Abstract:
Funnel in a CRT including a body part welded to a panel, a cone part connected to the body part having a deflection yoke fitted thereto actually, and a neck part connected to the cone part having an electron gun sealed therein, wherein the cone part is formed such that ΔY/ΔX={YD−(DD*sin θ 2 )}/{XD−(DD*cos θ 2 )} is greater than 4, where DD denotes a diagonal length, XD denotes a long axis length, YD denotes a short axis length, and θ 2  denotes a diagonal angle between the long axis and the short axis.

Description:
[0001]    This application claims the benefit of the Korean Application Nos. P2001-58646 filed on Nov. 21, 2001, and P2002-2283 filed on Jan. 15, 2002, which are hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a cathode ray tube (CRT), and more particularly, to a funnel in a CRT, which can secure an adequate vacuum strength, and improve a deflection sensitivity, one of deflection yoke efficiencies, and a wedge insert ability.  
           [0004]    2. Background of the Related Art  
           [0005]    A related art CRT will be explained, with reference to FIGS. 1 and 2.  
           [0006]    The related art CRT is provided with a panel  10  and a funnel  20  welded to rear of the panel  10  with frit glass. The panel  10  has flat or curved outside surface and inside surface, and the funnel  20  is a cone formed.  
           [0007]    In the meantime, there is an electron gun  19  sealed in a rear part of the funnel  20  for emitting an electron beam, and there is a shadow mask  12  fitted with a gap to the inside surface of the panel  10  having a radius of curvature similar to the radius of curvature of the inside of the panel.  
           [0008]    The shadow mask  12  is welded to the frame  14 , and the frame  14  is fixed to stud pins  16  fixed to the panel  10  through springs  15 . There is an inner shield  17  fixed to the frame  14  by fixing springs  13  for shielding an external magnetic field.  
           [0009]    The funnel will be explained with reference to FIGS.  1 - 3 .  
           [0010]    The funnel  20  is welded to the panel  10 , to form a seal line  31 , and a height from the seal line  31  to an outside surface of the panel  10  is a height (OAH) of the panel  10 .  
           [0011]    The funnel  20  is provided with a body part  21 , a cone part  22 , and a neck part  23 . A connection part of the body part  21  to the cone part  22  is called as a TOR (Top Of Round)  33 , and a connection part of the cone part  22  to the neck part  23  is called as a neck seal  37 . There is a RL (Reference Line)  35 , a center of the electron beam deflection, in the cone part  22 , and there is a deflection yoke  18  fitted to the cone part  22  for deflection of the electron beam.  
           [0012]    Since the cone part  22  in the funnel  20  is relatively thin compared to other parts, it is required that the cone part  22  is made to reinforce a vacuum strength. Therefore, as shown in FIG. 3, the cone part  22  has a circular section for uniform distribution of stress.  
           [0013]    In the meantime, the electron beam from the electron gun  19  is made to make a curvilinear motion in a screen direction by the deflection yoke  18  in the cone part  22 . Of a long side direction, a short side direction, and a diagonal direction of a rectangular screen, the diagonal direction is the farthest from a center of the screen. Accordingly, the electron beam deflected to the diagonal direction is required to make a curvilinear motion that is curved the most. Since the long side direction and the short side direction have shorter distances to the screen, the electron beams in the long side direction or the short side direction makes a curvilinear motion that is curved less than the electron beam in the diagonal direction.  
           [0014]    When the electron beam hits the cone part  22 , a shadow phenomenon is occurred, in which the electron beam is shaded by an inside surface of cone part  22 , so as not to be shown on the screen. Therefore, the cone part  22  has an outside form designed to have a curvature similar to an electron beam path in the diagonal direction.  
           [0015]    In the meantime, in order to form a rectangular screen, it is required that the path  22   b  of the electron beam passing through the cone part  22  also has a form close to rectangle, resulting to occur invalid spaces  22   a  in the long side direction and the short side direction through which no electron beam passes.  
           [0016]    Disadvantages of the related art CRT, a CRT having a circular cone part  22  section, will be explained.  
