US3176200A

US3176200A - Beam centering apparatus for cathode ray tubes

Info

Publication number: US3176200A
Application number: US221107A
Authority: US
Inventors: Fred P Manetti; Orie E Pine
Original assignee: AMERICAN PLASTICRAFT Co
Current assignee: AMERICAN PLASTICRAFT Co
Priority date: 1962-09-04
Filing date: 1962-09-04
Publication date: 1965-03-30
Anticipated expiration: 1982-03-30

Description

March 30, 1965 F. P. MANETTI ETAL 3,176,200

BEAM CENTERING APPARATUS FOR CATHODE RAY TUBES Filed Sept. 4, 1962 INVENTORS FQH/ PMA/l'sih IZ E. 73/";

United States Patent C 3,176,200 BEAM CENTERING APPARATUS FQR CATHODE RAY TUBES Fred P. Manetti, River Forest, and Orie E. Pine, Lombard,

Ill., assignors to American Plasticraft Company, Chicago, Ill., a corporation of Illinois Filed Sept. 4, 1962, Ser. No. 221,107 Claims. (Cl. 311-200) The present invention generally relates to a magnetic device attachable to the neck of a cathode ray tube for adjusting the position of cathode ray impingement on the viewing screen of the tube, and it more particularly relates to a new and improved device particularly suited for centering the raster on the viewing screen of a television receiver picture tube.

In order to enable manual adjustment of the position of the raster on the face of a television picture tube, it is known in the prior art to employ a pair of axially spaced circular ring magnets each arranged concentrically with the principal axis of the tube. The magnets are very closely spaced and are provided with radially extending tabs for adjustably rotating the ring magnets about the neck of the tube relative both to the tube and to one another. These magnets preferably have a magnetic axis parallel to a diameter of the ring whereby adjustment of the strength and direction of the composite magnetic field of the two magnets may be accomplished by the rotation of the magnetic rings. The resultant field provides the necessary force on the electrons to cause the desired deflection of the beam.

This type of magnetic centering device has now been in use for many years and the rings are commonly formed from relatively thin sheet metal stock. It has been found that unless extreme precautions are taken during the manufacturing process these thin flat rings become warped to an extent that they are rendered useless. Accordingly, it would be desirable to provide a centering device in which the thin, flat magnets are eliminated,

thereby to reduce the number of defective parts which must be scrapped and thereby to reduce the manufacturing cost of each completed unit.

In the past, the suppport on which the magnetic rings were rotatably mounted was a molded holding member formed of plastic and to which the rings were attached by separate spring clips or the like. The entire assembly was, in turn, secured at a fixed axial position along the neck of the picture tube by means of a separate metal clamping band which surrounded a longitudinally slit sleeve portion of the holding member. In order to reduce the cost of the over-all picture centering assembly, it would be desirable to mold a single plastic member which rotatably supports the magnetic rings and which includes as an integral part thereof, the clamping means for securing it at a fixed position along the neck of the associated picture tube. Such a molded memher would substantially decrease the time required to assemble the completed device, would reduce the number of different parts which would have to be manufactured and stored, and it could thus be manufactured at a lower cost than its multiple-piece prior art type counterpart.

Therefore, a principal object of the present invention is to provide a new and improved device for controllably deflecting the cathode ray beam in a cathode ray tube.

Another object of the present invention is to provide a new and improved centering device for a television picture tube.

Still another object of the present invention is to provide a new and improved moldable member for rotatably supporting a pair of ring magnets and including an "ice integral portion for clamping the device at a fixed position on the neck of the television picture tube.

A further object of the present invention is to provide a new and improved magnetic ring construction for adjusting the position of impingement of a cathode ray beam on the face of a cathode ray tube.

A still further object of the present invention is to provide a new and improved television picture centering device which is durable in construction, effective in operation, and inexpensive to manufacture.

