JPS5944745B2 - high pressure steam discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to an arc discharge lamp utilizing an alumina ceramic envelope, and more particularly to a sealing structure for an end portion and a lead wire thereof.

Alumina ceramic envelopes are of particular interest in connection with high pressure sodium vapor tubes, which are currently widely used for outdoor lighting due to their high efficacy of over 100 lumens per watt.

Alumina ceramics withstand sodium at high temperatures, and dense polycrystalline alumina and single crystal alumina, or synthetic sapphire, are utilized as the lamp envelope.

The rung filling is sodium with a rare gas to make starting easier, and mercury for more efficiency.

The ends of the alumina tubes are sealed by suitable closure members connected to the thermionic electrodes.

Ceramic arc tubes are generally supported within an outer glass envelope or jacket having a threaded cap at one end.

The electrodes of the arc tube connect to the terminals of the base, ie, the shell, and the center contact, and the space between the outer bodies is usually evacuated to conserve heat.

One of the end seals for an alumina ceramic arc tube described in McVie U.S. Pat. No. 3,882,346.
One design utilizes a ceramic plug sealed to the end of the arc tube with a central hole and a metal compatible with the ceramic, i.e., a metal that roughly matches the coefficient of expansion of the ceramic, such as alumina ceramic. In this case, a wire made of a metal such as niobium or tantalum is sealed through the hole.

Sealing is achieved by a vitreous sealing component that melts when the assembly is properly heated, creating ceramic-to-ceramic and ceramic-to-metal seals.

Such seals are more economical than conventional ones utilizing thin-walled niobium tubes.

However, the design is more critical because rigid leads cannot deform as quickly in response to thermally induced stresses as thin-walled tubes.

During sealing, the assembly is heated until the sealing component, or frit, melts and is drawn by capillary action into the annular gap between the arc tube and the ceramic plug and through the plug into the hole in the drop wire. .

The problem that arises is the destruction of the hermetic seal, especially the lead wire f.
This was an accidental breakage of the f7i's seal.

One object of the present invention is therefore to overcome this drawback.

Another problem that arises with this seal design is the uneven distribution of the sealing frit between the arc tube and plug peripheral seal and the plug and drop wire center seal, which causes the seal to weakens and causes leakage.

Another objective of the invention is to eliminate this problem.

Failure of the seal may be due to excessively high temperatures where the leads extend through the perforated ceramic plug or excessive temperature gradients along or across the mating surfaces. understood.

The prevention method is to thermally isolate the lead seal from the electrode.

According to the invention, this is achieved by looping the supporting conductor interposed between the electrode and the sealed portion of the lead.

Such a loop shall be provided during operation while ensuring sufficient heat from the arc tube and electrode structure reaches the junction of the ceramic plug and the conductor to prevent condensation of sodium and mercury amalgam therein. Provide thermal insulation.

The loop also supports the ceramic plug during sealing.

Also, a traversal member attached to the lead over the ceramic plug was used as a banger to support the lead, electrode, and plug assembly to the end of the arc tube during sealing.

According to the invention, the traversal member is placed close to the surface of the plug and serves as a wick that supplies the melt sealing frit to the seal by capillary action.

The traversing material is placed at two sealing points, the annular seal between the arc tube and the plug, and the seal between the plug and the lead wire, so that a reliable and more even seal is formed.
It is possible to evenly distribute the sealing frit.

A high pressure sodium vapor lamp 1 embodying the preferred form of the invention and corresponding to 400 watts is shown in FIG.

It is made up of a vitreous outer envelope 2 with a standard threaded cap 3 attached to one half thereof, and a recessed stem press 4, through which a pair of relatively heavy conductive wires 5,
The outer ends of 6 are connected to the threaded part 7 and the small hole 8 of the cap, respectively.

The arc tube 9, located centrally within the outer envelope, consists of a piece of crystalline alumina tube, the lower end of which is closed by a suitable metal end cap 10, such as niobium, which matches the coefficient of expansion of the alumina ceramic.