           [0017]    First, the circular cone part  22  also requires a circular deflection yoke  18 . This causes distances from the deflection yoke  18  to the electron beam both in the long side direction and the short side direction far, leading to make a force of a magnetic field of the deflection yoke  18  to the electron beam weak. Therefore, it is required to apply a strong current to the deflection yoke  18  for forming a strong magnetic field, to require much power consumption.  
           [0018]    Second, in the invalid spaces  22   a  in the long side direction and the short side direction, degrees of close contact of the deflection yoke  18  with the electron beam are poor, to drop deflection sensitivity of the electron beam even if the identical current is applied to the deflection yoke  18 .  
           [0019]    In the meantime, as environment friendly, and low powered electric appliances are required currently, improvement of the deflection yoke, that has much power consumption, is essential even in the CRT. However, for fabrication of a low powered deflection yoke, improvement of a form of the cone part in the funnel is required beforehand. Eventually, a CRT having a section similar to the deflection path of the electron beam is suggested. However, the non-circular cone part requires taking a vacuum strength thereof weaker than the circular cone part into account. Besides, the non-circular cone part requires taking the deflection sensitivity, and the wedge insert ability into account. That is, the CRT, particularly, the cone part of the funnel, is required to take the vacuum strength, the deflection sensitivity, the wedge insert ability into account.  
         SUMMARY OF THE INVENTION  
         [0020]    Accordingly, the present invention is directed to a funnel in a CRT that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.  
           [0021]    An object of the present invention is to provide a funnel in a CRT which permits to secure an adequate vacuum strength.  
           [0022]    Another object of the present invention is to provide a funnel in a CRT which has an excellent deflection sensitivity and a wedge insert ability.  
           [0023]    Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.  
           [0024]    To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the funnel in a CRT includes a body part welded to a panel, a cone part connected to the body part having a deflection yoke fitted thereto actually, and a neck part connected to the cone part having an electron gun sealed therein, wherein the cone part is formed such that ΔY/ΔX={YD−(DD*sin θ 2 )}/{XD−(DD*cos θ 2 )} is greater than 4, where DD denotes a diagonal length, XD denotes a long axis length, YD denotes a short axis length, and θ 2  denotes a diagonal angle between the long axis and the short axis.  
           [0025]    Preferably, the ΔY/ΔX=4.0-5.5, and more preferably, the ΔY/ΔX=4.0-5.0.  
           [0026]    Preferably, a part starting from a part the body part and the cone part are connected to a distance toward the cone part is formed to satisfy the range of the ΔY/ΔX. Preferably, the distance is approx. 20 mm.  
           [0027]    The diagonal angle is the same with an angle the long axis and the short axis of the screen of the CRT form.  
           [0028]    Centers of radiuses of curvatures of a corner of the cone part are on the same line.  
           [0029]    In another aspect of the present invention, there is provided a funnel in a CRT including a body part welded to a panel, a cone part connected to the body part having a deflection yoke fitted thereto actually, and a neck part connected to the cone part having an electron gun sealed therein, wherein the funnel is formed such that c/(a+d) is in a range of 0.26-0.37, where ‘c’ denotes a length of the cone part, ‘d’ denotes a length of the body part. ‘a’ denotes a length from a deflection center line of an electron beam to a front end of the cone part in the cone part, and ‘b’ denotes a length from a deflection center line of an electron beam to a rear end of the cone part in the cone part. Preferably, the c/(a+d) is in a range of 0.30-0.35. Preferably, the funnel is formed such that a/b is in a range of 1.00-1.20.  
           [0030]    Thus, the CRT with a non-circular cone part of the present invention can provide good vacuum strength, deflection sensitivity, and wedge insert ability.  
