Patent Publication Number: US-8985811-B2

Title: LED luminaire

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a LED luminaire, and more particularly, to a LED luminaire with wide view angle. 
     2. Description of Related Art 
     LEDs are widely used in lighting application, such as in various luminaire. For example, the luminaire may be a tube, a bulb or a down light, etc. 
     The view angle of the traditional LED is about 120 degrees. Due to the small view angle, just as the tube for example, the tube using the traditional LED module has smaller view angle than the fluorescent tube in the transverse direction perpendicular to the tube shaft. Furthermore, multiple LEDs are arranged along the tube shaft and a dark area occurs between the adjacent LEDs because of the small view angle. Therefore, the regions of high light density and low light density are occurred alternatively in the longitudinal direction of the tube shaft (i.e., hot spot). The viewers may feel uncomfortable in vision due to the hot spot phenomenon. 
     Currently, some manufacturers have used smaller LEDs on the printed circuit board. By decreasing the distance between adjacent LEDs, the low light density area is reduced for solving the hot spot problem in the longitudinal direction of the tube shaft. However, the problem of the small view angle in the transverse direction cannot be solved by using smaller LEDs. 
     To overcome the above issues, the inventor proposes a solution as described below. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is to provide a LED luminaire, which is characterized by a two-layer structure that can be formed by a co-extrusion method. The two-layer structure includes a body portion and an optical structure. The optical structure substantially is a sheet-like structure with two surfaces not parallel to each other. Two refractions occur as the light passes through the optical structure, such that the light can project in larger angles and increase the view angle accordingly. 
     The present invention offers the following advantages. The body portion and the optical structure could be made by the same or different plastic material. Next, a co-extrusion process could be used to produce the body portion and the optical structure integrally. No additional assembly is needed, which increases the efficiency of manufacturing process. Furthermore, the light is refracted twice by passing through the two non-parallel surfaces (i.e., the first and second surface) of the optical structure to increase the projection angle of the lighting module, such that the view angle of the lighting module is increased. 
     In order to further appreciate the characteristics and technical contents of the present invention, references are hereunder made to the detailed descriptions and appended drawings in connection with the present invention. However, the appended drawings are merely shown for exemplary purposes, rather than being used to restrict the scope of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view of the LED luminaire of a first embodiment according to the present invention; 
         FIG. 2A  shows a cross-sectional view of the LED luminaire of a second embodiment according to the present invention; 
         FIG. 2B  shows a part of the optical structure of  FIG. 2A ; 
         FIG. 2C  shows the curvature of the middle portion of the optical structure according to the second embodiment of the present invention; 
         FIG. 3  shows the light shape of the second embodiment according to the present invention; 
         FIG. 4  shows an alternative of the second embodiment according to the present invention; 
         FIG. 5  shows another alternative of the second embodiment according to the present invention; 
         FIG. 6  shows an alternative of the embodiment of  FIG. 5 ; 
         FIG. 7  shows a cross-sectional view of the LED luminaire of a third embodiment according to the present invention; and 
         FIG. 8  shows a cross-sectional view of the LED luminaire of a fourth embodiment according to the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter the present invention is described in the following embodiments shown in the drawings and the same reference number is designated to represent the similar element. 
     The present invention provides a LED luminaire that has a body portion and an optical structure, and the body portion and the optical structure are manufactured integrally by a co-extrusion process. The optical structure is used to generate two refractions when the light passes through the optical structure, so as to increase the view angle of the lighting module assembled in the LED luminaire of the present invention. The embodiments of the LED luminaire in the present invention are described with the LED tubes, but not limited thereby. The luminaire of the present invention may be a LED bulb, down light or any other types of the lighting device. As the LED bulb for example, the optical structure is a sheet-like structure formed within the body portion of the LED bulb along the lamp cover. As the LED tube for example, the body portion is a tubular element with an opening at both ends, and the optical structure is a sheet-like structure formed within the body portion of the LED tube. 
     The following drawings are cross-sectional views along the transverse axis perpendicular to the body portion. 
     Please refer to  FIG. 1 ; the LED luminaire  1  of the first embodiment is shown, and the LED luminaire  1  at least has a body portion  10  and an optical structure  11 . A lighting module  12 , for example a LED chip, is located in the body portion  10 . In the present embodiment, the lighting module  12  may be fixed on the upper surface of a heat-dissipating element  20 . The heat-dissipating element  20  may be formed by an aluminum-extrusion method and is used for dissipating heat generated from the lighting module  12 . In addition, the heat-dissipating element  20  may be electrically connected to different circuit boards (not shown), for example, a LED control circuit board or a drive circuit board, and the circuit boards may be mounted on the heat-dissipating element  20 . Therefore, the heat-dissipating element  20  is further provided for dissipating heat generated from the circuit boards. 
