Patent Publication Number: US-11644194-B2

Title: Linear optical system with ingress protection

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to, and the benefit of, U.S. Provisional Patent Application No. 63/187,659, filed May 12, 2021, the contents of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This invention relates to optical systems for linear lighting. 
     BACKGROUND 
     Linear lighting is a particular type of solid-state lighting. In this type of lighting, a long, narrow printed circuit board (PCB) is populated with light-emitting diode (LED) light engines, usually spaced at a regular pitch or spacing. Each LED light engine contains one or more LEDs along with the wires, structures, and connections necessary to mount the LEDs on the PCB. The PCB may be either rigid or flexible, and other circuit components may be included on the PCB, if necessary. Depending on the type of LED light engine or engines that are used, the linear lighting may emit a single color, or may be capable of emitting multiple colors. 
     In combination with an appropriate power supply or driver, linear lighting is considered to be a luminaire in its own right, and it is also used as a raw material for the production of more complex luminaires, such as light-guide panels. 
     One of the most popular ways of using linear lighting is to install it in a channel and cover it with a cover. The cover typically acts as a diffuser, spreading the light and improving the overall appearance of the emitted light. Examples of channels used with linear lighting can be found in U.S. Pat. No. 9,279,544, the contents of which are incorporated by reference in their entirety. The typical channel for linear lighting is a single-piece extrusion, made of metal or plastic, that has a pair of sidewalls and a bottom. 
     In a variation on the usual channel-and-cover arrangement, U.S. Pat. No. 10,788,170 to Bryan, the contents of which are incorporated by reference herein in their entirety, discloses two-element optical systems for linear lighting. These systems are designed to provide a highly focused or evenly diffused light beam and can be used in a channel even when the channel is only designed for a single cover or element. 
     In the systems of U.S. Pat. No. 10,788,170, the outer lens of the two-element system also serves as a cover. The cover is a physical barrier to limit ingress of dust into the channel. However, the protection provided by a typical linear lighting channel cover is limited. While greater protection against the ingress of water and other types of foreign material is often desirable, designing channels, covers, and other elements that can provide that protection can be particularly difficult, especially when the luminaire has multiple parts. 
     BRIEF SUMMARY 
     One aspect of the invention relates to closed optical assembly. The optical assembly includes a hollow outer optical element, an inner optical element, and a strip of linear lighting. The inner optical element and the strip of linear lighting are installed in a cavity of the outer optical element. Ends of the hollow outer optical element are closed, such as by endcaps, to seal the cavity of the outer optical element, thus protecting the optical assembly from ingress of dust, water, or other foreign material. 
     In another aspect of the invention, the strip of linear lighting rests on an interior bottom of the cavity. The inner optical element rests on support structure in the cavity of the hollow outer optical element such that the inner optical element receives light emitted from the strip of linear lighting. The outer optical element supports the inner optical element such that the outer optical element is optically aligned with the inner optical element so as to receive light passed through the inner optical element. 
     A further aspect of the invention relates to a linear luminaire. The luminaire includes a channel and a closed optical assembly having a hollow outer optical element, an inner optical element, and a strip of linear lighting. Ends of the outer optical element are closed, such as by end caps, with the inner optical element and the strip of linear lighting encased in a cavity of the outer optical element. The outer optical element includes channel engaging structure that secures the outer optical element to the channel. 
     In another aspect, the channel includes mounting structure for the luminaire. The mounting structure may include hanging structure to suspend the luminaire from a surface as a hanging fixture. 
     Yet another aspect of the invention relates to a method for sealing the ends of an optical assembly, such as the optical assembly described above. In this method, an end of the optical assembly is dipped into a container that contains an uncured resin. The resin covers the end of the optical assembly and then is caused or allowed to cure. 
