Abstract:
An LED light bulb includes a base and a hollow shell. The base has a closed end, an open end and a sleeve between the two ends. The shell is connected to the open end of the base. The LED light bulb includes at least two LEDs substantially linearly arranged within the shell, and supported by a self-supporting wire connecting one terminal of an LED to the next LED in each strand.

Description:
CROSS REFERENCE 
     This application is based on Republic of China (Taiwan) Application No. 0096206431 filed Apr. 23, 2007, the entirety of which is hereby incorporated by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a light bulb. In particular, the present invention relates to a light emitting diode (LED) light bulb that comprises one or more light emitting diodes (LEDs) in one or more substantially linear arrangements. 
     BACKGROUND OF THE INVENTION 
     Most existing light bulbs are incandescent light bulbs or fluorescent light bulbs. An incandescent light bulb typically comprises a base, a glass shell, a thin filament which is normally a thin tungsten filament within the shell, and an inert gas within the shell. When an electric current passes through the tungsten filament and heats it up to an extremely high temperature (2000° C. to 3000° C. depending on the filament type, shape, size, and amount of current passed through), heat radiation occurs and visible light is produced. However, the incandescing process is considered highly inefficient, as over 98% of its energy is emitted as invisible infrared light (or heat) and the luminance cannot further improve. In addition, the typical lifespan of an incandescent bulb is limited to about 1,000 hours. 
     By comparison, a fluorescent light bulb is filled with gas containing low-pressure mercury vapor and an inert gas such as argon or xenon. The inner surface of the bulb is coated with a fluorescent (and often slightly phosphorescent) coating made of various blends of metallic and rare-earth phosphor salts. When electricity passes through mercury vapour, the mercury vapour produces ultraviolet light. The ultraviolet light is then absorbed by the phosphorus coating inside the bulb, causing it to glow, or to fluoresce. While the heat generated by fluorescent light is much less than its incandescent counterpart, efficiencies are still lost in generating the ultraviolet light and converting this light into visible light. In addition, mercury is considered detrimental to the health of people and animals. Therefore, if the fluorescent bulb breaks, exposure to the substance can be hazardous. Fluorescent bulbs are typically more expensive than incandescent bulbs, but they have life spans of about 10,000 hours. 
     A light emitting diode light bulb is another type of light bulb. The LED bulb typically has high durability with no need to worry about the filament breaking as occurs with respect to incandescent bulbs or the noted hazards as can occur with respect to fluorescent bulbs. LED light bulbs have a long life span of approximately 50,000 to 100,000 hours. The LED bulb generates little heat and has little parasitic energy loss, thereby reducing the overall electricity used. This, in turn, increases the possibilities of reducing electricity bills. Since the LED light bulb has so many advantages over the incandescent bulb and the fluorescent bulb, it is considered to be a cost-effective yet high quality replacement for incandescent and fluorescent light bulbs. 
     There are already some LED bulbs in the market. These LED bulbs either contain one LED in the bulb or at least two LEDs horizontally fixed directly on one printed circuit board (PCB) in the bulb. For the bulb containing only one LED, the light is generally not bright enough. The luminance is hard to improve for a single bulb containing a single LED. For bulbs having at least two LEDs horizontally fixed on one PCB, the LEDs are in the same horizontal level and the distances that can be brightened by those LEDs are similar because of their attachment to the PCB. When the bulb shell increases in size, the LEDs will all have a longer distance to the bulb shell. As the distance from the LED to the shell increases, the brightness becomes weaker and dimmer. Light is governed by an increase-square law of physics namely that the intensity/strength of the light from a source is inversely proportional to the square of the distance from the source. Therefore, the use of LED bulbs in the prior art is limited to applications which do not have a high luminance requirement. In order to broaden the use of LED bulbs because of their so many advantages, limited luminance needs improvement. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided an LED light bulb. The LED light bulb has a hollow base, a hollow shell and at least two LEDs. The base has a closed end, an open end and a sleeve therebetween. The hollow shell is connected to the open end of the base. The LEDs are vertically arranged within the shell, for connecting to a DC power source. 
