US2206413A - Electron device - Google Patents

Description

' July 2, 1940. l. G. MALox-'Fv sLEcTRbn DEVICE Filed Nov. 9`, 1937 UNI I NV EN TOR.

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mgl/RY 6. MALOFF ATTORNEY.

Patented July 2, 1940 UNITED STATES ELECTRON DEVICE Ioury G. Malo, Norristown, Pa., assignorto Radio Corporation of America, a corporation of' Delaware Application November 9, 1937, Serial No. 173,667

Claims.

This invention relates to electron discharge devices, and, in particular, to electron beam tubes equipped with electrostatic deflection systems.

In cathode ray tubes where Ait is desired to 5 produce brilliant images, one ofr the general requirements is the use of highly accelerating voltages which may reach 20,000.V volts or more, the high voltage being necessary in order that the electrons impacting upon a luminescent screen shall produce enough luminosity to give the requisite illumination for observation purposes. Such tubes, for example, are used in electrical measurements, and in, particular, in television systems. Where the tube is used in electrical measuring systems because of high speed of indication, high illumination values are desirable in order that suitable photographs of the phenomena being studied may be conveniently made, While where such tubes arerused for television, 2Q it is desirable to have high illumination to alleviate eye strain, and at the same time, make the reproduced images on the luminescent screen easily visible tov large groups of people.

The requirements, therefore, upon the cathode ray focusing system commonly referred to as an electron gun, together with the delecting system, are rather severe from. the standpoint of insulation, because of the high voltages, while the use of the high voltages generally give rise 3o to distortions in the recorded phenomena due to the electrostatic elds set up between delecting plate systems and the support structures.

This is particularly true of the distortions which are set up between the mutually perpendicular electrostatic deecting system and the support members which serve to hold the deflecting electrode systems in `proper alignment. Consequently, one of the main obiects of this invention is to overcome the distortions arising between the deecting plate systems.

Another object of the invention is to provide a much firmer supporting method and means for the electron gun together with the deflecting system.

A still further object of my invention is to provide an improved method of insulating the deecting electrodes and the electron gun from the support members.

Other and ancillary objects of the invention will be apparent upon the reading of the detailed description taken together with the appended claims. Y

In accordance with the invention with respect to the elimination of distortion arising between the deflecting plate system and the support mem- (Cl. Z50-458) bers, I position intermediate the mutually perpendicular electrode. systems a. pair of electrostatic shields which are electrically bonded to the metallic support rods which support the deflecting electrodes as Well as the electron gun. 5 The electrostatic shields thus provided eliminate any asymmetrical electrostatic elds which might otherwise be set up, and consequently, prevent the beam of electrons from being affected by spurious electrostatic fields which would 10 otherwise be present.

In carrying out my method and means for supporting the unitary assembly of the gun and deecting system, I. make 'use of a metal place into which are screwed four relatively large dil5 ameter metal rods in a symmetrical array. Attached to the support rods are lateral support members for carrying the deilectng plates, while ring. shaped support members are supplied for the electrode gun structure. For purposes of h20 insulation, insulating members are fastened between. the deecting electrode and the lateral support members, while ring insulators are supplied between the ring support members and the electrodes ofr the electron gun. 25

Turning now to the drawing, in which Fig. l shows schematically a cathode ray tube embodying my invention,

Fig. 2 shows the cross-section taken at the line 2-2 of Fig. l; and 30 Fig. 3 shows the details of supporting deflecting electrodes in accordance with my invention.

I will describe my invention in detail.

Referring now to Fig. -1, an envelope I which may be of glass, but preferably for large sized 35 tubes is made of metal, supports .at the one end a glass walll 4 Ii, upon which is supported a layer of luminescent material 43. The edges of the envelope, which are iianged, are lapped ground as are the edges of the end wall 4i in contact therewith, so that by the use of suitable sealing compounds, an air-tight joint is provided.

It will be understood that this form of structure is used preferably where the size of the tube is so large as not to use a single envelope member 45 because oi the gigantic pressure whichrmust be supported by the end wall. Where small sized tubes are provided, the endr wall 4l and the envelope l maybe suitably made from a single glass blank, as is well known in the art. At the 50 opposite end of the envelope, a metal plate 35 lapped. ground so as to form a lapped joint with the flanged end of the envelope I, has supported therefrom four metal rods 5 5. These metal support rods support lateral support members 55 1 and I1, from which in turn, are insulatedly supported the defiecting plates 3-3 and 2l, the insulator elements I3 being interposed between the plates and the lateral support members.

The method of support is shown in more detail in Fig. 3 in which the metal rods 5 are shown supporting the lateral support members 1, which have suitable holes drilled in their upper faces through which the rods 5 may pass and which are held in position by set screws II. The set screws 9 extend through the lateral support member 1 and engage with suitably tapped holes in the insulating member I3. vThe deflecting plate 3 is supported at an angle with the axis of the tube by counter-sunk set screws extending through the insulating member I3 and engaging with shallow threaded holes in the deiiecting plate 3.

Alternatively, the plate 3 may be fastened to the insulating member which may be of ceramic material by a suitable cement. Connection to the deiiecting plates is by way of the leads 45, which are spot-welded or soldered to the deiiecting plates and which run alongside of the support rods 5, but mounted clear thereof through the use of stand-off insulators. Below the deilecting plates 3 are the electrostatic shield members I5, each shield being electrically bonded to two of the support rods 5, extending beyond stand-off insulators.

- sulator.

the lower edge of the plates 3-3 and in back thereof. Below these, the other set of deiiecting plates 2l, set at right angles to the first set of deflecting plates, as Well as the shields I5, are supported in essentially the same manner as the deflecting plates 3-3 by means of the lateral member l1, which member is locked in place by the set screws I9. The set screws 23 serve to hold an insulator from which the plate 2l is mounted, and a potential connection is afforded by the lead 49, which also runs alongside of the support rods, but held spaced therefrom by Below the defiecting plates, the second anode 29 of the electron gun is held in position by a ringed insulator tightly gripping the second anode 29. The ring insulator in turn is supported from a metallic ring support member 39, which is held in position by the set screws 21 inserted inthe ring member 39 and engaging with the rods 5. The second anode is electrically bonded to the envelope I by means of lead 5I in the applications where a metal tube is used. Where, however, a glass envelope is used, then the second anode may be electrically bonded to the supportrods 5. The first anode 3I is similarly supported from the support rods 5 by a ring member 39 engaging a ring insulator, which ring insulator has a drive t over the cylindrical rst anode. Suitable connection to the'rst anode is provided by way of lead 53 passing through the glass press 33. The control electrode 55 is supported from the first anode 3l by means of an internal annular in- This insulator has a drive fit with respect to the inner surface of the first anode 3| and a drive t with respect to the external surface of the control electrode 55. Internally of the control electrode 55, a cathode which may be of indirectly heated type, may be suitably supported and positioned by an annular ceramic insulator. Suitable leads are provided to both the control electrode and the cathode, which leads pass through the glass seal 33, which seal lis made air-tight with respect to the metal plate 35. A y

Fig. 2 shows in cross-section in somewhat more detail the method of supporting the anodes by the use of the ring insulators and support members. In this figure, the second anode 29 is shown in section around which is placed the ring insulator 31, which in turn has the metal ring 39 in contact with it. The insulator, which may be of the ceramic type, is held in position by set screws 25, while the assembly of the metallic ring 39, the insulator 31, and the second anode 29, are conveniently supported from the rods 5 and locked in position by the set screws 21. Thus a very rigid, easily assembled, electron gun and deflecting plate system is provided with excellent provision against displacement by mechanicall shock or impact.

At the same time'the electrical shields I5 prevent fringing from the deflecting plates to the support rods, in the region where the beam wouldgbe adversely affected and would, accordingly, produce distortion if it were not for these shields. It should be understood, that Where high voltages on the order of 20,000 volts vare provided, together with a metalcasing such as is shown in the drawing, the'metal casing is maintained at ground potentialI so that liability-to shock is guarded against, and accordingly, the support rods are at the same potential as the second anode, while the other electrodes in the system are generally at a lower potential. Since the electrostatic` deflecting plates, whiph are generally supplied with saw-tooth deflection voltages, are generally of negative voltage with respect to thevoltage of the casing I, the difference in potential between the deflecting plates and the support rods would normally produce a. distorting electrostatic field through which the beam would necessarily pass. However, by providing a large conducting surface maintained at the same potential as the support rods in .back of the deflecting plates, any electrostatic fields set up are outside of the region through which the cathode ray beam passes, and hence, no deleterious effects are encountered.

It. will, therefore, be understood that this method of confining spurious electrostatic fields to the back of the deecting plates, enables improved results to be obtained.

Although the invention has been shown. as applied to well known electron discharge devices, it is to be understood that the electron discharge devicesare merely illustrative of any organization since the invention may be applied to numerous other embodiments without departing from the spirit and scope of the invention.

Having described my invention, what I claim is:

l. A cathode ray tube comprising a metallic envelope flared at one end,` a rglass end` wall sealed to the flared end, a luminescent screen supported from the glassA wall, a metal base support plate fastened to the envelope, a plurality of metal support rods supported from the plate, and means to support in register with each other an electron gun and two pairs of deecting elec:- trodes perpendicular to each other, said vsupport means being afiixed to said metal rods.

2. A cathode ray tube comprising a metallic envelope flared at one end, a glass end wall sealed to the flared end, a luminescent screen supported from the glass wall, a support plate fastened to the envelope, a plurality of metal support rods supported from the plate, means to support in register with each other an electron gunj and two pairs of deflecting electrodesperpendicular to each other, said support means vbeing aflixed to said metal rods, and electrostatic shieldsl supported from the support rods and intermediate the two pairs of deflecting electrodes.

3. A cathode ray tube comprising a metallic envelope ared at one end, a glass end wall sealed to the ared end, a luminescent screen supported from the glass Wall, a support plate fastened to the envelope, a plurality of metal support rods supported from the plate, means to support in register with each other an electron gun and two pairs of deflecting electrodes perpendicular to each other, said support means being axed to said metal rods, and a pair of rectangular plates intermediate the pairs ofdeecting electrodes and electrically bonded to and supported from the support rods.

4. A cathode ray tube comprising a metallic envelope flared at one end, a glass end wall sealed to the flared end, a luminescent screen supported from the glass Wall, a support plate fastened -to the envelope, a plurality of metal support rods supported from the plate, means to support in register with each other an electron gun and two pairs of deecting electrodes perpendicular to each other, said support means being affixed to said metal'rods, and a pair of parallel plates electrically bonded to and supported from the support rods intermediate the pairs of deflecting electrodes and extending in back of one of the deflecting electrodes.

5. In a cathode ray tube, the combination of an electron gun, a pair of deecting plates in register with the electron gun, a second pair of delecting plates in register with the electron gun and more remotelv positioned than the first pair of defiecting plates, a pair of electrostatic shields positioned in the region intermediate the first and second pairs of deflecting plates, a planar metal support plate, a plurality of metallic rods constituting common means for supporting the electron gun, the electrostatic shields, and the two pairs of deflecting plates, said metallic rods being afxed perpendicularly to said support plate, and connections from said shields to said metallic rods.

IOURY G. MALOFF.

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