DEFLECTION UNIT INCLUDING A LINE BALANCE COIL

Abstract: A deflection unit having a hollow synthetic material coil support within which a line deflection coil system is arranged, which line deflection coils are connected in an electric circuit to a line balance coil arrangement comprising a cylinder which is provided with two sub-coils and within which a magnet core is movably arranged. The coil cylinder is secured to the coil support and is provided with an arrangement of metal (connection) strips which ensure a direct connection between the balance coil lead-outs, the line deflection coils and a tap.

Description: Deflection unit including a line balance coil. The invention relates to a deflection unit within which a line deflection coil system is arranged, said line deflection coils being connected in an electric circuit to a line balance coil arrangement comprising a cylinder which is provided with two sub-coils and within which a magnet core is arranged. In deflection units for cathode ray tubes, such as display tubes, and particularly monitor tubes and television tubes, line balance coils are used to control the self- induction balance between the two line deflection coils. To this end, they are incorporated in a circuit with the line deflection coils. The line deflection coils are preferably arranged within a hollow synthetic material coil support. The conventional line balance coil comprises two sub-coils wound on a cylinder. The cylinder is an injection-moulded product of polycarbonate in which 4 wires are moulded, while at one end the coil is sealed and at the other end the wire is inserted into a PCB (Printed Circuit Board) and soldered. The PCB has "riveting bushes" which are used for security purposes. The PCB is the connection between contact pins G, H of the line balance coil and the contact pins A, D to which the line deflection coils are sealed. The PCB also ensures the connection between the line balance coil and the client connection E. The other client connection is B or C (see Figs. 1 , 2 and 4). In practice, these types of line balance coil-PCB constructions present problems which may even lead to fire. According to the invention, these problems are related to differences in expansion between PC (polycarbonate) of the coil cylinder and the PCB material, while the mode of establishing electrical contact via wires soldered in riveting bushes is not optimal. The deflection unit according to the invention, which obviates the above- described drawbacks and various other drawbacks of the state of the art, is characterized in that the coil cylinder is provided with an arrangement of metal (connection) strips which ensure a direct connection between the balance coil lead-outs, the line deflection coils and a tap. The essence of the invention is that the PCB is omitted and the functions of the PCB are integrated in the line balance coil. This means that a direct connection can be established between the line deflection coil and the line balance coil. It does not need to be e stablished via tracks on a PCB. In practice, this may be realized by integrating the contact between D and H in one pin, integrating the contact between A and G in one pin, integrating the contact F, I and E in one pin and integrating the contact B-C in one pin. These pin shapes are preferably punched from a "leadframe" which is enveloped in a mould and punched loose. Various bends may be formed in the mould. The pin shapes have the properties required to seal the coils and to connect clients. The position of the client connections is not fixed. Various positions are possible. Integration in the line balance coil of the sealing pins and the function of the PCB lead to the following advantages: - no problems caused by differences of expansion - mode of establishing contact is more secure - no PCB and riveting bushes required - no PCB punching tools required - no pin insertion tools required - no riveting tools required - no "expensive" PCB in the design stage - integrally cheaper - more friendly to the environment. In a preferred embodiment the coil cylinder is provided with a plurality of supporting members which are integrated with an arrangement of metal (connection) strips formed from a leadframe. The supporting members are preferably made of an insulating material. In particular, they are moulded from a synthetic material. In a further embodiment a plurality of supporting members extends transversely to the longitudinal axis of the cylinder. In a variant of the previous embodiment the supporting members extend in a plane parallel to the longitudinal axis of the coil cylinder and are secured to the cylinder via flanges extending transversely to the longitudinal axis of the cylinder. The line balance coil arrangement is preferably secured to the coil support of the deflection coils. It may be integrated with a special holder in which the arrangement may be clamped. This is a practical system for every embodiment. The magnet core in the coil cylinder is preferably movably arranged. The invention also relates to a practical method of producing line balance coils. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter. In the drawings: Fig. 1 is an electric circuit diagram of a circuit of line deflection coils and a line balance coil; Fig. 2 is an electric circuit diagram of a line balance coil; Fig. 3 is a perspective elevational view of an embodiment of a deflection unit according to the invention; Fig. 4 is a perspective elevational view of a line balance coil mounted on a PCB in accordance with the state of the art; Fig. 5 is a perspective elevational view of an embodiment of a line balance coil arrangement without coils according to the invention; Fig. 6 shows diagrammatically an adjustable magnetic core arrangement for use in a line balance coil; Fig. 7 is a perspective plan view and Fig. 8 is a perspective bottom view of an embodiment of a line balance coil arrangement according to the invention, with an adjustable magnet core but without coils; Fig. 9 is a plan view of a sheet of strip material having a repetitive pattern of connection strips and being combined with a coil cylinder arrangement of the type as shown in Figs. 7 and 8; Fig. 10 is a plan view of a sheet having an alternative pattern of connection strips, combined with line balance sub-coils shown diagrammatically; and Fig. 11 A shows a circuit diagram and Fig. 1 IB is an elevational view of the construction showing the connection of line deflection coils, a line balance coil and possible further features. Fig. 3 shows an embodiment of a deflection unit 5 (deflection yoke) comprising a pair of line deflection coils la, lb, a pair of field deflection coils 2a, 2b, in this case wound on a ferrite ring core 3, and a hollow coil support 4 (support frame) of synthetic material. The deflection unit 5 is provided with a line balance coil arrangement 10 comprising a coil cylinder 8 on which two line balance sub-coils 7a, 7b are arranged. The coil cylinder 8 is secured to a rear flange 6 of the coil support 4. Line deflection coil la has connections A and B, line deflection coil lb has connections C and D and the line deflection coils la, lb are arranged in an electric circuit with the line balance coil 10 in the manner as shown in Fig. 1. The electric circuit diagram of the line balance coil 10 is shown in Fig. 2. Line balance sub-coil 7a has connections F and G and line balance sub-coil 7b has connections H and I. Fig. 4 shows a conventional line balance coil arrangement 11 mounted on a PCB 12. In contrast, the connections (sealing pins) and the function of the PCB are integrated, in accordance with the invention, in the line balance coil. Fig. 5 shows a first embodiment. Coil cylinder 53 has 4 cross-flanges 54- 57 in which connection strips 58-61 are integrated. These are formed in a manner to be described hereinafter from a leadframe which is enveloped with synthetic material in a mould. In this case, the connection strips 58-61 have bent ends 62-65 intended to seal the ends of the line balance sub-coils to be wound between the flanges 54-55 and the flanges 56 and 57. The coil cylinder 53 is hollow and intended to comprise a self-tapping control core assembly 26 which is movable in the longitudinal direction and is of the type shown in Fig. 6. (The ferrite magnet core is denoted by the reference numeral 26', the synthetic envelope having a tapered cross-shaped recess is denoted by 26".) Fig. 7 shows an alternative embodiment of a line balance coil arrangement 27 in which a magnet core 26 (enveloped with synthetic material) is arranged in a coil cylinder 28. Arrangement 27 has four synthetic material cross-flanges 44-47 to which three synthetic material supporting members 29-31 are secured which extend parallel to the longitudinal axis of cylinder 28. As is shown in Fig. 8, metal connection strips 32-37 are integrated with the supporting members 29-31, which strips have bent ends 38-41 intended to seal the ends of the line balance sub-coils to be wound between the flanges 44 and 45 and the flanges 46 and 47. Fig. 9 is an elevational view of a sheet of strip material 42 in which a repetitive pattern of coherent connection strips to be punched loose at a later stage is formed, for example by means of etching. The Figure particularly shows how such a sheet with a connection strip pattern is joined with a line balance coil 43. By enveloping the strip pattern with a synthetic material, punching loose and bending of the connection strips, the construction shown in Figs. 7 and 8 is obtained. In its turn, this construction is secured to the coil support of a deflection unit and the connections intended for this purpose are connected to the lead-outs of the line deflection coils and to ground. Securing may be realized in different manners, for example by means of synthetic material supports secured to the coil support. In "double mussel" deflection units, it is practical to secure the line balance coil to the front flange of the coil support, in contrast to securing it to the rear flange (cf. Fig. 3) as is common practice in hydride coils. Various options can be realized with the novel line balance coil design as shown in Fig. 10: 1. Line balance control. The end lead-outs of the line deflection coil are sealed to the pins 11 and 13. The start lead-outs of the line deflection coil are sealed to the pins 8 and 16. Coil LI is wound between the pins 20 and 21, Coil L2 is wound between the pins 22 and 23. A controllable ferrite core is inserted into the line balance coil. 2. Line balance control using ringing damping. Similarly as option 1 with a tap drawn from the line deflection coil (via a winding process or welded) and sealed to pin 10 for the one line deflection coil and pin 14 for the other line deflection coil. A resistor is connected between pin 10 and pin 9 and between 14 and pin 15. A capacitor is connected between pin 9 and pin 8 and between pin 15 and pin 16. The resistor and the capacitor may also be interchanged because they are in series. 3. Line balance control using ringing damping and VLMF (Very Low Magnetic Field, shielding of magnetic fields from within the tube). Similarly as options 1 and 2 with VLMF connection to pin 18 via a coil (PCB mould or loosely wound) connected to pin 17 or 19. The circuit diagram is shown in Fig. 1 1 A while Fig. 1 IB is a plan view of the line balance coil with connection pins. 4. No line balance control. The end lead-outs of the line deflection coil are sealed to the pins 11 and 13. The start lead-outs of the line deflection coils are sealed to the pins 8 and 16. Connection pieces 25 and 25' are not cut loose. The coils LI and L2 are thus not wound and the ferrite core is not provided. 5. It will be evident that various other combinations based on these 4 options are possible. It is particularly possible to realize other connection patterns as desired by interchanging the leadframes in a mould. In summary, the invention thus relates to a deflection unit having a hollow synthetic material coil support within which a line deflection coil system is arranged, which line deflection coils are connected in an electric circuit to a line balance coil arrangement comprising a cylinder which is provided with two sub-coils and within which a magnet core is movably arranged. The coil cylinder is secured to the coil support and is provided with an arrangement of metal (connection) strips which ensure a direct connection between the balance coil lead-outs, the line deflection coils and a tap.

Claims: CLAIMS: 1. A deflection unit within which a line deflection coil system is arranged, said line deflection coils being connected in an electric circuit to a line balance coil arrangement comprising a cylinder which is provided with two sub-coils and within which a magnet core is arranged, characterized in that the coil cylinder is provided with an arrangement of metal (connection) strips which ensure a direct connection between the balance coil lead-outs, the line deflection coils and a tap. 2. A deflection unit as claimed in Claim 1, characterized by a first strip, one end of which is sealed to a lead-out of one sub-coil and the other end of which is connected to one line deflection coil, a second strip, one end of which is sealed to a lead-out of the other sub-coil and the other end of which is connected to the second deflection coil, and a third strip having three ends, the outer ones of which are sealed to the remaining lead-outs of the sub-coils and the central one constitutes a tap. 3. A deflection unit as claimed in Claim 1 , characterized in that the coil cylinder is provided with a plurality of supporting members which are integrated with an arrangement of metal (connection) strips formed from a leadframe. 4. A deflection unit as claimed in Claim 3, characterized in that a plurality of strips is bent. 5. A deflection unit as claimed in Claim 3, characterized in that the supporting members extend transversely to the longitudinal axis of the cylinder. 6. A deflection unit as claimed in Claim 3, characterized in that the supporting members extend parallel to the longitudinal axis of the coil cylinder and are secured to the cylinder via flanges extending transversely to the longitudinal axis of the cylinder. 7. A deflection unit as claimed in Claim 6, characterized in that the cylinder is provided with four cross-flanges, the outer one of which is secured to two supporting members facing away from each other and the inner one is secured to a third supporting member, while a sub-coil is wound on the cylinder between each one of the outer pairs of cross-flanges. 8. A deflection unit as claimed in Claim 1, characterized in that the magnet core is movably arranged within the coil cylinder. 9. A deflection unit as claimed in Claim 1, characterized in that the deflection unit has a coil support, and in that the line balance coil arrangement is secured to said coil support. 10. A method of producing a line balance coil support, characterized in that, in a sheet of strip material having a repetitive pattern of coherent connection strips, said strips are enveloped in a mould with the support material, while the resultant coil supports are punched loose at a later stage of the method.

Inventors: GRUBBEN ANTONIUS PIERRE MARIE, VAN DE MEERAKKER JACOBUS JOHAN, GRUBBEN, ANTONIUS, PIERRE, MARIE, VAN DE MEERAKKER, JACOBUS, JOHANNES, MARIA
Applicants: PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, PHILIPS ELECTRONICS N.V.
Application year: 1996
Main classification: H01J29
IPC codes: H01J9, H01J29