Capped high-pressure discharge lamp and lampholder for same

Abstract: The capped high-pressure discharge lamp (1) has a lamp cap of insulating material (10) provided with a centrally disposed contact member (12) and with a metal sleeve (13) concentrical thereto. A first end (3) of a discharge vessel (2) is mounted within said metal sleeve (13) and a current supply conductor (7) is attached to said metal sleeve (13). The rotationally symmetrical geometry of the cap allows insertion of the lamp (1) into a holder (20) in any rotational position.

Description: The invention relates to a capped high-pressure discharge lamp comprising a lamp vessel which is closed in a vacuumtight manner and has opposing first and second ends and an ionizable gas filling, and in which a pair of electrodes is arranged; a first and a second current supply conductor which are connected to the pair of electrodes and which issue to the exterior from the first and the second end, respectively; a lamp cap of insulating material mounted to the first end of the lamp vessel and provided with a first, central contact member which is connected to the first current supply conductor, and with a second contact member which is connected to the second current supply conductor. The invention also relates to a lampholder for such a lamp. Such a capped high-pressure discharge lamp and a lampholder suitable for it are known from EP 0 157 357 B1. Lamps of this kind are designed for use in scenic illumination when positioned inside a reflector, for example, for photo, film, or video shots. For that purpose, it is favourable if the reflector surrounds the lamp through a large solid angle, because in that case a large fraction of the generated light is concentrated into a beam. The lamp cap of the known lamp has a laterally extending slot in which the second current supply conductor and the second contact member are eccentrically fixed with cement, laterally situated relative to the first contact member. The lamp cap as a result has a comparatively great lateral dimension and the reflector of the luminaire in which the lamp is to be used must have a comparatively great opening so that the lamp cap can be inserted through it into the lampholder arranged outside the reflector. This causes a loss in the beam concentration power of the reflector. Moreover, insertion of the lamp into the lampholder is difficult because the lamp cap must be accurately aimed during this in order to bring the second contact member into contact with the corresponding terminal of the lampholder. The invention has for its object to provide a lamp of the kind described in the opening paragraph which inter alia can be easily inserted into a holder. The invention also envisages a lamp having a lamp cap which can be of compact design. Furthermore, the invention envisages a lampholder for such a lamp. The envisaged lamp is realised in that the lamp cap has a substantially rotationally symmetrical metal sleeve around the first end of the lamp vessel, which sleeve is substantially concentric with the first contact member, within which sleeve the first end is fixed, and to which sleeve the second current supply conductor is fastened. The metal sleeve forms the second contact of the lamp cap. Owing to the rotationally symmetrical configuration of the contacts of the lamp cap, the latter may be inserted into the lampholder in any rotational position. It is also possible, as a result, to give the lamp cap a compact design. In a favourable embodiment, the metal sleeve has a circumferential relief, for example a circular elevation or circular groove, with which a corresponding clamp of a lampholder can cooperate. The clamp may either serve exclusively for retaining the lamp or also for achieving an electrical connection to a supply source. The lamp cap may have elevations around the first central contact member on a circle which is concentric with this contact member. These elevations may cooperate with the lampholder in which the lamp is inserted in order to form a depth stop. This is important for positioning the lamp with its electrodes in a spot inside a reflector previously determined by the luminaire manufacturer. To reduce the breakdown risk, it is useful if the central contact member is surrounded by a circular rim of the lamp cap. The second current supply conductor may be connected to the neutral lead of the supply terminal of the lamp for handling safety. In addition, this current supply lead may be surrounded at least substantially by an insulator. This is also useful if the ionizable filling of the lamp contains sodium, with the object of preventing the disappearance thereof as a result of photoemission. It is favourable if the insulator is an insulating coating of the second current supply conductor. Such a coating, for example of Si₃N₄ and/or SiO₂, possibly on a bonding layer of Al₂O₃, renders it possible to insulate a kinked or curved current supply conductor also on kinks or curves. The lampholder according to the invention designed for use with the capped high-pressure discharge lamp according to the invention is provided with a body of insulating material comprising a first cavity with a first clamping contact and an insertion opening in order to give a first, central contact member of the lamp access to the clamping contact; a second clamping contact outside the first cavity for making contact with a second contact member of the lamp; - the second clamping contact being substantially concentric with the first and comprising several contact elements which project from the body of insulating material. In an embodiment, the body of insulating material, for example of ceramic material, such as steatite or mica-filled glass, has a circular second cavity around the first cavity so as to accommodate a circular rim of the lamp cap. It is favourable if the body of insulating material of the lampholder has a tapering surface for cooperating with elevations of the lamp cap. Such a surface in conjunction with these elevations then not only forms a depth stop for the lamp, but also has a centring function. In an embodiment, the tapering surface is convex. It then has a locating function during insertion of the lamp cap into the lampholder, which facilitates the centring action. An embodiment of the capped high-pressure discharge lamp and of the lampholder according to the invention is shown in the drawing, the discharge vessel in side elevation, the lamp cap and the lampholder in which the lamp is placed in longitudinal section. In the drawing, the capped high-pressure discharge lamp 1 has a lamp vessel 2 which is closed in a vacuumtight manner and is made of, for example, quartz glass, comprising first and second, opposing ends 3 and 4, respectively, and an ionizable gas filling, for example consisting of a rare gas, mercury, and metal halides. A pair of electrodes 5 is arranged in the lamp vessel. First and second current supply conductors 6 and 7, respectively, connected to the pair of electrodes issue from the first and second ends 3 and 4, respectively, of the lamp vessel to the exterior. A lamp cap 10 of insulating material is fastened to the first end 3 of the lamp vessel and provided with a first, central contact member 12 which is connected to the first current supply conductor 6, and with a second contact member 13 which is connected to the second current supply conductor 7. The lamp cap 10 has a substantially rotationally symmetrical metal sleeve 13 around the first end 3 of the lamp vessel, which sleeve is substantially concentric with the first contact member 12 and within which sleeve the first end 3 is fixed. The second current supply conductor 7 is fastened to this sleeve. The metal sleeve 13 has a continuous circular relief in the form of a circumferential groove 14 with which retention means of a lampholder can engage, or a clamping terminal of the lampholder for making electrical contact. Alternatively, a terminal of the lampholder may make contact elsewhere separately from retention means. The central contact member 12 is surrounded by a circular rim 15 of the lamp cap 10. The lamp cap 10 has elevations 11, which serve as a depth stop for the lamp cap, on a circle which is substantially concentric with the central contact member 12. The second current supply conductor 7 is surrounded at least substantially by an insulator, in the drawing it is covered with a coating 8 of SiO₂. The lampholder 20 designed for use with the capped high-pressure discharge lamp 1 according to the invention is provided with a body 21 of insulating material, which has a first cavity 22 with a first clamping contact 23 and an insertion opening 24 to give a first contact member 12 of the lamp access to the clamping contact. The lampholder 20 has a second clamping contact 25 outside the first cavity 22 in order to make contact with a second contact member of the lamp. The second contact clamp 25 is substantially concentric with the first 23 and comprises several contact elements, two of which 25a and 25b are shown in the drawing. These contact elements project from the body 21 of insulating material. The lampholder 20 has a circular second cavity 27 around the first 21 in order to accommodate the circular rim 15 of the lamp cap 10. The body 21 of insulating material has a tapering surface, in the drawing a convex tapering surface 26. It has a locating function during insertion of the lamp cap 10, forms a depth stop together with the elevations 11, and centres the lamp cap 10.

