US2119070A - High voltage discharge tube - Google Patents

High voltage discharge tube Download PDF

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Publication number
US2119070A
US2119070A US759299A US75929934A US2119070A US 2119070 A US2119070 A US 2119070A US 759299 A US759299 A US 759299A US 75929934 A US75929934 A US 75929934A US 2119070 A US2119070 A US 2119070A
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US
United States
Prior art keywords
tube
insulating
portions
sleeve
cylinder
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.)
Expired - Lifetime
Application number
US759299A
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English (en)
Inventor
Bouwers Albert
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
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 Philips Gloeilampenfabrieken NV filed Critical Philips Gloeilampenfabrieken NV
Application granted granted Critical
Publication of US2119070A publication Critical patent/US2119070A/en
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Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J5/00—Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
    • H01J5/02—Vessels; Containers; Shields associated therewith; Vacuum locks
    • H01J5/06—Vessels or containers specially adapted for operation at high tension, e.g. by improved potential distribution over surface of vessel

Definitions

  • This invention relates to high voltage discharge tubes and more particularly to discharge tubes having equipotential wall portions.
  • the envelope comprises equipotential portions, for example a metal portion or a non-conductive portion coated with conductive material, to which are edgewise joined portions of insulation material, for instance of glass.
  • the insulating portions adjoining the equipotential portion are as a rule so shaped as to form a substantially colinear continuation of the equipotential portion, for instance, when the equi- 16 potential is a cylinder the adjoining insulating portions are also cylindrical, having substantially the same diameter as the equipotential portion. Even if there is in some cases a diierence in the diameter of these adjoining portions, this differ- 20 ence is slight.
  • the insulating portions in the vicinity of the equipotential portion assume a high electric charge and the voltage drop per unit length of insulation, i. e., poten- 25 tial gradient or concentration of electric lines of force, is much greater in the vicinity of the equipotential portion (and especially at the junction of the insulating and equipotential portions, where it has its maximum), than at the more re- 80 mote parts of the insulating portions.
  • I so shape the insulating portions that their intersection with any plane passing through the axis of the tube results in a curve, along which the potential 55 gradient is substantially constant.
  • the insulating portions form bulged-out vitreous members which are sealed at one end to 10 the metal sleeve and at the other end carry the electrodes, and which together with the sleeve form the closed container of the tube.
  • the insulating portions are joined to the central metal sleeve by sealing them with the edge of an inwardly-curved end portion to the outer surface of the metal sleeve at a distance back from the edge of the sleeve.
  • Figure 1 is a partly sectionized view of a portion of a discharge tube of prior art construction, showing the electric iield distribution in the vicinity of the junction between the equipotential and insulating portions.
  • Fig. 1a is an enlarged view of a portion of Fig. 1.
  • Fig. 2 is a graph showing comparative curves for the voltage distribution along the length of insulating portions made according to the prior art and according to the invention.
  • Fig. 3 is a partly sectionized view of an X-ray tube having insulating portions shaped in accordance with the invention.
  • the wall of the tube for instance an X-ray tube, comprises an equipotential metal portion, for instance a chrome iron sleeve I, to the edges of which are sealed two insulating portions 2 of vitreous material, for instance of glass., (only one of which is shown) and which have the same diameter as the sleeve I, thus forming a colinear continuation thereof.
  • the tube is provided in the usual way with electrodes, the figure showing only the anode 4 which is carried by a re-entrant part 3 of the insulating 45 portion 2, to which it is fused.
  • the equipotential surfaces may be considered as surfaces of revolution of which the lines 5 are the generatrices. Between the sleeve l and the electrode 4 these surfaces have the shape of concentric cylinders, whereas beyond the sleeve I, they bend around the edge of the sleeve I and increase their mutual distance in a fanlike manner.
  • the distances between adjacent equipotential surfaces, as measured along the insulating portion 2, and indicated as ai, a2, as, etc. is a minimum close to the edge of portion l and increases with increasing distances from this edge.
  • the potential gradient along the insulating portion 2 is a maximum at the edge of sleeve l and greatly decreases with increasing distances therefrom.
  • the abscissa axis represents the length of the insulating portion as measured from the edge of sleeve i, and the ordinates represent the potential difference existing between the sleeve l and individual points of the insulating portions.
  • the curve a represents the voltage distribution along the insulating portion 2 of Fig. l, for a total voltage difference of the value E1 applied between the sleeve l and the electrode 4.
  • the slope of the Curve represents at any point the potential gradient at this point, and it is again clearly apparent that the potential gradient is very high at the edge of sleeve l (corresponding to the point O), where it assumes its maximum value measurable by the tangent drawn to the curve at this point, e. g. 10 kv. per cm., which may be considered as the maximum permissible value for most kinds of glass surfaces under normal conditions.
  • the potential gradient decreases, and over a considerable portion of the insulation is practically zero.
  • the potential gradient would be the same at any point along the insulating portion and would be considerably smaller than that existing in the vicinity of sleeve l in the construction of Figure l.
  • the electrical stress to which the insulating portion is subjected would be the same throughout its entire length and its insulating capacity would be fully utilized.
  • a discharge tube having insulation portions of the shape shown in Fig. 3 has a substantially uniform potential gradient along a considerable portion of the insulating portions and the maximum value oi the gradient will be considerably smaller than is the case of the tube of Fig. 1.
  • the insulating portions-not being subjected to a much higher potential gradient in the vicinity of the equipotential section than at the other portions can be made much shorter for the same effective operating voltage, the respective lengths, as appears from Fig. 2, being Z1 (for Fig. l) and l2 (for Fig. 3).
  • a tube made according to Fig. 3 and having the same insulating length as the tube made according to Fig. 1 can stand a much higher voltage.
  • the voltage distribution of a tube according to Fig. 3 is represented by the curve c, which has the same initial potential gradient as curve a, i. e., the same tangent d, and will permit the use of a voltage E2 which is much higher than E1.
  • the tube schematically shown in Fig. 3 is assumed to be an X-ray tube for very high operating voltages, for instance, a deep therapy tube.
  • the envelope comprises a central metal cylinder l and glass members 8 and 9.
  • the glass members are sealed with their inner edges to the two ends of cylinder 'l and bulge out in a mushroom-like form.
  • the inner end surfaces of the glass portions 8 and 9 are inwardly curved and are sealed to the cylinder l, preferably by means oi an annular flange il, extending perpendicularly from the cylinder' l at a point somewhat back from the edge of the cylinder.
  • the glass portion approaches the flange il substantially a plane perpendicular to the axis of the tube.
  • This arrangement provides for an easier method of sealing, and also assists in obtaining the desired field distribution.
  • the maximum diameter P of the glass members il is greatly in excess of the diameter q of the cylinder l.
  • the inner edges of the cylinder 'i are preferably surrounded with a heavy .layer of glass, shown in dotted lines at i5 and iii.
  • the metal members 8 and 9 are provided with re-entrant portions 25J and 2i which carry the anode and cathode il respectively.
  • the cylinder 'i is provided in known manner with a ray-emitting window I2.
  • the tube receives its operating voltage from the secondary winding of a high-tension transformer 25 whose primary winding is connected to a lsuitable A. C. supply, and a battery serves to heat the cathode of the tube.
  • Tubes made according to the invention can be of much smaller overall lengths than tubes according to the prior art if using the same operating voltage; for instance, for an operating Voltage of 200 kv. a tube made according to Fig. l will have an overall length of 20 inches, whereas a tube according to the 1nvention will have a length of 12 inches.
  • the invention may be similarly applied to other high Voltage discharge tubes, for instance, rectier tubes, and instead of providing the equipotential portion as a metal member sealed to the insulating member, the equipotential member may be formed of glass provided with a conducting layer or otherwise.
  • an envelope comprising a central metal cylinder having an annular metal flange spaced back from each edge thereof, two
  • each of said insulating portions carrying at one end the electrodes of the tube, the other end being inwardly curved and edgewise sealed to said annular flange.
  • a high-voltage electric discharge tube comprising electrodes, and an envelope having a central metal cylinder surrounding a portion of said electrodes and provided with an annular metal flange spaced back from each edge of the cylinder, and two insulating end portions, each of said portions having a width in a plane perpendicular to the axis of said cylinder at the edge .thereof substantially greater than the diameter of the cylinder, said end portions carrying said electrodes and insulating same from said cylinder, the surface of one end of each of said insulating portions being inwardly curved and edgewise sealed to one of said flanges.
  • an envelope comprising a central metal cylinder having an annular metal flange spaced back from each edge thereof, and two insulating portions whose width perpendicular to the axis of the cylinder is greater than the diameter of the cylinder, each of said insulating portions carrying at one end the electrodes of the tube, the other end being inwardly curved and edgewise sealed to said annular flange.

Landscapes

  • Vessels And Coating Films For Discharge Lamps (AREA)
  • X-Ray Techniques (AREA)
US759299A 1934-01-26 1934-12-26 High voltage discharge tube Expired - Lifetime US2119070A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEM126307D DE633298C (de) 1934-01-26 1934-01-26 Hochspannungsentladungsroehre mit aequipotentialem Wandteil

Publications (1)

Publication Number Publication Date
US2119070A true US2119070A (en) 1938-05-31

Family

ID=6505345

Family Applications (1)

Application Number Title Priority Date Filing Date
US759299A Expired - Lifetime US2119070A (en) 1934-01-26 1934-12-26 High voltage discharge tube

Country Status (5)

Country Link
US (1) US2119070A (enrdf_load_stackoverflow)
DE (1) DE633298C (enrdf_load_stackoverflow)
FR (1) FR783324A (enrdf_load_stackoverflow)
GB (1) GB434319A (enrdf_load_stackoverflow)
NL (1) NL41746C (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2454049A (en) * 1944-02-04 1948-11-16 Gen Electric Electric capacitor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE972355C (de) * 1952-02-20 1959-07-09 Licentia Gmbh Strahlenaustrittsfenster aus Glasfolie mit einer Dicke kleiner als 0, 1 mm, vorzugsweise Hartglasfolie, fuer Entladungsgefaesse, insbesondere Roentgenroehren, und Verfahren zu seiner Herstellung

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2454049A (en) * 1944-02-04 1948-11-16 Gen Electric Electric capacitor

Also Published As

Publication number Publication date
NL41746C (enrdf_load_stackoverflow) 1937-10-15
GB434319A (en) 1935-08-29
DE633298C (de) 1936-07-24
FR783324A (fr) 1935-07-11

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