Abstract:
A non-specular skylight collimator has at least two axially successive collimator segments from top to bottom, with the segments becoming successively less flared from top to bottom. A skylight diffuser assembly typically covers the open end of the bottom segment.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to skylight collimators. 
     BACKGROUND OF THE INVENTION 
     Briefly, a tubular skylight such as those mentioned in U.S. Pat. Nos. 5,896,713 and 6,035,593, both of which are owned by the same assignee as is the present invention and both of which are incorporated herein by reference, includes a tube assembly mounted between the roof and ceiling of a building. The top end of the tube assembly is covered by a roof-mounted cover, while the bottom end of the tube assembly is covered by a ceiling-mounted diffuser plate. With this combination, natural light external to the building is directed through the tube assembly into the interior of the building to illuminate the interior. 
     As understood herein, the tube with vertical sides reflects light in the same angle each reflection, which angle depends on the sun&#39;s elevation in the sky and thus varying throughout the day, limiting the efficiency and effectiveness of the diffuser in controlling the distribution of light in the building. 
     SUMMARY OF THE INVENTION 
     The present invention has recognized that to optimize the light transmission through the cover, a collimator may be provided above the diffuser, and furthermore the collimator need not be specular. 
     Accordingly, a skylight assembly includes a skylight shaft and a collimator assembly operably engaged with the shaft. The collimator assembly includes an axial series of multiple collimator segments. In the limit in which the number of segments in the series approaches infinity, the collimator assumes a curved shape in longitudinal cross-section. A first collimator segment defines a first collimating angle with respect to an axis of the collimator assembly and subsequent collimating segments define respectively different (and steeper) collimating angles with respect to the axis. The collimating angles can be oblique. The collimating angles (and in the limiting case, the curve of the assembly) can be established by the desired degree of collimation, the expected range of angles at which sunlight enters the assembly, and the diameter of the entrance to the collimator. 
     In some examples, the collimating assembly includes a third collimating segment defining a third collimating angle different from the first and second collimating angles. The collimating segments can be successively less flared than each other. An upper collimating segment can be more flared than a lower collimator segment. The inside surface of the collimating assembly may be non-specular. 
     In another embodiment, a skylight collimator assembly has a first frustum-shaped collimator segment defining a first cone angle and a second frustum-shaped collimator segment connected to the first segment and coaxial therewith. The second segment defines a second cone angle more acute than the first cone angle. 
     In another aspect, a skylight has a skylight tube defining an upper end and a lower end, a skylight cover disposed above the upper end and permitting light to enter the tube, and a collimator assembly disposed below the lower end to receive light therefrom. The collimator assembly has a non-specular inside surface. A diffuser is disposed below the lower end of the collimator assembly. In some embodiments the assembly has multiple collimator segments. 
     The details of the present invention, both as to its structure and operation, can best be understood in reference to the accompanying drawings, in which like reference numerals refer to like parts, and in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view in partial cross-section of an example non-limiting tubular skylight showing an example environment of the collimator; 
         FIG. 2  is a cross-sectional view of the collimator as seen along the line  2 - 2  in  FIG. 1 ; 
         FIG. 3  is a side schematic view showing collimator parameters; 
         FIG. 4  is a side schematic view of an alternate collimator assembly in which the number of segments approaches infinity, effectively establishing a collimator that is continuously curved at ever-steeper tangents in the longitudinal dimension; 
         FIG. 5  is a perspective view of an alternate collimator having a round-to-square configuration; 
         FIG. 6  is an elevational view of the collimator shown in  FIG. 5 ; and 
         FIG. 7  is a top plan view of the collimator shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to  FIG. 1 , a tubular skylight made in accordance with the present invention is shown, generally designated  10 , for lighting, with natural sunlight, an interior room  12  having a ceiling dry wall  14  in a building, generally designated  16 .  FIG. 1  shows that the building  16  has a roof  18  and one or more joists  20  that support the roof  18  and ceiling dry wall  14 . 
     As shown in  FIG. 1 , the skylight  10  includes a rigid hard plastic or glass roof-mounted cover  21 . The cover  21  is optically transmissive and preferably is transparent. 
     The cover  21  may be mounted to the roof  18  by means of a ring-like metal flashing  22  that is attached to the roof  18  by means well-known in the art. The metal flashing  22  can be angled as appropriate for the cant of the roof  18  to engage and hold the cover  21  in the generally vertically upright orientation shown. 
     As further shown in  FIG. 1 , an internally reflective hollow metal shaft assembly, generally designated  24 , is connected to the flashing  22 . The cross-section of the assembly  24  can be cylindrical, rectangular, triangular, etc. Accordingly, while the word “tube” is used from time to time herein, it is to be understood that the principles of the present invention are not to be limited to a tube per se. 
