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GB2132012A - Protective base for an electron discharge tube - Google Patents

Protective base for an electron discharge tube Download PDF

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Publication number
GB2132012A
GB2132012A GB08332781A GB8332781A GB2132012A GB 2132012 A GB2132012 A GB 2132012A GB 08332781 A GB08332781 A GB 08332781A GB 8332781 A GB8332781 A GB 8332781A GB 2132012 A GB2132012 A GB 2132012A
Authority
GB
United Kingdom
Prior art keywords
base
lead
envelope
tube
conductor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB08332781A
Other versions
GB2132012B (en
GB8332781D0 (en
Inventor
Marinus Vanrenssen
Gardner Luther Fassett
Myron Henry Wardell
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Publication of GB8332781D0 publication Critical patent/GB8332781D0/en
Publication of GB2132012A publication Critical patent/GB2132012A/en
Application granted granted Critical
Publication of GB2132012B publication Critical patent/GB2132012B/en
Expired legal-status Critical Current

Links

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/92Means forming part of the tube for the purpose of providing electrical connection to it
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/24Manufacture or joining of vessels, leading-in conductors or bases
    • H01J9/34Joining base to vessel
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/50Means forming part of the tube or lamps for the purpose of providing electrical connection to it
    • H01J5/54Means forming part of the tube or lamps for the purpose of providing electrical connection to it supported by a separate part, e.g. base
    • H01J5/58Means for fastening the separate part to the vessel, e.g. by cement

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
  • Insulating Bodies (AREA)
  • Casting Or Compression Moulding Of Plastics Or The Like (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)

Abstract

A protective base 20 for a color picture tube type of electron discharge tube having an evacuated envelope is formed in situ. At least one lead-in conductor 14' is sealed through the envelope, an insulative member 28 disposed around the lead-in conductor so that the insulative member contacts the outer surface of the envelope, and an electrically insulating material 20 is moulded about at least a portion of the insulative member 28, thereby compressibly retaining the insulative member in contact with the outer surface of said envelope. The base 20 may be of polysulphone whilst the member 28 is of silicone resin. Various configurations are shown for the member 28 (Figures 4 to 6). A silo 26 is provided to give a long leakage path between the high voltage electrode 14' and the other electrodes. <IMAGE>

