110. The emitted light122may emanate from the light pipe102in a variety of directions, including from a side opposing the surface elements118. For example, the emitted light122may exit the light pipe102in directions substantially opposite the surface elements118. In the example shown inFIG. 1, the emitted light122includes light that emanates from a surface of the light pipe102that is disposed 180 degrees from the surface elements118, or on an opposite side of the approximately circular cross-sectional shape of the light pipe102.

The pattern116of the surface elements118may be provided along the length of the light pipe102in one or more of a shape and distribution in order to provide a desired distribution of the light122emanating from the light pipe102. For example, the pattern116may cause the surface elements118to reflect the light122out of the light pipe102in a projected distribution124. The projected distribution124of the light122is shown schematically inFIG. 1and may take alternative sizes and/or shapes. The projected distribution124may be defined by a length126and a projection angle128. The length126of the distribution124represents the distance along the light pipe102in a direction parallel to the longitudinal axis110that the light122emanates from the light pipe102in directions transverse to the longitudinal axis110. The projection angle128is the angle subtended by the distribution124, or the radial distance that the projection angle128extends over the surface120of the light pipe102.

Alternatively, the surface elements118may include light transmissive elements having an index of refraction that differs from the index of refraction of the light pipe102. The interfaces between the surface elements118and the light pipe102may alter the critical angle required for total internal reflection. For example, the surface elements118may have an index of refraction that increases the critical angle at the interface between the light pipe102and the surface elements118. Increasing the critical angle may reduce the amount of light that is internally reflected in the light pipe102and may increase the amount of light that emanates from the light pipe102. The light that is refracted by the surface elements118may emanate from the light pipe102through the surface elements118. For example, the emanating refracted light may exit the light pipe102proximate the same side of the light pipe102on which the surface elements118are disposed.

In one embodiment, the size and/or spatial density of the surface elements118may change in the pattern116. For example, the size and/or spatial density of the surface elements18may increase in the pattern116between the attachment and distal ends112,114. The spatial density of the surface elements118may be defined as the number of surface elements118per unit of surface area of the light pipe102. As described below, the surface elements118located in the pattern116in locations proximate to the attachment end112may be smaller, and/or the density of the surface elements118may be less, when compared to the size and/or spatial density of the surface elements118in locations proximate to the distal end114. By controlling the size and/or density of the surface elements118in the pattern116, the amount of emanated light122may be controlled along the longitudinal axis110of the light pipe102. For example, less light may emanate from the light pipe102in locations near the attachment end112where the surface elements118are smaller and/or are provided in a lesser spatial density. The size and/or density of the surface elements118increases along the longitudinal axis110of the light pipe102toward the distal end114, to compensate for the reduced amount of light impinging on each surface element118. For example, a lesser amount of the light transmitted within the light pipe102may be reflected by the surface elements118and emanate from the light pipe102near the attachment end112than the surface elements118near the distal end114. The size and/or density of the surface elements118may be tailored to provide an approximately uniform distribution of light122emanating from the light pipe102along the longitudinal axis110between the attachment and distal ends112,114. For example, the light122may emanate from the light pipe102such that no appreciable gradient in the intensity of the emitted light122exists.

FIG. 2is a plan view of a pattern200of surface elements202arranged in accordance with one embodiment. The pattern200of the surface elements202may be similar to the pattern116(shown inFIG. 1) of the surface elements118(shown inFIG. 1). The pattern200may be disposed on the curved outer surface120(shown inFIG. 1) of the light pipe102(shown inFIG. 1). The pattern200extends between opposing ends204,206. In one embodiment, the pattern200may be disposed on the light pipe102so that the first end204is located proximate to the attachment end112and the second end206is located proximate to the distal end114. An area on the outer surface120of the light pipe102between the first end204and the attachment end112and/or between the second end206and the distal end114may not include any surface elements202. For example, the pattern200may extend along a length208that is less than the distance between the attachment and distal ends112,114in a direction parallel to the longitudinal axis110(shown inFIG. 1). Adjusting the length208of the pattern200may alter the length126(shown inFIG. 1) of the projected distribution124(shown inFIG. 1) of the emanating light122(shown inFIG. 1). For example, increasing the length208may increase the length126of the projected distribution124of light122while decreasing the length208may decrease the length126of the projected distribution124.

The pattern200may extend along a width212in a direction transverse to the longitudinal axis110. The width212of the pattern200may extend around less than the entire outer circumference of the outer surface120of the light pipe102. For example, the width212may be small enough such that multiple patterns200may be disposed around the outer surface120of the light pipe102. Alternatively, the width212may extend around the entire outer circumference of the light pipe102. In one embodiment, the width212is approximately the same throughout the length208of the pattern200. In another embodiment, the width212may vary across the length208of the pattern200to adjust the distribution of the light122(shown inFIG. 1) emanating from the light pipe102. Adjusting the width212of the pattern200may alter the projection angle128(shown inFIG. 1) of the projected distribution124(shown inFIG. 1) of light122. For example, increasing the width212may increase the projection angle128of the light122. Decreasing the width212may decrease the projection angle128.

