Abstract:
A blind with angled slats where the sides are of unequal length allowing light transmission in the open and intermediate positions, no light transmission in the closed position and a flush planar surface in the closed position.

Description:
FIELD OF THE INVENTION 
     The present invention relates to Venetian blinds with angled slats in general and, in particular, to angled slats having unequal wings with circular holes for receiving cords located near the edge of the short wing of the slat for the purpose of allowing maximum light transmission in the open and intermediate positions and minimum light transmission in the closed position while further providing a flush planar surface in the closed position. 
     BACKGROUND OF THE INVENTION 
     The prior art contains angled blinds with equal wings, an apex at the junction of the wings and slots that pass through the apex and continue toward the respective edges of both wings or one wing or the other only. Common elements in prior art blinds are a head box, ladder-shaped supporting cords for supporting the slats and for tilting the slats and a bottom rail connected to lifting cords connected to the bottom rail which pass though lifting cord slats and into the head box. 
     U.S. Pat. No. 2,633,191 to R. Curtis, Jr. discloses an angle slatted blind with slots extending from the apex toward each wing of the slat. Curtis further disclosed angled slats that when tilted to a closed position have all of the vertical sections of the slat in a common plane. Specifically, the apex (Curtis calls it the angular free edge) of each bar is brought close to the apex of the lower adjacent bar. 
     U.S. Pat. No. 4,799,526 to John R. Reeves discloses a blind using angled shaped slats with lifting cord holes that are in the apex and extend only slightly beyond the apex into the respective slat wings. Reeves further discloses a blind that can be tilted so that all of the first sections are in the same vertical plane or alternatively all of the second sections are in the same vertical plane. 
     U.S. Pat. No. 5,423,367 to Mamoru Kataoka, et. al discloses an angle shaped slat with a slot that includes the apex and extends from the apex toward the edge of only one wing of the slat. The &#39;367 slats specifically overlap in the vertical position in order to prevent the leakage of light from the slot. 
     Angled shaped slats have the advantage of giving structural rigidity to the slat so that no more than two (in normal windows) lifting cords and two ladder shaped supporting cords are necessary. The advent of new lightweight materials such as polyvinyl chloride foam and pressed bamboo create opportunities for designing blinds that are relatively thin and lightweight while having aesthetic appeal. Blind slats made from such lightweight materials require additional structural rigidity that can be easily obtained by means of an angle shape. An additional reason for the angle shape is that lifting cords and ladder shaped supporting cords detract from the blinds appearance and cost more in materials and time to assemble. Angle shaped slats are known in the prior art; however, both wings of the angle shaped slats are equal in the prior art blinds. The prior art angle shaped blind will transmit less light than a conventional blind because of the large profile presented when in intermediate or open positions. Thus, it is usual for prior art blinds to have one wing of the angle shaped blind made from light transmitting material. When the light transmitting wing of the angle shaped slat is in the vertical position, light passes through; however, one cannot see completely through the blind as with a conventional blind. When the non-light transmitting wing of the blind is in the vertical position, light will leak through the slots unless the blinds overlap to cover the slot. Therefore, there is no design in the prior art to take advantage of the new lightweight materials that can also maximize transmission of natural light while achieving a smooth planar surface when closed with no leakage of light through slats. 
     Therefore, a need exists for an angle shaped slat that can provide the advantages of the strength of the angle shape, allow viewing through the blinds when open, have the aesthetically desirable effect of a smooth planar surface facing into the room when closed by having all of the vertical sections in the same plane and preventing light leakage through the holes when closed. 
     SUMMARY OF THE INVENTION 
     The present invention meets the needs identified above by having an angle shaped slat with one long wing and one short wing, and circular holes for receiving cords located near the outside edge of the short wing of the slat. In this way the long wings of the slats will be in the same vertical plane when the blind is closed. In an intermediate position light can pass in increasingly greater degrees reaching a maximum when the long wing is horizontal. Leakage of light through the holes does not occur because in the closed position the long wing in the vertical plane will approach the apex of the slat beneath it, and the hole of the lower slat will be well above the end of the long wing of the higher slat. Therefore, the angle shaped slat with unequal wings and round holes meets the needs beyond the prior art by providing both aesthetic and functional capabilities that cannot be achieved by any one of the prior art blinds alone. 
     The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawing wherein like reference numbers represent like parts of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the invention. 
     FIG. 2A is an end view of equal winged prior art blinds. 
     FIG. 2B is a perspective view of a portion of prior art angle shaped slat with slots extending from the apex toward both edges of the slat. 
     FIG. 2C is a perspective view of a portion of prior art angle shaped slat with slots extending from the apex toward one edge only of the slat. 
     FIG. 3 is a side view of the invention with the slats of the blind in full open position 
     FIG. 4 is a side view of the invention with the slats of the blind in full closed position. 
     FIG. 5 is a perspective of the angle shaped slat with unequal sides and holes 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows the assembled blind  10  made up of box  12 , ladder  20 , slat  30 , lifting cord  26  and bottom rail  14 . Also shown are the crank arm  15 , the handle  16  and the drawstring  18  and the drawstring runner  19 . Holes  36  for the lifting cords cannot be seen in this front perspective view (See FIGS. 3,  4  and  5 ). The gear mechanisms located within box  12  are well known to persons skilled in making Venetian blinds and are not shown. Blind  10  is operated by pulling drawstring  18  to release the blinds and letting them fall to full extension (shown) and then grasping handle  16  and turning it in order to rotate lever arm  15  which will cause ladders  20  to tilt further causing slats  30  to tilt. 
     FIGS. 2A,  2 B and  2 C show prior art blinds with angle shaped slats with equal wings and slots extending from the apex either in both directions toward the outside edge of the prior art slat (FIG. 2B) or from the apex toward only one outside edge of the prior art slat (FIG.  2 C). 
     FIG. 3 depicts blind  10  viewed from the side. Blind  10  is oriented so that long wing  31  of slat  30  is pointing into the room and toward a person inside a room looking out through the blinds (not shown). Lifting cord  20  is hanging fully extended and without tilting. Cord  26  is fully extended and runs from box  12  through holes  36  to rail  14  where it is anchored to rail  14  at point  13 . In FIG. 3, an end view of slat  30  can be seen with long wing  31  and short wing  32 . In the preferred embodiment, slat  30  is made of polyvinyl chloride foam. Other embodiments of slat  30  can be made from polyvinyl chloride, polypropylene, plastic, polyurethane or pressed bamboo. However, slat  30  can be made from any suitable material. Short wing  32  has hole  36  for receiving cord  26 . The diameter of hole  36  is greater than the diameter of cord  26  in order to ensure free passage of cord  26  through hole  36 . In the preferred embodiment, the diameter of hole  36  is 0.125 inch; however, the diameter can be any size sufficient to ensure the free passage of cord  26 . Ladder  20  has front  22 , rear  21  and support  23 . Slat  30  rests on support  23  at the junction of support  23  with front  22  and rear  21 . 
     FIG. 4 shows blind  10  in the closed position. Ladder  20  has been tilted so that front  22  drops and rear  21  rises with the result that long wing  31  of slat  30  tilts downward and short wing  32  of slat  30  tilts upward. Ladder  20  has been tilted so that front wing  31  is vertical and front edge  39  rests on the junction of front  22  and support  23  of ladder  20 . Edge  39  of long wing  31  may either touch short wing  32  or hang a short distance above short wing  32 ; however, edge  39  does not extend beyond apex  35 . 
     In FIG. 5, slat  30  is shown in a shortened view. Slat  30  has long wing  31  and short wing  32  which meet at apex  35 . Slat  30  further has holes  36 , right edge  33 , left edge  34 , front edge  39  and rear edge  38 . In the preferred embodiment, the interior angle at the junction of short wing  32  and long wing  31  at apex  35  is 150°. Experimentation has shown that 150° is the optimum angle for the interior angle between long wing  31  and short wing  32 . A variation of ±20° is acceptable. Therefore, the interior angle z defined by the junction of long wing  31  and short wing  32  meeting at apex  35  is in the range from 130° to 170° (130°≦z≦170°). Experimentation has shown that the optimum width of short wing  32  measured from rear edge  38  to apex  35  is 0.35 times the width of long wing  31  measured from front edge  39  to apex  35 . If x=width of long wing  31  and y=width of short wing  32 , then the respective widths are defined as y=0.35x. Therefore, the range of values defining the width of short wing  32  where x=the width of long wing  31  and y=the width of short wing  32  is y is less than or equal to 0.40x and y is greater than or equal to 0.30x. 
     Holes  36  are located in short wing  32 . If short wing  32  were divided in half lengthwise by an imaginary line running down the middle parallel to apex  35 , then the geometric center of the circles defined by of holes  36  would lie within the half of short wing  32  which is the outside half or the side having edge  38 . In the preferred embodiment, slat  30  is 23 inches long and the geometric center of the circles defined by holes  36  are located 5 inches from right edge  33  and from left edge  34 . For other embodiments, the location of holes  36  can be defined as follows. If L is the length of slat  30 , then the geometric center of the circles defined by holes  36  will be located at a distance from right edge  33  and left edge  34  defined by 0.22 L. The range of the location can vary from 0.18 L to 0.26 L. Where y is the width of short wing  32 , then the geometric center of the circles defined by holes  36  will not be any nearer rear edge  38  than 0.25y and not closer to apex  35  than 0.50y. 
     If hole  36  is too close to the edge then the material may break. Moreover, if holes  36  are too close to the apex then the advantageous effect of the unequal wings will not be achieved. In addition to allowing a flat planar surface when in the full closed position, slat  30  achieves a uniformity of spacing so that the slats at the bottom are evenly vertical like the slats at the top. Furthermore, in intermediate positions, where the slats are open up to the full horizontal position for long wings  31 , there will be no aggregation of space caused by lifting cords  26  because lifting cords  26  do not move forward within a slot but remain positioned in the rear half of short wing  32 . Therefore, the angle of tilt of slats  30  near rail  14  will be very close or similar to the angle of tilt for slats  30  near box  12 . An difference in the angle of tilt going in slats  30  due to contact of lifting cords  26  with the forward edge of a slat is avoided. 
     It will be understood from the foregoing description that various modifications and changes may be made in the preferred embodiment of the present invention without departing from its true spirit. It is intended that this description is for purposes of illustration only and should not be construed in a limiting sense. The scope of this invention should be limited only by the language of the following claims.