Mounting Assembly For A Convergence Coil

Abstract

A convergence coil assembly primarily for use with multigun cathode ray tubes and for mounting on a printed circuit board in which resilient mounting posts permit radial movement of the convergence coil assembly but limits skew and axial movement. A compact, economical supporting structure is shown, as well as a unique means for containing a shorting bar and for retaining the permanent magnet which is used for static convergence adjustment.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to convergence coil assemblies for cathode ray tubes. It especially relates to such assemblies used on multigun cathode ray tubes such as commonly used in color television tubes. In particular, the invention relates to such assemblies as are used with and mounted on a printed circuit board containing associated circuitry.

2. Description of the Prior Art

Color television picture tubes of the type employing a shadow mask are provided with convergence circuits by means of which the three electron beams in a delta array are caused to pass through the same hole in the shadow mask at the same time. Thus, the beams must converge at the shadow mask at all points scanned by the beam. When the beams do this, they emerge from the mask at the correct angle to strike the appropriate dot in the triad of color dots on the face of the tube. Normally static as well as dynamic convergence adjustment is required, and to achieve such convergence, it is the practice to subject the beams to auxiliary magnetic fields. Static convergence, that is, adjustment of the beam convergence at a fixed point, usually the center of the screen, is accomplished by a permanent magnet means which bends the individual beam to convergence. Conventionally, an adjustably supported permanent magnet is used for static adjustment. Dynamic convergence, that is, maintaining the beams in proper convergence during scanning, is accomplished by electromagnetic apparatus. These electromagnets are energized by correction signals derived from horizontal and vertical deflection circuits.

Both the permanent magnet and the electromagnets apply their flux to pole piece pairs which are mounted inside the neck of the cathode ray tube. A separate pole piece pair and a separate convergence assembly is associated with each beam in the cathode ray tube. The pole piece pairs typically take the form of elongated members that flank the path of its assigned electron beam to direct the magnetic flux field which is produced between the pole piece pairs across the path of the beam.

It is also desirable to provide some means of temperature compensation in a convergence assembly. This is due to changes in flux density, especially those changes associated with the permanent magnet, as a result of changes in ambient temperature.

The prior art has numerous examples of convergence assemblies which have been used to secure static and dynamic convergence.

Convergence coil assemblies of the prior art are described in the following U.S. patents which are cited strictly for the purpose of illustration and are not exhaustive of the subject matter:

3,777,512 3,617,962 3,496,501 3,629,752 3,590,302 3,623,151

The typical convergence coil assembly has a pair of L-shaped core pieces assembled in a U formation with windings for the vertical and horizontal convergence on each of the parallel legs of the U formation. The abutting legs of the U formation forming the bight of the U have a non-magnetic gap across which the flux of the permanent magnet is applied. The U formation and its windings and the permanent magnet are assembled in a housing usually of plastic.

With the increasing use of printed circuit boards, it has become common to mount the associated vertical and horizontal convergence control circuitry on a printed circuit board shaped to fit around the neck of the cathode ray tube. The convergence coil assemblies are also mounted on the printed circuit board at the 120.degree. angle to each other consistent with the disposition of the electron beams and their pole piece pairs on the neck of the cathode ray tube. The convergence coil assemblies as they are installed with the printed circuit board on the neck of the tube must have their parallel legs of the L-shaped cores aligned with their cooperating pole pieces. The ends of the parallel legs of the cores are canted to fit the curvature of the neck. It is important that the ends of the parallel legs be in contact with the glass of the tube neck in order to minimize the space between the L-shaped cores and their respective pole pieces inside the neck. In this respect, it should also be noted that the diameter of the tube neck varies from one tube to another and therefore the convergence assembly must be able to move radially to accommodate such difference. In considering this, it has been a problem to mount the convergence assembly on the printed circuit board in such manner as to permit such radial movement while closely limiting skew type movement, that is, movement out of the correct angular orientation with the pole piece pairs. In addition, it is important that the convergence coil assembly remain in firm contact with the printed circuit board in order to closely control its axial position on the neck of the cathode ray tube.

In a further adaptation, a shorting bar is applied around the L-shaped cores. The shorting bar is required because the convergence coil assembly is usually in proximity to the deflection assembly and its high magnetic field. The shorting bar serves to protect the convergence assembly from undesired effects of the deflection magnetic field.

As is commonly the case, the cost and size are important considerations in all factors of design of the convergence assembly. The invention described and claimed below provides in a small economical package a convergence assembly providing for accurate and stable emplacement and functioning.

SUMMARY OF THE INVENTION

A convergence coil assembly including electromagnetic dynamic convergence means and permanent magnet static convergence means, a supporting structure, and mounting means in which a first mounting lug pair close to the point of application to a cathode ray tube neck permits radial and skew movement and prohibits lifting from a printed circuit board and a second mounting lug pair radially distant from the point of application to the tube neck with respect to the first mounting pair permits radial movement and prohibits skew movement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 An assembled view showing convergence assemblies of the invention on a printed circuit board and mounted on a cathode ray tube neck.

FIG. 2 A sectional front view of a convergence assembly of the invention on line II--II of FIG. 3.

FIG. 3 A sectional side view of the convergence assembly of the invention on line III--III of FIG. 2.

FIG. 4 is a top partially sectional view of the convergence assembly of the invention.

FIG. 5 is a bottom partially sectional view of the convergence assembly of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, convergence coil assemblies 1 are shown in an orientation 120.degree. apart and mounted upon a printed circuit board 2. While the details of the printed circuit board and the circuit components mounted on it are representative of one in actual use, no further explanation of these details will be given. This is because such additional details would not enhance understanding of the following description. It is sufficient to understand that the elements illustrated are those comprising the circuitry of the vertical and horizontal convergence control circuits in conjunction with the respective vertical and horizontal convergence control windings. Normally, the convergence assembly 1 will be provided with protective tape 3 around the windings as shown on two of the assemblies. The tape 3 has been omitted from one of the assemblies to show the details of the assemblies. The L-shaped core pieces 4 are arranged in a U formation well illustrated in the sectional view of FIG. 2. The core pieces 4 have parallel legs 5 forming the sides of the U formation, and abutting legs 6 forming the bight of the U. Although the term abutting is used here for descriptive purposes, it should be understood that these legs 6 terminate leaving a gap. The legs 5 terminate with canted ends 7 in order to fit the curvature of the neck 8 of the cathode ray tube. The legs 5 are generally parallel and spaced so that when the assembly is in place on the neck 8 of the tube, they will operatively align with pole piece pairs 9 which flank the electron beams 10.

Referring to FIGS. 2 and 3, it can be seen that two sets of windings are operatively applied to the core pieces 4. For horizontal convergence control, the inside or horizontal winding 11 is on the horizontal bobbin 12. For vertical convergence control the outside or vertical winding 13 is on a vertical bobbin 14.

With the upper flange 15 and the lower flange 16 and the spring clip 17, the horizontal bobbin 12 and the vertical bobbin 14 constitutes the supporting structure of the convergence assembly.

In the gap between the abutting legs 6 is a metallic temperature compensating element 18 which is described in detail in U.S. Pat. No. 3,590,302 issued on June 29, 1971 to Robert W. Bussey. A piece of tape 19 may be emplaced in the gap to act as a dielectric and thereby separate the faces of the L-core.

Mounted above the legs 6 is a permanent magnet 20 in the form of a disc. This element is similar in function and form to those previously known in the art. It is adapted to rotate on an axis radial to the tube neck 8 to adjust the magnetic flux delivered to the pole piece pair 9. The permanent magnet 20 adjusts static convergence.

