Circuit for Lighting Like Candlelight

This invention relates to a circuit for lighting like a candlelight, and more particularly to a circuit which can continuously and irregularly vary luminous intensity of a light emitted by the circuit.

An illuminating device which uses a candle or candles has a little utility because of possibility of breaking out of a fire and a limited lighting time of a candle. Many of illuminating devices of such kind have been changed to devices having electric lamps. But, such illuminating devices are irksome, because an electric lamp cannot easily vary luminous intensity of a light emitted by the lamp.

Therefore, electric lighting devices which can change luminous intensities have been developed using mechanical or electrical methods. In the mechanical methods, the devices become complicated and expensive structures. In the electrical methods, it is not possible to obtain a device which can continuously and irregularly vary luminous intensity of a light. A device which has a plurality of electric lamps in an envelope and can change number of lighting lamps is known. A device shown in U.S. Pat. No. 3,710,182 has an incandescent lamp and a thyristor being connected in series across an alternate current source and an oscillator supplying gate pulses to the thyristor to energize the lamp. The device can vary luminous intensity of a light only constantly or periodically.

Accordingly, it is an object of this invention to provide a circuit for lighting like a candlelight which can vary luminous intensity of a light continuously and irregularly.

Another object of this invention is to provide a circuit for lighting like a candlelight which is simple and inexpensive.

The foregoing objectives are achieved according to this invention through the provision of a circuit for lighting like a candlelight comprising a lighting means having at least one lamp, and a control means having a plurality of oscillators which can be oscillated with substantial equal frequencies and controlling an electric current flowing through the lighting means. The each oscillator emits a light as an output thereof. The control means controls the electric current by all of the lights emitted from the oscillators. The each oscillator may be a relaxation oscillator having a neon tube, the control means may have a photo dependent resistor which is adapted to receive a composite light of lights emitted by neon tubes, whereby the resistance of the photo dependent resistor is varied so as to control the electric current flowing through the lighting means.

Various other objects, features, and attendant advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawing wherein the sole FIGURE is a diagram of a circuit of one embodiment of this invention.

In an embodiment of this invention shown in FIGURE, a pair of terminals 10 and 11 are provided for connection to a conventional alternate electric source. A lighting means or an incandescent lamp 12 is connected between the terminals 10 and 11.

13 generally designates a control means which has three relaxation oscillators 14. The each oscillator is connected between the terminals 10 and 11 and adapted to supply a direct current thereto by a diode 15 and a condenser 16. The each oscillator 14 is composed of a resistor 17, a condenser 18 and a source of light or a neon tube 20 which repeats lighting off and on. The oscillators 14 are made so as to have substantial equal frequencies. But, very small differences are irregularly created because the frequency of the each oscillator 14 is independently changed a small value owing to various conditions, for example temperature of air surrounding the oscillator and a small variation in the voltage of the electric source. Therefore, a composite light of lights emitted by the neon tubes 20 irregularly makes a beat phenomenon which means that the luminous intensity of the composite light irregularly varies to a large value at a time and to a small value at the other time.

The control means 13 has a bidirectional triode thyristor 21 which is connected between the lamp 12 and the terminal 11. A bidirectional diode thyristor 22 is connected to the gate electrode of the thyristor 21 for switching of the thyristor 21.

The control means 13 also includes a photo dependent resistor 23 which is adapted to receive the composite light of lights emitted by the neon tubes 20, whereby the resistance thereof is irregularly varied by the luminous intensity of the composite light. A condenser 24 is connected in series with the photo dependent resistor 23. The circuit composed of the photo dependent resistor 23 and the condenser 24 is connected in parallel with the thyristor 21, and the connecting point between the photo dependent resistor 23 and the condenser 24 is connected to the thyristor 22. A resistor 25 is connected in parallel with the photo dependent resistor 23. Therefore, the current flow angle of the thyristor 21 for supplying an alternate current to the lamp 12 is controlled by the varying of the resistance of the photo dependent resistor 23. The photo dependent resistor 23 has a small time lag for varying the resistance thereof, therefore it does not sensitively respond to the lighting off and on of the neon tubes 20, and it responds to an averaged value of the composite light in a short time interval. The resistor 25 makes it possible that the lamp 12 can be lighted with a small luminous intensity even at a time when the resistance of the photo dependent resistor 23 becomes to a large value.

Thus, the luminous intensity of the light emitted by the lamp 12 can be continuously and irregularly varied like a candlelight.

In this invention, various modifications will be made. For example, it is possible that a lighting means can include a plurality of lamps connected in series and/or parallel. A plurality of oscillators which are not relaxation oscillators can be used for control a current flowing through a lighting means by all of lights emitted from the oscillators.

The foregoing is of course considered as illustrative only of the principle of the invention. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings.