CA1305996C - Single ended high intensity discharge lamp with a specific volume - Google Patents
Single ended high intensity discharge lamp with a specific volumeInfo
- Publication number
- CA1305996C CA1305996C CA000569220A CA569220A CA1305996C CA 1305996 C CA1305996 C CA 1305996C CA 000569220 A CA000569220 A CA 000569220A CA 569220 A CA569220 A CA 569220A CA 1305996 C CA1305996 C CA 1305996C
- Authority
- CA
- Canada
- Prior art keywords
- envelope
- lamp
- electrodes
- arc supporting
- volume
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
- H01J61/827—Metal halide arc lamps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/52—Cooling arrangements; Heating arrangements; Means for circulating gas or vapour within the discharge space
Landscapes
- Vessels And Coating Films For Discharge Lamps (AREA)
- Discharge Lamps And Accessories Thereof (AREA)
Abstract
Abstract of the Disclosure A high intensity discharge lamp includes an envelope formed of vitreous high temperature resistant material, and a pair of electrodes each having a metal rod and an arc supporting electrode, each of the metal rods being sealed at one end of the envelope. The lamp further includes a portion for adjusting the temperature at the wall of the envelope adjacent to the arc support-ing rods, to minimize the differences in the wall tem-perature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substan-tially independent of the lighting postures of the lamp.
Description
The present invention relates to a high intensity discharge lamp and a method of manufacturing the same.
More particularly, it relates to a metal halide lamp and a method of manufacturing the same.
The high intensity discharge lamp was conven-tionally used for outdoor or factory illumination but it has been used these days for illuminating the inside of structures such as the stores whose ceilings are low.
There can be often seen these cases where particu-larly the metal halide lamp is made smaller in size and attached to the low ceiling to use it as an illuminating light source because it has high luminous efficiency and color display.
One thing which has to be done to make the metal halide lame smaller in size is that the lamp used is made to consume a smaller amount of power. Another thing is that the lamp is made to have as smaller a num-ber of component parts as possible and these parts are made as smal]er in size as possible.
The second measure has been mainly studied and the development of a metal halide lamp with its one side sealed, for example, of a quartz double-bulb type, has been advanced instead of the lamp of the conventional both-side sealed type. The lamp of the both-side sealed ; 25 type has two sealed portions while the one of the one side sealed type has one sealed portion. In the case of a metal halide lamp of the quartz double-bulb type with .... . .
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~ luminous bulb and an outer bulb. Each bulb has only one sealed portion and this therefore enables the whole of the lamp to be made smaller in size. The advantage of the luminous bulb having only one sealed portion resides in that surface ar~ ~ substantially smaller and heat loss is thu~ _s, as compared with the one of the conventio~ both-side sealed type, because the sealed portion which is a main cause of the heat loss is present only at one side of the lamp.
Further, the process of sealing the lamp can be made simpler because the sealed portion is only at one side.
However, because this luminous bulb of the one side sealed type is provided with a pair of main electrodes arranged at only one small sealed portion, the distance between front ends of these main electrodes is rela-tively small and limited to a predetermined length. In other words, this kind of luminous bulb has a larger volume behind their main electrodes compaired with the volume between the front ends of the main electrodes.
More specifically, the ratio of volume VAl located be-tween the front ends of the main electrodes relative to volume VBl defined by the remaining volume in the luminous bulb, that is, VA1/VBl, is smaller than 1.5.
Under this conditions, the temperature of the coldest portion in the luminous bulb is likely to change greatly when its lighting angle is changed because the coldest portion can be shifted because of the bending of an arc 13(1 5996 which is formed between the main electrodes.
Therefore, luminous color and efficiency can be changed greatly when a lamp changes lighting positions, limiting the extent of practical use of lamps.
The present invention provides a metal halide lamp of the one side sealed type having the least property changes for its changing lighting angles.
The present invention also provides a method of manufacturing the metal halide lamp of the one side sealed type having the least property changes for its changing lighting angles.
Further the present invention provides a metal halide lamp of the one side sealed type with less irregularity of lamp property for its changing lighting angles.
.1 ! 15 Still further the present invention provides a method of ! manufacturing the metal halide lamp of the one side sealed type with less irregularity of lamp property for its changing lighting angles. In one aspect the present invention provides a high intensity discharge lamp comprising an envelope formed of vitreous high temperature resistant material, a pair of electrodes each having a metal rod and an ar~ supporting electrode, each of the metal rods being sealed at one end of the envelope, and means for adjusting the temperature at the wall of the envelope adjacent to the arc supporting rods, to minimize the differences in the wall temperature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substantially independent of the lighting postures of the lamp.
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More specifically the invention provides a high intensity discharge lamp comprising: an envelope formed of vitreous high temperature resistant material; a pair of electrodes each having a metal rod and an arc supporting electrode, each of said metal rods being sealed at one end of said envelope; wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB
which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 <
VA/VB < 5.0; and means for adjusting the temperature at the wall of said envelope adjacent to said arc supporting rods, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substantially independent of the lighting postures of the lamp.
In a method aspect the invention provides a method of manufacturing a high intensity discharge lamp, comprising the steps of: forming an envelope of vitreous high temperature resistant material; incorporating a pair of electrodes into said envelope, each of said electrodes having a metal rod and an arc supporting electrode; sealing said metal rods at one end of said envelope; and adjusting the temperature at the wall of said envelope adjacent to said arc supporting electrodes, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency for the lamp is substantially independent of the lighting postures of the lamp, wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 < VA/VB < 5Ø
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~305996 This invention can be more fully understood from the following detailed description when taken in con~unction with the accompanying drawings, in which:-Fig. 1 shows the metal halide lamp to which a luminousS bulb of the present invention is applied;
Fig. 2 is a vertically-sectioned view showing an example of the luminous bulb according to the present invention;
Fig. 3 is a vertically-sectioned view showing the luminous bulb of Fig. 2 as it is turned round the vertical 1~ axis at an angle of 90;
Fig. 4 is a graph showing the relation between lighting angles (e) of the lamp and luminous efficiencies (relative values);
Fig. s 5~, B and C show the curves of an arc, caused by changing lighting angles of the lamp; and Fig. 6 shows another example of the luminous bulb according to the present invention.
