EP0142200A2 - Voltage control device for cathode-ray tube electrodes - Google Patents

Abstract

The invention relates to potentiometers for adjusting the cathode ray tube electrode for color television. In known voltage generating devices, a special potentiometer capable of supporting several kilovolts is used to supply an adjustable voltage. According to the invention, the potentiometer track is produced by means of a resistive layer (2) disposed inside the same of the voltage outlet pipe (10), and the potentiometer cursor by means of the end. high voltage cable (9) introduced into said pipe and which can slide in this pipe to adjust the tension.

Description

The invention relates to an adjustable voltage generator device for supplying at least one electrode of a cathode ray tube, device comprising a transformer provided with a winding to supply at least one voltage, and a hollow part called a "pipe" in which is introduced at least one electric cable and in which the latter is connected with the winding.

The invention finds its main application in color television receivers.

In known voltage generating devices, a special potentiometer capable of supporting a voltage of several kilovolts across its terminals is used to supply the adjustable voltage. Such a potentiometer is present, for example, in the catalog of The PHILIPS Company under the name "FOCUS POTENTIOMETER UNIT".

Such a potentiometer is bulky, difficult to connect, and above all expensive to manufacture because of the insulation constraints required by the high voltages present.

The invention provides a solution to avoid the use of such a specific element, its attachment to the transformer and its connection to the voltage generator element.

The generating devices include a transformer provided with a winding to supply a voltage, and a hollow part called a "pipe" into which an electric cable is introduced and in which the latter is connected to the winding.

The device according to the invention is remarkable in that inside said pipe is arranged at least one resistive layer, one end of which is connected at a point in the winding, in that the electric cable is provided with means for making contact with said layer, and in that the insertion of the cable into the pipe is adjustable.

In the device according to the invention, the potentiometer track is formed by means of a resistive layer disposed inside the very outlet pipe of the concentration voltage, and the potentiometer cursor by means of the end of the cable. high tension introduced into the said pipe being able to slide in this pipe to regulate the tension.

In order to avoid the use of an additional resistance, the other end of the resistive layer is advantageously connected to another point of the winding.

Advantageously, the means for making contact with the layer are constituted by the end of the conductive core of the cable folded over its insulating sheath.

Thanks to the device according to the invention, it is possible to provide an adjustable high voltage by using only extremely simple and inexpensive means.

In addition, the device according to the invention advantageously applies to the supply of the concentration voltage as well as to the bias voltage of the second grid of the cathode-ray tube, and for this purpose its hollow part comprises two housings, for two cables, Housing each provided with a resistive layer.

• Les figures 1A et 1B représentent une vue latérale et une coupe d'un transformateur utilisé dans l'invention.
• Les figures 2A et 2B sont deux schémas électriques de branchement à l'enroulement.
• Les figures 3A et 3B représentent en perspective coupée deux exemples de réalisation de La pipe selon L'invention.
• La figure 4 représente une barrette isolante recouverte d'une couche résistive.
• Les figures 5A et 5B représentent en perspective des moyens pour assurer le contact entre le câble et La couche résistive.
• Les figures 6A, B, C, et D iltustrent différents exemples de réalisation de moyens de blocage du câble.
• Les figures 7A à 7C sont respectivement une vue en perspective, une coupe transversale et une coupe longitudinale d'un mode de réalisation particulier de l'invention où La partie creuse comporte deux Logements.
• Les figures 8A et 8B représentent en perspective à divers stade de fabrication, des barrettes munies de couches résistives.
• La figure 9 est un schéma de branchement pour deux électrodes d'un tube cathodique.

The description which follows, with reference to the appended drawings given by way of nonlimiting examples, will make it clear how the invention can be implemented.

• Figures 1A and 1B show a side view and a section of a transformer used in the invention.
• Figures 2A and 2B are two electrical diagrams of connection to the winding.
• Figures 3A and 3B show in cut perspective two embodiments of the pipe according to the invention.
• FIG. 4 represents an insulating strip covered with a resistive layer.
• FIGS. 5A and 5B show in perspective means for ensuring contact between the cable and the resistive layer.
• FIGS. 6A, B, C, and D iltustrent different exemplary embodiments of cable locking means.
• FIGS. 7A to 7C are respectively a perspective view, a cross section and a longitudinal section of a particular embodiment of the invention where the hollow part comprises two housings.
• FIGS. 8A and 8B show in perspective at various stages of manufacture, bars provided with resistive layers.
• Figure 9 is a connection diagram for two electrodes of a cathode ray tube.

