Abstract:
A lighting system is provided to transmit light from a light source through a prism. The prism includes a light receiving edge surface, a curved edge surface and a light exiting edge surface. The light source is positioned to transmit a beam of light through the light receiving edge surface of the prism. The prism is configured such that the beam of light travels through the prism to strike the curved edge surface. The beam of light is then reflected off of the curved edge surface such that the beam of light changes direction and continues to travel through the prism until such time as it passes through the light exiting edge surface. The lighting system is adapted to provide a substantially uniform light distribution from the light exiting edge surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. provisional application Ser. No. 60/339,518, filed on Dec. 11, 2001. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to lighting systems, and more particularly, to lighting systems for appliance products, such as, for example, vacuum cleaners, stoves, refrigerators, microwaves, toasters, coffee makers, bread makers, other kitchen and household appliances, and other similar and various other related devices. 
     BACKGROUND AND SUMMARY OF THE INVENTION 
     Most prior art lighting systems used in appliances employ incandescent bulbs, which have many design disadvantages when trying to place them in small enclosures due to their relatively large size, short usage life and high heat generation. There is a need for a lighting system that uses a small bulb, such as an LED, which has a long life, does not have high heat generation, and can project sufficient light across the expanse of the area desired to be illuminated. 
     Replacing incandescent bulbs with LEDs would overcome most of the problems of using incandescent bulbs in small enclosures, but LEDs generally produce a small cone of light which typically does not generate adequate illumination to satisfy the majority of lighting requirements in appliances. One of the features of the present invention is to combine one or more LEDs with a specially designed prism to produce a uniform distribution of light of sufficient intensity across a relatively large surface area. 
     Another feature of the present invention is to use two LEDs in combination with a specially designed prism to further increase the area of illumination. This feature is accomplished in a simple but unique manner by adding a mirror image of the original prism. 
     An additional feature of the present invention is to utilize a unique complex lens to focus an LED&#39;s beam of light in a manner that keeps the light focused down the length of the prism to reduce the amount of light that bounces or reflects off of the prism&#39;s two parallel plate surfaces. A further feature is to include in the complex lens a spherical end portion that redirects light onto a curved surface of the prism that reflects the light to a light exiting surface of the prism. 
     According to another feature of the present invention, all of the above mentioned features are incorporated in a plastic prism that can be readily molded to provide an economical alternative to prior known lighting systems, such as those using incandescent light bulbs. The inventive lighting system requires a small amount of power to operate, provides a low operational temperature, is reliable and durable, and vibration resistant. The inventive lighting system can be retrofitted for existing appliance models. 
     According to the principles of the present invention, by using the unique combination of LEDs with the novel prism designs, lighting colors and lighting patterns can be tailored for desired appearance. 
     Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of a prism for a lighting system according to the present invention. 
     FIG. 2 is an illustration of the LED light traveling through the prism depicted in FIG.  1 . 
     FIG. 3 is a perspective view of another embodiment of a prism for a lighting system according to the present invention. 
     FIG. 4 is an illustration of the light from two LEDs traveling through the prism depicted in FIG.  3 . 
     FIG. 5 is a perspective view of the lens and prism for another embodiment of a prism for a lighting system according to the present invention. 
     FIG. 6 is a perspective view of the complex lens incorporated in the prism shown in FIG.  5 . 
     FIG. 7 is an illustration of the light from the LED traveling through the lens and prism of FIG.  5 . 
     FIG. 8 is a perspective view of a modified prism designed to create a particular light pattern. 
     FIG. 9 is an illustration of the particular light pattern created by the prism of FIG. 8 emanating from an appliance aperture. 
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 illustrate a lighting system  10  according to the present invention. The lighting system  10  transmits light from light source  12  through a prism  14 . Prism  14  has a generally triangular like shape having three sides  16 ,  18 , and  20  (see also FIG.  1 ). Prism  14  is preferably formed of a clear glass or plastic material having a high transparency value for transmitting light through the prism between its spaced parallel plate surfaces  22  and  24  (FIG.  1 ). Alternatively, the prism  14  can be made of other suitable materials according to the principles of the present invention. 
     The preferred light source  12  used in lighting system  10  is preferably small in size, reliable and durable, with low energy usage and low heat generation. Conventional LED lamps have been found to be particularly suitable for achieving the desired light source characteristics of the present invention. When designing a lighting system for many appliance applications requiring the illumination of a large expanse, the major shortcoming of using LED lamps is that they project a narrow beam of light. The present invention overcomes this disadvantage by combining the LED with a unique prism design, which will be explained in further detail by reference to the illustration of FIG.  2 . 