The spatial density of the surface elements202may increase throughout the pattern200along the length208of the pattern200. Alternatively, the spatial density may change through only a portion, or less than all, of the pattern200. A graph214illustrates an example of a gradient216that may represent the distribution or change in the spatial density of the surface elements202in the pattern200. The horizontal axis218in the graph214represents the distance along a length208of the pattern200. The vertical axis220may represent the spatial density of the surface elements202in the pattern200. As shown inFIG. 2, the spatial density of the surface elements202may change throughout the pattern200according to the gradient216. For example, the gradient216may define the packing density of the surface elements202in the pattern200. The gradient216represents the graded change of the number of surface elements202provided in the pattern200per unit area. In the example shown inFIG. 2, more surface elements202are provided in the pattern200per square unit of surface area of the pattern200in locations approaching the second end206than the first end204. In another example, the distance between one surface element202and the neighboring surface elements202may be greater towards the first end204than the second end206. While the gradient216is illustrated as an straight line inFIG. 2, the gradient216may take the form of one or more other shapes, such as a curved line or a combination of curved and straight lines.

In one embodiment, the sizes of the surface elements202may increase throughout the pattern200along the length208of the pattern200. For example, the sizes of the surface elements202may be distributed in the pattern200according to the gradient216. Alternatively, the sizes of the surface elements202may change through only a portion, or less than all, of the pattern200. In the embodiment shown inFIG. 2, outside dimensions210of the surface elements202increase throughout the pattern200from the first end204to the second end206. The outside dimensions210may be the greatest distance extending across the surface elements202. By way of example only, the outside dimensions210may be the outer diameters of the surface elements202. In the illustrated embodiment, the outside dimensions210are measured in directions parallel to the longitudinal axis110(shown inFIG. 1) of the light pipe102(shown inFIG. 1). Optionally, only one of the spatial density and the sizes of the surface elements202may change throughout the pattern200. For example, only one of the spatial density and the sizes of the surface elements202may change in the pattern200according to the gradient216. Alternatively, each of the spatial density and the sizes of the surface elements202may change throughout the pattern200according to different gradients216.

FIG. 3is a plan view of a pattern300of surface elements302arranged in accordance with one embodiment. The pattern300of the surface elements302may be similar to the pattern116(shown inFIG. 1) of the surface elements118(shown inFIG. 1). The pattern300may be disposed on the curved outer surface120(shown inFIG. 1) of the light pipe102(shown inFIG. 1). The pattern300extends between opposing ends304,306. In one embodiment, the pattern300may be disposed on the light pipe102so that the first end304is located proximate to the attachment end112and the second end306is located proximate to the distal end114. The pattern300may extend along a length308that is less than the distance between the attachment and distal ends112,114in a direction parallel to the longitudinal axis110(shown inFIG. 1). Adjusting the length308of the pattern300may alter the length126(shown inFIG. 1) of the projected distribution124(shown inFIG. 1) of the emanating light122(shown inFIG. 1). For example, increasing the length308may increase the length126of the projected distribution124of light122while decreasing the length308may decrease the length126of the projected distribution124. The pattern300may extend along a width312in a direction transverse to the longitudinal axis110. The width312of the pattern200may extend around less than or the entire outer circumference of the outer surface120of the light pipe102. Adjusting the width312of the pattern300may alter the projection angle128of the projected distribution124of light122. For example, increasing the width312may increase the projection angle128of the light122. Decreasing the width312may decrease the projection angle128.

The pattern300is similar to the pattern200(shown inFIG. 2) in that the size and spatial density of the surface elements302may increase along the length308of the pattern300. For example, one or more of the sizes and spatial densities of the surface elements302may change throughout all or less than all of the pattern300according to a gradient that is the same as or similar to the gradient216(shown inFIG. 2). One difference between the patterns300and200(shown inFIG. 2) is the shape of the surface elements302and202(shown inFIG. 2). The surface elements302include elongated shapes having a height314and a width316. In the illustrated embodiment, the surface elements302are strips defined by the height314and width316dimensions. The height314of the surface elements302may be measured in a direction that is transverse to the longitudinal axis110(shown inFIG. 1) of the light pipe102(shown inFIG. 1). For example, the height314of the surface elements302may be measured in a direction parallel to the direction in which the width312of the pattern300is measured. The width316of the surface elements302may be measured in a direction that is parallel to the longitudinal axis110. Alternatively, the surface elements302may be provided in a shape other than a strip. For example, the surface elements302may be provided as ovals, squares, triangles, and the like.

