Abstract:
A flame simulating device includes a substantially translucent shell having a hollow interior, a plurality of colored light sources, positioned within the hollow interior of said shell and a light source driving device for selectively activating each of said plurality of light sources. Each of the light sources are alternately and individually activated to have active periods and such that the surface of said shell is illuminated to produce an animated flame effect. In one example implementation, yellow, orange and red LEDs are positioned at varying heights within the flame-shaped shell and activated on and off in a sequence that follows a set of color transition rules in order to provide a close simulation of the flickering of a flame. During their active periods, LEDs are blinked on and off to conserve power.

Description:
[0001]    This application claims the benefit under 35 U.S.C.  119 ( e ) of U.S. Provisional Application No. 60/468,185, filed May 6, 2003. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to display devices and particularly to flame simulating devices.  
         BACKGROUND OF THE INVENTION  
         [0003]    Conventional flame sources require lighting with matches or the like, and when lit, represent a serious fire hazard, especially when unattended as is the case in commercial settings (e.g. restaurants, stores etc.) Furthermore, real flame sources (e.g. candles) present other personal injury and collateral damage challenges (e.g. dripping wax on people and/or upholstery etc.) Finally, real flame sources are easily extinguished (e.g. by air currents etc.) and accordingly cannot be easily setup and maintained without constant monitoring.  
           [0004]    There are a variety of flame imitation novelty products that utilize various methods to simulate a real flame for display purposes such as those disclosed in U.S. Pat. Nos. 6,454,425 and 4,550,363. Specifically, U.S. Pat. No. 6,454,425 discloses a candle flame simulating device that includes a blowing device for generating an air and for directing the air toward a flame-like flexible member, in order to blow and to oscillate or to vibrate the flame-like flexible member and to simulate a candle. U.S. Pat. No. 4,550,363 discloses an electric-light bulb fitted with a light permeable and light-scatting lamp casing. However, such attempts result in flame displays that are relatively poor imitations of a real flame. In addition, such devices require substantial energy and require frequent battery replacement.  
         SUMMARY OF THE INVENTION  
         [0005]    The invention provides in one aspect, a flame simulating device comprising:  
           [0006]    (a) a substantially translucent shell having a hollow interior and a directional axis;  
           [0007]    (b) a plurality of colored light sources, adapted to be positioned within the hollow interior of said shell;  
           [0008]    (c) a light source driving device for selectively activating each of said plurality of light sources;  
           [0009]    (d) each of said light sources being selectively activated such that the surface of said shell is illuminated and produces an animated flame effect.  
           [0010]    Further aspects and advantages of the invention will appear from the following description taken together with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    In the accompanying drawings:  
         [0012]    [0012]FIG. 1 is a cross-sectional view of the flame simulating device of the present invention;  
         [0013]    [0013]FIG. 2 is a schematic drawing illustrating the duty cycles of the yellow, orange and red light sources of FIG. 1;  
         [0014]    [0014]FIG. 3 is a schematic drawing of an example implementation of LED lighting assembly that drives the LED array of FIG. 1;  
         [0015]    [0015]FIG. 4 is a block diagram of an example implementation of control circuit of FIG. 3;  
         [0016]    [0016]FIG. 5 is a flow-chart illustrating the main steps of the MAIN OPERATION routine utilized by the microcontroller to control the output of the LED array of FIG. 4; and  
         [0017]    [0017]FIG. 6 is a schematic drawing of an example implementation of an audio deactivator device that shuts off the light source driving circuit of FIG. 1. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Referring to FIG. 1, illustrated therein is a flame simulating device  10  made in accordance with a preferred embodiment of the present invention. Flame simulating device  10  consists of an LED lighting assembly  30  that is incased in a substantially translucent shell  40 . LED assembly  30  consists of an LED array  12 , a power source  16 , light source driving circuit  18 . Light source driving circuit  18  is designed to allow a maximum of one LED from LED array  12  to be on at any particular time. Also as shown, flame simulating device  10  is also adapted to fit within the top of a base  41 . The combination of LED assembly  30  and shell  40  of flame simulating device  10  provides realistic flame lighting effects as will be described.  