The permanent magnet 20 is rotatably held in place on the legs 6 by the spring clip 17 shown in FIGS. 2 and 4. The spring clip 17 is made by punching and forming a metal, such as phosphor bronze, spring tempered, to provide the required retaining forces. A central bearing surface 21 has a dimple 22 which resides inside a hole 23 centered in the permanent magnet 20. From opposite sides of the bearing surface 21 legs 24 extend outwardly and downwardly at an angle to clear the permanent magnet 20. The legs 24 then turn downwardly to a terminal portion having shoulders 25. The shoulders 25 are held in upstanding retaining clips 26 extending from the upper flange 15. The terminal portions also push on the outboard ends of the abutting legs 6, exerting an inward force on them. The retaining clip 26 allows some sliding of the shoulders in order to facilitate the inward force.

Now referring to FIGS. 4 and 5, a first pair of mounting lugs 27 are fitted to the lower flange 16. A second pair of mounting lugs 28 are fitted to the upper flange 15. For convenience, the first pair of mounting lugs 27 may be referred to as the lower lugs or as being proximate to the tube neck 8. Also, the second pair of mounting lugs 28 may be referred to as the upper lugs or as being distant from the tube neck 8.

Before describing the lugs and their operation in detail, some further explanation of the entire assembly will be helpful. When installed, the printed circuit board 1 resides in a radial plane relative to the tube neck 8 and the generally parallel core legs 5 are parallel to a radial line extending from the tube neck 8 normal to its axis A and midway between the pole piece pairs 9.

Thus, in this description, radial movement refers to movement along the radial line as at B in FIGS. 1 and 2. Skew movement refers to movement to the left or right (as seen in FIG. 1 of the upper assembly) of the radial line as at C in FIGS. 1 and 2. This movement may take place circumferentially around the tube neck 8, that is, it may be arcuate movement.

Radial movement is desired because the tube necks are manufactured with a certain amount of tolerance. Typically, a tube neck will have a nominal diameter of 1 7/16 inch .+-. 1/16 inch. Thus, in order to assure an intimate contact between the canted core feet ends 7 and the tube neck 8, the coil assemblies are made to mount on the printed circuit board to fit the smallest diameter, 13/8 inch. For larger diameters, the convergence coil assembly herein described is able to move radially outward. The mounting lugs 27 and 28 described in detail below provide this radial movement.

Some slight skew movement of the converging assembly is in fact desired close to the tube neck 8 in order to provide good seating of the canted core feet 7 on the tube neck 8. However, skew movement radially outboard of the tube neck 8, such as at the upper lugs 28 can result in misalignment of the L core legs 5 and the pole piece pairs 9, to a degree that can adversely affect operation. Thus, the lower lugs 27 permit some skew movement but the upper lugs 28 prohibit skew movement.

In addition to radial and skew movement, upon assembly and adjustment of the printed circuit board 2 to the tube neck 8, there is a force tending to pull the convergence assembly away from the printed circuit board due to drag of the core feet 7 on the tube neck 8. The lower mounting lugs 27 described herein prohibit such movement.

Having thus described the preferred embodiment of the mounting lugs, there follows an additionally detailed description.

Referring to FIGS. 2, 4 and 5 the upper and lower flanges 15 and 16 are similarly made having a rectangular perimeter with small rectangles removed at the corners 29. A slot 30 extends along the short edges of the flanges and continues around the corners extending only a short distance along the long edge. The lower lugs 27 fit in the slot 30 as shown in FIG. 5 and the upper lugs 28 fit in the slot 30 as shown in FIG. 4.

When so assembled, the lower lugs 27 extend out of the ends of the lower flange 16 about midway defining a pivot point 31 and then have a flexing portion 32 which extends parallel to the tube neck axis A, beyond the flange and terminate in a termination portion 33 which is received and held in the printed circuit board 2. The pivot point 31 allows the lugs 27 to flex when the coil assembly is moved in the radial direction, without interfering with the flange 16. The pivot point 31 is selected to space the lugs slightly from the side of the flange 16 and also to permit some skew direction flexing of the lugs 27.

When so assembled, the upper lugs 28 have a flexing portion 34 extending from the corner 29 of the flange 15 oppositely and outward in a radial plane relative to the tube neck 8 and normal to the tube axis A. It is preferably also normal to the radial line B. A termination portion 35, constituting that part which is received and held in the printed circuit board 1 is normal to the first portion and parallel to the tube axis A. The slot 30 is enlarged at 36 (FIG. 2) in order to permit flexing of the first portion during radial movement of the convergence assembly. The flexing portion 34 has a pivot point 37 from which the radial flexing commences. However, the termination portion 35 having no substantial free length permits substantially no skew movement.

The upper and lower lugs are preferably formed from a highly resilient wire for example 0.020 inch diameter steel music wire. They may be secured to the flanges, which may be made of thermoplastic material by heating selected portions of the plastic to flow and close the slots 30.

As thus described, comparing the lugs 27 and 28, the lower lug 27 has a relatively long flexing portion 32, e.g., about one quarter inch, for radial and skew movement, while the upper lug 28 has relatively much less flexing capability for skew motion, in fact substantially none, i.e., the termination portion 35. For the upper lug 28, the flexing portion 34 is about the same length, e.g., about one quarter inch as the flexing portion 32, providing about the same capability for radial movement. Furthermore, the lower lug 27 has substantially no portion permitting axial movement, while the upper lug 28 has in its flexing portion 34 some capability for axial movement. This latter is of no effect because the axial force from the drag of the core ends 7 is not transmitted to the upper lugs.

The lugs 27 and 28, in addition to their mounting function, preferably also serve as termination for the vertical and horizontal windings. To accomplish this each lug has a wire receiving portion 38 constituting its passive end, which extends oppositely outward from far corners of the flanges 16 and 17. The vertical windings 13 are terminated to the upper lugs 28. The horizontal windings 11 are similarly terminated to the lower lugs 27, the winding wire in this case running through slots 39 in the lower flange 16. The respective windings on each L core are also, of course, connected to each other.

In the upper flange 15 as seen in FIGS. 2, 3 and 4 a shorting bar 40 resides in an opening 41. The shorting bar 40 protects the convergence coil assembly from effects from other elements of the television receiver circuitry particularly the high magnetic field of the deflection coil which is positioned nearby. In this preferred embodiment, the vertical bobbins 14 are ultimately joined together fully enclosing the shorting bar 40. In the assembly operation the shorting bar and the vertical bobbin 14 with its winding 13 already on it, are assembled to each other and in a later step, the L cores 4 are inserted into the vertical bobbins 14 and then the horizontal bobbins 12 are installed. Thereafter the permanent magnet 20 and the spring clips 17 are assembled. By the manner and means for retaining the shorting bar its position with respect to the windings is simply and effectively assured.

While the above description relates to certain embodiments now known to and preferred by the inventors, it is possible for persons skilled in the art to make certain additions, changes and modifications. It is intended by the appended claims to cover such additions, changes and modifications as fall within the scope and spirit of the invention.

Claims

We claim:

1. A convergence assembly for use with a cathode ray tube and for mounting on a printed circuit board comprising;

a supporting structure having a lower portion for mounting proximate to a cathode ray tube neck and an upper portion for mounting radially distant from a cathode ray tube neck,

magnetic flux producing means contained by the supporting structure,

mounting means including a lower mounting lug pair extending from the lower portion of the supporting means which is resilient in the radial and skew directions and substantially rigid in the axial direction of a cathode ray tube neck and having a mounting portion for inserting into a printed circuit board, and

an upper mounting lug pair extending from the upper portion of the supporting means which is resilient in the radial direction of a cathode ray tube neck and having a mounting portion for inserting into a printed circuit board,

whereby upon assembly to a cathode ray tube neck the convergence assembly being mounted on a printed circuit board will be slightly movable with respect to the printed circuit board in the radial direction and slightly movable in the skew direction only at its portion near to the cathode ray tube and will be immovable in the axial direction.

