Abstract:
An LED light tube and method of manufacturing an LED light tube includes the steps of forming an LED light tube housing of a first housing segment joined to a first end cap. One end of a circuit board is inserted through the one housing segment into contact with the first end cap. One or more additional housing segments are slid over the circuit board into engagement with ends of previously mounted housing segments. A second end cap is joined to the engaged ends of the multiple housing segments are fixed together to complete a unitary housing.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/362,561, filed Jul. 8, 2010, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    The present LED light tube and manufacturing method relates to a light emitting diode (LED) based light tube usable in a fluorescent light fixture and methods of manufacturing the LED light tube. 
         [0003]    LED-based light tubes have been developed for use in fluorescent light fixtures in place of conventional fluorescent tubes. LEDs have many advantages over fluorescent tubes. LEDs are more efficient, last longer, and are less sensitive to vibrations and low temperatures. To take advantage of the benefits of LEDs, LEDs are being included in lights of various shapes, such as in the shape of fluorescent tubes. LED-based light tubes, by definition, include one or more LED positioned on a circuit board. The light tubes for use in the fluorescent light fixtures are sized in length to fit the existing fixtures, and accordingly, have a considerable length. The circuit board and LEDs, along with other components, are inserted through the length of the tube during manufacture. 
       SUMMARY 
       [0004]    Disclosed herein are LED based light tubes usable in a fluorescent light fixture and methods of manufacturing the LED light tubes. One embodiment of a LED-based light for replacing a conventional fluorescent light bulb in a fluorescent light fixture includes a housing having multiple segments of equal diameter, a circuit board, and at least one LED mounted on the circuit board. The circuit board and LED&#39;s are located in an interior a cavity formed by the multiple segments of the housing being placed end to end. 
         [0005]    One embodiment of a method of manufacturing a LED-based light mountable on a fluorescent light fixture includes the steps of providing a housing segment having a first end cap on one end and an open end; inserting a circuit board through the open end until it contacts the end cap; sliding at least one additional housing segment individually over the circuit board until an entire length of the circuit board is enclosed; placing a second end cap on a remaining open end of the last housing segment; and joining seams created between the housing segments. 
         [0006]    In another embodiment, a method of manufacturing an LED-based light mountable in a fluorescent light fixture include the steps of coupling a first open end of one housing segment to the first end cap; engaging at least one additional housing segment to an opposite end of the one housing segment until a desired overall housing length is achieved, inserting a circuit board within an interior cavity formed by the housing segments into engagement with the first end cap; coupling a second end cap to the end of the last housing segment and to the circuit board; and fixedly joining ends of the housing segments to form a unitary housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein: 
           [0008]      FIG. 1  is a perspective view of an embodiment of an assembled LED light tube; 
           [0009]      FIG. 2  is a perspective expanded view of the LED light tube of  FIG. 1  prior to assembly; 
           [0010]      FIG. 3  is a perspective view of another embodiment of an assembled LED light tube; 
           [0011]      FIG. 4  is a perspective expanded view of the LED light tube of  FIG. 3  prior to assembly; 
           [0012]      FIG. 5  is an exploded view of an end of the light tubes of  FIGS. 1 and 3 ; and 
           [0013]      FIG. 6  is a cross sectional view of an alternative embodiment of a LED light tube. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    LED-based replacement lights for replacing conventional fluorescent light bulbs in a fluorescent fixture are typically made with a single tubular housing within which components of the light, such as a circuit board and LEDS, are inserted. The single housings typically have a length of approximately 48″, with diameters of 0.625″, 1.0″, or 1.5″ for engagement with common fluorescent fixtures. Currently, the components of the light are inserted into an end of the single housing and must be fed through the entire housing until the components span the length of the housing. 
         [0015]    The embodiments of the housings disclosed herein are in multiple segments, thereby easing manufacture of the lights and providing more design options. Non-limiting examples of lights with the housings disclosed herein are illustrated in  FIGS. 1-4 . In the example illustrated in  FIGS. 1 and 2 , an LED-based light tube  10  is configured as a replacement for a fluorescent tube in a fluorescent fixture. The light tube  10  includes a housing  12 , a circuit board  14  in the housing  12 , a plurality of LEDs  18  mounted on the circuit board  14 , and a pair of end caps  20  attached at opposing ends of the housing  12 . The light tube  10  can additionally include other components, such as electrical components or one or more highly thermally conductive structures for enhancing heat dissipation. The lights described herein are presented as examples and are not meant to be limiting. The embodiments of the housings disclosed herein can be used with any internal light components known to those skilled in the art compatible with the scope of the disclosure. 
         [0016]    The circuit board  14  is not limited to the example shown in the figures. The circuit board  14  can have a LED-mounting side and a primary heat transferring side opposite the LED-mounting side. The circuit board  14  may have an LED-mounting side with apertures along the circuit board to allow light to pass through. The circuit board  14  may be made in one piece or in longitudinal sections joined by electrical bridge connectors. The circuit board  14  and the housing  12  can be in thermally conductive relationship with the circuit board  14  by attachment to the housing  12  using highly thermally conductive adhesive transfer tape. The circuit board  14  can alternatively be positioned in a thermally conductive relationship with the housing  12  by attaching the circuit board  14  to the housing  12  using screws, glue, a friction fit, and other attachments known to those of skill, in which cases thermal grease can be applied between the circuit board  14  and the housing  12 . The circuit board  14  is preferably one on which metalized conductor patterns can be formed in a process called “printing” to provide electrical connections from connectors  22  on the end caps  20  to the LEDs  18  and between the LEDs  18  themselves. An insulative board is typical, but other circuit board types, e.g., metal core circuit boards, can alternatively be used. 
         [0017]    The LEDs  18  can be surface-mount devices of a type available from Nichia, although other types of LEDs can alternatively be used. For example, although surface-mounted LEDs  18  are shown, one or more organic LEDs can be used in place of or in addition thereto. Each LED  18  can include a single diode or multiple diodes, such as a package of diodes producing light that appears to an ordinary observer as coming from a single source. The LEDs  18  can be mounted to the circuit board  14  at longitudinally spaced apart locations along a central portion of the circuit board  14  as shown in  FIGS. 1 and 2 . In other examples, however, the LEDs  18  can be mounted at other locations. For example, LEDs  18  can be mounted in two longitudinally extending rows on opposing longitudinal sides of the circuit board  14 . 
         [0018]    The LEDs  18  can emit white light. However, LEDs that emit blue light, ultra-violet light or other wavelengths of light can be used in place of or in combination with white light emitting LEDs  18 . The number of LEDs  18  can be a function of the desired lumen output of the light tube  10  and the power of the LEDs  18 . For a 48″ light, the number of LEDs  18  can vary from about five to four hundred such that the light tube  10  outputs approximately 500 to 3,000 lumens. However, a different number of LEDs  18  can alternatively be used, and the light tube  10  can output any other amount of lumens. The LEDs  18  can be evenly spaced along the circuit board  16 , and the spacing of the LEDs  18  can be determined based on, for example, the light distribution of each LED  18  and the number of LEDs  18 . 
         [0019]    The end caps  20  can be attached at opposing longitudinal ends of the housing  12  for physically and electrically connecting the light tube  10  to a fixture. The end caps  20  can be the sole physical connection between the bulb  10  and the fixture. The end caps  20  can be electrically connected to the circuit board  14  for providing power to the LEDs  18 . Each end cap  20  can include two pins  22 , although two of the total four pins can be “dummy pins” that do not provide an electrical connection. Alternatively, other types of electrical connectors can be used, such as an end cap carrying a single pin. Also, while the end caps  20  are shown as including cup-shaped bodies, the end caps  20  can have a different configuration (e.g., the end caps  20  can be shaped to be press fit into the ends of the housing  12 ). One or both of the end caps  20  can additionally include electric components, such as a rectifier and a filter. 
         [0020]    The housing  12  can be formed by connecting multiple individual parts, not all of which need be light transmitting. As shown in  FIGS. 1-4 , the housing  12  can be provided in two segments  12   a  and  12   b , or in three segments  12   a ,  12   b  and  12   c  or more. These are provided as examples and are not meant to be limiting. Any number and sizes of segments can be formed as desired or required. 
         [0021]    For example, all of the housing segments may have the same length or one or more of the housing segments can have a different, non-equal length from the other housing segments. One or all of the housing segments may have a constant diameter linear shape between the opposed first and second ends. One or more of the housing segments of all of the housing segments used to form a single unitary housing, can have a non-linear shape, such as an arcuate or U-shape. This will enable the housing to have an overall U-shape formed of one or more arcuate or U-shaped segments joined to one or more linear segments at opposite ends of the one or more arcuate or U-shaped segments. 
