CA1212980A - Low pressure discharge lamp - Google Patents
Low pressure discharge lampInfo
- Publication number
- CA1212980A CA1212980A CA000448195A CA448195A CA1212980A CA 1212980 A CA1212980 A CA 1212980A CA 000448195 A CA000448195 A CA 000448195A CA 448195 A CA448195 A CA 448195A CA 1212980 A CA1212980 A CA 1212980A
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- CA
- Canada
- Prior art keywords
- inner tube
- end plate
- outer bulb
- discharge lamp
- tube
- 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.)
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Abstract
ABSTRACT OF DISCLOSURE
A low pressure discharge lamp of double tube structure comprises an outer bulb containing therein a sealed gas and having one end closed and at least one inner tube supported by an end plate to communicate with the interior of the outer bulb; receiving therein electrodes and restricting an electric dischargeing path.
The ends receiving therein the electrodes of the inner tube are bonded with an adhesive on the surface on the side facing the outer bulb of the end plate and a part of each end other than said ends of said inner tube is in contact to and supported by the end plate. The construction makes bonding operations of the inner tube to the end plate easy and provide a stable condition to the inner tube in an lamp assemblage and reduces lamp weight.
A low pressure discharge lamp of double tube structure comprises an outer bulb containing therein a sealed gas and having one end closed and at least one inner tube supported by an end plate to communicate with the interior of the outer bulb; receiving therein electrodes and restricting an electric dischargeing path.
The ends receiving therein the electrodes of the inner tube are bonded with an adhesive on the surface on the side facing the outer bulb of the end plate and a part of each end other than said ends of said inner tube is in contact to and supported by the end plate. The construction makes bonding operations of the inner tube to the end plate easy and provide a stable condition to the inner tube in an lamp assemblage and reduces lamp weight.
Description
The present invention relates to a low pressure discharge lamp having an inner tube to restrict a discharge pa-th in an outer bulb forming a discharge space.
The presen-t invention will be illustrated by wa~
of the accompanying drawings in which:
Figure 1 is an exploded perspective view of a con-ventional low pressure discharge lamp;
Figure 2 is an exploded perspective view of an embodimen-t of the low pressure discharge lamp according to the present inven-tion;
Figure 3 is a diagram showing the first stage of preparation of an inner tube shown in Figure 2;
Figure 4 is a diagram showing the second stage of preparation oE the inner tube in Figure 2;
Figure 5 is a diagram showing the final s-tage of prepara-tion of the inner tube in Figure 2;
Figure 6 is an e~ploded perspective view of ano-ther embodiment of the low pressure discharge lamp according to the present invention;
Figure 7 is a cross sectional view partly omitted of the other embodiment of the discharge lamp of the presen-t invention;
Figure 8 is a cross sec-tional view of an important part of still another embodiment of the present invention;
Figure 9 is a cross sectional view showing modifica-tion of the embodimen-t in Figure 8; and z~
~ igure 10 is a cross sectional view of a separat~
enlbodiment of the discharge lamp of the present invention.
A variety of proposals have been made on this kind oE discharge lamp to substitute it for an incandescent lamp because the discharge lamp allows its size-reduction into a compact form. The discharge lamp disclosed in Japanese Un-e~amined Patent Publication No. 44956/1982 is shown in Fig-ure 1 as an example, in which there are provided two elec-trodes 3, 3 passing through an end plate 2 closing -the lower opening portion of an ou-ter bulb 1, extending in the outer bulb 1 and each one end oE inner tubes 4, formed into a U-shape, is fitted to each projection 11 through which each of -the electrodes 3 passes, on account of which cross-talk discharge possibly occurring between the electrodes 3 is preven-ted~ The other open end of -the inner tubes 4 is in contact with the upper surface of the end plate 2 and near each of the open ends, a recess 5 for causing bridge of electric discharge is formed. On the other hand, the inner -tubes 4 are held by a pressing plate 10 fi-tted to the upper end of a supporting rod 9 secured to the end plate 2 so that bo-th -the open ends are in contact with the end pla-te 2. The inner wall o~ the inner tubes 4 is coated wi-th a layer of fluorescent material.
In the discharge lamp having the cons-truction de-scribed above, since the supporting rod 9 and the pressiny pla-te 10, both needed to secure the inner tubes 4 are incor-porated in the lamp as additional par-ts, there are problems of increasing the number of parts; causing additional man-agement for these parts, complicated structure of the lamp and increasing manufacturing steps.