     The optical structure  11  is formed integrally with the body portion  10 . For example, the extrusion technology for forming polymers into plastic products is used for manufacturing the body portion  10  and the optical structure  11  integrally. Depending on the optical and physical properties, a single polymer, for example polycarbonate (PC) or poly methylmethacrylate (PMMA), is used for manufacturing the body portion  10  and the optical structure  11 . Alternatively, at least two polymers, for example polycarbonate (PC) and poly methylmethacrylate (PMMA), are used to form the body portion  10  and the optical structure  11  by the co-extrusion method. For example, the PC material can be the product type with LN-2250Z available from Teijin. The PC material has high strength, low moisture absorption (i.e., the moisture absorption is about 2%), high flame-retarding property (V-0 degree), and small deformation (i.e., shrinkage ratio is about 0.5% to 0.7%). Moreover, the transparency of LN-2250Z is about 88%. On the other hand, the PMMA material can be the product type with CM-205, CM-207, or CM-211 available from CHI MEI CORPORATION. The PMMA material has moisture absorption of 3% and transparency of 92%. The above-mentioned available products may be used in the present invention. 
     Moreover, in the LED luminaire  1  manufactured by the co-extrusion method, the optical structure  11  is formed inside the body portion  10  and located in the light-projection direction of the lighting module  12  (shown by arrows). The optical structure  11  is an arc-plate protruding along the light-projection direction of the lighting module  12 . The optical structure  11  substantially has a first surface  111  and a second surface  112 , and the two surfaces  111 ,  112  are not parallel to each other. As shown in  FIG. 1 , the first surface  111  is farther from the lighting module  12  than the second surface  112 . The first surface  111  has larger curvature than that of the second surface  112 , and the curvature of the first surface  111  can be smaller or equal to the curvature of a straight line (i.e., the curvature of a straight line is infinite). Because of the curvature difference between the two surfaces  111 ,  112 , the light generated from the lighting module  12  is initially refracted by the second surface  112 , followed with another refraction by the first surface  111 . Due to the two refractions, the view angle of the light generated from the lighting module  12  can be increased after passing through the first surface  111  and the second surface  112  of the optical structure  11 . 
     Please refer to  FIGS. 2A to 2C ; the second embodiment of the present invention is shown. Different from the first embodiment, the second embodiment&#39;s first surface  111  has at least two side portions  1111  and a middle portion  1112  arranged between the two side portions  1111 . Namely, the first surface  111  has modified structures to increase the view angle of the light produced by the lighting module  12 . In  FIG. 2B , one side portion  1111  is defined by the connection of an end point “b 1 ” (i.e., the end point in connection of the middle portion  1112 ) and an end point “c 1 ” (i.e., the end point in connection with the body portion  10 ), and the other side portion  1111  is defined by the connection of an end point “b 2 ” (i.e., the end point in connection of the middle portion  1112 ) and an end point “c 2 ” (i.e., the end point in connection with the body portion  10 ). In other words, the two side portions  1111  can be represented by section of “b 1   c   1 ” and “b 2   c   2 ”. The middle portion  1112  is defined by connection of the end point “b 1 ” and the end point “b 2 ”, and can be represented by section of “b 1   b   2 ”. In the present embodiment, the two side portions  1111  have a first curvature, and the first curvature is greater than the second curvature of the second surface  112 . For example, in the present embodiment, the radius of the body portion  10  is 17.25 mm, and the radius of the side portions  1111  of the optical structure  11  is 19.12 mm. The radius of the second surface  112  of the optical structure  11  is 20.45 mm. Based on the definition of the curvature, which is equal to the reciprocal of the radius; the first curvature is calculated to be greater than the second curvature, and the first curvature is smaller than the curvature of a straight light. 
     In addition, the middle portion  1112  can be an arc surface with a plurality of continuous curvatures (i.e., the spline). As shown in  FIG. 2C ; the line A of  FIG. 2C  represents the curvature change of the spline of the present embodiment. The end points of “a”, “b 1 ”, and “b 2 ” correspond to the middle portion  1112  shown in  FIG. 2B . Symmetric at end point “a”, the curvature of the spline changes linearly from end point “a” to end point “b 1 ” and to end point “b 2 ”. In an exemplary embodiment, the coordinate of end point “a” is (0, 8.608), and the coordinates of end point “b 1 ”, “b 2 ” are respectively (−3.5, 8.712) and (3.5, 8.712). Therefore, the width of the middle portion  1112  is 7 mm. However, the width of the middle portion  1112  can be different depending on the size of the lighting module  12 . Dimensionally, the width of the middle portion  1112  ranges from half to three times of the size of the lighting module  12 . Therefore, by combining the structural variation of the side portions  1111  and the middle portion  1112 , the view angle of the light is increased and improves the uniformity of light projection. Furthermore, the thickness of each of the side portions  1111  is greater than that of the middle portion  1112 . 