     The sleeve may serve as an electrode; the closed end has a contact point serving as another electrode; both the two electrodes are connected to the input of a power converter, which converts an AC power to the DC power to be supplied to the LEDs. The bulb further has an insulating part separating and insulating the two electrodes. The power converter can be arranged inside the hollow base or located outside of the bulb. 
     The shell may be made of transparent plastics, transparent glass or similar materials. The sleeve of the base may include external threading. 
     The LED bulb may further include a transparent support for maintaining the LEDs in a vertically arranged position, and the transparent support may be a hollow plastic stem, made of transparent plastics, transparent glass or similar materials. 
     The power converter may include a filter circuit, a bridge rectifier circuit, and a resistor. The bridge rectifier circuit is connected to the electrodes via the filter circuit, and the output of the bridge rectifier circuit is connected to LEDs via the resistor. The LEDs can be connected in parallel or in series. The LEDs can be vertically stacked within the shell 
     The LED bulb according to the present invention, due to the vertical stacked arrangement, does not increase the distance from the LEDs to the top of the bulb shell when the bulb shell is bigger and higher, so luminance or brightness can be guaranteed by varying the number of LEDs in a bulb. In addition, the LED bulb according to the present invention consumes less energy than traditional incandescent or fluorescent bulbs and has a longer life (about 50,000 to 100,000 hours). It is also compatible with the bases of the existing bulb. Therefore, replacing a traditional bulb with one according the present invention is convenient and practical. 
     In accordance with an aspect of the present invention, there is provided a bulb, comprising:
         a base, said base further comprising a closed end, an open end and a sleeve therebetween, wherein said sleeve serves as an electrode and said closed end comprises a contact point serving as another electrode;   a hollow shell connected to the open end of the base; and   a strand of at least two LEDs joined together and substantially linearly arranged within the shell   wherein said bulb is adapted for connection to a DC power source.       

     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, further comprising a support for maintaining at least two LEDs in a substantially linear arranged position. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the support comprises a hollow plastic stem adapted to contain the at least two LEDs. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the substantially linear LEDs are oriented in a substantially vertical direction in relation to said bulb. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the base is hollow, and, within the hollow base, the bulb further comprises a power converter for converting AC power to DC power to be supplied to the LEDs. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein both the two electrodes are connected to the input of the power converter; and the bulb further comprises an insulating part separating and insulating the two electrodes. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the power converter comprises a filter circuit, a bridge rectifier circuit, and a resistor; the bridge rectifier circuit is connected to the electrodes via the filter circuit, and the output of the bridge rectifier circuit is connected to LEDs via the resistor. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the sleeve of the base comprises external threading. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the shell is made of translucent or transparent plastic. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the shell is made of translucent or transparent glass. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the LEDs are connected in parallel. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the LEDs are connected in series. 
     In accordance with another aspect of the present invention, there is provided an LED bulb, the bulb comprising:
         a base, said base further comprising a closed end, an open end and a sleeve therebetween, wherein said sleeve serves as an electrode and said closed end comprises a contact point serving as another electrode;   a hollow shell connected to the open end of the base; and   at least two substantially linear strands of LEDs wherein each substantially linear strand of LEDs further comprises at least two LEDs   wherein said bulb is adapted for connection to a DC power source.       

     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein said at least two substantially linear strands are joined together at one or more points along the length of said substantially linear strands. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein said substantially linear strands are joined to form an array whereby each strand points in a different direction within said compartment. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein said substantially linear strands are each oriented in a substantially vertical orientation within said compartment. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the LEDs are connected in parallel within each strand. 