     FIG. 2 shows an LED  26  positioned along the light receiving edge  28  of side  16  at a location that causes its cone shaped beam B to travel through the prism until the light strikes the convex edge surface  30  that is formed intermediate of sides  18  and  20 . In accordance with the known principles of light reflection, the radius of curvature of the convex edge surface  30  is preferably selected to have a critical angle less than the angle of incidence of the light beam B. 
     The reflected beam R is directed towards side  20  of the prism  14 , and passes through its light exiting edge surface  32  to provide a substantially uniform light distribution D, which has a substantially greater expanse as compared to the LED&#39;s beam B. This uniform light distribution D has been found to provide sufficient illumination to function as the headlight of a household vacuum cleaner or light up a surface of a wall behind an appliance, such as a stove. 
     When using the lighting system of this invention, it has been found useful to shape the light exiting edge surface  32  to enhance the desired lighting feature. For example in the design of a lighting system for a vacuum cleaner, the light exiting edge surface  32  can be chamfered as depicted in FIG. 1, to cause the light distribution pattern to be downwardly directed in order to illuminate the floor area directly in front of the vacuum cleaner. 
     In the design of a lighting system that needs a uniform light distribution of much greater expanse than that provided by an LED, the radius of curvature of the convex edge surface  30  is important since it is the reflection off this surface that determines the expanse of the uniform light distribution D. It has been found through experimentation that an optimum radius is approximately five inches for certain applications, such as, for example, for use with vacuum cleaners to illuminate the floor directly in front of the vacuum cleaner, or illuminate a portion of a wall behind a stove. 
     With reference to FIG. 4, there is shown another aspect of the present invention. In designing some lighting systems for appliances using the principles of this invention, there is a need to provide a greater expanse of light than can be obtained from the lighting system illustrated in FIGS. 1 and 2. The lighting system  40  depicted in FIG. 4 is capable of providing a substantially uniform light distribution that has practically twice the expanse as that for the lighting system  10  of FIGS. 1 and 2. By comparing the illustrations of FIGS. 2 and 4, it will be seen that prism  42  in FIG. 4 is, in essence, the combination of the prism  14  of FIG. 2 with a mirror image of prism  14 . It will also be appreciated by comparing FIGS. 2 and 4 that the light source  44  for lighting system  40  employs two LEDs  46  and  48 . 
     From the previous description, it will be appreciated that LED  46  is located near a first light receiving edge surface  50  at a position to direct its beam B 1  to the first convex curved edge surface  52 , where the radius of curvature of the convex edge surface  52  is selected to have a critical angle less than the angle of incidence of light beam B 1 . The reflected beam R 1  is directed towards light exiting edge surface  54  and passes through surface  54  to provide uniform light distribution D 1 . Likewise, LED  48  is located near a second light receiving edge surface  56  at a position to direct its beam B 2  to the second convex edge surface  58 , where the radius of curvature of the second convex edge surface has a critical angle less than the angle of incidence of light beam B 2 . The reflected beam R 2  is directed towards light exiting edge surface  60  and passes through surface  60  to provide uniform light distribution D 2 . 
     It will be appreciated from the FIG. 4 illustration that uniform light distribution D 1  and D 2  combine a short distance beyond light exiting edge surfaces  54  and  60  to provide a uniform light distribution that is almost double the expanse of that for the system of FIG.  2 . 
     A perspective view of the light prism  42  of FIG. 4 is depicted in FIG.  3 . As with the prism of FIG. 1, this prism is preferably made of a clear plastic having a high transparency value that can be molded. Other suitable materials can be used. There is also shown in FIG. 3, an LED holder  62  that slides into the V-groove  64  (FIG. 4) of prism  42 . LED holder  62  is configured to hold the LEDs  46  and  48 . As shown, LED holder  62  includes two apertures  66  and  68  for receiving LEDs  46  and  48 , respectively. LEDs  46  and  48  are secured in the apertures  66  and  68 , respectively, in a manner that positions the front of the LEDs against, or at least in close proximity to, the light receiving edge surfaces  50  and  56 , respectively. In the preferred embodiment, the LEDs are positioned in a generally perpendicular orientation with respect to the edge surfaces. The orientation of the LEDs with respect to the edge surfaces may vary depending on the desired results. In any event, by using LED holder  62 , the LEDs can always be placed in the same exact location along the light receiving edge surfaces and can always be held in the same angular orientation (substantially perpendicular to the light receiving edge surfaces). 
