Electric lamp and discharge devices – With temperature modifier – Double wall – jacket or casing for envelope
Reexamination Certificate
1999-09-24
2001-09-18
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With temperature modifier
Double wall, jacket or casing for envelope
C313S026000, C313S238000, C313S631000, C313S268000, C313S623000, C313S634000, C313S017000
Reexamination Certificate
active
06291933
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a lamp, in particular metal halide discharge lamp having a protective sleeve surrounding an arc tube, wherein the sleeve and the arc tube are supported by a metal frame mounted to the stem, and a glass envelope fixed to the stem surrounds the sleeve.
Metal halide lamps typically incorporate a tubular shield surrounding the pressurized arc tube to absorb the impact of dispersing shards in the event the arc tube fractures. Both the shield and the arc tube are supported by a metal frame mounted to the stem, which frame is electrically isolated from the leads for the arc tube. This is especially important for high wattage lamps. Since current carrying members in proximity to the arc tube can cause sodium loss, it is preferable to electrically distance the current carriers from the lateral walls of the arc tube.
U.S. Pat. No. 6,153,968 discloses a metal halide lamp of the type described above, wherein an arc tube and the surrounding shield are supported by a metal frame mounted to the stem. The shield is a quartz sleeve whose ends are fitted with retaining rings which are welded to respective frame members on either side of the sleeve. The arc tube has pinched ends which extend beyond the sleeve. Each pinched end is fitted with a metal strap which is welded to the frame members. Current is supplied to the arc tube by a braided wire for the lower electrode and a flying lead well spaced from the arc tube for the upper electrode. The construction is especially suitable for a 1000 watt lamp.
The arrangement of the prior art requires two rings for mounting the sleeve and two straps for mounting the arc tube, which is four metal components requiring at least four welds for fixing to the frame members. Since the pinched ends of the arc tube extend beyond the protective sleeve, it is possible that shards of arc tube will impinge the outer envelope if the lamp fails.
U.S. Pat. No. 5,729,078 also discloses a discharge lamp wherein an arc tube and the surrounding shield are supported by a metal frame mounted to the stem. The frame is directly connected to leads in the stem. For high wattage lamps, which have larger components, this would place undue stress on the stem. Since the frame is not electrically isolated, sodium loss would be unacceptable in high wattage lamps. Further, the pinched ends of the arc tube still extend beyond the shield.
In order to reduce manufacturing costs in a lamp having an electrically floating frame, it would be preferable to reduce the number of parts and the number of welding steps. From a safety standpoint, it would also be preferable for the protective sleeve to extend beyond the ends of the arc tube.
SUMMARY OF THE INVENTION
According to the invention, the tubular sleeve is provided with a pair of diametrically opposed apertures adjacent to each end, each pair of apertures lying in the plane defined by a respective one of the pinched ends. An elongate U-clip formed of steel wire is received through each pair of apertures; each U-clip engages a pinched end of the arc tube inside the sleeve and the frame members outside the sleeve. The distal ends of each U-clip are welded to the respective frame member, thereby fixing the position of both the arc tube and the sleeve to the frame.
The only mounting hardware required for both the arc tube and the sleeve is two identical U-clips which are formed from steel wire. Since each clip may be fixed to the frame with a single weld, only two welding operations are required. Manufacturing costs are thus considerably reduced, as compared to the prior art.
Since the apertures for receiving the U-clips are spaced from the ends of the sleeve, the sleeve may extend beyond the pinched ends of the arc tube. In the event that the arc tube fails, this helps to assure that flying fragments will not hit the outer envelope and cause it to fracture.
These and further advantages will be apparent from the drawing and description which follow.
REFERENCES:
patent: 4281274 (1981-07-01), Bechard et al.
patent: 4580989 (1986-04-01), Fohl et al.
patent: 5079480 (1992-01-01), Canale et al.
patent: 5136204 (1992-08-01), Muzeroll et al.
patent: 5532543 (1996-07-01), Van Der Leeuw et al.
patent: 5729078 (1998-03-01), Pragt
Dombrowski Kevin S.
Gensert James M.
Intihar, Jr. Richard
Provagna Kevin D.
Halajian Dicran
Patel Nimeshkumar D.
Philips Electronics North America Corporation
Roy Sikha
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