Low-pressure mercury vapor discharge lamp and illuminator

Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Discharge device load

Reexamination Certificate

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C315S063000, C313S489000, C313S483000, C313S635000

Reexamination Certificate

active

06337539

ABSTRACT:

This application is the national phase of international application PCT/JP99/05143 filed Sep. 21, 1999 which designated the U.S.
TECHNICAL FIELD
The present invention relates to a low-pressure mercury vapor discharge lamp equipped with a pair of electrodes arranged in different distances from both ends of an airtight container and a lighting system.
BACKGROUND ART
It is known that a low-pressure mercury vapor discharge lamp represented by a fluorescent lamp that lights at the most high efficiency when mercury vapor pressure in the bulb is about 0.8 Pa. The cold spot temperature of the bulb wall at this time is about 40° C.
On the other hand, a lamp that is lighting at a high atmospheric temperature or a lamp that has high inner wall load of the lamp bulb (input power per surface area of the bulb) is used at low efficiency because its temperature at the cold spot temperature of the bulb wall exceeds about 40° C. As a measure to improve efficiency of a lamp lighting at a high temperature of the cold spot, there is a method to fill amalgam, which is an alloy of mercury with other metal, in a bulb and lower mercury vapor pressure to about 0.8 Pa in the high temperature state. This method is adopted principally for compact self ballasted fluorescent lamp, etc.
However, there is such a problem that when amalgam is applied to ordinary fluorescent lamps, mercury vapor pressure drops too low when starting, in particular at a low temperature, and the startup of luminous flux becomes worse. As a measure to solve this problem, a method to improve lighting efficacy by forming a cold spot of a lamp bulb positively, lowering a temperature at one of the ends of the lamp, taking a large distance from one of the electrodes arranged at both ends of a lamp and filling pure mercury as disclosed in, for instance, Published Unexamined Japanese Patent Application No. 267501/1994 is known.
However, it was revealed that according to a method to make a distance from the end of one of the electrodes as before, the lamp characteristic including total luminous flux is not stabilized until mercury is collected to the cold spot that is formed at one of the ends.
Further, even if mercury was collected to the cold spot and the lamp characteristic was stabilized, mercury may move from the cold spot to other portion by a vibration applied to the lamp, etc. and the characteristic may be turned to the unstable state again.
In recent years, fluorescent lamps that are lighted with lighting efficiency above a certain level at a large lighting output in lighting devices that are used at a high ambient temperature are progressively developed, and this problem becomes important more and more as a result of the revision of “Law relative to rationalization of use of energy”, in March, 1999.
The present invention was made in view of the above-mentioned problem and it is an object to provide a low-pressure mercury vapor discharge lamp capable of improving the startup of luminous flux and reducing a time until lamp characteristic is stabilized and a lighting equipment.
DISCLOSURE OF INVENTION
A low-pressure mercury vapor discharge lamp comprises a translucent airtight container, a pair of electrodes filled in this airtight container at both ends and so arranged that a distance of one electrode from the end becomes longer than that of the other electrode, a mercury emission body filled in the airtight container, and discharging medium including mercury vapor discharged from the mercury emission body and inert gas.
Further, a translucent airtight container of the low-pressure mercury vapor discharge lamp of the present invention can be any tube provided that it is able to transmit ultraviolet rays or visible rays discharged from a fluorescent membrane formed in the airtight container and separate the discharge from the ambient atmosphere and envelope in the inside, and its material, shape and dimensions are not restricted. Generally, for reasons of environmental adaptability, economy and workability, soda lime glass is used in many cases. Further, for general lighting use, an airtight container in slender and tubular shape is used in many cases.
A hot-cathode equipped with a filament coil is normally used as an electrode. However, cold-cathode, ceramic electrode having electronic radiation material and any other materials are usable in this invention.
The electrodes are arranged at more than certain distance away from the ends supported by lead wires, etc. Lead wires supporting the electrodes may be filled in the container according to such a method as a pinch seal to directly fix the lead wires, etc. in addition to lead wires attached to flare stems or button stems attached to the ends of the container.
The arrangement of a pair of electrodes in different lengths from respective ends means a structure that the lengths between respective ends and the electrodes are made different to form the cold spot between the ends and the electrodes.
Mercury as a discharge medium can be filled in the form of pure mercury or amalgam. The filling method and amount of use can be according to a usual way. Normally, Argon (Ar) is used principally for inert gas. However, Neon (Ne), Krypton (Kr) and Xenon (Xe) can be used independently or in mix. The known range of filling pressure is applicable to inert gas.
The mercury emission body carries mercury before filling into the container and after filled, it is able to emit mercury into the container. Various methods, for instance, a means to make an alloy of mercury with other metals, a method to adsorb mercury in other materials physically or chemically, or a method to contain mercury in a small container in a size that can be filled in the container are considered for carrying mercury. However, any method is usable provided that mercury can be contained in a desired container.
Regarding a time required for mercury collected to the cold spot formed at one end, it was confirmed by experiments conducted by the inventor that it relates to an amount of mercury filled in the container. Further, it was also revealed that a phenomenon that mercury collected to the cold spot moves to other portion from the cold spot by vibration, etc. will appear when an amount of filled mercury is much and that mercury scarcely moves in case of a lamp with an amount of mercury filled needed only for lighting and does not affect the lamp characteristic. In other words, a time for excess mercury in the container to be collected to the cold spot is delayed and mercury moves to other place from the cold spot.
According to the present invention, the cold spot is formed at one end and mercury is filled by the mercury emission body and therefore, almost no excess mercury exists in the container, luminous flux starts up fast, mercury collected to the cold spot scarcely moves to other portions, and the lamp characteristic is stabilized.
Further, the startup of luminous flux referred to here does not imply such a temporary rise of luminous flux that luminous flux once rises after lighting a lamp, mercury vapor pressure also rises continuously while exceeding the maximum efficacy with subsequent temperature rise and luminous flux drops but it indicates the stable startup of luminous flux in a short time.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the airtight container is characterized in that it is in a ring type.
According to the present invention, it is possible to improve lighting efficacy of a ring type fluorescent lamp that is used mainly in a house lighting device and stabilize the lamp characteristic at the time of startup.
Further, in the low-pressure mercury vapor discharge lamp, the mercury emission body is characterized in that it is arranged at one electrode side.
Although a method to arrange the mercury emission body is not specially restricted, such methods as to house it in a thin tube arranged at one electrode side, to fix it with such a member as glass, etc. are enumerated. When the mercury emission body is of heating and fusing type, it may be fixed at a desired point on t

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