The present invention eliminates the disadvan-tage of the conventional discharge lamp and provides a low pressure discharge lamp having double tube structure compris-~. - 2 ,:"~
~2~LZ~
incJ an ou-ter bulb and at least one inner tube, in ~Afhich each open end part at the side of covering an electrode of the inner tube is bonded with an adhesive to an end plate at a position facing the outer bulb and the other open end par-t, which does no-t cover the electrode, of the inner -tube is made in contac-t with the end pla-te thereby eliminating problems of complicated management of par-ts; complicated manufacturing steps and increase in weight of the discharge lamp, all resulting from use of additional parts to secure -the inner tube.
The present inven-tion fur-ther provides a low pressure discharge lamp having double tube structure, in which an outer bulb, at least one inner tube and a fine pipe for air discharge are bonded with an adhesive on a sur-face of an end plate facing the outer bulb whereby manu-facturing work can be simplified, damage of parts -to be bonded or bonding portions can be prevented and reliability on air -tight can be increased.
According to one aspec-t thereof the present inven-tion provides a low pressure discharge lamp of double tube ; structure comprising an outer bulb containing therein a sealed gas and having one,end closed by an end plate and at least one inner tube supported by an end plate to communi-ca ~ fa W i. th -the interior of said outer bulb; receiving -therein e.lectrodes and restricting an electric di.scharging path, characterized in that the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing sa:~d outer bulb of said end plate and a par-t of each enfd other than sai.d ends of sai.d i.nner l-ube is in contact-to and supporte(lhy said e~ld l):late.
Sui.tably, said innex tube compri.sf-s a p.l.uralit.y of li.gh-t transmitting tubes each having at least one opening communi.cated with said bnlb and said tubes are con--: - 3 'i ~Z~Z93~3~
nected by melt-bonding at a part of the edge portion of said opening.
In ano-ther aspect thereof the presen-t invention provides a low pressure discharge lamp of double tube struc-ture comprising an outer bulb containing therein a sealed gas and having one end closed and at least one inner tube supported by an end pla-te to communicate with the interior of said outer bulb; receiving therein electrodes and re-stricting an electric discharging path, characterized inthat the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing said outer bulb of said end plate and said outer bulb and a fine tube for air discharge are bonded with an adhesive in said end plate at positions facing said : ollter bulb.
: .~uitably, said inner tube, outer bulb ancl fi.ne tube for air discharge are bonded with an adhesive at respecti.ve grooves formed in said end plate. Preferably, a flange is fvrmed in si.ad fine tube for air di.scharge at its end portion extending to said outer bulb. Desirably, said electrodes are bonded with an adhesive on said end plate through respective electrode supporters.
An emhodi.men-t of -the present invention will be described wi.th reference to Figure 2.
A reference numeral 1 designates a cyli.ndrical ~ ~ - 4 .,- ~
~2~æ~
outer bulb made of glass having a domed top and an opened bottom and numeral 2 refers -to an end plate made of metal or ceramics for closing the opened bottom of -the ou-ter bulb 1 to make it in air tight condition. There is enclosed a medium for discharge consisting of a predetermined amount of mercury and a rare gas such as argon in a sealed space formed by the end plate 2 and the ou-ter bulb 1. Numerals 3, 3 designates electrodes both being seal-bonded to the end plate 2 to ex-tend in-to the outer bulb 1 and a numeral 4 in-dica~es an inner tube made of glass which is -to be arranged in -the outer bulb 1 to restrict a discharge path. The inner tube 4 is formed in one piece by melt-bonding each of legs of two glass tubes bended to be a U-shape. Namely, free ends of -the inner tube 4 are bonded with an adhesive of ylass frit 8 to a ~ - 4a ",. ~, .-- 5 --surface of the end plate 2 in an air-tight fashion to respectively cover the electrodes 3, 3 so that no cross-talk electric discharge takes place between t'ne electrodes 3, 3. On the other hand, the other ends of the inner tube 4 is bridged by forming t'nerebetween a connecting part 6 by melt-bonding the vicinity of the open ends ~ of the two U-shaped glass tubes so that the end part thus connected is brought to in contact with`the surface of the end plate 2. A substantially semi-circular opening 5 formed by obliquely cutting the glass tube from its open end is provided in each side portion of the glass tubes facing each other.
Simple explanation will be made as to assembling work for the embodiment shown in Figure 2.
First of all, an adhesive 8 is applied to a predetermined por~ion on the end plate 2.
U-shaped glass tubes placed in juxta-position each other are made in one piece by means of the connecting part 6. Thus formed single inner tube 4 is set up on the
The presen-t invention will be illustrated by wa~
of the accompanying drawings in which:
Figure 1 is an exploded perspective view of a con-ventional low pressure discharge lamp;
Figure 2 is an exploded perspective view of an embodimen-t of the low pressure discharge lamp according to the present inven-tion;
Figure 3 is a diagram showing the first stage of preparation of an inner tube shown in Figure 2;
Figure 4 is a diagram showing the second stage of preparation oE the inner tube in Figure 2;
Figure 5 is a diagram showing the final s-tage of prepara-tion of the inner tube in Figure 2;
Figure 6 is an e~ploded perspective view of ano-ther embodiment of the low pressure discharge lamp according to the present invention;
Figure 7 is a cross sectional view partly omitted of the other embodiment of the discharge lamp of the presen-t invention;
Figure 8 is a cross sec-tional view of an important part of still another embodiment of the present invention;
Figure 9 is a cross sectional view showing modifica-tion of the embodimen-t in Figure 8; and z~
~ igure 10 is a cross sectional view of a separat~
enlbodiment of the discharge lamp of the present invention.
A variety of proposals have been made on this kind oE discharge lamp to substitute it for an incandescent lamp because the discharge lamp allows its size-reduction into a compact form. The discharge lamp disclosed in Japanese Un-e~amined Patent Publication No. 44956/1982 is shown in Fig-ure 1 as an example, in which there are provided two elec-trodes 3, 3 passing through an end plate 2 closing -the lower opening portion of an ou-ter bulb 1, extending in the outer bulb 1 and each one end oE inner tubes 4, formed into a U-shape, is fitted to each projection 11 through which each of -the electrodes 3 passes, on account of which cross-talk discharge possibly occurring between the electrodes 3 is preven-ted~ The other open end of -the inner tubes 4 is in contact with the upper surface of the end plate 2 and near each of the open ends, a recess 5 for causing bridge of electric discharge is formed. On the other hand, the inner -tubes 4 are held by a pressing plate 10 fi-tted to the upper end of a supporting rod 9 secured to the end plate 2 so that bo-th -the open ends are in contact with the end pla-te 2. The inner wall o~ the inner tubes 4 is coated wi-th a layer of fluorescent material.
In the discharge lamp having the cons-truction de-scribed above, since the supporting rod 9 and the pressiny pla-te 10, both needed to secure the inner tubes 4 are incor-porated in the lamp as additional par-ts, there are problems of increasing the number of parts; causing additional man-agement for these parts, complicated structure of the lamp and increasing manufacturing steps.
The present invention eliminates the disadvan-tage of the conventional discharge lamp and provides a low pressure discharge lamp having double tube structure compris-~. - 2 ,:"~
~2~LZ~
incJ an ou-ter bulb and at least one inner tube, in ~Afhich each open end part at the side of covering an electrode of the inner tube is bonded with an adhesive to an end plate at a position facing the outer bulb and the other open end par-t, which does no-t cover the electrode, of the inner -tube is made in contac-t with the end pla-te thereby eliminating problems of complicated management of par-ts; complicated manufacturing steps and increase in weight of the discharge lamp, all resulting from use of additional parts to secure -the inner tube.
The present inven-tion fur-ther provides a low pressure discharge lamp having double tube structure, in which an outer bulb, at least one inner tube and a fine pipe for air discharge are bonded with an adhesive on a sur-face of an end plate facing the outer bulb whereby manu-facturing work can be simplified, damage of parts -to be bonded or bonding portions can be prevented and reliability on air -tight can be increased.
According to one aspec-t thereof the present inven-tion provides a low pressure discharge lamp of double tube ; structure comprising an outer bulb containing therein a sealed gas and having one,end closed by an end plate and at least one inner tube supported by an end plate to communi-ca ~ fa W i. th -the interior of said outer bulb; receiving -therein e.lectrodes and restricting an electric di.scharging path, characterized in that the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing sa:~d outer bulb of said end plate and a par-t of each enfd other than sai.d ends of sai.d i.nner l-ube is in contact-to and supporte(lhy said e~ld l):late.
Sui.tably, said innex tube compri.sf-s a p.l.uralit.y of li.gh-t transmitting tubes each having at least one opening communi.cated with said bnlb and said tubes are con--: - 3 'i ~Z~Z93~3~
nected by melt-bonding at a part of the edge portion of said opening.
