US2456399A

US2456399A - Cathode-ray apparatus

Info

Publication number: US2456399A
Application number: US624275A
Authority: US
Inventors: Richard B Gethmann
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-10-24
Filing date: 1945-10-24
Publication date: 1948-12-14
Anticipated expiration: 1965-12-14

Description

Dec. 14 1948. R GETHMANN 2,456,399

CATHODE-RAY APPARATUS Filed Oct. 24, 1945 v 2 Sheets-Sheet 1 Inventor:

Richar-d B.Get hmann His Attorney.

Dec.'14, 1948. Y R. B. GETHMANN I CATHODERAY APPARATUS 2 Sheets-Sheet 2 Filed 001;. 24, 1945 F/gaf F/QA.

umunumnmi Irfivehtofp bym' 2% H IS Att orn ey.

n a m h t e B d r a h Patented Dec. 14, 1948 or to General Electric of New York Company, a corporation Application October 24, 1945, Serial No. 524,275

1 Claims. (01. 250-161) This invention relates to electron discharge devices of the cathode ray type and particularly to apparatus for controlling the direction and de' flection of the electron beams of such devices.

Apparatus employing cathode ray tubes nor- I in electron gun and as a result the tubes donot produce their cathode ray beams in the same position and direction. It is therefore apparent that when one tube is substituted for another in the apparatus it becomes necessary toadjust the direction of the electron beam, and devices are commonly provided which make it possible to adjust the direction of the beam so that the spot on the flourescent screen of the cathode ray tube appears at the desired position. However, an accurate display of the signal impressed on a cathode ray tube may be prevented because of undesirable deflection components of the magnetic field associated with the magnetic deflection and focus coils. The distortion of the signal due to these components can be minimized by bringing about a coincidence of the axes of the deflecting and focus coils and the 'axis' of the electron beam. Accordingly it is an object of this invention to provide in an electron discharge apparatus of the cathode ray type an improved arrangement for mounting the deflecting .coils and the focusing coil in their positions about th envelope of a cathode ray tube.

It is another object of this invention to provide an electron discharge apparatus of the'cathode ray type including an improved arrangement for adjusting the position of the electron beam and for securing coincidence of the axes of the focusing and deflecting coils and of the beam.

The novel features which are believed to be characteristic of this invention are set forth with. particularity in the appended claims. The inven= tion itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is a side elevation view, partly in section, of a cathode ray apparatus embodying this invention; Fig. 2 is an enlarged view,partly in section, of a portion of the apparatus shown in Fig. 1; Fig. 3 is a sectional view on the line 33 of Fig. 2; and Fig. 4 is a sectional view on the line 4 --4 of Fig. 2.

Cil

Referring now toFig. I, a cathode ray tube I having a glass envelope comprising a bowlyportion 2 and a neck portion 3 is mounted on a suitable supporting base indicated by the line 4- on a split collar 5 secured to a supporting member 6 and with the'bowl portion held in a support 'Lby an insulating-collar 8 of rubber or other suitable resilient material. -A glass viewing screen 9 is secured inthe collar 8 so that it lies over the face of the cathode ray tube I. A suitable housing 10 is mounted on the support I and encloses the bowl 2; this housing is also attached to the support 6 through adjusting rods H. The cathode ray tube I is provided with suitable electrodes constituting an electron gun for projecting a cathode ray beam against a fluorescent screen covering the inner face of the bowl 2 adjacent the viewing screen 9. The details of construction-of the elementsof the electron gun are not essential to an understanding of this invention and have not been illustrated. However, a portion of the first anode of the electron gun is indicated at: I2 in Fig. 2. In order to bring the electron beam to focus on the luminescent screen of the tube; a focusing coil [3 is mounted about the neck 3 of the tube between the anode-I2, which is nearithe source of the electron beam, anda'set of deflecting coils indicated at M. The details of construction of the focusing coil I3 and of the deflecting coils M have'not been shown as these coilsmay be constructed in any suitable manner for providing magnetic fields for deflecting and for focusing the cathode ray beam. When the tube l is first placed in the supporting structure it is necessary to adjust the alignment of the cathode ray beam so that it is projected longitudinally of theneck 3 onto the screen in the desired direction. In order to adjust the direction of the electron beam there is provided an annular permanent magnet 15;