Also, the metal tube 11 made of niobium is sealed by the cap and serves for evacuation and filling of the tube during the manufacture of the lamp.The evacuation tube is sealed at its outer end and is used during operation of the lamp. , serves as a reservoir in which the excess vaporizable metal, in this case the sodium mercury amalgam, condenses.

The lower electrode in the lamp is attached to the inward protrusion of the conductor 11.

A short wire connector 12 is welded to the tube body 11 and also to a short support rod 13, which in turn is welded to the drop wire 5.

The support bar 13 is fastened to the single cross bar 14 by means of a strip 15 attached to the same transverse bar 14 welded to the conductor 6, which strip 15 is connected to an insulator 16 threadedly connected to the support bar 13. surround.

The upper end of the arc tube is sealed by a perforated alumina ceramic plug 17 best shown in FIG.

As shown, the plug has a hole in the center through which the niobium lead 18 is sealed by a sealing member shown at 19.

The plug is in turn sealed to the end of the arc tube 9 by a sealing ring designated 20.

Lead wire 18 supports the upper electrode within the arc tube, and its outer portion extends through a loop 21 of transverse support wire 22 attached to crossbar 14.

With this arrangement, during operation, the arc tube is thermally stretched and the elastic metal ribbon 23 ensures a good electrical connection.

The upper end of the horizontal bar 14 is the opposite nipple 2 at the dome end of the outer envelope.
It is tightened by a spring clamp 24 that fits into the 5.

The outer envelope or jacket is evacuated by the pumping action and flashing of the getter ring 26.

A metal reflective strip 27 is preferably placed around the top of the arc tube, especially for small lamps, such as those under 250 watts, to maintain the desired temperature.

The lamp shown is designed to be used with the base facing down.
It has an amalgam reservoir 11 at its lowest part.

In a similar design for cap-up use, the arc tube is oriented in the opposite direction relative to the outer envelope to position the amalgam reservoir at the bottom, and the inflation slip loop 21
The arc tube support including the arc tube support is also suitably inverted.

Hermetic seals, including sealing lead wires through ceramic plugs and sealing plugs to arc tubes, can be accomplished using a variety of sealing members.

This is sometimes done using what is called sealing glass, which is primarily made of aluminum oxide or calcium oxide.

One ingredient we have effectively used is called G-54, which has a large weight ratio of 4.0% Al2O3 and 51% carbon.
It consists of a038.5% and Mg07.5%.

(Other ingredients used include Ross U.S. Pat. No. 32,813.
No. 09, Thurber et al., U.S. Pat. No. 3,441,421, and McVie, U.S. Pat. No. 3,588,577.

The lamp has a self-heating thermionic electrode 28 as best shown in FIG.

The electrode consists of two helical layers 29 of tungsten wire wound around a tungsten shank 30.

The turns of the inner helical layer are spaced apart, e.g. dibarium calcium tungstate B a 2Ca
The electron-emitting material, such as WO6, is surrounded by the interstices between the turns.

The inner end of the lead wire 18 is bent radially (as soon as it passes through the hole through the plug 17) and then bent into a ring-shaped loop 31, in which the shank 30 of the electrode
Extends to an inwardly downwardly directed extension that is welded at point 2.

The loop 31 defines a flat surface and serves as a pedestal to support the ceramic plug 17 before sealing.

The lead, electrode and ceramic plug assembly before sealing is best shown in FIG. 3, with the plug and electrode shown in dotted lines.

The light traverse wire 33 is connected to the lead wire 18 directly above the plug 17.
are spot welded to serve to support the assembly as it is lowered into the open end of arc tube 9.

The traverse wire is bent slightly about its center point in a horizontal plane transverse to the lead wire in order to bring its ends into contact with the edges of the arc tube in a vertical diametric plane.

The assembly thereby hangs vertically within the tube.

A measured amount of the sealing component, glass frit, is placed as a slurry on the ceramic plug, and the assembly is then heated to the melting temperature of the glass frit so that upon cooling, a seal is formed.

