Patent Application
20070236947
1. Technical Field
The invention relates to decorative, imitation candles and, more particularly, to an imitation candle simulating a lighted wick.
2. Description of the Problem
Numerous manufacturers have attempted to meet a demand for a flameless, candle like luminary using electrical illumination. There are many imitation candles available that use incandescent lamps or LEDs as a light source. These devices address people's concern with having an open flame indoors. Most of these devices 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 draws attention to the fact that the device is an imitation candle. 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.
In addition, there are also imitation candles available that utilize one or more very small incandescent lamps or LEDs as the light source which do not place the light source inside a flame shaped structure. Examples exist of imitation candles which have a deep well on the top to simulate a candle that has been burning for some time. As these light sources are relatively small they can be concealed within the deep well of the artificial candle. From most viewing angles, the wall of the artificial candle would be between the light source and the viewers eye. At these viewing angles there is no artificial flame structure visible that would detract from the candle's realism. However, when viewed from above, the small light source (or sources) are readily visible and reveal that the candle is an imitation. It would be desirable to provide an imitation candle that is viewable from the side or above without revealing an obvious artificial light source.
A key visual element of a real flame is a rather intense area of light. When the flame is viewed directly, in a darkened environment, the flame can become a source of glare for an eye accommodated to scotopic vision. Eyes adjusted to darkness cannot tolerate the large contrast in brightness and as a result, the physical outline of the flame is often lost to the eyes in the glare. In the case of artificial flame structures, the outer surface is often frosted so that the flame structure is itself lit up. By spreading the light from the artificial light source across a larger surface area, the intensity of light across the surface is much less than that from an illumination source. Because of this lack of point source intensity, the brain does not interpret the flame structure as a real flame, but still comprehends the structure. Incandescent lamps that have clear glass flame structures reveal an intense filament, but the filaments are generally linear, detracting from their appearance. The glass, though clear, may still ve visible as well.
U.S. Pat. No. 6,616,308, which is incorporated herein by reference, teaches an imitation candle configured to diminish any expectation on the part of an observer of seeing an open flame. Many of the typical deficiencies found in imitation candles are addressed in the '308 patent. The flame structure is eliminated and so does not detract from the candle's realism when not illuminated. In addition, the candle's structure is such that from most viewing angles the observer would not expect to have a direct view of the flame and so the lack of a flame when illuminated does not detract from the candle's realism. When the candle is off and viewed from above, there is no visible bulb or other structure to reveal that the candle is artificial. An imitation wick, visible when the candle is viewed from above, can be used to complete the illusion that the candle is real. However, when the imitation candle of the '308 patent is on and viewed from above, there is no bright source of light at the end of the wick as would be expected in a real candle. It would be desirable to provide an artificial candle with an artificial wick that when viewed from the side or above, does not reveal an obvious light source or other structure that would reveal that the candle is artificial, while at the same time providing a bright source of light at the tip of the wick when the candle is on.
One approach to creating a realistic illusion of a flame is disclosed in U.S. patent application Ser. No. 10/844,075, filed 12 May 2004, which is incorporated herein by reference. This application discloses an LED hidden within a fixture above an imitation candle body. Light emitted by the LED is directed to illuminate the candle body and wick from above. The LED is driven by a variable current to produce flickering light. The imitation wick has a reflective tip which reflects the incident light to create a small bright spot. The bright spot at the tip of the wick is sufficiently bright that even though the light source may be flickering, the intensity remains strong enough that the eye sees the resultant glare but cannot see the change in intensity of the spot. At the same time, light shines past the wick and onto the candle body where it is diffused throughout a relatively large volume. The light intensities within the candle body are much lower resulting in a dramatic, flickering effect.
For standalone imitation candles that are not housed in a permanent fixture, the approach of the '075 application is more difficult to effect since there is no convenient place to hide the LED but within the candle body itself. An approach to creating a realistic illusion of a flame that does not require a permanent fixture is disclosed in U.S. patent application Ser. No. 11/053,397, filed 31 Mar. 2005, which is incorporated herein by reference. This application discloses an LED hidden within an imitation candle body as in the '308 patent. One end of a fiber optic wick is positioned in close proximity to the LED and captures part of the emitted light. The captured light is directed to the upper, exposed end of the fiber optic wick which then glows brightly in response. The majority of the length of the artificial wick is covered by a dark material, so the overall visual effect is that of a real wick, the tip of which is glowing brightly. The candle can be viewed form the side or above without revealing any light sources or artificial structures that detract from the candles realism.
