EP2166282A1

EP2166282A1 - Unit of lamp and reflector

Info

Publication number: EP2166282A1
Application number: EP08164660A
Authority: EP
Inventors: designation of the inventor has not yet been filed The
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2008-09-19
Filing date: 2008-09-19
Publication date: 2010-03-24
Also published as: WO2010032180A1

Abstract

A unit of a lamp (10) and reflector in which the lamp is fixed with its first seal (14) in a neck shaped portion (5) of a reflector body (1). The neck shaped portion at its rear end is provided with a ceramic lamp cap (20). A ring (58) is provided around the first seal for counteracting cement (19) to flow from the neck shaped portion into the reflective portion (2) during manufacturing of the unit.
A spiral is provided around the first seal which spiral exerts resilient pressure on the ring towards the ceramic lamp cap, thus keeping the ring in position. When made of electrically conducting material, the spiral simultaneously functions as an external antenna (35).

Description

FIELD OF THE INVENTION

This invention relates to a unit of a lamp and a reflector. The unit comprising:

a reflector body provided with a reflective portion with a concave reflective surface and defining an optical axis, and as an integral part of the reflector body provided with a neck shaped portion surrounding with an opening the optical axis,
an electric discharge lamp provided with a lamp vessel having a gastight discharge space in which an electric element is arranged on the optical axis, the discharge space being closed by a first and a second, mutually opposed seals through which first and second seal respectively a first and a second electric current conductor extend from the electric element to the exterior;
a ceramic lamp cap fixed to a side of the neck shaped portion facing away from the reflective portion and surrounding with a hole opening the optical axis, the lamp cap being provided with at least one electrical contact to which at least one current conductor is electrically connected;
the lamp vessel being fixed with cement in the neck shaped portion via its first seal and with the discharge space in the reflective portion,
a ring is provided around the first seal for counteracting an adhesive compound to flow from the neck shaped portion into the reflective portion during manufacturing of the unit.

