CA1142358A - Photoflash lamp primer material - Google Patents
Photoflash lamp primer materialInfo
- Publication number
- CA1142358A CA1142358A CA000351560A CA351560A CA1142358A CA 1142358 A CA1142358 A CA 1142358A CA 000351560 A CA000351560 A CA 000351560A CA 351560 A CA351560 A CA 351560A CA 1142358 A CA1142358 A CA 1142358A
- Authority
- CA
- Canada
- Prior art keywords
- primer material
- primer
- combustion
- oxide
- alkali metal
- 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
Links
Abstract
PHOTOFLASH LAMP PRINTER MATERIAL
ABSTRACT OF THE DISCLOSURE
A miniature high performance flash lamp of the flashcube type is disclosed utilizing improved primer material that is more stable during manufacture of the lamp as well as during subsequent use of the lamp. Such primer material comprises a mixture of powdered zirconium fuel, a polymer binder, an oxidizer for the fuel consisting of an alkali metal chlorate or perchlorate compound, a combustion-supporting oxide and a hygroscopic additive.
An aqueous coating composition of the primer material is used to produce a dried primer ignition mass for the flash lamp which is less subject to premature ignition from either mechanical vibration or electrostatic discharge.
ABSTRACT OF THE DISCLOSURE
A miniature high performance flash lamp of the flashcube type is disclosed utilizing improved primer material that is more stable during manufacture of the lamp as well as during subsequent use of the lamp. Such primer material comprises a mixture of powdered zirconium fuel, a polymer binder, an oxidizer for the fuel consisting of an alkali metal chlorate or perchlorate compound, a combustion-supporting oxide and a hygroscopic additive.
An aqueous coating composition of the primer material is used to produce a dried primer ignition mass for the flash lamp which is less subject to premature ignition from either mechanical vibration or electrostatic discharge.
Description
5~3 -- 1 LD 776~ii PHOTOFLASH LAMP PRIMER M~TERIAI, BACKGROUND OF THE INVE21TI ()N
._ This invention relates in general to miniatura photo~lash lamps oE the all-glass type, and more particu-larly to those of the so-called electrical-i.gnition type ignited with a 1~5 vol-t dry cell.- Such photoflash lamps in general comprise a he:.metically sealed light-trans-mitting envelope usually made of soft glass which contains a combustion-supporting ga5 such as oxygen at about five or seven atmospheres, together with a filling o suitable light-producing combustible material such as shredded foil o zixconium, for example~ to produce a high intensity flash o actinic light. A stem press ~ase is located at one end o~ the lamp envelope to form a hermetic seal with a pair of ~ electrical lead-in w.ires having a refractory metal resistance filament connected therebetween. In such electrical~ignition type photoflash lamps now being used, the inner ends of these wires are coated with a charge oE heat-sen~itive primer material so that when electrical current is passed through the resistant ~ilament, there will be deElagration o the primer material cau~ing the shredded combustible foil in the lamp envelope to burn rapidly with incandescence. Two lamps of this general type in current manuacture with soft glass ~or ~lashcube-type product applications and called AG-l or AG-3, are more particularly described in IJ.S. Patent 3,506,385, assigned to the assi~nee o~ the present invention.
- ~ - LD 7766 A primer ignition material for use with a high-voltage type flash lamp which can be deposited from an a~ueous coa~ing composition is disclosed in UOS. Patent 3~972,673, also assigned to the present assignee~ Said ignition pri~er material includes a combustion-supporting oxide to provide an additional oxygen ~ource in the primer material which is readily available for combustion of the primer fuel when the primer mixture is ignited~ Preferred combustion supporting oxides are cobalt oxide, barium chromateJ iron oxide ana higher oxides of nickel which are easily reduced by zirconium fuel in the primer mîxture to lower non-conducting oxides but which resist further dissociation forming conductive residues after the lamp has been flashed. Where formation of such conductive residues is not objection~ble, however, still other metal oxides are disclosed which can be reduced by the fuel metal upon primer ignition including copper oxide, lead oxide, tin oxide, titanium oxide, and zinc oxide as well as still oth~rs. Utilization of said combustion supporting oxide~ in this type primer ignition matexial enhances reliable ignition of the overall high voltage flash lamp to produce th~ desired light output in a relatively short time period.
