Patent Publication Number: US-6703914-B1

Title: Deflection coil having gaps formed subsequent to the winding

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to deflection coils for cathode;ray tubes, and in particular, to an apparatus and a related method of forming gaps in a deflection coil. 
     2. Description of the Related Art 
     Cathode ray tubes (CRTs) are used in display devices to produce images. The basic elements of a CRT are a deflection yoke, one or more electron guns, and a phosphor screen. The deflection yoke converges and deflects electron beams emitted by the electron gun(s). In general, a deflection yoke include two pairs of coils, where the first coil pair (i.e., horizontal coil) deflects the electron beam in the horizontal direction and the second coil pair (i.e., vertical coil) deflects that same electron beam in the vertical direction. 
     One type of a deflection coil used in deflection yokes is a saddle-type deflection coil  100  as shown in FIG.  1 . Typically, a coil-winding die and a winding machine are used to winding a conductive wire into a saddle-shaped coil. The conductive wire generally includes an insulation layer and an adhesive coating disposed about the insulation layer. After the conductive wire has been wound into a proper shape, the coil is heated to melt the adhesive coating and provide adhesive bonding between winding turns of the coil. 
     As the requirements of deflection yokes become more stringent, deflection coils take on more complicated and intricate winding patterns as shown in FIG.  2 . The number, location and shape of the gaps in the deflection coil influence the magnetic field produced by the coil. One conventional method of forming gaps in a deflection coil requires the use of pin insertions in the die during winding. At various times during the winding process, the coil-winding die stops spinning momentarily to enable pins to be inserted in the winding area. After the pins have been inserted, the coil-winding die starts to spin again to wind the wire around the inserted pins. The pin insertions cause the path of the winding to change. By changing the path of the winding, gaps are formed between a previous winding path and a subsequent winding path. The timing of the pin insertions and the location of the pin inserting mechanisms incorporated into the coil-winding die dictate the location of gaps formed in a deflection coil. Gaps in a deflection coil produced by inserting pin mechanisms during a winding process are usually of a triangular or curved triangular shape, as shown in FIG.  2 . 
     Such conventional method of forming gaps in a deflection coil during a winding process suffers from various disadvantages. For example, because pin inserting mechanisms are permanently incorporated into the coil-winding die and the winding machine, the pin inserting mechanisms increase the complexity of the die design and increase the cost of designing and producing the die and winding machine. Moreover, because pins are inserted during winding of the deflection coil, the coil-winding die must slow down or stop spinning momentarily to enable pins to be inserted during a winding process. As a result the winding process is slowed down and the production output rate is reduced. Furthermore, the shape, location, and number of gaps in the deflection coils are restricted to those already machined into the coil-winding die. In other words, if a design engineer decides to change the location of one or more gaps in a deflection coil, this would require making major design changes in the winding machine and the coil-winding die. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the present invention, a method is provided for forming gaps into a saddle-shaped deflection coil subsequent to a winding process. The method includes winding a conductive wire into a saddle-shaped deflection coil using a winding machine and bonding the saddle-shaped deflection coil to provide adhesive bonding between winding turns of the coil while the coil remains in the winding machine. Then, the deflection coil is removed from the winding machine and heat is applied to the deflection coil after the deflection coil has been removed from the winding machine to a temperature above a first temperature and below a second temperature. Gaps are formed in the deflection coil subsequent to the winding process while the temperature of the coil is between the first and second temperatures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic perspective view of a conventional saddle-type deflection coil. 
     FIG. 2 is a diagrammatic perspective view of another conventional saddle-type deflection coil having a number of gaps formed during a winding process. 
     FIG. 3 is a diagrammatic perspective view of a saddle-type deflection coil constructed in accordance with one embodiment of the invention. 
     FIG. 4 is a diagrammatic perspective view of an apparatus for inducing gaps into a deflection coil according to one embodiment of the invention. 
     FIG. 5 is a diagrammatic perspective view of the apparatus of FIG. 4 with some components removed. 
     FIG. 6 is a flowchart of operations of forming a saddle-type deflection coil according to one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 3 depicts one example of a saddle-type deflection coil  300  constructed according to the invention. The illustrated deflection coil  300  comprises a front flare portion  302 , a rear flare portion  304 , a neck region  306  and a central opening  308  and a number gaps  310 - 316  formed in winding regions  318  and  320  between the front and rear flare portions. The deflection coil  300  may be formed by using a winding machine and a coil-winding die to wrap a wire into a saddle shape. Then, gaps are formed in the windings subsequent to the winding process in accordance with one aspect of the invention. In accordance with another aspect of the invention, instruments having shaped ends are used to create gaps of various sizes and shapes along various locations in the coil windings. The number, location and shape of gaps in the deflection coil are selected by a design engineer to obtain a desired magnetic field. 
     FIG. 4 depicts an apparatus  400  for forming gaps into a deflection coil  410  according to one embodiment of the invention. The apparatus includes a base  402  which may be any structure that provides a stable surface from which to support and work on a deflection coil  410 . Mounted to the base  402  are a vertical support  404 , a coil support  406  and a coil clamp  408 . The coil support  406  is configured to support and restrict the deflection coil  410  from moving laterally along the base  402 . In the illustrated embodiment, the coil support  406  is of a semi-cylindrical configuration to support the neck region of the deflection coil  410 . However, the coil support  406  can be of any other configuration capable of restricting the deflection coil  410  from moving laterally along the base  402 . The deflection coil  410  may be secured to the base  402  by placing the coil clamp  408  over the neck region of the coil and fastening bolts  412  through the coil clamp  408  into the base  402 . 
     A vertical clamp  414  is mounted on the vertical support  404 . The vertical clamp  414  includes an extended lip that may be lowered over a front flare portion  416  of the coil  410  so as to sandwich the front flare portion between the vertical clamp  414  and vertical support  404 . The front flare portion  416  of the deflection coil  410  can be secured to the apparatus  400  by tightening support pins  418 ,  420  into the vertical support  404  to wedge the front flare portion  416  between the extended lip and the vertical support  404 . 
     As shown in FIG. 4, a gap-forming instrument  422  is used to facilitate formation of a gap in coil windings. In the illustrated embodiment, the instrument  422  includes an elongated rod  424  having a handle  426  on one end and a gap-forming portion  428  on the other end. The gap-forming portion  428  of the instrument has a cross sectional profile that influences the shape of gap placed into the coil  410 . The cross sectional profile of the gap-forming portion may be any desired shape to provide a desired gap shape. For example, the cross sectional profile of the gap-forming portion may be resemble one of a circle, a rectangle, a diamond, an oval, a long slit or any other suitable shape. By enabling a design engineer to select from different shapes of gaps to be created in a deflection coil, this provides the design engineer with greater flexibility in achieving an optimal magnetic field provided by the deflection coil. 
     To aid in parting of coil windings, the coil is heated prior to the insertion of the gap-forming instrument to a temperature at which the bonding or adhesive material disposed about the conductive wire starts to melt but not so high that the heat starts to damage the insulation layer of the wire. In one implementation, the gap-forming portion  428  has a tapered rounded end to facilitate insertion of the instrument  422  in the coil windings without damaging the insulation layer of the wire. 
     To help guide the gap-forming portion  428  of the instrument  422  into a particular location in the windings, an instrument guide assembly  430  is incorporated in the apparatus  400 . The instrument guide assembly  430  comprises an instrument guide  432  and a guide holder  434 . In the illustrated embodiment, the guide holder  434  includes an L-shaped member movably attached to the base  402  to permit the entire guide holder  434  to slide over the top surface of the base and rotate with respect to the base. The guide holder  434  includes one or more fastener (not shown) to secure the holder  434  to the base  402  in a selected position. The probe guide  432  includes an elongated element pivotally coupled to the guide holder  434 . The probe guide  432  has a bore to enable the instrument  422  to move longitudinally with respect to the bore. The probe guide  432  also includes a fastener (not shown) to secure the probe guide at a selected pivotal angle with respect to the guide holder  434 . In this regard, the instrument guide assembly  430  is useful in remembering the location of a gap during subsequent gap forming process. 
     While only one instrument, one instrument guide and one guide holder are shown for the illustrated embodiment, it will be appreciated by those skilled in the art that the apparatus  400  can accommodate a number of instrument guide assemblies to systematically form multiple gaps in the deflection coil to achieve any complex and intricate coil pattern. 
     The illustrated apparatus  400  also includes a vice holder  436  attached to bottom of base  402 . The vice holder  436  may be an extension of base  402  that may be disposed between two jaws that, when closed, securely hold the base  402  in position. 
     FIG. 5 depicts the apparatus  400  of FIG. 4 with some components removed from the illustration for clarity. As noted above, the shape of gap  438  may be influenced by the cross sectional profile of a gap-forming portion  428  of a gap-forming instrument  422 . In the illustration shown, the gap  438  defines a trapezoid shape produced with an instrument  422  having a trapezoid shape gap-forming portion  428 . 
     By forming at least some or all of the gaps in the coil windings subsequent to the winding process, a number of advantages are provided by the present invention. For example, because the number of gaps formed during a coil winding process using pin insertions is significantly reduced or totally eliminated, a coil winding machine is able to complete its winding task in a much quicker fashion. In addition, the cost of developing a coil-winding die and winding machine is significantly reduced, since the present invention eliminates or minimizes the need to have complicated pin insertion mechanisms as part of the coil-winding die and winding machine. Moreover, the present invention allows for a variation in hole location and number of holes as part of designing process during a deflection coil designing stage. Furthermore, unlike conventional techniques, the present invention advantageously permits introduction of gaps in the coil windings of a wide variety of shapes and sizes, such as long slits and oval holes as shown in FIG.  3 . 
     FIG. 6 depicts operations of forming a saddle-type deflection coil according to one embodiment of the invention. In block  600 , a winding machine and a coil-winding die are used to form a saddle-shaped deflection coil. Then in block  605 , the deflection coil is removed from the winding machine and coil-winding die. Then in block  610 , the deflection coil is secured to a gap-forming apparatus  400  by placing the coil over a coil support  406  and with the front flare portion of the coil touching a vertical support  404 . By using a combination of a coil clamp  408  and a vertical clamp  414 , the coil may be securely supported by the apparatus. Specifically, the coil clamp  408  is used to secure the neck region of the coil to the base  402  and the vertical clamp  414  is used to secure the front flare portion to the vertical support  404 . 
     To facilitate separation of the coil windings upon insertion of the instrument, heat is applied to raise the temperature of the coil to soften or to melt the adhesive material bonding the coil windings together. Heat can be applied to the coil either before the coil is secured to the gap forming apparatus  400  or after the coil has been secured to the apparatus  400 . The heating of the coil can be accomplished by directing heat from an external source such as a hot air gun or by placing the coil in an oven. Alternatively, electrical power can be applied to the coil to provide heat generated by the electrical power. In one embodiment, the coil is heated to a temperature above the softening point or melting point of the adhesive coating but below a temperature that would damage insulation layer of the conductive wire. In one implementation, the coil is heated to a temperature which may range from about 130 to 160 degrees Celsius, and preferably about 150 degrees Celsius. 
     After the coil has been heated to a proper temperature range, the gap-forming portion  428  of the instrument  422  is inserted in the coil windings, in block  620 , to form a gap. This can be accomplished by moving the instrument through the bore of the guide  432 . Then in block  625  the coil is allowed to cool to a rigid construction before the coil is removed from the apparatus in block  630 . 
     In one embodiment, the gap-forming portion  428  of the instrument  422  is manually inserted into the coil windings using the apparatus  400  described above. In an alternative embodiment, the process of creating gaps in a deflection coil is automated by a machine that controls insertion of a number of gap-forming instruments. The machine may be configured to create all gaps in the coil at the same time or may be configured to create gaps in certain order. 
     When desired, the location of the gap formed in the coil winding can be changed by simply adjusting the orientation of the instrument  422  with respect to the coil supported by the apparatus  400 . This may involve sliding the guide holder  434  over the top surface of the base  402 , adjusting the vertical pivot angle of the instrument  422  by rotating the probe guide  432  with respect to the guide holder  434 , and adjusting the horizontal pivot angle of the instrument  422  by rotating the guide holder  434  with respect to the base  402 . Once the instrument is in a desired position, the guide holder  434  and instrument guide  432  is fixed in place by tightening fasteners. By using the instrument guide  432  and the guide holder  434  to maintain the instrument  422  in certain orientation with respect to the deflection coil, the insertion of the instrument head (e.g., gap-forming portion) into a precise location in the windings can be subsequently repeated. 
     While the foregoing embodiments of the invention have been described and shown; it is understood that variations and modifications, such as those suggested and others within the spirit and scope of the invention, may occur to those skilled in the art to which the invention pertains. The scope of the present invention accordingly is to be defined as set forth in the appended claims.