which may be rotated about the neck 3 of the tube. This magnet is rotatably mounted on a nonmagneticring l6 which is clamped about an extended nonmagnetic sleeve I1, attached to the collar-5. The magnet l5 has a single air gap indicated at I8 and is so magnetizedthatjit pro-'-,

duces a field extending diametrically across-the ring; thus, when the ringis rotated, the direction of the field is also rotatedl- It will be apparent that when the ring is rotated the direction of. the electron beam is rotated. By rotating the ring l5 the beam may be moved through any angle into the desired position. In order to adjust the angle of the beam with respect to the longitudinal axis of the tube, the strength offthe field produced by t been? is se e We e efie eit eas tron gun. The ring [6 which carries the gmag netic ring I5 is clamped about the supporting sleeve I! by a ring clamp 2|! provided with .a

clamping thumb screw 2!. i The supporting ring I6 is provided with a plurality of longitudinal slots 22 extending from the seat-of the magnet 1:5 through the right-hand edgeof the support thereby forming a plurality of separate finger portions which may be clamped tightly about the sleeve -11. *The supporting ring lG :may be elamped inany position on the sleeve 11 ito select the :position of the magnet 'li axially-ofthe tube andwith respect to the sleeve I8. The-direction of the beam may also be adjusted :by changing ilongitudinal position of the cylinder 5 with 351 851180? to the anode #2 to effecta simultaneous change in the positions =of the ring 15 and the core H withrespect tothe:anodedi. One or more openings 23 :may be provided in the sleeve 11 to afford a view -oi the position of the anode 42 of the tube when the ring and sleeve assembly is being 'adjusted with respect-toithe anode.

1f theaxis f the deflecting coil *3 and-of the beam projected'within the tube do not coincide, then waria'tlons in the focusing field result in distortion-of the signal as it'appears on the fluoresoent screen. similar situation prevails 'with respectto the deflecting coils I4, and it is desirable that the "central axis of the-deflecting coils andof thefocusing coilcoincidewiththe axis of theelect-ron beam. ;'In orderto secure this result the deflecting and focusing coils are secured to gather on 'a common :mounting'collar 24 to provide a unitary assembly arranged so that the central magneticaxes Of thecQiIs-are-in alignment and extend -in the direction iii-which the cathode raybeam'is to be projected. The coils are spaced fromthe-tube neck 3' and the collarrZl-is-attached to the'supportingstructure 6 by a -moun'ting which permits adjustment -of the collar 24 lateraiiykof the tube neck 3 at right angles to therequired axis of the beam. This mounting ineludes -a mountingpl-ate 25 whichis supported on the structure -B through the agenoyof an intermediate plate 16. "The plate 2-5 is clampedto the collin- 24 byturning set screwsfil shown in Fig. 3 until they press two split segments '28 tormed on the platen into engagement with the collar 24. clearly shown {in Fig. 3 the -mount-ing plate 25 *is slidabl-y mounted with respect to the inter mediate plate 28 it "being provided with four ho on a s otsfl o e eac co er cf the-p a e 2.5 ans wnieh nga t b sc ews {50 a t ched tothe plate 25 {or clamping-the plates 35 anddfi together. Adinstme tof th -pla efi w th resp c toth plat -fi-is aii d dby l se in the thum screws a d en tu n ng a thumb screw 3,!

mnunted inlugsfl and onthe iateszs and 26,.

slotsflbe' gp o ded init p a 25 and thumb sc ws, 5 on th s p o t ng struct re '5,- The plate 16 maybe slidably moved with respect to the supporting structure 6 by loosening the thumb screws 35 and then turning a thumb screw 36 mounted in

lugs

31 and 38 on the plate 26 and support 6, respectively. The slots 29 are at right angles to the slots 34 and thus the position of the collar 24 and of the coils carried thereby may be adjusted laterally in any direction at right angles to the longitudinal axis of the tube neck .3. This lateral adjustment makes 'it'possible to move the common central magnetic axis of the deflecting and focusing coils into any selected position; and

afiincethis axis extends in the direction in which the cathode ray beam is to be projected, the axes of :thecoils and-of th'e beam may be brought into coincidence.

