Electric lamp and discharge devices – With optical device or special ray transmissive envelope – Reflector
Reexamination Certificate
2000-05-30
2002-06-11
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With optical device or special ray transmissive envelope
Reflector
C313S573000, C313S578000, C313S634000, C362S310000, C362S341000
Reexamination Certificate
active
06404112
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an electric lamp/reflector unit comprising
a reflector body including a reflector portion having a concave reflecting surface with an optical axis and, integral therewith, a hollow neck-shaped portion about the optical axis,
and an electric lamp provided with a gastight light-transmitting lamp vessel
and comprising a quartz-glass wall which encloses a cavity of a predetermined, in general, spherical or elliptic shape with a geometric center, said wall being at least partly provided with an infrared-reflecting and visible light-transmitting coating, and said cavity accommodating a, substantially, linear electric light source,
and said lamp also comprising a metal foil which is entirely embedded in the wall and connected to the electric light source,
and comprising a first end portion and a second end portion which are arranged so as to be opposite to each other and which both comprise a seal, through which seals a respective current conductor, which is connected to the embedded metal foil, issues from the lamp vessel to the exterior.
The invention further relates to an electric lamp for use in an electric lamp/reflector unit.
Such electric lamp/reflector units are used as a source of white light for general and decorative lighting applications.
BACKGROUND OF THE INVENTION
An electric lamp/reflector unit of the type mentioned in the opening paragraph is known from EP-A 0 397 422. In said document a description is given of a so-called double-ended halogen lamp provided with an infrared-reflecting interference filter, which lamp is arranged in a reflector body of the PAR
38
type, where the abbreviation PAR stands for Parabolic Aluminium Reflector, and the number “38” indicates a diameter of the reflector body at the location of the light emission window, the diameter being obtained by multiplying said number with an eighth of an inch, 1 inch being 25.4 mm, so that the diameter of the emission window of a PAR
38
reflector is 38×⅛ inch≈121 mm. It is an object of the inventors to enable such a double-ended halogen lamp to be fitted also in known PAR reflector bodies of a smaller physical size, for example in a PAR
20
reflector body having a diameter of the emission window of 20×⅛ inch≈63.5 mm, and, particularly, in a PAR
16
reflector body having a diameter of the emission window of 16×⅛ inch≈51 mm. An alternative embodiment of the reflector body is referred to as MR
16
(“metal reflector”), which, in comparison with a PAR reflector body having a corresponding diameter indication, has a neck-shaped portion which, viewed along the optical axis, is much shorter.
In order to bring about a satisfactory ratio between the reflector body and the double-ended electric (halogen) lamp, it is desirable to reduce the dimensions of the known electric lamp; however, this causes the temperature balance of such a miniaturized electric lamp to be adversely affected. In general, such an adversely affected temperature balance has a negative effect on the service life of the electric lamp in the electric lamp/reflector unit.
SUMMARY OF THE INVENTION
It is an object of the invention to adapt the dimensions of the electric lamp so as to make the electric lamp suitable for use in reflector bodies whose dimensions are smaller than the dimensions of the known electric lamp/reflector unit, and said adaptations also obviating the above drawbacks.
To achieve this, the electric lamp/reflector unit is characterized in accordance with the invention in that
the electric lamp is arranged in the reflector body in such a manner that the first end portion is at least partly situated in the neck-shaped portion, the cavity is situated within the reflecting portion and the electric light source is predominantly situated on the optical axis,
and in that the ratio of the distance d
c
I
;d
c
II
from the connection point where the current conductor is connected to the metal foil to the length l
ep
I
;l
ep
II
of the first and the second end portion lies in the range d
c
I
/l
ep
II
≧0.75 and d
c
I
;l
ep
II
≧0.75, the distance d
c
I
;d
c
II
and the length l
ep
I
;l
ep
II
being measured with respect to the geometric center of the lamp vessel.
By arranging one of the end portions of the electric lamp at least partly in the neck portion of the reflector body, it is achieved, viewed along the optical axis, to reduce the relative height of the electric lamp with respect to the reflector body, which has a favorable influence on the ratio of the dimensions of the double-ended electric lamp with respect to the dimension of the reflector body of the known electric lamp/reflector unit. In the known electric lamp/reflector unit, a double-ended halogen lamp is bodily arranged in the reflector portion of the reflector body by means of so-called mounting legs. By securing, in accordance with the invention, the first end portion of the electric lamp in the neck portion of the reflector body, a sturdy and reliable connection of the electric lamp with the reflector body is achieved. In addition, the positioning of the electric light source on the optical axis of the reflector portion is improved thereby, the electric light source preferably being positioned such that the geometric center of the electric lamp is situated in the focus of the concave reflecting surface. The improved positionability results in a higher light output and a better light distribution of the electric lamp/reflector unit.
The inventors have recognized that the miniaturization of the electric lamp, which makes it possible and attractive to fit said lamp in a reflector body having much smaller dimensions than the dimensions of the known electric lamp/reflector unit, causes, in particular, the so-called pinch temperature of the electric lamp to increase, which adversely affects, in particular, the service life of the electric lamp. The temperature of the pinch of a lamp is measured at the location of the connection point (generally formed by a welded joint) of the (external) current conductor and the metal foil embedded in the wall of the electric lamp. In general, a high pinch temperature enhances corrosion of the metal foil and/or the external current conductor. Corrosion leads to failure of the lamp as a result of the current supply being interrupted. Other causes of failure include, for example, leakage of the lamp vessel or explosion of the lamp. If in the electric lamp in accordance with the invention, the connection point between the metal foil and the external current conductor is positioned as faraway from the heat source (the electric lamp) as possible, a reduction of the pinch temperature is obtained.
Experiments have shown that a lower limit of d
c
I
/l
ep
I
=0.75 and d
c
II
;l
ep
II
=0.75 is desirable, in spite of the fact that the pinch temperature of the electric lamp in the electric lamp/reflector unit in accordance with the invention is higher than the pinch temperature of the known electric lamp/reflector unit, in order to achieve that the service life of the electric lamp in the electric lamp/reflector unit in accordance with the invention is at least comparable to the service life of the known electric lamp/reflector unit.
Preferably, the ratio of the distance d
c
I
;d
c
II
to the length l
ep
I
;l
ep
II
lies in the range 0.8≦d
c
I
/l
ep
I
≦0.95 and 0.8≦d
c
II
/l
ep
II
≦0.95. A lower limit of d
c
I
/l
ep
I
=0.8 and d
c
II
;l
ep
II
=0.8 causes the service life of the electric lamp in the electric lamp/reflector unit in accordance with the invention to be longer than the service life of the known electric lamp/reflector unit. An upper limit of d
c
I
/l
ep
I
=0.95 and d
c
II
/l
ep
II
=0.95 has the advantage that the part of the end portion situated between the connection point and the end of the end portion gives sufficient mechanical support to the (external) current conductor during the service life of the electric lamp. As a result, the risk that the current conductor breaks off during th
Frings Hubert
Kaulen Franz Herbert
Kreus Herbert Heinrich
Halajian Dicran
Koninklijke Philips Electronics , N.V.
Patel Ashok
LandOfFree
Electric lamp/reflector unit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Electric lamp/reflector unit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric lamp/reflector unit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2970945