     The shaft assembly  24  extends to the ceiling  14  of the interior room  12 . Per the present invention, the shaft assembly  24  directs light that enters the shaft assembly  24  downwardly to a light diffuser assembly, generally designated  26 , that is disposed in the room  12  and that is mounted to the ceiling  14  or to a joist  20  as described in the above-mentioned &#39;593 patent. 
     The shaft assembly  24  can be made of a metal such as an alloy of aluminum or steel, or the shaft assembly  24  can be made of plastic or other appropriate material. The interior of the shaft assembly  24  is rendered reflective by means of, e.g., electroplating, anodizing, metallized plastic film coating, or other suitable means. 
     In one example embodiment, the shaft assembly  24  is established by a single shaft. However, as shown in  FIG. 1 , if desired, the shaft assembly  24  can include multiple segments, each one of which is internally reflective in accordance with present principles. Specifically, the shaft assembly  24  can include an upper shaft  28  that is engaged with the flashing  22  and that is covered by the cover  21 . Also, the shaft assembly  24  can include an upper intermediate shaft  30  that is contiguous to the upper shaft  28  and that can be angled relative thereto at an elbow  31  if desired. Moreover, the shaft assembly  24  can include a lower intermediate shaft  32  that is slidably engaged with the upper intermediate shaft  30  for absorbing thermal stresses in the shaft assembly  24 . And, a collimator-like lower shaft  34  can be contiguous to the lower intermediate shaft  32  and join the lower intermediate shaft  32  at an elbow  35 , with the bottom of the lower shaft  34  being covered by the diffuser assembly  26 . The elbow  35  is angled as appropriate for the building  16  such that the shaft assembly  24  connects the roof-mounted cover  21  to the ceiling-mounted diffuser assembly  26 . It is to be understood that where appropriate, certain joints between shafts can be mechanically fastened and covered with tape in accordance with principles known in the art. 
     As shown in  FIG. 2 , the collimator-like lower shaft  34  referenced in  FIG. 1  is presented in greater detail. As may now be appreciated, in non-limiting embodiments the collimator-like lower shaft  34  has an axial series of multiple collimator segments. It may further be appreciated that each collimating segment of the shaft  34  is successively less outwardly-flared from top to bottom than the one immediately above it. 
     The collimator-like lower shaft  34  shown in  FIG. 2  has a top  36  and a bottom  38 . The top  36  of the shaft  34  may be contiguously engaged to the lower intermediate shaft  32  as described in reference to  FIG. 1  above. The bottom  38  of the shaft  34  may be covered by the diffuser assembly  26  as also described above. The bottom of the collimator may also be left open without a diffuser assembly engaged therewith. 
     Also as stated above, the shaft  34  has multiple collimating segments. In some embodiments the collimating segments are frusto-conical. In other embodiments they may assume other collimating shapes, e.g., frusto-pyramidal. 
     Thus, there may be a first frustum-shaped collimating segment  40  defining a first collimating angle α 1  with respect to an axis of the collimator assembly  34  and a second frustum-shaped collimating segment  42  connected to the segment  40  and defining a second collimating angle α 2  that is less than the first collimating angle with respect to an axis of the collimator assembly  34 . Furthermore, in non-limiting embodiments there may also be a third frustum-shaped collimating segment  44  connected to the segment  42  and defining a third collimating angle α 3  that is less than the first and second collimating angles. It is to be further understood that each collimating angle referenced in the present application may be oblique. Additional segments may be provided in accordance with disclosure below. 
     Still referencing  FIG. 2 , the collimating segment  40  is more flared than the collimating segment  42 . Similarly, in non-limiting embodiments that include a third collimating segment  44 , the collimating segment  42  is more flared than the third collimating segment  44 . Should there be more than three collimating segments, each upper collimating segment may be more flared than the one below it. 
     Last, it may also be appreciated from  FIG. 2  that there is an inside surface  46  of the collimating assembly  34 . The inside surface  46  of the assembly  34  is understood to be non-specular in non-limiting embodiments. Examples of such non-specular surfaces are disclosed in the present assignee&#39;s U.S. Pat. No. 7,146,768 and USPPs 2006/0191214 and 2007/0266652, incorporated herein by reference. In brief, the non-specular inside surface can be established by a structured surface in the metal substrate, reflective film or adhesive on the film. It can be in the form of dimples, corrugated patterns or other shapes known to provide a controlled spread of light of, e.g., less than about ten degrees. Using a non-specular surface provides a controlled light spread as desired, e.g., a spread of light that is less than plus or minus five degrees from the central reflected ray of light. 
     The multi-stage collimator described above advantageously consumes less axial space than a single stage collimator yielding equivalent performance. 
     With greater specificity and with the understanding that the discussion below is not intended to limit the invention but rather provide background explanation, the following terms are used. Refer to  FIG. 3 . “SALT” (in degrees) refers to the solar altitude, angle of the sun from the horizontal plane, and the angle of the sunlight reflecting down a parallel walled tube. “TT” (degrees) refers to the tube taper, angle from vertical and/or parallel, while “ALT” (in degrees) refers to the alignment angle of light after reflecting off of the tapered wall. This angle is in relation to a horizontal plane. Then:
 