     Other aspects, features, and advantages of the invention will be set forth in the description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The invention will be described with respect to the following drawing figures, in which like numerals represent like features throughout the description, and in which: 
         FIG.  1    is a perspective view of a linear luminaire according to one embodiment of the invention; 
         FIG.  2    is an exploded view of the linear luminaire of  FIG.  1   ; 
         FIG.  3    is a cross-section taken through Line  3 - 3  of  FIG.  1   ; 
         FIGS.  4 - 5    are front and back perspective views, respectively, of the solid endcap of  FIG.  1   ; 
         FIGS.  6 - 7    are front and back perspective views, respectively, of the endcap with a power cord opening of  FIG.  1   ; 
         FIG.  8    is a cross-sectional view of the light-generating assembly of the linear luminaire of  FIG.  1   , illustrating its placement into a mold for end-sealing with a liquid resin; 
         FIG.  9    is a cross-sectional view similar to the view of  FIG.  8   , illustrating the curing of a resin to seal the ends of the light-generating assembly; 
         FIG.  10    is a front perspective view of the assembly of  FIG.  9   , sealed and installed in a channel; and 
         FIG.  11    is a rear perspective view of the assembly of  FIG.  9   , sealed and installed in a channel. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a perspective view of a linear luminaire, generally indicated at  10 , according to one embodiment of the invention. The linear luminaire  10  includes a light-generating assembly  12  and a channel  14 . 
     The light-generating assembly  12  is a self-contained, sealed optical assembly that includes all elements necessary to generate light and to direct, focus, or modify the generated light in a particular way. As will be described below in more detail, the light-generating assembly  12  would typically include at least one light source and at least one optical element. Here, the term “optical element” refers to an element that receives light from the strip of linear lighting and modifies that light in some way, e.g., to focus, direct, or diffuse the light. An optical element may be a lens, but the term broadly encompasses both lens and non-lens elements. A diffuser, a non-lens that diffuses or scatters the light, is one example of a non-lens element. Other examples of non-lens optical elements may include gels or filters that change the color of the light. 
     The light-generating assembly  12  is similar in capabilities to the two-element optical systems disclosed in U.S. Pat. No. 10,788,170 (“the &#39;170 patent”). However, as will be explained below in more detail, in contrast to the systems of the &#39;170 patent, the light-generating assembly  12  is intended to have a higher ingress protection rating. The light-generating assembly  12  may have an ingress protection rating of at least IP64, and it may have an ingress protection rating as high as IP67 or IP68. In other words, the light-generating assembly  12  will typically prevent ingress of dust, and will usually at least protect against splashes of water, although it may protect against water jets, and in some cases, may allow full immersion, or even continuous operation underwater. 
     To that end, in the embodiment of  FIG.  1   , the light-generating assembly is sealed by an endcap  16 ,  18  on each end. The endcap  16  on one end is solid; the other endcap has an opening (not shown in  FIG.  1   ) that allows for the egress of a power cord  20  to power the lighting element inside. A molded strain relief  22  is fitted around the power cord  20  proximate to the endcap  18 . 
     The channel  14  of  FIG.  1    is the channel disclosed in U.S. Pat. No. 11,168,852, the contents of which are incorporated by reference herein in their entirety. This particular channel  14  has an upper compartment  24  in which the light-generating assembly  12  is seated, a lower compartment  26  that is adapted to accept mounting structures and also serves as a raceway for wires and cables, and a cross-member  28  that separates the upper compartment  24  from the lower compartment  26 , giving the channel  14  an H-shaped cross-section. As will be described below in more detail, the light-generating assembly  12  and the channel  14  have complementary engaging features such that the light-generating assembly  12  snaps into place in the upper compartment  24  of the channel  14  without the use of tools, and without the need for dedicated fasteners or adhesives. 
     The channel  14  itself may, e.g., be made of a metal, such as aluminum, and may be extruded or machined. The basic form of the channel may be painted, powder-coated, anodized, or otherwise surface-treated as desired. Yet as those of skill in the art may realize, the particular features of the channel  14  are not critical to the invention. Rather, the light-generating assembly  12  may be adapted for placement in any type of channel. Moreover, while it is convenient if the channel  14  and the light-generating assembly  12  have complementary interengaging features and can “snap” together without the need for fasteners or adhesives, that may not always be the case. So long as the light-generating assembly  12  fits at least partially within a channel, adhesives or fasteners can be used to secure it. 
