Title:
Flash Lamp Mount Construction
United States Patent 3884615
Abstract:
A glass bead is provided over an end of a pair of inlead wires for a flash lamp. An opening is provided through the bead between and in communication with both inlead wires, and is filled with primer material. One of the inlead wires may extend through the bead and into contact with combustible material in the lamp. The underside of the bead may be sleeved or shaped to prevent shorting between the inlead wires.
US Patent References:
FLASH BULB
Van der Tas et al. - October 1973 - 3768957
METHOD OF MAKING COMBUSTION FLASH BULB
De Graaf et al. - July 1974 - 3823994
FLASH BULB
Van der Tas et al. - October 1973 - 3768957
METHOD OF MAKING COMBUSTION FLASH BULB
De Graaf et al. - July 1974 - 3823994
Application Number:
05/453487
Publication Date:
05/20/1975
Filing Date:
03/21/1974
View Patent Images:
Export Citation:
Assignee:
General Electric Company (Schenectady, NY)
Primary Class:
International Classes:
F21K5/08; F21K5/00; F21K5/02
Field of Search:
431/93-95
Primary Examiner:
Dority Jr., Carroll B.
Attorney, Agent or Firm:
Fulmer, Norman Kempton Lawrence Neuhauser Frank C. R. L.
Claims:
What I claim as new and desire to secure by Letters Patent of the United States is
1. A photoflash lamp of the type having a bulb and a mount comprising a pair of inleads extending within the bulb and having flash ignition means connected across said inleads within said bulb, said bulb containing combustible material ignitable by said flash ignition means, wherein said flash ignition means comprises an electrically insulative member, said inleads extending into said insulative member, an opening through said insulative member between and in communication with both of said inleads, said opening having ends thereof at different locations on the surface of said insulative member and communicating with the interior of said bulb, at each of said ends, and primer material contained in said opening and connected electrically across said inleads said primer material being exposed to said interior of the bulb at both said ends of said opening.
2. A flash lamp as claimed in claim 1, in which one end of said opening through the insulative member is directed toward said combustible material.
3. A flash lamp as claimed in claim 2, in which said insulative member overlies at least a portion of the ends of said inleads.
4. A flash lamp as claimed in claim 2, in which said inleads are substantially mutually parallel and enter into the bulb through a seal region at which the bulb wall is relatively thicker than the rest of the bulb wall, said opening extending substantially straight through the insulative member in a direction substantially parallel to said inleads, the other end of said opening being directed toward said seal region.
5. A flash lamp as claimed in claim 4, in which said opening is tapered with the larger cross-section area thereof being at said end directed toward said seal region.
6. A flash lamp as claimed in claim 4, in which said opening is in the shape of a slot extending between said inleads and through said insulative member.
7. A flash lamp as claimed in claim 6, in which said slot has a height of about 0.080 inch through said insulative member, a length of about 0.040 inch between said inleads, and a width of about 0.015 inch.
8. A flash lamp as claimed in claim 4, in which said opening has a substantially circular cross-sectional shape.
9. A flash lamp as claimed in claim 8, in which said circular opening is tapered with the larger diameter end thereof being at said end directed toward said seal region.
10. A flash lamp as claimed in claim 9, in which said insulative member overlies at least a portion of the ends of said inleads.
11. A flash lamp as claimed in claim 9, in which said tapered circular opening has a length of about 0.080 inch, a small end diameter of about 0.024 inch, and a larger end diameter of about 0.040 inch.
12. A flash lamp as claimed in claim 4, in which one of said inleads extends entirely through said insulative member and into electrical contact with said combustible material.
13. A flash lamp as claimed in claim 4, including at least one sleeve of insulative material positioned around one of said inleads and attached to and extending from said insulative member toward said seal region.
14. A flash lamp as claimed in claim 4, in which said insulative member extends toward said seal region alongside at least one of said inleads.
15. A flash lamp as claimed in claim 4, in which said inleads are shaped to be relatively farther apart at said seal region than at said insulative member.
1. A photoflash lamp of the type having a bulb and a mount comprising a pair of inleads extending within the bulb and having flash ignition means connected across said inleads within said bulb, said bulb containing combustible material ignitable by said flash ignition means, wherein said flash ignition means comprises an electrically insulative member, said inleads extending into said insulative member, an opening through said insulative member between and in communication with both of said inleads, said opening having ends thereof at different locations on the surface of said insulative member and communicating with the interior of said bulb, at each of said ends, and primer material contained in said opening and connected electrically across said inleads said primer material being exposed to said interior of the bulb at both said ends of said opening.