     Please refer to  FIG. 2A  again. For the second embodiment of the present invention, the second surface  112  of the optical structure  11  has a circular center  112 C and the body portion  10  has a circular center  10 C (i.e., a core). The circular centers  10 C,  112 C are coaxial and are located on the same light axis “L”. The two side portions  1111  are arc-surfaces with the same curvature but have different circular centers  1111   c  (i.e., two circular centers are shown in  FIG. 2A ). The circular centers  1111   c  of the two side portions  1111  are symmetric to the light axis “L,” which is coaxial with the axis defined by the circular centers  10 C,  112 C. 
     With reference to  FIG. 1  and  FIG. 2A , the LED luminaire  1  has two accommodating rooms thereinside. The first accommodating room  101  is constructed by the first surface  111  of the optical structure  11  and the inner surface of the body portion  10 . The second accommodating room  102  is constructed by the second surface  112  of the optical structure  11  and the inner surface of the body portion  10 . The body portion  10  of the LED luminaire  1  further has a first fixing portion  103  in the second accommodating room  102  for holding the heat-dissipating element  20 . The lighting module  12  may be mounted on the heat-dissipating element  20 . The light generated from the lighting module  12  projects to and passes through the first surface  111  and the second surface  112  to increase the view angle of the LED luminaire  1 . Furthermore, with the structural variations of the first surface  111  as shown in  FIG. 2A , the light projected from the lighting module  12  is more uniform as well as an increase of the view angle of the LED luminaire  1 . Please refer to  FIG. 3 ; the light shape of the lighting module  12  that is mounted in the second embodiment is shown. The figure shows the view angle has increased to approximately 140 degrees, which improves the projection ability of light generated by LED. 
     Specifically, the position of the optical structure  11  in the LED luminaire is defined as follows. The distance between the optical structure  11  and the lighting module  12  can be zero, so the second surface  112  of the optical structure  11  contacting the lighting emitting surface  121  (i.e., top surface) of the lighting module  12 . The distance between the optical structure  11  and the lighting module  12  can be as zero to two-thirds of the distance defined by the lighting emitting surface  121  of the lighting module  12  and the inner surface of the body portion  10  in the direction of the light axis L. In other words, the position of the optical structure  11  may be preferably located in zero to two-thirds of the distance between the lighting emitting surface  121  of the lighting module  12  and the body portion  10  in the direction of light axis L. In addition, to minimize the effect of heat generated by the lighting module  12  on the optical structure  11 , a space is recommended between the lighting module  12  and the optical structure  11  and the space is preferred greater than 1 mm in the direction of the light axis L. 
     Please refer to  FIG. 4 ; a modification of the second embodiment is shown. The first curvature of the two side portions  1111  are equal to the curvature of a straight line (i.e., the curvature of a straight line is infinite). The connection of the end point “b 1 ” (i.e., the first end point in connection to the middle portion  1112 ) and the end point “c 1 ” (i.e., the second end point in connection to the body portion  10 ) is a straight line. The connection of the end point “b 2 ” (i.e., the end point in connection to the middle portion  1112 ) and the end point “c 2 ” (i.e., the end point in connection with the body portion  10 ) is also a straight line. In other words, for the side portions  1111 , the position of each of end points connecting to the body portion  10  (so-called as the first end point) is equal to or lower than a position of each of the end points connecting to the middle portion  1112  (so-called as the second end point). In terms of optical design, the position of end point “c 1 ” (the first end point) is equal to or lower than that of end point “b 1 ” (the second end point), and the position of end point “c 2 ” (also the first end point) is equal to or lower than that of end point “b 2 ” (also the second end point). Under the condition that the first curvature must be larger than the second curvature, the curvature of the two side portions  1111  (i.e., the sections b 1   c   1  and b 2   c   2 ) is equal to or smaller than the curvature of a horizontal line. 
     Please refer to  FIG. 5 ; another modification of the second embodiment is shown. The side portions  1111  are arc-surfaces with the same circular center (i.e., circular center  1111 C). In other words, the side portions  1111  are two portions which can be substantially connected as a circle. In the exemplary embodiment, the side portions  1111  have the same circular center as the circular center  1111 C. 