While the approach described in the '397 application is effective, it may be desirable to produce a light intensity at the tip of the wick that is even brighter than that which can be achieved using a fiber optic wick to transmit a portion of the light emitted by the LED. It would be desirable to place the light source at the tip of the wick for maximum brightness while at the same time incorporating the light source and its support structure into an artificial wick that does not detract from the candles realism when the candle is viewed from the side or from above.
The present inventors are familiar as well with a decorative, miniature Christmas tree, which is constructed from wires which terminate in surface mount technology light emitting diodes. The wires are soldered to the SMT LEDs, which are scattered about the tree producing the effect of a fully lighted tree.
According to the invention there is provided an imitation candle having a body and an imitation wick. The imitation wick extends outwardly from the body and supports a light emitting diode on its exposed portion at a location spaced from the body of the imitation candle. An energization circuit for the light emitting diode is housed within the body and electrical leads extend from the energization circuit along the imitation wick for connection to the light emitting diode.
Additional effects, features and advantages will be apparent in the written description that follows.
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:
Referring to
While a cordless model is preferred, it is possible to provide external energization to the device. An internal light source 9 is provided, preferably using a super bright light emitting diode (LED) as described in U.S. Pat. No. 6,616,308, but it could be an incandescent source. External light source 3 is preferably a surface mount technology (SMT), super bright, light emitting diode (LED). In addition to supplying current to the light sources 3 and 9, electronics module 29 may include on/off timers, daylight sensors and a flicker energization circuit to cause either the light source 3, 9 or both, to flicker as would an unstable candle flame.
The size and position of main circuit board 8 is chosen to control the illumination levels from top to bottom of the imitation candle body 1, reducing light emission from the lower portion of the body. A secondary circuit board 10 is mounted along one of its edges to the upper surface of main circuit board 8. Secondary circuit board 10 provides conductive traces 11 to supply current to the external light source 3 along a narrowed section of the secondary board which serves an an imitation wick 2. The artificial wick 2 is a narrowed section of the secondary circuit board 10 and passes through a hole 12 in the upper surface of the candle body 1. Hole 12 would typically be filled with a small, insulating plug (not shown) to provide mechanical support for the artificial wick 2. A dark colored, opaque sleeve (described below) would typically surround the exposed portion of artificial wick 2 serving to disguise the artificial wick 2 and give it the appearance of a real wick which has burned down. Alternatives to the sleeve could be used to disguise artificial wick 2 as a wick, but care must be taken not to interfere with light emission from the external light source 3.
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 29 sources a varying amount of current to LEDs 3, 9. 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 light emitting diodes 3, 9. The voltage source provided by battery 50 is connected to the transistor 60 emitter by resistor 56 and to the 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 above 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 LEDs 3, 9 always produce a minimum level of light output when the device is on.
Variation in light output is effected by variably increasing the current supplied to LEDs 3, 9. A hex inverter, such as a SN74HC14N hex inverter, available from Texas Instruments of Dallas, Tex., 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 (U1E) only but is identical for each of inverters 91-94.
The supply of power to the internal LED 9 is described first. 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 LED 9 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 9 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 9 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 9. 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 9. 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 9. 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 9 than oscillators 68 and 70. This contributes still more to the impression of randomness in the light output of LED 9 by 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 9 by resistor 80 and diode 82 to the summing junction and than by resistor 126. A capacitor 125 may be connected between Vcc 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 externally mounted LED 3 is intended to be driven less hard than an internal LED 9 and is connected to the output of the summing junction fed by resistor 126 and PNP transistor 60. Luminosity of LED 3 may be determined by varying the resistance of a resistor 136, if desired, which operates as a voltage divider assuring that LED 3 luminesces at a lower level than does LED 9. Swapping the positions of the LEDs changes which gives off more light.
While the invention is shown in only a few 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.
