Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/06—Screens for shielding; Masks interposed in the electron stream
  • H01J29/07—Shadow masks for colour television tubes
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
  • H01J29/06—Screens for shielding; Masks interposed in the electron stream
  • H01J29/07—Shadow masks for colour television tubes
  • H01J29/073—Mounting arrangements associated with shadow masks
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
  • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J2229/00—Details of cathode ray tubes or electron beam tubes
  • H01J2229/07—Shadow masks
  • H01J2229/0727—Aperture plate
  • H01J2229/0738—Mitigating undesirable mechanical effects
  • H01J2229/0744—Vibrations

Definitions

• the present invention relates to a masking device for a color cathode ray tube.
• the invention finds its application in any type of tube comprising a mask for selecting colors and is as well suited to tubes whose mask is kept in tension by the frame on which it is secured, as to the mask formed by pressing and then fixed by welding to the support frame.
• Conventional cathode ray tubes have a color selection mask located at a precise distance from the inside of the glass front face of the tube, the front face on which are deposited arrays of red, green and blue phosphors to form a screen , said front face being practically perpendicular to the longitudinal axis Z of the tube,
• the mask consists of a metal sheet pierced in its central part with a plurality of holes or slots.
• An electron gun placed inside the tube, in its rear part, generates three electron beams in the direction of the front face.
• An electromagnetic deflection device generally placed outside the tube and close to the electron gun, has the function of deflecting the electron beams in order to make them scan the surface of the panel on which the phosphor networks are arranged. Under the influence of three electron beams each corresponding to a specific primary color, the phosphor networks reproduce colored images on the screen, the mask allowing each determined beam to illuminate only the phosphor of the corresponding color.
• the color selection mask must be placed and maintained during the operation of the tube in a precise position inside the tube.
• the mask holding functions are performed by means of a generally very rigid rectangular metal frame on which the mask is conventionally welded.
• the frame / mask assembly is mounted inside the front face of the tube by means of suspension most often welded to the frame and cooperating with pins inserted in the glass constituting the front face of the tube.
• the tubes whose front face is more and more flat correspond to the current trend, with an evolution towards completely flat front faces.
• a plane mask held in tension in at least one direction.
• the mask can be formed by pressing, its surface pierced with openings then being slightly curved to follow the internal curvature of the glass front face of the tube.
• the peripheral skirt of the mask formed so as to be perpendicular to the surface pierced with openings, is conventionally welded to the edge of the support frame, which generally has a substantially L-shaped section.
• the color selection mask being constituted by a metal sheet of very small thickness, its tensioning can generate parasitic phenomena of vibration of said mask during the operation of the tube. Under the influence of shock or external mechanical vibrations, for example acoustic vibrations due to the loudspeakers of the television set in which the tube is inserted, the mask can enter into vibration according to its natural frequency of resonance.
• the vibrations of the mask have the effect of modifying the landing zone of the electron beams on the screen of the tube, the points of impact of each beam then being offset with respect to the associated phosphor network, thus creating a discoloration of the image reproduced on the screen.
• US Pat. No. 4,827,179 proposes adding on one face of the mask means for damping the vibration of the mask. These means are in known manner, arranged on the peripheral part of the mask not pierced with openings.
• the depreciation devices implemented in this patent have a complicated structure, which is difficult to implement. Indeed, these devices must be installed on the surface of the mask once it is stretched over the frame; in fact the fragility of the thin metal sheet pierced with openings constituting the mask does not allow additional components to be installed there before its installation on the frame.
• the fragility of the mask can pose a problem in welding damping means to its surface: any final modification of the surface of the mask can cause rejection of the complete masking device. Furthermore, during the welding of the damping elements on the edges of the mask, weld projections can occur and seal holes on the central surface of the mask, which also causes the rejection of the entire masking device. It is one of the objects of said invention to provide a cathode ray tube comprising a masking device for a color cathode ray tube comprising simple damping means, inexpensive, and easy to install without causing deterioration of the surface. of the mask and as well adaptable to a tensed mask structure as to a mask structure formed by pressing.
• the cathode ray tube comprises a mask for selecting colors in the form of a metal sheet, suitable for being fixed on a support frame of substantially rectangular shape and comprising a pair of short parallel sides and a pair long parallel sides, the frame / mask assembly being arranged inside the glass front face of the tube, the frame being characterized in that at least two of its opposite sides have at least one cavity inside from which at least one metallic mass is likely to move.
• Figure 2 describes a frame / mask assembly stretched according to the state of the art without vibration damper
• Figure 3 is a perspective view of an embodiment of a vibration damping device according to the state of technique.
• Figure 4 shows from the front a mask support frame according to the invention
• a cathode ray tube 1 comprises a substantially flat slab 2 and a peripheral skirt 3.
• the slab is connected to the rear part of the tube, in the form of a funnel 4 by means of a sintered glass seal.