     In accordance with another aspect of the present invention, there is provided the bulb of the present invention, wherein the LEDs are connected in series within each strand. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention will be better understood by the detailed description thereof, with reference to the accompanying drawings, wherein like reference numerals refer to the like elements throughout, in which: 
         FIG. 1  is a perspective view of an LED bulb according to the prior art; 
         FIG. 2  is a perspective view of another LED bulb according to the prior art; 
         FIG. 2A  is a perspective view of a portion of the prior art bulb illustrated in  FIG. 2  and accordingly is prior art; 
         FIG. 3  is a perspective view of an LED bulb in accordance with one embodiment of the present invention; 
         FIG. 3A  is a perspective view of an LED bulb in accordance with another embodiment of the present invention; 
         FIG. 4  is an electrical circuit of one part of the bulb of  FIG. 3 ; 
         FIG. 5A  is a perspective view of an LED bulb in accordance with another embodiment of the present invention; 
         FIG. 5B  is a perspective view of an LED bulb in accordance with another embodiment of the present invention; 
         FIG. 6  is a side view of an LED bulb in accordance with a decorative bulb embodiment of the present invention illustrating the typical bulb surface of a Christmas bulb; and 
         FIG. 7  is a section of the bulb illustrated in  FIG. 6  illustrating the interior components of the bulb. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates an LED bulb according to the prior art. The LED bulb, generally shown as  10 , comprises a hollow base  20  and a hollow shell or sometimes referred to as an envelope  30 . For the instant application, the entire article illustrated, for example in  FIG. 1 , is called a bulb. The LED inside the bulb, for example LED  110 , is called an LED. The base  20  has an open end  50 , a closed end  60  and a sleeve  70  between the ends  50  and  60 . The sleeve  70  has external threading  80  so as to match internal threading in a bulb holder (not shown) for installment. The sleeve  70  serves as an electrode. In the central part of the closed end  60  is located a contact point or portion, serving as another electrode  90 , and an insulating portion ( 8171  in  FIG. 7 ) separates and insulates the two parts  70  and  90 . When the LED bulb  10  is installed in a bulb holder, such as in a desk lamp, parts  70  and  90 , acting as electrodes, are connected to the electrical contact points in the bulb holder. The electrical contact points in the bulb holder are typically further connected to a plug or switch in order to provide electricity to the bulb thereby causing the LED&#39;s to light up. 
     The follow back shell or envelope  30  is connected to open end  50  of base  20  and thus forms an enclosed compartment  100  together with the closed end  60  of the base  20 . Within the compartment  100 , the bulb  10  comprises at least one an LED  110 . Corresponding to the sleeve portion  70  in the compartment  100  is located a power converter  120 , which converts AC to DC and supplies energy to at least one LED contained within the bulb  10 . Alternatively, the power converter can be located outside of the LED bulb and supply DC power directly to multiple LED bulbs each constructed similarly to the prior art bulb  10  illustrated in  FIG. 1 . 
       FIG. 2  illustrates another prior art LED bulb,  210 . It is similar to the LED bulb in  FIG. 1 , and the only difference is that it comprises more than one LED,  2110 , more specifically seven LEDs, within the shell  230 . The seven LEDs in the prior art bulb  210  of  FIG. 2  are horizontally fixed on a printed circuit board (PCB)  2111 , with presumably a goal to enhance the luminance of the bulb. However, the distance that can be brightened is not much further than a bulb with a single LED, because all of the LEDs are grouped together in a common place. 
     As light waves move away from the light source, the light waves spread out over a distance and quickly diminish in intensity. It is known that there is a light intensity decay over distance with light intensity decreasing quickly as the distance from the light source increases. The intensity of light is the power per unit of area. Area increases as the square of the distance therefore light decreases as the inverse square of the distance. Light intensity follows an inverse-square law. Therefore if all the LEDs are in the same or substantially the same horizontal plane, the brightness or light intensity of the bulb may not increase significantly between the prior art bulb in  FIG. 1  and the prior art bulb illustrated in  FIGS. 2 and 2A  despite the additional LEDs present. 
