Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Reexamination Certificate
1998-09-21
2001-02-27
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
C313S490000, C445S026000, C445S027000, C445S009000
Reexamination Certificate
active
06194827
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a low pressure mercury vapor discharge lamp using a mercury-releasing metal substrate as a method for providing mercury to a bulb and to a method for manufacturing the same.
BACKGROUND OF THE INVENTION
In a circular fluorescent lamp, mercury typically is provided to bulb, using a method of filling mercury in a bulb, a method of dropping and introducing liquid mercury into the bulb directly from an exhaust-pipe (vacuum-pipe) (hereinafter, “a dropper method” will be referred to). Since it is difficult to control the filling amount of mercury by the dropper method, a great amount of mercury has to be used so as to ensure the reliability of products. However, since mercury is a harmful substance for the environment, it is desirable to minimize the amount of mercury.
In order to reduce the amount of mercury, alternative methods to the dropper method have been considered. One such method includes filling only a required amount of mercury by providing a mercury-releasing metal substrate, for example, an alloy of zinc and mercury inside a bulb. However, in a case where the mercury-releasing metal substrate is merely put into the bulb, the mercury-releasing metal substrate moves freely inside the bulb. As a result, the mercury-releasing metal substrate makes noises or peels off an inner fluorescent film. To overcome this, the mercury-releasing metal substrate is adhered to the inside face of the bulb by bringing the mercury-releasing metal substrate into contact with a seal part of the end of the bulb and then heating the bulb from the outside.
As a method of heating the bulb from the outside, a method of heating by a furnace, burner, or the like, is employed. However, under the conventional heating conditions, the mercury-releasing metal substrate cannot be adhered or is insufficiently adhered to the bulb, so that the mercury-releasing metal substrate is often peeled off from the bulb.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a low pressure mercury vapor discharge lamp capable of firmly adhering a mercury-releasing substrate to the inside face of a bulb and a method for manufacturing such a low pressure mercury vapor discharge lamp.
According to the present invention, a low pressure mercury vapor discharge lamp comprises a bulb and a mercury-releasing metal substrate formed in the bulb. Herein, the mercury-releasing metal substrate has an inside part crystallized in a plate form or in a granular form and a surface on which a mercury-rich layer is formed.
It is preferable in the above-mentioned discharge lamp that the mercury-releasing metal substrate is an alloy of zinc and mercury.
It is preferable in the above-mentioned method that the content of mercury included in said alloy of zinc and mercury is in the range of 40 to 60 weight %. If the content of mercury is less than 40 weight %, the alloy is not adhered to the inside face of the bulb or only weakly adhered to the inside face of the bulb. Consequently, it is difficult to place the alloy one at a time in the process of manufacturing the low pressure mercury vapor discharge lamp.
It is preferable in the above-mentioned discharge lamp that the weight ratio of mercury to zinc is approximately 1:1.
It is preferable that the above-mentioned discharge lamp further comprises a flare part at the end of the bulb, and a cavity is formed at the junction between the bulb and the flare part, with the mercury-releasing metal substrate adhered to the cavity.
It is preferable in the above-mentioned discharge lamp that the mercury-releasing metal substrate is present in an amount of 0.02 to 0.028 mg per 1 cm
3
of space within the bulb.
It is preferable in the above-mentioned discharge lamp that plate crystals are formed inside the mercury-releasing metal substrate and granular crystals are formed on the surface of the mercury-releasing metal substrate.
It is preferable in the above-mentioned discharge lamp that the mercury-rich layer is partially formed on the surface of the mercury-releasing substrate.
Next, according to the present invention, the method for manufacturing the low pressure mercury vapor discharge lamp comprises the steps of putting a mercury-releasing metal substrate into a bulb; forming a mercury-rich layer on the surface of the mercury-releasing metal substrate while crystallizing the inside of the mercury-releasing metal substrate in a plate form or in a granular form by heating the bulb from the outside; and then softening the mercury-releasing metal substrate to adhere it to the inside face of the bulb.
It is preferable in the above-mentioned method that the mercury-releasing metal substrate is an alloy of zinc and mercury.
It is preferable in the above-mentioned method that the weight ratio of mercury to zinc is approximately 1:1.
It is preferable that the above-mentioned method comprises the steps of further providing a flare part at the end of the bulb; forming a cavity at the junction between the bulb and the flare part; and heating and softening the mercury-releasing metal substrate to adhere it to the cavity.
It is preferable in the above-mentioned method that mercury is seeps to the surface of crystals by heating to form the mercury-rich layer.
It is preferable in the above-mentioned method that the mercury-releasing metal substrate's surface is etched with acid.
It is preferable in the above-mentioned method that the mercury-releasing metal substrate is heated so that the graph describing the relationship between the heating time t (seconds) and the bulb temperature T (° C.) passes through a region defined by coordinates (0, 200), (60, 360), (120, 380), (80, 420), (40, 405), (10, 380) and (0, 300) before reaching a region defined by coordinates (120, 380), (240, 380), (210, 420), and (80, 420).
It is preferable in the above-mentioned method that the mercury-releasing metal substrate is heated so that the graph describing the relationship between the heating time t (seconds) and the bulb temperature T (° C.) passes through a region defined by coordinates (120, 200), (1020, 380), (90, 380), (60, 405), (10, 400), (0, 300), and (0, 200) before reaching a region defined by (1020, 380), (90, 380), (60, 405), (120, 420) and (1020, 420).
According to the present invention, a low pressure mercury vapor discharge lamp comprises a bulb and a mercury-releasing metal substrate formed in the bulb. Herein, the mercury-releasing metal substrate has an inside part crystallized in a plate form or in a granular form and a surface on which a mercury-rich layer is formed. Thus, the mercury-releasing metal substrate can be firmly adhered to the inside face of the bulb.
Furthermore, according to the present invention, the method for manufacturing a low pressure mercury vapor discharge lamp comprises the steps of putting a mercury-releasing metal substrate into a bulb; forming a mercury-rich layer on the surface of the mercury-releasing metal substrate while crystallizing the inside of the mercury-releasing metal substrate in a plate form or in a granular form by heating the bulb from the outside; and softening the mercury-releasing metal substrate to adhere it to the inside face of the bulb. Thus, the area in which the inside face of the bulb is in contact with the mercury-releasing metal substrate can be increased and the mercury-releasing metal substrate can be firmly adhered to the inside face of the bulb.
Furthermore, according to another method for manufacturing a mercury vapor discharge lamp of the present invention, a mercury-releasing metal substrate whose surface is etched with acid is used. Thus, heating conditions for adhering the mercury-releasing substrate to the inside face of the bulb can be relaxed.
REFERENCES:
patent: 4228715 (1980-10-01), Van Overveld et al.
patent: 5879216 (1999-03-01), Yoshii et al.
patent: 5882237 (1999-03-01), Sarver et al.
patent: 7-211235 (1995-08-01), None
patent: 9-45282 (1997-02-01), None
patent: WO 94-18692 (1994-08-01), None
Matsushita Electronics Corporation
Merchant & Gould P.C.
Patel Nimeshkumar D.
Williams Joseph
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