~ n embodiment of the present invention will now be described in detail with reference to the accompanying drawings.
Fig. 1 shows a construction of the metal halide ,~
~- - 4a -., ~3~59g6 lamp to which a luminous bulb of the present invention is applied. The metal halide lamp shown in Fig. 1 includes outer bulb 11, luminous bulb 20 housed in outer bulb 11, and sealing sections 12 and 22 of these two bulbs. Outer bulb 11 is made of quartz glass and has the sealing section located on only one side thereof.
This outer bulb 11 is therefore of the one side sealed type. A base (not shown) is usually attached to sealing section 12. Luminous bulb 20 includes bulb body (envelope) 21, main electrodes 31 and 32, sealing sec-tion 22, metal foils 41 and 42, and lead lines 51 and 52. Luminous bulb 20 iS also of the one side sealed type, and sealing section 22 is formed on only one side of bulb body (envelope) 21. The volume of bulb body (envelope) 21 is 0.5 CC. A pair of main electrodes 31 and 32 each of which is made of thoriated tungsten, for example, and has a diameter of 0.5 mm, are arranged inside the bulb body (envelope) 21. Base ends (metal rods) 37 and 3a of main electrodes 31 and 32 are con-nected to metal foils 41 and 42 respectively embedded in sealing section 22. One end of each of lead lines 51 and 52 are also connected to these metal foils 41 and 42 respectively. The other end of each of luminous bulb lead lines 51 and 52 are respectively connected to metal 25 foils 61 and 62 air-tightly embedded in sealing section 12 of outer bulb 11. Further, outer bulb lead lines 71 and 72 are connected to these metal foils 61 and 62.
Mercury 26 and argon gas whlch serve as the startlng gas are sealed In bulb body (envelope) 21, and scandlum lodlde and sodlum lodlde whlch serve as the metal hallde are further sealed thereln at a ratlo of 1:5. When bulb body (envelope~ 21 Is sealed, Mer-cury 26 Is attached In the form of llquld spheres on the Innerwall thereof.
In the case of tl1e metal halIde lamp, a voltage Is , applled to the palred maln electrodes, and a dlscharge Is gener-ated In the mercury vapor between the palred electrodes to emlt llght. The Intenslty of thls llght Increases as the vapor pres-sure of the sealed mercury Increases. it Is also well known that the vapor pressure of mercury Is determlned by the bulb wall tem-perature In the bulb body (envolope) 21. It can therefore be sald that the Intenslty of the lamp Is determlned by the bulb wall temperature.
Flg.s 5A, B and C show that an arc generated between arc supportlng electrodes 33 and 34 of palred electrodes 31 and 32 curves dlfferently dependlng upon the dlfferent llghtlng angles of the lamp. As Is apparent from Flg.s ~A, B and C the arc Is curved dlfferently dependlng upon the posltlon of the llt lamp. The dlstance extendlng from the center of the arc, whlch Is the hlghest In temperature, to the farthest bulb Inner wall of the lamp, whlch Is the coldest portlon, thus changes dependlng upon the posltlon of the llt lamp, and the " 13Q5996 `emperature at the coldest portion of the lamp changes accordingly depending upon the position of the lit lamp.
This changing ratio becomes large particularly when VAl/VBl ~ 1.5.
Fig. 2 shows an example of the present invention.
In Fig. 2, volume VA (or hatched portion) in bulb body (envelope) 21, located between arc supporting electrodes 33 and 34 of paired main electrodes 31 and 32 is about 0.36cc and volume VB, the remaining volume in bulb body (envelope) 21 is about 0.14 cc. Therefore, VA/VB =
0.36/0.14 -. 2.5. AS shown in Figs. 2 and 3, inner wall face 2 3 of bulb body (envelope) 21 appears to be ellip-tically (Fig. 2) or circularly shaped, (Fig. 3) depending upon the angle at which bulb body (envelope) 21 is viewed. Further, groove 81 is formed at a part of inner wall fàce 23 of bulb body (envelope) 21. This groove 81 ls created when bulb body (envelope) 21 is crush sealed. It is assumed that the distance extend-ing from line A which extends between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 to innsr wall face 23 of bulb body (envelope) 21 be L2 and that the distance extending from line A to the deepest of groove 81 be Ll. It is set in this case that Ll/L2 - 1.1.
When the lamp has this arrangement, it is obvious that remaining volume VB is smaller than the conven-tional one. Therefore, the distance extending from the .. .
~3~59~6 arc generating area where arc discharge is carried out when the lamp is turned on to inner wall face 23 of bulb body (envelope) 21 can be made shorter. The tem-perature at the coldest portion of the inner wall of bulb body (envelope) 21 can be thus raised and it is also made possible to keep the temperature change least for its changing lighting angles. According to experi-mental data, the relative value of luminous efficiency at the time when the lit lamp was set horizontal (the lo arc becomes vertical) was about 95, providing that the luminous efficiency was lo~ at the time when the lit lamp was set vertical (the arc becomes horizontal).
This means the changing ratio was ~ust about 5~.
Flg. 4 is a graph showing the relation between lighting angles or postures ~) of the lamp and luminous efflciencies (relative values) thereof. It can be understood from Fig. 4 that the relation between lighting angles and luminous efficiencies of the lamp changes as the rate of VA and VB changes. The lighting angle of 0 = 0 represents vertical lighting (the arc is horizontal) and the lighting angle of 0 = 90 represents horizontal lighting (the arc is vertical). As apparent from Fig. 4, the change of luminous efficiency becomes larger as the angle 0 becomes larger from 0 to 90 for each value of the VA/VB. This is because the arc does not become linear but curved depending upon the lighting ~ angle of the lamp, as described above. Further, this ; ~
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.
~3~5996 change of luminous efficiency differs greatly depending upon the rate of VA/VB. Providing that the permissible change rate for practical lamp use is 20% at maximum, Fig. 4 shows that the value of VA/VB should be between 1.5 and 5.0, that is, 1. 5 ~ VA/VB ~ 5Ø More prefer-ably, when the rate is in the range of 2.0 ~ VA/VB ~ 4.0, the changing ratio of luminous efficiency can be made smaller than 10%. When the changing ratio of luminous efficiency is made small, the changing ratio of other lamp properties such as color change can be made small.
The reason why the change of luminous efficiency becomes larger as the rate of VA and VB becomes smaller for its changing lighting postures is supposed that remalning volume VB becomes larger and temperature lrregularity at the coldest portion of inner wall 23 of bulb body (envelope) 21 is made larger by the change of the lighting posture. On the other hand, the reason why the changing ratio of luminous efficiency becomes larger as the rate of VA and VB becomes larger for its changing lighting postures is supposed that the distance between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 becomes longer and the curve of the arc is thus made more prominent to thereby lncrease heat loss.
Under mass production of the lamps, there produced those inferior lamps which satisfied the condition of 1.5 ~ VA/VB S 5.0 but whose efficiency for its different lighting angles changed more than 20%. As the result of comparing these inferior lamps with those good ones in which VA/VB is less than 10%, it has been found that the depth of groove 81 formed on inner wall face 23 of bulb body (envelope) 21 at the time of manufacture is deeper for those lamps whose luminous efficiency changes more than 20%. The method of manufacturing luminous bulb 20 includes a process of heating and melting the opening portion of a dome-like product which is made of quartz glass and then crush-sealing the opening portion by means of a pair of jigs to form a sealing section.
Groove 81 is unavoidably formed along the inner end of the sealing section when this sealing section is formed.
The depth of groove 81 differs depending upon the lamps manufactured. In order to define the depth of groove 81, it ls assumed that the distance extending from line A between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 to inner wall face 23 of bulb body (envelope) 21 be L2 and that the distance extending from line A to the deepest of groove 81 be L1. Therefore, the depth of groove 81 can be defined as the difference of these two distances or Ll - L2. Further, the rate of these two distances L1 and L2 is considered. The lighting direction property of the lamps were studied in detail changing values of Ll - L2 (or depth of groove 81) and Ll/L2. As the result, the changing ratio of lamp efficiency which depends upon the lighting i.,: -, ~3Q599~i dlrection became larger as the depth of groove 81 or Ll - L2 was made larger. When Ll/L2 met the relation of Ll/L2 ~ 1.3, the changing ratio of lamp efficiency became smaller than 20%. This percentage is in the practically permissible range.
As described above, therefore, it is possible to keep the temperature change at the coldest portion of the inner wall face of bulb body (envelope) 21 least for changing lighting postures when the rate of volume VA
in bulb body (envelope) 21 between arc supporting elec-trodes 33 and 34 of paired main electrodes 31 and 32 and volume VB remaining in bulb body (envelope) 21 except volume VA is limited to 1.5 ~ VA/VB ~ 5 at the time of manufacturing the lamps. It is also possible to prevent 1.5 those lamps which satisfy the relation of l. 5 ~ VA/VB ~ 5 but have such a groove depth as not to satisfy the rela-tion of L1/L2 ~ 1.3 from being manufactured, when the rate of the two distances relating to the depth of groove 81 is limited to Ll/L2 < 1.3 at the time of manu-facturing the lamps.
Even when the lamp lighting posture is changed fromvertical to horizontal by goo, changes of luminous effi-ciency and lamp property such as the color of light emitted can be made less than 20%. Therefore, a metal halide lamp which is smaller in size, higher in practi-cal value and free in its posture when it is lit can be produced.
13~S996 Fig. 6 is another embodiment of this invention, showing a luminous bulb 20 used in a metal halide lamp of 150 w. sulb body (envelope) 21 is made of quartz glass and formed like a substantially elliptical sphere, having a volume of 0.5 cc. Like reference numerals in Fig. 6 designate corresponding parts in the several views.
A pair of electrodes 31 and 32 are separated from and opposed one another in bulb body (envelope) 21 in the direction of the longitudinal axis (or bulb axis) of the bulb body (envelope) 21 and they are embedded in crush-melted sealing section 22 on one side of the bulh body (envelope) 21.
Each of electrodes 31 and 32 comprises base ends ~metal rods) 37 or 38 and arc supporting electrode 35 or 36 which serves to increase heat capacity, and these base ends (metal rods) 37 and 38 and coil portions 35 and 36 are made as a unit by thori.ated tungsten whose diameter is o.s mm. Arc supporting electrodes 35 and 36 of the electrodes 31 and 32 are separated from each other by about 6.8 mm and opposed to each other in the bulb body (envelope) 21 in the direction of the bulb ; axls, and base ends (metal rods) 37 and 38 thereof are connected to metal foils 41 and 42 such as Mo embedded in crush-melted sealing section 22. Metal foils 41 and 42 are connected to external iead lines 51 and 52, respectively.
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Insulating films 24 and 25 are formed on the outer face of this bulb body (envelope) 21 behind arc sup-porting electrodes 35 and 36 of the electrodes 31 and 32. These insulating films 24 and 25 are made of A~2O3, TiO2, SiO2 or the like and coated on the outer face of the bulb body (envelope) 21 behind coil portions 35 and 36 of the electrodes 31 and 32.
The areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated are formed in a conical angle 0 of 10 - 30O whose apex is the center O
of bulb body (envelope) 21, and arc supporting elec-trodes 35 and 36 of the electrodes 31 and 32 are naturally in the areas of this conical angle 0.
The luminous bulb 20 having the above-described arrangement is housed in the outer bulb 11 shown in Fig. 1 of the one side sealed type made of quartz glass.