The focusing'coil i3 is provided with a flanged boss or collar :39 which fits closely within the collar 24 and is secured thereto by a plurality of setkscrews 40. The focusing coil may be removed from the collar by loosening the set screws and sliding .the ibos-s -39 v=out of the collar :24. This construction.afiordseasyassembly ofzthe focusing and deflecting coil unit, and thefit of the collar 39 within the .collar 12A is such thatualignment .oi the axes of .ithe :focusing :and deflecting coils is assured .when thecollar :has been tightened rin place byithe set screws.

twhenia cathode ray tube is :to be installed iin the apparatus illustrated, -:the resilient collar .8, stogether with a metal frame-structure indicated .atidl and :the glass.=screen:,zis fittedloyersthe face of .the bowl I2 :of the tube. The tube :is then 1111- serted in :the apparatus so :that ail; :rests on the flower :portion :of the support 1. 5. As iswolearly shown Ei-n Rig. {4, sthe upper portion of it-he support 5 is :removable from the lower :portion Eby tloosenring .two set =scre.ws :42 which are :secured to 'the lower :portion and. :enter .=slots A3 ii-n :the upper removable portion. Two padsdidzof vrubber orrother suitable material are cemented *totthe upper :and ;lower portions :of :the support The-upper .porliiOH'rOf :the clampifi is then-.placedmver the neck of thestube, aslshown in Fig. 14. The iframe 1H ,is thenqsecured ,ein place -.on the sup-port -I :so that the face of :the tube is in sitszdesiredposition with the'longitudinal axis of the neck of the tube substantiallyparallehtlo the axisofvtlierdeflecting and focusing unit. The tube :is adjusted longitudinaliy of its support .bymeans -of rods d1 until the gun 1.2 is in its rrequiredcposition as determined bysighting through :one :of the openingslld. The clamping screws 112 i are then rtightened to hold the upperzportion of the clamping (member 5 in position about the tube meek and thereby maintain the'itube in its :desired position with respect to the magnetic ring 1-5. The [electrical onnections idiot-shown) :are then made so that "for purposes of testing :there may be applied-to the focusing -coil either an alternating current or a direct currentxwhich can lie-switched to be negative, aerobi -positive. The tube-is'then excited to generate-the electronbeam and if 'the axis'of the focus coil and the beam do-not coincide a pattern will appear on the screen when alternating current isa-pplied to the *focus coil or the position of the beam will be shifted upon switching the direct current of the focus coil. This pattern or shifting of the beam is produced by ;a change inintensity and'direction of the focusing field during eachalternating currentcycle or during eachchange in direction or intensity of the direct current. The pattern may be changed by rotatingithemagnetic ring 15 and by shifting it axially and also'by shifting the position of the focusing and deflecting coil unit. It will be round that by adjustment of these devices the pattern produced by the beam maybe reduced to a dot in the case "of' alternating testing current, and in the case of direct current the threedots corresponding to the three switching positions may be caused to coincide. This positionof coincidence occurs when thedirection of the beam is parallel to the axis of deflection of the focusing coil and coincidencetherflwith. Adjustment of the intensity of theifield produced by the magnetic ring 15 may, of course be made by axial movement of the core [9 during 'the adjustment. When the desired position for the magnetic ring on the tube I! has been determined, the thumb screw 2| is tightened to maintain lthat position. 1 In a similar manner the'f'ocusing and deflecting coil assembly is retained in its final desired position by tightening the thumb screws 30 and 35.

By constructing the supporting structure and the focusing and deflecting coils so that coincidence of the beam and coil axes may be secured, distortion of the signal portrayed on the screen is minimized. There is minimum astigmatism, and changes in the position of the spot resulting from random changes of focusing coil current are minimized. In cathode ray apparatus, utilizing the position of the luminescent spot on the screen as a measure of current, the coincidence of the coil and beam axes assures minimum error of the measurement.

While the invention has been illustrated in connection with a particular type of cathode ray tube, other applications and embodiments of the invention will readily be apparent to those skilled in the art. It is not, therefore, desired to limit the invention to the specific construction illustrated and described, and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray beam onto the screen, a magnetic focusing means arranged about the axis of the beam and having its central axis extending in the desired direction of the beam, means near the origin of the beam for adjusting the direction of the beam to make it parallel to the central axis of said focusing means, and means for moving said focusing means transversely of the direction of said beam for bringing the central axis of said focusing means into coincidence with the axis of said beam.

2. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray beam onto the screen, a magnetic focusing coil arranged about the axis of the beam and having its central axis extending in the desired direction of the beam, means providing a rotatable magnetic field about the beam near the origin thereof for adjusting the direction of the beam to make it parallel to the central axis of said focusing coil, and means for moving said coil transversely of the direction of said beam for bringing the central axis of said coil into coincidence with the axis of said beam.

3. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray beam onto the screen, a magnetic focusing means arranged about the axis of the beam and having its central axis extending inthe desired direction of'the beam, a beam (1e; fleeting means arranged about 'said envelopebe' tween saidfocusing means and said screen, said deflecting means being fixed with respect to said focusing means and having its central axis in alignment with 'the'central axis of said focusing means, means near the origin of the beam for adjusting the directionof the beam to make it parallel to the central axis of said focusing means, and means for moving said focusing and deflecting fmeans transversely of the direction of said beam for-bringing thecentral axis of said focusing and deflecting means into coincidence with the axis of said beam.

4 In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray beam onto the screen, a magnetic focusing coil arranged about the axis of the beam and having its central axis extending in the desired direction of the beam, a deflecting coil assembly arranged about the axis of the beam between said focusing coil and said screen and having its central axis in alignment with the central axis of said focusing coil, said focusing and deflecting coils being secured together against relative movement therebetween, means providing a rotatable magnetic field about the beam near the origin thereof for adjusting the direction of the beam to make it parallel to the central axis of said focusing coil, and means for moving said focusing and deflecting coils transversely of the direction of said beam for bringing the central axis of said coils into coincidence with the axis of said beam.

5. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and an electron gun for projecting a cathode ray onto the screen, a support for said envelope, a magnetic focusing coil and a magnetic deflecting coil secured together and having their central axes in alignment in the direction of the beam, means near the origin of the beam for adjusting the direction of the beam into parallelism with said central axes, and means for mounting said coils on said support and for affording movement of said coils together bodily laterally of the beam whereby the axis of said coils may be moved into coincidence with the axis of said beam.

6. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and means for projecting a cathode ray beam onto the screen, means for supporting the envelope, a focusing and deflection coil unit surrounding the envelope and attached to the supporting structure, said unit being positioned with its central axis parallel to the desired axis of the cathode ray beam, means near the origin of the beam for adjusting the direction of the beam into parallelism with said central axis, and means affording movement of said unit laterally while maintaining said central axis in the same direction for moving said central axis into coincidence with the beam.

7. In an electron discharge apparatus of the cathode ray type including an envelope having therein a screen and means for projecting a cathode ray beam onto the screen, a supporting structure, a unitary assembly comprising a focusing coil and a deflecting coil having a common central axis, means near the origin of the beam for adjusting the direction of the beam into parallelism with said central axis, said assembly being arranged to .fit lover the -nvelope :in ,spaced relatien thezeto land with said common,.axis extendvsaid uni-tmay be .brought into coincidence with the cathode ray beam. 3

' RICHARD .B. 'GE'THMANN.

REFERENCES mum The following orefgrences .are of .record in the file of this patent:

Number lflumbr UNITED STATES PATENTS Name Date Kuelmi Dec. 14, 1937 Goldsmith Decif31, 1940 De Tar Mar. 11,1941 Schuchmann et a]. Dec. 15, 1942 Packer Nov. '27, 1945 FOREIGN vZPA'IEE'NTS Country Date Great Britain Sept. 13, 193'!