US3569754A

US3569754A - Flash source

Info

Publication number: US3569754A
Application number: US738158A
Authority: US
Inventors: Richard G Priebe; Harold L Neuman; Michael L Rishton
Original assignee: Dyonics Inc
Current assignee: Smith and Nephew Inc
Priority date: 1968-06-19
Filing date: 1968-06-19
Publication date: 1971-03-09
Anticipated expiration: 1988-03-09

Abstract

A flash source comprises a mutually spaced lamp and lamp shield mounted between a lamp socket and an electrode head each having perforations for circulating cooling fluid communicating with the space between the lamp and shield. The socket has an insulator upon the surface of which an electrical connection to a helical spring trigger wire is fused and plated. The block supporting the socket also resiliently supports an external fluid conductor connected to the electrode head. The lamp is electrically connected by means of spring contact fingers engaging the electrode head inwardly of its perforations.

Description

United States Patent [72] Inventors Richard G. Priebe;

Harold L. Neuman; Michael L. Rishton, Reading, Mass. [21] Appl. No. 738,158 [22] Filed June 19, 1968 [45] Patented Mar. 9, 1971 [73] Assignee Dyonics, Inc.

Stoneham, Mass.

[54] FLASH SOURCE 10 Claims, 7 Drawing Figs.

[52] US. Cl 313/12, 313/35 [51] Int. Cl H0lj 1/02 [50] Field of Search 313/22, 198,184, 201; 303/12 [56] References Cited UNITED STATES PATENTS 2,654,043 9/1953 Freeman et al. 313/201X Germeshausen 2,756,361 7/1956 313/184 2,977,492 3/1961 l-loestra 313/22 3,337,762 8/1967 Vincent 313/22X 3,337,763 8/1967 Aronson et al. 313/22 Primary Examiner-Nathan Kaufman Attorney-Kenway, Jenney & Hildreth ABSTRACT: A flash source comprises a mutually spaced lamp and lamp shield mounted between a lamp socket and an electrode head each having perforations for circulating cooling fluid communicating with the space between the lamp and shield. The socket has an insulator upon the surface of which an electrical connection to a helical spring trigger wire is fused and plated. The block supporting the socket also resiliently supports an external fluid conductor connected to the electrode head, The lamp is electrically connected by means of spring contact fingers engaging the electrode head inwardly of its perforations.

' sum 1 or 3' FIG. I v

INVENTORS RICHARD s. PRIEBE HAROLD L. NEUMAN MICHAEL L. RISHTON ATTORNEYS -IOS INVENTORS RICHARD G. PRIEBE HAROLD L. NEUMAN MICHAEL L. RISHTON m ATTORNEYS sum 2 or '3 PATENTED MAR 9 I971 FIG. 2

PATENTEUMAR 91971 3569754 sum 3 0F 3 FIG. 7

FIG.5

INVENTORS RICHARD G. PRIEBE HAROLD L. NEUMAN MICHAEL L. RISHTON BY q ATTORNEYS FLASH SOURCE BACKGROUND OF THE INVENTION This invention relates generally, to intermittent flash sources, and is particularly intended for rapid repetition of flashes having uniform energy and brilliance and long service life.

A typical but not exclusive example of an application is found in an optical fundus camera. These cameras are used in medical diagnostic laboratories for examination of the fundus region of the eye by still photography, and in some cases by motion pictures. A suitable flash tube produces an arc about 7 millimeters in diameter and 50 millimeters in length, each flash being produced by a trigger pulse typically of about 25 kilovolts and in turn producing about 100 watt-seconds of energy at an average power of about 3 kilowatts.

The useful life measured in the number of flashes of the flash tube is related to the type of service, particularly the rate of flash repetition. For example, a commercially available tube having a life of over 50,000 flashes at a flash interval of 4 to seconds may have a life of only about 20,000 flashes at a flash interval of to 24 flashes per second. This difference can be attributed in most instances to problems in cooling the flash tube, the trigger circuit and the surrounding and related parts. in most flash sources localized heating develops as a result of difficulties in reaching the heated areas with the circulating coolant liquids usually employed. Specific problems arise from differentials in the thermal expansion of the various parts including supports, terminals, leads and connections. This in turn gives rise to mechanical and electrolytic breakdowns. Attempts at solving this problem and others previously mentioned have been rendered more difficult by the requirement of compactness imposed by the apparatus in which the flash source is often supported, such apparatus usually including optical elements and means for training a flash beam through the optics in an accurately determined direction or directions.

SUMMARY OF THE INVENTION This invention resides in an improved flash source comprising advantageous arrangements and configurations of the parts including supports for the tubular flash lamp and coolant circulation means, and in the trigger circuit for the lamp. Cooling liquid is circulated continuously between the lamp and a transparent lamp shield, the coolant passing through perforations in an electrode head receiving the lamp and defining an end space. This space is connected in the coolant circulation system through an external fluid and electrical conductor having a portion flexibly supported by a compliant adhesive material.

The lamp includes novel upper contact means, including a perforated mount secured to an end of the lamp and metallic spring contact fingers resiliently and radially engaging the wall of an aperture in the electrode head. The electrode head is also perforated to provide further fluid communication with the metal parts in the region subject to rapid and intense heatmg.

The trigger electrode is in the novel form of a helical stainless steel spring fastened at one end to a terminal on a refractory lamp base insulator. An electrically conductive strip plated on the insulator extends from this terminal along the insulator. This strip is produced by a novel process by which the insulator is first painted with a solution of a precious metal, then fired to fuse the metal to the surface of the insulator, and finally electroplated with a second metal to build up the cross section of the strip. This produces a mechanically stable and durable connection to the trigger electrode, further increasing the useful life of the flash source, especially for relatively high power units of the type described.

BRIEF DESCRIPTION OF THE DRAWING FIG. is a view in perspective of the assembled flash source. FIG. 2 is an elevation in section taken on line 2-2 of FIG. 1.

FIG. 3 is a partially cutaway view in perspective of the electrode head.

FIG. 4 is a view in perspective of the upper lamp mount.

FIG. 5 is a view in perspective of the contact finger sleeve.

FIG. 6 is a view of the trigger contact member.

FIG. 7 is a partially cutawayview in perspective of the lamp socket insulator illustrating its electroplated conductive ring and strip.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment herein described, all metal parts are preferably nickel plated to protect them from electrolytic actron.

Referring to FIGS. 1 and 2, the flash source is an assembly shown generally at 12, and suitably mounted within a housing (not shown) in appropriate relation to projection lenses and associated parts for directing the flashes of light and focusing them. The source has a generally rectangular shaped linen phenolic mounting clockl4. This block supports a Pyrex or similar glass lamp shield 16 having a cylindrical central portion and end portions of expanded diameter. The upper end of the lamp shield receives and is glued to a closed ended brass electrode head 18 having a central inner aperture 20 and a number of perforations 22 (FIG. 3), these perforations communicating with an end space 24 in the electrode head. The head 18 also has an external opening 26 (FIG. 3) to which is connected a brass fluid and electrical conductor tube 28. This tube is curved to fit within a recess 30 in the block 14, being surrounded and held in place within the recess by a body of compliant potting compound32, preferably a relatively soft epoxy resin. The flow path for a fluid coolant, such as water, extends from a suitable refrigeration system (not shown) through the tube 28 to the end space 24, through the perforations 22 to a space 34 within the lamp shield, to a communicating space 36 within the block 14 and to a brass tube 38 through which the fluid returns to the refrigeration system.

A flash lamp 40, mounted upon a socket, is inserted through an opening in the bottom of the block 14 and supported in spaced relation to the lamp shield with an electrode connection at each end of the lamp and a connection to a trigger circuit as hereinafter described. The flash lamp itself is of conventional form and includes a cylindrical glass envelope 42 closed at its ends by sealed metal end electrode caps 44. Short sealed metal tubes 46 extend from the caps with their ends crimped and soldered. These caps are used for making the electrode connections to the tube. The lower tube is soldered into an externally threaded, flanged lamp bushing 48, and the upper tube is soldered into a central aperture or perforation in a brass upper lamp mount 50 also having a circle of perforations 52 for coolant circulation. A phosphor bronze contact finger sleeve 54 is bent about the mount 50 and spot welded to it, the sleeve 54 having a number of spaced spring contact flngers 56 with radially outwardly curved end portions 58 adapted for resiliently engaging the wall of the central aperture 20 in the head 18.

The brass tube 28 is secured in the opening 26 in the head 18 and has a lug 60 at its lower end by which the upper electrode cap is connected to an external voltage source (not shown).

A fluid seal is provided between the head l8 and the lamp shield 16 by an O-ring 62 of heat resistant material. A body 64 of heat insulating material such as epoxy cement is molded over the otherwise externally exposed portions of the head I8.

The lamp bushing 48 is supported in a lamp socket subassembly designated generally at 66. This subassembly is secured in the clock I4 by means of an internally threaded and shouldered brass receptacle 68 fitted within an annular space drilled in the block and held in place by a linen phenolic socket pad or cover. A brass lamp socket 70 is threaded into the receptacle and tightened against an 'O-ring 72 to form a fluid seal. The lamp socket has a central hole in which is secured a brass lamp mount 73 having internal threads at the upper end to receive the lamp bushing 48. The lamp socket also has an upper portion of enlarged diameter defining a space 74 and four holes 76 passing transversely through it to the space 74. Thus the tube 38 has fluid connection to the space 34 between the lamp 40 and shield 16 by inner and outer paths, namely, a path through the holes 76 to the space 74 and around the lamp mount 73, and a second path from the space 36 along the interior wall of the block 14 to the enlarged lower end of the shield 16. These two paths are separated by a ceramic lamp socket insulator 78 mounted by means of epoxy cement 80 on an upper shoulder of the lamp socket support 70.

A linen or paper phenolic lamp socket pad 82 is fitted on a lower shoulder on the lamp socket support 70. Securing this pad to the lamp socket support is a body 84 of epoxy cement.

The lamp shield 16 is sealed to the block 14 by means of an O-ring 86 received in an inner annular recess in the block. Above this O-ring a quantity of epoxy cement 88 is applied, and a cover 90 of ceramic material is molded around the shield E6 to cover the upper surface of the block 14.

Electrical connection to the lower end of the flash lamp is completed through the lamp mount 73, the lamp socket support 70, the tube 38 which is threaded in the receptacle 68, a copper power lead 92 and a lug 94 for connection to the external voltage source.

The construction of the trigger circuit for the flash source is as follows. A phosphor bronze trigger contact member 96 (FIG. 6) is received in an inner annular groove in the block 14, and is formed with spaced curved spring contact fingers 98 that bear resiliently upon a conductive ring 100, plated as described below upon an external shoulder of the insulator 78. Connection of the ring 100 to an external trigger circuit is made in any desired manner, here illustrated as including a trigger plug 102 bearing on the member 96 and threaded in a transverse hole in the block 14. A trigger pulse generator (not shown) is received within a space 104 in a nylon receptacle 1016 fitted behind the plug 102 and suitably secured by screws to the block 14. A quantity of silicone grease preferably fills the void between the plug 102 and the receptacle 106. Electrical connection between the pulse generator and the plug is made through a brass fitting 108 on the receptacle. This electrical connection of the pulse generator to the ring 100 is completed when the lamp socket support 70 is threaded into the receptacle 68 in the block 14.

Extending upwardly from the conductive ring 100 along the surface of the insulator 78 is a conductive strip 110. A metal terminal 112 is fitted through a hole 114 in the strip 110 into the insulator. A stainless steel spring trigger 116 is performed as a helical wire spring, then stretched and wrapped around the envelope 42 of the lamp and secured to the terminal 112. The spring 116 has a uniform space between its turns. This form of trigger has been found to produce greater uniformity in production, thereby resulting in more reliable operation, particularly in high power flash sources such as are here described.

Past difficulties with trigger circuit connections on flash lamps have been substantially overcome by the method employed to apply the strip 110 and the ring 100 to the surface of the insulator 78. A solution of a precious metal such as platinum, silver or gold, is first painted upon the insulator, then fired in an oven at a temperature slightly above the melting temperature of the metal, this temperature having such value and being sustained for such a time duration that the metal is precipitated and fused to the surface of the ceramic insulator. As so fused, the metal has a substantially continuous surface at or slightly above that of the insulator. After the fusing step, nickel electroplated to the precious metal and builds up a conductive layer of appreciable thickness. It has been found that these conductive deposits are not seriously damaged by continuous and repeated operation under the relatively high temperatures of lamp use, and thereby the life of the lamp is appreciably increased.

in order to prevent undue wear upon the ring 100 by the fingers 98 of the member 96 as a result of repeated removal and replacement of the lamp socket subassembly 66, the lamp socket insulator 78 preferably has a groove 118 into which the electroplated ring is extended, thereby protecting its edge.

in operation, the flash source is provided with continuous circulation of coolant fluid from a refrigeration unit of the type commonly employed in this type of equipment. A suitable voltage is applied by means of a charged capacitor circuit between the

lugs

60 and 94, respectively connected to the end electrode caps on the lamp 40. When a suitable trigger pulse is applied by the pulse generator to the trigger plug 102 bearing upon the contact member 96, the voltage appears on the helical spring trigger 116 and fires the lamp. The heat generated by the electrical discharge is dissipated by the circulating fluid which flows on both sides of the insulator 78 as described above, and also flows through the holes 22 in the head 18 and the holes 52 in the upper lamp mount 50. Reliable electrical connection of the upper end cap of the flash lamp to the external circuit is maintained through the contact fingers 56 on the sleeve 54. At the same time, reliable electrical connection of the spring trigger 116 is assured by the spring fingers 98 of the contact member 96.

It will be understood that while the invention has been described with reference to a preferred embodiment, this is not intended to imply the limitation of its principals thereto. On the contrary, the invention is intended to encompass those adaptations, modifications, configurations and arrangements of the parts that would occur to one skilled in this art upon a reading of the foregoing specification.

We claim:

1. A flash source having, in combination:

a tubular lamp shield of insulating material having an end portion of expanded diameter;

a centrally apertured metallic electrode head fitted within said end portion; and

a lamp spaced from the lamp shield, fitted within the aperture in the electrode head and including an envelope and contact means secured to the envelope, said contact means including a number of metallic fingers resiliently and radially engaging the wall of said aperture.

2. The combination according to claim 1, in which the electrode head has an end defining an end space and providing a fluid connection, and a perforation between its central aperture and the lamp shield for connecting said end space to the space between the lamp and said shield.

3. The combination according to claim 2, in which the lamp has a contact pin and the contact means include a mount having provision to receive said pin and a perforation providing a second fluid path from the space between the lamp and shield to said end space.

4. The combination according to claim 3, in which the mount has plural perforations spaced in a circle about the contact pin.

5. The combination according to claim 3, in which the mount and electrode head each have plural perforations spaced in circles about the contact pin.

6. A flash source having, in combination:

a tubular envelope;

a trigger electrode around said envelope; and

a lamp socket of refractory insulating material having a termine! to which the trigger electrode is fastened and a conductor extending along its surface from the connector, said conductor comprising a first layer of metal heat fused to the surface of the socket and a second layer of metal electroplated on said first layer.

7. The combination according to claim 6, in which the first layer is selected from the group comprising platinum, silver and gold.

8. A flash source having, in combination:

a lamp base of rigid insulating material and having a cavity and a fluid connection therefrom;

a tubular lamp shield supported at one end on said base;

a lamp supported at one end on said base within and in trode head; and

spaced relation to the lamp shield, the space between the a body of compliant adhesive material supporting said fluid lamp and shield being in communication with said cavity; conductor on said base.

a electrode head defining an nd space a d h i a fl id 9. The combination according to claim 8, in which the lamp connection therewith, said electrode head supporting the 5 base has a recessed PQ to receive? length of the fluid other ends of the lamp and shield and providing a fluid ductor, and the q q i fi 531d l connection from the space therebetween to Said end 10. The combination according to claim 9, in which the adspace; hesive consists essentially of a compliant epoxy resin.

a metallic fluid conductor connected at one end to the elecl 0 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,5 9,75h- Dated March 9 97 fiichard G. Priebe, Harold L. Neuman,Michael L. Hi

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, lines 63-61 cancel "insulator" and substitute "surface of the insulator-- Column 2, line 68, cancel "clock" and substitute --b1ock-- Column 2, line 71, after "socket", second occurrenc insert --support-- Column 2 line 73, I/

after "socket" insert --supp l 75,

Column 3, line 68, after "nickel" insert --is-- Column 5, line 11,, cancel "and first occurrence, and substitute --end-- Signed and sealed this 6th day of July 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. tte i g Officer Commissioner of Patents

Claims

1. A flash source having, in combination: a tubular lamp shield of insulating material having an end portion of expanded diameter; a centrally apertured metallic electrode head fitted within said end portion; and a lamp spaced from the lamp shield, fitted within the aperture in the electrode head and including an envelope and contact means secured to the envelope, said contact means including a number of metallic fingers resiliently and radially engaging the wall of said aperture.

6. A flash source having, in combination: a tubular envelope; a trigger electrode around said envelope; and a lamp socket of refractory insulating material having a terminal to which the trigger electrode is fastened and a conductor extending along its surface from the connector, said conductor comprising a first layer of metal heat fused to the surface of the socket and a second layer of metal electroplated on said first layer.

8. A flash source having, in combination: a lamp base of rigid insulating material and having a cavity and a fluid connection therefrom; a tubular lamp shield supported at one end on said base; a lamp supported at one end on said base within and in spaced relation to the lamp shield, the space between the lamp and shield being in communication with said cavity; an electrode head defining an and space and having a fluid connection therewith, said electrode head supporting the other ends of the lamp and shield and providing a fluid connection from the space therebetween to said end space; a metallic fluid conductor connected at one end to the electrode head; and a body of compliant adhesive material supporting said fluid conductor on said base.

9. The combination according to claim 8, in which the lamp base has a recessed portion to receive a length of the fluid conductor, and the adhesive surrounds said length.

10. The combination according to claim 9, in which the adhesive consists essentially of a compliant epoxy resin.