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(11) | EP 0 371 618 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and device for suppression of leakage of magnetic flux in display apparatus |
| (57) A device for suppression of leakage of the magnetic flux in a cathode ray tube display
apparatus which comprises at least a cathode ray tube having a face plate and horizontal
beam deflection circuit generating the leakage, the deflection circuit comprising
a pair of upper and lower coils each of which has a bend-up section producing a first
magnetic field which deflects an electron beam of the cathode ray tube, and a second
magnetic field produced as the leakage the first and second magnetic field forming
a boundary plane therebetween, so that two boundary planes are formed of said upper
and lowser deflection coils, respectively, said device comprising; a pair of conductors
each of which has a main portion and a lead portion connected to the main portion,
said main portion of the pair of conductors being disposed approximately within said
boundary plane and along approximately top and bottom rims of the face plate, respectively,
said lead portion of the pair of conductors disposed along a side wall of a funnel
of the cathode ray tube in such a form that one end of the lead portion is bent along
a side rim of the face plate to couple with said main portion and another end of the
lead portion extends toward a rear of the horizontal beam deflector, the pair of conductors
being driven with a current proportional to a horizontal deflection current flowing
through the horizontal beam deflectors. |
BACKGROUND OF THE INVENTION
[0001] This invention relates to a method and a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, which is adapted to suppress leakage magnetic flux generated from the deflection yoke.
[0002] There are many display apparatuses of the type utilizing a magnetic field generated from the deflection coil, etc. as the method of deflecting an electron beam. For this reason, in the display apparatus of this kind, a magnetic flux from the deflection coil, etc. leaks out from the surrounding of the cathode ray tube. Such an unnecessary electromagnetic ray may exert bad or adverse influence on the operation of electronic equipment in the vicinity thereof.
[0003] Recently, studies on the influence exerted on the human being and animals of the magnetic field have been conducted. For example, a magnetic field from the cathode ray tube is considered to be also harmful. In view of this, the research institution of SSI (Statens Stralskydds Institut) in Sweden has announced that, in regard to the super low frequency magnetic field, with the point within 15 cm from the center of the display surface of the cathode ray tube being as a center, as recommended values of the change rate, i.e., time-derivative (dB/dt) of a magnetic flux density at 80 positions on the spherical body having a radius of 65 cm and the strength of a magnetic flux density in the frequency band of 10 to 300 KHz, the change rate of the maximum magnetic field is set to a value lower than 25 mT (mili tesla), and the strength of the maximum magnetic flux density is set to a value lower than 50 nT (nano tesla).
[0004] In the above-described description, T represents Tesla which is the unit of the strength of a magnetic field, and 1 T = 10000 Gauss and 1 mT = 10 Gauss.
[0005] For allowing the change rate of a maximum magnetic field as the entirety of the display apparatus to satisfy the value lower than 25 mT/sec, it is indicated by the display manufacturers and sellers (e.g., IBM, etc.) that the change rate of the maximum magnetic field should be a value lower than 15 mT/sec as the standard requirement in the state of the cathode ray tube to which the deflection yoke is attached, i.e., the cathode ray tube display apparatus what is called an ITC (Integrated Tube Component).
[0006] For conventional technologies for suppression of leakage magnetic flux from the deflection yoke on the display surface of the cathode ray tube, there were two prior arts described below.
[0007] The first prior art is the technology shown in FiGS. 1A to 1 C. This has been already filed at the Japanese Patent Office by N.V. Philips Gloellam- penfabrieken (Japanese Patent Application Laid Open No. 223952/1987).
[0008] Namely, FIGS. 1 A to 1 C show examples where an electric wire 1 is electrically coupled to the deflection unit and the electric wire 1 is disposed on a face-plate 2, respectively. In these figures, reference numerals 3a and 3b represent ordinary connection terminals of the deflection unit, respectively.
[0009] In the case of the example of Fig. 4A (system I), the electric wire 1 is connected in series with deflection coils 4a and 4b, and two electric wire sections 1 a and 1 b in a horizontal direction of the electric wire are directly attached to the upper and lower side edge portions of the face-plate 2, or are attached in a manner that they are extremely close thereto, respectively.
[0010] In the case of the example of FIG. 1 C (system II), for compensating a stray magnetic flux of individual deflection coils, a deflection coil 4a is coupled in series with the upper side electric wire section 1 a in a horizontal direction, and a deflection coil 4b is coupled in series with the lower side electric wire section 1 b in the horizontal direction.
[0011] In the case of the example of FIG. 1 B (system III), a control current source 5 is disposed between the deflection coils 4a and 4b and the electric wire sections 1 a and 1b. In this case, the electric wire sections are wound a plurality of times, i.e., as a plurality of loops at the upper and lower side edge portions of the face-plate 2.
[0012] The second technology has been proposed by the same assignee as one of this invention. (Japanese Patent Application No. 156411/1987, EPC Application No. 89306338.8).
[0013] Namely, the example shown in FIG. 2 (system IV) is as follows. In this figure, reference numeral 6 represents a cathode ray tube, reference numeral 7 a deflection coil, and reference numerals 8a and 8b electric wires for producing cancellation magnetic flux, respectively. The electric wires 8a and 8b are disposed in a manner that they are wound on the upper and lower halves around the display surface 10, respectively. A horizontal deflection current is delivered in a direction indicated by an arrow in the figure. The deflection coil 7 is provided in the vicinity of an electron gun 9 so that it deflects an electron beam. A horizontal deflection current is delivered from the deflection circuit to the deflection coil 7.
[0014] At this time, a signal from the deflection circuit is delivered to the deflection coil 7, and this signal is also delivered to the electric wires 8a and 8b, and varies in synchronism with the signal flowing in the deflection coil 7.
[0015] The leakage magnetic flux was measured under the following condition in connection with the systems I to IV according to the above-described first and second prior arts.
[0016] For measuring the recommendated value announced by the above SSI in Sweden, a meter (MAGNETIC FIELD METER MODEL MFM 1000) capable of measuring a low frequency leakage magnetic field developed by Combinova Company in Sweden is used. An actual measurement was conducted as follows. As shown in FIG. 3, antennas corresponding to magnetic fields from three directions were installed at positions of A, C and E. The CRT display apparatus was then rotated clockwise and anticlockwise using the central point of the display apparatus as a center. The change rate of the magnetic field and the strength of the magnetic field under the condition in FIGS. 3 and 4 (particularly at positions and angles of the antenna relative to the cathode ray tube), i.e., at the positions where antennas are installed, labelled A0, A1, A2, A14, A15, C0, C1, C2, C14, C15, E0, E1, E2, E14, E15, are measured by allowing a sawtooth current 7.8 A p-p having a horizontal deflection frequency of 20 KHz to flow in a horizontal deflection coil (not shown) of the deflection yoke 12 of the cathode ray tube 11, and by allowing a sawtooth current having a vertical deflection frequency of 60 Hz to flow in a vertical deflection coil (not shown).
[0017] As a result, the maximum values and the minimum values of measured values at 15 positions in accordance with the above-described systems I to IV are as shown in FIG. 5.
[0018] All the measured values shown in this figure vary to much extent depending upon the wiring position of a lead wire for conducting a current into the electric wire for cancellation of leakage magnetic flux provided in the vicinity of the face-plate of the cathode ray tube. By changing the wiring position of the lead wire, a value at a specific position on the above-mentioned electric wire may be minimized. However, if measurement is made with the lead wire in the above-described first and second prior arts hanging down in a direction of gravity, it was impossible to minimize, in a well- balanced manner, measured values on the measurement spherical body constituted by the above-described 15 positions. Further, cathode ray tube display apparatus could be hardly mass-produced in such an unbalanced state.
[0019] It is to be noted that respective measured values shown in FIG. 5 indicate values in the case of producing a magnetic field in a direction opposite to that in the description in the patent specification (EPC.A No. 89306388.8) according to the second prior art.
[0020] Meanwhile, when, as in the above-described arrangement shown in FIGS. 1 A and 1 B, two electric wire sections 1 a and 1 for cancellation of leakage magnetic flux along the upper and lower side edge portions of the face-plate 2 are connected by electric wires indicated by broken lines, which are subjected to wiring on the diagonal line, a magnetic flux in the same direction as that of a magnetic flux (leakage flux) produced from the deflection coils 4a, 4b is produced across the electric wire on the diagonal line. Not only the leakage magnetic flux cancellation effect by the electric wire sections 1 a and 1 b can be reduced, but also it could not be expected to uniformly exhibit the leakage magnetic flux cancellation effect on the above-described spherical body designated by the SSI institution.
[0021] Further, also in the arrangement shown in FIG. 1C, a magnetic flux generated from the electric wire indicated by broken lines becomes effective in a direction of decreasing the leakage magnetic flux cancellation effect. Thus, a sufficient effect could not be expected.
[0022] Furthermore, in the above-described second prior art (EPC Appln. No. 89306338.8), it is suggested that the source from which a leakage magnetic flux is produced in front of the display surface of the cathode ray tube is a bend-up portion of the horizontal deflection coil.
[0023] However, as shown in FIG. 8 which will be described later, how an actual leakage magnetic flux is produced is such that leakage magnetic flux B2b radiated in a forward direction of the fluorescent display surface 53a is extremely greater than the magnetic flux B1 produced from the bend-up portions 50ai and 50bi of the horizontal deflection coils 50a and 50b. Thus, it is necessary to produce a cancellation magnetic flux in a direction opposite to that of the second prior art.
[0024] When a leakage magnetic flux cancellation magnetic flux is produced in a direction as indicated by the patent specification according to the above-described second prior art, a far greater leakage magnetic flux would be produced as compared to the case where there is no electric wire for cancellation of leakage magnetic flux.
[0025] In addition, as shown in FIGS. 11, 12 and 17 which will be described later, a leakage magnetic flux 82c in the same direction as that of the main magnetic flux B2a component is produced also from the side surface portions of the cathode ray tube or the side surface portions of the deflection yoke. Since this leakage magnetic flux B2c exerts an effect also in the forward direction of the display surface, unless such a leakage magnetic flux B2c is canceled along with other leakage magnetic flux, the leakage magnetic flux of the entirety of the cathode ray tube display apparatus cannot be reduced to a low level. Particularly cancellation of the leakage magnetic flux B2c toward the side surfaces could not be imagined by the prior art.
[0026] Accordingly, none of the above-described prior arts can reduce the strength of an unnecessary magnetic flux over the entire periphery of the cathode ray tube, and manufacture apparatus which can satisfy the standard requirement of recent display manufacturers and sellers. Thus, it was necessary to stably reduce the leakage magnetic flux radiated from the cathode ray tube display apparatus and to allow the value of the leakage magnetic flux to fall within the above-mentioned recommended value.
SUMMARY OF THE INVENTION
[0027] This invention has been made in view of the above, and its object is to provide a method and a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, which can satisfy the standard requirements of display manufacturers and sellers.
[0028] Namely, the object of this invention is to provide a method and a device for suppression of leakage of magnetic flux, which prevents that a magnetic flux produced from a coil for suppression of leakage of magnetic flux rather promote a leakage magnetic flux in a specific direction around CRT, and which is capable of reducing, efficiently and to such an extent having no serious harmful influence on the human body, a leakage magnetic flux produced from CRT, having a bad influence on other equipment and harmful to the human body.
[0029] To achieve the above object, a device for suppression of leakage of magnetic flux according to this invention is, in a CRT display apparatus comprising a CRT, a deflection yoke at the neck portion of the CRT, and a face-plate portion for holding the display surface of CRT, characterized in that an electric wire for suppression of leakage magnetic flux is constituted by a first upper electric wire portion and a second lower electric wire portion arranged at positions as close as possible to the display surface at the upper and lower edges of the face-plate portion and bent slightly toward the inside of four corner portions, and first and second four lead wire portions disposed extending to the central portion of the both side surfaces of the deflection yoke from the position where the first and second electric wires are bent and gradually coming close in proportion to the distance from the rear portion of the CRT so as to gather at the neck portion on the both side surfaces of the CRT; and in that, in order to suppress a main deflection magnetic flux leaking out from the front surface of the face-plate, a current in a direction for canceling the main magnetic flux is delivered to the first and second electric wire portions, and a current in the same direction as that of a horizontal deflection current for producing the main magnetic flux is delivered to the first and second lead wire portions.
[0030] More particularly, in order to solve the above-described problems, this invention provides a method and a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus as featured below.
[0031] First, there is proposed a method for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the method comprising the steps of:
arranging first and second electric wires at the upper and lower side edge portions of a face-plate portion as close as possible to the display surface in the vicinity of the boundary surface between a main deflection magnetic flux produced from a horizontal deflection coil of a deflection yoke in a cathode ray tube display apparatus provided with a cathode ray tube, the deflection yoke attached at the neck portion of the cathode ray tube, the face-plate portion for holding the display surface, and a funneled portion, and a magnetic flux radiating from the forward direction of the display surface and produced from the bend-up portion of the horizontal deflection coil,
arranging and bending the first and second electric wires in the vicinity of the boundary plan between the main deflection magnetic flux radiating toward the both left and right side wall portions of the face-plate portion and the magnetic flux produced from the bend-up portion of the horizontal deflection coil between respective corner portions of the face-plate portion and the portions in the vicinity of the left and right side wall portions of the face-plate portion intersecting with the horizontal plane of the cathode ray tube,
in arranging first and second lead portions contiguous to the first and second electric wires from the both left and right wall portions of the face-plate portion toward the portion in the vicinity of the neck portion side of the horizontal deflection coil, arranging the first and second lead portions so that a spacing between the first and second lead portions gradually becomes small, between the portion in the vicinity of a boundary plan and the horizontal plane, the boundary plane being formed between the main deflection magnetic flux radiating toward the side wall portions of the funneled portion and the side wall portions of the deflection yoke, a leakage magnetic flux component of the main deflection magnetic flux, and a magnetic flux produced from the bend-up portion of the horizontal deflection coil,
delivering, into the first and second lead wires, a current having a magnetic flux in the same direction as that of the horizontal deflection current delivered to the horizontal deflection coil, and canceling, by the first and second electric wires and the first and second lead portions, a leakage magnetic flux radiated from the cathode ray tube display apparatus with the deflection yoke attached thereto over the entire surrounding of the cathode ray tube.
[0032] Secondly, there is proposed a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the device comprising:
first and second electric wires arranged at the upper and lower edge portions and the both left and right side wall portions of a face-plate portion as close as possible to the display surface in the vicinity of the boundary plane between a main deflection magnetic flux produced from a horizontal deflection coil of the deflection yoke in a cathode ray tube display apparatus provided with a cathode ray tube, the deflection yoke attached at the neck portion of the cathode ray tube, the face-plate portion for holding the display surface, and a funneled portion, and a magnetic flux radiating from the forwarding direction of the display surface and produced from the bend-up portion of the horizontal deflection coil, and arranged and bent up to the portion in the vicinity of the boundary plane between the main deflection magnetic flux radiating toward the both left and right side walls of the face-plate portion and a magnetic flux produced from the bend-up portion of the horizontal deflection coil, between respective corner portions of the face-plate portion and the horizontal plane of the cathode ray tube, respectively; and
first and second lead portions contiguous to the respective first and second electric wires, and arranged, when they are arranged from the bent portion of the both left and right side walls of the face-plate portion toward the portion in the vicinity of a terminal on the neck portion side of the horizontal deflection coil, through the horizontal plane, along the boundary plane between the main deflection magnetic flux radiated toward the side walls of the deflection yoke and the funneled portion, a leakage magnetic flux, and the magnetic flux produced from the bend-up portion of the horizontal deflection coil so that a spacing between the first and second lead portions gradually becomes small, a current having the same direction of a magnetic flux as that of the horizontal deflection current delivered to the horizontal deflection coil being delivered to the first and second lead portions; a leakage magnetic flux radiated from the cathode ray tube display apparatus with the deflection yoke attached thereto being canceled over the entire surrounding of the cathode ray tube by the first and second electric wires and the first and second lead portions;
thirdly, there is proposed a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the device comprising:
first and second electric wires arranged at the upper and lower edge portions and the both left and right side walls of a face-plate portion as close as possible to the display surface in the vicinity of the boundary plane between a main deflection magnetic flux produced from a horizontal deflection coil of the deflection yoke in a cathode ray tube display apparatus provided with a cathode ray tube, the deflection yoke attached at the neck portion of the cathode ray tube, and the face-plate portion for holding the display surface, and a funneled portion and a magnetic flux radiating from the forwarding direction of the display surface and produced from the bend-up portion of the horizontal deflection coil, and arranged and bent at the both left and right both side walls of the face-plate portion in the vicinity of substantially the inter- medium portion of respective corner portions of the face-plate portion and the horizontal plane of the cathode ray tube, respectively; and
first and second lead portions contiguous to the respective first and second electric wires, and arranged; when they are arranged from the both left and right side walls of the face-plate portion toward the horizontal deflection coil, through the horizontal plane, so that a spacing between the first and second lead portions gradually becomes small to reach zero, a current having the same direction of a magnetic flux as that of the horizontal deflection current delivered to the horizontal deflection coil being delivered to the first and second lead portions;
a leakage magnetic flux radiated from the cathode ray tube display apparatus with the deflection yoke attached thereto being canceled over the entire surrounding of the cathode ray tube by the first and second electric wires and the first and second lead portions.
[0033] Fourthly, there is proposed a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the device comprising: first and second electric wires arranged at the upper and lower edge portions and the both left and right side walls of a face-plate portion as close as possible to the display surface in the vicinity of the boundary plane between a main deflection magnetic flux produced from a horizontal deflection coil of the deflection yoke in a cathode ray tube display apparatus provided with a cathode ray tube, the deflection yoke attached at the neck portion of the cathode ray tube, face-plate portion for holding the display surface, and a funneled portion, and a magnetic flux radiating from the forwarding direction of the display surface and produced from the bend-up portion of the horizontal deflection coil, and arranged in the vicinity of the both left and right side walls of the face-plate portion intersecting with the horizontal plane of the cathode ray tube from the respective corner portions of the face-plate portion, respectively; and first and second lead portions contiguous to the respective first and second electric wires, and arranged, so that they are opposite to each other from the both left and right side walls of the face-plate toward the horizontal deflection coil, a current having the same direction of a magnetic flux as that of the horizontal deflection coil being delivered to the first and second lead wires; a leakage magnetic flux radiated from the cathode ray tube display apparatus with the deflection yoke attached thereto being canceled over the entire surrounding of the cathode ray tube by the first and second electric wires and the first and second lead portions.
[0034] Fifthly, there is proposed a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the device comprising:
a demagnetization coil attached on a funneled portion in a cathode ray tube display apparatus provided with a cathode ray tube, a deflection yoke attached at the neck portion of the cathode ray tube, and a face-plate portion for holding the display surface, a funneled portion, and for carrying out demagnetization of a shadow mask, etc.,
first and second electric wires attached at the both ends thereof to the magnetization coil, arranged at the upper and lower edge portions of the face-plate portion as close as possible to the display surface, and arranged and extended to respective corner portions of the face-plate portion,
first and lead wires contiguous to the respective first and second electric wires, and arranged so that they are opposite to each other substantially along the horizontal plane of the cathode ray tube from the both left and right side walls of the face-plate portion toward the horizontal deflection coil of the deflection yoke, a current having the same direction of a magnetic flux as that of a horizontal deflection current delivered to the horizontal deflection coil being delivered to the first and second lead wires,
a leakage magnetic flux irradiated from the cathode ray tube display apparatus with the deflection yoke attached thereto being canceled over the entire surrounding of the cathode ray tube by the first and second electric wires and the first and second lead portions.
[0035] Sixthly, there is proposed a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus, the device comprising:
a demagnetization coil attached on a funneled portion in a cathode ray tube display apparatus provided with a cathode ray tube, a deflection yoke attached at the neck portion of the cathode ray tube, a face-plate portion for holding the display surface, and a funneled portion, and for carrying out demagnetization of a shadow mask, etc., first and second electric wires attached at the both ends thereof to the magnetization coil, arranged at the upper and lower edge portions of the face-plate portion as close as possible to the display surface, and arranged and bent at the both left and right side walls of the face-plate portion in the vicinity of substantially the intermediate portion of the respective corner portions of the face-plate portion and the horizontal plane of the cathode ray tube, respectively, and
first and second lead wires contiguous to the respective first and second electric wires, arranged, when they are arranged from the both left and right side walls of the face-plate portion toward a horizontal deflection coil of the deflection yoke, through the horizontal plane so that a spacing between the both lead wires gradually becomes small to reach zero, a current having the same direction of a magnetic flux as that of a horizontal deflection current delivered to the horizontal deflection coil being delivered to the first and second lead portions,
a leakage magnetic flux irradiated from the cathode ray tube display apparatus with the deflection yoke attached thereto being canceled over the entire surrounding of the cathode ray tube by the first and second electric wires and the first and second lead portions.
[0036] As described above, in accordance with this invention, electric wires and lead portions contiguous thereto for producing a cancellation magnetic flux for canceling a leakage magnetic flux from the deflection coil are arranged on the upper and lower surfaces, and left and right side surfaces of the face-plate near the fluorescent display screen surface of the cathode ray tube, the side wall of the cathode ray tube, and the side surfaces of the deflection yoke, thus allowing a current in the same direction as that of a current flowing in the horizontal deflection coil to flow in the electric wires and the lead portions. Thus, the advantages are provided as follows. The strength and the change rate of a magnetic flux from the side surfaces of the cathode ray tube and/or the fluorescent display screen surface can be reduced to much extent over the entire surrounding of the cathode ray tube display apparatus. Further, interference with other equipment and/or influence on the human body can be reduced. In addition, by arranging, on the demagnetization coil, an electric wire for canceling a leakage magnetic flux, labor in attaching an electric wire independent of the demagnetization coil is saved, and positioning for such an attachment work or fixing of the electric wire is facilitated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In the accompanying drawings:
FIGS. 1 A to 1 C and FIG. 2 are schematic diagrams and a perspective view showing the arrangement of the first and second prior arts, respectively;
FIGS. 3 and 4 are diagrams showing conventional measurement methods for measuring a low frequency leakage magnetic flux, respectively;
FIG. 5 is a Table collectively showing measured values obtained by the measurement methods shown in FIGS. 3 and 4;
FIG. 6 is a perspective view showing a device of a first embodiment according to this invention attached to a cathode ray tube display apparatus;
FIGS. 7A to 7D are circuit diagrams showing the states of connection between horizontal deflection coils 50a, 50b and electric wires 51a, 51b for producing a magnetic flux for canceling a leakage magnetic flux;
FIGS. 8 to 11 are diagrams showing the distributions of magnetic flux produced in the case where the device according to this invention attached to a cathode ray tube display apparatus is used, respectively;
FIG. 12 is a diagram showing the distribution of magnetic flux of a deflection yoke produced in the case where the cathode ray tube display apparatus is in a use state;
FIG. 13 is a rear perspective view showing a cathode ray tube display apparatus;
FIGS. 14 and 15 are perspective views showing the state where devices of second and third embodiments according to this invention are attached to a cathode ray tube display apparatus, respectively;
FIGS. 16 and 17 are perspective views showing the state where devices of fourth and fifth embodiments according to this invention are attached to a cathode ray tube display apparatus; respectively; and
FIGS. 18 and 19 are perspective view showing devices of fourth and fifth embodiments according to this invention, respectively.
DETAILED DESCRIPTION OF THE PREFERRED EMBODiMENTS
[0038] Preferred embodiments of a method and a device for suppression of leakage of magnetic flux in a cathode ray tube display apparatus will be described in conjunction with FIGS. 6 to 19, respectively.
[0039] The outline of the method and the device for suppression of a leakage of magnetic flux in a cathode ray tube display apparatus will be seen particularly by making reference to a first embodiment of a device according to this invention.
[0040] Accordingly, attention is first to FIG. 6 showing the state where the device of the first embodiment is attached to a cathode ray tube display apparatus.
[0041] As shown in this figure, the outline of the cathode ray tube display apparatus A is composed of a cathode ray tube 53 including a fluorescent display screen surface 53a, a funneled portion 53c, a neck portion 53d, and a side wall 56, and a deflection yoke 54 having a horizontal deflection coil (not shown) attached to the neck portion 53d.
[0042] Further, electric wires 51a, 51 b and four lead portions 51ai, 51a1, 51bi, 51bi contiguous thereto for producing a magnetic flux for canceling a leakage magnetic flux are added to the side wall 56 of the cathode ray tube 53 and the upper and lower side edge portions 53b3, 53b4 of the plate portion 53b. The both ends of 51a1, 51b1 are connected to connection portions 60, 60 of the deflection yoke 54 along the portion in the vicinity of the side walls 56,56.
[0043] In FIG. 6 four metal fittings 53f1, 53f4, 53f3 and 53f2 are affixed on four corner portions 53b5, 53b6, 53b7 and 53b8 of the face-plate portion 53b of the cathode ray tube 53, respectively. Further, electric wires 51 a and 51 b are arranged in the vicinity of the fluorescent display screen surface 53a along the upper and lower side edge portions 53b3 and 53b4 of the face-plate portion 53b from the portion in the vicinity of the metal fittings 53f1 and 53f4 on one side surface portion 53b1 side of the face-plate portion 53b to the portion in the vicinity of the metal fittings 53f2 and 53f3 on the other side surface portion 53b2 side, and bent thereat.
[0044] Then, a pair of electric wires 51 a and 51 b are disposed approximately along top and bottom rims of the face-plate portion 53b and are contiguous to lead portions 51a1 and 51b1 and extended to terminal portion 60 which is located at a rear of the deflection yoke 54 and on a horizontal plan which is approximately perpendicular to the face-plate portion 53b and crosses horizontally the face-plate portion 53b at a vertical center thereof so that lead portions 51a1 and 51b1 progressively approach the horizontal plane toward the rear of the deflection yoke 54 along the side walls 56 and 56 of the funnel portions 53c, respectively. The lead portions 51 ai and 51 b1 are bent along respective side rims of the face-plate portion 53b to couple with main portions of the electric wires 51 a and 51b, which are located respectively at the top and bottom rims of the face-plate portion 53b as mentioned previously. Then, a current having a time function substantially corresponding to the time function of an electric wires 51 a and 51 are contiguous to four lead wires 51a1, 51b1 and 51a1, 51b1 and electric wires 51 a and 51 may be elongated by the length corresponding to these lead wires in place of using these lead wires according to need.
[0045] FIGS. 7A to 7D are circuit diagrams showing the state of connection between horizontal deflection coils 50a, 50b and electric portions 51a, 51b b for producing a magnetic flux for canceling a leakage magnetic flux.
[0046] In the case of the connection shown in FIG. 7A, the above-mentioned electric portions 51a, 51b b connected in parallel are cascade-connected to the horizontal deflection coils 50a, 50b connected in parallel constituting the deflection yoke 54. As a modification thereof, connections shown in FIGS. 7B to 7D which will be described later may be employed.
[0047] In the case of the connection shown in FIG. 7B, a variable or fixed inductance L is connected in parallel with the electric portions 51 a, 51 b connected in parallel. Further, in the case of the connection shown in FIG. 7C, a variable resistance R is connected thereto in place of the variable or fixed inductance L shown in FIG, 7B. In addition, in the case of the connection shown in FIG. 7D, electric portions 51 a, 51 are connected to the succeeding stages of the horizontal deflection coils 50a, 50b connected in parallel.
[0048] In any of the circuit arrangements shown in FIGS. 7A to 7D, a current approximately proportional to the deflection current going through the horizontal deflection coils 50a and 50b, flows through the electric wires 51 a and 51 b. In FIGS. 7A to 7D, the horizontal deflection coils 50a and 50b may be connected each other in series, but it is possible to obtain the same effect, to therefore omit figures and description thereof.
[0049] Referring to FIGS. 8 to 11, there are shown distributions of magnetic flux produced in the state where the device of this invention attached to a cathode ray tube display apparatus is used.
[0050] As shown in FIG. 8, when a main magnetic flux (main deflection magnetic flux) B2a is produced on the horizontal deflection coils 50a, 50b, a partial magnetic flux B2b of the main magnetic flux B2a leaks out toward the outside from the fluorescent display screen surface 53a.
[0051] In FIG. 8, currents I50a1, I50b1, I50a2, I50b2 flow, in a direction indicated by the symbol representing the opposite side of the deflection perpendicular to the plane of paper (0) or representing this side thereof (
), in the bend-up portions 50a1, 50b1 on the fluorescent display screen surface 53a of the horizontal deflection coils 50a, 50b and the bend-up portions 50a2, 50b2 on the neck portion 53d side opposite thereto. Thus, a leakage magnetic flux B1 is produced.
[0052] Namely, as shown in FIG. 8, two boundary planes between the main magnetic flux B2a and the leakage magnetic flux B1 exist substantially at the positions 55a, 55b indicated by broken lines (such boundary planes may exist on the display screen surface depending on the kind of the cathode ray tube).
[0053] Electric wires 51a, 51 are arranged in the vicinity of the two boundary planes 55a and 55b and at the upper and lower side edge portions 53b3, 53b4 of the face-plate portion 53b as close as possible to the fluorescent display screen surface 53a, respectively. When currents 151a, 151b are caused to flow in these electric wires in directions shown in FIGS. 8 and 9, respectively, magnetic flux B3a, B3b are produced therefrom.
[0054] These magnetic flux B3a, B3b become active in a direction of canceling leakage magnetic flux Bi, B2b with respect to the direction located forward than the upper and lower outsides of the boundary planes 55a, 55b and the fluorescent display screen surface 53a.
[0055] Especially, leakage magnetic flux B2b radiated from the fluorescent display screen surface 53a toward the outside, and leakage magnetic flux B1 radiated from the upper and lower side edge poe- tions 53b3, 53b4 of the face-plate portion 53b and the upper and lower sides of the funneled portion 53c toward the outside can be suppressed.
[0056] On the other hand, as shown in FIG. 12, when a current is caused to flow in the horizontal deflection coils 50a, 50b, a main magnetic flux B2a is produced in the horizontal plane direction of the deflection yoke 54. A portion of the main magnetic flux B2a leaks out from the cores 58a, 58b of the deflection yoke toward the outside. Thus, a leakage magnetic flux B2c is produced.
[0057] By the influence of the leakage magnetic flux B2e, leakage magnetic flux B2c which is a portion of the main magnetic flux B2a is a portion of the main magnetic flux B2a is produced on the side wall 56 (x-axis plane) of the cathode ray tube 53 indicated by slanting lines in the rear perspective view of a cathode ray tube display apparatus shown in FIG. 13, i.e., between the corner portion 53b5 and the corner portion 53b6 of the face-plate portion between which the horizontal plane is present and between the corner portion 53b7 and the corner portion 53b8 thereof as shown in FIGS. 9 and 10.
[0058] The boundary surface between the leakage magnet flux B1 and the leakage magnetic flux B2c exists substantially along the positions indicated by broken lines 57a, 57b shown in FIG. 13, i.e., four corner portions of the cathode ray tube 53 (i.e., four corner portions 53b5, 53b6, 53b7, 53b8 of the face-plate portion 53b).
[0059] To cancel these leakage magnetic flux B1, B2c, as shown in FIGS. 10 and 11, four lead portions 51a1, 51bi, 51a1, 51b1 of the electric wires 51a, 51b in a manner that a spacing β between respective lead wires is gradually widened at upward and downward positions on the horizontal plane according as the distance between the both left and right side surface portions 53bi, 53b2 of the face-plate portion 53b close to the fluorescent display screen surface 53a of the cathode ray tube 53 and the deflection yoke 54 decreases. When a current in a direction of the currents shown in FIGS. 10 and 11 is caused to flow, a magnetic flux B3 is produced in a direction of canceling the magnetic flux B2c.
[0060] Thus, leakage flux B2c radiated from the side surface portions of the deflection yoke 54 and/or the side wall 56 of the cathode ray tube 53 can be suppressed.
[0061] It is to be noted that if the spacing β between lead portions 51a1, and 51b1 arranged at positions spaced from the side walls 56 of the cathode ray tube 53 at a predetermined interval is excessively widened as shown in FIG. 6, the leakage magnetic flux B2c becomes smaller than the cancellation magnetic flux B3. As a result, the cancellation magnetic flux B3 has an effect on the upper and lower portions of the boundary surfaces 57a, 57b between the leakage magnetic flux B2c and the leakage magnetic flux Bi, thus to strengthen the leakage magnetic flux at the upper and lower portions of the boundary surfaces 57a, 57b.
[0062] For this reason, as shown in FIG. 6, wiring of electric wires 51 a, 51 b and four lead portions 51a1 , 51b1, 51a1, 51bl is implemented in a manner that they pass from the side surface portion (near the horizontal plane) on the neck portion 54d side of the deflection yoke 54 through the corner portions 53ai to 53a4 of the fluorescent display screen surface 53a of the cathode ray tube 53, i.e., the portions in the vicinity of the side surface portions 56, 56 of the four metal fittings 53f1, 53f4, 53f3, 53f2 provided on the four corner portions 53b5, 53b6, 53b7, 53b8, of the face-plate 53b. By an employment of such a wiring, lead portions 51 a1, 51 b2 are located at positions closer to the horizontal plane side than the boundary lines 57a, 57b. Thus, leakage magnetic flux B2c can be stably suppressed, resulting in an improved leakage magnetic flux suppression effect.
[0063] Meanwhile, since the horizontal deflection coils 50a, 50b swing an electron beam (not shown) in a lateral direction of the cathode ray tube 53 as shown in FIG. 9, a main magnetic flux B2a is caused to be produced in a longitudinal direction perpendicular to the scanning direction (horizontal plane direction) of the electron beam. For this reason, horizontal deflection coils 50a, 50b are provided at the upper and lower positions on the horizontal plane of the cathode ray tube 53. Accordingly, the horizontal deflection coils 50a, 50b interchangeably produce, as magnetic flux B1, B1a, B2b produced therefrom, magnetic flux having directions opposite to the directions indicated by respective arrows shown in FIGS. 10 and 11 in correspondence with the horizontal deflection frequency.
[0064] Some research results teach that since a relatively large power is delivered to the horizontal deflection coils 50a, 50b, a leakage magnetic flux toward the external direction from the cathode ray tube as shown in FIG. 13 of the magnetic flux produced thereby is apt to interfere with other electronic equipment and a low frequency magnetic flux is harmful to the human body. The standard requirement for such phenomena is severe.
[0065] As stated above, the place where two electric wires 51a, 51 and four lead portions 51a1, 51bi, 51a1, 51b1 are attached is not limited to the cathode ray tube in this invention, but a leakage magnetic flux suppression device according to this invention may be attached to structure in the vicinity of the display screen surface 53a of the cathode ray tube 53, such as a cabinet for accommodating the cathode ray tube 53 so that a predetermined leakage magnetic flux suppression effect is provided. The object or place where the device according to this invention is attached is not limited.
[0066] Referring to FIGS. 14 and 15, there are shown the state where the second and third embodiments of the devices according to this invention are attached to the cathode ray tube display device. The same components as those described above are designated by the same reference numerals, respectively, and their explanation will be omitted.
[0067] As shown in FIG. 14, the second embodiment of the device according to this invention is of substantially the same structure as the first embodiment shown in FIG. 6, but differs from the first embodiment in the following points.
[0068] Namely, in accordance with the device according to the second embodiment, one lead portion 51a1, 51b1 contiguous to electric portions 51a, 51 b respectively arranged on the side walls 56, 56 of the cathode ray tube 53 are conducted, toward the side surface portion 54a of the deflection yoke 54, from substantially the intermediate portion of the side surface portion 53b1 of the face-plate 53b halved as a result of the fact that the line connecting the corner portions 53b5 and the corner portion 53b6 of the face-plate 53b and the horizontal plane extending from the deflection yoke 54 to the display screen surface 53a through the side surface portion 53bi of the face-plate 53b intersect with each other. The other lead portions 51a1, 51 bi are conducted, toward the side surface portion 54a of the deflection yoke 54, substantially from the intermediate portion of the side surface portion 53b2 of the face-plate 53b halved as a result of the fact that the line connecting the corner portions 53b7 and the 53b8 of the face-plate 53b and the horizontal plane extending to the display screen surface 53a from the deflection yoke 54 through the side surface portion 53b2 of the face-plate 53b intersect with each other. Further, these lead portions 51a1, 51 b1 are arranged in a manner that the spacing β between lead portions 51a1 and 51b1 gradually becomes narrow from the left and right side surface portions 53bl, 53b2 of the face-plate 53b from substantially the intermediate portion of the length of respective lead portions 51a1, 51b1 extending to terminal portions 60, 60 of the deflection yoke 54, and are arranged in parallel so that they are adjacent to each other from the intermediate portion to the terminal portions 60, 60 of the deflection yoke 54.
[0069] As shown in FIG. 15, the third embodiment of the device according to this invention is of substantially the same structure as that of the above-described first embodiment shown in FIG. 6, but differs from the first embodiment in the following point.
[0070] The device according to the third embodiment is characterized in that even if lead portions 51a1, 51b1 contiguous to electric portions 51a, 51b arranged on the side surface portion 56 of the cathode ray tube 53 become close to the fluorescent display screen surface 53a, the both lead wires are adjacent to each other.
[0071] Usually in a color cathode ray tube display apparatus, a demagnetizing coil is equipped around the CRT to prevent the shadow mask of the CRT from being magnetized by the earth magnetism. In such a type apparatus, abovementioned leakage flux cancelling wiring may be composed of the demagnetizing coil as a body for supporting thereof.
[0073] FIG. 16 is a perspective view showing the state where the device according to this invention shown in FIG. 18 which will be described later is attached to a cathode ray tube display apparatus, and FIG. 17 is a perspective view showing the state where the device according to this invention shown in FIG. 19 which will be described later is attached to a cathode ray tube display apparatus. The same components as those described above are designated by the same reference numerals, respectively, and their explanation will be omitted.
[0074] As shown in FIG. 16, the cathode ray tube display apparatus B is characterized in that a demagnetization coil 62 which will be described later is additionally provided in the arrangement of the above-described cathode ray tube display apparatus A.
[0075] Namely, as shown in FIGS. 16 and 18, the both ends of electric portions 51a, 51 b for producing a magnetic flux for canceling the above-described leakage magnetic flux are attached, with a predetermined spacing therebetween, to the demagnetization coil 61 for demagnetizing magnetization, etc. of the shadow mask portion 53e attached on the funneled portion 53c. In order to cancel leakage magnetic flux B2c which is a portion of the main magnetic flux B2a, as shown in FIG. 5 mentioned above, electric portions 51 a, 51 b are arranged on the left and right side surface portions 53bi, 53b2 of the face-plate portion 53b close to the fluorescent display screen surface 53a of the cathode ray tube 53, respectively. Then, lead portions 51a1, 51b1, 51 ai, 51b1 contiguous thereto are conducted to the side surfaces 54a, 54a of the deflection yoke 54 substantially along the horizontal plane in the vicinity of the side walls 56, 56 of the cathode ray tube 53, and are fixed at predetermined positins (e.g., terminal portions 60, 60). A current is caused to flow in these lead wires in a direction shown in FIG. 10, thus to produce a magnetic flux B3 in a direction of canceling the magnetic flux B2c. Thus, leakage magnetic flux B2c leaking out, toward the outside, from the side walls 56, 56 of the cathode ray tube 53 and the side surfaces 54a, 54a of the deflection yoke 54 can be suppressed. Further, electric portions 51a, 51 b are arranged on the upper and lower side edge portions 53b3, 53b4 of the face-plate portion 53b of the above-described cathode ray tube 53 shown in FIG. 8. A current is caused to flow in these electric wires in a direction of the current shown in FIG. 8, to produce a magnetic flux B3 for canceling the leakage magnetic flux B2b, Bi. Thus, leakage magnetic flux B2b, B1 radiated from the fluorescent display screen surface 53a can be suppressed. The fourth embodiment of the device according to this invention is constructed as shown in FIG. 18. Reference numeral 61a a denotes a connection appliance provided on the lead wire end of the demagnetization coil 61. Reference numerals 51, 51 denote connectors attached to the initial ends 51c1, 51c2 and the terminating ends 51 di, 51 d2 of the electric portions 51a, 51b, respectively. In place of using these connectors 51, 51', such electric wires may be soldered to respective predetermined portions.
[0076] The fifth embodiment of the device according to this invention is constructed as show in in FIG. 19. This embodiment is substantially the same structure as that of the above-described fourth embodiment show in in FIG. 18, but differs from the fourth embodiment in that lead portions 51 ai, 51b1, 52ai, 51bl contiguous to the electric wires 51 a, 51 b are arranged in a manner that the spacing between two sets of lead portions is gradually widened according to these lead wires bewcome close to the fluorescent display screen surface 53a.
[0077] As described above, this invention is not limited to the first to fifth embodiments, but include various implementations which can be considered to be identical in principle in the method of canceling leakage magnetic flux.
[0078] It is to be noted that while leakage magnetic flux from the deflection coil 54 varies depending upon the shape or deflection current of the cathode ray tube display apparatus, electric wires 51 a, 51 b may be connected in series with the both ends of the horizontal deflection coils 50a, 50b as shown in FIG. 7D, or they may be connected, as shown in FIGS. 7B and 7C, in parallel with electric wires 51a, 51b to which inductance L or resistance R is connected in parallel to adjust a current flowing therein, thus to balance such a leakage magnetic flux.
[0079] For reference, values of leakage magnetic flux from the fluorescent display screen surface 53a in the case of the embodiments according to this invention shown in FIG. 6 and FIGS. 7A to 7D and in the case where this invbention is not implemented (no measure is taken), which are measured at positions installed of the above-described antennas AO to A15, BO to B15, CO to C15, DO to D15, and EO to E15 shown in FIGS. 3 and 4 are shown in the following Table.
a pair of conductor means each of which has a main portion and a lead portion connected to the main portion, said main portion of the pair of conductor means being disposed approximately within said boundary plane and along approximately top and bottom rims of the face plate, respectively, said lead portion of the pair of conductor means disposed along a side wall of a funnel of the cathode ray tube in such a form that one end of the lead portion is bent along a side rim of the face plate to couple with said main portion and another end of the lead portion extends toward a rear of said horizontal beam deflection means, said pair of conductor means being driven with a current proportional to a horizontal deflection current flowing through said horizontal beam deflection means.