This application is the national phase of international application PCT/JP99/05143 filed Sep. 21, 1999 which designated the U.S.
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.
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 40xc2x0 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 40xc2x0 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 xe2x80x9cLaw relative to rationalization of use of energyxe2x80x9d, 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.
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 the inner surface of the container by heating.
According to the present invention, it becomes possible to easily collect mercury to the cold spot formed at one end by utilizing the action of mercury adsorbing force of mercury left in the mercury emission body or the mercury emission body and thus, the startup of luminous flux becomes more fast and the lamp characteristic is stabilized more certainly.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the mercury emission body is characterized in that it is arranged at a point below one of the electrodes when the discharge lamp is mounted in a lighting device.
According to the present invention, the cold spot is formed at a point below the electrode where the mercury emission body is arranged at the time of horizontal lighting and therefore, it becomes possible to utilize the action of the mercury adsorbing force of the mercury emission body certainly when mercury is collected to the cold spot.
Further, the low-pressure mercury vapor discharge lamp of the present invention is characterized in that it is provided with a first and a second ring type containers which are mutually in different diameters and positioned in the concentric circle state on the same plane surface; a first and a second electrodes provided at one ends of the first and the second ring type containers; a bridge formed through a discharge space at a point away from the other ends of the first and the second ring type containers so that the electric discharge is taken place between the first and the second electrodes; a no discharge path formed area that is formed between the bridge and other ends of the ring type container; a mercury emission body filled in the ring type container so that it is arranged in this no discharge path formed area; and a base to cover a part of one end and the other end of the ring type container.
According to the present invention, it is possible to improve the lighting efficacy of a double ring type fluorescent lamp that is used mainly in a lighting device for house use and stabilize the lamp characteristic at the time of startup.
Further, the low-pressure mercury vapor discharge lamp of the present invention is characterized in that it is provided with a first and a second straight tubular containers that are provided parallel to each other, a first and a second electrodes provided at one end of these first and the second straight tubular containers, a bridge formed through a discharge space at a point away from the other ends of the first and the second straight tubular container so that an electric discharge is taken place between the first and the second electrodes, a no discharge path formed area that is formed between the bridge and the other end of the ring type container, a mercury emission body filled in the first or the second straight tubular container so as to be arranged in this no discharge path formed area, and a base to cover one end of a straight tubular container.
According to the present invention, it is possible to improve the lighting efficacy of a compact type fluorescent lamp that is used mainly for light devices for houses, facilities and shops and stabilize the lamp characteristic at the time of startup.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the mercury emission body is characterized in that it is a pellet shape alloy comprising mercury and at least one kind of a group of Bi, Zn, Sn, Pb, Ag, In, Cu and Sb.
According to the present invention, mercury can be filled in a container according to a relatively simple method. Further, depending on kind of alloy, mercury vapor pressure can be controlled to a desired characteristic.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the mercury emission body is characterized in that it is a porous pellet medium made of at least one kind out of a group comprising silica, alumina, titania, iron and glass, with mercury impregnated.
A porous medium that is an aggregated matter comprising electrolytic separated iron (Fe) that was obtained by immersing an iron electrode in mercury and hardened in a rod shape by applying the mechanical pressure is suited.
According to the present invention, mercury can be filled in a container according to a relatively simple method.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the mercury emission body is characterized in that its metallic substrate surface is coated with a titanium-mercury alloy.
For the mercury emission body referred to here, Commodity Name xe2x80x9cGEMEDISxe2x80x9d made by SAES Getters Inc., etc. are usable. By arranging this mercury emission body around the electrodes, it is possible to emit mercury by such a means as high frequency induction heating.
According to the present invention, mercury can be filled in a container according to a relatively simple method.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the mercury emission body is characterized in that it is a capsule containing mercury in the readily emitting state.
According to the present invention, mercury can be filled in a container according to a relatively simple method.
Further, in the low-pressure mercury vapor discharge lamp of the present invention, the airtight container is characterized in that a fluorescent membrane is formed therein and lights at a inner wall load of lamp bulb 500 W/m2 or above.
Already known various fluorescent materials are usable for the fluorescent membrane and for instance, halo-phosphate phosphor, three wavelength luminescence type rare earth metal phosphor, etc. are usable for fluorescent lamps for general use. In addition, needless to say, any fluorescent materials are usable according to use and grade of fluorescent lamps.
The definition of the inner wall load of lamp bulb is the lamp input electric power per surface area of the inner surface of a container opposing an electric discharge path and the inner surface of a container at the portion wherein no discharge path is formed is excluded.
According to the low-pressure mercury vapor discharge lamp of the present invention, it is possible to provide a high load type fluorescent lamp having the fast startup of luminous flux and the stabilized lamp characteristic.
Further, the low-pressure mercury vapor discharge lamp is characterized in that the length of the mercury diffusion route from the cold spot formed in the container to the end of the container most far away therefrom is more than 400 mm, an amount of filled mercury for each mercury diffusion route is less than 6 mg within the range of length of the mercury diffusion route 400-500 mm and when the length of the mercury diffusion route is more than 500 mm, the relationship of Mxe2x89xa62800/S is satisfied, where S is a surface area of the bulb (cm2) and M is a filled amount of mercury for each mercury diffusion route (mg)
The reason for why a time is required for mercury to collect to the cold spot formed in the container relates to a filling amount of mercury was described in the above. Here, it is found that the upper limit value of this filling amount of mercury is depending on the length of the mercury diffusion route and the inner surface area of the container. In other words, the movement of mercury is a phenomenon of mercury vapor being diffused to a low vapor pressure area in the container. If the mercury diffusion route of a container is long, a time needed for excess mercury to move becomes long and therefore, an amount of mercury to be fill must be adjusted according to a length of the mercury diffusion route. Further, if a diameter of a container is small and its length is long, it is hard for mercury vapor to diffuse and therefore, an upper limit of a mercury filling amount in inverse proportion to an inner surface area calculated from a diameter and a length of a container is demanded.
When the startup stability characteristic was measured by the inventor by varying a filling amount of mercury of various low-pressure mercury vapor discharge lamps, it was confirmed that a numerical value obtained by dividing an coefficient of correction 2800 with an inner surface area S (cm2) of a container can be stipulated for a mercury filling amount M (mg). However, there is an exception; that is, when the length of the mercury diffusion route is within a range of 400-500 mm, readiness of diffusion of mercury vapor is satisfactory at around the upper limit value of the mercury filling amount obtained from the relationship between the coefficient of correction and the inner surface area S; however, amount of mercury becomes rather excess against the capacity of a container and an adverse effect to the discharge with the movement of granulated mercury when the blackening is generated by excess mercury and vibration is applied is considered and therefore, it is necessary to stipulate a mercury filling amount to be below an absolute amount. It was confirmed by the tests that these defects would not be generated when a mercury filling amount is below 6 mg within the range of the length of the mercury diffusion route is 400-500 mm. Further, it was also confirmed that in case of the discharge lamps of which mercury diffusion route lengths are less than 400 mm, if mercury in amount (preferred 5 mg or less) less than that of liquid mercury filled through the mercury emission body, the startup stability characteristic is satisfied and the defects mentioned above also would not be generated.
Further, the mercury diffusion route means a route from one end to the other end of a container when the cold spot is formed at one end of a tubular container and means a route from the cold spot to a pair of ends (more than 2 ends according to a shape) of a tubular container when the cold spot is formed at the intermediate region, for instance, a non discharge path formed area of a tubular container. Accordingly, when the cold spot is formed at an intermediate region such as the no discharge path formed area of a tubular container, there are more than one mercury diffusion routes and an added value of values obtained for mercury diffusion routes is defined to be an upper limit value of the mercury filling amount. An inner surface area S in this case is also not that of the entire container but is calculated from a part of inner surface area of a container opposing each mercury diffusion route.
According to the present invention, it is possible to optimize amount of mercury filled in a low-pressure mercury vapor discharge lamp having a length of the mercury diffusion route more than 400 mm.
Further, a lighting system of the present invention comprises the low-pressure mercury vapor discharge lamp described in the above invention, a lighting system to stably light up this low-pressure mercury vapor discharge lamp, and a main body of the lighting system to house the low-pressure mercury vapor discharge lamp and the lighting system.
According to the present invention, it is able to provide a lighting system equipped with the low-pressure mercury vapor discharge lamp of the invention described above.
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