     Furthermore, the lighting module  12  may be located in a lower position in the second accommodating room  102  of the body portion  10 . The resultant distance between the optical structure  11  and the lighting module  12  is within the allowable distance in the preceding description. 
     Please refer to  FIG. 6 ; a modification of the embodiment of  FIG. 5  is shown. Three lighting modules  12  are placed on the heat-dissipating element  20 . The first surface  111  of the optical structure  11  has three middle portions  1112  of spline corresponding to the three lighting modules  12  respectively. For example, the left lighting module  12  corresponds to the middle portion  1112  of “b 3   b   5 ” section. The middle portions  1112  have the same width with the middle portion  1112  of the second embodiment. Therefore, the body portion  10  can hold a plurality of lighting module  12  therein. The first surface  111  of the optical structure  11  can have a plurality of side portions  1111  (i.e., the sections c 1   b   5 , b 3   b   1 , b 2   b   4 , and b 6   c   2 ) and a plurality of middle portions  1112  (i.e., the sections b 5   b   3 , b 1   b   2 , and b 4   b   6 ). The width of each middle portion  1112  is ranged from one half up to three times of the corresponding lighting module  12 . For the present modification, the side portions  1111  are arc-surfaces with the same circular center  1111   c . In other cases, the side portions  1111  are arc-surfaces with the same curvature but have different circular centers. Alternatively, the side portions  1111  can be classified in two groups: the side portions  1111  at left portion of the light axis “L” and the side portions  1111  at right portion of the light axis “L”. The side portions  1111  at left portion of the light axis “L” have a circular center and the side portions  1111  at right portion of the light axis “L” have another circular center. Moreover, the two circular centers are symmetrical of the light axis “L”. All the above modifications are part of the present invention. 
     Please refer to  FIG. 7 ; the third embodiment is shown. The optical structure  11  is formed inside the body portion  10  and located in the light-projection path of the lighting module  12 . The optical structure  11  substantially has a first surface  111  and a second surface  112 , and the two surfaces  111 ,  112  are not parallel to each other. The first surface  111  consists with two side portions  1111  and a middle portion  1112  between the two side portions  1111 . In the present embodiment, the optical structure  11  or the light-projecting area of the body portion  10  may have optical micro-structure thereon for improving the light uniformity. As shown in  FIG. 7 , the second surface  112  of the optical structure  11  has a plurality of convex portion  1121  of the optical micro-structure  112 , and the convex portions  1121  may be formed integrally with the optical structure  11  and the body portion  10  by the co-extrusion method. Therefore, the view angle of the LED luminaire is increased and the convex portions  1121  of the optical micro-structure are used to improve light uniformity. 
     Please refer to  FIG. 8 ; the fourth embodiment is shown. The optical structure  11  is formed inside the body portion  10  and located in the light projection path of the lighting module  12 . The optical structure  11  substantially has a first surface  111  and a second surface  112 , and the two surfaces  111 ,  112  are not parallel to each other. The first surface  111  consists with two side portions  1111  and a middle portion  1112  in between the two side portions  1111 . In the present embodiment, the body portion  10  further has a second fixing portion  104  in the first accommodating room  101  for assembling an optical element  13 . The optical element  13  may be a diffuser sheet or a brightness enhancement film. Therefore, the view angle of the LED luminaire is increased and the optical element  13  can be used to improve light uniformity. 
     Based on the above descriptions, the present invention can offer one or more advantages as below. 
     1. The co-extrusion method is used to form the optical structure integrally with the body portion. The optical structure has a first surface and a second surface, and the two surfaces are not parallel to each other, such that the light passes through the two surfaces is refracted to increase the view angle of the LED luminaire. Specifically, the view angle for the LED tube is increased in the transverse direction perpendicular to the tube shaft of the body portion. 
     2. The view angle of the LED luminaire can be increased also. Therefore, the structure of the present invention can be used to solve the hot spot issue when using LEDs with the same size 
     3. To improve the uniformity of light generated by LED, the present invention uses the co-extrusion method to form the micro-structure, such as the convex portions on the bottom surface of the optical structure. In addition, other surface modifications to the optical structure and the addition of auxiliary optical elements also contribute to the improvement. 
     The descriptions illustrated supra set forth simply the preferred embodiments of the present invention; however, the characteristics of the present invention are by no means restricted thereto. All changes, alternations, or modifications conveniently considered by those skilled in the art are deemed to be encompassed within the scope of the present invention delineated by the following claims.