       FIG.  2    is an exploded perspective view of the linear luminaire  10 , and  FIG.  3    is a cross-sectional view taken through Line  3 - 3  of  FIG.  1   . As shown in  FIG.  2   , the light-generating assembly  12  of this embodiment includes five major components: a body  30 , which includes a first, outer optical element  32 ; a second, inner optical element  34 ; a light source  36 , and the two endcaps  16 ,  18 . 
     The body  30  of the light-generating assembly  12  has the general form of a hollow tube with an internal cavity. The outer optical element  32  lies at the top of the body  30  and, in this embodiment, is a biconvex lens of the type described in the &#39;170 patent. In other embodiments, the outer optical element  32  could be a biconvex lens with a different curvature or curvatures, a different type of lens (e.g., convex, concave, biconcave, etc.), or a non-lens optical element, like a diffuser. In addition to a traditional lens, the outer optical element  32  may comprise a plurality of different facets, as in a Fresnel lens. The outer optical element  32  may also have features of the asymmetrical optical system of U.S. patent application Ser. No. 17/230,081, filed Apr. 14, 2021, the contents of which are incorporated by reference in their entirety. 
     From the outer optical element  32  down, the profile of the body  30  bifurcates, as can be seen at the end in  FIG.  2    and in the cross-sectional view of  FIG.  3   . That bifurcation defines a set of mirror-image left and right connecting legs  38  that have the complementary features necessary to engage the upper compartment  24  of the channel  14 , as well as mirror-image left and right sidewalls  40  that extend contiguously down and around into a bottom  42 , completing the tubular shape of the body  30  and defining a cavity in the body  30 . 
     The depending connecting legs  38  are spaced laterally outward from the sidewalls  40 , giving the connecting legs  38  enough room to deflect inwardly in order to make a snug connection with the upper compartment  24  of the channel  14 . The sidewalls  40  themselves are canted inward as they extend from top to bottom, leaving sufficient room for the connecting legs  38  to flex. The sidewalls  40  are at their narrowest at positions corresponding to the bottoms of the connecting legs  38 . The profile of the body  30  then flares back out rectilinearly into the bottom  42 , extending outward, down, and around. 
     As can be seen in both the exploded view of  FIG.  2    and the cross-sectional view of  FIG.  3   , with the body  30  shaped and configured as it is, the light source  36  rests not on the cross-member  28  of the channel  14 , as would be customary with a conventional linear luminaire, but along the interior bottom  42  of the body  30 . This is part of what allows the light-generating assembly  12  to be a self-contained, sealed unit. 
     In this embodiment, the light source  36  is a strip of linear lighting, an elongate, narrow printed circuit board (PCB)  43  on which a number of LED light engines  44  are mounted, spaced apart at a regular spacing or pitch. Typically, a PCB  43  for linear lighting is of two-layer construction, with components surface-mounted on an upper layer and a lower layer that includes conductors. The LED light engines  44  may be of any type and produce any color or colors of light. In addition to the LED light engines  44 , other components may be mounted on the PCB  43 . These elements, such as resistors, may be used to control the current in the circuit or circuits and to control the LED light engines  44  themselves. The power cable  20  of the illustrated embodiment has two wires, usually a positive wire  48  and a negative-return wire  50 , that are soldered to defined solder pads  52 ,  54  on the PCB  43 . The PCB  43  itself may be either rigid or flexible, made, e.g., of a flexible material like polyimide film, polyethylene terephthalate (PET) film, or aramid film, or of a rigid material, like aluminum, FR4, or ceramic. With flexible material in particular, the PCB  44  may be made to arbitrary lengths, as lengths of flexible PCB material can be joined together at overlapping solder joints to form a PCB  43  of essentially any desired length. 