     Furthermore, with more LEDs on a PCB, the bulb shell must be big enough to accommodate them. Since a bulb (for example bulb  10  or bulb  210 ) typically has a smaller diameter than its height (as illustrated), then a horizontal distribution of LEDs on a PCB will be limited by the size of the bulb shell the number of LEDs present in. 
       FIG. 3  is an illustration of an LED bulb in accordance with one embodiment of the present invention. The LED bulb  310  comprises a hollow base  320  with an open end  350 , a closed end  360  and a sleeve  370  therebetween. A hollow shell  330  is connected to the open end  350  of the base  320 , and a compartment  3100  formed by the shell  330  and the base  320 . The sleeve  370  has external threading  380  to be installed in an internally threaded bulb holder. The sleeve  370  serves as one electrode. The closed end  360  has a contact portion or point  390  serving as another electrode. An insulating part ( 8171  in  FIG. 7 ), made of rubber or other insulating material, separates and insulates the two parts  370  and  390 . In the sleeve portion  370  of the compartment  3100  is located a power converter  3120  for converting AC to DC and supplying DC power to the LEDs. 
     Unlike the prior art bulb in  FIG. 1 , the particular example illustrated by bulb  310  comprises three LEDs  3110  contained within the compartment  3100  so as to increase the luminance created by the bulb. The LEDs  3110  are stacked such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand and connected in series with each other and also connected in series with the power converter. Although  FIG. 3  illustrates three LEDs in the bulb, the number of LEDs contained in the bulb can vary from two to any number that can be arrayed within compartment  3100  depending on the dimensions of the bulb shell  330 . Preferred embodiments comprise at least 2 LEDs. 
     The LED bulb  310  may further comprise a support. A support comprises any structure which abuts or surrounds the at least two LEDs in linear arrangement to support a vertical orientation or a particular direction. An example of a suitable support is illustrated in  FIG. 3  illustrating a hollow transparent stem  3130  to support and maintain the LEDs  3110  in a substantially vertical alignment or linear alignment. The support can be made of translucent or transparent materials such as plastics or glass. It can be cloudy or clear or colored or colorless. The bulb shell can also be made of translucent or transparent glass or plastics and it can be cloudy or clear or clear or colored or colorless. 
     Referring to  FIG. 4 , the power converter  3120  comprises a filter circuit  4210 , and a bridge rectifier circuit  4220 , and a resistor  4230 . The filter circuit further comprises a resistor  4212  and a capacitor  4214 , connected in parallel. The bridge rectifier circuit  4220  is connected to the electrodes (power supply) via the filter circuit  4210 , and the output of the bridge rectifier circuit  4220  is connected to LEDs  3110  via the resistor  4230 . Thus the alternative current flowing to the LED bulb from the power supply connected to the plug of the bulb holder can be converted to direct current needed by the LEDs  3110 , so as to cause the LEDs to emit light. 
     The power adaptor can also be located outside of the LED bulb and can be adapted to supply DC power directly to one or multiple LED bulbs. Furthermore, those skilled in the art will understand that other kinds of power converters and/or filter circuits can also be used. The base can be of bi-pin type instead of the screw base as illustrated herein, or any other type of lamp base with inner space no less than E-12 type lamp base. The vertical arrangement of the LEDs is generally linear and can extend substantially vertical or can be pointed in a particular direction. In a substantially vertical embodiment, the arrangement need not be precisely vertical, indeed the LEDs may be offset from each other by a few degrees, or the whole stacked arrangement of LEDs may be offset from the vertical position by a few degrees. In either case, a person skilled in the art will understand that such variances are acceptable in the operation of the LED bulb of the present invention. 