Briefly, the above and further objects are realized in accordance with the present invention by providing a centering device including a moldable support member having an integral portion for rotatably receiving a pair of magnetic rings, and further including an integral portion for clamping the assembly to the neck of a cathode ray picture tube. In accordance with another feature of the present invention the magnetic rings are formed of lengths of ferromagnetic wire formed into a nearly complete circle and hvaing integnal off-turned adjustment tabs.

Further objects and advantages and a better understanding of the present invention may be had by reference to the following detailed description taken in connection with the accompanying drawing in which:

FIG. 1 is a fragmentary elevational view illustrating a centering device embodying the present invention attached to the neck of a cathode ray tube;

FIG. 2 is a view looking at the rearward end of a centering device embodying the present invention;

FIG. 3 is a view looking at the forward end of a centering device embodying the present invention;

FIG. 4 is a sectional view of the device of FIG. 2 taken along the line 4-4 thereof with the cathode ray tube removed for purposes of clarity; and

FIG. 5 is a longitudinal sectional view of an alternative embodiment of the present invention.

Referring now to the drawings and particularly to FIG. 1 thereof, there is shown a portion of a cathode ray tube 10 used as a television picture tube. The tube 10' has a cylindrical neck portion 11 terminating at its forward end in a flared out portion 12 which extends to the face of the tube on which the viewing screen 13' is located. An electron beam generated by suitable means such as a cathode ray gun (not shown) is directed from the right-hand end of the neck 11 to the viewing screen and thereby passes through a portion of the neck about which inductance coils forming a sweep yoke assembly 14 are disposed. The sweep yoke assembly 14 may be conventional and in cooperation with the horizontal and vertical sweep circuits of the associated system causes the electron beam to sequentially sweep across the face of the screen 13 to provide the usual raster. Consequently, if the electron beam is amplitude or intensity modulated in accordance with the received video signal, the televised picture is reproduced on the vewing screen of the tube 10.

Directly to the rear of the sweep yoke assembly 14 and mounted on the tube neck 11 is a picture centering device 16 which is tightly clamped to the neck of the tube 11 in engagement with the rear face 18 of the sweep yoke assembly 14. The centering device 16 thus serves to hold the sweep yoke assembly 14 tightly against the flared out portion 12 of the tube thereby to prevent relative movement between the tube and the sweep yoke assembly 14. Rotational movement of the sweep yoke assembly 14 would, of course, cause a rotation of the picture on the face of the tube and axial movement of the sweep yoke assembly 14 would cause a variation in the size of the picture. The centering device 16 embodies certain features of the present invention more fully described hereinafter and includes a pair of ring magnets savages (not fully shown in FIG. 1) which respectively include rearwardly extending tab portions 2t) and 21 to permit orbital adjustment of the ring magnets about the principal longitudinal axis of the tube neck 11.

Refer now to FIGS. 2, 3 and 4, for a more detailed description of the centering device 16 of the present invention. In accordance with an important feature of the present invention the centering device 16 comprises a unitary molded member including a rearwardly extending clamping sleeve portion 24, a forwardly disposed flat, circular flange 26 for engagement with the rear face of the sweep yoke assembly, and a plurality of rearwardly extending arcuate projections 28 for supporting a pair of magnetic rings 30 and 3]..

The sleeve 24 is longitudinally split throughout its length and a pair of outwardly extending

radial ears

33 and 34 are provided on the slit defining marginal edges of the sleeve 24. The

cars

33 and 34 are provided with aligned apertures through which a self-tapping screw 33 may be placed after the device 16 has been placed over the tube neck 11. Tightening of the screw 3% draws the

ears

33 and 34 together, thereby to tighten the rearward sleeve portion onto the tube neck 11. In order to provide greater flexibility for the rearward portion of the sleeve 24 which serves as the tube grasping clamp portion, an arcuate slot 36 is provided in the sleeve 24 just forward of the clamp portion. The portion 4d of the sleeve 24 is thus reduced in arcuate length and connects at its forward end with the circular flange 26. The flange 26 is provided with a central opening which is largest in the upper portion thereof and which is located opposite to the upper, flexible clamping portion of the sleeve 24. In addition, the hole through the flange 36 is further enlarged in the extreme upper area 44 to facilitate molding of the

ear portions

33 and 34.

