Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1998-11-06
2001-11-13
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S573000, C313S317000
Reexamination Certificate
active
06316872
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to a cold cathode fluorescent lamp device, and in particular, to a high luminance, high efficiency, long lifetime monochromatic, multi-color or full-color cold cathode fluorescent lamp devices (CFD).
2. Description of the Prior Art
Hot cathode fluorescent lamps (HCFLs) have been used for illumination. The HCFL operates in the arc gas discharge region. It operates at a relatively low voltage (of the order of 100 volts), large current (in the range of 60 milliamps), high efficiency (such as 80 lm/W, and the cathode is usually operated at a relatively high temperature such as 400 C. Typically, the cathodes would first need to be heated to an elevated temperature by means of a starter and a ballast before the HCFL may be turned on and operated at its optimum temperature. Thus, in order to turn on an HCFL, a voltage is applied to the starter which generates gas discharge. The heat produced by the gas discharge heats up the cathode and an electron emission layer on the cathode to an elevated temperature so that the layer emits electrons to maintain the gas discharge. The gas discharge generates ultraviolet radiation which causes a phosphor layer in the lamp to emit light.
When the cathode and the electron emission layer are first heated to an elevated temperature during starting, the heating causes a portion of the electron emission layer to evaporate, so that after the HCFL has been started a number of times, the electron emission layer may become deficient for the purpose of generating electrons, so that the HCFL needs to be replaced. This problem is particularly acute for displaying information that requires constant starting and turning off the HCFLs. Thus, HCFLs are not practical for use in computer, video, and television applications. For the purpose of illumination, HCFLs requires starters and ballasts, which may also become defective after a period of constant use. This also reduces the lifetime of the HCFL. It is thus desirable to provide an illumination device with improved characteristics.
Currently available traffic light and outdoor large size sign displays are normally made of incandescent lamps. They have high brightness, but many drawbacks:
a. High maintenance cost because of short lifetime and low reliability. This is the case especially for traffic lights or signs on free ways, where changing and repair of the lights are very inconvenient and expensive.
b. High power consumption because of low luminous efficiency, which is about 10 lm/W. For traffic lights and other multi-colored displays, luminance efficiency is even lower because colored light is obtained by filtering white light emitted from the incandescent lamps, so that the colored fight so obtained is much reduced in intensity. The effective efficiency for such applications is only 4 lm/W or lower.
c. Under direct sunight, ON/OFF contrast is very low, i.e., even OFF status looks like ON, which can cause fatal results.
It is, therefore, desirable to provide an improved illumination device which avoids the above-described disadvantages.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantages of the prior art.
In one aspect of the invention, a light transmitting container containing a gas medium is used to house at least one cold cathode fluorescent lamp (“CCFL”). The gas medium and the container increase luminous efficiency of the at least one lamp by reducing heat lost from the lamp and the effect of the ambient temperature on the lamp.
In another aspect of the invention, a light transmitting container is used to house at least one cold cathode fluorescent lamp having at least one electrode. The container increases the luminous efficiency of the lamp by reducing heat loss from and the effect of ambient temperature on the lamp. An electrical connector connected to the at least one electrode is adapted to be electrically and mechanically connected to one of a number of conventional electrical sockets. In this manner, a gas discharge device formed by the above elements may be used to replace a conventional incandescent lamp.
According to yet another aspect of the invention, a light transmitting container is used to house at least one cold cathode fluorescent lamp having at least one electrode so as to increase the luminous efficiency of the lamp by reducing heat loss from and the effect of the ambient temperature on the lamp. A driver circuit in the container is connected to the at least one electrode to supply power to the lamp. The container containing the lamp and the driver circuit, therefore, form a complete gas discharge device that may be used to replace a conventional incandescent lamp.
According to one more aspect of the invention, a light transmitting container is used to house at least one elongated cold cathode fluorescent lamp having two ends so as to increase the luminous efficiency of the lamp by reducing heat loss from and the effect of the ambient temperature on the lamp. A base plate is used to support the lamp at or near the two ends at two support locations and the base plate is attached to the container. Support means is used to connect a portion of the lamp at a location between the two support locations to the container to secure the lamp to the container. By supporting the lamp at a location between the two support locations, the lamp is less likely to be damaged by vibrations, such as those present in a traveling vehicle.
According to yet another aspect of the invention, a container is used to house at least one cold cathode fluorescent lamp so as to increase luminous efficiency of the lamp by reducing heat loss from and the effect of the ambient temperature on the lamp. The at least one lamp has at least one electrode outside the container. Since the container reduces heat loss from the lamp, if none of the electrodes of the at least one lamp is outside the container, the heat generated by the electrodes would cause the temperature of the lamp to become elevated, thereby reducing the luminous efficiency of the lamp. By placing at least one electrode outside the container, the temperature of the lamp is less likely to become elevated.
In yet another aspect of the invention, a CCFL is proposed comprising a tube that has an elongated portion and an enlarged portion with cross-sectional dimensions larger than those of the elongated portion, in order to accommodate larger size electrodes. The larger size electrodes can be used to provide a higher quantity of electrons in the CCFL, thereby resulting in the higher brightness of the device. Larger size electrodes also reduce the amount of heat generated, thereby enhancing the lifetime of the device.
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patent: 2261
Ge Shichao
Ge Xiaoqin
Ge Yiping
Lam Victor
GL Displays, Inc.
Patel Ashok
Skjerven. Morrill MacPherson LLP
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