US2914694A - Cathode assembly - Google Patents

Cathode assembly Download PDF

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US2914694A
US2914694A US688166A US68816657A US2914694A US 2914694 A US2914694 A US 2914694A US 688166 A US688166 A US 688166A US 68816657 A US68816657 A US 68816657A US 2914694 A US2914694 A US 2914694A
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cathode
sleeve
heat
cap
inch
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US688166A
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Chin Te Ning
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RCA Corp
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RCA Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
    • H01J3/02—Electron guns
    • H01J3/027—Construction of the gun or parts thereof

Definitions

  • TE NINE [II-1m imwnai M CATHODE ASSEMBLY Te Ning Chin, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application, ctober4, 1951, Serial No. 688,166
  • tube is a pickup, or camera, tube which is designed to be used in a portable television camera for use in a mobile television unit.
  • Aportable camera generally uses tran sis'tori zed circuit components which are light in weight and low in power consumption.
  • the pickup tube 'shouldalso be of the efficient, low power input, miniature, lightweight type.
  • a srnall,icompact, low wattage cathode is an esscntial part of, such a pickup tube.
  • a tubular cathode sleeve that is supported onlyat an end thereof remotefrom the electron emissive area of the cathode.
  • the support structure whichis-in the shape of a truncated c one cornpactly supports the cathode within a tubular shaped cathode shield with a maximum efliciency and minimum of heat .loss.
  • l-lig l is an enlargdplan view, partially in section, of a pickup tube utilizing this invention, and, Fig. 2 is an enlargedsectional view'of the cathode mount shown in Fig. 1.
  • a pickup tube embodying a" cathode structure in accordance with this invention is shown merely as an example of a type of tube whereimthis invention has been foundtobe especially useful.
  • the tube 10 comprises an evacuated glass. envelope 112 having an electron gun 14 in one end thereof.
  • the electron gun 14, which will be explained in detail hereinafter, is for the purpose of providing a beam of electrons which is controlled and/or accelerated down the tube by a control electrode 16, and an accelerating electrode 20 toward a target electrode 22.
  • One end of the accelerating electrode 20 is covered by a fine mesh screen 21 that is closely spaced adjacent to the target electrode 22.
  • the electron beam 1 United States Patent is focused onto, and deflected over, the target electrode 22 in any well-known manner, such as by means-of a focus coil and a deflection yoke, neither of which is shown for simplicity of illustration.
  • the target electrode 22 comprises a transparent support member 30, such as glass, which is shown as the end or face plate of the envelope 12.
  • a transparent conductive coating 32 which may comprise a coating of tin chloride or tin oxide.
  • a layer of photoconductive material 34 On the surface of c the transparent conductive coating 32 there is a layer of photoconductive material 34, which may be a ma- 12.
  • the sealing ring 31 is used as a lead-in for the conductive coating 32 during the operation of the tube 10.
  • a hollow, tubular cathode sleeve 36 which is made of a material having low heat conduction properties, such as a cobalt-nickel-iron alloy.
  • Press fitted into. and closing one end of the cathode sleeve 36 is a cathode cap 38, which is of a high heat conductivity metal, such as nickel.
  • the cathode cap 38 has a coating of electron emissive material on the surface thereof may be a material such as barium oxide and/ or strontium oxide.
  • the cathode cap 38 contacts the cathode sleeve 36'only in a relatively small area 37, which comprises a protuberance on the cap member 38 that is press fitted into the cathode sleeve 36.
  • the protuberance may be one'or more small indentationslor, in the alternative, a bead extending completely around the cap member 38.
  • the small contact area 37 results in heat conduction A paths from the cathode cap 38 to the cathode sleeve 36 of an extremely high thermal resistance.
  • a heater wire 40 which is formed of any material which A has an appropriate electrical resistance to produce relatively large amounts of heat for a relatively small amount of input power. Examples of such resistance materials are tungsten and/or molybdenum.
  • the turns of the heater wire 40 are within the cap 38 in order to con-j ,7 centrate the heat in this region.
  • the support member 42 contacts the cathode sleeve only at the smaller diameter 43 of the funnel shaped member 42.
  • Thecathode sleeve 36 may he spot welded or press fitted to the cathode suppo t 2-; 1 unnel shaped support member 42 is made of a material, such as a .CQbEItrHiCkfil-lIOH alloy,'having low heat conductionproperties. to minimize the heat losses to the other cathode support structures.
  • the funnel shaped member 42 is supported, such as by press fitting, at an end47, that is opposite to the end 43 that contacts the cathode member 36, by a tubular shaped cathode shield' 44,
  • The' cathode shield 44 is'also made of a material hayinglow heat conduction properties, such as a cobalt nickel iron alloy, to minimize heat losses.
  • the cathode shield 44 substantially encloses the funnel shaped member 42 and the cathode 36.
  • the cathode shield 44 is press fitted into another tubular shaped member 45 for the purpose of adding rigidity to the cathode mount.
  • the tubular shaped member 45 may also be a cobaltnickel-iron alloy to minimize heat losses. Another reason for the presence of the tubular shaped member 45 Patented Nov. 24, less mount, could be withdrawn and replaced by another cathode assembly. a
  • the members of the cathode mount are machined so as to be as thin as possible, and still provide suitable strength, in order to further increase the thermal resistance of the heat conduction paths away from thecathode cap 38. Also, due to the geometry of the cathode mount, the heat conduction paths are long, while still within a compact volume, and therefore the thermal resistance of the heat conduction paths from the cathode cap is further increased.
  • the cathode support 42 is joined to the cathode sleeve 36 only adjacent to the end of the sleeve'36 remote from the electron emissive area, and, the otherend of the cathode support 42 is the only area of the cathode support 42 that contacts the cathode shield 45.
  • the materials, thickness and geometry of the cathode mount are such as to provide an efficient, miniature, heat conserving cathode structure.
  • the cathode mount assembly shown in Fig. 1 is highly efiicient from a heat radiation standpoint also, in that the funnel shaped support member 42 and the cathode shield member 44 are heat reflectors and are provided with bright inner surfaces to reflect as much heat as possible back toward the cathode cap 38.
  • the balance of the electron gun 14 is conventional in that the first control electrode 16 is positioned adjacent to the cathode cap 38.
  • the elements of the gun structure 14 are supported by means of glass side rods 46 which are fixed to the particular electrodes in a well-known manner.
  • the cathode mount is extremely small and compact and is highly eflicient, as was explained, in that the heat generated by the heater wires 40 is conserved by the compact structure whereby a maximum of electron emission is obtained with a minimum heat loss.
  • This eflicient, compact structure is readily adaptable for use in portable television camera tubes, such as the /2" Vidicon type tube.
  • the cathode When the cathode is assembled, the cathode maybe fabricated by concentric, self-jigging parts, since the parts are substantially coaxial, and thus can easily be assembled in a few steps.
  • the junctions of the various cathode parts may be formed by press fitting or by spot welding.
  • the cathode mount assembly is free of any insulating members, such as mica, which is often found in the prior art structures.
  • the insulating members may tend to cause loose particles within the tube 10 by flaking of the insulator during tube processing or operation. The loose particles are particularly harmful in a pickup tube if they should land on the photoconductor or on the screen of the final accelerating electrode.
  • the cathode mount assembly is made only of metal which may actually be made more heat insulating than materials that are electrical insulators, 'due to the fact that the metal may be machined to extremely fine thicknesses.
  • electrical insulators e.g., mica, cannot be machined to these fine thicknesses and still provide adequate support for the cathode mount.
  • the particular cathode assembly described produces an electron beam suitable for operation of a television pickup tube with an input power of approximately 0.6 of a watt.
  • the low power, compact cathode assembly I is extremely useful as a cathode in a pickuptube in portable-televisioncameras.
  • a cathode mount assembly comprising a hollow metallic cylindrical cathode sleeve member a metallic cathode cap member closing one end of said sleeve member, electron emissive material on said cap member, a hollow metallic truncated conical support member, the smaller end of said support member engaging the other end of said sleeve member, the larger end of said support member being arranged around said sleeve member Material Nickel Length inch .040 Width inch .045 Thickness inch .002
  • a hollow cylindrical metallic cathode shield spaced concentrically around said support member, one end ofsaid cathode shield engaging said larger end of said support member, a cathode lead-in connected to said shield adjacent to the other end of said shield, and aheater coil within said sleeve member, the turns of said heater coil being concentrated adjacent to said one end of said sleeve member;

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  • Electrodes For Cathode-Ray Tubes (AREA)

Description

TE NING CHIN CATHODE ASSEMBLY 7 Nov. 24, 1959 Filed Oct. 4, 1957 INVENTOR. TE NINE [II-1m imwnai M CATHODE ASSEMBLY Te Ning Chin, Lancaster, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application, ctober4, 1951, Serial No. 688,166
2 Claims. (Cl. 313270) tube is a pickup, or camera, tube which is designed to be used in a portable television camera for use in a mobile television unit. Aportable camera generally uses tran sis'tori zed circuit components which are light in weight and low in power consumption. In television cameras of this type, the pickup tube 'shouldalso be of the efficient, low power input, miniature, lightweight type. Thus, a srnall,icompact, low wattage cathode is an esscntial part of, such a pickup tube.
It is" therefore an object of this invention to provide a new and improved cathode structure.
-It-is another object of this invention -to provide an improved miniature'cathode mount that efliciently uses the input power. 1. 4
-These objects, as well as others, are accomplished in accordance with this invention by providing a tubular cathode sleeve that is supported onlyat an end thereof remotefrom the electron emissive area of the cathode. The support structure, whichis-in the shape of a truncated c one cornpactly supports the cathode within a tubular shaped cathode shield with a maximum efliciency and minimum of heat .loss.
The invention will be ,more clearlyunderstood by reference to theaccompan'ying single sheet of drawings whe in: r
l-lig l is an enlargdplan view, partially in section, of a pickup tube utilizing this invention, and, Fig. 2 is an enlargedsectional view'of the cathode mount shown in Fig. 1.
Referring nowto Fig. -1, there is shown, a pickup tube embodying a" cathode structure in accordance with this invention. .It should be understoodthat the invention is equally, applicable to other types of tubes, such as electron beamtubes,'wherein small, efiicient cathodes are desired, and the pickuprtnbe. 10 is shown merely as an example of a type of tube whereimthis invention has been foundtobe especially useful. The tube 10 comprises an evacuated glass. envelope 112 having an electron gun 14 in one end thereof. The electron gun 14, which will be explained in detail hereinafter, is for the purpose of providing a beam of electrons which is controlled and/or accelerated down the tube by a control electrode 16, and an accelerating electrode 20 toward a target electrode 22. One end of the accelerating electrode 20 is covered by a fine mesh screen 21 that is closely spaced adjacent to the target electrode 22. The electron beam 1 United States Patent is focused onto, and deflected over, the target electrode 22 in any well-known manner, such as by means-of a focus coil and a deflection yoke, neither of which is shown for simplicity of illustration.
The target electrode 22 comprises a transparent support member 30, such as glass, which is shown as the end or face plate of the envelope 12. On the inner surface of the transparent support member 30' there is a transparent conductive coating 32 which may comprise a coating of tin chloride or tin oxide. On the surface of c the transparent conductive coating 32 there is a layer of photoconductive material 34, which may be a ma- 12. The sealing ring 31 is used as a lead-in for the conductive coating 32 during the operation of the tube 10. The electron gun 14, as shown more clearly in Fig. 2,
includes. a hollow, tubular cathode sleeve 36 which is made of a material having low heat conduction properties, such as a cobalt-nickel-iron alloy. Press fitted into. and closing one end of the cathode sleeve 36 is a cathode cap 38, which is of a high heat conductivity metal, such as nickel. The cathode cap 38 has a coating of electron emissive material on the surface thereof may be a material such as barium oxide and/ or strontium oxide. The cathode cap 38 contacts the cathode sleeve 36'only in a relatively small area 37, which comprises a protuberance on the cap member 38 that is press fitted into the cathode sleeve 36. The protuberance may be one'or more small indentationslor, in the alternative, a bead extending completely around the cap member 38.
The small contact area 37 .results in heat conduction A paths from the cathode cap 38 to the cathode sleeve 36 of an extremely high thermal resistance.
Within thetubular cathode sleeve 36, and closely spaced from the inner surface of the cathode cap 38, is a heater wire 40 which is formed of any material which A has an appropriate electrical resistance to produce relatively large amounts of heat for a relatively small amount of input power. Examples of such resistance materials are tungsten and/or molybdenum. The turns of the heater wire 40 are within the cap 38 in order to con-j ,7 centrate the heat in this region.
sections 43 and 47. The support member 42 contacts the cathode sleeve only at the smaller diameter 43 of the funnel shaped member 42. Thecathode sleeve 36 may he spot welded or press fitted to the cathode suppo t 2-; 1 unnel shaped support member 42 is made of a material, such as a .CQbEItrHiCkfil-lIOH alloy,'having low heat conductionproperties. to minimize the heat losses to the other cathode support structures. The funnel shaped member 42 is supported, such as by press fitting, at an end47, that is opposite to the end 43 that contacts the cathode member 36, by a tubular shaped cathode shield' 44, The' cathode shield 44 is'also made of a material hayinglow heat conduction properties, such as a cobalt nickel iron alloy, to minimize heat losses. The cathode shield 44 substantially encloses the funnel shaped member 42 and the cathode 36. The cathode shield 44 is press fitted into another tubular shaped member 45 for the purpose of adding rigidity to the cathode mount. The tubular shaped member 45 may also be a cobaltnickel-iron alloy to minimize heat losses. Another reason for the presence of the tubular shaped member 45 Patented Nov. 24, less mount, could be withdrawn and replaced by another cathode assembly. a
In addition to the high thermal resistance materials used in the cathode mount members, the members of the cathode mount are machined so as to be as thin as possible, and still provide suitable strength, in order to further increase the thermal resistance of the heat conduction paths away from thecathode cap 38. Also, due to the geometry of the cathode mount, the heat conduction paths are long, while still within a compact volume, and therefore the thermal resistance of the heat conduction paths from the cathode cap is further increased. As an example, the cathode support 42 is joined to the cathode sleeve 36 only adjacent to the end of the sleeve'36 remote from the electron emissive area, and, the otherend of the cathode support 42 is the only area of the cathode support 42 that contacts the cathode shield 45. Thus, the materials, thickness and geometry of the cathode mount are such as to provide an efficient, miniature, heat conserving cathode structure.
The cathode mount assembly shown in Fig. 1 is highly efiicient from a heat radiation standpoint also, in that the funnel shaped support member 42 and the cathode shield member 44 are heat reflectors and are provided with bright inner surfaces to reflect as much heat as possible back toward the cathode cap 38.
The balance of the electron gun 14 is conventional in that the first control electrode 16 is positioned adjacent to the cathode cap 38. The elements of the gun structure 14 are supported by means of glass side rods 46 which are fixed to the particular electrodes in a well-known manner.
The cathode mount is extremely small and compact and is highly eflicient, as was explained, in that the heat generated by the heater wires 40 is conserved by the compact structure whereby a maximum of electron emission is obtained with a minimum heat loss. This eflicient, compact structure is readily adaptable for use in portable television camera tubes, such as the /2" Vidicon type tube.
When the cathode is assembled, the cathode maybe fabricated by concentric, self-jigging parts, since the parts are substantially coaxial, and thus can easily be assembled in a few steps. The junctions of the various cathode parts may be formed by press fitting or by spot welding.
A particular example of materials and sizes for use in the cathode mount described is an follows:
Cathode cap 38:
. 4 Cathode shield 44:
Material Nickel-cobalt-iron alloy Length inch .275 Width inch .191 Thickness inch .005
Cathode member 45: Q
Material Nickel-cobalt-iron alloy Length in h .216 Diameter inch .201 Thickness inch .005
It should be noted'thatthe cathode mount assembly is free of any insulating members, such as mica, which is often found in the prior art structures. The insulating members may tend to cause loose particles within the tube 10 by flaking of the insulator during tube processing or operation. The loose particles are particularly harmful in a pickup tube if they should land on the photoconductor or on the screen of the final accelerating electrode. Also, it should be noted that the cathode mount assembly is made only of metal which may actually be made more heat insulating than materials that are electrical insulators, 'due to the fact that the metal may be machined to extremely fine thicknesses. On the other hand, electrical insulators, e.g., mica, cannot be machined to these fine thicknesses and still provide adequate support for the cathode mount.
The particular cathode assembly described produces an electron beam suitable for operation of a television pickup tube with an input power of approximately 0.6 of a watt. Thus, the low power, compact cathode assembly I is extremely useful as a cathode in a pickuptube in portable-televisioncameras.
What is claimed is: v
1. A cathode mount assembly comprising a hollow metallic cylindrical cathode sleeve member a metallic cathode cap member closing one end of said sleeve member, electron emissive material on said cap member, a hollow metallic truncated conical support member, the smaller end of said support member engaging the other end of said sleeve member, the larger end of said support member being arranged around said sleeve member Material Nickel Length inch .040 Width inch .045 Thickness inch .002
Funnel shaped support member 42:
Material Nickel-cobalt-iron alloy Length inch ,177 Large diameter inch .178 Small diameter inch .048 Thickness inch. .001
Length of top and bottom parallel walls inch .019
Cathode sleeve 36:
adjacent to said one end offs'aid sleeve member, a hollow cylindrical metallic cathode shield spaced concentrically around said support member, one end ofsaid cathode shield engaging said larger end of said support member, a cathode lead-in connected to said shield adjacent to the other end of said shield, and aheater coil within said sleeve member, the turns of said heater coil being concentrated adjacent to said one end of said sleeve member; I
. 2. A cathode mount assembly as in claim 1 wherein said metallic members have a thickness not greater than .005 inch whereby the heat conductionpaths of said members are of high resistance. l
References Cited in the tile of this patent Great Britain Oct. 24, 1956
US688166A 1957-10-04 1957-10-04 Cathode assembly Expired - Lifetime US2914694A (en)

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Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3025418A (en) * 1959-12-24 1962-03-13 United Aircraft Corp Quadrature stripping circuit
US3047758A (en) * 1959-12-01 1962-07-31 Machlett Laboraotries Inc Cathode ray tubes
US3065374A (en) * 1959-10-12 1962-11-20 Varian Associates Low noise electron discharge device
US3087082A (en) * 1960-02-09 1963-04-23 Rca Corp Cathode-ceramic assembly for electron guns and method of making
US3145318A (en) * 1960-11-14 1964-08-18 Rca Corp Cathode grid assembly for electron gun
US3254251A (en) * 1962-07-06 1966-05-31 Rca Corp Cathode ray tube gun having nested electrode assembly
US3333138A (en) * 1965-01-11 1967-07-25 Rauland Corp Support assembly for a low-wattage cathode
JPS49123569A (en) * 1973-03-20 1974-11-26
US4071803A (en) * 1974-09-19 1978-01-31 Tokyo Shibaura Electric Co., Ltd. Electron gun assembly
EP0022201A1 (en) * 1979-06-21 1981-01-14 Kabushiki Kaisha Toshiba Cathode assembly
FR2481516A1 (en) * 1980-04-23 1981-10-30 Philips Nv
US4514660A (en) * 1983-11-29 1985-04-30 Rca Corporation Cathode-ray tube having an electron gun assembly with a bimetal cathode eyelet structure
US4554480A (en) * 1983-11-29 1985-11-19 Rca Corporation Cathode-ray tube having an electron gun assembly with emissivity modifying means

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB499532A (en) * 1937-11-15 1939-01-25 Gen Electric Co Ltd Improvements in or relating to cathode ray tubes and the like
US2740913A (en) * 1951-11-01 1956-04-03 Itt Electron gun
GB759944A (en) * 1954-03-02 1956-10-24 Gen Electric Co Ltd Improvements in or relating to electric circuit arrangements incorporating cathode ray tubes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB499532A (en) * 1937-11-15 1939-01-25 Gen Electric Co Ltd Improvements in or relating to cathode ray tubes and the like
US2740913A (en) * 1951-11-01 1956-04-03 Itt Electron gun
GB759944A (en) * 1954-03-02 1956-10-24 Gen Electric Co Ltd Improvements in or relating to electric circuit arrangements incorporating cathode ray tubes

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3065374A (en) * 1959-10-12 1962-11-20 Varian Associates Low noise electron discharge device
US3047758A (en) * 1959-12-01 1962-07-31 Machlett Laboraotries Inc Cathode ray tubes
US3025418A (en) * 1959-12-24 1962-03-13 United Aircraft Corp Quadrature stripping circuit
US3087082A (en) * 1960-02-09 1963-04-23 Rca Corp Cathode-ceramic assembly for electron guns and method of making
US3145318A (en) * 1960-11-14 1964-08-18 Rca Corp Cathode grid assembly for electron gun
US3254251A (en) * 1962-07-06 1966-05-31 Rca Corp Cathode ray tube gun having nested electrode assembly
US3333138A (en) * 1965-01-11 1967-07-25 Rauland Corp Support assembly for a low-wattage cathode
US3895249A (en) * 1973-03-20 1975-07-15 Int Standard Electric Corp Instant warm-up heater cathode
JPS49123569A (en) * 1973-03-20 1974-11-26
JPS559127B2 (en) * 1973-03-20 1980-03-07
US4071803A (en) * 1974-09-19 1978-01-31 Tokyo Shibaura Electric Co., Ltd. Electron gun assembly
EP0022201A1 (en) * 1979-06-21 1981-01-14 Kabushiki Kaisha Toshiba Cathode assembly
US4370588A (en) * 1979-06-21 1983-01-25 Tokyo Shibaura Denki Kabushiki Kaisha Cathode assembly
FR2481516A1 (en) * 1980-04-23 1981-10-30 Philips Nv
US4514660A (en) * 1983-11-29 1985-04-30 Rca Corporation Cathode-ray tube having an electron gun assembly with a bimetal cathode eyelet structure
US4554480A (en) * 1983-11-29 1985-11-19 Rca Corporation Cathode-ray tube having an electron gun assembly with emissivity modifying means

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