     The nature of the light source  36  is not critical. In addition to conventional linear lighting, organic LEDs (OLEDs), LED filaments, and other types of solid-state lighting may be used. As shown in  FIG.  2   , the light source  36  generally slides into the cavity within the body  30 . This may be relatively easy to do if the light source  36  has a rigid PCB  43 . However, the light source  36  may not always be a rigid strip. For example, the light source may also comprise a plurality of individual light-emitting elements that are connected together, e.g., a plurality of LED modules that are connected together by wires or cables. Moreover, although it is usually desirable for the light source  36  to extend substantially the entire length of the body  30  (e.g., less a small distance on each end used to seal the body  30 ), that is not an absolute requirement, and the precise arrangement of the light source  36  will usually depend on the application. 
     If the light source  36  is not in the form of a rigid strip (e.g., having a rigid PCB  43 ), it may be difficult to slide it into the body  30 , at least in some circumstances, for example, if the body  30  is particularly long. There are many potential ways of dealing with this issue. For example, it may be helpful to join the PCB  43  to a carrier. A carrier, as the term is used here, means anything that can increase the stiffness of the PCB  44  enough to allow it to be inserted into the body  30  without difficulty, preferably without entirely compromising the flexibility of the PCB  43 . Suitable carriers may include metal strips, like steel or aluminum strips, or plastic strips, typically thin and the same width or just wider than the PCB  43 . If a carrier is used, the PCB  43  may be joined to the carrier with, e.g., pressure-sensitive adhesive on its underside. The carrier may or may not be adhered in place within the body  30 . Typically, carrier-strips of this type are bendable in the same plane as the PCB  43 . Other techniques may be used to get the light source  36  into the body. For example, a string may be tied or otherwise temporarily adhered to the PCB  43 . In some cases, if the joint between the wires  48 ,  50  and the PCB  43  is strong enough, the power cable  20  may be used to pull the PCB  43  into the body  30 . 
     The second, inner optical element  34  is an optional component. In some applications, the first, outer optical element  32  of the body  30  may be sufficient to perform the desired light manipulation. In that case, the second, inner optical element  34  may simply be omitted. 
     In this embodiment, the second, inner optical element  34  includes an optically-active portion  56 , a leg  58  to each side of the optically-active portion  56 , and an outwardly-extending support or lip  60  at the top of each leg  58 . The arrangement is best seen in the cross-sectional view of  FIG.  3   : the lips  60  of the second, inner optical element  34  rest on ledges  62  defined in slot-spaces  64  that lie just under the first, outer optical element  32 . From the lips  60 , the legs  58  depend downwardly and slightly inwardly, such that when the light source  36  is installed, the optically-active portion  56  is centered directly over it. This overall arrangement allows the body  30  to include two optical elements  32 ,  56  when only one would typically be included, with the second, inner optical element  32  suspended from the body  30 . 
     As may be apparent from  FIG.  3   , in the body  30  and second, inner optical element  34 , portions that are not optically active (i.e., portions that are not designed to receive and transmit light) are opaque in this embodiment. Additionally, the channel  14 , the body  30  and the second, inner optical element  34  have the same cross-sectional shape over their entire lengths. Because of this, the body  30  and the second, inner optical element  34  may be extruded, with co-extrusion used to extrude both the optically active and optically inactive parts at once. For example, co-extruded materials for body  30  could include material for the outer optical element  32  that is transparent with the balance of the material for the outer optical element being opaque. Exemplary transparent materials include acrylic, polycarbonate, or polyvinylchloride, although any material that is transparent to the light emitted by the linear lighting and has a higher index of refraction than air may be used. Non-optically active portions may be made of the same material with an added opaque colorant, or they may be made of a different material. A more detailed description of co-extruding an optical element can be found in the &#39;170 patent. 
     While extrusion is one convenient way of making elements of constant cross-section, other methods of manufacture may also be used. For example, particularly in shorter sections, both the body  30  and the second, inner optical element  34  may be molded or co-molded, machined from a larger block of material, or made using additive manufacturing. It should also be understood that co-extrusion and co-molding are not the only possible techniques that could be used to create a piece with non-uniform properties. For example, an outer optical element could be extruded or molded of a single material and subjected to additional manufacturing operations to render non-optically active portions opaque, e.g., by coating. Additionally, dissimilar materials could be joined by processes like heat fusing, ultrasonic welding, or adhesives after initial manufacture. 
