Patent Application
20110298356
The present disclosure relates generally to a low pressure mercury vapor discharge lamp and more particularly to a compact fluorescent lamp including an amalgam for emitting mercury vapor during at least a starting period.
A wide variety of low-pressure discharge lamps are known in the art. These lamps contain small doses of mercury which radiates under the influence of a discharge arc. The mercury may be introduced into a discharge space of the lamp in a number of ways. One possible method is the introduction of an amalgam, typically containing bismuth, e.g., a bismuth-indium-mercury compound. The mercury necessary for the operation of the lamp is released from the amalgam. A cold spot is responsible for the mercury pressure. Other methods of releasing mercury for operation of the lamp include liquid or pellet forms. During operation the mercury “leaves the pellet” with the liquid form working similarly. The liquid and pellet forms are positioned in the arc tube while the amalgam is optimally positioned in the exhaust tube close to the heat of the cathode as its operating temperature is much higher than the liquid or pellet forms. This results in a slow warm-up of the lamp because the amalgam must reach a much higher temperature from room temperature compared to the cold spot for the liquid and pellet forms. The amalgam is positioned in the arc tube in a defined position while the pellet and liquid mercury forms usually move freely in the arc tube.
Discharge lamps employing an amalgam optimized for use in high temperature areas have the disadvantage of a longer start-up period than lamps using pure liquid mercury. The length of the start-up period is dependent on the speed at which mercury vapor pressure in the lamp increases because the lumen output of the lamp is dependent on the mercury vapor pressure. The start-up period is longer for amalgam containing lamps since the mercury pressure is too low at lower temperatures usually present at start-up, typically in the range of 0° C. to about 50° C. The mercury vapor increases slowly, not reaching a desired level until the amalgam reaches higher temperatures. In contrast, the mercury vapor pressure of a liquid mercury dosed lamp is much higher than the mercury vapor pressure of the amalgam containing lamp at the lower temperatures or at room temperature.
The amalgam which controls the mercury vapor pressure during lamp operation, except for the start-up period, is typically called the main amalgam. In contrast, the auxiliary amalgam influences the mercury vapor during the start-up period. That is, in order to improve start-up characteristics in an amalgam containing lamp, an auxiliary amalgam is typically attached to each cathode stem. Therefore, the auxiliary amalgam emits mercury during the start-up period. The auxiliary amalgam is heated by the cathode after ignition and emits mercury to make up for the lack of mercury vapor during the start-up period. A typical auxiliary amalgam is indium-mercury (In-Hg).
Amalgams containing low pressure mercury vapor discharge lamps have experienced varying degrees of success. Thus, a need exists for an improved low-pressure mercury vapor discharge lamp.
In an exemplary embodiment, a compact fluorescent lamp includes a discharge tube having cathodes disposed adjacent opposite ends. A fill gas is disposed within the discharge tube. The lamp further includes an auxiliary amalgam located in the discharge tube and dispersed in the arc to be heated thereby for emitting mercury vapor during at least a starting period.
In an exemplary embodiment, a low-pressure mercury vapor discharge lamp includes a sealed envelope having an interior surface to form a discharge tube. A fill gas including mercury is disposed within the discharge tube. The lamp further includes a continuous arc path with cathodes disposed at each end of the arc path. An auxiliary amalgam is located in the sealed envelope between the cathodes and dispersed in the arc to be heated thereby for emitting mercury vapor during at least a starting period.
A method of positioning an amalgam in a compact fluorescent lamp includes providing a sealed discharge tube having cathodes disposed at each end thereof. The method further includes disposing a fill gas which includes mercury within the discharge tube. The method further includes locating an auxiliary amalgam in the discharge tube between the cathodes and dispersed in the arc to be heated thereby for emitting mercury vapor during at least a starting period.
A compact fluorescent lamp includes a sealed discharge tube filled with a fill gas including mercury, A phosphor coating is disposed on an inner surface of the tube. The lamp further includes cathodes disposed at each end, forming a continuous arc path therebetween. The lamp further includes an auxiliary amalgam located in the sealed envelope between the cathodes and dispersed in the arc to be heated thereby for emitting mercury during at least a starting period.
In an exemplary embodiment, the auxiliary amalgam is a generally planar wire mesh member.
In another exemplar embodiment, the wire mesh member is a spring-like component.
The improved compact fluorescent lamp with decreased warm-up time is provided.
A primary benefit of the present disclosure is a positioning of an auxiliary amalgam in a fluorescent lamp.
Another benefit is an improved compact fluorescent lamp with decreased warm-up time during the service life of the lamp.
Still further advantages will become apparent of those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiment.
A gaseous discharge fill or fill gas is contained within the discharge chamber 104. The till gas typically includes an inert gas such as argon or a mixture of argon and other rare earth gases such as xenon, krypton, and neon at a low pressure often in combination with a small quantity of mercury to provide a desired low vapor pressure for operation of the lamp 100.
The discharge tube in one exemplary embodiment is preferably formed from four U-shaped tubes 108, 110, 112, 114 having generally circular cross sections, although the shapes and number of tubes may be varied without departing from the scope and intent of the present disclosure. The tubes 108, 110, 112, 114 each have generally parallel leg sections 116, 118 and a transverse bridging or light section 120 joining one end of each of the leg sections 116, 118. The opposite end of each of the leg sections 116, 118 is closed.
The tubes 108, 110, 112, 114 are in substantially parallel alignment. The tubes 108. 110, 112, 114 are oriented in the same direction such that the bridging section 120 of the tubes 108, 110, 112, 114 are at one end of the lamp 100 while the closed ends of the section 116, 118 are at the opposite end of the lamp 100. Adjacent leg sections 116 of adjacent tubes are joined by connecting conduits 122 which complete a convoluted and maximize a length of a generally elongate discharge path between cathodes 124 which are provided at the closed ends of two of the exterior leg sections.
The cathodes 124 are preferably of a filament coil type. Each cathode 124 is supported within the envelope 102 by a cathode support structure 126. The cathode support structure 126 includes a pair of electrical lead-in wires 128 connected to opposite ends of the cathodes to supply electrical energy to the cathodes 124 and an electrically insulated support 130 connecting and supporting electrical lead-in wires 128 below the 124. The electrical lead wires 128 extend through a stem 132 which is pinched or sealed to hermetically seal the envelope 102.
A main amalgam member 150 is provided within the sealed envelope 102, preferably located in the exhaust tube 138. Typically, the amalgam is a metal alloy such as an alloy containing a bismuth-indium-mercury (Bi-In-Hg) composition. The main amalgam may also contain tin, zinc, silver, gold and combinations thereof. The particular composition is chosen to be compatible with the operating temperature characteristic of the location in the envelope 102. As such, the alloy is generally ductile at temperatures of about 100° C. The alloy may become liquid at higher lamp operating temperatures. Once the working temperature is reached, the main amalgam 150 holds the correct mercury vapor pressure.
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The auxiliary amalgam member 250 controls the mercury vapor pressure during a starting period of the lamp. The auxiliary amalgam member 250 is heated by being located in the path of the arc discharge because it is disposed between cathodes in the arc discharge path and at an elevated temperature that emits mercury vapor during the starting period to increase the mercury vapor pressure in the discharge lamp and thereby improves warm up characteristics of the lamp 200. The auxiliary amalgam member 250 also absorbs mercury during a non-discharge period, i.e., when the temperature is reduced at the cathode in a non-discharge state. The generally planar wire mesh member 252 can vary in shape and size, while the support member 226 is preferably an elongated, flexible, spring-like component. This is in contrast to the auxiliary amalgam being located between a cathode and the associated mount as is generally done in the prior art.
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The disclosure has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the disclosure be construed as including all such modifications and alterations.
