Abstract:
Illuminated keypads are disclosed herein. One embodiment includes first and second light guides having a compressible material located therebetween. The material blocks light from traveling between the light guides.

Description:
BACKGROUND 
       [0001]    Many keypads have lights located therein that enable keys to be illuminated. The keys may contain icons or numbers that guide the user to make selections between different keys. Therefore, some keys need to be illuminated while some keys are not illuminated. Problems exist when light from an illuminated key leaks to a key that should be not be illuminated. The key that is not illuminated becomes illuminated by way of the leaked light. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a plan view of an embodiment of a keypad. 
           [0003]      FIG. 2  is a side cutaway view of an embodiment of the keypad of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0004]    A top plan view of an embodiment of a keypad is shown in  FIG. 1 . The keypad  100  contains several portions  104 , wherein each portion may be an area of the keypad  100  that is able to be pressed. The portions  104  may be keys on the keypad, but for illustration purposes, they are referred to as portions  104  of the keypad  100 . For example, the portions  104  may be numbers or icons on the keypad  100  that are depressable. As described in greater detail below, the portions  104  may be individually illuminated. 
         [0005]    Reference is made to a first portion  110  and a second portion  112 . It is noted that the first portion  110  and the second portion  112  may be substantially similar to the other portions  104  of the keypad  100 . The portions  104  may be individually illuminated. For example, the first portion  110  may be illuminated during a period when the second portion  112  is not and should not be illuminated. The illumination of different portions  104  may be used to offer the user of the keypad  100  options to depress illuminated portions of the keypad  100 . In conventional illuminated keypads, light from one portion may leak to another portion that should not be illuminated. This leakage causes the other portion to illuminate when it should not. The keypad  100  described herein overcomes the light leakage problem so that only portions of the keypad  100  that are intended to illuminate actually illuminate. 
         [0006]    A side cutaway view of the keypad  100  of  FIG. 1  is shown in  FIG. 2 . The first portion  110  and the second portion  112  are shown as bracketed regions. The first portion  110  and the second portion  112  may refer to illuminated keys on the keypad  100 . Pressing either the first portion  110  or the second portion  112  will cause a switch to activate as described in greater detail below. 
         [0007]    The keypad  100  has an outer layer  116  that is made from a flexible material. The flexible material means that it can be depressed so as to operate a switch or the like described herein and return to its original configuration without being permanently deformed. The first layer has a first surface  118  and a second surface  120  located opposite of the first surface  118 . The first surface  118  corresponds to the side of the keypad  100  that is viewed and operated by a user. The outer layer  116  may pass light between the first surface  118  and the second surface  120 . Icons or the like may be located in or on the outer layer  116  so as to be illuminated by the light. The light is sometimes referred to as reacting with the icons. 
         [0008]    A plurality of protrusions may extend from the second side  120  of the outer layer  116 . As described in greater detail below, the protrusions may facilitate operation of the switches. In some embodiments, each portion  110 ,  112  of the outer layer  116  has at least one protrusion associated therewith. In the embodiment of  FIG. 2 , the first portion  110  of the outer layer  116  has a first protrusion  124  extending from the second surface  120 . The second portion  112  of the outer layer  116  has a second protrusion  126  extending from the second surface  120 . In some embodiments, the protrusions  124 ,  126  are made of the same material as the outer layer  116 . 
         [0009]    In some embodiments, a light guide holder  130  extends between at least the first portion  110  and the second portion  112 . The light guide holder  130  may be made of transparent material and may serve to hold the light guides in place as described below. 
         [0010]    Each portion of the keypad  100  that is to be illuminated may have a light guide associated with it. In the view of  FIG. 2 , two light guides are shown and are referred to individually as a first light guide  134  and a second light guide  136 . The first light guide  134  has a first light guide first surface  138  and a first light guide second surface  140 , which are opposite one another. Likewise, the second light guide  136  has a second light guide first surface  144  and a second light guide second surface  146 , which are opposite one another. Although the light guides  134 ,  136 , the light guide holder  130 , and the protrusions  124 ,  126  are shown as not contacting each other in  FIG. 2 , they may contact each other. 
         [0011]    The keypad  100  has a substrate  150 , which may be a circuit board or the like. Electrical connections and devices may be located on the substrate  150 . The substrate  150  has a first side  152  and an opposite second side  154 . The first side  152  of the substrate  150  faces the second surfaces  140 ,  146  of the first light guide  134  and the second light guide  136 . Switches  160 ,  162  may be located on the first side  152  of the substrate  150 . A first switch  160  is located in the first portion  110 . A second switch  162  is located in the second portion  112 . The switches  160 ,  162  may be metal type switches or may have compressible domes located thereon as shown in  FIG. 2 . Conductors within the domes may contact electrical contacts on the first side  152  when the domes are depressed. 
         [0012]    A space exists between the first light guide  134  and the second light guide  136 . In order to prevent light from leaking between the first and second light guides  134 ,  136 , a compressible material  170  is located in the space. The compressible material  170  may be located in the light paths extending between the first light guide  134  and the second light guide  136  in order to prevent light from leaking between the light guides  134 ,  136 . The compressible material  170  may extend from the substrate  150  to the light guide holder  130  or to the first surfaces  138 ,  144  of the light guides  134 ,  136 . 
         [0013]    In some embodiments, the compressible material  170  contains urethane. In still other embodiments, the compressible material  170  is a closed cell material or a closed cell foam material. In some embodiments, the compressible material is black so as to prevent light from reflecting off the compressible material  170 . A compressible material means that it is able to be compressed as used in the keypad  100  and substantially return to its original shape with insignificant permanent deformation. 
         [0014]    Having described the components of the illuminated keypad  100 , its operation will now be described. A processor or other device (not shown) determines which portions  104  of the keypad  100  are to be illuminated. The processor or other device may then cause a light source (not shown) to illuminate a light guide  134 ,  136  that correspond to the portions  104  of the keypad  100  that are to be illuminated. In this example, the first portion  110  of the keypad corresponding to the first light guide  134  is to be illuminated and the second portion  112  of the keypad  100  corresponding to the second light guide  136  is not to be illuminated. 
         [0015]    Light from the illuminated first light guide  134  passes through the light guide holder  130  and to the second side  120  of the outer layer  116 . As described above, icons may be present in the outer layer  116  (or in other sections of the keypad  100 ) so that the light reacts with the icons as it passes to the first side  118  of the outer layer  116 . The result is that the icon is illuminated on the first portion  110  of the keypad  100 . In other embodiments, the icon may be present in the light guide holder  130  or in the first light guide  134 . In other embodiments, there are not icons. 
         [0016]    The compressible material  170  prevents light emitted from the first light guide  134  from entering the second light guide  136 . Therefore, the second portion  112  of the keypad  100  will remain without illumination. 
         [0017]    A user may depress the first portion  110  of the keypad  100 . This depressing causes the first protrusion  124  to apply pressure to the components of the keypad  100  and deform the switch  160 . Thus, the switch  160  is toggled. During the application of pressure to the first portion  110 , some deformation may occur in the region of the compressible material  170 . Because the material is compressible, it maintains its light blocking characteristics during compression. The result is that no light leaks to the second light guide  136  during the period when the first portion  110  is being depressed. When pressure is removed from the first portion  110 , the first switch  160  and the other components of the keypad  100  return to their original shape. The same applies to the compressible material  170 . More specifically, the compressible material  170  returns to its original configuration, which continues to prevent light leakage to the second light guide  136  even after compression of the first portion  110 .