         [0019]    Shell  40  is substantially translucent in order to allow a substantial amount of light from LED array  12  to penetrate the surface of shell  40  such that visible lighting effects are provided on the surface of shell  40 . Shell  40  is preferably flame-shaped (FIG. 1) but it should be understood that shell  40  could be any volumetric container that has enough space within to house LED lighting assembly  30 . For example, it is contemplated that shell  40  could have the shape of a pen-shaped tubular body, a spherical ball, a rectangular box, a multisided box, etc. (e.g. adapted to be coupled to a keychain etc.) for application to various novelty items. Other example include yo-yo&#39;s, batons, computer mice, lamps, bulbs, night lights, wearable items (e.g. necklaces, broaches, pins, hair accessories, lariats), floral “picks” (longitudinal bodies for use with floral bouquets), picture frames, gearshift knobs and tire lights to only name a few. Finally, while shell  40  is preferably manufactured from plastic, it should be understood that it could be manufactured from other materials.  
         [0020]    As illustrated in FIG. 1, LED array  12  comprises a plurality of LEDs. In order to provide realistic flame effects, it has been determined that it is optimal to use at least one yellow, at least one orange, and at least one red LED within LED array  12 . However, it should be understood that it is also possible to use various color types and combination of LEDs within LED array  12  (e.g. the additional use of white LEDs to add brightness to the array, the additional use of blue LEDs to simulate propane gas flame etc.)  
         [0021]    For illustrative purposes, the present invention will be described in respect of a LED array  12  that comprises one yellow LED  12   a , one orange LED  12   b , and one red LED  12   c  as shown in FIG. 1. Also for discussion purposes, it should be noted that yellow, orange and red LEDs  12   a ,  12   b  and  12   c  are arranged at different heights as measured along the longitudinal axis of flame-shaped shell  40  (FIG. 1). This variation in directional axis (i.e. the longitudinal axis of this example embodiment) further enhances the “flame-like” effect produced by flame simulation device  10  since the different colored LEDs are positioned to represent different parts of a flame.  
         [0022]    As conventionally known, LEDs are semiconductor devices that emit a visible light when current biased in the forward direction. Unlike standard bulb type lamps, LEDs are immune to failure conditions such as filament breakage due to sudden shocks or bumps and are well suited for use in articles that may experience sudden impacts from being bounced or shaken such as flame simulating device  10 . In addition, LEDs are highly energy efficient as they only require a small amount of electricity to generate a relatively strong light. For example, a typical incandescent lamp operates on 5 volts and uses a current of 115 milliamps while a LED can operate on 3 volts and draw current on the order of 5 to 20 milliamps.  
         [0023]    Accordingly, LEDs are a particularly desirable lighting source in applications involving small and lightweight devices where the desired size and weight limits the strength of power sources available thereby making energy efficiency important. The LEDs of LED array  12  are preferably 5 mm high intensity wide dispersion color LEDs. However, it should be understood that many other kinds of LEDs could be utilized depending on the particular visual effect desired or the device production economy required, such as 3 mm on surface mounted lens less LEDs. Since the rated lifetime of these LEDs is approximately 15 years, LED array  12  provides flame simulating device  10  with an energy efficient, long lasting, light weight and durable light source.  
         [0024]    Power source  16  is preferably four conventional penlight “AAA” batteries, consisting of two sets in parallel to insure relatively long life. Alternatively, a 6 volt DC adaptor can be used to power a “screw in” bulb version. Power wires  17  are used to connect LED array  12  to power source  16 . It has been determined that four penlight “AAA” batteries will run flame simulating device  10  continually for over several months. This long lifetime is due to the fact that light source driving circuit  18  is designed to only allow maximum one LED from LED array  12  to be on at any particular time as will be further discussed. This results in substantial power savings since power source  16  is only required to power at a maximum one LED at any particular time. The power requirements of flame simulating device  10  is substantially less than those of devices that use multiple LEDs where one or more LEDs must be powered at any particular time (i.e. simultaneously).  
         [0025]    Now referring to FIGS. 1 and 2, FIG. 2 illustrates an example activation protocol for the three example LEDs within LED array  12  that have been discussed. It should be understood that many different types of activation profiles and relative positioning of activation characteristics for the various LEDs could be used for the LEDs within LED array  12  of flame simulating device  10 . As discussed, generally speaking yellow, orange and red LEDs  12   a ,  12   b  and  12   c  are sequentially activated and deactivated in a manner that simulates the color flickering of a real flame. Specifically, yellow, orange and red LEDs  12   a ,  12   b  and  12   c  are sequentially activated according to a set of color transition rules as will be discussed in more detail below.  
         [0026]    The activation characteristics of LEDs within LED array  12  shown in FIG. 2 are represented as follows. For each LED  12   a ,  12   b  and  12   c , a high level line is used to indicate that an LED is “active” and a low level line is used to indicate that an LED is “inactive”. The LEDs within LED array  12  are activated for periods of time such that the human eye perceives the alternate color of each of said yellow, orange and red LED (i.e. long enough activation periods). At the same time, the user sees the color of a particular LED briefly enough so that the “look” of a flame is produced with the requisite flicker and change of color inherent in a real flame.  