           [0031]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention:  
         [0033]    In the drawings:  
         [0034]    [0034]FIG. 1 illustrates a side view of a funnel of a related art CRT, with a partial cut away view;  
         [0035]    [0035]FIG. 2 illustrates a plan view of FIG. 1;  
         [0036]    [0036]FIG. 3 illustrates a section showing a circular cone part in a funnel of a CRT;  
         [0037]    [0037]FIG. 4 illustrates a perspective view of a CRT with a non-circular cone part;  
         [0038]    [0038]FIG. 5 illustrates a section showing a non-circular cone part in a funnel of a CRT;  
         [0039]    [0039]FIG. 6 illustrates stresses occurred in a non-circular cone part in a funnel of a CRT, schematically;  
         [0040]    [0040]FIG. 7 illustrates a graph showing vacuum strengths varied with forms of a cone part in a CRT with a non-circular cone part;  
         [0041]    [0041]FIG. 8 illustrates a graph showing deflection sensitivities varied with forms of a cone part in a CRT with a non-circular cone part;  
         [0042]    [0042]FIG. 9 explains a state a deflection yoke is fixed to a funnel by a wedge, schematically;  
         [0043]    [0043]FIG. 10 illustrates a graph showing an insert ability of a wedge varied with forms of a cone part in a CRT with a non-circular cone part;  
         [0044]    [0044]FIG. 11 illustrates a section of a cone part in a funnel of a CRT in accordance with a preferred embodiment of the present invention;  
         [0045]    [0045]FIG. 12 illustrates a graph showing vacuum strengths varied with lengths of various parts of the funnel of a CRT in accordance with another preferred embodiment of the present invention;  
         [0046]    [0046]FIG. 13 illustrates a graph showing wedge insert abilities varied with lengths of various parts of the funnel of a CRT in accordance with another preferred embodiment of the present invention; and  
         [0047]    [0047]FIG. 14 illustrates a graph showing BSN varied with lengths of various parts of the funnel of a CRT in accordance with another preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0048]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings FIGS.  4 - 6 .  
         [0049]    Alike the related art, a funnel in a CRT in accordance with a preferred embodiment of the present invention also includes a body part  21 , a cone part  22 , and a neck part. The body part  21  and the neck part may have the same forms with the related art, except the cone part  22  that is non-circular. That is, the cone part  22  is non-circular with different long sides and short sides similar to a deflection path of the electron beam.  
         [0050]    In the meantime, in comparison to the funnel with the circular cone part, the funnel with the non-circular cone part is required that the non-circular cone part in the funnel  20  is optimized, because the non-circular cone part  22  has a vacuum strength weaker than the circular cone part, and the shade phenomenon is prevented, in which a shade is occurred on the screen as the electron beam hits an inside surface of the cone part  22 . Moreover, it is required that a form of the cone part  22  is determined in view of a wedge insert ability, and a deflection sensitivity. That is, it is required that the cone part  22  of the funnel  20  is determined in view of securing an adequate vacuum strength, prevention of the shade phenomenon, a good wedge insert ability, and a good deflection sensitivity.  
         [0051]    In the meantime, the form of the cone part  22  of the funnel  20  is fixed by a length of the cone part  22  and a sectional form of the cone part  22 . As shown in FIG. 5, the form of the non-circular cone part  22  is fixed by a length from a center to a long side, (hereafter called as a “long axis length”) XD, a length from a center to a short side, (hereafter called as a “short axis length”) YD, a length from a center to a corner, (hereafter called as a “diagonal length”) DD, and an angle between a “diagonal angle”) θ 2 , and the like.  
         [0052]    The form of the cone part of the present invention will be explained in detail.  
         [0053]    Once a deflection angle θ 1 , formed by a line connecting a reference line  35  of the funnel  20  and a diagonal edge of an effective surface of the panel and a CRT axis, is fixed, a length of the CRT is fixed.  
         [0054]    The fixed CRT length is allocated into a length of the panel  10  and a length of the funnel  20  appropriately, and the funnel  20  length is allocated into a body part  21  length, a cone part  22  length, and a neck part length appropriately.  
         [0055]    In the division of the length, it is required that the followings are taken into account. At first, it is very important that effective distribution and reduction of the vacuum stresses on the seal line  31  and the TOR  33  are very important. Particularly, in the case of the non-circular cone part  22 , the distribution and reduction of the vacuum stresses on the TOR  33  are more important, because the TOR  33 , a part the radius of curvature is the smallest, is weak to stress, more particularly, to the non-circular cone part  22 .  
         [0056]    Referring to FIG. 6, a corner  226  of the non-circular cone part  22  has a tension, and the long side part  222  and the short side part  224  have compressive stress. Moreover, it can be known from a vacuum strength analysis that there is a tensile stress at a part (a fore end of the short side)  230  the short side  224  of the neck part  23  and the body part  21  are in contact. Therefore, it is preferable that dimensions of various parts are fixed such that the stresses occurred at the corner  226  of the cone part  22  and the fore end of the short side  230  are reduced.  
         [0057]    The inventor found that, though forms of the electron beam passing the long side part and the short side part of the cone part  22  are concave actually (see FIG. 3), concave the long side part and the short side part of the cone part  22  is not favorable for the vacuum strength.  
         [0058]    Because, too short a long axis length XD and too short a short axis length YD in comparison to the diagonal length DD increase a tensile stress at the corner  226  sharply, such that the vacuum strength of the CRT is not adequate, or susceptible to breakage from an external impact.  
         [0059]    The inventor found that relations of the diagonal length DD, the long axis length XD, and the short axis length YD appropriate in view of the vacuum strength are obtainable by the following equation. 
         Δ Y/ΔX={YD− ( DD *sin θ 2 )}/{ XD− ( DD *cos θ 2 )} 
         [0060]    [0060]FIG. 7 illustrates a graph showing vacuum strengths varied with ΔY/ΔX in a CRT with a non-circular cone part. When ΔY/ΔX is 1, 2, 3, 4, 5, or 6, the stress at the short axis fore end  230  is 7.2, 6.5, 5.2, 4.5, 4.4, or 4.2 MPa, and the stress at the corner  226  is 4.8, 4.6, 4.4,4.2, 4.1, or 4.0 MPa.  
         [0061]    As can be noted in FIG. 7, since the short axis length YD increases when the ΔY/ΔX increases, the tensile strength at the short axis fore end  230  and the corner  226  is reduced. Particularly, when the ΔY/ΔX is greater than 4, the tensile stress at the short axis fore end  230  and the corner  226  is below a certain value. Therefore, it is preferable that the ΔY/ΔX is greater than 4 in view of the vacuum strength.  
         [0062]    In the meantime, when the ΔY/ΔX is greater than 4, the reduction of the tensile stress at the short axis fore end  230  is slow. When the ΔY/ΔX is great, the short axis length YD is also great, to drop a horizontal direction deflection sensitivity. Therefore, it is preferable that a range of the ΔY/ΔX is limited in view of the horizontal direction defection sensitivity.  
         [0063]    [0063]FIG. 8 illustrates a graph showing deflection sensitivities varied with the ΔY/ΔX in a CRT with a non-circular cone part. When the ΔY/ΔX is 1, 2, 3, 4, 5, or 6, the deflection sensitivity is 28.5, 28.7, 28.9, 29.1, 29.5, 32.2, mHA 2 , considering current situation in which power consumption of a large sized appliance is regulated, it is preferable that the horizontal deflection sensitivity is below  30 . According to this, it is preferable that the ΔY/ΔX is below 5.5.  
         [0064]    It is more preferable that the ΔY/ΔX is below 5 because the horizontal deflection sensitivity increases sharply if the ΔY/ΔX is greater than 5. According to this, it is preferable that the ΔY/ΔX is 4-5.5, and more preferably 4-5.0.  
         [0065]    In the meantime, referring to FIG. 9, there is a wedge  40  inserted between the short side of the cone part  22  and the deflection yoke  18  for fitting the deflection yoke  18 . However, because the non-circular cone part  22  has a sharp change of a curvature at the body part  21  and the cone part  22  in comparison to the circular cone part  22 , insertion of the wedge  40  may be difficult, or contact of the wedge  40  may be poor. Therefore, it is preferable that a range of the ΔY/ΔX is fixed taking insertion of the wedge into account. It is preferable that the short axis length YD is made long, to reduce a sharp slope in a part connecting the cone part  22  and the body part  21  to the maximum, for easy insertion of the wedge.  
         [0066]    [0066]FIG. 10 illustrates a graph showing an insert ability of a wedge with reference to a short side at which the body part  21  and the cone part  22  are met. When the ΔY/ΔX is 1, 2, 3, 4, 5, or 6, a gap between the wedge and the funnel is 0.8, 0.7, 0.6, 0.3, 0.23, or 0.2 mm.  
         [0067]    As noted in FIG. 10, a degree ‘t’ of contact of the wedge changes sharply at 3-4 ΔY/ΔX and the degree ‘t’ of contact of the wedge is good when the ΔY/ΔX is greater than 4. Therefore, it is preferable that the ΔY/ΔX is greater than 4.  
         [0068]    In general, an inserted length of the wedge is 20 mm. Therefore, it is particularly required that the wedge insert ability is good to a point 20 mm from TOR. Moreover, a length ‘a’ from the electron beam deflection center to a fore end of the cone part has an influence to the deflection sensitivity less than a length ‘b’ from the electron beam deflection center to a rear end of the cone part. Therefore, it is preferable that the ΔY/ΔX is greater than 4 at a part starting from TOR up to approx. 20 mm in a neck  23  direction.  
         [0069]    [0069]FIG. 11 illustrates a section of a cone part  22  perpendicular to the axis of the CRT, wherein a plurality of sections along an axis direction of the CRT are shown. As shown in FIGS. 1 and 11, it is preferable that centers  242   a ,  244   a , and  246   a  of radiuses of curvature at the corner in the plurality of cone part sections  242 ,  244 , and  246  in the axis direction are on the same line. In other words, it is preferable that diagonal angles θ 2  of the plurality of cone part sections  242 ,  244 , and  246  are the same, otherwise an outside surface of the corner of the cone part  22  will be non-linear, to cause a stress concentration.  
         [0070]    Moreover, it is required that the diagonal angle θ 2  of the cone part  22  is the same with the diagonal angle (an angle between the long axis and the short axis of the screen effective surface) of the effective surface of the screen, to keep a linearity of the corner continuous from the cone part  22  and the body part  21  of the funnel  20  to the panel, for prevention of the stress concentration caused by a non-linearity.  
         [0071]    In the meantime, the foregoing embodiment explains a funnel of a CRT of the present invention in view of a form of a cone part section. A funnel of a CRT in accordance with a preferred embodiment of the present invention will be explained in view of lengths of the body part and cone part of the funnel, hereafter.  
         [0072]    Referring to FIG. 2, a distance from TOR  33  to the neck seal  37  is a length ‘c’ of the cone part, and a distance from the seal line  31  to TOR  33  is a length ‘d’ of the body part. The cone part length ‘c’ may be allocated into a distance ‘a’ from the reference line  35  to TOR  33 , and a distance ‘b’ from the reference line  35  to the neck seal  37 .  
         [0073]    It is important that a length ‘d’ of the body part of the funnel  20  and a height OAH of the panel  10  are allocated, appropriately. Though the panel  10  is not favorable in view of the vacuum strength in comparison to the funnel  20  due to a straight section of the panel  10 , the panel  10  can be reinforced by means of thickness. However, because the funnel  20  is, though favorable in view of the vacuum strength as the funnel  20  is curved, not favorable due to thickness, it is required that the funnel  20  is designed, appropriately. In the funnel  20  with the non-circular cone part, a part a long side of the cone part  22  and the body part  21  meet, i.e., TOR part is weak as the radius of curvature is the smallest. Therefore, an appropriate allocation of lengths of the body part  21  and the cone part  22  is required such that strength of the TOR part is adequate.  
         [0074]    [0074]FIG. 12 illustrates a graph showing stresses at TOR varied with c/(a+d), referring to which relations of a length (a+d) from the reference line  35  to the seal line  31  and a length ‘c’ of the cone part will be explained. When c/(a+d) is 0.20, 0.25, 0.30, 0.35, 0.40, or 0.45, the stress is 7.5, 7.2, 5.4, 5.6, 6.8, 7.3 MPa, respectively.  
         [0075]    As can be noted in FIG. 12, since the stress at TOR is approx. 6 MPa if 0.26&lt;c/(a+d)&lt;0.37, the funnel  20  is safe in view of strength.  
         [0076]    Moreover, as the c/(a+d) becomes the greater, though the stress becomes the smaller for some extent, the stress becomes the greater again. Because the greater the c/(a+d), the smaller the length ‘d’ of the body part, the stress at the body part  21  becomes the greater. That is, the stress is the smallest when the c/(a+d) is within a range of 0.26-0.37.  
         [0077]    At the end, considering strength of the CRT, it is preferable that the c/(a+d) is within a range of 0.26-0.37, and more preferably within a range of 0.30-0.35.  
         [0078]    Meanwhile, as explained, it is required that the shade phenomenon is prevented. The shade phenomenon is related to a BSN (Beam Strike Neck). The BSN is a distance the deflection yoke is moved from a point the deflection yoke is brought into contact in a screen direction toward a neck direction until no electron beam hits the screen such that the electron beam can not make the fluorescent film luminescent.  
         [0079]    Referring to FIG. 14, for preventing the shade phenomenon, it is preferable that the BSN, which becomes the smaller as the c/(a+d) is the greater, is greater than 4.5 mm. Accordingly, it is preferable that the c/(a+d) is below approx. 0.35.  
         [0080]    In the meantime, the non-circular cone part has difficulty in inserting a device for fitting the deflection yoke in comparison to the circular cone part due to sharp change of curvature in the body part  21  and the cone part  22  (see FIG. 9). Therefore, it is preferable that lengths of different parts of the funnel are fixed taking, not only the strength, but also the wedge insert ability into account.  
         [0081]    The deflection yoke is designed taking the reference line  35  of the cone part  22  as a mechanical center. Therefore, a deflection power is fixed by the length ‘b’ from the reference line to the neck seal, and the wedge insert ability is fixed by the length ‘a’ from the reference line to TOR.  
         [0082]    Since the longer the length ‘a’ from the reference line to TOR, the better the contact between the wedge and the cone part, the longer the length ‘a’, the deflection yoke can be fixed to the cone part  22  the more stably. Moreover, as a size of the deflection yoke is limited, when the length ‘a’ from the reference line to TOR is small, the deflection yoke can not deflect the electron beam enough to display a desired picture size even if the same current is applied, thereby deteriorating a product quality. However, if the length ‘a’ from the reference line to TOR is great excessively, the length ‘c’ of the cone part may be increased, to cause the shade phenomenon.  
         [0083]    Referring to FIG. 13, when a/b is 0.80, 0.90, 1.10, 1.10, 1.20, 1.30, the degree ‘t’ of contact of the wedge and the cone part is 0.5, 0.35, 0.31, 0.22, 0.08, 0.0, respectively. As explained, considering the wedge insert ability, the deflection yoke efficiency, the shade phenomenon, and the like, it is preferable that the degree ‘t’ of contact of the wedge and the cone part is 0.1-0.3. Therefore, it is preferable that a/b is in a range of 1.0-1.2.  
         [0084]    In the meantime, it is preferable that the deflection angle θ 1  is in a range of 100°-120°. Because if the deflection angle is smaller than 100°, the foregoing formula are not satisfied owing to the small stress at the cone part, and if the deflection angle is greater than 120°, the sensitivity can not be satisfied.  
         [0085]    As has been explained, the funnel in a CRT of the present invention has the following advantages.  
         [0086]    First, by allocating lengths of different parts of the cone part, an adequate vacuum strength can be secured, and a good deflection sensitivity can be obtained.  
         [0087]    Second, the good wedge insert ability provided the present invention permits a stable fitting of the deflection yoke, and reduction of a quality spread of the CRTs.  
         [0088]    It will be apparent to those skilled in the art that various modifications and variations can be made in the funnel in a CRT of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.