CRT assembly

Abstract

A simplified means for supporting the components of a high resolution CRT assembly without utilizing a separate rigid metal frame is disclosed. The components including the CRT, coils and coil positioners are supported by the magnetic shield thereby eliminating the necessity of the intermediate rigid frame without impairing the precision and performance of the CRT function.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improved, low-cost, simplified means for supporting and magnetically shielding the components used in a high resolution CRT assembly or similar devices such as vidicons, orthicons and image converters.

2. Description of Prior Art

Many cathode ray tube (CRT) assemblies include a high resolution CRT and its associated components including a rigid metal structure to which are attached the CRT, coils and micropositioners. Reference is made to Litton Industries Model 1019 Precision Universal Mount which is typical of a rugged mount for use with magnetically deflected CRT's. Most known mounts of this type utilize a rigid support structure including four steel bars with the CRT and the related deflection, focus and other components attached to the rigid support structure for support. A separate magnetic shield which covers all of the CRT components including the rigid structure is provided to prevent external magnetic influences on CRT operation. Unfortunately, such an assembly is quite bulky, expensive to produce and difficult to maintain.

SUMMARY OF THE INVENTION

This invention relates to an improved low cost cathode ray tube (CRT) assembly which permits the use of the magnetic shield for (1) shielding the CRT from external magnetic effects and (2) supporting the CRT and all of the CRT related components. The CRT components, including the CRT, coils, micropositioners and the like are mounted on the magnetic shield in a unique assembly thereby eliminating completely the use of a separate support frame and the supporting of the components thereby. The result is elimination of extensive assembly and maintenance problems, cost saving of material used in the rigid structure and the like. These advantages are obtained without reducing the performance of the CRT assembly or its function.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a prior art CRT support assembly.

FIG. 2 is a side view, partially in section, of one embodiment of the assembly of the invention.

FIG. 3 is a front view of the embodiment shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, the same reference numeral is used in conjunction with similar components. However, the suffix P is included in all reference numerals associated with the prior art device shown in FIG. 1.

FIGS. 2 and 3 are referred to concurrently. CRT assembly 10 is an assembly which may be utilized in the system described in co-pending applications bearing U.S. Ser. Nos. 359,590 and 359,591 both entitled Character Generating Method and System by R. L. Caswell and G. D. Evans, respectively and assigned to the common assignee. Magnetic shield 12 is shaped to encase all the CRT components and substantially all of CRT 14. In a preferred embodiment, magnetic shield 12 comprises two layers 11 and 13 of magnetic shielding material such as permalloy or mu-metal which provides proper magnetic shielding of a CRT. In a preferred embodiment, the inner layer 11 of magnetic shield 12 is used as the frame for supporting the CRT and the related components. Thus, magnetic shield 12 has the dual purpose of magnetically shielding CRT 14 and providing a rigid structure to which all CRT components including the CRT are mounted. CRT 14 is secured to inner layer 11 essentially by neck clamp 16 and front clamp 18.

Referring initially to FIG. 1, there is shown one embodiment of a typical prior art CRT assembly including a CRT and related components. Briefly, this prior art embodiment has the CRT components and the CRT 14P mounted on a rigid frame consisting of a front plate 20P and an end plate 90P connected by four metal bars or rods 80P. This rigid frame is covered by a magnetic shield 13P which is shown broken away for convenience.

In the embodiment of the prior art shown in FIG. 1, the respective micropositioners or holders 46P and 48P have four holes therein in order to be mounted to the four connecting metal rods 80. This is, of course, one requirement that is eliminated by the present invention.

In the preferred embodiment of this invention neck clamp 16 is a simple self-centering clamp which holds CRT 14 securely yet minimizes substantially the possibility of a fracture. Clamp housing 34 is mounted on inner layer 11 by suitable means such as screws 51. Neck clamp 16 secures the neck section of CRT 14 and includes teflon washer 28, rubber ring 30, and clamp retainer ring 32 and housing 34. Housing 34 is in the preferred embodiment, generally annulus-shaped although other configurations are contemplated. A substantially centrally located threaded aperture is included in housing 34. Clamp retainer ring 32 is threaded on its outer surface and threads into the threaded aperture in housing 34 against teflon washer 28 and rubber ring 30 until rubber ring 30 expands and securely grips the neck of CRT 14. Teflon washer 28 serves to reduce the torsion effects on rubber ring 30 which can result from the tightening of clamp retainer ring 32.

Housing 34 also supports alignment coil 36. That is, housing 34 also includes a raised portion, or neck 34A in which coil 36 is secured by set screws 76. For convenience, neck 34A is on the opposite side of housing 34 relative to the threaded aperture.

Centering coil 38 is similarly supported by coil holder 40. Coil holder 40 is mounted at inner layer 11 by suitable means such as screws 75. Holder 40 is also generally annulus-shaped with either a central aperture or neck for receiving centering coil 38. Coil 38 is retained in holder 40 by suitable means such as set screws 76. In general, coils 36 and 38 are intended to be fixed relative to CRT 14 whereby precision positioners (i.e. micropositioners) are not required.

Conversely, focus coil 42 and deflection yoke 44 frequently require precision adjustment. Consequently, these coils are mounted in micropositioners 46 and 48, respectively. Typically, micropositioners 46 and 48 are of the type described in detail in co-pending application U.S. Ser. No. 398,731, entitled Simplified Micropositioner by R. L. Caswell, filed on Sept. 17, 1973, which is incorporated herein by reference. The coils 36, 38, 42, and 44 and clamp housing 34 have apertures to accommodate the neck section of CRT 14.

Micropositioners 46 and 48 are attached to inner layer 11 of magnetic shield 12 by suitable means such as machine screws 50 in each respective member spaced equally as shown in FIG. 2.

Front mounting plate 20 (better seen in FIG. 3) is attached to the front, flared section of inner layer 11 of magnetic shield 12. Front plate 20 has an aperture therein which is shaped to fit the front of CRT 14. In the preferred embodiment, the front or face fiber optics element 90 of CRT 14 projects into or through the aperture in plate 20. Front clamp 18 is arranged within the aperture in front plate 20. Clamp 18 includes a stainless steel band 22 which engages or wraps around three sides of CRT 14. When band 22 is tightened, it draws CRT 14 against one side of the aperture in front mounting plate 20. This aperture side is lined with rubber pad 23.

Front mounting plate 20 includes a pair of slots 24 adjacent to and extending from the ends of the aperture. Clearance holes 77 are provided in the face plate which holes communicate with slots 24. Machine screws 26 which are mounted in clearance holes 77 provide the means for tightening front clamp 18. That is, band 22 has an enlarged section at the ends thereof. These enlarged sections included tapped holes which engage screws 26. The enlarged section fits in slot 24 to prevent band 20 from turning with machine screws 26 when adjusted. As screws 26 are turned, the enlarged sections of band 22 are moved wherein band 22 is adjusted relative to CRT 14.

This type of band adjustment assures that the flared end of CRT 14 will be rigidly secured and that the prealignment adjustments will be maintained without impairing the flexibility of rapid and simple disassembly if required.

The control circuitry for CRT assembly 10 is channeled through prefabricated holes in both layers of magnetic shield 12. Electrical leads from the respective coils and the CRT anode are brought out through insulating bushings 52 which are press fitted in the magnetic shield 12. Focus coil 42 and deflection yoke 44 leads go to connector 54 as shown in FIG. 2. The conductor leads of centering coil 40 and alignment coil 38 go to printed circuit board 56. PC board 56 contains circuitry which is the primary source for regulating the currents for coils 38 and 40. Power for PC board 56 is provided through connector 54. It is advantageous to incorporate the current control as part of the CRT assembly inasmuch as this permits prealignment of CRT assembly 10 when it is assembled utilizing the same current settings used when the CRT assembly is set in operation. Prealignment of the CRT assembly using these settings provides more accuracy and eliminates the effort of additional later current settings.

The time and materials saved by elimination of the frame and attachments thereto of the prior art as well as incorporation of the centering and alignment current settings into the same physical assembly can readily be seen.

The mechanical characteristics, i.e. the cross-section moment of inertia and Young's modulus of a typical magnetic shield are well adapted for use as a rigid support when properly rigid attachments to it are made as in the present invention. Frequently the magnetic shield weighs more than the total of other CRT components; hence the magnetic properties of the shield (which could be impaired by high stresses) are not significantly affected by supporting the weight of the other CRT components.

Access to the CRT base 58 to connect or remove the CRT socket which plugs into CRT base 58 is made by removing shield cap 60.

In describing the actual assemblng of CRT assembly 10 consider that inner magnetic shield 11 is the mounting structure for all of the CRT components; i.e. all the CRT components, including front plate 20, will be attached to the inner magnetic shield. The deflection yoke 44 is mounted in the micropositioner 48 which is installed in the inner magnetic shield through the unflared end of the shield. The same procedure is followed with focus coil 42 and micropositioner 46. The respective electrical leads are fed through the insulating bushings in prefabricated holes in inner magnetic shield 11. Next, centering coil 38 is mounted on coil holder 40 and positioned in inner magnetic shield 11 through the rear section of the inner magnetic shield 11. The coil leads are fed through prefabricated holes in inner magnetic shield 11. Finally, alignment coil 36 is mounted on neck clamp housing 34 and positioned in the inner magnetic shield assembly and its respective leads are fed through the insulated, prefabricated holes in magnetic shield 11. Each respective micropositioner and holder is physically attached to the magnetic shield by machine screws 50 or 51. Spacers 53 are positioned on the surface of inner magnetic shield 11 to support outer magnetic shield 13. These spacers may be in the nature of a plurality of individual stand offs or alternatively appropriate plate-like members. In the preferred embodiment, spacers 53 are generally rectangular with substantially circular apertures therein. Thus, outer layer 13 is rectangular while inner layer 11 is circular. Of course, these configurations can be readily modified without departing from the inventive teachings herein.