2. The convergence assembly of claim 1 wherein the upper mounting lugs further comprise;

a pair of resilient metal members each having a flexing portion extending in a radial plane outwardly from the supporting structure on opposite sides of and normal to the radial axis and adapted to be secured to a printed circuit board thereby permitting resilient movement of the assembly in the radial direction relative to the cathode ray tube, by flexing of the flexing portions,

and the lower mounting lugs further comprise;

a pair of resilient metal members having a flexing portion extending generally parallel to the axis of a cathode ray tube from the supporting structure on opposite sides of and normal to the radial axis and adapted to be secured to a printed circuit board thereby permitting resilient movement of the assembly in the radial and skew directions relative to the cathode ray tube by flexing of the flexing portions.

3. The convergence assembly of claim 2 wherein the lugs are resilient conductive wire and are electrically connected to the magnetic flux producing means and the terminal end of each wire is bent back upon itself to provide a larger post to fit in a mounting hole in a printed circuit board.

4. The convergence assembly of claim 1 wherein the support structure has a generally rectangular shape at its upper and lower portions and the lower mounting lugs extend from opposite shorter sides and the upper lugs extend from opposite corners thereof.

5. The convergence assembly of claim 1 wherein the mounting lugs are of a resilient conductive metal and are electrically connected to the magnetic flux producing means and have means for connecting them to conductors on a printed circuit board.

6. The convergence assembly of claim 1 wherein the magnetic flux producing means comprises;

L shaped core members assembled in a U formation having generally parallel first legs extending for contact with the neck of a cathode ray tube abutting second legs forming the bight of the U formation,

windings associated with the core members for supplying an electromagnetic flux field to the cathode ray tube; and

bobbin means surrounding at least the parallel first legs of the L shaped core members for supporting the core members and having the windings thereupon to induce the magnetic flux.

7. The convergence assembly of claim 6 wherein the upper mounting lugs further comprise a pair of resilient metal members each having a flexing portion extending outwardly in a radial plane from the bobbin means on opposite sides of and normal to the radial axis and adapted to be secured to a printed circuit board thereby permitting resilient movement of the assembly in the radial direction relative to the cathode ray tube, by flexing of the flexing portions, and the lower mounting lugs further comprise a pair of resilient metal members having a flexing portion extending generally parallel to the axis of a cathode ray tube from the bobbin means on opposite sides of and normal to the radial axis and adapted to be secured to a printed circuit board thereby permitting resilient movement of the assembly in the radial and skew directions relative to the cathode ray tube by flexing of the flexing portions.

8. The convergence assembly of claim 7 wherein the lugs are resilient conductive wire and are electrically connected to the magnetic flux producing means and the terminal end of each wire is bent backupon itself to provide a larger post to fit in a mounting hole in a printed circuit board.

9. The convergence assembly of claim 1 further comprising a printed circuit board to which the convergence assembly is mounted by means of the mounting lugs.

10. The convergence assembly of claim 8 further comprising a printed circuit board to which the convergence assembly is mounted by means of the mounting lugs.

11. The convergence assembly of claim 7 wherein the support structure has a generally rectangular shape at its upper and lower portions and the lower mounting lugs extend from opposite shorter sides and the upper lugs extend from opposite corners thereof.

12. The convergence assembly of claim 8 wherein the bobbin means comprises a lower generally rectangular flange having a slot on each outboard side thereof for receiving and seating the lower mounting lugs respectively therein and generally rectangular upper flange having a slot on each outboard side thereof for receiving and sealing the lower mounting lugs respectively therein.

13. The convergence assembly of claim 6 wherein the bobbin means comprises separate bobbin means on each parallel leg abutting centrally thereof and having a cavity in each upper flange portion which cavities meet to form an enclosed cavity and the parallel legs pass through the cavity and also having a shorting bar situated inside the cavity and surrounding the L core legs.

14. The convergence assembly of claim 13 wherein the bobbin means comprises a first bobbin means containing vertical windings and having the flanges thereon and second bobbin means containing horizontal windings being assembled on the L core legs inside a portion of the first bobbin means.