In Figure 1, a high voltage television transformer is shown. The latter is usually provided with several windings, or windings, providing various voltages, placed around a ferrite core 8. the winding 20 which provides the focusing voltage is shown. The transformer comprises a prominent and hollow part 10 called a "pipe", into which an electric cable 9 is introduced and into which the latter is placed in connection with the winding 20.

Inside the tadite pipe 10, a resistive layer 2 is arranged, one end of which is connected by the connection 7 to a point of the winding. The electric cable 9 is provided with means for making contact with said layer and its insertion into the pipe is adjustable by hand or by some mechanical means which is easy to carry out.

The other end of the resistive layer 2 is connected, for example by means of a clip 12, to a conductor 11. FIG. 2A, where we find the winding 20 and The resistive layer 2, shows that said other end is connected by the conductor 11 to a heel resistor 23, itself connected to ground.

This diagram is the one usually used. It also includes rectifier diodes not described here, which can be connected in different ways, described for example in the book "The new guide to color television" published by CHIRON in Paris, pages 229 to 240. These diodes are generally incorporated in the molding of the winding, for example in the manner described by patent FR 2 146 419. A diode can thus be placed in series in connection 7.

The diagram in Figure 2B shows another possibility of connecting the potentiometer. This possibility is not used in the prior art because it requires the presence of a second pipe to ensure the connection, at point 22, of the other end of the potentiometer. This connection is on the other hand advantageous in the context of the invention since it makes it possible to remove the conductor 11 and the resistance 23. The two ends of the resistive layer, located in the same pipe 10, are connected to the sockets 21, 22 of the 'winding.

The pipe of Figure 3A has a resistive layer 2 cut directly to the interior of the pipe. This deposition can be carried out under plasma, this well-known technique making it possible to metallize inaccessible surfaces. On the two ends 5, 6 a conductive layer is deposited by masking the central part of the layer 2 during the deposition. The conductive pads 5, 6 allow the connection with, respectively, the connection 7 and the clip 12.

The pipe of Figure 3B is provided with a prefabricated internal part 100. This piece has a rai nure 4 in which is fixed an insulating strip covered with a resistive layer.

FIG. 4 represents such a bar covered with the resistive layer 2 on one side, a conductive layer 1, 3 being deposited at each end. These layers are preferably deposited by screen printing in a thick layer on a ceramic substrate which has a large quantity of bars and which is then cut into unitary bars. On the end layers 1 and 3, connections 7 and 70 are fixed, the connection 70 being for example folded behind the bar. The bar is then fixed in the part 100, the connections 7, 70 passing through the holes 24, then the connections 7, 70 are connected to the winding 20 and, finally, the whole of the winding and the part 100 is overmolded to form a block provided with the pipe 10.

The cable 9 of FIG. 5A is provided at its end with a ferrule 14 welded to the central conductor 13 of the cable. This tip comprises one or more stamped cutout (s) each constituting an elastic blade 25 intended to ensure good contact with the resistive layer. In a simplified version represented by FIG. 5B, the end of the rigid central conductor 13 of the cable is folded over its insulating sheath to ensure contact with the resistive layer. This arrangement is adapted to the pipe shown in FIG. 3B, the groove 4 then being deeper than the thickness of the bar, so that after fixing it in the bottom of the groove, the resistive layer remains in shrinkage relative to the inner wall of the pipe, thus still constituting a groove in which the penetration of the end 13 of the cable into contact with the bar, thus preventing the cable from rotating around its axis LongitudinaL. Instead of a narrow bar housed in the groove, it is also possible to use a relatively wide bar, housed in a suitable recess next to the housing intended for the cable, with a slot between said recess and said housing, slot through which passes the conductive end of the cable, such an arrangement is represented by FIGS. 7A, B, C which will now be described.

To provide both the concentration voltage and the second grid voltage of a color television cathode ray tube The pipe seen in perspective in FIG. 7A comprises two housings for two cables 9, 29, housings each provided with a resistive layer.

This arrangement makes it possible to carry out the electrical diagram shown in FIG. 9. The winding 20 supplies a voltage of approximately 8 kV by a conductor 33 at one end of a resistive track 2 on which the cable 9 contacting the electrode contacts focusing, track followed by a track 23 forming resistance-heel, and a resistive track 28 on which the contactor The cable 29 supplying the second grid of the cathode ray tube. the end, opposite to track 23, of track 28 is connected by a conductor 36 to an outlet of the transformer winding, outlet providing approximately 0.5kv; it could also be brought back to ground via a heel resistance.

Figure 7B is a cross section through the pipe of Figure 7A. It shows two cables 9, 29 in two cylindrical housings, and two bars 31, 32 with which the ends respectively 13, 30 of the cables 9, 29 are in contact. The bars 31, 32 are placed together in a suitable recess 27 placed between the two housings for the cables, and passages parallel to the axes of the cables make said housings communicate with said recess 27 by allowing the ends of the cables 13, 30 to pass. Of course a contact tip like that shown in Figure 5A could as well be used here.

FIG. 7C, which is a perspective view in section along C of the pipe of FIG. 7A, makes it possible to perfectly understand the arrangement of the cables 9, 29, and bars 31, 32.

FIG. 8A represents bars 31 and 32 seen from the side which carries the resistive tracks 2 and 28 and conductive connecting tracks 33 to 36. The bars are cut from an alumina plate and the tracks are produced according to the so-called "technique". in thick layers "by screen printing and baking.

Track 28 is wider than Track 2, because for the same Cable Sliding Length, it must provide a voltage variation of approximately 400 volts, while Track 2 provides a variation of approximately 2 kilovolts. The resistance-heel portion 23 which extends Track 28 is offset laterally so that, in the event of insufficient penetration of the cable, the latter is no longer in contact with the resistance, so that the second grid cannot be brought to too high a voltage.

Before being placed in the pipe 10, the plate 32 is turned back to back against the plate 31, as indicated by arrow 37, and one then obtains the set of bars represented by FIG. 8B. A clip 26 provides the electrical connection between the conductive tracks 34 and 35 of FIG. 8A, and the tracks 33 and 36 are connected to taps of the winding as explained above with reference to FIG. 9.

FIG. 6A represents the outer end of a pipe provided with slots 15 around a cable passage. The slots 15 allow tightening by constriction. One uses for example a plug 17 shown in Figure 6B, screwed onto the thread 16 of the pipe, so as to cause tightening. One can also use a ring 18 shown in Figure 6C, forced into the frustoconical end of the pipe. It is also possible to use a transverse screw 19, as shown in FIG. 6D, to tighten the cable. Although Figures 6A and D show a pipe to a cable, it is obvious that the means described with reference to these figures and more particularly to FIG. 6D apply equally well to a pipe with two cables.

Other variants for producing the resistive layer or the means for making contact, or for blocking the cable, can of course be imagined without departing from the scope of the invention. For example, it is possible to use to block the cabled cables, a wedge-shaped piece which is slid until locked between the two cables, or between a cable and a stop provided on the end of the pipe. It is thus possible to replace part of the conductive track 36 (FIG. 8A) with a resistive track so as to produce a heel resistance.

Claims (10)

1. Adjustable voltage generator device for supplying at least one electrode of a cathode ray tube, device comprising a transformer provided with a winding to supply at least one voltage, and with a hollow part (10) called "pipe" in which is introduced at least one electric cable (9) and in which the latter is connected with the winding, characterized in that inside said pipe is arranged at least one resistive layer (2), one of which end is connected to a point of the winding (20), in that the electric cable is provided with means for making contact with said layer, and in that the insertion of the cable into the pipe is adjustable. 2. Device according to claim 1, characterized in that the means for making contact with the layer consist of the end (13) of the conductive core of the cable folded over its insulating sheath. 3. Device according to claim 1, characterized in that the means for making contact with the layer consist of a tip (14) provided with at least one elastic blade. 4. Device according to any one of the preceding claims, characterized in that the resistive layer is arranged in a groove in the wall of the pipe. 5. Device according to any one of the preceding claims, characterized in that the other end of the resistive layer is connected to another point of the winding (20). 6. Device according to any one of the preceding claims, characterized in that at least one insulating bar on which a resistive layer is deposited is placed in said pipe. 7. Device according to any one of claims 1 to 5- characterized in that the resistive layer is deposited directly on the inner wall of the pipe. 8. Device according to any one of the preceding claims, characterized in that its hollow part comprises two housings, for two cables (9, 29), housings each provided with a resistive layer, providing respectively the concentration voltage and the voltage second grid of the cathode ray tube. 9. Device according to any one of claims 1 to 6, characterized in that its hollow part comprises two housings, for two cables, housings each provided with an insulating strip (31, 32) on which is deposited a resistive layer (2, 28), and in that these strips are arranged back between the two housings and their resistive layers are connected in series. 10. Device according to any one of the preceding claims, characterized in that it is provided with cable locking means.

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