2. A flash lamp as claimed in claim 1, in which one end of said opening through the insulative member is directed toward said combustible material.
3. A flash lamp as claimed in claim 2, in which said insulative member overlies at least a portion of the ends of said inleads.
4. A flash lamp as claimed in claim 2, in which said inleads are substantially mutually parallel and enter into the bulb through a seal region at which the bulb wall is relatively thicker than the rest of the bulb wall, said opening extending substantially straight through the insulative member in a direction substantially parallel to said inleads, the other end of said opening being directed toward said seal region.
5. A flash lamp as claimed in claim 4, in which said opening is tapered with the larger cross-section area thereof being at said end directed toward said seal region.
6. A flash lamp as claimed in claim 4, in which said opening is in the shape of a slot extending between said inleads and through said insulative member.
7. A flash lamp as claimed in claim 6, in which said slot has a height of about 0.080 inch through said insulative member, a length of about 0.040 inch between said inleads, and a width of about 0.015 inch.
8. A flash lamp as claimed in claim 4, in which said opening has a substantially circular cross-sectional shape.
9. A flash lamp as claimed in claim 8, in which said circular opening is tapered with the larger diameter end thereof being at said end directed toward said seal region.
10. A flash lamp as claimed in claim 9, in which said insulative member overlies at least a portion of the ends of said inleads.
11. A flash lamp as claimed in claim 9, in which said tapered circular opening has a length of about 0.080 inch, a small end diameter of about 0.024 inch, and a larger end diameter of about 0.040 inch.
12. A flash lamp as claimed in claim 4, in which one of said inleads extends entirely through said insulative member and into electrical contact with said combustible material.
13. A flash lamp as claimed in claim 4, including at least one sleeve of insulative material positioned around one of said inleads and attached to and extending from said insulative member toward said seal region.
14. A flash lamp as claimed in claim 4, in which said insulative member extends toward said seal region alongside at least one of said inleads.
15. A flash lamp as claimed in claim 4, in which said inleads are shaped to be relatively farther apart at said seal region than at said insulative member.
Description:
CROSS-REFERENCE TO RELATED APPLICATION
Ser. No. 356,459, filed May 2, 1973, now U.S. Pat. No. 3,816,054, John Baldrige, Jr., and John C. Sobieski, "Photoflash Lamp Having Non-Shorting Construction," assigned the same as this invention.
BACKGROUND OF THE INVENTION
The invention is in the field of photoflash lamps of the so-called high-voltage type, which contain a primer material connected across inlead wires, there being no conventional filament in such a lamp. The "mount" for such a lamp comprises an assembly including inlead wires and primer material.
Photoflash lamps may be classified generally into two voltage types: low-voltage and high-voltage. The low-voltage types usually are intended to be flashed by a battery, or a charged capacitor, having a voltage of about 1.5 volts to 15 volts, whereas the high-voltage flash lamps are intended to be flashed by a firing pulse of a few hundred volts or greater such as can be produced by a piezoelectric element. Conventional low-voltage flash lamps contain a filament connected across inlead wires. When the filament is heated by a firing current, it ignites a primer material which in turn ignites a combustible material such as metal foil which, with the aid of oxygen in the lamp, produces a flash of light.
In typical high-voltage flash lamp constructions, the primer material is connected directly across and between a pair of inlead wires extending into the lamp envelope. The primer material may be positioned and carried in the lamp on top of a glass or ceramic insulating material member through which the inlead wires extend, or may be carried in a cavity in such a member. In another construction, the primer material is carried on or in a depression in the inner wall of the envelope at the bottom of the lamp. In another high-voltage flash lamp construction, disclosed in U.S. Pat. Nos. 2,868,003 and 3,000,200, both to Warren Albrecht, the primer material is applied to one or both of the inlead wires within the lamp and the electrical circuit is completed through the combustible shredded metal foil in the lamp.
SUMMARY OF THE INVENTION
Objects of the invention are to provide a new and improved mount construction for flash lamps, and to provide flash lamps incorporating such mounts, in which the primer will reliably ignite the combustible material in the lamp, and in which a flashed lamp will reliably have a high impedance across its lead-in wires.