       FIGS.  4 - 7    are outer and inner perspective views of the endcaps  16 ,  18 , respectively. Specifically, the closed endcap  16  is shown in  FIGS.  4 - 5    and the open endcap  18  is shown in  FIGS.  6 - 7   . Each endcap  16 ,  18  has the same set of engaging features that allow it to engage and seal an end of the body  30 . Specifically, a set of four pins  72  project outwardly from each endcap  16 ,  18 , such that they will extend into the body  30  when the endcaps  16 ,  18  are engaged with the body  30 . The pins  72  are positioned such that they extend into the interstices of the body  30  (e.g., between the sidewalls  40  and the connecting legs  38 . A wedge  74  projects from each endcap  16 ,  18  in the same direction as the pins  72 . The wedge  74  may sit on the ledges  62  that support the second, inner optical element  34 . In order to accommodate the endcaps  16 ,  18 , the second, inner optical element  34  may have a length that is very slightly shorter than that of the body  30 . Although the strain relief  22  is shown as a component of the endcap  18 , it may be separate or attached to the power cord  20  in other embodiments. 
     The endcaps  16 ,  18  may be made of a compliant material, like a rubber, or of a hard plastic. If the endcaps  16 ,  18  are made of a hard plastic, they may have a co-molded or adhered layer of softer, compliant material in order to make a seal, or they may use an appropriately-shaped gasket between the inner face of the endcap  16 ,  18  and the outer face of the body  30 , in order to make a better seal. 
     Manufactured endcaps  16 ,  18  are not the only way to seal the body  30  of the linear luminaire  10 .  FIG.  8    is a cross-section of the body  30 . In the view of  FIG.  8   , the body  30  is dipped end-first into a container  102  that contains a resin  104 . The fit between the container  102  and the linear luminaire  100  is tight enough that the resin  104  will flow into and seal the end of the body  30  without flowing around it. The container  102  may have a shape that is a negative or mirror image of the outer perimeter of the body  30 . A seal may be provided along the inner perimeter of the container or added to the exterior of the body  30  (e.g., by rolling a large O-ring or a custom-designed elastomeric piece onto the body  30 ). The end of the body  30  is dipped into the resin  104  to a shallow depth. 
     The resin would typically be a synthetic polymeric resin, e.g., a polyurethane resin, a silicone resin, a polyvinyl chloride (PVC) resin, or a resin of some other type of chemistry. The resin may be a one-component system that cures upon exposure, e.g., to air or to moisture in the air, or it may be a two-component system that cures after two components are mixed, e.g., a platinum- or tin-cured silicone resin system. Once the end of the body  30  is dipped, it may be clamped or held in place while curing occurs. 
     The resin  104  may be caused or allowed to cure. That is, a mixed two-component resin system may cure by itself at room temperature (or at other ambient conditions), and any curing steps may simply involve allowing that to happen. Alternatively, a resin system may be caused to cure by, e.g., baking at elevated temperature (35° C., 65° C., etc.). In some cases, a resin system may also be cured by application of a form of radiation other than heat (e.g., UV light, or light of particular wavelengths).  FIG.  9    is a cross-sectional view similar to the view of  FIG.  8   , illustrating the body with a solidified resin endcap  104 . 
       FIGS.  10  and  11    are left and right perspective views illustrating the linear luminaire  100  with its cured resin endcaps  104 ,  106 . To make the endcap  106  with an opening for the power cord  20 , an appropriate form or insert would be placed in position in the container  102 . 
     The endcaps  104 ,  106  may or may not be removable, depending on the nature of the resin, the material of the channel  14 , and other factors. For example, if the resin is a silicone and the channel  14  is made of metal, the endcaps  104 ,  106  may be removable, because the silicone would not typically adhere to the channel  14 . 
     While the invention has been described with respect to certain embodiments, the description is intended to be exemplary, rather than limiting. Modifications and changes may be made within the scope of the invention, which is defined by the appended claims.