• the end portion 5 of the tube surrounds the electron gun 6, the beams of which illuminate the screen of luminescent phosphors 13 through the color selection mask 8, which is here flat, for example stretched between the long sides 9 of the frame 19.
• Metal supports of the frame / mask assembly hold this assembly inside the tube, said supports. may include a part 10 welded to the frame and a part forming a spring 11, provided with an opening for cooperating with a pin 12 included in the glass skirt 3.
• the frame 19 comprises a pair of long sides 9 and a pair of short sides 7, said long and short sides having for example an L-shaped section, the short sides 7 having a face 71 substantially parallel to the mask.
• the mask 8 itself of substantially rectangular shape, is tensioned, then maintained in this state for example by welding on the end 20 of said long sides of the frame.
• the mask 8 consists of a metal sheet, for example made of steel or Invar, of very small thickness, of the order of 100 ⁇ m.
• the mask has a central zone 30 pierced with openings generally arranged in columns and a peripheral zone 28 surrounding the central zone 30, peripheral zone comprising for example horizontal 31 and vertical edges 32 not participating in the selection of colors.
• Cathode ray tube structures using color selection masks kept in tension on the support frame have to face the vibration problem of this mask, according to their own modes, when said mask is excited by external vibrations , for example mechanical shock on the tube or sound vibrations coming from loudspeakers arranged near said tube.
• vibrations being manifested by movements of the mask in a direction perpendicular to its surface, the distance between the openings of the mask and the screen varies locally depending on the amplitude of the vibration of said mask.
• the purity of the colors reproduced on the screen is then no longer guaranteed, the landing points of the beams on the screen being shifted as a function of the amplitude of the vibration and of the area of the mask vibrated; for example, the vibrations of the edges of the perforated part 30 of the mask will be more visible on the screen because this zone is crossed by the electronic beams at angles of incidence of significant value.
• the vibrations of the mask are only very slowly absorbed, the energy communicated to the mask having few means of dissipation, which increases the visibility of the phenomenon on the screen when the tube is in operation.
• the same phenomenon can occur with masks formed by pressing and then welded to the frame, especially for tubes having a substantially planar front face.
• the flatness of the surface of the mask makes this surface not very rigid mechanically and on the contrary sensitive to the vibrations of the environment.
• the hooks are installed on the mask which is itself mechanically fragile with the risk of damaging it.
• the invention provides a simple, economical structure, and easy to implement to dampen the vibrations of a mask generated by the mask. environment of the tube by installing an anti-vibration device on the frame to which the mask is attached
• Figure 4 is a top view of a first embodiment of a frame 90 shadow mask support according to the invention.
• the frame 90 is of substantially rectangular shape and has a pair of short sides 100 and a pair of long sides 101.
• the short sides are of substantially L-shaped section and has a first flange 100 ′ substantially parallel to the surface of the mask and a second flange 100 "perpendicular to the first and extending towards the screen of the tube.
• a cavity 120 substantially in the middle of said short sides, produced for example by stamping the flange 100 'parallel to the surface of the mask.
• This cavity of parallelepiped shape extends along the short side so as to be able to receive a mass 115; the cavity is closed by a cover 1 12 which, as illustrated in FIG. 6, can only partially cover the cavity 120, the opening 111 of the cover 112 being of smaller size than the mass 115 to maintain the latter in the cavity 120
• Figure 5 shows in section along a plane AA 'perpendicular to the flange 100' and passing through the middle of the short sides 100, the mass 115 held inside the cavity 120 by the cover 112.
• the cavity extends towards the inside of the volume created by said assembly. In this way the surface of the frame / mask assembly opposite the mask remains substantially flat.
• the volume of the cavity once closed by the cover 112 remains slightly greater than the volume of the mass 115 that it contains so that this mass is not immobilized.
• the mechanical clearance of the mass 115 in the cavity in the direction of the longitudinal axis Z of the tube must be at least of the order of 0.5 mm and preferably around 1 mm, for the tubes of intermediate dimension, that is to say the screen diagonal of about 70cm.
• the weight of the mass 115 must be adjusted according to parameters such as the format of the image screen (4/3 or 19/9), the size of the screen, the fact of having a frame / mask system in which the mask is in tension or not. It has been demonstrated that the mass 115, in order to provide maximum efficiency, should preferably weigh a weight proportional to the weight of the frame / mask assembly.
• the cavity 1 10 containing the mass 115 is produced by attaching a housing 116 containing said mass and securing said housing by welding to the frame.
• the housing 1 16 may for example comprise two opposite lips 117 folded outwards allowing the weld on the flange 100 ′ and two lips 1 18 folded inwards so as to maintain the mass 115 inside the housing before the welding phase on the frame.

Landscapes

• Electrodes For Cathode-Ray Tubes (AREA)
• Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=33446428

Family Applications (1)

Country Status (8)

Family Cites Families (2)

• 2003
  • 2003-05-09 IT IT000935A patent/ITMI20030935A1/it unknown
• 2004
  • 2004-04-29 JP JP2006530433A patent/JP2006528832A/ja not_active Withdrawn
  • 2004-04-29 CN CNA2004800121509A patent/CN1784761A/zh active Pending
  • 2004-04-29 KR KR1020057020857A patent/KR20060008969A/ko not_active Withdrawn
  • 2004-04-29 MX MXPA05011930A patent/MXPA05011930A/es not_active Application Discontinuation
  • 2004-04-29 WO PCT/FR2004/050177 patent/WO2004102608A1/fr not_active Ceased
  • 2004-04-29 US US10/554,455 patent/US20070210690A1/en not_active Abandoned
  • 2004-04-29 EP EP04742861A patent/EP1623444A1/de not_active Withdrawn

Non-Patent Citations (1)

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