The invention comprises, briefly and in a preferred embodiment, a flash lamp mount construction comprising a glass bead or other electrically insulative member provided over an end of a pair of inlead wires. An opening is provided through the bead member between and in communication with both of the inlead wires, and primer material is provided in the opening and electrically bridges across the inlead wires. Preferably the aforesaid opening extends fully through the bead member, in a direction parallel to the inlead wires. Also, preferably, a portion of the bead member extends above and over and overlies at least a portion of the ends of the inlead wires. One of the inlead wires may extend through the top of the bead member and into contact with combustible material in the lamp. The underside of the bead member may be sleeved or shaped to provide increased electrical insulation at the inlead wires to prevent shorting between them.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a photoflash lamp in accordance with a preferred embodiment of the invention.
FIG. 2 is a top view of the mount in the flash lamp of FIG. 1.
FIG. 3 is a side cross-sectional view of the mount construction.
FIGS. 4, 5, and 6 are side cross-sectional views of modified mount constructions in accordance with the invention.
FIG. 7 is a side view of a flash lamp construction in accordance with another preferred embodiment of the invention.
FIG. 8 is a side cross-sectional view of the mount employed in FIG. 7.
FIG. 9 is a top view of the mount of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lamp shown in FIG. 1 of the drawings is generally the same, except for the mount construction, as that shown in FIG. 5 of U.S. Pat. No. 3,506,385 to Kurt Weber and George Cressman, and comprises a tubular envelope 11, preferably made of a borosilicate glass or other suitable vitreous material such as lead glass and having a stem press seal 12 at one end thereof through which a pair of inlead wires 13, 14 extend from the exterior to the interior of the bulb 11 in a generally mutually parallel spaced apart manner and form part of a mount 15. The bulb 11 is partially filled, above the mount, with a loose mass of filamentary or shredded metal wire or foil 16, of zirconium or hafnium or other suitable combustible metal. Air is exhausted from the bulb 11, and the bulb is filled with oxygen at a pressure of at least several atmospheres, such as about 5 to 10 atmospheres, and the bulb is sealed off at an exhaust tip 16 at the other end thereof from the stem press seal 12. The lamp may be coated with the usual lacquer or plastic protective coating.
In accordance with the invention, and as shown in FIGS. 2 and 3, the mount 15 includes flash ignition means for igniting the combustible material 16, comprising a glass bead or other vitreous electrically insulative member 18 sealed over and around an end of the pair of lead-in or inlead wires 13 and 14. An opening 19 is provided through the bead 18 and is between and in communication with both of the inlead wires 13 and 14. The bead 18 may be formed by placing a ring of glass around the ends of the inlead wires, and heating for a suitable time at a suitable temperature so as to cause the glass ring to shrink into molten contact with the end portions of the inlead wires, leaving the slot-like or other shaped opening 19. Greater accuracy can be achieved by molding the glass ring into place. The ends of the inlead wires 13 and 14 extend only partially into the bead, as shown, and the bead material overlies the ends of the inlead wires. Suitable dimensions for the bead 18 are about 0.080 inch in height, with the slot 19 being about 0.015 inch wide and about 0.040 inch long between the inlead wires 13 and 14.
The opening 19 is at least partially filled with primer material 21. Various suitable primer materials are known; for example, a mixture may be prepared of fine particles of zirconium and potassium perchlorate along with a binder such as nitrocellulose and solvent such as amyl acetate, as described in the above-mentioned Albrecht patents. This binder, in liquid form, is applied to the opening 19 with a syringe, or by daubing, or by dipping the inverted mount onto the surface of the liquid primer. The small cross-sectional area of the opening 19, and the opening being open at both ends, causes a capillary action effect which aids in drawing the liquid primer material into the opening. The binder and solvent are then dried out from the primer material 21 in the opening 19. Preferably the mount 15 is sealed in the envelope 11 prior to putting the primer 21 into the opening 19 of the bead 18, and then the combustible material 16 is positioned in the envelope above the bead 18 whereby the upper end of the opening 19 is directed toward the combustible material 16, the tipped-off end 17 is necked down, the bulb is evacuated and filled in with oxygen, and then tipped off at 17.
The mount construction of the invention achieves several desirable advantages. Prior to flashing of the lamp, the top ends of the inlead wires 13 and 14, being covered over by the bead material and the primer, cannot become short-circuited by being in contact with shreds of the combustible material 16. The bead 18 is large enough in diameter to reduce the likelihood of strands of material 16 from extending down between the bead and inner wall of bulb 11 so as to short the inlead wires 13 and 14. During flashing of the lamp, with the lamp conventionally being in base-down position as shown in the drawing, voltage applied to the primer 21 via the inlead wires 13 and 14 causes the primer 21 to ignite, causing a blast of sparks both upwardly and downwardly from the opening 19. The upward blast of sparks is directed toward and ignites the combustible material 16, which, with the aid of the oxygen in the lamp, causes a flash of light. The downward blast of sparks from the opening 19, with the aid of gravity, assures complete or substantially complete exiting of primer material from the opening 19, thus insuring an open circuit rather than a short circuit in the flashed lamp between the inlead wires 13 and 14. The aforesaid downward blast of sparks is directed toward the thickened glass at the seal 12 at the bottom of the bulb, which readily withstands the blast. Also, upon flashing of the lamp, the glass bead covering over some or all of the upper ends of the lead-in wires 13 and 14 helps to prevent particles of burned or partly burned metal of the combustible material 16 from falling against the ends of the lead-in wires and causing a short or partial short between them, and the small cross-sectional size of the opening 19 tends to prevent burned metal debris from falling into the opening 19 so as to short across the inleads 13, 14.
In the modification of FIG. 4, one of the lead-in wires 14 extends completely through the bead 18 and is in electrical contact with the combustion metal 16, which is desirable in certain flash lamps so that the combustion material 16 can be electrically grounded, thus reducing the possibility of accidental electrostatic flashing of the lamp.
In the modification of FIG. 5, a glass sleeve 23 extends downwardly from the bead 18 and around one of the lead-in wires 13, and functions to help prevent debris from the combustion material 16 from shorting between the lead-in wires 13 and 14 at the underside of the bead 18 after the lamp has flashed. In the modification of FIG. 6, the bead 18 is shaped so as to extend downwardly and partially around each of the lead-in wires 13 and 14, for the same purpose as that of FIG. 5, i.e., to help prevent debris from the combustible material 16 of the flashed lamp from shorting across the lead-in wires below the bead 18.
The alternative embodiment of the invention shown in FIGS. 7, 8, and 9 is generally the same as that of FIGS. 1, 2, and 3, except that the opening 19 through the bead 18 is a circular tapered hole having a larger diameter toward the bottom of the bead and facing the seal 12, as shown. It will be noted that FIGS. 8 and 9 do not show primer material in the opening 19. In a successful construction of this embodiment, the height of the bead 18 is 0.080 inch, the smaller (upper) diameter of the opening 19 being approximately 0.024 inch, and the diameter of the larger (bottom) end of the circular opening being approximately 0.040 inch. It will be noted that, near the small upper end of the opening 19, the glass or other material of the bead 18 completely covers over the upper ends of the lead-in wires 13 and 14, thus virtually assuring that no metallic debris from the flashing of the combustible material 16 will be able to fall into the opening 19 and short across the lead-in wires 13 and 14.
It is believed that tapering the opening 19, as best shown in FIGS. 8 and 9, with the larger end downward in the lamp (it being understood that flash lamps are usually oriented base-down when flashing) helps the flashing primer material debris to fall downwardly and out of the opening 19, as well as being blasted down out of the opening toward the thickened glass at the seal 12, therefore helping to insure that no substantial amount of primer material will remain in the opening 19 after flashing which could cause a short or low impedance across the lead-in wires 13 and 14, while at the same time a sufficient amount of primer blast sparks blast upwardly from the opening 19 so as to reach and ignite the combustible material 16 when the lamp is flashed. The slot-like opening 19 shown in FIGS. 1-6 could also similarly be tapered so as to have a larger cross section at the bottom of the head 18 than at the top thereof. The embodiment of FIGS. 7-9 can employ the modifications of FIGS. 4-6.
It has been found that the invention achieves the objectives of providing a high-voltage flash lamp which will reliably flash, and which will reliably have an open circuit or high impedance across its lead-wires after flashing, these objectives being achieved by constructing a mount comprising a bead or other electrically insulative member provided over an end of a pair of substantially parallel lead-in wires, there being an opening through the bead between and in communication with both of the lead-in wires, the opening being filled or partially filled with primer material and being open at both ends thereof at different locations on the surface of the insulative member to the interior of the flash lamp, so that when the primer ignites it can readily blast out and exit from the opening at both ends thereof, thus insuring that little if any residue of the primer will remain in the opening after flashing.
Preferably, a clear glass bead 18 having rounded sides is employed, as shown, whereupon the curved sides of the bead function as a magnifying lens for aiding visual inspection to see whether there is primer material in the opening 19, the primer material 21 usually being of a black or dark color. The lead-in wires 13 and 14 preferably are shaped as shown, being substantially mutually parallel and being farther apart where they enter the inside of the bulb 11 than at their upper ends at the bead 18 (which spacing at the bead is a function of desired firing breakdown voltage), thus providing more spacing between them on the bottom of the inside of the bulb and making it less likely that any falling metallic debris from the combustible material 16 which reaches the bottom of the bulb will cause a short across the lead-in wires 13 and 14. Alternative inlead arrangements include bringing the ends of the inleads in through opposite sides of the bead 18.
While preferred embodiments and modifications of the invention have been shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art and will fall within the scope of the invention as defined in the following claims.
Ser. No. 356,459, filed May 2, 1973, now U.S. Pat. No. 3,816,054, John Baldrige, Jr., and John C. Sobieski, "Photoflash Lamp Having Non-Shorting Construction," assigned the same as this invention.
BACKGROUND OF THE INVENTION
The invention is in the field of photoflash lamps of the so-called high-voltage type, which contain a primer material connected across inlead wires, there being no conventional filament in such a lamp. The "mount" for such a lamp comprises an assembly including inlead wires and primer material.
Photoflash lamps may be classified generally into two voltage types: low-voltage and high-voltage. The low-voltage types usually are intended to be flashed by a battery, or a charged capacitor, having a voltage of about 1.5 volts to 15 volts, whereas the high-voltage flash lamps are intended to be flashed by a firing pulse of a few hundred volts or greater such as can be produced by a piezoelectric element. Conventional low-voltage flash lamps contain a filament connected across inlead wires. When the filament is heated by a firing current, it ignites a primer material which in turn ignites a combustible material such as metal foil which, with the aid of oxygen in the lamp, produces a flash of light.
In typical high-voltage flash lamp constructions, the primer material is connected directly across and between a pair of inlead wires extending into the lamp envelope. The primer material may be positioned and carried in the lamp on top of a glass or ceramic insulating material member through which the inlead wires extend, or may be carried in a cavity in such a member. In another construction, the primer material is carried on or in a depression in the inner wall of the envelope at the bottom of the lamp. In another high-voltage flash lamp construction, disclosed in U.S. Pat. Nos. 2,868,003 and 3,000,200, both to Warren Albrecht, the primer material is applied to one or both of the inlead wires within the lamp and the electrical circuit is completed through the combustible shredded metal foil in the lamp.
SUMMARY OF THE INVENTION
Objects of the invention are to provide a new and improved mount construction for flash lamps, and to provide flash lamps incorporating such mounts, in which the primer will reliably ignite the combustible material in the lamp, and in which a flashed lamp will reliably have a high impedance across its lead-in wires.
The invention comprises, briefly and in a preferred embodiment, a flash lamp mount construction comprising a glass bead or other electrically insulative member provided over an end of a pair of inlead wires. An opening is provided through the bead member between and in communication with both of the inlead wires, and primer material is provided in the opening and electrically bridges across the inlead wires. Preferably the aforesaid opening extends fully through the bead member, in a direction parallel to the inlead wires. Also, preferably, a portion of the bead member extends above and over and overlies at least a portion of the ends of the inlead wires. One of the inlead wires may extend through the top of the bead member and into contact with combustible material in the lamp. The underside of the bead member may be sleeved or shaped to provide increased electrical insulation at the inlead wires to prevent shorting between them.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view of a photoflash lamp in accordance with a preferred embodiment of the invention.
FIG. 2 is a top view of the mount in the flash lamp of FIG. 1.
FIG. 3 is a side cross-sectional view of the mount construction.
FIGS. 4, 5, and 6 are side cross-sectional views of modified mount constructions in accordance with the invention.
FIG. 7 is a side view of a flash lamp construction in accordance with another preferred embodiment of the invention.
FIG. 8 is a side cross-sectional view of the mount employed in FIG. 7.