As shown inFIG. 3, the spatial density of the surface elements302increases throughout the pattern300along the length308of the pattern200. For example, a separation distance318between adjacent surface elements302decreases along the length308of the pattern300. The spatial density of the surface elements302increases as the separation distance318decreases. Additionally, the sizes of the surface elements302increase throughout the pattern300along the length308of the pattern300. For example, the width316of the surface elements202may increase throughout the pattern300from the first end304to the second end306. Alternatively, the width316may remain substantially the same throughout all or at least some of the pattern300. In another example, the height314of the surface elements202may increase throughout the pattern300from the first end304to the second end306.

FIG. 4illustrates a plan view406of another pattern400of surface elements424and a plan view408of the distal end114of the light pipe102in accordance with another embodiment. A portion of the light pipe102is shown inFIG. 4. The light pipe102includes surface elements424that include strips402that are interconnected with one another by a line404. The line404may be a surface element424that is positioned between the other strips402so as to interconnect the strips402with one another. As shown inFIG. 4, the strips402are substantially linear strips disposed in a direction transverse to the longitudinal axis110of the light pipe102. For example, the individual strips402may be perpendicular to the longitudinal axis110. Alternatively, the strips402may be positioned at an obtuse or acute angle with respect to the longitudinal axis110. Each of the strips402has a width dimension418that is measured in a direction parallel to the longitudinal axis110of the light pipe102. The width418of the strips402may be approximately the same for all strips402in the pattern400or may vary throughout the pattern400similar to as described above in connection with the patterns116(shown inFIG. 1),200(shown inFIG. 2),300(shown inFIG. 3). The strips402are separated from one another by a separation distance420. The separation distance420may be measured in a direction that is parallel to the longitudinal axis110. The separation distance420between each pair of strips402may be the same or may vary throughout the pattern400.

The interconnecting line404extends along the light pipe102in a direction that is transverse to the individual strips402. For example, the interconnecting line404may extend substantially parallel to the longitudinal axis110. Alternatively, the interconnecting line404may be disposed at a transverse angle with respect to the longitudinal axis110. The interconnecting line404has a thickness dimension422that is measured in a direction transverse to the longitudinal axis110. For example, the thickness422of the interconnecting line404may be measured in a direction perpendicular to the longitudinal axis110. The thickness422may be approximately the same throughout the interconnecting line404or may vary throughout the pattern400.

The interconnecting line404connects the strips402such that the strips402and line404form a continuous light scattering surface on the light pipe102. The surface elements424may cause light transmitted by the light pipe102to exit the light pipe102as emanating light410in a projection412. The projection412of light410may provide for a more even distribution of light intensity on a surface414that is angled or sloped with respect to the light pipe102. As shown inFIG. 4, the surface414is disposed at an angle with respect to the light pipe102. In one embodiment, a normal direction416to the surface414is transverse to the longitudinal axis110of the light pipe102. The position of the interconnecting line404in each of the views406,408is indicated by the phantom line labeled “a” and the positions of the strips402in the views406,408are indicated by the phantom line labeled “b.” In the illustrated example, the interconnecting line404and strips402are disposed on the light pipe102such that the interconnecting line404is closer to the illuminated surface416than the strips402.

Due to the continuous nature of the interconnecting line404, or that the interconnecting line404extends along the longitudinal axis110of the light pipe102so as to cover a greater total surface area than the strips402, the interconnecting line404nay reflect more light410out of the light pipe102than the strips402. As a result, the light410that is reflected out of the light pipe102by the interconnecting line404may be more intense upon exiting the light pipe102than the light410reflected by the strips402. The more intense light that is reflected by the interconnecting line404may be directed toward the portion of the angled surface414that is farther away from the light pipe102while the less intense light that is reflected by the strips402may be directed toward the portion of the angled surface414that is closer to the light pipe102. For example, the light410that is reflected out of the light pipe102by the interconnecting line404may strike the surface414in the illuminated area labeled “A” and the light410that is reflected out of the light pipe102by the strips402may strike the surface414in the illuminated area labeled “B.” As shown inFIG. 4, the “A” area of the surface414is farther away from the light pipe102than the “B” area. By aligning the pattern400on the light pipe102and by aligning the light pipe102with respect to the surface414, the more intense light410that is reflected by the interconnecting line404may be directed towards the farther away area “A” of the surface414than the less intense light410that is reflected by the strips402and directed toward the closer area “B” of the surface414. Directing the reflected light from the pattern400in this manner may provide a more uniform distribution of the intensity of the light on the surface414.