       FIG. 3A  is an illustration of an LED bulb in accordance with another embodiment of the present invention. The LED bulb  710  comprises a hollow base  720  with an open end  750 , a closed end  760  and a sleeve  770  therebetween, a hollow shell  730  connected to the open end  750  of the base  720 , and a compartment  7100  formed by the shell  730  and the base  720 . The sleeve  770  has external threading  780  to be installed in an internally threaded bulb holder. The sleeve  770  serves as one electrode. The closed end  760  has a contact portion or point  790  serving as another electrode. An insulating part ( 8171  in  FIG. 7 ), made of rubber or other insulating material, separates and insulates the two parts  770  and  790 . In the sleeve portion  770  of the compartment  7100  is located a power converter  7120  for converting AC to DC and supplying DC power to the LEDs. 
     The bulb  710  in  FIG. 3A  further comprises more than one substantially linear strand of LEDS. In the specific embodiment illustrated in  FIG. 3A  three strands are illustrated and each is referred to by reference numeral  7140 . Each strand  7140  comprises in this specific embodiment, three LEDs  7110 . The number of LEDS per strand may vary and the number of strands may vary all contained within compartment  7100  so as to increase the luminance created by the bulb. Each LED comprises a base  7142  having electrical terminals  7143  and an envelope  7141  extending from the base to the envelope top end distal from the base. The LEDs  7110  in each strand  7140  are joined in a linear orientation. They are connected in series with each other and also connected in series with the power converter. In the bulb  710  in  FIG. 3A , the strands  7140  are each oriented in a substantially linear and vertical orientation within the compartment  7100  such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand. Though  FIG. 3A  illustrates three strands each having three LEDs in the bulb, the number of strands and LEDs contained in the bulb can vary from two to any number that can be contained within compartment  7100  depending on the dimensions of the bulb shell. 
       FIG. 5A  is an illustration of an LED bulb in accordance with another embodiment of the present invention. The LED bulb  510  comprises a hollow base  520  with an open end  550 , a closed end  560  and a sleeve  570  therebetween, a hollow shell  530  connected to the open end  550  of the base  520 , and a compartment  5100  formed by the shell  530  and the base  520 . The sleeve  570  has external threading  580  to be installed in an internally threaded bulb holder. The sleeve  570  serves as one electrode. The closed end  560  has a contact portion or point  590  serving as another electrode. An insulating part ( 8171  in  FIG. 7 ), made of rubber or other insulating material, separates and insulates the two parts  570  and  590 . In the sleeve portion  570  of the compartment  5100  is located a power converter  5120  for converting AC to DC and supplying DC power to the LEDs. 
     The specific embodiment illustrating bulb  510   FIG. 5A  illustrates three substantially linear strands  5140 , each strand comprising three LEDs  5110  contained within the compartment  5100  thereby increasing and enhancing the luminance created by the bulb. In contrast to the strands  7140  in  FIG. 3A , the strands  5140  in  FIG. 5A  are joined to form an array whereby each strand  5140  points in a different direction within compartment  5100 . The shell  530  in  FIG. 5A  is larger than the shell  730  in  FIG. 3A  in order to accommodate the arrangement of the strands  5140 . The LEDs  5110  are stacked such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand and connected in series with each other and also connected in series with the power converter. A strand  5140  may be joined together with the other strands  5140  at one or more points along the length of the strand  5140 . Though  FIG. 5A  illustrates three strands each having three LEDs in the bulb, the number of strands and LEDs contained in the bulb can vary from one to any number that can be arrayed within compartment  5100 . There can be a number of strands each having at least two LEDs. The strands need not have the same number of LEDs but on the other hand they may have the same number of LEDs. 
