Background Art Many people find candle light pleasant. The flickering of light and movement of shadows across a floor or on a nearby wall can be almost hypnotically soothing. As a result, candles have remained popular for generations since the invention of more practical electrical lighting, especially for decorative and mood setting purposes. This has remained so notwithstanding the hazard posed by open flames and the consequent danger of household fires.

Few people consider it safe to leave a lit candle unattended.

Consequently, numerous manufacturers have attempted to meet a demand for a candle like luminary using electrical illumination. There are many imitation candles available that use incandescent lamps or LED's as a light source. While these address people's concern with the open flame, most try to implement the appearance of a realistic flame using a specially shaped bulb or lens that is exposed to view. Typically, the bulb or lens sits on top of a thin cylindrical sleeve, which is shaped and colored to resemble a candle. The results are typically disappointing, especially when these devices are not illuminated. The visible, flame shaped artificial light source makes the imitation candle as a whole appear artificial. The result can look more like a caricature of a candle than a real candle. The color of incandescent light can leave something to be desired in many candles as well.

The use of frosted glass cylinders around incandescent light sources to diffuse light is known. Such products are pleasant and popular. However, the light produced by an incandescent source can be quite broad, and the top of the lamp must be open to allow heat to escape. Another product, sold by Eternalight, Inc. of Cortaro, Arizona, provides a plurality of LEDs arranged on a base inside a frosted glass cylinder. A computer is used to control current supplied the LEDs to simulate an artificial flame of changing color and intensity of emitted light. Control of the LEDs also gives the simulated flame shape and motion. A similar product is sold by Norex Enterprises, Inc. of Blauvelt, New York. In both cases the products place the artificial flame above a base. A frosted glass cylinder, open at the top, is then set on the base. The appearance is intended to simulate a candle inside a glass lamp.

Candles of course do not all come in one shape or size. While a classical image of a

candle is of a long, thin, tapering rod, which stands upright in a candle stick and which leaves its flame exposed as it burns down, many candles come as a relatively short to circumference block or cylinder which is self supporting. Such candles commonly leave the outer wall of the candle intact as the candlewick burns down. When this happens, the candle flame is no longer directly visible when viewed from the side. This results in a diffuse, flickering glow visible through the paraffin wall of the candle.

Disclosure of the Invention One object of the invention is to provide an electrical candle that provides realistic candle like light.

Another object of the invention is to provide an electrical candle that presents a realistic appearance when the light source is not illuminated.

Yet another object of the invention is to provide an imitation candle that uses a light-sensing device to turn the light source off during the day.

Still another object of the invention is to provide a flicker circuit that provides three or more distinct light levels that vary in a pseudo-random manner to provide a realistic variation in light output akin to a candle flame being disturbed by gentle air currents. A realistic flicker provides one more subconscious cue that the candle is real.

Yet another object of the invention is to provide a luminary that gives a very realistic representation of a broad, self supporting candle that has burned down to the point where the flame is not visible.

These and other objects are achieved as is now described. The imitation candle of the present invention hides a light source within the body of the luminary in order to illuminate the body to look like a real wax candle internally illuminated by a depressed flame. There is no exposed bulb shaped like an imitation flame to betray the fact that the imitation candle is not real.

The imitation candle has a body made from a translucent material having optically transmissive properties similar to candle paraffin. In a preferred embodiment the body of the imitation candle has a relatively large base or circumference relative to its height and is self supporting. The candle body is shaped to simulate a candle which has partially burned down, for example by forming a depression into an upper surface of a cylindrical candle body.

The light source is preferably a super bright, light emitting diode (LED), which functions as a highly directional, near point source. An emission color, such as amber, is selected for the LED to produce a light similar in color to that of a paraffin fed flame. A simple circuit using multiple oscillators running at close frequencies, but not the same frequency, creates a realistic, pseudo-random flicker for light emitted by the LED.