FIG. 5is a rear exploded isometric partial view of the light pipe assembly100implemented in accordance with one embodiment.FIG. 6is a front exploded isometric partial view of the light pipe assembly100according to one embodiment.FIG. 7is a front isometric view of the housing108of the lamp assembly104according to one embodiment. As shown inFIGS. 5 and 6, the housing108of the light pipe assembly100includes a mating portion512(FIG. 5) for attaching the light pipe102to the lamp assembly104. The mating portion512includes an opening500(FIG. 6) into which the attachment end112of the light pipe102is loaded to mount the light pipe102in the lamp assembly104. An inside dimension502(FIG. 6) of the opening500may be less than an outer diameter504(FIG. 6) of the light pipe102to provide an interference fit between the light pipe102and the lamp assembly104. When the attachment end112of the light pipe102is loaded into the mating portion512of the housing108, the opening500may expand to accommodate the light pipe102. One or more slits514(FIG. 5) in the mating portion512may be provided to permit expansion of the opening500.

One or both of the light pipe102and the lamp assembly104may include orientation features to align the light pipe102with respect to the lamp assembly104. Aligning the light pipe102with the lamp assembly104may permit the light emanating from the light pipe102to be directed in a desired or predetermined direction. In one embodiment, the orientation features that align the light pipe102with respect to the lamp assembly104include a notch518(FIG. 5) in the light pipe102and a step510(FIG. 6) in the lamp assembly104. Alternatively, the notch518may be included in the housing108of the lamp assembly104and the step510may be provided in the light pipe102. The step510includes a generally flat lip600(FIG. 7) along the inside of the step510. The notch518includes a recess in the attachment end112of the light pipe102that is shaped to mate with the step510. The notch518may be formed such that the cross-sectional area of the light pipe102in a section that includes the notch518and that is measured in a plane perpendicular to the longitudinal axis110is less than the cross-sectional area of the light pipe102in a section that does not include the notch518and that is measured in a plane perpendicular to the longitudinal axis110.

The step510and notch518may have complimentary shapes such that the step510and notch518nest with one another when the light pipe102is loaded into the housing108. The engagement between the orientation features of the light pipe102and the lamp assembly104limits or inhibits rotation of the light pipe102with respect to the housing108of the lamp assembly104. Preventing rotation of the light pipe102may ensure that the pattern116of surface elements118is oriented in a desired direction. For example, the notch518and step510may be disposed in a desired location with respect to the pattern116in order to direct the light122(shown inFIG. 1) emanating from the light pipe102along a desired direction or path.

In one embodiment, the orientation features secure the light pipe102to the lamp assembly104. For example, the orientation features may include a slot516(FIG. 5) in the light pipe102and a rib506(FIG. 6) in the housing108of the lamp assembly104. The slot516and rib506may engage one another to prevent removal of the light pipe102from the housing108in a direction parallel to the longitudinal axis110of the light pipe102. The slot516extends along the outer circumference of the light pipe102near the attachment end112. As shown inFIG. 5, the notch518and slot516in the light pipe102may be circumferentially offset from one another along the outer surface120of the light pipe102. The slot516may include a front wall800and a rear wall802spaced apart from one another in a direction parallel to the longitudinal axis110. The rib506may include a ramp surface602(FIG. 7) joined to a latch surface604(FIG. 7). The ramp surface602may be positioned transverse to the latch surface604and extend between an inner surface508(FIG. 6) of the housing108and the latch surface604. The latch surface604may extend between the inner surface508and the ramp surface602. Alternatively, the ramp and latch surfaces602,604may be positioned parallel to one another with a third surface (not shown) interconnecting the ramp and latch surfaces602,604. For example, the ramp and latch surfaces602,604may be parallel to one another and each extend between the inner surface508and the third surface.

FIG. 8is an isometric cross-sectional view of the light pipe102attached to the lamp assembly104taken along line7-7inFIG. 1according to one embodiment. As shown inFIG. 8, the rib506is received in the slot516between the front and rear walls800,802to secure the light pipe102to the housing108of the lamp assembly104. The ramp surface602slides along the front wall800of the slot516as the light pipe102is loaded into the housing108. The latch surface604engages the front wall800to prevent removal of the light pipe102from the lamp assembly104. A depth700of the slot516represents the radial distance that the slot516extends into the light pipe102from the outer surface120of the light pipe102. A height702of the rib506represents the distance that the rib506protrudes from the inner surface508of the housing108. The depth700of the slot516and the height702of the rib506may be approximately matched with one another such that the rib506is entirely received with in the slot516. For example, the height702of the rib506may be approximately the same as the depth700of the slot516. A variety of materials may be used for the light pipe assembly100(shown inFIG. 1). For example, materials that are elastic enough to allow insertion of the light pipe102into the housing108and provide a sufficient retention force once the light pipe102is inserted therein, and/or to expand and retract a sufficient amount to allow the light pipe102to be secured to the housing108.