The respective electrical leads are fed through holes in outer magnetic shield 13, insulating bushings 52 are fitted over the leads, and the bushings are press-fitted through the prefabricated holes in outer magnetic shield 13. PC board 56 is mounted on outer magnetic shield 13 and centering coil 38 leads and alignment coil 36 leads are connected to PC board 56. PC board 56 is electrically connected to connector 54. The CRT anode 57 lead, deflection and focus coil leads also are fed through prefabricated holes and through bushings and are connected directly to connector 54. Front mounting plate 20 is attached to the front of the inner shield 11.

The CRT 14 is now ready to be mounted. The CRT neck is passed through the front end of the magnetic shield assembly and through the apertures in deflection yoke 46, focus coil 44, centering coil 40, alignment coil 38, clamp housing 30, and neck clamp 16. As this is being done the anode lead is attached to the CRT. Neck clamp 16 is lightly adjusted on the CRT neck. At this point front clamp 18 is installed in front mounting plate 20 and adjusted to secure the flared end of CRT 14. Neck clamp 16 is then adjusted to secure the neck of CRT 14. The shield cap is attached and CRT 10 is now assembled and ready to be aligned.

Once the CRT assembly is aligned and ready for operation, it is physically mounted to a system by its front mounting plate, i.e. supported by only the front mounting plate, and installed for operation vertically with the front mounting plate face up. The mechanical rigidity of this CRT assembly is more than adequate to withstand operation use without noticeable degradation of the alignment.

Thus, there has been shown a CRT assembly without the conventional rigid structure, and which maintains the precision and performance of the CRT function by utilizing the magnetic shield as the supporting structure as well as for magentic shielding purposes.

In addition to eliminating the rigid metal structure, another advantage of mounting the CRT components directly to the shield is that it can be accomplished by simply tapping four holes in each respective assembly to be mounted and engaging same by four machine screws through four holes in the shield. Whereas in the conventional rugged type mount assembly four precision jig bored holes are required in each component to be mounted on the frame to accommodate the four rods of the structure and in addition four tapped holes and four set screws are necessary to secure each mount to the rods and finally the mounting of the magnetic shield onto the rigid structure requires additional tapped holes and set screws to secure the magnetic shield to the rigid structure.

Thus, elimination of the frame in a CRT assembly not only eliminates the cost of the frame and additional cost for attachment of other CRT components to it but the size of the shield is also reduced and thus it is less expensive to manufacture.

The embodiment shown and described is illustrative only. It is not meant to be limitative of the invention. Certain modifications will be suggested to those skilled in the art. For example, outer layer 13 may be eliminated in some cases. Moreover, it should be clear that the assembly is fabricated of suitable non-magnetic material such as plastic, aluminum and the like, except for shield 12 which is a high permeability at low induction magnetic shielding material. The scope of the invention is to be defined only by the claims appended hereto.

Claims

What is claimed is:

1. A cathode ray tube assembly for housing a CRT comprising:

at least one precision positioner means having an aperture to accommodate said CRT;

front plate means for securing the face end portion of said CRT;

at least one coil holder means having an aperture to accommodate another portion of said CRT;

clamp means for securing still another portion of said CRT;

said clamp means comprising a housing having a threaded aperture therein through which said CRT extends, a retainer ring having a threaded outer surface, and a pliable spacer, which expands into said aperture when said retainer ring is threaded into said threaded aperture of the clamp housing and compresses said spacer thereby forcing said pliable spacer to grip said CRT; and

magnetic shield means connected to said front plate means, said precision positioner, said coil holder and said clamp housing to provide a support structure therefor.

2. The cathode ray tube assembly as recited in claim 1 wherein said magnetic shield further includes control circuitry attached thereto for setting and regulating at least one of the currents of said CRT assembly.

3. The cathode ray tube assembly as recited in claim 1 wherein said front plate means for securing the face end of said CRT includes:

a metal band;

a resilient member interposed between said metal band and the interior surface of an aperture in said front mounting plate means; and

means connected to each end of said metal band for adjusting the portion of said metal band relative to the sides of the flared end of said CRT and drawing said CRT against one side of said aperture.

4. The cathode ray tube assembly as recited in claim 1 wherein said clamp means includes washer means intermediate said retainer ring and said pliable spacer.

5. The cathode ray tube assembly as recited in claim 1 wherein said magnetic shield means has an enlarged, flared end adjacent said front plate means.

6. The cathode ray tube assembly as recited in claim 1 wherein said magnetic shield includes a pair of spaced apart layers separated by spacers.

7. The cathode ray tube assembly as recited in claim 6 wherein each layer of said pair of spaced apart layers has a different configuration.

8. The cathode ray tube assembly as recited in claim 7 wherein at least one of said layers is of substantially cylindrical configuration.