The directional, and small area of light emission, from the small, high intensity light source, its location horizontally centered and toward the top within the imitation candle, coupled with the internal contours and material of the imitation candle serve to diffuse the light in a manner evocative of candle light. The body of the imitation candle is preferably a translucent material, ideally candle wax. An LED may be positioned in a cavity enclosed within the translucent material, with the base of the LED being downwardly oriented. The cavity, where proximate to portion of the LED above its base is sized and shaped to closely conform to the size and shape of the LED's housing. The translucent material surrounds the LED on the sides and top and serves to diffuse the light throughout the portion of the imitation candle at or above the height of the LED and makes direct viewing of the LED at best inconvenient. An LED positioned near the top of the body causes the top of the imitation candle to be more brightly illuminated than the lower parts of the candlestick. This effect can be enhanced by positioning an opaque light block around the base of the LED to prevent diffusion of light into the lower portions of the imitation candle. These steps simulate the usual diffusion of light in a real candle. Recessing the top within the side walls presents the appearance of a candle that has already been burning for some length of time. The body of the imitation candle is preferably made from real wax to further enhance the imitation candle's realism. Alternatively, frosted glass or plastic materials may be used.

The power consumption of super bright LEDs is low enough at low illumination levels that reasonable battery life can be achieved. Alternatively, a wall-cube style power supply could be used to supply power and eliminate the need periodically to replace battery cells.

Rechargeable cells can be used in conjunction with a solar cell or other recharging means. A simple light sensing device can be used to turn the LED off during daylight hours and extend battery life in battery operated versions of the candle.

Additional effects, features and advantages will be apparent in the written description that follows.

Brief Description of the Drawings The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: Fig. 1 is a perspective view of a preferred embodiment of the imitation candle of the invention.

Fig. 2 is a partial cutaway view of an embodiment of the invention.

Fig. 3 is a partial cutaway view of a preferred embodiment of the invention.

Fig. 4 is a circuit schematic for a luminary of the preferred embodiment.

Best Mode for Carrying Out the Invention Referring now to the drawings and in particular to Fig. 1 a preferred embodiment of the invention will be described. An imitation candle 10 includes a body 12 with a horizontal lower surface 14 on which the imitation candle rests, an upper surface 16 and a cylindrical vertical side wall 18 between the lower and upper surfaces. Imitation candle 10 is preferably sized to resemble a self supporting candle having a relatively large circumference compared to its height. Slender, tapering bodies resembling classical candles, and other shapes, are possible and such configurations are within the scope of the invention, but embodiments using such shapes may not provide as esthetically a pleasing appearance in use due to the expectation that a flame be visible.

While imitation candle 10 is illustrated as being cylindrical, other horizontal cross sectional shapes are possible, such as rectangular, as well as irregular shapes. Upper surface 16 includes an indented or depressed central region 20, which is preferably shaped to resemble a top portion of candle which has been reduced by melting to feed a flame supported from a central wick.

Fig. 2 shows a preferred embodiment of the invention in a cutaway view. A light source body 24 preferably emits highly directional light from a small area. This is advantageously achieved by using a super bright light emitting diode (LED) oriented with to transmit most of its light upwardly toward the depressed central region 20. Light source body 24 is placed in a cavity 26 just below the surface formed by depressed central region 20. Cavity 26 extends upwardly from a large central cavity 126 in the lower portion of body 12. Cavity 26 is preferably sized to be just slightly larger than the light source body 24 with light source body nested upright therein.

The material 22 forming body 12 is preferably relatively thick and translucent and is shaped to resemble a candle that has been burning long enough to have burned away the inner portion of the wax (e. g. , depressed central region 20). The material 22 can be wax, frosted glass, or plastic and is chosen to diffuse the light from the light source body 24 so that, when viewed from the side, the light is evenly scattered and provides a fairly evenly distributed glow. Pigments added to relatively clear plastics or glass with frosted surfaces should also produce satisfactory results, although wax is preferred.

The light intensity on cylindrical vertical side wall 18 of body 12 will be roughly proportional to the square of the distance between the light source body 24 and the surface. The thickness of material directly above the light source body 24 can be selected to generate a'hot spot'of fairly intense light that is similar in size to the diameter of a real candle's flame.

Generally though, light source body 24 is positioned so as not to be conveniently directly

viewable from outside of body 12. In other words, optically diffusing material is preferably interposed between a casual viewer and the light source body 24 in directions to the side and above the light source body. Propagation of light downwardly from light source body 24 is preferably blocked by an opaque disk 92 positioned at the base of the light source body.

Light source body 24 is connected to a remote power source 30 by leads 28. Remote power source 30 may be provided by a conventional step down power supply which may be plugged into a household wall socket. Alternatively a power source may be provided by a battery. A switch 32, which may be manually activated, timer based, light sensitive, or even accept remote control commands, may be incorporated into the power supply. The remote power source 30 would typically be hidden in a base designed to look like a typical candle stand or it could be disguised as, or hidden in, another decorative element. The power source housing preferably includes a flicker circuit (described below) to cause the LED of the light source body 24 to vary in brightness in a pseudo-random manner to simulate the flickering of a real candle flame. Yet another option is to provide a solar cell that charges one or more rechargeable batteries.

Light emitted from light source body 24 should be highly directional and close to being a point source to achieve the best results. Light emitting diodes are conventionally housed in a light source body 24 which is made primarily of transparent plastic. The outer, light transmitting surface 170 of the body is cylindrically shaped, terminating at one end in a hemisphere. An LED is capped at the other, lower end in an opaque base 172. Most light is directed out the hemispherical end, with some escaping to the sides. Cavity 26 is essentially form fitted to the light source body to capture and diffuse emitted light. This allows light to impinge the cylindrical vertical side wall 18 level with the light source body 24 as well as the floor of the depressed central region 20. This enhances the already strongly directional aspect of an LED.

Fig. 3 shows an alternative embodiment of an imitation candle 110 which incorporates a replaceable battery. Light source body 24 is preferably provided by a super bright LED as described above. A battery housing 36 is translucent or transparent plastic and is enclosed in an enlarged lower cavity 126. Battery housing 36 holds two C cells 40 and 42 to provide a battery power source. Battery housing 36 encloses light source body 24 in a contoured bulge on top of the housing which couples light through to its surface. A printed circuit board 44 and an LED energization circuit 46 are positioned in the housing 36. Printed circuit board 44 blocks the downward projection of light allowing opaque dish 92 to be omitted. Embodiments of the invention using a single cell with a step up power supply can be used to save space in small candles. Additional cells for larger batteries can be used in large candles. The exterior

configuration of body 12 of imitation candle 110 is the same body used for imitation candle 10, with a depressed central region 120 set in an upper surface 116 provided to simulate a partially melted and burned away appearance within cylindrical vertical side wall 118.

Fig. 4 illustrates representative energization electronics 46 for driving an LED 124. A battery 50 is provided by two size C cells. Different power sources can be used depending upon desired battery life or the desired brightness to be obtained from the LED. As mentioned above, alternatives include combinations of solar cells and rechargeable cells or an outside line source of power. LED 124 is preferably provided in a Global Opto G-L202YTT-T amber light emitting diode package. Energization electronics may be switched on and off using a switch 52 which is attached at one pole to the positive terminal of battery 50. Switch 52 may be a photosensitive device, such a photosensitive transistor. Battery 50 also supplies Vcc within LED energization electronics 46.

LEDs have a constant voltage drop when conducting current and the intensity of light emission from an LED is controlled by varying the current sourced to the LED. Accordingly, the LED energization circuit 46 sources a varying amount of current to LED 124. The first major element of energization circuit 46 is a base current source provided by zener diode 54, resistors 56 and 62, and a PNP transistor 60, which sources current to the load, here a light emitting diode 124. The voltage source provided by battery 50 is connected to the transistor 60 emitter by resistor 56 and to base of the transistor by reverse oriented zener diode 54. The transistor is assured of being constantly biased on by the voltage drop set by the reverse breakdown voltage of zener diode 54 as long as battery voltage remains the minimum required for zener breakdown operation. Thus transistor 60 sources current to the load through which the current returns to ground. As a result LED 124 always produces a minimum level of light output when the device is on and the battery has a minimum charge.

