Compensated deflection yoke for cathode-ray tubes

Abstract: The present invention relates to the technical field of electronic control and adjustment devices and in particular to a compensated deflection yoke for cathode-ray tubes provided with two plastic supports (2) mounted, in register with the north and south sides of the yoke body (1), to the plastic magnet-holding ring (1a) in which they are structurally incorporated, which plastic supports (2) preferably are of polygonal form with rounded edges and are each provided with hooks (3) to allow the bucking coils to be snap-fitted thereon as well as with pins (5) for the fastening of the coil terminals (4a, 4b), said pins being also capable of supporting, when required, a dampening cell consisting of a resistor (6) connected in series to a capacitor (7); said bucking coils (4) can also have a variable number of turns, depending upon the compensation it is wished to achieve.

Description: The present invention relates to a deflection yoke compensated for electromagnetic radiations for a cathode-ray tube. It is known that in the field of television sets and monitors in general the necessity arises to reduce the electromagnetic radiation produced by the horizontal windings of the deflection yokes. In order to reduce said radiation, coils, naked bucking coils, are suitably arranged to the sides of the yoke body located at the rear end of the cathode-ray tube. A great difficulty is encountered on mounting said coils, as they must be fixedly secured to the yoke body, in a suitable manner with respect to the electromagnetic field on which it is wished to operate and must be properly clamped. At the present state of the art some monitor manufacturers have studied a compensating system provided with a bucking coil consisting of some turns of copper wire wound in the air, held together by some turns of insulating tape and fastened to the yoke partly by welding the terminals thereof to the yoke contacts and partly by means of silicone cements. However this structure is rather precarious and not at all reliable as regards lifetime and efficiency. Likewise there are some embodiments of handicraft type which generally exhibit the same structure as the one described above. From the foregoing it appears that compensation cannot be a fine one and that the structure reliability of the coil is limited because said coil is not integrally fastened to the yoke body to which it belongs, but it is only secured through the terminals thereof. Finally, when fastening is carried out by means of cements it is not very reliable because the coil can be easily removed from its seat, which is already precarious by itself, when the monitor is subjected to sudden and strong shakes. It is also to be pointed out that in such a precarious embodiment the calculus of compensation relating to the number of turns in bucking coils surely cannot be of high quality. It is therefore clear that it is necessary to find a solution which is capable of associating a reliability in use with a quick installation and high quality of yield. The foregoing and further objects which will best be understood from the following description, are attained in accordance with the present invention by a deflection yoke compensated for electromagnetic radiation in a cathode-ray tube characterized in that it comprises a yoke body (1), a plastic magnet-holding ring (1a) mounted to the widest circular base portion of said yoke body, and two plastic support plates (2) mounted simmetrically to the magnet holding ring in register to the north and south sides of the yoke and preferably of polygonal form with rounded edges and mounted preferably at right angles to the plane of the magnet holding ring, provided each with hooks (3) disposed at right angles to and on the symmetric ends of said support plates and designed to snap-fit bucking coils (4), and provided further with plastic pins (5) so disposed that they project with respect to said ends of the support plates (2) and are disigned to secure the coil terminals (4a, 4b), said pins preferably support and connect parallel to the coils a dampening circuit consisting of a resistor (6) connected in series to a capacitor (7), said bucking coils (4) having a number of turns, depending on the compensation to be achieved. Further features and advantages of the invention will become more apparent from the detailed description of a preferred embodiment of a deflection yoke compensated for electromagnetic radiations in a cathode-ray tube given hereinafter by way of non-limiting example with reference to the accompanying drawings, in which: fig. 1 is a simplified plan view of the yoke in which the magnet-holding ring is provided with plastic support plates for the respective bucking coils in accordance with the invention; Fig 2 is a front view of the plastic support plate provided with the dampening circuit of the invention. Referring to the drawings and particularly to Fig. 1, 1 denotes the yoke body taken as a whole, and 1a a plastic magnet-holding ring mounted to the widest circular base portion of the yoke body 1. Symmetrically to the magnet-holding ring and in register with the north and south sides of yoke 1, two plastic support plates are mounted as, shown in top view in the figure and identified by reference numeral 2. Said plastic support plates are provided with hooks 3 around which bucking coils 4 can be wound. The ends 4a and 4b of said bucking coils are fastened to pins 5 which, as more clearly shown in Fig. 2, are designed to support a dampening circuit which consists of a resistor 6 connected in series to a capacitor 7. According to this embodiment preferably the plastic support plates are in the form of a polygon with rounded edges, as clearly seen in Fig. 2. The plastic support plates 2 are disposed at right angles to the plane of the magnet-holding ring 1a of yoke 1 and symmetrically in register with the north and south sides of said yoke. Obviously the perpendicular condition of said support plates with respect to the plane of magnet-holding ring 1a is not compulsory, but if a necessity of electromagnetic nature for the compensation arises, said support plates are positioned at an angle to said plane of the magnet-holding ring of said yoke body, depending on the compensation to be achieved. The support plates 2 can also have different suitably shaped forms in order to optimize the required compensation. Operation of the yoke according to the invention described above mainly as regards structure, is as follows. Yoke body 1, provided with plastic support plates 2, is equipped with bucking coils 4 which are connected in parallel to each other and then in series with the horizontal winding of the yoke or in any other manner. Bucking coils 4, as well as the horizontal deflection ones, are made of self-cementing copper wire and are wound by an appropriate winding machine around a former intended for the purpose. For the above reasons they do not need wound around bands to ensure the cohesion of wires and therefore their arrangement on the structure of the yoke body 1, and as a result on the plastic support plates 2, is surely rigid and very reliable against any impact or shake. The number of turns in the bucking coils obviously depends on the number of turns in the horizontal deflection coils and on the degree of compensation to be achieved. The two pins to which terminals 4a and 4b of bucking coil 4 are fastened also allow a dampening circuit to be added each time it is necessary, said circuit consisting of a resistor connected in series to a capacitor, to resist the parasitic oscillations generated by the bucking coil. The invention thus attains the intended purposes. In fact, the present deflection yoke used for a cathode-ray tube exhibit a low radiated electromagnetic field intensity which is just reached by virtue of the use of bucking coils 4 directly mounted to the yoke body 1 on the above described plastic support plates 2 which are incorporated in the circular base portion of yoke 1 representing the plastic magnet-holding ring 1a. Furthermore, the compensation of electromagnetic radiations by the above solution has other particular characterizing features which can be summarized as follows: 1. an excellently-brought about mechanical mounting which allows an important saving as regards manual activity; 2. the rigidity of the wires which are also fastened to precise locations so as to eliminate excessive magnetic leakages; 3. a compact and net wiring which reduces the bulkiness of the compensated yoke to a minimum as well as all risks of entangling the connection wires being part of the monitor during the introduction of the yoke. It is therefore possible to assume that, unlike handcraft-made coils which must be manufactured one by one and then set in position and stuck in a suitable seat, the present bucking coils allow an important saving in manufacture and ensure a high production rate as compared to any other type of embodiment. Obviously further modifications are possible as regards structure and parameters, all falling within the scope of the claims.

Claims: A deflection yoke for a cathode-ray tube compensated for electromagnetic radiation characterized in that it comprises a yoke body (1), a plastic magnet-holding ring (1a) mounted to the widest circular base portion of said yoke body, and two plastic support plates (2) mounted simmetrically to the magnet holding ring in register to the north and south sides of the yoke and preferably of polygonal form with rounded edges and mounted preferably at right angles to the plane of the magnet holding ring, provided each with hooks (3) disposed at right angles to and on the symmetric ends of said support plates and designed to snap-fit bucking coils (4), and provided further with plastic pins (5) so disposed that they project with respect to said ends of the support plates (2) and are disigned to secure the coil terminals (4a, 4b), said pins preferably support and connect parallel to the coils a dampening circuit consisting of a resistor (6) connected in series to a capacitor (7), said bucking coils (4) having a number of turns, depending on the compensation to be achieved. A deflection yoke according to claim 1, characterized in that said plastic support plates (2) are positioned at all angle to the plane of the magnet holding ring of said yoke body depending on the compensation to be achieved. A deflection yoke according to claim 1, characterized in that said plastic support plates (2) are of several polygonal forms depending on the compensating effect to be obtained from the coils. A deflection yoke according to claim 1, characterized in that said bucking coils (4) are made of self-cementing copper wire and are automatically wound by means of winding machines.

Inventors: GERMANI EMILIO, GERMANI, EMILIO
Applicants: ELDOR CORP S P A, ELDOR CORPORATION S.P.A.
Application year: 1988
Main classification: H01J29
IPC codes: H01J29