A comparison o the ignition characteristics for such flash lamp between primer materials applied from an aqueous suspension as compared with the sama primer materials applied from organic liquid suspension finds the latter primers to ignite more rapidly which is desirable.
Since the relative speed of primer ignition influences the rate at which light i9 generated by the flash lamp, it follows that such water-based primer materials could prove too slow to ignite for acceptable use although safer to handle in lamp manufacture than primer materi~ls applied from organic liquid suspen~ion. It is a desirab1e objective, therefore, to improve the speed of ignition for prim~r materials which can be applied from an aqueous liquid suspension~ , It is another desirable objective to improve the stability of primer materials used in said flash lamps so that the flash lamps are less prone -to prematur~
ignition from either mechanical vibration or electros~atic charges.
SUMMARY OF THE INVENTION
_.
An improved primer material has now been discovered which can be applied reliably as a coating for the lead-in conductors of an electrical-ignition flashcube type flash lamp from a water-based suspension having none o the foregoing drawbacks. Specifically, it has been ound tha~ incorporation of a hygroscopic agent ;n the aqueous suspension of said primer material provides a dried product con~a.ining sa.id additive which ignites more rapidly and is also less prone to premature ignition than when a primer material no~ containing said addi-tive has been deposited from an organic liquid suspension. The primer material havi~g the desired characteristics compxise~
a mixture of powdered zirconium fuel, a polymer binder, an oxidizer for said fuel selected from an alkali metal chlorate ox pe~chlorate compound, a com~ustion-supporting oxide, and said hygroscopic additive. In its preferred embodiments, the primer material utilizes a combustion-supporting oxide selected from cobalt oxide, barium chromate, 'ron oxide, and higher oxides of nickel to avoid any electrical short-circuited condition in the lamp ater Elashing created by a conductive primer residue. An alkali metal chlorate compound is also preferred as the oxidizer in the present primer material by xeason of being water-soluble to provide more uniform distribution in the dri.ed primer ignition mass than an alkali metal perchlorate compound which is les~
water-soluble. In said preferred dried primer mixtures, the proportion of oxidizer is approxi.mately 4-12% by 35~
weight with the hygroscopic agent also being present in the same weight range (4-12%). Polyvinyl alcohol and polyvinyl pyrrolidone are preferred organîc binders ~or the aqueous coating composition since both provide a S tough and adherent coating of the dried primer mass in the flash lamp.
A suitable hygroscopic agent can be selected from a wide variety of known materials which absorb water without becoming liquified. More particularly, said hygroscopic additive must be capable of preferentially absorbing mois~ure from the fuel and oxidizer constituents in the deposited mixture after drying to enhance ~he speed of primer igni~ion. Rnown hygroscopic addi~ives include such diverse materials as cobaltous cobaltic cyanide, boric oxide, and calcium sulfate which all can be distributed uniformly in the present aqueous primer suspensions ei-~her as a powdered solid or dissolvsd in said suspensions~ The preferred hygroscopic additive is cobaltous cobaltic cyanide since said material may provide a source of combustion supportin~ oxide when the primer is ignited and thereby support more thorough and rapid combustion.
BRIEF DESCRIPTION OF THE DRAWING
In the accompanying drawing, the single figure represents a cross section view partly in elevation of a preferred flash lamp utilizing the present invention~
DESCRIPT~ON OF THE PRRFERRED EMBODIMENTS
A preferred flash lamp construction is depicted compr.ising a glass bulb or envelope 1 which is shown may be formed of a short lengthened glass tubing, for example, about 0.340 inch outside diameter which is constricted and rounded off at one end as indicated at 2 and closed off thereof by an exhaust tube 3 and is ~ormed at the other or base end 4 with a stem press base. A flashcube type lamp having this general conEigurat.ion and in commercial production is the previously rPferenced AG-l which produces approximately 7,000 lumen-seconds light output for a 1.1 cubic centimeter internal volume The lead-in wires 6 are sealed in opposi-te corners 7 of the stem press base which provides a longer path length of the in-leads through the lamp envelope and less likelihood o~ leakage or loss o a hermetic seal~ The glass and metal in-lead compositions ~or said flash lamp are dictated by the desired ligh~ output characteristics and some high performance flash lamps utilize a borosilicate glass in combination with alloy in-leads of iron, nickel, and cobalt. The inner ends of said in-leads axe coated with the primer material 8 and have an electrical filament 9 connected therebetween. This filament is a re~ractory metal such as tungsten or a tungsten alloy. A quantity of ~ilamentary combustible material 10 such as a shredded foil of zirconium or hafnium, for example, is distributed within the interior space of the envelope 1 which also contains a ~illin~ of a suitable combustion supporting gas such as o~ygen, generally a-t high pressures in excess of several atmospheres.
The solid coating of primer material in the above embodiment is applied to the lead-in conductors from an aqueous suspension of the present invention in various known ways. For example, the in-lead members can be dipped into the aqueous slurry followed by drying in air or wi-th heat to remove the liquid and form a solid adherent coating having the desired characteristics above de~cribed.
Alterna~.ely, the aqueous slurry can be sprayed on the in-lead members and thareafter processed to provide a solid coating exhibi~ing comparable performance.
AS an example of a suitable aqueous coating composition, there is initially prepared the fuel portion of said primer mixture as an aqueous suspension containing 80 parts milled zirconium, 10 parts barium chromate, 10 parts cobalt oxide, 5 parts cobaltous cohaltic cyanide, 3s~
~ 6 ~ I,D 7766 and ~ pa:rts polyvinyl pyrrolidone binder. To said aqueous fuel suspension there is added with mixing an aqueous oxidizer solution of sodium chlorate in various amounts so that the dried primer ml~ture cont~ins from 4-12 percent ox.idi~er by weight. ~ solid coating of sa.id primer material .is applied to both in-leads of the above type lamp construction in the conventional manner.
Performance tests were conducted on -the above described flash lamp embodiments to evaluate the effectiveness of the hygroscopic additive in providing light output improvement. Spec.iicallyt flash lamps utilizing a water~based primer containing said hygroscopic ~dditive were ~lashed for comparison with flash lamp performance when said additive was not used and :~urther compared with flash lamp performance when the same la-tter primer solids had been deposlted from a conventi.onal organic liquid suspension. Sample lo-ts o~ 50 lamps were flashed duriny said performance tests by application of an electrical pulse of 1.5 volts and 0.8 ampere during a ~0 0.7 second time interval. The sample lot of flash lamps using primer not containlng said hygroscopic additive and deposited ~rom an amyl aceta-te liquid susper.sion demonstrated a 76% flashabili-ty rate. The flashability rate of :Lamps utilizing the water-based primer suspensions is reported in the table below for various oxidizer levels in the primer mixture.
Flashahility o~ Flashability of Oxiclizer Content Primer with 5% Primer without (B~ We.ight) _ Additive (By Weight~ Additive 5% 96% 78%
7~ 84% 72%
9~ ~2~ 72~
'rhe above tes-t results demonstrate an average increase in lamp flashability from 74% to 91% at the indicated test condi.tions when said water-based primer materials contain ci8 - 7 - I.D 7766 cobaltic cobaltous cyanide addi-tive, Further observations conducted during flash lamp manufacture with said water-based primers indicated a significant reduction in premature flashing from mechanical vibration and elec-tro-static discharge as compared with lamp manufactura usingsaid conven-tional amyl acetate primer suspension.
It follows from the foregoing disclosure that various changes and modifications may be made in the above described improved primer material without departing from ~he spirit and scope of the invention. For example, it will be apparent that other fuel compositions can be employed in said primer mixture, such as red phosphorus to still provide comparable electrical ignition charac-teristics. Additionally, it is contemplated to vary the weight proportions of the specific cons-tituents in the primer mix-ture above specifically disclosed depending upon the performance requirements desired in a particular flash lamp construction with respect to light OUtpllt level and flash duration, Consequentlyl it is intended to limit the presen~ invention, therefore, only by the scope of the following claims.