Variation in light output is effected by variably increasing the current supplied to LED 124. A hex inverter, such as a SN74HC14N hex inverter, available from Texas Instruments of Dallas, Texas, is used to implement several parallel oscillators or clocks. All of the oscillators are identically constructed though external component values may be altered. In the preferred embodiment 4 of 6 available inverters (91-94) are used with resistors (105-108) providing feedback from the outputs of the inverters to the inputs. Capacitors 101-104 are connected from the inputs of inverters 91-94 to set the operating frequency of the oscillators. The connection of Vcc to the inverters is represented for inverter 90 (UlE) only but is identical for each of inverters 91-94.

Oscillators 68 and 70 are designed to be low frequency oscillators running at

approximately 2 Hz. Oscillators 68 and 70, formed using inverters 94 and 93, can use similar timing components to run at approximately a 10% difference in frequency. The 10% difference in frequency prevents oscillators 68 and 70 from synchronizing with each other or drifting past one another too slowly. Low frequency oscillators 68 and 70 provide current to the LED 124 through series connected resistors and forward biased diodes 76 and 78, and 72 and 74, respectively, to a summing junction. As a result, current flow through LED 124 is increased from the minimum set by the current source formed by PNP transistor 60 pseudo-randomly. When either of oscillators 68 or 70 is high, it supplies extra current to LED 124 and the LED becomes slightly brighter. When both of oscillators 68 and 70 are high, a third, higher level of current is supplied to the LED 124. The three current levels (both high, only one high, or both low) provide three brightness levels that can be selected by the choice of values for resistors 76 and 72 and the current from the current source. As long as the two oscillators are not synchronized, the three brightness levels will vary in a pseudo-random manner as the oscillators drift. Loose component tolerances are acceptable as contributing to the degree of randomness in current sourced to LED 124.

In some applications oscillators 68 and 70 may be set to have as great as a 2: 1 variation in frequency. The rate at which the oscillators drift past one another is consequential to the appearance of the luminary.

In the preferred embodiment oscillator 66, formed using inverter 92, operates at about 8 Hz. and provides two more current levels. Three parallel current sources allow for a total of six brightness levels. Again the output from the inverter is fed through a series connected resistor 84 and forward biased diode 86 to a summing junction and then by resistor 126 to LED 124. The value chosen for resistor 84 is higher than for resistors 78 and 74 with the result that oscillator 66 makes a smaller current contribution to LED 124 than oscillators 68 and 70. This contributes still more to the impression of randomness in the light output of LED 124by providing that changes in light output occur in differing sized steps. Oscillator 64, formed using inverter 91, is also set to run at about 8 Hz. The resistance of resistor 80 is comparable to that of resistor 84 so that oscillator 64 contributes a current comparable to the current supplied by oscillator 66. The current from inverter 91 is routed to LED 124 by resistor 80 and diode 82 to the summing junction and than by resistor 126. A capacitor 125 may be connected between V,, and ground to short circuit noise to ground preventing circuit noise from causing the oscillators to synchronize with one another.

As shown, two of the gates of the hex inverter are not used, but these gates could be used to create two more oscillators with outputs driving additional candles using multiple LEDs or

supplying additional current levels to a single LED.

The invention provides an imitation candle that provides realistic candle like light while retaining a candle-like appearance when unlit. The light produced by the invention has a multitude of light levels that vary in a pseudo-random manner to provide variation in light output akin to a candle flame being disturbed by gentle air currents. The imitation candle of the invention can be readily used with decorative light fixtures that would typically use a candle, while sparing the user from the need of periodically cleaning the fixture of wax. The imitation candle can also serve as a stand alone luminary or it can be readily used in a variety of fixtures, such as outdoor landscape lights, patio lights, solar powered lights, night lights, etc.

While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.