Description

SPECIFICATION Protective base for an electron discharge tube and method for making the same The present invention relates to a base for an electron tube, and particularly to a base which is molded, in situ, directly to the electron tube.
Certain types of electron tubes, e.g., color picture tubes, include a stem structure comprising a glass disk, a circular array of stiff lead-in conductors sealed through the disk, and a central opening through the disk from which an exhaust tubulation extends. It is common practice to attach a base, usually of some type of plastic material, over the conductors and exhaust tubulation. The base serves to protect the conductors and the exhausttubula- tion, and to provide an indexing means for insertion into a mating socket.
One type of base commonly employed in the picture tube industry is the flanged base which comprises a protector cup or housing disposed over the exhaust tubulation of an electron tube stem, and a flange which extends radially outwardly from the open end of the cup. The flange is abutted against the tube stem and is provided with an array of apertures through which the conductors of the stem are disposed.
U.S. Patent Nos. 3, 278, 886 (Blumenberg et al., 11 October 1966) and 4,076,366 (Wardell, Jr. et al., 28 February 1978) disclose flanged type bases, both of which are especially designed for high voltage applications. For this purpose, they incorporate a tubular silo structure which surrounds one of the conductors to which high voltage is applied, and a recess in the flange of the base into which a dielectric adhesive material is molded around the high voltage conductor. Both of these features serve to increase resistance against high voltage breakdown.
In the base of U.S. Patent No. 3, 278,886, the conductors are spaced outwardly from the exhaust tubulation cup and are thus free-standing. This type of flanged base is sometimes referred to as a wafer base. In the base of U.S. Patent No. 4,076,366, the conductors lie flush against the cup in channel-like grooves around the periphery of the cup. This type of flanged base is sometimes referred to as a pin-protector base.
The latter base is provided with a fill hole which communicates with a recess in the flange of the base so that dielectric adhesive can be injected directly into the recess through the fill hole. However, in the case of electron tubes having very small diameter stems, there may not be sufficient room in the base for the fill hole. In such a case, bases more like the former base are used.
In mounting a base of the former type to an electron tube stem, it has been the practice heretofore to simply insert a quantity of dielectric adhesive material, such as RTV (trade mark), directly into the recess of the base and then apply the base to the stem. Since the dielectric adhesive material is applied to the base while it is out of contact with the stem, the result is a messy process. Alternatively, the dielectric adhesive material may be injected through the exhaust tubulation housing. In order for the material to flow along the length of the housing to the recess in the base flange and around the high voltage conductor, sufficient clearance must be provided between the exhaust tubulation and the housing wall; but this conflicts with the need to keep the exhaust tubulation as large as possible in order to facilitate the exhausting of the electron tube therethrough.Often, the result is that adequate clearance for good flow of the material along the tubulation is compromised.
Furthermore, the concentricity variation between the tubulation and housing may result in the greatest clearance, and hence the preferential material flow path, being along onesideofthetubulation opposite the recess so that the flow path does not communicate with the recess in the base flange. This, of course, results in unpredictable filling of the recess and sometimes no filling at all.
An alternative to utilizing a dielectric adhesive material to provide high voltage protection is disclosed in U.S. Patent No. 4,040,707 (Pisano, August 1977), which discloses one drawback of the dielectric adhesive to be the long time required for the adhesive material to cure. The structure of this patent utilizes an insulating plug of silicone rubber shaped as a segmented washer which fits over the high voltage conductor. The silicone washer has an adhesive on both sides to secure the insulating plug between the tube stem and the plastic base. The base is secured to the neck of the tube by use of an electrically insulating cement, as in the prior art. U.S.
Patent No.4,040,708 (Neuber et al., 9August1977) discloses a structure similar to the structure of U.S.
Patent No. 4,040,707, in which a rubber washer is fit over all the conductors and secured to a base by means of a suitable adhesive cement, such as rubber cement or RTV (trade mark).
While both the last two structures avoid using a dielectric adhesive material for electrical isolation, a dielectric adhesive material is nevertheless used to secure the base to the tube. Thus, the mess and long cure time associated with the use of a dielectric adhesive material is not avoided by the patentees of these structures.
U.S. Patent No.4,155,618 (Regnault et al., 22 May 1979) proposes the use of a deformable electrically insulative elastic gasket of a complex configuration, which has a portion comprising a substantially cylindrical projection which is inserted into a cavity in the base. The elastic gasket provides electrical isolation of the high voltage conductor from adjacent conductors, while securing the base against the stem of the tube without using a dielectric adhesive material. A drawback of this structure is that the tolerances between the cavity diameter and the diameter of the cylindrical projection on the gasket do not always permit the projection on the gasket to fitfully into the cavity in the base.Thus, a firm seal is not always made around the high voltage conductor, and electrical leakage and arcing sometimes occur between the high voltage conductor and adjacent conductors.
Another alternative to the above-described use of a dielectric adhesive material for affixing flange-type bases to tubes is to mold the base directly to the stem of the tube. Such a base is disclosed in U.S.
Patent No. 2,424,990 (Krim, 5 August 1947). An apparatusforforming a base directly on the stem of a tube is described in U.S. Patent No. 2,433,373 (Krim, 30 December 1947). A drawback of that molded-in-situ base is its inability to withstand the high processing and operating voltages which are applied to modern color picture tubes. In the manufacture of such tubes, it is desirable to apply a "spot-knocking" voltage of approximately 20 kilovolts through the base and stem of the tube in order to remove sharp points and particles from elements of the electron gun. The base of U.S. Patent No.
2,424,990 is unable to withstand a voltage of this magnitude.
It is therefore desirable to provide a tube base that can be applied quickly, cleanly and reliably, to obtain the high voltage breakdown protection required by modern picture tubes.
In accordance with the present invention, a protective base for an electron discharge tube having an evacuated envelope is formed, in situ. The envelope has an outer surface and at least one lead-in conductor which is sealed through the envelope. The protective base is attached directly to the outside surface of the envelope. The method of the invention includes the steps of disposing an insulative member around the lead-in conductor so that the insulative member contacts the outer surface of the envelope, and then molding an electrically insulating material about at least a portion of the insulative member, thereby compressibly retaining the insulative member in contact with the outer surface of said envelope.
In the drawings: Figure 1 is a perspective view of a stem-containing portion of a cathode ray tube, together with a formed-in-place base according to the present invention.
Figure 2 is a plan view of the structure shown in Figure 1.
Figure 3 is a sectional view of the stem-containing portion of the cathode ray tube insulative member and base according to the present invention.
Figure 4 is an enlarged fragmentary view of the insulative member of Figure 3.
Figures 5-6 show fragmentary views of alternative configurations of an insulative member which is retained against the stem-containing portion of the cathode ray tube by the formed-in-place base.
Figure 7shows a sectional view of a mold positioned on the stem-containing portion of the cathode ray tube.
Referring to Figures 1-3, a glass neck portion 10 of a cathode ray tube is closed at one end with a stem 12, which includes an array of stiff lead-in conductors 14, sealed through a glass disc 16. The conductors 14 are disposed parallel to each other in a circular array. The stem 12 also includes a closed-off exhausttubulation 18 disposed centrally of the disc 16. The exhausttubulation 18 provides access through the disc 16 to the interior of the cathode ray tube. A protective base 20 of a moldable electrically insulating material is formed, in situ, and attached to the stem 12 in any suitable manner, as by being molded thereon. A suitable material for the base 20 is a heat-resistant polysulfone resin.
The base 20 comprises a flange portion 22 and a cylindrical housing 24. The flange portion 22 sur rounds and firmly anchors each of the conductors 14 which project therefrom as external leads, thereby providing additional support thereto. The cylindrical housing 24 embraces and reinforces the exhaust tubulation 18, thereby greatly strengthening the tubulation. The base 20 further includes a silo 26 disposed coextensively along side the housing 24.
The silo 26 is closed at one end by the flange 22 and is open at the opposite end. The silo 26 encloses one of the conductors 14', which is intended to have a high voltage applied thereto. The silo 26 serves to provide a greatly increased discharge path from the high voltage conductor 14' contained therein to any one of the lower voltage conductors 14 adjacent thereto.
In order to prevent electrical leakage along the surface of the glass disc 16 from the high voltage conductor 14' to the adjacent conductors 14, an insulative member 28, preferably formed from heatresistant resilient silicone of high dielectric strength, is disposed around the conductor 14'. The insulative member 28, shown in detail in Figure 4, comprises an annular ring or washer having an outside diameter of about 3mm, an inside diameter of about 1 mm and a height of about 3mm. The insulative member 28 is compressed against the outer surface ofthe glass disc 16 and retained in contact therewith by the base material, which is molded about and encloses at least a portion of the insulative member 28.Since it is difficult to bond to silicone, the exterior surface of the insulative member 28 may be provided with an irregular shape to increase the contact between the moldable material of the base 20 and the insulative member 28.
Figures 5 and 6 show two alternative configurations for the insulative member which increase the mechanical coupling to the moldable material of the base 20. In Figure 5, a step 30 is formed in an insulative member 28'. The step 30 is disposed against the glass disc 16 so that the moldable material of the base 20 covers the step 30 and locks the insulative member 28' against the disc 16, thereby reducing electrical leakage from the conductor 14' along the interface between the glass disc 16 and the insulative member 28'. A second alternative configuration for the insulative member is shown in Figure 6. A recess 32 is formed in the outside surface of an insulative member 28". The recess 32 is covered by the moldable material which locks the member 28" therein, so that the insulative member 28" is compressed against and held in contact with the glass disc 16 of the stem 12.
A mold 40, shown in Figure 7, may be used to form the base 20. Following the steps of bake-out, exhaust, and tip-off of the exhaust tubulation, the insulative member 28 is disposed around the conductor 14', and the mold 40 is disposed overthe exhaust tubulation 18 and attached to the cathode ray tube. At this step in the process, the tube envelope is at a temperature of about 1 500C. The mold 40 has a plurality of apertures which conform closely to the conductors 14 and 14'. The mold 40 includes a gasket 42 to restrict the flow of the moldable material. Suitable means (not shown) are used to attach the mold 40 to the neck portion 10 of the cathode ray tube. The mold 40 includes a passageway 44 which communicates with a central chamber 46. The polysulfone resin is injected at low pressure and at a temperature of about 380-450"C into the passageway 44 of the mold 40. The resin cures in about 30 seconds to form the base 20, at which point the mold 40 can be removed, and the tube can be sent to post processing.

Claims (12)

1. A method for forming, in situ, a protective base for an electron discharge tube having an evacuated envelope with an outer surface, said envelope including at least one lead-in conductor sealed therethrough, and said protective base being attached directly to said outside surface of said envelope, comprising the steps of: disposing an insulative member around said leadin conductor so that said insulative member contacts said outer surface of said envelope; and molding an electrically insulating material about at least a portion of said insulating member, thereby compressively retaining said insulative member in contact with said outer surface of said envelope.
2. The method of Claim 1, further including, subsequent to said disposing step, the steps of: attaching a mold to said tube, said mold having a central chamber; injecting said electrically insulating material into said central chamber at a temperature greater than said tube temperature; and removing said mold after said electrically insulating material has cured to form said base.
3. The method of Claim 2, further including the step of heating said electrically insulating material to a temperature of about 380 to 450"C prior to injecting said material into said central chamber of said mold.
4. An electron discharge tube having an evacuated envelope with an outer surface and at least one lead-in conductor sealed therethrough, and a protective base attached directly to said outer surface of said envelope, comprising: a resilient annular insulative member disposed around and in contact with said lead-in conductor, said insulative member being compressed against and retained in contact with said outer surface of said envelope by a portion of said base which encloses at least a portion of said insulative member.
5. Acathode ray tube including, in combination, an evacuated envelope having a stem portion with an exhaust tubulation therethrough, and a protective base directly attached to said stem portion of said envelope, said base completely encapsulating said exhausttubulation, said stem portion including an array of lead-in conductors sealed therethrough, and said lead-in conductors being securely anchored in said base and projecting therefrom as external leads, wherein: said protective base is formed, in situ, from a heat resistant polysulfone resin; and a resilient annular insulative member is disposed around at least one of said lead-in conductors and in contact therewith, said insulative member being compressed against said stem portion and retained in contact therewith by said polysulfone resin which encloses at least a portion of said insulative member.
6. The tube as in Claim 5, wherein said base includes a silo spaced from but substantially enclosing said lead-in conductor having said insulative member disposed therearound, said silo having an opening at an end thereof to provide access to said lead-in conductor.
7. The tube as in Claim 6, wherein said resilient annular insulative member comprises a heatresistant silicone washer having a dielectric strength sufficient to prevent electrical leakage between said silicone washer and said stem portion of said envelope in contact therewith.
8. The tube as in Claim 7, wherein said silicone washer has an irregularly shaped outside surface which is in contact with said polysulfone resin.
9. The tube as in Claim 8, wherein the irregularly shaped outside surface of said silicone washer includes a recess formed therein.
10. The tube as in Claim 8, wherein the irregularly shaped outside surface of said silicone washer includes a step-like portion adjacent to said stem portion of said envelope.
11. A cathode ray tube including, in combination, an evacuated envelope having a stem portion with an exhaust tubulation therethrough, and a protective base directly attached to said stem portion of said envelope, said base completely encapsulating said exhaust tubulation, said stem portion including an array of lead-in conductors sealed therethrough for providing a plurality of voltages to said tube, at least one of said lead-in conductors being a higher voltage lead-in conductor than the lead-in conductors adjacent thereto, and each of said lead-in conductors being securely anchored in said base and projecting therefrom as external leads, wherein:: said protective base is formed, in situ, from a heat resistant polysulfone resin, said base including a silo spaced from but substantially enclosing said higher voltage lead-in conductor, and said silo having an opening at an end thereof to provide access to said higher voltage lead-in conductor; and a heat resistant, resilient annular silicone washer is disposed around said higher voltage lead-in conductor and in contact therewith, said silicone washer being compressed against and held in contactwith said stem portion of said envelope by said polysulfone resin which encloses at least a portion of said silicone washer, thereby preventing electrical leakage between said higher voltage leadin conductor and the lead-in conductors adjacent thereto.
12. A method of providing an electron discharge tube with a protective base, or such tube so provided, substantially as hereinbefore described with reference to the accompanying drawings.
GB08332781A 1982-12-16 1983-12-08 Protective base for an electron discharge tube Expired GB2132012B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US45021282A 1982-12-16 1982-12-16

Publications (3)

Publication Number Publication Date
GB8332781D0 GB8332781D0 (en) 1984-01-18
GB2132012A true GB2132012A (en) 1984-06-27
GB2132012B GB2132012B (en) 1986-04-03

Family

ID=23787221

Family Applications (1)

Application Number Title Priority Date Filing Date
GB08332781A Expired GB2132012B (en) 1982-12-16 1983-12-08 Protective base for an electron discharge tube

Country Status (7)

Country Link
JP (1) JPS59119656A (en)
KR (1) KR840007304A (en)
CA (1) CA1195373A (en)
DE (1) DE3345636A1 (en)
FR (1) FR2538162A1 (en)
GB (1) GB2132012B (en)
IT (1) IT1168981B (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991015039A1 (en) * 1990-03-20 1991-10-03 Reynolds Industries, Incorporated Releasable connector assembly for cathode ray tube
GB2282004A (en) * 1993-09-21 1995-03-22 Sony Corp An insulator, e.g. for the terminals of a CRT

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000011922A (en) 1998-06-25 2000-01-14 Toshiba Corp Color picture tube

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0014550A1 (en) * 1979-01-31 1980-08-20 Rca Corporation Method for assembling a base to an electron tube

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4064412A (en) * 1976-07-02 1977-12-20 Gte Sylvania Incorporated Cathode ray tube base
GB1536777A (en) * 1976-07-22 1978-12-20 Ferranti Ltd Electrical component assemblies
US4155618A (en) * 1978-01-19 1979-05-22 Rca Corporation Base assembly for an electron tube

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0014550A1 (en) * 1979-01-31 1980-08-20 Rca Corporation Method for assembling a base to an electron tube

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991015039A1 (en) * 1990-03-20 1991-10-03 Reynolds Industries, Incorporated Releasable connector assembly for cathode ray tube
GB2282004A (en) * 1993-09-21 1995-03-22 Sony Corp An insulator, e.g. for the terminals of a CRT
GB2282004B (en) * 1993-09-21 1997-06-25 Sony Corp An electric insulator and method of use thereof
US5990610A (en) * 1993-09-21 1999-11-23 Sony Corporation Manufacturing method and apparatus for insulating member

Also Published As

Publication number Publication date
GB2132012B (en) 1986-04-03
FR2538162A1 (en) 1984-06-22
CA1195373A (en) 1985-10-15
JPS59119656A (en) 1984-07-10
KR840007304A (en) 1984-12-06
IT8324091A0 (en) 1983-12-09
DE3345636A1 (en) 1984-06-20
IT1168981B (en) 1987-05-20
GB8332781D0 (en) 1984-01-18

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PCNP Patent ceased through non-payment of renewal fee