         [0027]    By doing so, it is possible to achieve a realistic color transition effect on shell  40  as the human eye will perceive the resulting visual display from LED array  12  on shell  40  as being mix of color with moving yellow, orange and red hues. In addition the human eye will perceive that at times, more than one LED is “active” due to the well-known after image that the eye sees even after an LED is already off. Accordingly, unlike the conventional flame bulbs that simply light up or have two wire filaments that are used to cause a twinkling effect, this LED-based flame source will appear to flicker much more like a real flame.  
         [0028]    Also, while it is not explicitly shown on the activation characteristics in FIG. 2, each “active” period for a particular LED preferably represents the turning on and off of the LED at a suitable high frequency rate (e.g. 160 times per second per “active” period). It should be understood that it is possible to operate LED assembly  12  during “active” periods without turning on and off (i.e. a steady on for the extent of the “active” period) although power requirements will be higher. The specific high frequency utilized for turning the LED on and off during the “activation” period is selected such that the rapid blinking of an individual LED is not perceptible to the human eye. In practical terms, the LEDs of LED array  12  will be inactive for up to approximately 80% of the time, resulting in substantial power savings and long life for a fixed battery power source  16 . As discussed previously, a typical LED can operate on 3 volts and draw current on the order of 5 to 20 milliamps. However, since the LEDs within LED array  12  are inactive up to 80% of the time, the current draw of LED array  12  is greatly reduced and has been determined to be as low as 5 mA per LED  
         [0029]    In this particular example, light source driving circuit  18  sequentially activates LEDs  12   a ,  12   b  and  12   c . As shown, the following activation cycle is executed: red (12aON1), orange (12bON2), yellow (12cON3), orange (12bON4), yellow (12cON5), orange (12bON6), red (12aON7), orange (12bON8), yellow (12cON9) etc. It has been determined that it is beneficial to cycle between yellow and orange, between orange and red, but not between red and yellow, in order to minimize the “color” transition difference. Further, since LED array  12  is encased in a translucent shell  40 , the LED colors will mix and blend providing an impression that the shell  40  “glows” much like a true flame glows.  
         [0030]    It has been determined that when using LEDs that emit light at different frequencies (i.e. the frequencies associated with yellow, orange, red etc.), it is preferable to sequentially activate LEDs that emit light at frequencies which are close together in order to minimize the length of the color “steps” (i.e. to minimize the visible difference in color between activated LEDs). Accordingly, the LED lighting sequence steps in the example (i.e. as shown in FIG. 2) follow such transition rules. For example, in the case of the yellow, orange and red LEDs shown in FIG. 2, yellow is never activated before or after red. Rather, since orange is closer in emitted color to yellow and red, activation transitions move between red and orange and between orange and yellow. However, it should be understood, that many other specific lighting sequences could be used.  
         [0031]    [0031]FIG. 3 shows an example implementation of LED lighting assembly  30 . The main component is a light source driving circuit  18  that contains the logic circuitry that controls the output of LED array  12 . Light source driving circuit  18  is most likely a designed chip on board (COB) that can be customized for this application. Light source driving circuit  18  could be adapted to be integrated with the LEDs of LED array  12  to form a single sub-assembly complete with embedded program. The outputs of light source driving circuit  18  are each connected to a separate LED in LED array  12 . LED array  12  itself is connected in series with a load resistor RL that limits the current passing through the LEDs of LED array  12 .  
         [0032]    The preprogrammed sequence controls the output state of the flame simulating device  10 . As discussed above, it is preferred to leave the input unconnected in order to cause the LEDs of LED array  12  to light up in a sequential order. It should be understood that although this exemplary embodiment contains the aforementioned inputs this embodiment is only one example implementation. Other embodiments may contain fewer or greater inputs depending on the specific implementation. Light source driving circuit  18 , its functionality and components are described in greater detail below.  
         [0033]    Now referring to FIGS. 2, 3 and  4 , FIG. 4 illustrates a light source driving circuit  18  in block diagram form. Specifically, light source driving circuit  18  includes a microcontroller  52 , an oscillator  54 , a latch  56  and a driver  58 . Microcontroller  52  is electrically coupled to oscillator  54 , through the SCK line  51 , and to latch  56 , through the RSR line  53  and OFF line  55 . Oscillator  54  is also coupled to the latch  56  through the CK line  57 . In turn, the latch  56 , through information lines  59 , is coupled to the driver  58  which itself is electrically coupled to the LEDs in LED array  12  through output lines  61 .  