In ano-ther aspect thereof the presen-t invention provides a low pressure discharge lamp of double tube struc-ture comprising an outer bulb containing therein a sealed gas and having one end closed and at least one inner tube supported by an end pla-te to communicate with the interior of said outer bulb; receiving therein electrodes and re-stricting an electric discharging path, characterized inthat the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing said outer bulb of said end plate and said outer bulb and a fine tube for air discharge are bonded with an adhesive in said end plate at positions facing said : ollter bulb.
: .~uitably, said inner tube, outer bulb ancl fi.ne tube for air discharge are bonded with an adhesive at respecti.ve grooves formed in said end plate. Preferably, a flange is fvrmed in si.ad fine tube for air di.scharge at its end portion extending to said outer bulb. Desirably, said electrodes are bonded with an adhesive on said end plate through respective electrode supporters.
An emhodi.men-t of -the present invention will be described wi.th reference to Figure 2.
A reference numeral 1 designates a cyli.ndrical ~ ~ - 4 .,- ~
~2~æ~
outer bulb made of glass having a domed top and an opened bottom and numeral 2 refers -to an end plate made of metal or ceramics for closing the opened bottom of -the ou-ter bulb 1 to make it in air tight condition. There is enclosed a medium for discharge consisting of a predetermined amount of mercury and a rare gas such as argon in a sealed space formed by the end plate 2 and the ou-ter bulb 1. Numerals 3, 3 designates electrodes both being seal-bonded to the end plate 2 to ex-tend in-to the outer bulb 1 and a numeral 4 in-dica~es an inner tube made of glass which is -to be arranged in -the outer bulb 1 to restrict a discharge path. The inner tube 4 is formed in one piece by melt-bonding each of legs of two glass tubes bended to be a U-shape. Namely, free ends of -the inner tube 4 are bonded with an adhesive of ylass frit 8 to a ~ - 4a ",. ~, .-- 5 --surface of the end plate 2 in an air-tight fashion to respectively cover the electrodes 3, 3 so that no cross-talk electric discharge takes place between t'ne electrodes 3, 3. On the other hand, the other ends of the inner tube 4 is bridged by forming t'nerebetween a connecting part 6 by melt-bonding the vicinity of the open ends ~ of the two U-shaped glass tubes so that the end part thus connected is brought to in contact with`the surface of the end plate 2. A substantially semi-circular opening 5 formed by obliquely cutting the glass tube from its open end is provided in each side portion of the glass tubes facing each other.
Simple explanation will be made as to assembling work for the embodiment shown in Figure 2.
First of all, an adhesive 8 is applied to a predetermined por~ion on the end plate 2.
U-shaped glass tubes placed in juxta-position each other are made in one piece by means of the connecting part 6. Thus formed single inner tube 4 is set up on the
2~ surface of the end plate 2 with its four lower surfaces without any supporting aid. Then, the outer bulb 1 is sealed by the end plate 2.
In the assembling work as above-mentioned, it is unnecessary to use a jig for supporting the inner tube for the purpose of bonding the inner tube 4 to the end plate 2 with the adhesive of glass frit 8, as required in the conventional processes to secure an inner tube 4 . 6 --consisting of a single U-shaped glass tub~, whereby the assembling work can be remarXably simplified. Further, since the four lower surfaces of the inner tube 4 of the present invention are all in contact with the end plate surface, the inner tube 4 stands in a stable manner even though an impact force is applied to the assembly or a incomplete lamp in the later stage of the assembling wor~
or in the transportation of the lamp.
Incidentally 7 since the inner tube supporting rod as shown in Figure 1 is not required because the inner tube 4 is attached by bonding operation, the number of parts needed can be reduced, hence -the number of the manufacturing steps can be reduced and accordingly, management for the parts is easy and manufacturing process is simplified.
The supporting rod 9 and the pressing plate lO used in the conventional lamp as shown in Figure l have been made oE metal. In the discharge lamp of this kind which is required to reduce its weight for the purpose of substituting the discharge lamp for an incandescent lamp, if the supporting rod 9 and the pressing plate 10 can be eliminated, the total weight of the lamp can be reduced.