     There is illustrated in FIG. 7 yet another aspect of the present invention. In the lighting systems thus described, although substantially uniform light distributions are created, given the general nature of reflective light, it was observed that these lighting systems can generally create alternating lighter and darker bands across the uniform light distribution expanse. In some applications, this visual effect may be less than desired, for example, when the uniform light distribution is intended to shine on a wall surface, such as that found behind a stove. The lighting system  80  depicted in FIG. 7 is capable of greatly diminishing the differences between the lighter and darker bands of the uniform light distribution expanse and thereby present a more pleasing visual effect of the uniform light distribution expanse, when such an effect is desired. 
     The darker bands of the uniform light distribution that can be generated by the lighting systems of FIGS. 2 and 4 are greatly diminished by the addition of a complex lens  82  that is mounted near the light receiving edge surface  84  of prism  86  depicted in FIG.  7 . Prism  86  operates on the same design concepts and principles previously explained with reference to prism  14  (FIGS. 1 and 2) and prism  42  (FIGS.  3  and  4 ). 
     Referring to FIG. 7, in conjunction with FIG. 6, complex lens  82  is shown as having a generally half-cylindrical portion  88  and a generally spherical portion  90  positioned at one end of portion  88 . The diameter of the half-cylindrical portion  88  is preferably the same length as the thickness of the light receiving edge surface  84 . 
     As depicted in FIGS. 6 and 7, as well as in FIG. 5, the complex lens  82  is located on the light receiving edge surface  84  in a contiguous relation in such a manner that the cone-shaped beam C from LED  100 , which is spaced away from lens  82 , will be focused near the portion of the complex lens  82  where the half-cylindrical portion  88  and spherical portion  90  merge together. The spacing and location of LED  100  is set to have its cone-shaped beam C be approximately centered on the boundary of the half-cylindrical portion  88  and spherical portion  90 . 
     The portion of the LED&#39;s cone-shaped beam C striking the spherical portion  90  will bend towards the light beam B′ traveling through prism  86  to the convex edge surface  102 . Without the addition of the spherical portion  90 , the outer portion of the cone-shaped beam C would not find its way to surface  102  to assist in creating the uniform light distribution D′. 
     The major portion of LED&#39;s cone shaped beam C passes through the semi-cylindrical portion  88  which functions to keep the light focused through prism  86  and to greatly reduce the amount of light rays bouncing between the parallel plate surfaces  106  and  108  of prism  86  depicted in FIG.  7 . 
     The net effect of using the complex lens  82  in association with prism  86  is to generate a uniform light distribution D′ which has a greater intensity and, perhaps more importantly, has virtually eliminated the sometimes objectionable alternating lighter and darker bands to create a more pleasing visual lighting effect when the uniform light distribution D′ is shined on a surface, such as a wall surface behind a stove. 
     The complex lens  82  can be made of the same material as the prism  86  and can be conveniently manufactured by simultaneously molding the lens  82  and prism  86  of a clear plastic material, such as an acrylic or styrene material having a high transparency value. 
     Whereas various aspects of the present invention have been illustrated and described in detail, it will be apparent that various changes may be made in the disclosed embodiments without departing from the spirit and scope of the invention. For example, the edge surface of the light exiting surface for prisms  14 ,  42  and  86  can be shaped to produce different uniform light distribution patterns. One such variation has been previously described by chamfering the edge surface to direct the light upwards or downwards (see FIG.  1 ). Another possibility is to shape the light exiting edge surface to have a scalloped shape as depicted on the light exiting edge surface  110  of prism  112  in FIG.  8 . 
     FIG. 9 schematically depicts the visually pleasing palm leaf pattern that results from the scalloped-shaped edge surface  110  of FIG.  8 . The palm leaf light pattern is shown in FIG. 9 as exiting from an elongated surface  116  of an appliance display panel  118  and being directed to appear on a wall surface  120  above the elongated surface  116 . 
     It should be understood that although the invention has been primarily described for use in a vacuum cleaner or stove, the invention is capable of use in any number of other suitable applications, and the use of a vacuum cleaner and a stove in combination with the present invention is merely intended to provide examples of such applications. 
     It should also be understood that the invention is not limited in its application to the details of construction and arrangements of the components set forth herein. The invention is capable of other embodiments and of being practiced or carried out in various ways. Variations and modifications of the foregoing are within the scope of the present invention. It also being understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. 
     Various features of the invention are set forth in the following claims.