._ This invention relates in general to miniatura photo~lash lamps oE the all-glass type, and more particu-larly to those of the so-called electrical-i.gnition type ignited with a 1~5 vol-t dry cell.- Such photoflash lamps in general comprise a he:.metically sealed light-trans-mitting envelope usually made of soft glass which contains a combustion-supporting ga5 such as oxygen at about five or seven atmospheres, together with a filling o suitable light-producing combustible material such as shredded foil o zixconium, for example~ to produce a high intensity flash o actinic light. A stem press ~ase is located at one end o~ the lamp envelope to form a hermetic seal with a pair of ~ electrical lead-in w.ires having a refractory metal resistance filament connected therebetween. In such electrical~ignition type photoflash lamps now being used, the inner ends of these wires are coated with a charge oE heat-sen~itive primer material so that when electrical current is passed through the resistant ~ilament, there will be deElagration o the primer material cau~ing the shredded combustible foil in the lamp envelope to burn rapidly with incandescence. Two lamps of this general type in current manuacture with soft glass ~or ~lashcube-type product applications and called AG-l or AG-3, are more particularly described in IJ.S. Patent 3,506,385, assigned to the assi~nee o~ the present invention.
- ~ - LD 7766 A primer ignition material for use with a high-voltage type flash lamp which can be deposited from an a~ueous coa~ing composition is disclosed in UOS. Patent 3~972,673, also assigned to the present assignee~ Said ignition pri~er material includes a combustion-supporting oxide to provide an additional oxygen ~ource in the primer material which is readily available for combustion of the primer fuel when the primer mixture is ignited~ Preferred combustion supporting oxides are cobalt oxide, barium chromateJ iron oxide ana higher oxides of nickel which are easily reduced by zirconium fuel in the primer mîxture to lower non-conducting oxides but which resist further dissociation forming conductive residues after the lamp has been flashed. Where formation of such conductive residues is not objection~ble, however, still other metal oxides are disclosed which can be reduced by the fuel metal upon primer ignition including copper oxide, lead oxide, tin oxide, titanium oxide, and zinc oxide as well as still oth~rs. Utilization of said combustion supporting oxide~ in this type primer ignition matexial enhances reliable ignition of the overall high voltage flash lamp to produce th~ desired light output in a relatively short time period.
A comparison o the ignition characteristics for such flash lamp between primer materials applied from an aqueous suspension as compared with the sama primer materials applied from organic liquid suspension finds the latter primers to ignite more rapidly which is desirable.
Since the relative speed of primer ignition influences the rate at which light i9 generated by the flash lamp, it follows that such water-based primer materials could prove too slow to ignite for acceptable use although safer to handle in lamp manufacture than primer materi~ls applied from organic liquid suspen~ion. It is a desirab1e objective, therefore, to improve the speed of ignition for prim~r materials which can be applied from an aqueous liquid suspension~ , It is another desirable objective to improve the stability of primer materials used in said flash lamps so that the flash lamps are less prone -to prematur~
ignition from either mechanical vibration or electros~atic charges.
SUMMARY OF THE INVENTION
_.
An improved primer material has now been discovered which can be applied reliably as a coating for the lead-in conductors of an electrical-ignition flashcube type flash lamp from a water-based suspension having none o the foregoing drawbacks. Specifically, it has been ound tha~ incorporation of a hygroscopic agent ;n the aqueous suspension of said primer material provides a dried product con~a.ining sa.id additive which ignites more rapidly and is also less prone to premature ignition than when a primer material no~ containing said addi-tive has been deposited from an organic liquid suspension. The primer material havi~g the desired characteristics compxise~
a mixture of powdered zirconium fuel, a polymer binder, an oxidizer for said fuel selected from an alkali metal chlorate ox pe~chlorate compound, a com~ustion-supporting oxide, and said hygroscopic additive. In its preferred embodiments, the primer material utilizes a combustion-supporting oxide selected from cobalt oxide, barium chromate, 'ron oxide, and higher oxides of nickel to avoid any electrical short-circuited condition in the lamp ater Elashing created by a conductive primer residue. An alkali metal chlorate compound is also preferred as the oxidizer in the present primer material by xeason of being water-soluble to provide more uniform distribution in the dri.ed primer ignition mass than an alkali metal perchlorate compound which is les~
water-soluble. In said preferred dried primer mixtures, the proportion of oxidizer is approxi.mately 4-12% by 35~
weight with the hygroscopic agent also being present in the same weight range (4-12%). Polyvinyl alcohol and polyvinyl pyrrolidone are preferred organîc binders ~or the aqueous coating composition since both provide a S tough and adherent coating of the dried primer mass in the flash lamp.
