Electric lamp and discharge devices – With luminescent solid or liquid material – With gaseous discharge medium
Patent
1993-11-19
1999-11-09
O'Shea, Sandra
Electric lamp and discharge devices
With luminescent solid or liquid material
With gaseous discharge medium
H01J 162
Patent
active
059820896
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a low-pressure mercury discharge lamp which comprises an elongate tubular lamp vessel which is sealed in a vacuumtight manner, which extends in a meander shape parallel to a flat plane, which has an inner surface coated with a fluorescent powder, and which is provided with a lamp filling comprising a rare gas and mercury and with cold electrodes between which a discharge path extends. The invention further relates to an illumination panel, in particular an illumination panel destined for a liquid crystal display, provided with such a low-pressure mercury discharge lamp.
Such a lamp is known from a brochure of the Harison Electric Co, Ltd. The lamp described therein is recommended for use in an illumination panel for liquid crystal displays. The lamp has an external diameter of 6.2 mm (internal diameter approximately 4.3 mm) and the length of the discharge path is approximately 500 mm. This lamp is bent into a meander shape, i.e. the lamp vessel comprises a number of substantially parallel legs which are connected in series with one another and whose centrelines lie in a flat plane. The known lamp is suitable for being incorporated in an illumination panel for a 6" display screen and results in a smaller constructional height of this panel than is possible with similar bent fluorescent lamps of greater lamp diameter. The operating voltage specified for the known lamp is 530 V and the lamp current is no more than 6.0 mA, which is interesting for the use in portable equipment powered by batteries.
The known lamp is not suitable for larger displays of a similar comparatively small constructional height of the panel. To obtain an even illumination of a greater surface area, one would have to have recourse to a number of lamps of the kind described, so that a number of independent discharge paths would be created. An increase in the number of lamps leads to a proportional increase in the electrode losses, which is a disadvantage in a liquid crystal display unit which is often a portable one provided with a battery system. Moreover, an even illumination of the panel cannot be guaranteed in the case of independently arranged lamps because small differences in brightness between the lamps cannot be avoided in practice.
SUMMARY OF THE INVENTION
The invention has for its object to provide lamps with which illumination panels can be obtained having a very favourable power consumption coupled to a very even surface illumination and a small constructional height.
According to the invention, a low-pressure mercury discharge lamp of the kind mentioned in the opening paragraph is characterized in that the length of the discharge path is at least 250 times and at most 1000 times the internal diameter of the lamp vessel. This geometry involving a comparatively long discharge path in relation to the internal diameter leads to a lamp whose electrode losses are comparatively low, i.e. a greater portion of the power supplied becomes available for the gas discharge. It is also possible now to choose a lamp shape in which the lamp has a comparatively large number of legs situated next to one another, whereby a more unifom light distribution is obtained.
The ratio of the discharge path length to the internal lamp vessel diameter indicated above, which must be at least 250 in order to obtain the envisaged effect, is found to have a maximum value of 1000; it was in fact found that impractically high values for the operating voltage of the lamp are required when this upper limit is exceeded.
In an advantageous embodiment of a low-pressure mercury discharge lamp according to the invention, in which the meander-shaped discharge vessel comprises a number of straight, mutually substantially parallel legs, the internal diameter of the lamp vessel is at least 2.0 and at most 3.5 mm, and is preferably 2.5 mm, and the free distance between the legs is at least equal to and at most 5 times the internal diameter of the lamp vessel. This lamp has the advantage that a very uniform surface i
REFERENCES:
patent: 2433218 (1947-12-01), Herzog
patent: 3937998 (1976-02-01), Verstegen et al.
patent: 4559470 (1985-12-01), Murakami et al.
patent: 4743799 (1988-05-01), Loy
patent: 4798768 (1989-01-01), Oversluizen et al.
patent: 4842378 (1989-06-01), Flasck et al.
patent: 4920298 (1990-04-01), Hinotani et al.
patent: 5004948 (1991-04-01), Kinczel et al.
patent: 5041762 (1991-08-01), Hartai
patent: 5043627 (1991-08-01), Fox
patent: 5220249 (1993-06-01), Tsukada
patent: 5239238 (1993-08-01), Bergervoet et al.
patent: 5281448 (1994-01-01), Altena et al.
Brochure--Harison Electric Co., Ltd., pp. 1-6, No Date.
Ligthart Franciscus A. S.
Wesselink Gustaaf A.
Faller F. Brice
O'shea Sandra
U.S. Philips Corporation
LandOfFree
Low-pressure mercury discharge meander lamp dimensioned for even does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low-pressure mercury discharge meander lamp dimensioned for even, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-pressure mercury discharge meander lamp dimensioned for even will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1460771