FIELD OF INVENTION

[0001] This invention relates to a light tube, in particular a vacuum light tube with electromagnetic compatibility (EMC) filter.

BACKGROUND OF INVENTION

[0002] Light tube is commonly used as a lighting device nowadays. However, shortcomings exist on conventional light tubes on the market. First, after the light tube is used for a period of time, the outer layer of the light tube will be affected in different extents by natural phenomena such as air, temperature, humidity or wind. Commonly, dust, dew, fog or frost precipitates on the inner/outer surface of the outer layer, affecting the inner/outer surface in different extents, for example reducing the luminance emitted from the light source inside the outer layer and affect the outlook of the light tube. Furthermore, as dust accumulates in the light tube and is unable to be cleaned, the operating temperature of the light tube increases as more dust accumulates, resulting in short circuit or open circuit in the light tube and render the light tube inoperable. More serious cases may lead to fire accidents.

[0003] In another aspect, as conventional light tube has the problem of insufficient space, it is hard to add protective circuitry. A common protective circuitry is EMC (Electromagnetic Compatibility) filter. When the light tube is operating, starting or operating of large magnetic devices nearby such as water pumps, fans, compressors, motors or dynamos will induce electromagnetic interference to the light tube. Such electromagnetic interference may penetrate to the light source inside the light tube, resulting in blackening or burning of outer body and shocking the electronic elements or circuitry. The advantage of the protective circuitry is to prevent the above from happening. Unfortunately, conventional EMC circuitry with the electronic elements used are too large to be installed in the limited space of conventional light tubes.

SUMMARY OF INVENTION

[0004] To resolve the aforementioned problems, the present invention provides an alternate light tube. The light tube comprises an inner light source, an outer transparent body, a vacuum seal, a filter driver and a power connector. The outer transparent body comprises an inner layer and an outer layer of vacuum glass, the diameter thereof being at least 7mm and the length thereof being at least 60mm. An interlayer exists between the two layers of vacuum glass, the air pressure inside the interlayer being less than 11 - 1 Pa. In addition, the inner surface of the interlayer is coated with a low-radiation film.

[0005] In an embodiment of the present invention, air between the outer transparent body and the inner light source is completely drawn out and sealed by the vacuum seal, such that a vacuum state is formed between the outer transparent body and the inner light source. This can effectively prevent suspended particles from entering the outer transparent body through air which causes different natural problems such as frosting, fogging, dew condensation, dirt and dust accumulation, and resulting in the luminance output of the light tube being greatly reduced and the outlook being also affected.

[0006] In an embodiment of the present invention, the filter driver comprises two parts: driver and EMC filter. In light of the problem of limited space inside the light tube, the circuitry of the EMC filter is specifically designed to reduce the volume thereof. In another embodiment, the power connector is installed at the two opposite ends of the light tube, and they can both connect to power input and multiple light tubes can also be connected in series through the power connector.

BRIEF DESCRIPTION OF FIGURES

[0007] The function and advantages of the present invention can be more understood when described with reference to the accompanied drawings and the description. Same components are denoted by the same numeral. In some cases, subtag is added at the end of a tag and string to denote one of many similar elements. All similar elements are indicated when a tag is referred but a subtag is not specifically referred to.

[0008] Figs. 1A-B show schematic diagrams of an EMC filter installed inside an outer transparent body, according to an embodiment of the present invention, wherein fig. 1 A is an assembled diagram and fig. IB is an exploded diagram.

[0009] Figs. 2A-B shows a schematic diagram of an EMC filter installed outside an outer transparent body, according to an embodiment of the present invention, wherein fig. 2A is an assembled diagram and fig. 2B is an exploded diagram.

[0010] Fig. 3 shows a circuit diagram of a filter driver according to an embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0011] Referring to Figs. 1 A-1B, according to an embodiment of the present invention, a light tube comprises an inner light source 20, an outer transparent body 30, a vacuum seal 40, a filter driver 50 and power connector 60. Inner light source 20 uses Tl to T12 type fluorescent tube, cold cathode fluorescent tube (CCFL), light emitting diode (LED) or non-standard light source. The outer transparent body 30 comprises an inner and an outer layer of vacuum glass. The diameter of the vacuum glass material is at least 7mm and the length is at least 60mm. An interlayer exists between the two layers of vacuum glass. The air pressure inside the interlayer is less than 11 - 1 Pa. The inner surfaces of the interlayer are coated with a low-radiation film to reduce heat conduction by radiation. The outer transparent body 30 has the advantages such as being hard, high heat resistance, high wind load performance and good sound insulating properties. Therefore, the long-existing problems of frosting, fogging or dust accumulation can be effectively eliminated, and thus resulting in effectively increasing light distribution and reducing ultra-violet ray output. The ability to withstand high temperature can keep the operating temperature of the inner light source 20 constant and not easy to release to the environment through the outer transparent body 30, therefore increasing power-saving efficiency.

[0012] According to an embodiment of the present invention, the main material of the vacuum seal can be various plastic material or steel. The main function of the vacuum seal 40 is to seal up the outer transparent body 30 and the inner light source 20 after the air therebetween is completely drawn out, such that a vacuum state is formed. In an exemplary embodiment of the present invention, power connector 60 is installed at the two opposite ends of the light tube, the power connector 60 can both connect to the power inlet, and multiple light tubes can be connected in series through the power connector 60. [0013] Figs. 1A-1B are schematic diagrams of a filter driver installed inside the outer transparent body 30, according to an embodiment of the present invention. As shown in Figs. 1A-1B, the inner light source 20 is disposed inside the outer transparent body 30, and air therebetween is completely drawn out. The filter driver is then installed inside the outer transparent body 30 and sealed by the vacuum seal 40, such that a vacuum state is formed between the outer transparent body 30 and the light source 20. Lastly, the power connector 60 is installed at the two opposite ends of the light tube. [0014] According to another embodiment of the present invention, the filter driver 50 can be installed outside the outer transparent body 30 instead of inside. Figs.

2A-2B is a schematic diagram of the filter driver 50 installed outside the outer transparent body 30. Similarly, the light tube comprises the inner light source 20, the outer transparent body 30, vacuum seal 40, filter driver 50 and power connector 60. However, the inner light source 20 and the outer transparent body 30 are sealed by the vacuum seal 40 as soon as the air therebetween is completely drawn out. The filter driver 50 is installed at the two opposite ends of the outer transparent body 50 afterwards. Lastly, the power connector 60 is installed at the two opposite ends of the light tube.

[0015] According to a further embodiment of the present invention, the filter driver 50 comprises two parts: driver and EMC (Electromagnetic Compatibility) filter. In light of the limited space in a light tube, circuitry of the EMC filter is specifically designed to reduce its size, such that it can be installed in light tubes. Fig. 3 shows a circuit diagram of a filter driver 50 according to an embodiment of the present invention. As shown in Fig. 3, EMC filter circuitry 70 and driver circuitry 80 is connected together. Specifically designed circuitry not only can reduce the size of the filter driver 50, but can also increase luminance of the light tube by enlarging the light distribution surface of the inner light source 20. Furthermore, adding the EMC filter allows the light tube to resist the electromagnetic interference created by starting or operation of large electromagnetic devices nearby, such as water pumps, fans, compressors, motors or dynamos etc., therefore enhancing the safety and stability of the light tube.

[0016] The exemplary embodiments of the present invention are thus fully described. Although the description referred to particular embodiments, it will be clear to one skilled in the art that the present invention may be practiced with variation of these specific details. Hence this invention should not be construed as limited to the embodiments set forth herein.

[0017] For example, the shape of the inner light source 20 and the outer transparent body 30 is not limited to circular, but can also be rectangular, ellipse or in other shapes. The vacuum seal 40 can be made using other materials to one skilled in the art. The filter driver 50 can be assembled using different elements. The luminance and color of the inner light source 20 are also not limited.