Abstract:
The present invention discloses a color CRT system that can be easily adapted for installations in either the northern or the southern hemisphere. The CRT is symmetrical with respect to its yamming or set up for the earth&#39;s magnetic field so the CRT can be installed in either a normal or an inverted orientation. Likewise the yoke and yoke connector are designed and can be easily installed so the CRT scan starts in the upper left of the CRT in either the normal or inverted installation. The connectors for the neck video card are designed to exit the side of the card so the wires can be routed to the CRT system card in either CRT installation orientation. Finally the anode wire is made with a length and attachment point such that the anode is wireable when the CRT is in the normal or inverted orientation. Also disclosed are visual orientation markings on the CRT, the yoke and yoke connectors and the neck video card connectors so it is easy to visually see when all elements are correctly installed for either the northern or the southern hemisphere installations.

Description:
TECHNICAL FIELD 
     The present invention relates in general cathode ray tubes used in display systems, and in particular, to color displays using cathode ray tubes that installed in data processing systems that are marketed world wide. 
     BACKGROUND INFORMATION 
     Cathode ray tube (CRT) displays are used in televisions, most computer displays and many other displays and monitors. Color CRTs create images by impinging an electron beam on the face of an evacuated glass tube that has been coated with phosphors that emit light at the primary colors. The intensity of the colors depends on the intensity of the electron beam that impinges on the particular emission phosphor. 
     To create a full screen image the electron beams are scanned in a raster and modulated electronically. Moving electrons are affected by and undergo a force if they are moving in a magnetic field. Since CRTs are manufactured in very large volumes, the CRTs are adjusted or “yammed” at the site of manufacture. These adjustments are made to insure that images are placed on the screen or face of the tube for correct viewing. Since the earth has a magnetic field, adjustments made at one point of manufacture may cause viewing errors when the CRT is shipped to a another geographic location, e.g. another hemisphere. Some manufacturers of color CRTs have incorporated correction circuitry to electronically correct for variations in the earth&#39;s magnetic field. 
     Providing CRTs that were adjusted in the factory to compensate for the earth&#39;s magnetic field at the point of use was one of the lowest cost ways to correct the problem. In the early development of color CRTs as many as seven different part numbers were used at times to account for the variations in the earth&#39;s magnetic field at various geographic locations. However, advances in CRT manufacture has reduced to three the number of different CRTs of a type that are manufactured and adjusted for variations in the earth&#39;s magnetic field; one for the northern, southern, and equatorial hemispheres. 
     Since multiple part numbers in any high volume part may create cost and inventory problems, it would be advantageous to further reduce the number of part numbers for CRTs since they are shipped to every part of the world. A method for reducing the number of CRT part numbers that is simple and cost effective is needed. Further, it would be beneficial if the CRT manufacturing method that reduced the number of part numbers also allowed CRTs manufactured in one area to be easily adapted to another. 
     SUMMARY OF THE INVENTION 
     The present invention discloses a method for reducing the part numbers on CRTs manufactured for shipment worldwide. The method includes the steps to produce only two part numbers instead of three normally used for northern hemisphere, southern hemisphere and equatorial hemisphere distribution. The CRT is made and adjusted so that the southern and northern hemisphere parts are symmetrical relative to their magnetic field bias to account for the earth&#39;s magnetic field. To account for the different CRT magnetic field bias needed for the southern and northern hemispheres, the CRT is installed in either normal or inverted orientation. The yoke design for the CRT of the present invention has a connector that can also be installed in either the normal or the inverted connector orientation. The yoke connector enables signals and signal routing so the start scan is in the upper left corner of the CRT when it is in either the normal or inverted orientation. The present invention also has the wiring points to the neck video card that enable proper routing in either the normal or inverted installation of the CRT. The symmetrical design of the CRT and the disclosed configuration of the yoke connections and the neck video card connections a design that reduces to two the CRTs needed for color CRT displays shipped to the, southern, northern, or equatorial hemispheres. The present invention also enables simple conversion of the southern or northern hemisphere CRT by rotating the CRT 180 degrees when installed in a system configured for shipment to either the southern and northern hemisphere. 
     The various parts of the CRT system that are altered for the different installations, CRT, yoke connector and neck video card connectors may also have visual indicators to show when all of the elements are in a correct orientation for a given installation. 
     The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is an illustration of the earth&#39;s magnetic field, 
     FIGS. 2A and 2B illustrate the vector orientation of the magnetic bias field needed to compensate for the earth&#39;s magnetic field for the southern and northern hemispheres respectively; 
     FIG. 3 illustrates an embodiment of the present invention with a CRT orientated for a northern hemisphere installation; 
     FIG. 4 illustrates the embodiment of the present invention shown in FIG. 3 inverted for a southern hemisphere installation; 
     FIG. 5 is a side view of a CRT illustrating features of an embodiment of the present invention; 
     FIGS. 6A and 6B illustrate an embodiment of the present invention illustrating a yoke connector installed in two different configurations of the CRT; and 
     FIG. 7 is a system diagram of a system that could use various embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be obvious to those skilled in the art that the present invention may be practiced without such specific details. In other instances, well-known circuits have been shown in block diagram form in order not to obscure the present invention in unnecessary detail. For the most part, details concerning timing considerations and the like have been omitted inasmuch as such details are not necessary to obtain a complete understanding of the present invention and are within the skills of persons of ordinary skill in the relevant art. 
     Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
     The earth has a magnetic field that affects the electron beam of a CRT by exerting a force and deflecting the beam off of a given path. The earth&#39;s magnetic field is substantially static at a given location but does vary over geographic distances, for example from the northern, southern and equatorial hemispheres of the earth. System electronics that control the CRT display system start scanning the electron beams that “paint” a CRT display image at a particular point on the face of the CRT. Unless the effects of the earth&#39;s magnetic field are accounted for, the starting point of the electron beams will vary depending on the geographical location where the CRT display system is used. CRTs typically have magnetic components positioned around the neck of the CRT that are adjusted at the factory to offset or bias the CRT for a particular geographic installation. The magnetic components are magnetic material that can be magnetized during manufacture to create a bias field. The adjustments made in CRTs at the time of manufacturing are referred to as “yamming”. Present advances in CRT manufacturing have enabled as few as three CRTs with fixed factory magnetic bias adjustments to cover the world market (i.e., northern, southern and equatorial hemispheres). The present invention reduces that number to two, one part for the northern and southern hemispheres and one for the equatorial hemisphere. The present invention also allows the CRT installed for the northern or southern hemispheres to be easily changed so a CRT setup for a northern hemisphere installation can be easily adapted to a southern hemisphere setup and visa-versa. The change from a northern hemisphere to a southern hemisphere installation, or visa-versa can be done in the field away from the factory. 
     FIG. 1 is an illustration of the earth  101  and the earth&#39;s magnetic field. Magnetic field line  100  illustrates a field line exiting and entering the earth essentially perpendicular to the earth&#39;s surface. Because the earth is so large relative to a person or system on the surface, all field lines appear to be perpendicular to the earth&#39;s surface. A CRT display system installed in the northern hemisphere  102  would experience a magnetic field illustrated as a vector perpendicular to the surface illustrated by a field vector pointing up from the earth&#39;s surface. A CRT display system installed in the southern hemisphere  103  would experience a magnetic field, also perpendicular to the earth&#39;s surface, but in the opposite direction as one in the northern hemisphere  102 . The magnetic field is illustrated by a vector pointing into (southern hemisphere) or out of (northern hemisphere) the earth&#39;s surface. Only in the equatorial hemisphere  103  would a CRT display system experience a magnetic field vector that is essentially neutral. 
     FIG. 2A is an embodiment of the present invention illustrating a CRT  200  and showing the direction of a magnetic field bias  205  set to +4 gauss in the vertical direction to offset the earth&#39;s magnetic field  203 . The arrow  203  represents the earth&#39;s magnetic field direction relative to the magnetic field bias  205  in the northern hemisphere. The X  204  represents an electron beam perpendicular to the magnetic field bias  205  and going into the page. Circle  202  illustrates the cross section of the neck of a CRT  202  in which the electron beam X  204  is generated. Circle  210  is illustrative of bias magnetic components placed around the neck of the CRT  202  in such a way as to create a magnetic bias  205 . FIG. 2B illustrates the same CRT  200  rotated  180  degrees for a southern hemisphere installation so the vertical magnetic field bias  205  is now opposite or −4 gauss with respect to a vertical pointing to the top of the page. Arrow  206  represents the earth&#39;s magnetic field direction relative to the magnetic field bias  205  in the southern hemisphere. 
     A CRT  200 , in one embodiment of the present invention, is manufactured with a bias magnetic field that is symmetrical for the requirements of the northern and southern hemisphere installations. In the embodiment illustrated in FIGS. 2A and 2B the magnetic bias field  205  is 4 gauss, the direction of the bias depends on the CRT orientation. Other magnetic bias fields may be used for a particular CRT as long as the symmetry is maintained for a northern and a southern hemisphere installation and the magnetic field bias  205  compensates for the earth&#39;s magnetic field for the particular CRT. When CRT  200  is installed as shown in FIG. 2A, an electron beam illustrated by X  204  would experience a force in one direction resulting from the earth&#39;s magnetic field and in the opposite direction by the magnetic bias field  205 , thus compensating for the earth&#39;s magnetic field. If CRT  200 , with the magnetic bias field  205  in FIG. 2A, was moved to an opposite hemisphere the earth&#39;s magnetic field would be reversed and instead of compensating, the magnetic bias field  205  would add to the force experienced by the electron beam X  204 . If, however, CRT  200  was inverted, the same magnetic bias field  205  would again compensate for the effect of the earth&#39;s magnetic field. 
     FIG. 3 is an illustration of an embodiment of the present invention containing elements of a CRT system and with CRT  301  mounted for a northern hemisphere installation. CRT  301  is illustrated viewing from the rear so the system components and their unique features can be seen. Yoke  305  surrounds the CRT neck  312  (visible in FIG. 5) and contains the magnets used to bias and deflect the electron beam (not shown) that impinges on the CRT face  400  (shown in FIG. 5) of the CRT  301 . The electrical signals that drive the electromagnets in the yoke  305  are coupled via connector  3   17  and cable  304  to the system electronics board  302  with yoke connector  309 . Anode wire  306  connects the system electronics board  302  high voltage output connector  313  to the CRT anode button  321 . An alternate location  320  of the CRT anode button  321  may be present on some CRT products, but this could be easily accommodated by sufficient length of anode wire  306 . Anode connector  307  typically has a rubber boot over its connection point because of the high voltage on the anode wire  306 . System electronics board  302  contains circuits used to drive the CRT system, such as the components discussed below with respect to FIG.  7 . The neck video card  311  is mounted perpendicular to the CRT neck  312  (see FIG. 5) and connects to the system electronics board  302  via wire  308  with neck video connectors  310  and  316 . Installation indicators  300  and  303  may be used so installation or manufacturing personnel can observe the CRT  301  &#39;s orientation relative to its bias adjustment. That is, in FIG. 3, for installation in the northern hemisphere, the indicator  300  is to point upwards and should match with the indicator  319 , explained in further detail below. 
     The video scan of the CRT  301  starts in the upper left hand comer of the CRT when viewed from the front. Since the yoke  305  and its associated electronic components determine the deflection of the scanning electron beam that generates displayed images, the connector  309  must also be symmetrically wired for a northern or southern hemisphere installation. In a northern hemisphere installation the yoke connector  309  plugs in one way and in a southern hemisphere installation it is reversed. The details of yoke connector  309  are shown in FIGS. 6A and 6B. Whenever the CRT  301  is inverted, the yoke connector  309  must also be inverted so the proper signals are altered causing the scan to again start in the upper left corner of the CRT  301  in its inverted orientation, again viewed from the front. Since the CRT  301  could be inverted with also inverting the yoke connector  309  it is desirable to have an indication of when the connector and the CRT  301  are in corresponding orientations. Installation indicators  604  and  608  may be placed on the yoke connector  309  so installation personnel can see if all the connections are proper for a given installation. This would be particularly beneficial if CRTs installed for the northern hemisphere were later inverted for a southern hemisphere installation. After inverting the CRT  301 , personnel could simply observe the indicators to see if the corresponding inversion of yoke connector  309  was done. 
     FIG. 4 illustrates the CRT  301  inverted for a southern hemisphere installation. That is, the CRT  301  is mounted so that indicator  303  points upwards and matches with the orientation of indicator  318 . Since the anode connection via connectors  307  and  313  and wire  306  remain with the CRT, the wire length nor connections have to change. However, the routing of the anode wire  306 , for embodiments of the present invention, is such that no interference with the loop in anode wire  306  occurs with other CRT system components when inverting CRT  301 . Video neck card wire  308  and connector  316  and yoke wire  304  and connector  317  change their orientation with respect to system electronics board  302 . System electronics board connections via connectors  315  and  310  must be changed. Connector  310  may have to be unplugged and re-plugged while inverting CRT  301 . Yoke connector  309  is also inverted when the CRT  301  is inverted, as further described below with respect to FIGS. 6A and 6B. Installation indicator  318  illustrates one embodiment of the present invention with yoke connector  309  having installation indicators consistent with those of CRT  301 . 
     FIG. 5 is a side view of the CRT  301 , system board  302  and the various other components of the CRT system illustrated in FIGS. 3 and 4. The CRT neck  312  is visible only in FIG. 5 as well as the relative position of the yoke  305  on the CRT neck  312 . An electron beam illustrated by  401  is also shown in FIG.  5 . The electron beam  401  is deflected by yoke  305  generating dynamic magnetic fields (not shown). The electron beam  401  is deflected by the yoke  305  and hits, for example, a target  402  on the face  400  of CRT  301 . The other system components shown in FIG. 5 have been already explained; FIG. 5 gives another view of the relationship of components. 
     FIGS. 6A and 6B illustrate a yoke connector  309  in the two orientations discussed previously, one for a northern hemisphere installation (FIG. 6A) and one for a southern hemisphere installation (FIG.  6 B). Wire  600  through wire  605  make up yoke cable  304 . In this illustration, wire  600  and wire  605  would exchange connections to the system electronics board  302  when the connector is inverted. If all other connections remained the same and the two connections that switched signaled the systems electronics on system card  302  to apply a correct signal to the yoke to start the scan again in the upper left hand corner as viewed from the front, then the combination of inverting the CRT  301  and inverting the yoke connector  309  would have converted a CRT manufactured for installation in one hemisphere to one that is operable in the opposite hemisphere. In the illustration of FIG. 6A the yoke connector  309  is in the normal orientation for a northern hemisphere installation and in FIG. 6B it is in the inverted orientation for a southern hemisphere installation. Indicators  604  and  608  make up installation indicator  319  (shown in FIG. 3) and indicators  606  and  607  make up installation indicator  318  (shown in FIG.  4 ). Label  602  indicates the fourth connector and label  603  indicates the first connector. Labels  602  and  603  are shown to illustrate what happens when the yoke connector  309  is inverted. 
     A representative hardware environment for practicing the present invention is depicted in FIG. 7, which illustrates a typical hardware configuration of data processing system  713  in accordance with the subject invention having central processing unit (CPU)  710 , such as a conventional microprocessor, and a number of other units interconnected via system bus  712 . Data processing system  713  includes random access memory (RAM)  714 , read only memory (ROM)  716 , and input/output (I/O) adapter  718  for connecting peripheral devices such as disk units  720  and tape drives  740  to bus  712 , user interface adapter  722  for connecting keyboard  724 , mouse  726 , and/or other user interface devices such as a touch screen device (not shown) to  20  bus  712 , communication adapter  734  for connecting data processing system  713  to a data processing network, and display adapter  736  for connecting bus  712  to CRT display device  738 . CPU  710  may include other circuitry not shown herein, which will include circuitry commonly found within a microprocessor, e.g., execution unit, bus interface unit, arithmetic logic unit, etc. CPU  710  may also reside on a single integrated circuit. 
     CRT display device  738  may be manufactured according to an embodiment of the present invention and the data processing system of FIG. 7 would be able to have a CRT display device  738  reconfigured in the field for an installation in either the southern or northern hemisphere. All of the system components shown in FIG. 7 may be contained on systems electronics board  302   
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.