BACKGROUND OF THE INVENTION

Such a unit is known from EP-595412 . Units of this type may be used for projection purposes, for example, film or slide projection, but also in projection TV devices. If the light generated by the lamp is to be efficiently used, it is necessary to have a clean, reflective surface that is as large as possible. In particular this applies for a most relevant part of the reflective surface which is located relatively close to the electric element, being the reflective surface close to the neck shaped portion. During a manufacturing fixation step the lamp vessel is fixed in the neck shaped portion of the reflector body with an adhesive compound, for example cement. During said fixation step and if no counteractive measures are taken, there is a large risk that cement flows from the neck shaped portion onto the reflective surface located close to the neck shaped portion, thus reducing the size of the most relevant part of the reflective surface. Furthermore, if the cement flows too far over a part of the first seal, i.e. that part of the first seal which is located in the reflective portion, there is an increased risk on explosion of the lamp. To counteract these risks in the known unit, a ring is provided which narrows the opening of the neck shaped portion for a significant part at a transition area where the neck shaped portion merges into the reflective portion. Said ring is held in position by an internally narrowed portion of the neck shaped portion adjacent the transition area. It is a drawback of the known unit that manufacturing of the reflector is rather complicated because of the narrowed portion in the neck shaped portion. It is a further drawback that provision of an antenna to facilitate (re-) ignition of the lamp in the known unit is relatively complicated to realize as both the cavity and the antenna, which should be around the cavity, are located inside the cement.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a unit of the kind described in the opening paragraph in which at least one of the abovementioned drawbacks is counteracted. Thereto the unit is characterized in that the hole opening of the ceramic lamp cap is narrower than the opening in the neck shaped portion for the ceramic lamp cap to function as a seat for the ring. During the manufacturing process, in particular during positioning of the lamp in the neck and fixation of said lamp by the adhesive compound, for example by cement, the ring may temporarily be kept in position until the adhesive compound has hardened and does not readily flow anymore. The ring narrows a passage from the lamp cap to the neck shaped portion and thus to the reflective portion, so that the passage is blocked for a readily flowing mass like the adhesive compound. Thus reduction of the reflective surface, in particular of its most relevant part, and efficiency of the unit due to flow of the adhesive compound onto the reflective surface, is counteracted. Furthermore, as the flow of the adhesive compound is counteracted, the risk on presence of adhesive compound on the first seal is reduced, hence the risk on explosion of the lamp vessel is reduced as well. Finally, manufacture of the reflector body is simplified as special manufacturing steps to obtain the internal narrowed portion in the neck of the known reflector body are no longer required. The ring preferably is made from heat resistant material, for example hard glass, quartz glass, stainless steel, or, for example, heat resistant foil (Kapton).
In another embodiment, a kind of automatic positioning of the ring may be realized. Thereto the unit is characterized in that the first seal has a first and a second sealed portion between which a cavity is present and in that the first seal has a widening portion at the location of the cavity, the ring having only limited freedom in axial direction in between the widening portion and the ceramic cap. By keeping the lamp positioned in the reflective portion, the ring practically automatically is kept in position as well. In a preferred embodiment, the unit is characterized in that the ring is positioned adjacent the widening portion and thus that an opening in the ring through which the first seal extends, is practically closed by the widening portion. Thus a further reduction in the risk of flow of adhesive compound onto the reflective surface is attained.
Alternatively and/or additionally to the abovementioned automatic positioning of the ring, the unit is characterized in that a spiral is provided around the first seal which spiral exerts resilient pressure on the ring in an axial direction towards the ceramic lamp cap due to the ring being jammed in between the ceramic lamp cap and w all of the discharge space of the lamp vessel. The spiral can be made of any resilient, high temperature resistant material, i.e. high temperature means temperatures in the range of 300° to about 600° C, for example high temperature resistant metal like for example molybdenum, tungsten, kanthal, chromium, tantalum etc., or hard/quartz glass fibers. Preferably, the unit has a construction wherein the spiral is made of electrically conducting material and simultaneously functions as an external antenna. The antenna facilitates the (re-) igniting of the lamp. This construction offers the advantage that both the function of fixation of the ring and antenna are combined into one constructive part. For optimal functioning as an antenna, the spiral should be located least at the location of the cavity.
In another preferred embodiment the unit is characterized in that the antenna is electrically connected to the second current conductor. A passive serial antenna with a simple structure, which is easy to provide, and with a very reliable operation is thus realized.
The electric element may be an incandescent body, for example in an inert gas comprising a halogen, or a pair of electrodes in an ionizable gas. In an alternative embodiment of the unit the current conductor is passed from the second end portion through the reflective portion to the exterior and is connected there to a contact member. The two contact members may then be at a comparatively large distance from one another, so that the risk of flash-over between these members is very small.
A preferred embodiment of the unit is characterized in that the hole opening in the ceramic lamp cap has a stepped profile in which a first part of the hole opening adjacent the neck shaped portion has a diameter D_l which is larger than an inner diameter D_r of the opening in the neck shaped portion, while a second part of the hole opening remote from the neck shaped portion has a diameter D_s which is smaller than the diameter D_r of the opening in the neck shaped portion. This renders the unit to have the advantage of an increase in the most relevant part of the reflective surface of the reflective portion as it is enabled for the neck shaped portion of the reflector body to have a relatively small inner diameter. For autopositioning of the ring in axial direction, the ring preferably is clamped in between the stepped profile of the ceramic lamp cap and the neck shaped portion of the reflector body. Manufacturing of the unit is thus simplified.
In a unit comprising an electric discharge lamp, for example a high-pressure discharge lamp, for example a lamp having a filling comprising rare gas and metal halides, or a lamp having a filling of rare gas, mercury and halogen, and with a very high operational pressure, for example a pressure of approximately 200 bar or more, it is favorable when the reflector has means at its exterior for accommodating a low-voltage/high-voltage converter, for example, a recess suitable for this purpose. Conductors carrying a high voltage may then be very short. Further it is convenient when the reflector is closed off by a transparent plate, which is then provided at a light exit window opposite to the neck portion and transverse to the optical axis. It can be prevented thereby that flammable objects come into contact with hot portions of the lamp. The risk involved in an explosion of the lamp vessel can also be reduced by this.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the unit of electric lamp and reflector according to the invention are shown in the drawing, in which:

Fig. 1 shows a prior art unit in axial section,
Fig. 2 shows in axial section an embodiment of the unit according to the invention, and
Fig. 3 shows a detail of another embodiment of the first seal in the neck of the reflector in axial section;
Fig. 4 shows a detail of another embodiment of the unit of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In Fig. 1, the unit of electric lamp and reflector has a reflector body 1 which is provided with a reflective portion 2 with a reflective surface 3 with an optical axis 4, and integral therewith a hollow neck-shaped portion 5 surrounding the optical axis. The unit also comprises an electric lamp 10 which is provided with a light-transmitting lamp vessel 11, which is sealed in a gastight manner and has a discharge space 12 in which an electric element 13 is arranged. The lamp vessel has a first 14 and a second 15 end portion with a respective seal. The electric lamp 10 is fixed in the reflector body 1 by means of cement 19. The neck-shaped portion 5 internally has a narrowed portion 6 which merges into the reflective surface 3. A ring 58 is provided adjacent the narrowed portion 6 and around the first end portion 14 of the electric lamp 10 inside the neck-shaped portion 5 of the reflector body 1. The ring rests against the narrowed portion 6 of the neck-shaped portion 5 and surrounds the first end portion with small clearance.
In Fig. 2, the unit of electric lamp and reflector has a moulded reflector body 1 which is provided with a reflective portion 2 with a concave, for example, paraboloidically curved reflective surface 3 defining an optical axis 4, and integral with the reflective portion a hollow neck-shaped portion 5 surrounding the optical axis. In an alternative embodiment, however, this surface may be curved, for example, ellipsoidically. In the drawing, the reflector body is made of glass and has a metal layer, for example an aluminum layer, serving as a mirror. Alternatively, however, the reflector body may be made of, for example, glass-ceramic, ceramic, metal or synthetic resin. The unit also comprises an electric lamp 10 which is provided with a light-transmitting lamp vessel 11, for example made of quartz glass, i.e. glass with an SiO2 contents of at least 95% by weight, which is sealed in a gastight manner and has a discharge space 12 in which an electric element 13, a pair of electrodes in the Figure, is arranged. The lamp vessel has a first 14 and a second 15 seal, which are mutually opposed, while a respective first 16 and second current conductor 17 runs through each seal and is connected to the electric element 13 and issues from the lamp vessel 11 to the exterior. The second current conductor is electrically connected to a second metal wire 37a which extends alongside the lamp vessel and through the neck shaped portion and is connected to a second electric contact 21a provided on a lamp cap 20.
The lamp shown is a high-pressure mercury gas discharge lamp which has a pressure of approximately 200 bar or more during operation. The lamp vessel contains besides mercury a rare gas, for example argon, and bromine. The electric lamp 10, which consumes a power of approximately 100 W to approximately 450 W, is fixed in the reflector body 1, by means of cement 19 in the Figure, with the first seal 14 inside the neck-shaped portion 5, the discharge space 12 inside the reflecting portion 2, and the electric element 13 on the optical axis 4.
The lamp cap 20, made of ceramic material in the Figure such as, for example, steatite, with a first electric contact 21 to which a current conductor 16 is connected, is fixed to the neck-shaped portion 5 of the reflector body 1, by means of cement 29. The ceramic lamp cap has a hole opening 23 around the optical axis 4 which hole opening is narrower than an opening 24 in the neck shaped portion, thus a seat 25 is formed. A ring 58 is present in the neck-shaped portion adjacent the ceramic lamp cap and around the first seal 14 of the electric lamp 10. The ring, which is made, for example, of stainless steel, rests against the seat 25 of the ceramic lamp cap and surrounds the first seal with a small clearance all around, for example, of 0.0.5 mm. The ring is kept in position by spirally shaped antenna 35 which is provided around the first seal and which is electrically connected to the second current conductor. The antenna is compressed in between the ring and a wall 9 of the discharge space, hence the antenna exerts an axially directed pressure on the ring towards the ceramic lamp cap and keeps it positioned there.
The reflector body 1 shown is closed off by a transparent plate 30. The plate is fixed with cement 39 in the Figure, but could alternatively have been mounted by other means, for example a flanged metal ring. The reflective portion 2 has a substantially cylindrical end portion 7 adjacent the transparent plate 30, whereby the volume of the reflective portion is increased without substantially increasing also the diameter of the unit.
Fig. 3 (not to scale) shows a first seal 14 in a neck shaped portion 5 of a reflector body 1, the seal 14 incorporating an electric conductor 16 in the form of a foil 16a in a plan view which connects a first electrode 34 to a metal wire 37 projecting to the exterior from the first seal, which first seal has a first gastight portion 14a and a second gastight portion 14b between which a gas-filled cavity 31 is present. The cavity comprises at least a gaseous constituent of the filling, for example, the cavity comprises argon.
At the area of the cavity, the first seal has a widening portion 41 around which an external antenna 35 is provided, the antenna being squeezed in between a wall 9 of the discharge space 12 and a ring 58. The first seal 14 constitutes a collapsed seal, but alternatively could be a pinched seal. The foil 16a is a Mo-strip having knife edges. The metal wire 37 is secured via a wire part 16d of the current conductor 16 to one end 16b of the strip 16a, for example, by welding and projects to the exterior from the seal and from the discharge vessel. The electrode rod 34 is secured via the strip 16a to a further end 16c of said strip 16a. In the operating condition of the lamp, a discharge extends between the electrodes. In the embodiment described, a very reliable passive antenna is thus realized in an extremely simple manner.
A ring 58 is provided around the first seal, the ring 58 rests on a ceramic lamp cap 20 which is fixed at a rear side 36 of the neck shaped portion 5 of the reflector body 1. The ring 58 practically closes off an opening 38 in the neck shaped portion and counteracts the flow of cement 19 into the neck shaped portion and thus onto the reflective surface 3. The antenna 35 simultaneously functions as a metal spring which exerts an axially directed pressure on the ring 58 towards the ceramic lamp cap 20, thus being fixed and kept in position there. Furthermore, the ring 58 surrounds the first seal of the lamp vessel adjacent the widening portion 41 of the first seal 14, thus a clearance 42 between the opening in the ring and the first seal of the lamp vessel is practically closed off and flow of cement 19 through said opening in the ring is prevented. The ceramic lamp cap has only one electrical contact (not shown), as the second metal wire (ref. nr. 37a in Fig.2) does not extend through the neck shaped portion but is lead elsewhere to the exterior via the reflective portion 2 (not shown).
In Fig. 4 shows a similar detail as shown in Fig. 3 (not to scale) with all technical features being the same as shown in Fig. 3 except for the construction of the ceramic lamp cap 20. The ceramic lamp cap 20 is provided with a stepped profile 61, indicated by the circle. As a result the ceramic lamp cap has a first part 62 of the hole opening 23 adjacent the neck shaped portion 5 of the reflector body 1, and a second part 63 of the hole opening distant from said neck shaped portion. The first part 62 has an inner diameter D_l which is larger than an inner diameter D_r of the neck shaped portion of the reflector body. The second part 63 has an inner diameter D_s which is smaller than the inner diameter D_r of the neck shaped portion of the reflector body. The ring 58 fits with ample spacing within the first part 62 to enable adjustment transversal to the optical axis 4 necessary for alignment of the lamp vessel 11 in the reflective portion 2 of the reflector body, but the ring is too large to fit in the second part 63. The ring 58 is pressed against the stepped profile 61 by the antenna 35.

Claims

A unit of a lamp and reflector comprising:
- a reflector body provided with a reflective portion with a concave reflective surface and defining an optical axis, and as an integral part of the reflector body provided with a neck shaped portion surrounding with an opening the optical axis,

- an electric discharge lamp provided with a lamp vessel having a gastight discharge space in which an electric element is arranged on the optical axis, the discharge space being closed by a first and a second, mutually opposed seals through which first and second seal respectively a first and a second electric current conductor extend from the electric element to the exterior;

- a ceramic lamp cap fixed to a side of the neck shaped portion facing away from the reflective portion and surrounding with a hole opening the optical axis, the lamp cap being provided with at least one electrical contact to which at least one current conductor is electrically connected;
the lamp vessel being fixed with an adhesive compound in the neck shaped portion via its first seal and with the discharge space in the reflective portion,
a ring is provided around the first seal for counteracting the adhesive compound to flow from the neck shaped portion into the reflective portion during manufacturing of the unit,
characterized in that the hole opening in the ceramic lamp cap is narrower than the opening in the neck shaped portion for the ceramic lamp cap to function as a seat for the ring.
The unit as claimed in claim 1, characterized in that the first seal has a first and a second sealed portion between which a cavity is present and in that the first seal has a widening portion at the location of the cavity, the ring being located in between the widening portion and the transition area.
The unit as claimed in claim 2, characterized in that an opening in the ring through which the first seal extends, is practically closed by the widening portion.
The unit as claimed in claim 1, 2 or 3, characterized in that a spiral is provided around the first seal which spiral exerts resilient pressure on the ring towards the neck shaped portion.
The unit as claimed in claim 4, characterized in that the spiral is made of electrically conducting material and functions as an external antenna.
The unit as claimed in claim 5, characterized in that the antenna is electrically connected to the second current conductor
The unit as claimed in any of the claims 1 to 6, characterized in that the hole opening in the ceramic lamp cap has a stepped profile in which a first part of the hole opening adjacent the neck shaped portion has a diameter D_l which is larger than an inner diameter D_r of the opening in the neck shaped portion, while a second part of the hole opening remote from the neck shaped portion has a diameter D_s which is smaller than the diameter D_r of the opening in the neck shaped portion.
The unit as claimed in claim 7, characterized in that the ring is clamped in between the stepped profile of the ceramic lamp cap and the neck shaped portion of the reflector body.