TT=((ALT)−(SALT))/2 and ALT=(2)(TT)+(SALT)
 
     Present principles can be used to provide a single reflection, variable tapered tube that is optimally designed to realign sunlight while minimizing reflective material and space of the collimator. 
     In example embodiments and now referring to  FIG. 3 , dimensions of the first (top) segment may be determined using the following equations:
         DIATOP(inches)=Diameter of tapered tube at the top or light entrance;   DIATT(inches)=Diameter of tapered tube where light is reflected based on light entering the tapered tube from the top diameter at a specific SALT and light reflected at a specific ALT requirement;   HTTT(inches)=Height of tapered tube at the related DIATT; then
 
DIATT=(2)((DIATOP)(tan SALT))/((1/tan TT)−(tan SALT))+(DIATOP)
 
HTTT=(DIATT-DIATOP)/(2 tan TT) where “TT” is the angle of tube taper relative to the vertical axis.
       

     Each consecutive segment diameter and height can be determined from the previous segments values as follows: 
     N is new value, P is previous value and AP is ½ the increase in diameter from DIATOP to DIATTP. Thus using the example in the table below to determine HTTTN for the collimator @ a SALT of 35 degrees, AP would be (13.64−10.0)/2=1.82″.
 
HTTTN=((DIATOP+ AP )(tan SALTN)−(HTTTP)(tan SALTN)(tan TTN))/1−(tan SALTN)(tan TTN)
 
DIATTN=DIATTP+(2)(HTTTN−HTTTP)(tan TTN)
 
     Preferably, light undergoes only one reflection in the variable tapered tube to provide the required alignment angle. 
     With the above in mind, for a variable tapered tube that provides an alignment angle (ALT, the axis of the light spread as shown) greater than or equal to 55 degrees with an input range of light (SALT) from 15 degrees up to 55 degrees, the following dimensions may be used. The below table is in increments of ten degrees/five segments of (SALT). For this example, the top of the tapered tube opening is assumed to be ten inches in diameter. An example multiple stage collimator is shown in  FIG. 4 . 
     
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                   
               
               
                   
                 SALT 
                 TT 
                 Tube Dia. 
                 Tube height 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 15° 
                 20° 
                 12.16″ 
                 2.96″ 
               
               
                   
                 25 
                 15 
                 13.64 
                 5.51 
               
               
                   
                 35 
                 10 
                 14.91 
                 8.72 
               
               
                   
                 45 
                  5 
                 15.81 
                 12.90 
               
               
                   
                 55 
                  0 
                 16.04 
                 18.59 
               
               
                   
                   
               
             
          
         
       
     
     The multiple stage collimator results in smaller dimensions than were a single stage collimator to be used with a taper angle of eight degrees to accomplish the same requirement. Such a single stage collimator would be expected to be fully one third-longer in axial dimension and six percent greater in diameter than the multi-stage collimator of equivalent performance. 
     In addition to saving space, use of a non-specular inside surface with controlled light spread in the present collimator can reduce glare and non-uniform illumination associated with using a specularly reflective surface. A non-specular surface provides a controlled spread of light, less than approximately ten degrees, which eliminates the problems mentioned above, without unduly affecting the alignment angle since there is only one reflection. 
     It may now be appreciated that use of a multi-stage collimator changes the angle of low angle sunlight to a consistent high angle and, when a non-specular inside surface is used, with a minimum of glare. By maintaining relatively high angles to the diffuser/glazing independent of the solar altitude, consistent glazing efficiencies are maintained throughout the day. Furthermore, by establishing the downward angle of the sunlight and slightly spreading the light at the same time as described above, in some examples no diffuser need cover the open bottom end  38  of the collimator, simulating a recessed lighting fixture. Present principles also provide a consistent angular controlled light source for any light directing pendent or other optical element placed under the variable tapered tube. 
     A collimator assembly  100  may be provided as shown in  FIG. 4  that has more than three stages and indeed may have a number of stages that approach the limit of infinity, i.e., each stage effectively has little or no thickness in the longitudinal dimension. Accordingly, the collimator  100  assumes a continuously curved shape in the longitudinal dimension as shown in  FIG. 4  in which tangents  102  to the surface with respect to the longitudinal axis  104  of the collimator progressively define steeper angles from the collimator&#39;s light entry to the light exit. The equations above may be used at each axial location to establish the tangent at that location. The reflection angles and collimator dimensions shown in  FIG. 4  are exemplary only and not limiting. 
     A collimator assembly  200  is shown in  FIGS. 5-7  that has, from a round top opening  202  to a rectilinear bottom opening  204 , multiple collimator stages  206 ,  208 ,  210 , with the stages  206 - 210  being successively less flared than the next upper stage. Thus, the assembly  200  in  FIGS. 5-7  is substantially identical to the collimators discussed above with the exception of the round to square configuration from top to bottom as shown. To achieve the round-to-square configuration, in which the top opening  202  may mate with the bottom of a cylindrical skylight tube while the bottom opening  204  may mate with a rectilinear diffuser or ceiling opening, the stages  206 - 210  transition progressively in the axial dimension from mostly round (the top stage  206 ) to predominantly rectilinear (bottom stage  210 ) as shown. 
     While the particular SKYLIGHT COLLIMATOR WITH MULTIPLE STAGES is herein shown and described in detail, it is to be understood that the subject matter which is encompassed by the present invention is limited only by the claims.