         [0034]    Microcontroller  52  determines the output state of the flame simulating device  10 , which could be programmable or off. This unit has three inputs, preprogrammed sequence, S (sleep) and R 2  (resistor  2 ) and three outputs, SK (stop clock), RSR (random or sequential) and OFF. Connecting the S input to Vss causes microcontroller  52  to enable the clock signal and latch  56  by sending the appropriate digital signals over the SCK  51  and OFF  55  lines respectively. The result is that the flame simulating device  10  is activated thereby causing LED array  12  to emit light.  
         [0035]    Flame simulating device  10  continues to function until the unit is turned off, at which point, microcontroller  52  disables the clock signal by sending the appropriate digital signal through the SCK line  51  to oscillator  54 . At this time, microcontroller  52  also disables latch  56  by sending the appropriate digital signal through the OFF line  55 . This causes the output to be disabled and the flame simulating device  10  to shut down. Since the preprogrammed sequence line is unconnected, the LEDs of LED array  12  light up sequentially according to a particular transitional rule (i.e. following a strict color order) as will be further described. Microcontroller  52  sends the appropriate digital signal, through the RSR line  53  to the latch  56 , which in turn generates the appropriate output.  
         [0036]    Oscillator  54  generates the periodic clock signal that is used to control timing within the circuit. The oscillator has two inputs, SCK (stop clock) and R 1  (resistor  1 ), and one output, CK (the clock signal). The clock signal is transmitted to latch  56  along the CK line  57 . The resistor connected to R 1  together with an internal capacitance determines a time constant for the circuit, which in turn determines the period of the clock signal. During normal operation, an appropriate digital signal is received from microcontroller  52  along the SCK line  51  and the clock signal is enabled. When flame simulating device  10  is shut off, microcontroller  52  sends an alternative signal via the SCK line  51  and the CK (clock) signal is disabled.  
         [0037]    While the clock rate of the LED controller can be set at 160 Hz, the actual flash rate of the individual LEDs (i.e. yellow LED  12   a , orange LED  12   b , and red LED  12   c ) can be varied throughout the length of the programmed routine, resulting in a more “flame like” appearance. Individual LED frequencies are set visually and then programmed directly into processor. As discussed before, a maximum of one LED is activated at any given time and even when a LED is activated it is being blinked on and off at a rapid frequency. Even so, a user will not perceive that there are any times when all LEDs are inactive (when in fact up to 80% of the time there will be no activated LEDs). As discussed above, since a maximum of one LED is activated at any given time (i.e. there are times at which all LEDs are inactive for short bursts of time), it is possible to run flame simulating device  10  on a set (i.e. finite such as a battery) power supply  16  for a relatively long time. Specifically, it is possible to run flame simulating device  10  for longer than a device which requires at least one LED to be powered at a given time.  
         [0038]    Latch  56  contains the logic circuitry used to generate the appropriate output sequences. Latch  56  has three inputs, CK, RSR and OFF, and a number of outputs equal to the number of LEDs in LED array  12 . Each output corresponds to a separate LED in LED array  12 . Based on the preprogrammed sequence, latch  56  activates each of the appropriate output signals sequentially. It should be noted that latch  56  can also be programmed to sequence the output in different orders other than sequentially, although it is preferred in this invention to have sequential activation of LEDs in color order.  
         [0039]    Driver  58  is essentially a buffer between latch  56  and the LED array  12 . Driver  58  ensures that sufficient power is supplied to the LEDs in LED array  12  and that the current drawn from the outputs of latch  56  is not too great. During normal operation, the output of the driver  58  tracks the output of latch  56 .  
         [0040]    It should be understood that the above circuit descriptions in FIG. 3 and FIG. 4 are only meant to provide an illustration of how LED assembly  30  may be implemented and configured and that many other implementations are possible. LED assembly  30  is not circuit dependent and therefore neither is flame simulating device  10 . There are many possible circuit configurations that may be used in alternative embodiments to achieve a result substantially similar to that described above.  
         [0041]    Reference is now made to FIG. 5, illustrated therein is the MAIN OPERATION routine  100  utilized by microcontroller  52  to control the output of LED array  12 . The routine commences at step ( 102 ) when the flame simulation device  10  is turned “on”, that is, S switch  20  is manually closed. It is also possible for switch to be closed using various types of activation devices (e.g. a an audio deactivation device as will be described in relation to FIG. 6). At step ( 104 ) microcontroller  20  enables the clock signal and latch  24  by sending an appropriate signal through the SCK  51  and OFF  55  lines respectively.  
         [0042]    At step ( 108 ) microcontroller  52  determines the preprogrammed sequence input and sends the appropriate digital signal to latch  56  through the RSR line  53 . In turn latch  56  generates the appropriate output at step ( 110 ). That is, at step ( 110 ) the LEDs in LED array  12  are turned on in sequential order. Specifically, yellow, orange and red LEDs  12   a ,  12   b  and  12   c  are sequentially activated in a “single LED” and “up/down” sequence according to the color transition rules discussed above.  
         [0043]    As noted, it has been determined that it is beneficial to cycle between yellow and orange, between orange and red, but not between red and yellow, in order to minimize the “color” transition difference. Accordingly, microcontroller  52  is programmed to follow these color transition rules when executing LED lighting sequence steps and activating specific LEDs. Application of these color transition rules is illustrated in the duty cycle graphs of FIG. 2 which indicate the following LED activation sequence: red ( 12   a ), orange ( 12   b ), yellow ( 12   c ), orange ( 12   b ), yellow ( 12   c ), orange ( 12   b ), red ( 12   a ), orange ( 12   b ), yellow ( 12   c ).  
         [0044]    Then at step ( 114 ) microcontroller  52  determines whether or not flame simulation device  10  has been turned “off”. If not, then the routine cycles back to step ( 108 ) and repeats itself. If so, then at step ( 116 ), microcontroller  52  disables the clock and latch  56  by sending the appropriate signals over the SCK  51  and OFF  55  lines respectively. Flame simulating device  10  is then inactive until the switch closes again at step ( 102 ).  
         [0045]    [0045]FIG. 6 illustrates an optional audio deactivation device  150  that can be used to deactivate light source driving circuit  18 . Audio deactivation device  150  allows the user to in effect “blow out” the flame (as a user typically “blows out” a candle) by blowing air close to the LED array  12  as will be described. Specifically, audio deactivation device  150  includes a microphone  152  and another latch  156 . It should be understood that any other sound sensitive device (e.g. a piezo crystal buzzer, etc.) could be utilized instead of microphone  152 . Preferably, microphone  152  is positioned in close proximity to LED array  12  for most intuitive effect.  
         [0046]    When a user blows at LED array  12 , microphone  152  senses the sound increase and a large delta spike in circuit resistance results within circuit resistors (shown as 15 Kohm, 29 Kohm, 4.7 Kohm), capacitor (shown as 104 microfarads) and transistor T 2 . In turn, the trigger input TG of latch  156  is enabled and causes latch  156  to disrupt the voltage being provided at VDD to output Cout which is connected to the power input (not shown) of light source driving circuit  18 .  
         [0047]    In addition, it is contemplated that a photosensor-based turn-off circuit (not shown) could also be utilized to deactivate light source driving circuit  18  and audio deactivation device  150  when a photosensor (not shown) is exposed to light. When the power is removed from light source driving circuit  18  and audio deactivation device  150 , the latches associated with these circuits are reset. Once the light dims, the photosensors will emit an operational signal (i.e. time to turn flame simulating device  10  back on) and the associated latches will then be enabled again to power LED array  12 . The use of such a photosensor-based turn-off circuit results in additional power savings since the unit would be turned off during daylight hours and does not require manual deactivation and activation (i.e. in a restaurant or other hospitality setting).  
         [0048]    Various alternatives to the preferred embodiment of the flame simulating device  10  are possible. For example, the LED array  12  of flame simulating device  10  can be fabricated out of different types of LEDs that may, for example, have different colors, intensities and dispersion angles. Furthermore, it is also possible to implement the LED array  12  with fewer or larger numbers of LEDs. Also, light source driving circuit  18  could be adapted to activate at least one LED at a time although there would be a commensurate rise in the required power from power supply  16  and a reduction in the lifetime of a set (i.e. finite such as a battery) power supply  16 . In addition, the shape, size and material of the shell  40  may be varied. Furthermore, power source  16  can be comprised of any appropriate type of battery. While it is preferred for power source  16  to have an output voltage in the range of 3 to 12 V DC, it is possible to manufacture the decorative display assembly to operate outside this range. In addition, many other circuit configurations may be used to implement the same or similar functionality.  
         [0049]    As will be apparent to persons skilled in the art, various modifications and adaptations of the structure described above are possible without departure from the present invention, the scope of which is defined in the appended claims.