         [0022]    All of the housing segments may have a non-linear shape, such as an arcuate shape sized to form a circular housing. 
         [0023]    The housing segments  12   a ,  12   b ,  12   c  can be made from polycarbonate, acrylic, glass or another light transmitting material (i.e., the housing segments can be transparent or translucent). For example, a translucent housing segment can be made from a composite, such as polycarbonate with particles of a light refracting material interspersed in the polycarbonate. While the illustrated housing segments  12   a ,  12   b ,  12   c  are cylindrical, the housing segments can alternatively have a square, triangular, polygonal, or other cross sectional shape. Similarly, while the illustrated housing segments  12   a ,  12   b ,  12   c  are linear, the overall housing  12  can have an alternative shape, e.g., a U-shape or a circular shape, making the housing segments  12   a ,  12   b ,  12   c  non-linear. The housing segments  12   a ,  12   b ,  12   c  can be manufactured to include light diffusing or refracting properties, such as by surface roughening or by applying a diffusing film to the housing  12 . 
         [0024]    The light diffusing and/or refracting properties of the housing segments  12   a ,  12   b ,  12   c  can vary between segments or about the circumference of the individual segments  12   a ,  12   b ,  12   c . For example, housing segment  12   a  can be configured to provide greater light diffusion or refraction than the other housing segments  12   b  and  12   c . This can be accomplished by, for example, increasing an amount of surface roughening on housing segment  12   a  compared to the other housing segments  12   b ,  12   c , by applying different diffusing film to housing segment  12   a  than the other housing segments  12   b ,  12   c , or by attaching one or more reflectors to the housing segment  12   a  over at least portions of its surface area. 
         [0025]    Assembling the light tubes  10  involves, in the case of  FIG. 2 , attaching an end cap  20  to one end of a housing segment  12   a , inserting one end of the circuit board  14  into the housing segment  12   a  until the circuit board  14  contacts the end cap  20 . The end cap  20  can have a raised portion  28  forming a slot within which the end of the circuit board  14  fits to hold the circuit board  14  in place. This is shown more clearly in  FIG. 5 . Housing segment  12   b  is slid over the other end of the circuit board  14  until it contacts housing segment  12   a . The other end cap  20  is then placed on the open end of housing segment  12   b . The seam  30  of housing segments  12   a  and  12   b  is joined by, for example, ultrasonic welding. When the light tube  10  of  FIG. 3  is manufactured, seams  30   a  and  30   b  are similarly joined after the components are assembled. Other means of joining the seam or seams of the housing known to those skilled in the art can be used as desired or required. After assembly, the light tubes  10  of  FIGS. 1 and 3  can be installed in a fixture by engaging the end caps  20  with the fixture, with the circuit board  14  oriented to face the area to be illuminated. 
         [0026]    Additionally, while the illustrated circuit board  14  is shown in  FIG. 5  to be received by the slot  28  in the end cap  20 , the circuit board  14  can be slidably engaged with the housing  12 , as shown is  FIG. 6 , and secured by tabs  32 . The housing segments  12   a ,  12   b ,  12   c  can have tabs  32  that project from the segment on opposite sides of the circuit board  14 . The tabs  32  are preferably formed integrally with the segment by, for example, extruding the housing segments  12   a ,  12   b ,  12   c  to include the tabs  32 . Each tab  32  can extend the entire length of a housing segment, though a series of discrete tabs can alternatively be used to secure the circuit board  14 . The circuit board  14  can alternatively be clipped, adhered, snap- or friction-fit, screwed or otherwise connected to the housing segments. 
         [0027]    Although the circuit board  14  is shown in  FIGS. 1-4  as an integral, one-piece circuit board, multiple circuit board sections can be joined by bridge connectors to create the circuit board of the appropriate length. If multiple circuit board sections are used, the assembly of the light tube may involve inserting a first circuit board section into a housing segment, joining another circuit board segment to the first segment with a bridge connector, sliding another housing segment over the last inserted circuit board segment and continuing until the assembly is complete with the end caps at each end of the overall light tube. 
         [0028]    The above-described examples have been described in order to allow easy understanding of the invention and do not limit the invention. On the contrary, the invention is intended to cover various modifications and equivalent arrangements, whose scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structure as is permitted under the law.