Claims: A capped high-pressure discharge lamp (1) comprising a lamp vessel (2) which is closed in a vacuumtight manner and has opposing first (3) and second (4) ends and an ionizable gas filling, and in which a pair of electrodes (5) is arranged; a first (6) and a second (7) current supply conductor which are connected to the pair of electrodes (5) and which issue to the exterior from the first (3) and the second (4) end, respectively; a lamp cap (10) of insulating material mounted to the first end (3) of the lamp vessel (2) and provided with a first, central contact member (12) which is connected to the first current supply conductor (6), and with a second contact member (13) which is connected to the second current supply conductor (7); characterized in that the lamp cap (10) has a substantially rotationally symmetrical metal sleeve (13) around the first end (3) of the lamp vessel (2), which sleeve is substantially concentric with the first contact member (12), within which sleeve the first end (3) is fixed, and to which sleeve the second current supply conductor (7) is fastened. A capped high-pressure discharge lamp as claims in Claim 1, charactertzed in that the metal sleeve (13) has a circumferential relief (14). A capped high-pressure discharge lamp as claimed in Claim 1 or 2, characterized in that the central contact member (12) is surrounded by a circular rim (15) of the lamp cap (10). A capped high-pressure discharge lamp as claimed in Claim 1, 2 or 3, characterized in that the lamp cap (10) has elevations (11) on a circle which is substantially concentric with the central contact member (12). A capped high-pressure discharge lamp as claimed in Claim 1 or 2, characterized in that the second current supply conductor (7) is surrounded at least substantially by an insulator (18). A lampholder (20) for use with the capped high-pressure discharge lamp (1) as claimed in any one of the Claims 1 to 5, which lampholder is provided with a body (21) of insulating material and comprises a first cavity (22) with a first clamping contact (23) and an insertion opening (24) in order to give a first, central contact member of the lamp access to the clamping contact; a second clamping contact (25) outside the first cavity (22) for making contact with a second contact member of the lamp; the second clamping contact (25) being substantially concentric with the first (23) and comprising several contact elements (25a, 25b) which project from the body (21) of insulating material. A lampholder as claimed in Claim 6, characterized in that a circular second cavity (27) is present around the first cavity (22). A lampholder as claimed in Claim 6 or 7, characterized in that the body (21) of insulating material has a tapering surface (26).

Inventors: VAN DULMEN HENDRIKUS ALBERTUS, VERSPAGET GODEFRIDUS NICOLAAS, VAN DULMEN, HENDRIKUS ALBERTUS MARIA, VERSPAGET, GODEFRIDUS NICOLAAS MARIA
Applicants: PHILIPS ELECTRONICS NV, PHILIPS ELECTRONICS N.V.
Application year: 1991
Main classification: H01J5
IPC codes: H01J61, H01R33, H01K1, H01J5, F21V19