The molten frit is drawn by capillary action into the ring-shaped gap between the arc tube and the plug and the gap between the plug and the drop-in wire, forming a seal upon cooling.

This method makes it easy to remove air from the frit.

Prior to the present invention, frit would often collect at the peripheral seals of the plug and arc tube, leaving insufficient amounts at the center seal of the lead, and vice versa.

However, in accordance with the present invention, as shown, a traverse member 33 is placed close to the surface of the ceramic plug 170 to serve as a wick for the fused seal frit during the sealing operation.

This equalizes the distribution of the sealing frit between the arc tube and plug peripheral seal and the plug and lead wire center seal.

The surface tension of the molten frit causes a five-wedge-shaped liquid sphere to form between the top surface of the ceramic disk and the underside of the traversal member, as shown in FIG.

This causes the molten frit to flow in either direction between the plug and the peripheral seal of the arc tube and the lead wire and the center seal of the plug, thereby allowing it to flow evenly.

The result is a more reliable and more uniform seal.

FIG. 4 shows a modification of the lead wire and electrode assembly in which the inner portion of the niobium drop wire 18' is cut at a point corresponding to its exit from the hole through the ceramic plug.

A small U-shaped connector member 34 of niobium is welded to the distal end of lead 18' at 350 to form a transverse support.

The upper side of the connector member 34 serves to support the ceramic plug before and between the seals, and the shank of the electrode is welded to the lower side of the connector member 34 at 36.

The transverse members 33 also provide a convenient means of locking the reflective strip 27 in place.

As shown in FIG. 2A, the flex tabs 37 prevent the ends of the traversal from sliding off the arc tube when they reach the top of the strips, and also prevent the ends of the traverse from sliding off the ends of the arc tube. prevent.

In the single member lead wire structure shown in both FIGS. 2 and 3, and the two member lead wire structure shown in FIG.
Pressure is used during resistance welding of the tungsten electrode shaft 30 to the end of the niobium lead wire 18 or to the niobium connector member 34.

This causes the hard tungsten to deform the niobium, thereby creating a large area joint that has adequate strength to support the relatively large tungsten electrode despite vibration and shock during use. .

The reliability of ceramic and metal type seals is critically influenced by temperature or by temperature gradients along or across the interface.

Very high temperature gradients occur in the end structure of ceramic discharge lamps.

A heat-resistant electrode whose leads extend through a ceramic-to-metal seal creates a plasma whose temperature exceeds 3,000 degrees Celsius.

There, these seals are destroyed and their lifespan is 800 degrees Celsius.
It is greatly shortened at higher temperatures.

The coil structure of the electrode contains an electron emissive material, which must be operated at a temperature high enough to slowly release the electrode actuating element so that useful electrons are emitted.

The conflicting demands of a hot electrode and a cooler electrode lead seal are met in accordance with the present invention by a loop 3 of niobium drop wire that lengthens the heat transfer path from the electrode shaft 30 to the lead seal.
satisfied by 1.

The U-shaped connector member 34 serves the same function in the embodiment of FIG. 4. Typical temperatures found in a 400 watt high pressure sodium lamp such as that shown in FIG. ing.

The corresponding temperature points are shown in FIG.

From the above table it can be seen that the axial temperature drop along the length of the wire seal from the inner surface to the outer surface of the ceramic plug is only 50.degree.

The temperature drop from inside to outside of the ring seal between the arc tube and the plug is only 20°C.

Therefore, the requirements that the temperature of the electrode coil, ie, the main body, be 1300° C. and that the seal of the lead-in wire should not be higher than 800° C. are satisfied, and the temperature gradient along the seal is reduced.

Next, to summarize the embodiments of the present invention, (1) the inner part of the lead wire is bent in the radial direction immediately after passing the hole,
2. A lamp as claimed in claim 1, characterized in that it is then bent into a ring-shaped loop, terminating in an inward and downward extension to which the electrodes are attached.

(2) A connector member is attached to the distal end of the inner portion of the lead wire, and the electrode is attached to the connector member forming the intervening loop. lamp.

(3) The ceramic is alumina, the lead wire is made of niobium, and the electrode is formed by a tungsten coil on a tungsten shank attached to the end of the intervening loop. Lamp described in Section 1.

(4) said lead wire bends radially immediately beyond said hole, and then bends into a ring-like loop, which terminates at an inwardly directed downward extension, said electrode being at the end of said extension; 2. A lamp as claimed in claim 1, characterized in that it is formed by a tungsten coil on a tungsten shank welded to the tungsten shaft.

(5) The lamp according to embodiment 4), wherein the outer envelope is made of alumina, and the lead wire is made of niobium.

(6) the traverse is a small wire welded to the lead directly above the plug, which is placed on the arc tube wall to serve as a banger to support the closure member of the arc tube during sealing; 3. The lamp according to claim 2, characterized in that it reaches the following.

(7) the traversal member is bent in a plane perpendicular to the lead wire sufficiently to contact the arc tube wall at a diameter such that the closure assembly hangs vertically within the arc tube during sealing; The lamp according to embodiment (6), characterized by:

(8) having a metal reflective strip around one end of the arc tube, with both ends of the traversing member reaching above the strip, thereby preventing the strip from slipping off the end of the arc tube; The lamp according to embodiment 6), characterized in that:

(9) The lamp according to claim 2, wherein the ceramic is alumina and the lead wire is made of niobium.

00) Embodiment (8) characterized in that the ceramic is alumina and the wire is a niobium wire.
The lamp described in.

[Brief explanation of the drawing]

FIG. 1 is a side view of a ceramic arc tube lamp embodying the present invention, FIGS. 2 and 2A are partial cross-sectional views of the upper end of the arc tube, and FIG. 3 is a view descending to the end of the arc tube for sealing. The ready ceramic plug, wire, and electrode assembly is shown. FIG. 4 shows a modification of the wire and electrode assembly. 1... High pressure sodium vapor pair, 2...
Vitreous outer envelope, 3...Standard type threaded cap, 4
...Recessed stem press, 5, 6 ... Conductor, 7 ... Threaded part, 8 ... Small hole in base, 9 ...・Arc tube, 10...Metal end cover, 11...Metal tube, 12...
・Short wire connector, 13...Support rod,
14...Horizontal bar, 15...Band body, 16.
... Insulator, 17 ... Perforated alumina ceramic plug, 18 ... Niobium lead wire, 19 ... Sealing component, 21 ... Loop , 22... Support wire, 23... Elastic metal ribbon, 24... Spring clamp, 25...
... Reverse nipple, 26 ... Getter ring, 27 ... Metal reflective band, 28 ...
...Thermionic electrode, 29...Two spiral layers of tungsten wire, 30...Shaft of electrode, 33
...Transverse (member) member, transverse wire.

Claims (1)

[Scope of Claims] 1. A high-pressure discharge lamp comprising a tubular translucent ceramic tube having a closing member and an electrode attached in a sealed manner at both ends thereof, the closing member at one end of the ceramic tube being a sealing member. A ceramic plug sealed between the ceramic tube and the ceramic tube by a frit, and the closing member has a through hole through which a metal lead wire is sealed, and the coefficient of thermal expansion of the metal matches that of the ceramic. In a high-pressure discharge lamp in which a linear transverse member is attached to the lead wire in the vicinity of the plug, the linear transverse member 33 acts as a wick, so that the plug 17 and the ceramic tube 9 are connected to each other. and a seal 190 between the lead wire 18 and the plug 17. The linear transverse member 33 is connected to the plug 17 so that the melted sealing frit is evenly distributed between the two sealing locations. A high-pressure discharge lamp characterized in that it is placed extremely close to. 2. Both ends of the linear transverse member 330 are stretched to the reflective strip 27 provided at one end of the ceramic tube 9 in order to prevent the reflective strip 27 from slipping off the ceramic tube. A high-pressure discharge lamp according to claim 1, characterized in that: