US2688708A - Cold cathode flashing and other lamp - Google Patents

Description

' Sept. 7, 1954 H. F. CHARLOTTE COLD CATHODE FLASHING AND OTHER LAMP Filed Feb. 19, 1952 Patented Sept. 7, 195 4 UNITED STATS gram" OFFICE COLD CATHODE FLASHING AND OTHER LAMP Claims priority, application France February 23, 1951 12 Claims.

This invention relates to improvements in or relating to cold cathode lamps and more particularly to cold cathode flash lamps.

The invention has for an object to provide an improved discharge lamp capable of giving a White light.

Within the" last fifteen years much study has been made of the flashes obtained by discharging a condenser having between the electrodes thereof a difference of potential of several hundred or several thousand volts by means of two spaced electrodes disposed in a tube filled with a rare gas at an absolute pressure of a few inches of mercury.

The flashes thus obtained are of very short duration and of a very high light intensity, and often many thousands of candle power (stilb) are thus made available in nearly spectroscopically white light.

The discharges may be triggered at will, or peber's'; the study of the trajectories of high speed electrified particles; and the recording and projection o f cinematographic pictures by the continuous film technique, etc.

One of the most important applications of the white light flashing lamps is their use in Stroboscopy (Bruin: An apparatus for strobos'copic observation in Technical Review-Philips, 8: 1946, p; 25).

It is theobject of the present invention to provide a new improved flash lamp giving a white light and capable of functioning stroboscopically at arate comprised between approximately 1 to approximately 1,000 flashes per second.

The lamp according to the invention is made of quartz, Pyrex, Nonex, or other suitable hard glass; the gas filling preferably comprises a suitable mixture of rare gases such as krypton, argon and xenon permitting a substantially white light to beproduced.

The lamp further comprises an anode preferably in the shape of an inverted bell and a cooled cathode, preferably of'ta'nta-lum, thereby'increasing by morethan 50% the lightpower factor and permitting a concentration of the light cathode rays":

The lamp according to the invention may be overloaded for short periods without any danger tothe lamp itself. I

It is another object of the invention to provide a flash lamp" having a better performance of the cathode, i. e. a better stability at ultra-high frequencies, and also a short de-ionization timefactor, thereby permitting formation of an image of exact definition and accuracy of the object under study, 1. e. an' image free from blur or fuzziness, when using visual or photographic viewing methods.

The cathode of a lamp according to the invention' is made preferably of tantalum and comprises an emissive portion and an outer cooling jacket.

The aforesaidand other objects, features and advantages of the invention will be more easily and fully understood from the illustration of one embodiment of a flash lamp according to the invention, it being understood that the invention is not restricted to' the details of the illustrated and described embodiment but rather is susceptible to various modifications and adaptations.

In the attached drawing:

Fig. I is a View, partly in elevation and partly in section, of a lamp according to the invention;

Fig. 2 is a more detailed view in section of the cathode of the lamp shown in Fig. I;

Fig. 3 is an" exploded view of the various elements of the cathodeshown in Fig. 2;

Fig. 4 shows, mostly in section, the whole cathode assembly; and

Fig. 5 is a graph representing the power factors of a standard known lamp and of lamps according toth'e'invention.

Referring firstly to Fig. 1, the transparent tube or envelope in which is produced the luminous discharge is generally indicated by the numeral I". The lower part of said tube l' penetrates into a bulb or envelope 2', the cathode assembly 3 being disposed inside said bulb 2.

The cathode assembly 3, which will be described herein below, is shown with more detail in Figs. 2 and 4 and the elements of said cathode assembly are shown, as separate elements, in Fig. 3.

The bulb" 2 is sealed or cemented, according to the usual method, for a screw plug 4, used to supporting and connecting the flash lamp to a lamp-holder.

The upper part of tube 1 penetrates into a small bulb or envelope 5 inside which is also disposed the electrode forming the anode e of the flash tube, said anode preferably having the shape of an inverted bell. Said anode 6 made of a non-oxidizable metal and has sufficient surface for allowing dissipation of heat during the functioning of the lamp at ultra-high frequencies. A metallic connection 7, sealed to the anode 6, goes through said bulb 5, permitting circuit contact to be made. Thus the functional portion of the tube, according to the arrangement of the present invention, is localised within the tube 1 thereby providing a source of light having a small linear dimension.

The cathode (Figs. 2, 3 and 4) comprises a cylinder 8 supported by a glass pinch 9, a current feeding stem IU of tungsten or other suitable material and an exhaust tube ll, through which Vacuum is drawn prior to degassing, processing, activation and final gas filling, after which said tube I l is sealed off.

The active essential components of the cathode comprise a perforated cylinder [2, a spirally wound metallic element I3 and a cylinder [4. Said perforated cylinder I2, which can be omitted, is preferably made out of activated tantalum, thereby minimizing the voltage drop of this electrode and at the same time allowing considerably higher densities of current to be used. This construction also provides a larger surface for attracting the ions formed during flashing; this effect is further improved by the presence of the metallic spiral [3, made out of tantalum or other suitable metal and in direct thermal contact with and disposed around said cylinder [2.

The cathode assembly is completed by an outer cooling jacket or cylinder I4 preferably made of pure nickel, forming a chamber of de-ionization chamber, said cylinder I4 comprising at its lower end cooling elements such as the vanes or fins Hi. The leading edges of these vanes or fins play a very important part in the final dissipation of heat conducted away from the cathode. The useful emissive area and the de-ionization chamber are limited by a plate [6, to which is attached the eyelet H, for attachment to the tungsten stem [0, said plate I6 being connected to the tantalum cylinder I2. The upper part of cylinder [4 is turned inwardly and downwardly upon itself and penetrates inside the cathode in order to prevent the so-called brush or corona discharge effect during the function of the lamp.

Said cylinder M has also another extremely important object, i. e. to limit the discharge in space in such a manner so that no light appears in bulb 2. Furthermore the large ray emitting surfaces of said cylinder, combined with the vanes or fins I having a large number and area of leading edges, permit the production of flashes at a very much higher frequency than has been hitherto obtained with conventional tubes.

The envelope of the flash tube is filled with a mixture of rare gases preferably comprising xenon and krypton and exerting an internal pressure of approximately 1 to 10 mm. of mercury. The proportions of the rare gases may be substantially equal but they may also vary between the following limits: 4% to 90% xenon and 96% to 10% krypton. Argon may also be partially substituted for the xenon and/or krypton components of said rare gases.

The graph of Fig. 5 illustrates the improved performance obtained by the use of a flash tube according to the invention, when plotting the triggering voltages against the time.

The curve N represents the functional characteristics of conventional or normal tubes hitherto used.

The curve T shows the characteristics of an experimental tube according to the invention but not including the cooling devices or vanes [5.

The curve Q represents the characteristics of the same experimental tube but including a cathode and an anode designed and arranged in accordance with the practice of the present invention.

The curves of Fig. 5 show the important additional efiiciency obtained with the device of the invention; firstly, the lamps being provided with an activated and protected cathode have a triggering point much more clearly defined than the triggering point of a conventional or normal tube and secondly, the functional voltages being higher, the power factor of the discharges is much more important. Further it may be noted that the zone in which the tension, and therefore the luminous intensity, is constant shows a clearly defined and useful level much larger for a tube assembly according to the invention than for a conventional tube.

Accordingly, there has been provided a gas filled flash tube having an anode and a cathode; said cathode comprising a perforated cylindrical member, a spirally wound element surrounding said perforated cylindrical member, and an imperforate cylindrical member surrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member, said anode being disposed in spaced relation to said extremity of said imperforate cylindrical member.

Since certain modifications may be made in the deviceof the present invention without departing from the scope thereof, it is intended that all matter contained in the foregoing description and shown in the accompanying drawing be interpreted merely as illustrative and not in a limiting sense.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. A flash tube filled with a mixture of xenon, krypton and argon under a pressure inferior to 10 mm. of mercury comprising an anode and a cathode, said cathode comprising a perforated cylindrical sheet, a spiral wire around said perforated cylindrical sheet and a non-perforated cylindrical sheet around said spiral wire, said non-perforated cylindrical sheet having one extremity thereof internally inverted round and said anode being disposed in front of said internally inverted round extremity of said nonperforated sheet.

2. A flash tube filled with a mixture of xenon, krypton and argon under a pressure inferior to 10 mm. of mercury comprising an anode and a cathode, said cathode comprising a perforated cylindrical sheet, a spiral wire around said perforated cylindrical sheet and a non-perforated cylindrical sheet around said spiral wire, said non-perforated cylindrical sheet having one extremity thereof internally inverted round, said anode being disposed in front of said internally inverted round extremity of said non-perforated sheet and said non-perforated cylindrical sheet comprising cooling means.

3. A flash tube filled with a, mixture of xenon and krypton under a pressure inferior to 10 mm. of mercury comprising an anode and a cold cathode, said cathode comprising a perforated cylindrical sheet, a spiral wire around said per- .forated cylindrical sheet and a non-perforated cylindrical sheet around said spiral wire, said non-perforated cylindrical sheet having one extremity thereof internally inverted round and comprising at the other extremity thereof a series of cooling vanes or fins, said anode being disposed in front of said internally inverted round extremity of said non-perforated sheet.

4. A flash tube filled with a mixture of xenon and krypton under a pressure inferior to mm. of mercury comprising an anode and a cold cathode, said cathode comprising a perforated cylindrical sheet, a spiral wire around said perforated cylindrical sheet and a non-perforated cylindrical sheet around said spiral wire, said non-perforated cylindrical sheet having one extremity thereof internally inverted round and comprising at the other extremity thereof a series of cooling vanes or fins, said anode being disposed in front of said internally inverted round extremity of said non-perforated sheet and forming a bell of an inoxidable metal, the opening of said bell being directed towards said cathode.

5. A flash tube filled with a mixture of xenon and krypton under a pressure inferior to 10 mm. of mercury comprising an anode and a cold cathode, said cathode comprising a perforated cylindrical sheet of tantalum, a spiral wire of tantalum around said perforated cylindrical sheet and a non-perforated cylindrical sheet of pure nickel around said spiral wire, said nonperforated cylindrical sheet having one extremity thereof internally inverted round and comprising at the other extremity thereof a series of cooling vanes or fins, said anode being disposed opposite to said internally inverted round extremity of said non-perforated sheet and forming a bell of an inoxidable metal, the opening of said bell being directed towards said cathode.

6. A flash tube filled with a mixture of approximately equal proportions of xenon and krypton under a pressure of about 10 mm. of mercury comprising a spiral gas-filled tube made out of hard glass and including an anode and a cold cathode at the extremities thereof, said cathode comprising a perforated cylindrical sheet of tantalum, a spiral wire of tantalum around said perforated cylindrical sheet and a non-perforated cylindrical sheet of pure nickel around said spiral wire, said non-perforated cylindrical sheet having one extremity thereof internally inverted round and comprising at the other extremity thereof a series of cooling vanes or fins, said anode being disposed opposite to said internally inverted round extremity of said non-perforated sheet and forming a bell of an inoxidable metal, the opening of said bell being directed towards said cathode.

7. A gas filled fiash tube having an anode and a cathode; said cathode comprising a perforated cylindrical member, a spirally wound element surrounding said perforated cylindrical member, and an imperforate cylindrical member surrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member, said anode being disposed in spaced relation to said extremity of said imperforate cylindrical member.

8. A gas filled flash tube having an anode and a cathode; said cathode comprising a perforated cylindrical member, a spirally wound element surrounding said perforated cylindrical member,

andzanimperforate cylindrical\membersurrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said :perforated member, said anode being disposed in spaced relation to said extremity of said imperforate cylindrical member, said imperforate cylindrical member including cooling means, said anode and said cathode being disposed within an envelope containing a mixture of rare gases exerting an internal pressure less than approximately 10 mm. of mercury.

:9. A gas filled flash tube having an anode and .a cold cathode; said cathode comprising a perforated cylindrica'l member, a spirally wound element surrounding said perforated cylindrical member, and an imperforate cylindrical member surrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member and defining at the other extremity thereof a plurality of cooling elements, said anode being disposed in spaced relation to said first-mentioned extremity of said imperforate cylindrical member, said anode and said cathode being disposed within an envelope containing a mixture of xenon and krypton exerting an internal pressure less than approximately 10 mm. of mercury.

10. A gas filled flash tube having an anode and a cold cathode; said cathode comprising a perforated cylindrical member, a spirally wound element surrounding said perforated cylindrical member, and an imperforate cylindrical member surrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member and defining at the other extremity thereof a plurality of cooling vanes, said anode being disposed in spaced relation to said first-mentioned extremity of said imperforate cylindrical member and defining a bellshaped member of substantially non-oxidizable metallic material having an open end, the open end of said bell-shaped member being disposed towards said cathode, said anode and said cathode being disposed within an envelope containing a mixture of xenon and krypton exerting an internal pressure less than approximately 10 mm. of mercury.

11. A gas filled flash tube comprising an anode and a cold cathode, said cathode comprising a perforated cylindrical member consisting of tantalum, a spirally wound element consisting of tantalum surrounding said perforated cylindrical member and an imperforate cylindrical member consisting of pure nickel surrounding said spirally wound element, said imperforate cylindrical member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member and defining at the other extremity thereof a plurality of cooling fins, said anode being spaced from and disposed opposite said first-mentioned extremity of said imperforate cylindrical member and defining a bell-shaped, substantially non-oxidizable metallic member having an open end, the open end of said bellshaped member being disposed towards said cathode, said anode and said cathode being disposed within an envelope containing a mixture of xenon and krypton exerting an internal pressure less than approximately 10 mm. of mercury.

12. A flash lamp comprising a spiral gas-filled tube made of hard glass and including an anode and a cold cathode at opposite extremities thereof, said cathode comprising a perforated cylindrical member of tantalum, a spirally wound element of tantalum surrounding said perforated cylindrical member and an imperforate cylindrical member of pure nickel surrounding said spirally wound element, said imperforate member having one extremity thereof turned inwardly and downwardly upon itself and embraced by an adjacent end of said perforated member and defining at the other extremity thereof a plurality of cooling elements, said anode being spaced from and disposed opposite said first- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,831,950 Ewest Nov. 17, 1931 2,117,054 Boucher May 10, 1938 2,159,255 Clark May 23, 1939 2,567,369 Edwards Sept. 11, 1951

Images