In the next place, a method of preparation of the inner tube 4 of the embodiment shown in Figure 2 will be described~ The inner tube 4 is prepared according to steps as shown in Figure 3. Two glass tubes A, A each - having a U-shaped portion are placed in juxta-position .
z~
with respect to two legs Al, Al and A~, A2 facing each other and with their open ends directing upwards; the upper portions of the respective legs A2, A2 are simultaneously heated by a burner C from the open end to the just lower portion to cause them to be molten; after a short time period, a part of the top of the respective legs A2, A2 deforms due to wind pressure of the flame from the burner C to Eorm a semi-circular opening 5 as if cut obliquely from the open end and a mass of molten glass 52 is formed at the peripheral portion 51 of the opening 5 as shown in Figure 4 (The molten glass mass is formed at the lower part of the peripheral portion in view of Figures 3 to 5, but at the upper part when the inner tube 4 is set up on the end pla.te 2.); the molten glass mass of both the glass tubes A, A are brought into contact each other; then, the glass tubes A, A are slightly apart from each other to form a connecting part 6; thus the preparation of the inner tube 4 is completed (Figure 5). It is advantageous that a fluorescent layer 7 to be coated on the inner wall of the inner tube 4 is formed after the preparation of the inner tube 4 because the connecting part 6 can be easily formed. In the discharge lamp of the present invention, since the connecting part 6 is formed at the same time of the formation of the opening 5 as a recess to cause a brid~e of electric discharge when the inner tube 4 is to be prepared, the number oE steps for heating and annealing the glass tube are reduced.
The shape of the opening 5 to be formed in the inner tube 4 is not limited to a semi-circular one whicn is formed by obliquely cutting the leg from the open end, but can be a circular shape which may be formed at the intermediate of the leg of the inner tube 4. In this case, the circular opening 5 can be obtained by blowing a flame oli~uely from the outside at a high temperature such as oxygen gas flame to a position where an opening is to be formed in the leg.
The shape of the inner tube 4 is variab-le; for example, the inner tube is formed in such a manner that a glass tube in a U-shape is again subjected to bending operation into a saddle shape to form a plurality of U-shaped portions. Then, the electrodes are covered by the respective ends of the glass tube and the lower side surfaces of the plurality of U-shaped portions are brought into contact with the end plate.
~ It is considered that in addition to the inner tube bonded to the end plate with an adhesive, the outer bulb and the fine tube for air discharge are also bonded to the end plate with an adhesive.~ In this case, bonding operations are carried out by putting an adhesive of glass frit in either a molded form or paste on predetermined portions; putting a body to be bonded such as an outer bulb on the glass frit or directly putting _ 9 _ the body on, for example, the end plate, followed by coating a paste-like glass frit around the contacting area of the body, and then applying heat to the glass frit until the glass frit reaches a predetermined tempera-ture for melt-bonding.
In the discharge lamp having many portions to be bonded with an adhesive such as glass frit, it is essential to reduce the number of bonding operations to simplify manufacturing work. Further, when the inner tube, the outer bulb and the fine tube for air discharge are separately bonded, a part having been bonaed or bonding portion may be broken- or air-tight property may be impaired due to thermal stress caused by application of heat in the bonding operations conducted later.
As measures to solve such drawback, there is another embodiment of the present invention which will be described with referece to Figure 6 and 7. In Figure 6, the same reference numerals as in Figure 2 designate the same or corresponding parts and therefore~ the description is omitted~
Figure 6 shows a discharge lamp in which there are provided two inner tubes 4, 4 each having an upper open end and the lower end bonded to the end plate 2 with an adhesive 8 such as glass frit and each enlosing therein an electrode 3. The reference numeral l~ designates a fine tube for air discharge which has one end communicated with the interior of the outer bulb l for the purpose of evacuation of air. The fine tube 12 is fitted into an insertion hole 21 for fine tube formed in the end plate 2 as shown in Figure 7.
The construction of the end plate 2 will be described in more detail with reference to Figure 7.
The insertion hole 21 for fine tube is provided between the electrodP 3, 3 in the end plate 2 and a recess 22 having relatively large diameter is formed in the surface at the side of the electrodes-, of the end plate 2. Annular grooves 23 are formed around the electrodes 3 in the end plate 2 so as to have a diameter corresponding to the inner tube 4. Separate annular grooves 24 are formed near the edge of the end plate 2 on the same side as the annular grooves 23 as above-mentionPd so as to have a diameter corresponding to the outer bulb 1. In these grooves 22, 23 and 24, the adhesive 8 of glass frit is applied.
Assembling operations for the discharge lamp having the construction described above will be explained.
First of all, the adhesive 8 of paste-like glass frit is applied to each of the grooves 22, 23 and 24 in the end plate 2. The fine tube 7 for air discharge is inserted into the insertion hole 21 for fine tube. The inner tube 4 is put on the glass frit 8 in the groove 23.