       FIG. 5B  is an illustration of an LED bulb in accordance with another embodiment of the present invention. The LED bulb  610  comprises a hollow base  620  with an open end  650 , a closed end  660  and a sleeve  670  therebetween, a hollow shell  630  connected to the open end  650  of the base  620 , and a compartment  6100  formed by the shell  630  and the base  620 . The sleeve  670  has external threading  680  to be installed in an internally threaded bulb holder. The sleeve  670  serves as one electrode. The closed end  660  has a contact portion or point  690  serving as another electrode. An insulating part ( 8171  in  FIG. 7 ), made of rubber or other insulating material, separates and insulates the two parts  670  and  690 . In the sleeve portion  670  of the compartment  6100  is located a power converter  6120  for converting AC to DC and supplying DC power to the LEDs. 
     The bulb  610  further comprises three substantially linear strands  6140 , each strand comprising three LEDs  6110  contained within the compartment  6100  so as to increase the luminance created by the bulb. Unlike the strands  7140  in  FIG. 3A , the strands  6140  in  FIG. 5B  are joined to form an array whereby each strand  6140  points in a different direction within compartment  6100 . The shell  630  in  FIG. 5B  is larger than the shell  730  in  FIG. 3A  in order to accommodate the arrangement of the strands  6140 . The LEDs  6110  are stacked such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand and each strand  6140  is connected to the other strands  6140  such that the connection between strands  6140  occurs between LEDs  6110  closest in proximity to the sleeve portion  670 . Though  FIG. 5B  illustrates three strands each having three LEDs in the bulb, the number of strands and LEDs contained in the bulb can vary from one to any number that can be arrayed within compartment  6100 . 
       FIGS. 6 and 7  are illustrations of an LED bulb in accordance with another embodiment of the present invention. The LED bulb  810  comprises a hollow base  820  with an open end  850 , a closed end  860  and a sleeve  870  therebetween, a hollow shell  830  connected to the open end  850  of the base  820 , and a compartment  8100  formed by the shell  830  and the base  820 . The shell  830  has a thickness  8170  and an outer surface  8180 . The sleeve  870  has external threading  880  to be installed in an internally threaded bulb holder. The sleeve  870  serves as one electrode. The closed end  860  has a contact portion or point  890  serving as another electrode. An insulating part  8171 , made of rubber or other insulating material, separates and insulates the two parts  870  and  890 . In the sleeve portion  870  of the compartment  8100  is located a power converter  8120  for converting AC to DC and supplying DC power to the LEDs. The power converter is connected to point  890  by wire  8165  and to sleeve  870  by wire  8166 . 
     The particular example illustrated by bulb  810  in  FIGS. 6 and 7  comprises two LEDs  8110  contained within the compartment  8100  so as to increase the luminance created by the bulb. The LEDs  8110  are stacked such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand and connected in series with each other by wires  8160  and also connected in series with the power converter. The bulb in  FIGS. 6 and 7  has a traditionally narrowed tip end  8150  consistent with decorative bulbs of the holiday seasons. Although  FIGS. 6 and 7  illustrate two LEDs in the bulb, the number of LEDs contained in the bulb can vary from two to any number that can be linearly contained within compartment  8100  and in this embodiment the strand of two LEDs is arranged in a substantially vertically orientation. 
     A globe bulb may be used, for example in Halloween lights may which may be shaped like a pumpkin. Other arrangements of single substantially linear strands and multiple substantially linear strands would be known to a person skilled in the art and would be suitable for bulbs of varying sizes and shapes. 
     Though in the embodiment illustrated herein the LEDs are connected in series, those skilled in the art will understand that the LEDs can also be connected in parallel. However, even though the LED bulb can contain a large number of LEDs because the voltage drop across each LED is small, due to the difficulties of constructing a circuit with LEDs in parallel, the number of LEDs that can be connected in parallel is limited by the amount of the voltage drop. 
     By stacking LEDs in substantially linear strands arranged such that for all but the last LED in each strand, the envelope top end of any given LED of a strand substantially faces the base of an adjacent LED in the strand, an LED bulb of the present invention is able to distribute light evenly within the entirety of the bulb compared to the prior art including where the bulb is pointed such as in a Christmas tree bulb or the bulbs of outdoor lights which are strung at Christmas. This is possible because in accordance with an advantage of the present invention the distance from any location in a bulb to the closest LED to that location varies less in the bulb of the present invention than in a bulb of the prior art. For example, the distance between the top of the bulb shell and an LED fixed to the PCB in the prior art shown in  FIG. 2  is much greater than the distance from the top of the bulb shell to the top-most LED in the stacked arrangement shown in  FIG. 3 . In this example, light from the top LED in the stack does not have to travel as far in the present invention to reach the top of the bulb shell, and therefore allows that location to appear brighter than it does in the prior art. In practice, this means that an LED bulb of the present invention using the same number of LEDs as the prior art bulb from  FIG. 2  will appear brighter, especially when viewed from the side or from a long distance away. 
     The LED bulb of the present invention has other advantages over the prior art. It is possible to create larger bulbs while maintaining even brightness distribution by using multiple linear stacks oriented in substantially vertical or oriented diagonally, of LEDs arranged side-by-side. In this way, light can be distributed more evenly throughout the bulb, regardless of the size of the bulb, simply by adding more stacks of LEDs beside one another in the bulb. 
     It was also determined that the cost of manufacturing an LED bulb of the present invention that uses 2 to 4 LEDs is lower than the cost of manufacturing an LED bulb of the prior art using the same number of LEDs. 
     Note that it is possible to create an LED bulb of the prior art using multiple PCBs, each having multiple LEDs, where each PCB is positioned parallel to the other PCBs, both above and below the single PCB shown in  FIG. 2 . Depending on the arrangements of the LEDs on the PCBs, it is possible to increase the brightness of the LED bulb of the prior art in this way. However, in order to achieve brightness that is similar to the brightness of the LED bulb of the present invention, such a stacked-PCB design would require more LEDs and have increased manufacturing cost compared to the LED bulb of the present invention. 
     A test was carried out on an LED bulb of the present invention where the LEDs in the bulb were connected in a series arrangement as shown in  FIG. 4  to determine how many LEDs could be used in that arrangement. For the test, an input voltage of 110V was used. In order to achieve the desired current of 10 mA to 13 mA for proper operation of the LEDs, an input resistor with a resistance of 560 Ohms was used causing the voltage to drop to 90V. Since the maximum voltage drop across each single LED was 3.4V, the maximum number of LEDs that could be used in the circuit was determined by the calculation 90V divided by 3.4V per LED, or 26.47 LEDs. Therefore the maximum number of LEDs arranged in series was determined to be 26. However, during testing, it was found that the input resistor will become over-heated when there are more than 23 LEDs connected in series. For safety concerns, the maximum number of LEDs that were connected in series in this test was 20. It should be noted that the number of LEDs vertically positioned in a bulb is also limited by the size of the bulb shell. 
     In another test, it was shown that the LED bulb according to the embodiments of the present invention can provide energy savings of up to 90% compared with a traditional incandescent light bulb. In this test, a LED bulb of the present invention having 3 LEDs was compared with 120V 3 W C7 and C9 type incandescent lamp bulbs, which are known to the applicant to be amongst the lowest power consuming incandescent light bulbs in the North American market. The test results showed that the LED bulb consumed power in the range of 0.3 W to 0.35 W, which is a savings of nearly 90% compared to the 3 W consumed by the C7 and C9 incandescent bulbs. 
     The LED bulb can be used in various applications, such as household, work plant, show window, store, street display, exterior decorations. The LED bulbs of the present invention are applicable in many setting requiring light and can provide enhanced luminescence and brightness over prior art LED bulbs at a lower cost of manufacturing as described herein. The luminance of the LED bulb can be adjusted by including various LEDs in the bulb. 
     While this invention has been illustrated and described in connection with only certain embodiments thereof, various changes, modifications and amendments can occur to those skilled in the art without departing from the spirit and the scope of the invention as defined in the appended claims.