FIG. 9 is a top view of the mount of FIG. 8.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The lamp shown in FIG. 1 of the drawings is generally the same, except for the mount construction, as that shown in FIG. 5 of U.S. Pat. No. 3,506,385 to Kurt Weber and George Cressman, and comprises a tubular envelope 11, preferably made of a borosilicate glass or other suitable vitreous material such as lead glass and having a stem press seal 12 at one end thereof through which a pair of inlead wires 13, 14 extend from the exterior to the interior of the bulb 11 in a generally mutually parallel spaced apart manner and form part of a mount 15. The bulb 11 is partially filled, above the mount, with a loose mass of filamentary or shredded metal wire or foil 16, of zirconium or hafnium or other suitable combustible metal. Air is exhausted from the bulb 11, and the bulb is filled with oxygen at a pressure of at least several atmospheres, such as about 5 to 10 atmospheres, and the bulb is sealed off at an exhaust tip 16 at the other end thereof from the stem press seal 12. The lamp may be coated with the usual lacquer or plastic protective coating.
In accordance with the invention, and as shown in FIGS. 2 and 3, the mount 15 includes flash ignition means for igniting the combustible material 16, comprising a glass bead or other vitreous electrically insulative member 18 sealed over and around an end of the pair of lead-in or inlead wires 13 and 14. An opening 19 is provided through the bead 18 and is between and in communication with both of the inlead wires 13 and 14. The bead 18 may be formed by placing a ring of glass around the ends of the inlead wires, and heating for a suitable time at a suitable temperature so as to cause the glass ring to shrink into molten contact with the end portions of the inlead wires, leaving the slot-like or other shaped opening 19. Greater accuracy can be achieved by molding the glass ring into place. The ends of the inlead wires 13 and 14 extend only partially into the bead, as shown, and the bead material overlies the ends of the inlead wires. Suitable dimensions for the bead 18 are about 0.080 inch in height, with the slot 19 being about 0.015 inch wide and about 0.040 inch long between the inlead wires 13 and 14.
The opening 19 is at least partially filled with primer material 21. Various suitable primer materials are known; for example, a mixture may be prepared of fine particles of zirconium and potassium perchlorate along with a binder such as nitrocellulose and solvent such as amyl acetate, as described in the above-mentioned Albrecht patents. This binder, in liquid form, is applied to the opening 19 with a syringe, or by daubing, or by dipping the inverted mount onto the surface of the liquid primer. The small cross-sectional area of the opening 19, and the opening being open at both ends, causes a capillary action effect which aids in drawing the liquid primer material into the opening. The binder and solvent are then dried out from the primer material 21 in the opening 19. Preferably the mount 15 is sealed in the envelope 11 prior to putting the primer 21 into the opening 19 of the bead 18, and then the combustible material 16 is positioned in the envelope above the bead 18 whereby the upper end of the opening 19 is directed toward the combustible material 16, the tipped-off end 17 is necked down, the bulb is evacuated and filled in with oxygen, and then tipped off at 17.
The mount construction of the invention achieves several desirable advantages. Prior to flashing of the lamp, the top ends of the inlead wires 13 and 14, being covered over by the bead material and the primer, cannot become short-circuited by being in contact with shreds of the combustible material 16. The bead 18 is large enough in diameter to reduce the likelihood of strands of material 16 from extending down between the bead and inner wall of bulb 11 so as to short the inlead wires 13 and 14. During flashing of the lamp, with the lamp conventionally being in base-down position as shown in the drawing, voltage applied to the primer 21 via the inlead wires 13 and 14 causes the primer 21 to ignite, causing a blast of sparks both upwardly and downwardly from the opening 19. The upward blast of sparks is directed toward and ignites the combustible material 16, which, with the aid of the oxygen in the lamp, causes a flash of light. The downward blast of sparks from the opening 19, with the aid of gravity, assures complete or substantially complete exiting of primer material from the opening 19, thus insuring an open circuit rather than a short circuit in the flashed lamp between the inlead wires 13 and 14. The aforesaid downward blast of sparks is directed toward the thickened glass at the seal 12 at the bottom of the bulb, which readily withstands the blast. Also, upon flashing of the lamp, the glass bead covering over some or all of the upper ends of the lead-in wires 13 and 14 helps to prevent particles of burned or partly burned metal of the combustible material 16 from falling against the ends of the lead-in wires and causing a short or partial short between them, and the small cross-sectional size of the opening 19 tends to prevent burned metal debris from falling into the opening 19 so as to short across the inleads 13, 14.
In the modification of FIG. 4, one of the lead-in wires 14 extends completely through the bead 18 and is in electrical contact with the combustion metal 16, which is desirable in certain flash lamps so that the combustion material 16 can be electrically grounded, thus reducing the possibility of accidental electrostatic flashing of the lamp.
In the modification of FIG. 5, a glass sleeve 23 extends downwardly from the bead 18 and around one of the lead-in wires 13, and functions to help prevent debris from the combustion material 16 from shorting between the lead-in wires 13 and 14 at the underside of the bead 18 after the lamp has flashed. In the modification of FIG. 6, the bead 18 is shaped so as to extend downwardly and partially around each of the lead-in wires 13 and 14, for the same purpose as that of FIG. 5, i.e., to help prevent debris from the combustible material 16 of the flashed lamp from shorting across the lead-in wires below the bead 18.
The alternative embodiment of the invention shown in FIGS. 7, 8, and 9 is generally the same as that of FIGS. 1, 2, and 3, except that the opening 19 through the bead 18 is a circular tapered hole having a larger diameter toward the bottom of the bead and facing the seal 12, as shown. It will be noted that FIGS. 8 and 9 do not show primer material in the opening 19. In a successful construction of this embodiment, the height of the bead 18 is 0.080 inch, the smaller (upper) diameter of the opening 19 being approximately 0.024 inch, and the diameter of the larger (bottom) end of the circular opening being approximately 0.040 inch. It will be noted that, near the small upper end of the opening 19, the glass or other material of the bead 18 completely covers over the upper ends of the lead-in wires 13 and 14, thus virtually assuring that no metallic debris from the flashing of the combustible material 16 will be able to fall into the opening 19 and short across the lead-in wires 13 and 14.
It is believed that tapering the opening 19, as best shown in FIGS. 8 and 9, with the larger end downward in the lamp (it being understood that flash lamps are usually oriented base-down when flashing) helps the flashing primer material debris to fall downwardly and out of the opening 19, as well as being blasted down out of the opening toward the thickened glass at the seal 12, therefore helping to insure that no substantial amount of primer material will remain in the opening 19 after flashing which could cause a short or low impedance across the lead-in wires 13 and 14, while at the same time a sufficient amount of primer blast sparks blast upwardly from the opening 19 so as to reach and ignite the combustible material 16 when the lamp is flashed. The slot-like opening 19 shown in FIGS. 1-6 could also similarly be tapered so as to have a larger cross section at the bottom of the head 18 than at the top thereof. The embodiment of FIGS. 7-9 can employ the modifications of FIGS. 4-6.
It has been found that the invention achieves the objectives of providing a high-voltage flash lamp which will reliably flash, and which will reliably have an open circuit or high impedance across its lead-wires after flashing, these objectives being achieved by constructing a mount comprising a bead or other electrically insulative member provided over an end of a pair of substantially parallel lead-in wires, there being an opening through the bead between and in communication with both of the lead-in wires, the opening being filled or partially filled with primer material and being open at both ends thereof at different locations on the surface of the insulative member to the interior of the flash lamp, so that when the primer ignites it can readily blast out and exit from the opening at both ends thereof, thus insuring that little if any residue of the primer will remain in the opening after flashing.
Preferably, a clear glass bead 18 having rounded sides is employed, as shown, whereupon the curved sides of the bead function as a magnifying lens for aiding visual inspection to see whether there is primer material in the opening 19, the primer material 21 usually being of a black or dark color. The lead-in wires 13 and 14 preferably are shaped as shown, being substantially mutually parallel and being farther apart where they enter the inside of the bulb 11 than at their upper ends at the bead 18 (which spacing at the bead is a function of desired firing breakdown voltage), thus providing more spacing between them on the bottom of the inside of the bulb and making it less likely that any falling metallic debris from the combustible material 16 which reaches the bottom of the bulb will cause a short across the lead-in wires 13 and 14. Alternative inlead arrangements include bringing the ends of the inleads in through opposite sides of the bead 18.
While preferred embodiments and modifications of the invention have been shown and described, various other embodiments and modifications thereof will become apparent to persons skilled in the art and will fall within the scope of the invention as defined in the following claims.