Discharge vessel wire support

Abstract

 A high-pressure discharge lamp arrangement in which the support wire (25, 27) for the discharge vessel (11) of the lamp has its end (37, 39) which is inserted in the open tubular electrode structure (13, 15) of the lamp expanded so that its external dimension more nearly equals the internal dimension of the tube (17, 19).

Description

[0001] The invention relates to a high-pressure dis­charge lamp including a ceramic discharge vessel having at one end a hollow cylindrical lead-through element as a part of an electrode construction having on the side remote from the discharge vessel an opening of defined substantially circular cross-section, in which a wire-­shaped supporting member is arranged.

[0002] The term "ceramic discharge vessel" is to be understood in this description and the appended Claims to mean a discharge vessel having a wall of crystalline oxidic material containing at least aluminium oxide. This may be, for example, monocrystalline sapphire. Other possibilities are for instance densely sintered polycrys­talline aluminium oxide or yttrium-aluminium-garnet.

[0003] The lead-through element is generally connected by means of a melting glass connection in a gas-tight manner at the end to the discharge vessel. It is common practice that the lead-through member is made of niobium because this material has an expansion coefficient which differs comparatively slightly from that of aluminium oxide. However, molybdenum has also been suggested. The lead-through member will generally be provided with means for positioning the lead-through element in the end of the discharge vessel before a gas-tight melting glass connection is established. These positioning means can consist of one or more local deformations of at least the outer surface of the lead-through element. A large number of variations is known from literature.

[0004] In the known lamp, which is widely used in public illumination, there is a comparatively large amount of clearance between the lead-through element and the supporting element. A certain amount of clearance is necessary with a view to the neutralization of expansion and shrinkage due to temperature variations occurring during operation of such lamps. However, too large an amount of clearance is disadvantageous because this results in that the discharge vessel can start to vibrate unneces­sarily with respect to the supporting element, for example during the transport of the lamp.

[0005] Wire-shaped supporting elements are generally obtained by cutting, clipping or mechanically severing in another manner lengths of wire of prescribed length from a supply. In this case, burrs are formed. Such burrs may lead to damage of the lead-through element.

[0006] The use of wire-shaped supporting elements is very advantageous with a view to material consumption and is particularly suitable for comparatively simple automized mass production.

[0007] The invention has for its object to provide a measure which, whilst maintaining a favourable material consumption and the possibility of the use of simple and automatized mass production, results in a more rigid lamp construction.

[0008] For this purpose, according to the invention, a lamp of the kind mentioned in the opening paragraph is characterized in that the wire-shaped supporting element is provided, at least as far as it is located within the hollow lead-through element, with a plastically deformed part having a largest outer dimension substantially equal to the defined cross-section of the opening.

[0009] An advantage of the invention is that the amount of clearance between the lead-through element and the supporting element is limited, as a result of which the possibility of damage of the lead-through element by a burr of the wire-shaped supporting element is also limited. A further advantage is that in this manner the wire-shaped supporting member can serve for centering the discharge vessel. This is favourable especially with the use in reflector luminaires.

[0010] Plastic deformation of metal wire can generally be realized in mass production.

[0011] In a first advantageous embodiment, the plas­tically deformed part of the wire-shaped supporting element is formed as a coiled wire. In a second advantageous embodiment, the plastically deformed part of the wire-­shaped supporting element is formed as a flattened wire.

[0012] Coiled wire and flattened wire are both wire shapes which can be realized very well by means of a simple reproducible mass production. Especially in the case of a flattened wire, the absence of a burr can also be ensured due to the fact that the end of the length of wire is flattened. Damage of the lead-through element due to a burr is then not possible.

[0013] A further improvement of the lamp construction can be attained in that the flattened wire part consists of two portions, which are arranged substantially at right angles to each other.

[0014] The Japanese Patent laid open Publication 61-118955 (1986) discloses, it is true, a construction of a supporting element having a rectangular cross-section at the area at which it is passed into the hollow lead-­through element. However, on the one hand a beam-shaped element is used as a supporting element, which conflicts with advantageous material consumption, while on the other hand the lead-through element is deformed at the area of the supporting element in such a manner that it encloses the supporting element. This requires a particular treat­ment of the lead-through element.

[0015] Preferably, a lamp according to the invention is provided with two ends each provided with a hollow cylindrical lead-through element, which is provided on the side remote from the discharge vessel with an opening of defined substantially circular cross-section, in which a wire-shaped supporting element is arranged, which is provided, at least as far as it is located within the relevant lead-through element, with a plastically deformed part having a largest outer dimension substantially equal to the defined cross-section of the opening. Due to the fact that the lamp is provided with a similar construction on either side of the discharge vessel, the manufacture is comparatively simple and a rigid lamp construction can be realized.