In the same manner, the outer bulb 1 is put on the adhesive 8 in the groove 24. Thus combined product is subject to preliminary drying and then it i5 passed through a heat oven to cause melt-bonding of 'che adhesive 8 of glass frit followed by solidification; thus, the bonding operation is completed.
Since the grooves 22, 23 and 24 to which the outer bulb 1, the inner tube ~ and the fine tube 12 for air discharge are bonded are all provided on the single surface of the end plate 2, which is covered by the outer bulb 1, the assembling work such as application of the adhesive ~ of glass frit~ putting or inserting the outer bulb (1), the inner tube 4 and the ~ine tube 12 and so on are all carried out on the same surface side without requirement of necessity of separate operations for the outer bulb (1) or the inner tube 4 etc. In this way, the assembling operation is simplified.
It is known that when a glass frit as an adhesive is heated, it becomes molten state to exhibit fluidity. In the present invention, however, since the grooves 22, 23, 24 to which the glass frit is applied are formed in the same surface of the end plate 2, there is no risk of flowing the glass frit from any of grooves 22, 23, 24.
In the embodiment, it is unnecessary to separately carry out bonding operations on account o~ which a part having been bonded is not damaged due to thermal stress caused by bonding operations to the other part and excellent mechanical strength and air-tight property can be obtained.
25~
Description will b~ made as to another embodiment of the present invention.
Although the fine tube 7 for air disc'narge of generally cylindrical shape is used in the embodiment as shown in Figures 6 and 7, it can be one which has an external flange 121 at one end of the fine tube whic'n extends in the outer bulb 1 as shown in Figures 8 and 9.
This structure of the fine tube 12 eliminates an auxiliary means to support the fine tube 12 for air discharge.
For a separate embodiment of the construction for the electrodes 3, 3 and the end p-late 2, it is possible, as shown in Figure 10, to provide supporters 31, 31 made of glass or ceramics to support the electrodes 3, 3 and bond the supporters 31, 31 with the glass frit on the end plate surface facing the outer bulb as with the other elements. Further, it is always unnecessary to apply the glass frit in -the grooves 22, 23, 24 as shown in Figure 10 .
Use of the glass frit as an adhesive is made not only in paste form as described above but also in a predetermined molded form to a part or the entire portion of the end plate 2.
In the embodiments shown in Figures 6 to 10, it is, 2~ of course, possible to use the inner tube 4 in which two U-shaped glass tubes are combined into one piece as shown in Figure 2, or in which a single U-shaped tube is bent into a saddle form.
In the assembling work as above-mentioned, it is unnecessary to use a jig for supporting the inner tube for the purpose of bonding the inner tube 4 to the end plate 2 with the adhesive of glass frit 8, as required in the conventional processes to secure an inner tube 4 . 6 --consisting of a single U-shaped glass tub~, whereby the assembling work can be remarXably simplified. Further, since the four lower surfaces of the inner tube 4 of the present invention are all in contact with the end plate surface, the inner tube 4 stands in a stable manner even though an impact force is applied to the assembly or a incomplete lamp in the later stage of the assembling wor~
or in the transportation of the lamp.
Incidentally 7 since the inner tube supporting rod as shown in Figure 1 is not required because the inner tube 4 is attached by bonding operation, the number of parts needed can be reduced, hence -the number of the manufacturing steps can be reduced and accordingly, management for the parts is easy and manufacturing process is simplified.
The supporting rod 9 and the pressing plate lO used in the conventional lamp as shown in Figure l have been made oE metal. In the discharge lamp of this kind which is required to reduce its weight for the purpose of substituting the discharge lamp for an incandescent lamp, if the supporting rod 9 and the pressing plate 10 can be eliminated, the total weight of the lamp can be reduced.