In order to provide a guideway for slidably mounting the magnetic rings for rotation thereof about the tube neck, the plurality of arcuate projections 28 extend rearwardly from the flange 2d outwardly of the sleeve 24. Each of the projections 28 has an outwardly directed radial lip 48 thereby to define, in conjunction with the body of the projection 28 and the adjacent flange 26, an arcuate channel. The projections 28 all have the same outer magnet receiving radius and are concentrically arranged with respect to the central longitudinal axis of the sleeve 24. A plurality of arcuate slots 50 are provided in the flange 26 directly opposite the lips 43 to facilitate molding of the unit.

In accordance with another feature of the present invention, the magnetic rings 3% and 31 are each formed of a length of magnetic stock which, as best shown in FIG. 4, is substantially square in cross section and which, as best shown in FIG. 2, has a central portion thereof formed in a substantially complete circle with the two ends being bent outwardly in a plane extending through the axis of the sleeve 24 and extending at an angle of approximately 45 degrees with respect to the plane of the respective circular portion. The ends 52 and 53 of the magnet 31 and the corresponding ends of the magnet 30 thus lie in mutual juxtaposition and are held tightly together by means of a flexible tubular member 55 which may be formed of a suitable plastic material. In order to assemble the magnets 39 and 31 to the molded portion of the assembly, the previously circularized magnets are slightly sprung open and snapped into place over the rearward lips 48 on the projections 28. The two magnets should be snapped in place, one in front of the other, and thereafter the sleeves 55 are inserted over the offturned ends of the magnet rings to secure the magnets to the molded part and to provide a friction fit between the projections and the internal surface of the magnets thereby to prevent spurious movement of the magnets after they have been adjusted.

The present invention has thus far been described in connection with a centering device for use with a complete sweep yoke assembly. However, the present in vention may be directly incorporated in the molded rear end cup of a sweep yoke assembly thereby decreasing the cost of the unit inasmuch as the sweep yoke assembly rear cover and the centering and clamping unit may be molded in a single operation. Referring to FIG. 5, therefore, there is shown a cup-like member 60 which includes a circular flange portion 62 terminating at its inner end with the magnet-holding and clamping construction described in connection with FIGS. 2, 3 and 4. In FIG. 5, those portions which are like similar parts in FIG. 4 are designated by the same reference numerals with a prime affixed thereto. By comparing FIGS. 4 and 5, it will be seen that the flange 62 is identical at its inner end with the flange 26 and with the remaining parts of the assembly 16. However, in the member 60, the flange portion 26' extends outwardly a suflicient distance to terminate in a cylindrical side wall portion 64 which overlies the rearward wall of a sweep yoke assembly and is provided with a reentrant lip 65 useful in securing the cover 69 to the remainder of the sweep yoke assembly.

While the present invention has been described in connection with particular embodiments thereof, it will be understood that those skilled in the art may make many changes and modifications without departing from the true spirit and scope of this invention and, therefore, it is intended in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of this invention.

We claim:

1. A device adapted to be mounted on the neck of a television picture tube for use in controlling the position of the picture on the viewing screen of the tube, said device comprising an integrally molded member having a longitudinally split, generally cylindrical sleeve for receiving said neck portion of said tube, a pair of radial ears extending outwardly from said sleeve on the respective edges of said sleeve along said slit, said ears having aligned apertures for reception therein of an elongated fastening device, a circular flange extending outwardly from said sleeve in a plane substantially normal to the principal longitudinal axis of said sleeve, said flange being longitudinally spaced from said ears, a plurality of projections on said flange extending parallel to said axis in radially spaced relationship with said sleeve, and a plurality of radially directed lips on the marginal ends of said projections, said lips, said projections and said flange providing a circular guideway for rotatably mounting a pair of magnetic rings.

2. A device adapted to be mounted on the neck of a television picture tube for use in controlling the position of the picture on the viewing screen of the tube, said device comprising an integrally molded member having a longitudinally split, generally cylindrical sleeve for receiving said neck portion of said tube, a pair of radial ears extending outwardly from said sleeve on the respective edges of said sleeve along said slit, said ears having aligned apertures for reception therein of an elongated fastening device, a circular flange extending outwardly from said sleeve in a plane substantially normal to the principal longitudinal axis of said sleeve, said flange being longitudinally spaced from said ears, a plurality of projections on said flange extending parallel to said axis in radially spaced relationship with said sleeve, a plurality of radially directed lips on the marginal ends of said projections, and a pair of generally circular permanently magnetized rings rotatably mounted on said projections, said rings each being substantially square in cross section.

3. A device as set forth in claim 2 wherein said circular flange is connected to one end of said sleeve and is provided with a circumferential slot opening into the slot in said sleeve.

4. In a combination sweep yoke assembly cover and magnetic centering device comprising a unitary molded member having a cup-like portion including a forwardly extending cylindrical sleeve and a circular flange, a rearwardly extending arcuate portion on said flange, a split sleeve portion at the rearward end of said arcuate portion, said flange having an axially disposed tube receiving aperture therein, a plurality of rearwardly extending hook-like projections on said flange equally spaced from the longitudinal axis of said sleeve, said arcuate portion being longer in the axial direction than said projections to provide a clearance space between said split sleeve and said projections, and a pair of ears extending outwardly from said sleeve near the marginal ends or" said sleeve defining said slit.

5. In a combination sweep yoke assembly cover and magnetic centering device comprising a unitary molded member having a cup-like portion including a forwardly extending cylindrical :sleeve and a circular flange, a rearwardly extending arcuate portion on said flange, a sleeve portion at the rearward end of said arcuate portion for mounting said combination sweep yoke assembly cover and magnetic centering device on associated picture tubes, said flange having an axially disposed tube receiving aperture therein, a plurality of rearwardly extending projections on said flange on which magnetic rings may be mounted, said arcuate portion being longer in the axial direction than said projections to provide a clearance 10 space between said sleeve and said projections.

References Cited in the file of this patent UNITED STATES PATENTS 2,482,129 Schneiderman Sept. 20, 1949 15 2,552,341 Mucher May 8, 1951 2,922,909 Heller Ian. 26, 1960

Claims

5. IN A COMBINATION SWEEP YOKE ASSEMBLY COVER AND MAGNETIC CENTERING DEVICE COMPRISING A UNITARY MOLDED MEMBER HAVING A CUP-LIKE PORTION INCLUDING A FORWARDLY EXTENDING CYLINDRICAL SLEEVE AND A CIRCULAR FLANGE, A REARWARDLY EXTENDING ARCUATE PORTION ON SAID FLANGE, A SLEEVE PORTION AT THE REARWARD END OF SAID ARCUATE PORTION FOR MOUNTING SAID COMBINATION SWEEP YOKE ASSEMBLY COVER AND MAGNETIC CENTERING DEVICE ON ASSOCIATED PICTURE TUBES, SAID FLANGE HAVING AN AXIALLY DISPOSED TUBE RECEIVING APERTURE THEREIN, A PLURALITY OF REARWARDLY EXTENDING PROJECTIONS ON SAID FLANGE ON WHICH MAGNETIC RINGS MAY BE MOUNTED, SAID ARCUATE PORTION BEING LONGER IN THE AXIAL DIRECTION THAN SAID PROJECTIONS TO PROVIDE A CLEARANCE SPACE BETWEEN SAID SLEEVE AND SAID PROJECTIONS.