[0016] A further improvement with respect to the rigidity of the lamp construction can be realized in the case in which the flattened wire portions of each of the supporting elements are arranged substantially at right angles to each other.

[0017] Other objects, features and advantages of the invention will be apparent to those skilled in the art from the following description and appended claims when considered in conjunction with the accompanying drawing in which:

Figure 1 is a partial view of a high pressure discharge lamp showing one embodiment of the invention;

Figure 2 is a partial view of a high pressure discharge lamp showing another embodiment of the invention;

Figure 3 is a partial view of a high pressure discharge lamp showing yet another embodiment of the invention; and

Figures 4a and 4b are orthogonally arranged views of a part of the embodiment of Figure 3.

[0018] The drawing is not to scale. Similar elements of the structures disclosed are identified by the same reference characters in the various Figures of the drawing.

[0019] Referring to Figure 1 of the drawing there is shown a discharge vessel in the form of an arc tube 11 having electrode structures 13 and 15 at each of its ends. As is typical these structures include as hollow cylindrical lead-through elements niobium tubes 17 and 19 and electrodes 21 and 23. The support means for arc tube 11 includes support wires 25 and 27 each having a prescribed length which could be different for each wire depending on the lamp design. Wires 25 and 27 are depicted as two separate wires but could be two ends of a single prescribed length of support wire which would later be cut in two. The niobium tubes 17 and 19 are each provided on the side remote from the arc tube with an opening having a defined substantially circular cross-section.

[0020] In the Figure 1 embodiment of the invention the ends of support wires 25 and 27 which are inserted in the open ends of niobium tubes 17 and 19 are plastically deformed to coiled portions 29 and 31 in order to form expanded parts whose external dimensions nearly equal the internal dimension of the niobium tubes. The expanded parts can provide centerline alignment between the discharge vessel and the support wires. They also provide more lateral support than wires 25 and 27 would provide without expanded parts.

[0021] Figure 2 shows an arrangement similar to Figure 1. Instead of coiling the ends of support wires 25 and 27 to form coiled portions 29 and 31 as in Figure 1, however, the ends of support wires 25 and 27 are plastically deformed by flattening to form flat portions 33 and 35. It is to be understood that the edges of flat portions 33 and 35 are so disposed that they are at approximately right angles to each other which favours the rigidity of the lamp construction.

[0022] Figure 3 shows the presently preferred embodiment of the invention. In this embodiment flat portions 33 and 35 of the arrangement of Figure 2 are replaced by dual flattened end portions 37 and 39. As can be seen from Figures 4a and 4b each of these axial sections comprises two flattened portions 41 and 43 with rounded edges disposed at approximately right angles to each other. Flattened portions 41 and 43 are readily provided at the ends of wires 25 and 27 by crimping the ends of these wires as desired. It is contemplated that more than two flattened portions could be provided at the ends of each of wires 25 and 27. If so these might be arranged at different angles from the 90° angle shown in Figures 4a and 4b.

[0023] It is understood that various modifications to the above described arrangement of the invention will become evident to those skilled in the art and that the arrangements described herein are for illustrative purposes and are not to be considered restrictive.

Claims

1. A high-pressure discharge lamp including a ceramic discharge vessel having at one end a hollow cylindrical lead-through element as a part of an electrode construction, which has on the side remote from the dis­charge vessel an opening of defined substantially circular cross-section, in which opening a wire-shaped supporting member is arranged, characterized in that the wire-shaped supporting element is provided at least as far as it is located within the hollow lead-through element., with a plastically deformed part having a largest outer dimension substantially equal to the defined cross-section of the opening.

2. A lamp as claimed in Claim 1, characterized in that the plastically deformed part of the supporting element is formed as coiled wire.

3. A lamp as claimed in Claim 1, characterized in that the plastically deformed part of the supporting element is formed as flattened wire.

4. A lamp as claimed in Claim 3, characterized in that the plastically deformed part of the supporting element is formed from two flattened wire portions arranged substantially at right angles to each other.

5. A lamp as claimed in any one of the preceding Claims, characterized in that the discharge vessel is provided with two ends each provided with a hollow cylin­drical lead-through element, which is provided on the side remote from the discharge vessel with an opening of defined substantially circular cross-section, in which a wire-­shaped supporting element is arranged, which is provided, at least as far as it is located within the relevant lead-­through element, with a plastically deformed part having a largest outer dimension substantially equal to the defined cross-section of the opening.

6. A lamp as claimed in Claims 3 and 5, characterized in that the flattened wire portions of each of the supporting elements are arranged substantially at right angles to each other.

Drawing