In the next place, a method of preparation of the inner tube 4 of the embodiment shown in Figure 2 will be described~ The inner tube 4 is prepared according to steps as shown in Figure 3. Two glass tubes A, A each - having a U-shaped portion are placed in juxta-position .
z~
with respect to two legs Al, Al and A~, A2 facing each other and with their open ends directing upwards; the upper portions of the respective legs A2, A2 are simultaneously heated by a burner C from the open end to the just lower portion to cause them to be molten; after a short time period, a part of the top of the respective legs A2, A2 deforms due to wind pressure of the flame from the burner C to Eorm a semi-circular opening 5 as if cut obliquely from the open end and a mass of molten glass 52 is formed at the peripheral portion 51 of the opening 5 as shown in Figure 4 (The molten glass mass is formed at the lower part of the peripheral portion in view of Figures 3 to 5, but at the upper part when the inner tube 4 is set up on the end pla.te 2.); the molten glass mass of both the glass tubes A, A are brought into contact each other; then, the glass tubes A, A are slightly apart from each other to form a connecting part 6; thus the preparation of the inner tube 4 is completed (Figure 5). It is advantageous that a fluorescent layer 7 to be coated on the inner wall of the inner tube 4 is formed after the preparation of the inner tube 4 because the connecting part 6 can be easily formed. In the discharge lamp of the present invention, since the connecting part 6 is formed at the same time of the formation of the opening 5 as a recess to cause a brid~e of electric discharge when the inner tube 4 is to be prepared, the number oE steps for heating and annealing the glass tube are reduced.
The shape of the opening 5 to be formed in the inner tube 4 is not limited to a semi-circular one whicn is formed by obliquely cutting the leg from the open end, but can be a circular shape which may be formed at the intermediate of the leg of the inner tube 4. In this case, the circular opening 5 can be obtained by blowing a flame oli~uely from the outside at a high temperature such as oxygen gas flame to a position where an opening is to be formed in the leg.
The shape of the inner tube 4 is variab-le; for example, the inner tube is formed in such a manner that a glass tube in a U-shape is again subjected to bending operation into a saddle shape to form a plurality of U-shaped portions. Then, the electrodes are covered by the respective ends of the glass tube and the lower side surfaces of the plurality of U-shaped portions are brought into contact with the end plate.
~ It is considered that in addition to the inner tube bonded to the end plate with an adhesive, the outer bulb and the fine tube for air discharge are also bonded to the end plate with an adhesive.~ In this case, bonding operations are carried out by putting an adhesive of glass frit in either a molded form or paste on predetermined portions; putting a body to be bonded such as an outer bulb on the glass frit or directly putting _ 9 _ the body on, for example, the end plate, followed by coating a paste-like glass frit around the contacting area of the body, and then applying heat to the glass frit until the glass frit reaches a predetermined tempera-ture for melt-bonding.
In the discharge lamp having many portions to be bonded with an adhesive such as glass frit, it is essential to reduce the number of bonding operations to simplify manufacturing work. Further, when the inner tube, the outer bulb and the fine tube for air discharge are separately bonded, a part having been bonaed or bonding portion may be broken- or air-tight property may be impaired due to thermal stress caused by application of heat in the bonding operations conducted later.
As measures to solve such drawback, there is another embodiment of the present invention which will be described with referece to Figure 6 and 7. In Figure 6, the same reference numerals as in Figure 2 designate the same or corresponding parts and therefore~ the description is omitted~
Figure 6 shows a discharge lamp in which there are provided two inner tubes 4, 4 each having an upper open end and the lower end bonded to the end plate 2 with an adhesive 8 such as glass frit and each enlosing therein an electrode 3. The reference numeral l~ designates a fine tube for air discharge which has one end communicated with the interior of the outer bulb l for the purpose of evacuation of air. The fine tube 12 is fitted into an insertion hole 21 for fine tube formed in the end plate 2 as shown in Figure 7.
The construction of the end plate 2 will be described in more detail with reference to Figure 7.
The insertion hole 21 for fine tube is provided between the electrodP 3, 3 in the end plate 2 and a recess 22 having relatively large diameter is formed in the surface at the side of the electrodes-, of the end plate 2. Annular grooves 23 are formed around the electrodes 3 in the end plate 2 so as to have a diameter corresponding to the inner tube 4. Separate annular grooves 24 are formed near the edge of the end plate 2 on the same side as the annular grooves 23 as above-mentionPd so as to have a diameter corresponding to the outer bulb 1. In these grooves 22, 23 and 24, the adhesive 8 of glass frit is applied.
Assembling operations for the discharge lamp having the construction described above will be explained.
First of all, the adhesive 8 of paste-like glass frit is applied to each of the grooves 22, 23 and 24 in the end plate 2. The fine tube 7 for air discharge is inserted into the insertion hole 21 for fine tube. The inner tube 4 is put on the glass frit 8 in the groove 23.
In the same manner, the outer bulb 1 is put on the adhesive 8 in the groove 24. Thus combined product is subject to preliminary drying and then it i5 passed through a heat oven to cause melt-bonding of 'che adhesive 8 of glass frit followed by solidification; thus, the bonding operation is completed.
Since the grooves 22, 23 and 24 to which the outer bulb 1, the inner tube ~ and the fine tube 12 for air discharge are bonded are all provided on the single surface of the end plate 2, which is covered by the outer bulb 1, the assembling work such as application of the adhesive ~ of glass frit~ putting or inserting the outer bulb (1), the inner tube 4 and the ~ine tube 12 and so on are all carried out on the same surface side without requirement of necessity of separate operations for the outer bulb (1) or the inner tube 4 etc. In this way, the assembling operation is simplified.
It is known that when a glass frit as an adhesive is heated, it becomes molten state to exhibit fluidity. In the present invention, however, since the grooves 22, 23, 24 to which the glass frit is applied are formed in the same surface of the end plate 2, there is no risk of flowing the glass frit from any of grooves 22, 23, 24.
In the embodiment, it is unnecessary to separately carry out bonding operations on account o~ which a part having been bonded is not damaged due to thermal stress caused by bonding operations to the other part and excellent mechanical strength and air-tight property can be obtained.
25~
Description will b~ made as to another embodiment of the present invention.
Although the fine tube 7 for air disc'narge of generally cylindrical shape is used in the embodiment as shown in Figures 6 and 7, it can be one which has an external flange 121 at one end of the fine tube whic'n extends in the outer bulb 1 as shown in Figures 8 and 9.
This structure of the fine tube 12 eliminates an auxiliary means to support the fine tube 12 for air discharge.
For a separate embodiment of the construction for the electrodes 3, 3 and the end p-late 2, it is possible, as shown in Figure 10, to provide supporters 31, 31 made of glass or ceramics to support the electrodes 3, 3 and bond the supporters 31, 31 with the glass frit on the end plate surface facing the outer bulb as with the other elements. Further, it is always unnecessary to apply the glass frit in -the grooves 22, 23, 24 as shown in Figure 10 .
Use of the glass frit as an adhesive is made not only in paste form as described above but also in a predetermined molded form to a part or the entire portion of the end plate 2.
In the embodiments shown in Figures 6 to 10, it is, 2~ of course, possible to use the inner tube 4 in which two U-shaped glass tubes are combined into one piece as shown in Figure 2, or in which a single U-shaped tube is bent into a saddle form.
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A low pressure discharge lamp of double tube structure comprising an outer bulb containing therein a sealed gas and having one end closed by an end plate and at least one inner tube supported by an end plate to communic-ate with the interior of said outer bulb; receiving therein electrodes and restricting an electric discharging path, characterized in that the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing said outer bulb of said plate and a part of each end other than said ends of said inner tube is in contact to and supported by said end plate.
2. The low pressure discharge lamp according to claim 1, wherein said inner tube comprises a plurality of light transmitting tubes each having at least one opening communicated with said outer bulb and said tubes are con-nected by melt-bonding at a part of the edge portion of said opening.
3. A low pressure discharge lamp of double tube structure comprising an outer bulb containing therein a sealed gas and having one end closed and at least one inner tube supported by an end plate to communicate with the in-terior of said outer bulb; receiving therein electrodes and restricting an electric discharging path, characterized in that the ends, receiving therein said electrodes, of said inner tube are bonded with an adhesive on the surface on the side facing said outer bulb of said end plate and said outer bulb and a fine tube for air discharge are bonded with an adhesive in said end plate at positions facing said outer bulb.
4. The low pressure discharge lamp according to Claim 3, wherein said inner tube, outer bulb and fine tube for air discharge are bonded with an adhesive at respective grooves formed in said end plate.
5. The low pressure discharge lamp according to Claim 3, wherein a flange is formed in said fine tube for air discharge at its end portion extending to said outer bulb.
6. The low pressure discharge lamp according to Claim 3, wherein said electrodes are bonded with an adhesive on said end plate through respective electrode supporters.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000448195A CA1212980A (en) | 1984-03-01 | 1984-03-01 | Low pressure discharge lamp |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000448195A CA1212980A (en) | 1984-03-01 | 1984-03-01 | Low pressure discharge lamp |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1212980A true CA1212980A (en) | 1986-10-21 |
Family
ID=4127267
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000448195A Expired CA1212980A (en) | 1984-03-01 | 1984-03-01 | Low pressure discharge lamp |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1212980A (en) |
-
1984
- 1984-03-01 CA CA000448195A patent/CA1212980A/en not_active Expired
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| MKEX | Expiry |