According to this embodiment of the present invention having the above-described arrangement, arc discharge between arc supporting electrodes 35 and 36 of paired electrodes 31 and 32 are created along the direction of the bulb axis while the lamp is being lit.
Sealing section 22 formed at one side of the bulb body (envelope) 21 in a direction perpendicular to the direction of the bulb axis is thus heated by radiation heat generated by the arc discharge. Therefore, the coldest portion are formed not at sealing section 22 in 130~
the discharge space but at those portions x of the bulb body (envelope) 21 which are remote from arc supporting electrodes 35 and 36 of the electrodes 31 and 32, and the temperature at these portions x lowers depending upon the posture of the lamp lit.
However, since insulating films 24 and 25 are formed on the outer face of these coldest portions x, insulating films 24 and 25 reflect the radiation heat coming from the arc discharge and electrodes 31, 32 to raise the temperature at coldest portions x and helps the metal halide which tends to gather at these coldest portions x evaporate to raise the vapor pressure in bulb body (envelope) 21, so that the luminous efficiency and the color display of the lamp can be enhanced, pre-venting the temperature at the coldest portions x from belng lowered depending upon the posture of the lamp lit.
The areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated have a conical angle 0 of 10 - 30 respectively whose apex is the center O of bulb body (envelope) 21. This reason will be described.
The following table shows test results relating to how the luminous efficiency and the color display of the lamp changes when the areas on the bulb body (envelope) 21 whose insulating films 24 and 25 are coated are changed.
~3Q5996 As apparent from the table, the insulating effect is enhanced as the area of the insulating films 24 and 25 coated become larger. The luminous efficiency and the color display of the lamp are thus enhanced but when the area of the insulating films 24 and 25 coated becomes too large, the amount of light emitted from the lamp is lowered because light shielding effect created by the insulating films 24 and 25 becomes high.
Table Luminous Efficiency % Color Display Ra ~
Conical (Values relative to (Values relative to Angle ~lamps having no lamps having no insulating film) insulating film) 40 g5 110 It is therefore needed that the areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated are in a conical angle 0 of 10 - 30~ whose apex is center 0 of bulb body (envelope) 21.
When insulating film 24 and 25 are coated in these areas, they reflect infrared radiation to thereby heat those shoulder portions of sealing section 22 which oppose to insulating films 24 and 25, respectively.
Heat escaped through sealing section 22 can be thus ~3~S9~;
supplemented to raise the temperature at that side of sealing section 22 which faces the discharge space, thereby enhancing the luminous efficiency and the color display of the lamp.
The present invention can be applied not only to the metal halide lamp which has been described above but also to any of those discharge lamps which have a bulb body of the one side sealed type. Therefore, the present invention may be applied to the metal vapor discharge lamp such as the high pressure mercury lamp.
AS described above, the insulating films are formed on the outer face of the bulb body behind the electrodes and the areas on the bulb body whose the insulating films are coated are defined to be in the conical angle of 10 - 30 whose apex is the center of the bulb body.
Therefore, temperature rise at the coldest portions whlch may be created behind the electrodes can be acce-lerated to raise the vapor pressure of the luminous metal, thereby enabllng the luminous efficiency and the color display of the lamp to be enhanced.
More particularly, it relates to a metal halide lamp and a method of manufacturing the same.
The high intensity discharge lamp was conven-tionally used for outdoor or factory illumination but it has been used these days for illuminating the inside of structures such as the stores whose ceilings are low.
There can be often seen these cases where particu-larly the metal halide lamp is made smaller in size and attached to the low ceiling to use it as an illuminating light source because it has high luminous efficiency and color display.
One thing which has to be done to make the metal halide lame smaller in size is that the lamp used is made to consume a smaller amount of power. Another thing is that the lamp is made to have as smaller a num-ber of component parts as possible and these parts are made as smal]er in size as possible.
The second measure has been mainly studied and the development of a metal halide lamp with its one side sealed, for example, of a quartz double-bulb type, has been advanced instead of the lamp of the conventional both-side sealed type. The lamp of the both-side sealed ; 25 type has two sealed portions while the one of the one side sealed type has one sealed portion. In the case of a metal halide lamp of the quartz double-bulb type with .... . .
~3~
.
~ luminous bulb and an outer bulb. Each bulb has only one sealed portion and this therefore enables the whole of the lamp to be made smaller in size. The advantage of the luminous bulb having only one sealed portion resides in that surface ar~ ~ substantially smaller and heat loss is thu~ _s, as compared with the one of the conventio~ both-side sealed type, because the sealed portion which is a main cause of the heat loss is present only at one side of the lamp.
Further, the process of sealing the lamp can be made simpler because the sealed portion is only at one side.
However, because this luminous bulb of the one side sealed type is provided with a pair of main electrodes arranged at only one small sealed portion, the distance between front ends of these main electrodes is rela-tively small and limited to a predetermined length. In other words, this kind of luminous bulb has a larger volume behind their main electrodes compaired with the volume between the front ends of the main electrodes.
More specifically, the ratio of volume VAl located be-tween the front ends of the main electrodes relative to volume VBl defined by the remaining volume in the luminous bulb, that is, VA1/VBl, is smaller than 1.5.
Under this conditions, the temperature of the coldest portion in the luminous bulb is likely to change greatly when its lighting angle is changed because the coldest portion can be shifted because of the bending of an arc 13(1 5996 which is formed between the main electrodes.
Therefore, luminous color and efficiency can be changed greatly when a lamp changes lighting positions, limiting the extent of practical use of lamps.
The present invention provides a metal halide lamp of the one side sealed type having the least property changes for its changing lighting angles.
The present invention also provides a method of manufacturing the metal halide lamp of the one side sealed type having the least property changes for its changing lighting angles.
Further the present invention provides a metal halide lamp of the one side sealed type with less irregularity of lamp property for its changing lighting angles.
.1 ! 15 Still further the present invention provides a method of ! manufacturing the metal halide lamp of the one side sealed type with less irregularity of lamp property for its changing lighting angles. In one aspect the present invention provides a high intensity discharge lamp comprising an envelope formed of vitreous high temperature resistant material, a pair of electrodes each having a metal rod and an ar~ supporting electrode, each of the metal rods being sealed at one end of the envelope, and means for adjusting the temperature at the wall of the envelope adjacent to the arc supporting rods, to minimize the differences in the wall temperature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substantially independent of the lighting postures of the lamp.
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More specifically the invention provides a high intensity discharge lamp comprising: an envelope formed of vitreous high temperature resistant material; a pair of electrodes each having a metal rod and an arc supporting electrode, each of said metal rods being sealed at one end of said envelope; wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB
which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 <
VA/VB < 5.0; and means for adjusting the temperature at the wall of said envelope adjacent to said arc supporting rods, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substantially independent of the lighting postures of the lamp.
In a method aspect the invention provides a method of manufacturing a high intensity discharge lamp, comprising the steps of: forming an envelope of vitreous high temperature resistant material; incorporating a pair of electrodes into said envelope, each of said electrodes having a metal rod and an arc supporting electrode; sealing said metal rods at one end of said envelope; and adjusting the temperature at the wall of said envelope adjacent to said arc supporting electrodes, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency for the lamp is substantially independent of the lighting postures of the lamp, wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 < VA/VB < 5Ø
~,.......
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., :
~305996 This invention can be more fully understood from the following detailed description when taken in con~unction with the accompanying drawings, in which:-Fig. 1 shows the metal halide lamp to which a luminousS bulb of the present invention is applied;
Fig. 2 is a vertically-sectioned view showing an example of the luminous bulb according to the present invention;
Fig. 3 is a vertically-sectioned view showing the luminous bulb of Fig. 2 as it is turned round the vertical 1~ axis at an angle of 90;
Fig. 4 is a graph showing the relation between lighting angles (e) of the lamp and luminous efficiencies (relative values);
Fig. s 5~, B and C show the curves of an arc, caused by changing lighting angles of the lamp; and Fig. 6 shows another example of the luminous bulb according to the present invention.
~ n embodiment of the present invention will now be described in detail with reference to the accompanying drawings.
Fig. 1 shows a construction of the metal halide ,~
~- - 4a -., ~3~59g6 lamp to which a luminous bulb of the present invention is applied. The metal halide lamp shown in Fig. 1 includes outer bulb 11, luminous bulb 20 housed in outer bulb 11, and sealing sections 12 and 22 of these two bulbs. Outer bulb 11 is made of quartz glass and has the sealing section located on only one side thereof.
This outer bulb 11 is therefore of the one side sealed type. A base (not shown) is usually attached to sealing section 12. Luminous bulb 20 includes bulb body (envelope) 21, main electrodes 31 and 32, sealing sec-tion 22, metal foils 41 and 42, and lead lines 51 and 52. Luminous bulb 20 iS also of the one side sealed type, and sealing section 22 is formed on only one side of bulb body (envelope) 21. The volume of bulb body (envelope) 21 is 0.5 CC. A pair of main electrodes 31 and 32 each of which is made of thoriated tungsten, for example, and has a diameter of 0.5 mm, are arranged inside the bulb body (envelope) 21. Base ends (metal rods) 37 and 3a of main electrodes 31 and 32 are con-nected to metal foils 41 and 42 respectively embedded in sealing section 22. One end of each of lead lines 51 and 52 are also connected to these metal foils 41 and 42 respectively. The other end of each of luminous bulb lead lines 51 and 52 are respectively connected to metal 25 foils 61 and 62 air-tightly embedded in sealing section 12 of outer bulb 11. Further, outer bulb lead lines 71 and 72 are connected to these metal foils 61 and 62.
Mercury 26 and argon gas whlch serve as the startlng gas are sealed In bulb body (envelope) 21, and scandlum lodlde and sodlum lodlde whlch serve as the metal hallde are further sealed thereln at a ratlo of 1:5. When bulb body (envelope~ 21 Is sealed, Mer-cury 26 Is attached In the form of llquld spheres on the Innerwall thereof.
In the case of tl1e metal halIde lamp, a voltage Is , applled to the palred maln electrodes, and a dlscharge Is gener-ated In the mercury vapor between the palred electrodes to emlt llght. The Intenslty of thls llght Increases as the vapor pres-sure of the sealed mercury Increases. it Is also well known that the vapor pressure of mercury Is determlned by the bulb wall tem-perature In the bulb body (envolope) 21. It can therefore be sald that the Intenslty of the lamp Is determlned by the bulb wall temperature.
Flg.s 5A, B and C show that an arc generated between arc supportlng electrodes 33 and 34 of palred electrodes 31 and 32 curves dlfferently dependlng upon the dlfferent llghtlng angles of the lamp. As Is apparent from Flg.s ~A, B and C the arc Is curved dlfferently dependlng upon the posltlon of the llt lamp. The dlstance extendlng from the center of the arc, whlch Is the hlghest In temperature, to the farthest bulb Inner wall of the lamp, whlch Is the coldest portlon, thus changes dependlng upon the posltlon of the llt lamp, and the " 13Q5996 `emperature at the coldest portion of the lamp changes accordingly depending upon the position of the lit lamp.
This changing ratio becomes large particularly when VAl/VBl ~ 1.5.
Fig. 2 shows an example of the present invention.
In Fig. 2, volume VA (or hatched portion) in bulb body (envelope) 21, located between arc supporting electrodes 33 and 34 of paired main electrodes 31 and 32 is about 0.36cc and volume VB, the remaining volume in bulb body (envelope) 21 is about 0.14 cc. Therefore, VA/VB =
0.36/0.14 -. 2.5. AS shown in Figs. 2 and 3, inner wall face 2 3 of bulb body (envelope) 21 appears to be ellip-tically (Fig. 2) or circularly shaped, (Fig. 3) depending upon the angle at which bulb body (envelope) 21 is viewed. Further, groove 81 is formed at a part of inner wall fàce 23 of bulb body (envelope) 21. This groove 81 ls created when bulb body (envelope) 21 is crush sealed. It is assumed that the distance extend-ing from line A which extends between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 to innsr wall face 23 of bulb body (envelope) 21 be L2 and that the distance extending from line A to the deepest of groove 81 be Ll. It is set in this case that Ll/L2 - 1.1.
When the lamp has this arrangement, it is obvious that remaining volume VB is smaller than the conven-tional one. Therefore, the distance extending from the .. .
~3~59~6 arc generating area where arc discharge is carried out when the lamp is turned on to inner wall face 23 of bulb body (envelope) 21 can be made shorter. The tem-perature at the coldest portion of the inner wall of bulb body (envelope) 21 can be thus raised and it is also made possible to keep the temperature change least for its changing lighting angles. According to experi-mental data, the relative value of luminous efficiency at the time when the lit lamp was set horizontal (the lo arc becomes vertical) was about 95, providing that the luminous efficiency was lo~ at the time when the lit lamp was set vertical (the arc becomes horizontal).
This means the changing ratio was ~ust about 5~.
Flg. 4 is a graph showing the relation between lighting angles or postures ~) of the lamp and luminous efflciencies (relative values) thereof. It can be understood from Fig. 4 that the relation between lighting angles and luminous efficiencies of the lamp changes as the rate of VA and VB changes. The lighting angle of 0 = 0 represents vertical lighting (the arc is horizontal) and the lighting angle of 0 = 90 represents horizontal lighting (the arc is vertical). As apparent from Fig. 4, the change of luminous efficiency becomes larger as the angle 0 becomes larger from 0 to 90 for each value of the VA/VB. This is because the arc does not become linear but curved depending upon the lighting ~ angle of the lamp, as described above. Further, this ; ~
~, ........ ..
.
~3~5996 change of luminous efficiency differs greatly depending upon the rate of VA/VB. Providing that the permissible change rate for practical lamp use is 20% at maximum, Fig. 4 shows that the value of VA/VB should be between 1.5 and 5.0, that is, 1. 5 ~ VA/VB ~ 5Ø More prefer-ably, when the rate is in the range of 2.0 ~ VA/VB ~ 4.0, the changing ratio of luminous efficiency can be made smaller than 10%. When the changing ratio of luminous efficiency is made small, the changing ratio of other lamp properties such as color change can be made small.
The reason why the change of luminous efficiency becomes larger as the rate of VA and VB becomes smaller for its changing lighting postures is supposed that remalning volume VB becomes larger and temperature lrregularity at the coldest portion of inner wall 23 of bulb body (envelope) 21 is made larger by the change of the lighting posture. On the other hand, the reason why the changing ratio of luminous efficiency becomes larger as the rate of VA and VB becomes larger for its changing lighting postures is supposed that the distance between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 becomes longer and the curve of the arc is thus made more prominent to thereby lncrease heat loss.
Under mass production of the lamps, there produced those inferior lamps which satisfied the condition of 1.5 ~ VA/VB S 5.0 but whose efficiency for its different lighting angles changed more than 20%. As the result of comparing these inferior lamps with those good ones in which VA/VB is less than 10%, it has been found that the depth of groove 81 formed on inner wall face 23 of bulb body (envelope) 21 at the time of manufacture is deeper for those lamps whose luminous efficiency changes more than 20%. The method of manufacturing luminous bulb 20 includes a process of heating and melting the opening portion of a dome-like product which is made of quartz glass and then crush-sealing the opening portion by means of a pair of jigs to form a sealing section.
Groove 81 is unavoidably formed along the inner end of the sealing section when this sealing section is formed.
The depth of groove 81 differs depending upon the lamps manufactured. In order to define the depth of groove 81, it ls assumed that the distance extending from line A between arc supporting electrodes 33 and 34 of main electrodes 31 and 32 to inner wall face 23 of bulb body (envelope) 21 be L2 and that the distance extending from line A to the deepest of groove 81 be L1. Therefore, the depth of groove 81 can be defined as the difference of these two distances or Ll - L2. Further, the rate of these two distances L1 and L2 is considered. The lighting direction property of the lamps were studied in detail changing values of Ll - L2 (or depth of groove 81) and Ll/L2. As the result, the changing ratio of lamp efficiency which depends upon the lighting i.,: -, ~3Q599~i dlrection became larger as the depth of groove 81 or Ll - L2 was made larger. When Ll/L2 met the relation of Ll/L2 ~ 1.3, the changing ratio of lamp efficiency became smaller than 20%. This percentage is in the practically permissible range.
As described above, therefore, it is possible to keep the temperature change at the coldest portion of the inner wall face of bulb body (envelope) 21 least for changing lighting postures when the rate of volume VA
in bulb body (envelope) 21 between arc supporting elec-trodes 33 and 34 of paired main electrodes 31 and 32 and volume VB remaining in bulb body (envelope) 21 except volume VA is limited to 1.5 ~ VA/VB ~ 5 at the time of manufacturing the lamps. It is also possible to prevent 1.5 those lamps which satisfy the relation of l. 5 ~ VA/VB ~ 5 but have such a groove depth as not to satisfy the rela-tion of L1/L2 ~ 1.3 from being manufactured, when the rate of the two distances relating to the depth of groove 81 is limited to Ll/L2 < 1.3 at the time of manu-facturing the lamps.
Even when the lamp lighting posture is changed fromvertical to horizontal by goo, changes of luminous effi-ciency and lamp property such as the color of light emitted can be made less than 20%. Therefore, a metal halide lamp which is smaller in size, higher in practi-cal value and free in its posture when it is lit can be produced.
13~S996 Fig. 6 is another embodiment of this invention, showing a luminous bulb 20 used in a metal halide lamp of 150 w. sulb body (envelope) 21 is made of quartz glass and formed like a substantially elliptical sphere, having a volume of 0.5 cc. Like reference numerals in Fig. 6 designate corresponding parts in the several views.
A pair of electrodes 31 and 32 are separated from and opposed one another in bulb body (envelope) 21 in the direction of the longitudinal axis (or bulb axis) of the bulb body (envelope) 21 and they are embedded in crush-melted sealing section 22 on one side of the bulh body (envelope) 21.
Each of electrodes 31 and 32 comprises base ends ~metal rods) 37 or 38 and arc supporting electrode 35 or 36 which serves to increase heat capacity, and these base ends (metal rods) 37 and 38 and coil portions 35 and 36 are made as a unit by thori.ated tungsten whose diameter is o.s mm. Arc supporting electrodes 35 and 36 of the electrodes 31 and 32 are separated from each other by about 6.8 mm and opposed to each other in the bulb body (envelope) 21 in the direction of the bulb ; axls, and base ends (metal rods) 37 and 38 thereof are connected to metal foils 41 and 42 such as Mo embedded in crush-melted sealing section 22. Metal foils 41 and 42 are connected to external iead lines 51 and 52, respectively.
~3~s9g~ ~
Insulating films 24 and 25 are formed on the outer face of this bulb body (envelope) 21 behind arc sup-porting electrodes 35 and 36 of the electrodes 31 and 32. These insulating films 24 and 25 are made of A~2O3, TiO2, SiO2 or the like and coated on the outer face of the bulb body (envelope) 21 behind coil portions 35 and 36 of the electrodes 31 and 32.
The areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated are formed in a conical angle 0 of 10 - 30O whose apex is the center O
of bulb body (envelope) 21, and arc supporting elec-trodes 35 and 36 of the electrodes 31 and 32 are naturally in the areas of this conical angle 0.
The luminous bulb 20 having the above-described arrangement is housed in the outer bulb 11 shown in Fig. 1 of the one side sealed type made of quartz glass.
According to this embodiment of the present invention having the above-described arrangement, arc discharge between arc supporting electrodes 35 and 36 of paired electrodes 31 and 32 are created along the direction of the bulb axis while the lamp is being lit.
Sealing section 22 formed at one side of the bulb body (envelope) 21 in a direction perpendicular to the direction of the bulb axis is thus heated by radiation heat generated by the arc discharge. Therefore, the coldest portion are formed not at sealing section 22 in 130~
the discharge space but at those portions x of the bulb body (envelope) 21 which are remote from arc supporting electrodes 35 and 36 of the electrodes 31 and 32, and the temperature at these portions x lowers depending upon the posture of the lamp lit.
However, since insulating films 24 and 25 are formed on the outer face of these coldest portions x, insulating films 24 and 25 reflect the radiation heat coming from the arc discharge and electrodes 31, 32 to raise the temperature at coldest portions x and helps the metal halide which tends to gather at these coldest portions x evaporate to raise the vapor pressure in bulb body (envelope) 21, so that the luminous efficiency and the color display of the lamp can be enhanced, pre-venting the temperature at the coldest portions x from belng lowered depending upon the posture of the lamp lit.
The areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated have a conical angle 0 of 10 - 30 respectively whose apex is the center O of bulb body (envelope) 21. This reason will be described.
The following table shows test results relating to how the luminous efficiency and the color display of the lamp changes when the areas on the bulb body (envelope) 21 whose insulating films 24 and 25 are coated are changed.
~3Q5996 As apparent from the table, the insulating effect is enhanced as the area of the insulating films 24 and 25 coated become larger. The luminous efficiency and the color display of the lamp are thus enhanced but when the area of the insulating films 24 and 25 coated becomes too large, the amount of light emitted from the lamp is lowered because light shielding effect created by the insulating films 24 and 25 becomes high.
Table Luminous Efficiency % Color Display Ra ~
Conical (Values relative to (Values relative to Angle ~lamps having no lamps having no insulating film) insulating film) 40 g5 110 It is therefore needed that the areas on the bulb body (envelope) 21 where insulating films 24 and 25 are coated are in a conical angle 0 of 10 - 30~ whose apex is center 0 of bulb body (envelope) 21.
When insulating film 24 and 25 are coated in these areas, they reflect infrared radiation to thereby heat those shoulder portions of sealing section 22 which oppose to insulating films 24 and 25, respectively.
Heat escaped through sealing section 22 can be thus ~3~S9~;
supplemented to raise the temperature at that side of sealing section 22 which faces the discharge space, thereby enhancing the luminous efficiency and the color display of the lamp.
The present invention can be applied not only to the metal halide lamp which has been described above but also to any of those discharge lamps which have a bulb body of the one side sealed type. Therefore, the present invention may be applied to the metal vapor discharge lamp such as the high pressure mercury lamp.
AS described above, the insulating films are formed on the outer face of the bulb body behind the electrodes and the areas on the bulb body whose the insulating films are coated are defined to be in the conical angle of 10 - 30 whose apex is the center of the bulb body.
Therefore, temperature rise at the coldest portions whlch may be created behind the electrodes can be acce-lerated to raise the vapor pressure of the luminous metal, thereby enabllng the luminous efficiency and the color display of the lamp to be enhanced.
Claims (8)
1. A high intensity discharge lamp comprising: an envelope formed of vitreous high temperature resistant material; a pair of electrodes each having a metal rod and an arc supporting electrode, each of said metal rods being sealed at one end of said envelope; wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 ? VA/VB ? 5.0, and means for adjusting the temperature at the wall of said envelope adjacent to said arc supporting rods, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency of the lamp is substantially independent of the lighting postures of the lamp.
2. The high intensity discharge lamp according to claim 1, wherein a continuous groove is defined by a portion of said envelope located between the metal rods of said electrodes, and distance L1 between said arc supporting electrodes, on the one hand, and the bottom of said continuous groove, on the other hand, and distance L2 which is the difference between distance L1 and the depth of said groove has a relationship of: L1/L2 ? 1.3.
3. The high intensity discharge lamp according to claim 1, wherein insulating films are formed on a portion of said envelope which is located behind said electrodes.
4. The high intensity discharge lamp according to claim 3, wherein said insulating films have areas defined by a conical angle of 10°-30° the apex of which is the center of said envelope.
5. A method of manufacturing a high intensity discharge lamp, comprising the steps of: forming an envelope of vitreous high temperature resistant material; incorporating a pair of electrodes into said envelope, each of said electrodes having a metal rod and an arc supporting electrode; sealing said metal rods at one end of said envelope; and adjusting the temperature at the wall of said envelope adjacent to said arc supporting electrodes, to minimize the differences in said wall temperature under different lighting postures of the lamp, whereby the luminous efficiency for the lamp is substantially independent of the lighting postures of the lamp, wherein a space is defined by said envelope and said arc supporting electrodes, said space having a volume VA which is located between said arc supporting electrodes and has a specific relationship with volume VB which is the difference between VA and the volume of said envelope, wherein said relationship is expressed as 1.5 ? VA/VB ? 5Ø
6. The method according to claim 5, wherein a continuous groove is defined by a portion of said envelope located between the metal rods of said electrodes, and distance L1 between said arc supporting electrodes, on the one hand, and the bottom of said continuous groove, on the other hand, and distance L2 which is the difference between distance L1 and the depth of said groove has a relationship of: L1/L2 ? 1.3.
7. The method according to claim 5, wherein insulating films are formed on a portion of said envelope which is located behind said electrodes.
8. The method according to claim 7, wherein said insulating films have areas defined by a conical angle of 10 -30° the apex of which is the center of said envelope.
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62144053A JP2526065B2 (en) | 1987-06-11 | 1987-06-11 | Discharge lamp |
| JP62-144053 | 1987-06-11 | ||
| JP62-243956 | 1987-09-30 | ||
| JP62243956A JPH0787092B2 (en) | 1987-09-30 | 1987-09-30 | Metal halide lamp |
| JP63-42253 | 1988-02-26 | ||
| JP63042253A JPH01220361A (en) | 1988-02-26 | 1988-02-26 | Metal vapor discharge lamp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1305996C true CA1305996C (en) | 1992-08-04 |
Family
ID=27291137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000569220A Expired - Lifetime CA1305996C (en) | 1987-06-11 | 1988-06-10 | Single ended high intensity discharge lamp with a specific volume |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU604126B2 (en) |
| CA (1) | CA1305996C (en) |
| FR (1) | FR2616588A1 (en) |
| GB (1) | GB2206992B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0762993B2 (en) * | 1987-09-21 | 1995-07-05 | 東芝ライテック株式会社 | Metal halide lamp |
| US4998036A (en) * | 1987-12-17 | 1991-03-05 | Kabushiki Kaisha Toshiba | Metal vapor discharge lamp containing an arc tube with particular bulb structure |
Family Cites Families (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB506824A (en) * | 1900-01-01 | |||
| GB383165A (en) * | 1931-05-07 | 1932-11-10 | Gen Electric Co Ltd | Improvements in electric lamps |
| GB639536A (en) * | 1946-04-17 | 1950-06-28 | Gen Electric Co Ltd | Improvements in and relating to mercury vapour lamps |
| US3621322A (en) * | 1968-09-12 | 1971-11-16 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | High-pressure compact arc lamp with electrodes containing tantalum carbide |
| NL178107C (en) * | 1977-12-23 | 1986-01-16 | Philips Nv | HIGH PRESSURE DISCHARGE LAMP. |
| JPS563962A (en) * | 1979-06-22 | 1981-01-16 | Mitsubishi Electric Corp | High-pressure metal vapor discharge lamp |
| US4342937A (en) * | 1980-02-12 | 1982-08-03 | Egyesult Izzolampa Es Villamossagi Rt. | Metal halogen vapor lamp provided with a heat reflecting layer |
| US4321504A (en) * | 1980-03-24 | 1982-03-23 | Gte Products Corporation | Low wattage metal halide arc discharge lamp |
| US4320322A (en) * | 1980-03-24 | 1982-03-16 | Gte Products Corporation | Electrode geometry to improve arc stability |
| GB2103872A (en) * | 1981-07-22 | 1983-02-23 | Gen Electric Co Plc | Electric discharge lamp seals |
| DE3232207A1 (en) * | 1982-08-30 | 1984-03-08 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH, 8000 München | HIGH PRESSURE DISCHARGE LAMP WITH LOW POWER |
| US4557700A (en) * | 1983-06-09 | 1985-12-10 | Gte Products Corporation | Metal halide discharge lamp gas fill process to provide minimal color separation |
| DE3537872A1 (en) * | 1985-10-24 | 1987-04-30 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | HIGH PRESSURE DISCHARGE LAMP |
| DE8623905U1 (en) * | 1986-09-05 | 1988-02-25 | Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH, 81543 München | High pressure discharge lamp |
| JPH0762993B2 (en) * | 1987-09-21 | 1995-07-05 | 東芝ライテック株式会社 | Metal halide lamp |
-
1988
- 1988-06-09 AU AU17524/88A patent/AU604126B2/en not_active Ceased
- 1988-06-10 FR FR8807814A patent/FR2616588A1/en not_active Withdrawn
- 1988-06-10 CA CA000569220A patent/CA1305996C/en not_active Expired - Lifetime
- 1988-06-10 GB GB8813736A patent/GB2206992B/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| FR2616588A1 (en) | 1988-12-16 |
| AU604126B2 (en) | 1990-12-06 |
| AU1752488A (en) | 1989-01-19 |
| GB8813736D0 (en) | 1988-07-13 |
| GB2206992A (en) | 1989-01-18 |
| GB2206992B (en) | 1992-01-08 |
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