A suitable hygroscopic agent can be selected from a wide variety of known materials which absorb water without becoming liquified. More particularly, said hygroscopic additive must be capable of preferentially absorbing mois~ure from the fuel and oxidizer constituents in the deposited mixture after drying to enhance ~he speed of primer igni~ion. Rnown hygroscopic addi~ives include such diverse materials as cobaltous cobaltic cyanide, boric oxide, and calcium sulfate which all can be distributed uniformly in the present aqueous primer suspensions ei-~her as a powdered solid or dissolvsd in said suspensions~ The preferred hygroscopic additive is cobaltous cobaltic cyanide since said material may provide a source of combustion supportin~ oxide when the primer is ignited and thereby support more thorough and rapid combustion.
BRIEF DESCRIPTION OF THE DRAWING
In the accompanying drawing, the single figure represents a cross section view partly in elevation of a preferred flash lamp utilizing the present invention~
DESCRIPT~ON OF THE PRRFERRED EMBODIMENTS
A preferred flash lamp construction is depicted compr.ising a glass bulb or envelope 1 which is shown may be formed of a short lengthened glass tubing, for example, about 0.340 inch outside diameter which is constricted and rounded off at one end as indicated at 2 and closed off thereof by an exhaust tube 3 and is ~ormed at the other or base end 4 with a stem press base. A flashcube type lamp having this general conEigurat.ion and in commercial production is the previously rPferenced AG-l which produces approximately 7,000 lumen-seconds light output for a 1.1 cubic centimeter internal volume The lead-in wires 6 are sealed in opposi-te corners 7 of the stem press base which provides a longer path length of the in-leads through the lamp envelope and less likelihood o~ leakage or loss o a hermetic seal~ The glass and metal in-lead compositions ~or said flash lamp are dictated by the desired ligh~ output characteristics and some high performance flash lamps utilize a borosilicate glass in combination with alloy in-leads of iron, nickel, and cobalt. The inner ends of said in-leads axe coated with the primer material 8 and have an electrical filament 9 connected therebetween. This filament is a re~ractory metal such as tungsten or a tungsten alloy. A quantity of ~ilamentary combustible material 10 such as a shredded foil of zirconium or hafnium, for example, is distributed within the interior space of the envelope 1 which also contains a ~illin~ of a suitable combustion supporting gas such as o~ygen, generally a-t high pressures in excess of several atmospheres.
The solid coating of primer material in the above embodiment is applied to the lead-in conductors from an aqueous suspension of the present invention in various known ways. For example, the in-lead members can be dipped into the aqueous slurry followed by drying in air or wi-th heat to remove the liquid and form a solid adherent coating having the desired characteristics above de~cribed.
Alterna~.ely, the aqueous slurry can be sprayed on the in-lead members and thareafter processed to provide a solid coating exhibi~ing comparable performance.
AS an example of a suitable aqueous coating composition, there is initially prepared the fuel portion of said primer mixture as an aqueous suspension containing 80 parts milled zirconium, 10 parts barium chromate, 10 parts cobalt oxide, 5 parts cobaltous cohaltic cyanide, 3s~
~ 6 ~ I,D 7766 and ~ pa:rts polyvinyl pyrrolidone binder. To said aqueous fuel suspension there is added with mixing an aqueous oxidizer solution of sodium chlorate in various amounts so that the dried primer ml~ture cont~ins from 4-12 percent ox.idi~er by weight. ~ solid coating of sa.id primer material .is applied to both in-leads of the above type lamp construction in the conventional manner.
Performance tests were conducted on -the above described flash lamp embodiments to evaluate the effectiveness of the hygroscopic additive in providing light output improvement. Spec.iicallyt flash lamps utilizing a water~based primer containing said hygroscopic ~dditive were ~lashed for comparison with flash lamp performance when said additive was not used and :~urther compared with flash lamp performance when the same la-tter primer solids had been deposlted from a conventi.onal organic liquid suspension. Sample lo-ts o~ 50 lamps were flashed duriny said performance tests by application of an electrical pulse of 1.5 volts and 0.8 ampere during a ~0 0.7 second time interval. The sample lot of flash lamps using primer not containlng said hygroscopic additive and deposited ~rom an amyl aceta-te liquid susper.sion demonstrated a 76% flashabili-ty rate. The flashability rate of :Lamps utilizing the water-based primer suspensions is reported in the table below for various oxidizer levels in the primer mixture.
Flashahility o~ Flashability of Oxiclizer Content Primer with 5% Primer without (B~ We.ight) _ Additive (By Weight~ Additive 5% 96% 78%
7~ 84% 72%
9~ ~2~ 72~
'rhe above tes-t results demonstrate an average increase in lamp flashability from 74% to 91% at the indicated test condi.tions when said water-based primer materials contain ci8 - 7 - I.D 7766 cobaltic cobaltous cyanide addi-tive, Further observations conducted during flash lamp manufacture with said water-based primers indicated a significant reduction in premature flashing from mechanical vibration and elec-tro-static discharge as compared with lamp manufactura usingsaid conven-tional amyl acetate primer suspension.
It follows from the foregoing disclosure that various changes and modifications may be made in the above described improved primer material without departing from ~he spirit and scope of the invention. For example, it will be apparent that other fuel compositions can be employed in said primer mixture, such as red phosphorus to still provide comparable electrical ignition charac-teristics. Additionally, it is contemplated to vary the weight proportions of the specific cons-tituents in the primer mix-ture above specifically disclosed depending upon the performance requirements desired in a particular flash lamp construction with respect to light OUtpllt level and flash duration, Consequentlyl it is intended to limit the presen~ invention, therefore, only by the scope of the following claims.
Claims (12)
1. A primer material for a flash lamp utilizing resistive filament ignition, comprising: a mixture of powdered zirconium fuel, a polymer binder, an oxidizer for said fuel selected from an alkali metal chlorate compound and an alkali metal perchlorate compound, a combustion-supporting oxide, and an inorganic compound additive which is hygroscopic and which furnishes a source of combustion-supporting oxide when said primer material is ignited.
2. A primer material as in claim 1, wherein the oxidizer is an alkali metal chlorate compound.
3. A primer material as in claim 1, wherein the combustion-supporting oxide is a mixture of cobalt oxide and barium chromate.
4. A primer material as in claim 1, wherein the additive is cobaltous cobaltic cyanide.
5. A primer material as in claim 1, wherein the polymer binder is polyvinyl pyrrolidone.
6. A primer material as in claim 1, which contains in percentages by weight 4 to 12 percent oxidizer and 4 to 12 percent additive.
7. A coating composition to produce a dried primer material for a flashcube type flash lamp utilizing resistive filament ignition, comprising: an aqueous suspension of powdered zirconium fuel, a polymer binder, an oxidizer for said fuel selected from an alkali metal chlorate compound and an alkali metal perchlorate compound, a combustion-supporting oxide selected from cobalt oxide, barium chromate, iron oxide and higher oxides of nickel, and an inorganic compound additive which is hygroscopic and which furnishes a source of combustion-supporting oxide when said primer material is ignited.
8. A coating composition as in claim 7, wherein the polymer binder is water-soluble.
9. A coating composition as in claim 8, wherein the polymer binder is selected from polyvinyl alcohol and polyvinyl pyrrolidone.
10. A coating composition as in claim 7, wherein the oxidizer is an alkali metal chlorate compound.
11. A coating composition as in claim 7, wherein the combustion-supporting oxide is a mixture of cobalt oxide and barium chromate.
12. A coating composition as in claim 7, wherein the additive is cobaltous cobaltic cyanide.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000351560A CA1142358A (en) | 1980-05-09 | 1980-05-09 | Photoflash lamp primer material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000351560A CA1142358A (en) | 1980-05-09 | 1980-05-09 | Photoflash lamp primer material |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1142358A true CA1142358A (en) | 1983-03-08 |
Family
ID=4116903
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000351560A Expired CA1142358A (en) | 1980-05-09 | 1980-05-09 | Photoflash lamp primer material |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1142358A (en) |
-
1980
- 1980-05-09 CA CA000351560A patent/CA1142358A/en not_active Expired
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| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |