EP0326440B1 - Machines for inserting a cathode in a CRT gun - Google Patents

Description

The present invention relates to cathode implantation machines in a cathode ray tube barrel, more particularly an improvement to the machine described in French patent application No. 87 03922 (EP-A-288 335, published on October 26, 1988) filed March 20, 1987 in the name of the plaintiff.

The machines currently used for inserting cathodes into the electronic cannon of a cathode ray tube comprise, for measuring the distance between the active face of the cathode and the grid G1 or, where appropriate, the grid G2, complex devices, not very rapid. , and with difficulty keeping the necessary precision.

In fact, the machines position the cathode relative to the first grid or grid G1 by first inserting a probe of fixed length between the cathode and the grid G1, the cathode being mounted on a fixed support and the barrel being mounted on a support. mobile driven by a roller cooperating with the groove in cam profile of a parent screw itself driven by a stepping motor.

A first stage of this groove determines the position of measurement and of adjustment in position of the cathode, then the barrel is moved back, the probe released, and the barrel advanced by a distance equal to that from which it moved back, increased by the length of the probe. We thus arrive in the welding position of the cathode in the eyelet of the barrel, this position also being determined by a bearing in the groove. Thus all modifications to the machine setting require dismantling the probe and re-machining it to a new dimension. On the other hand, the drive device constituted by a lead screw cooperating with a roller is imprecise: the groove of the lead screw must be free of any dust or debris, which is difficult to obtain in an industrial environment. On the other hand, even if the stepping motor stops precisely in the desired angular position, the coupling device with the lead screw which drives it has games that are difficult to take into account. The efforts exerted on the roller both by the barrel carrier carriage and by the mother screw, the play in this transmission of movements is passed on to the carriage. In addition, if the cathode grommet is off-center, the feeler may deform the grommet, or else the feeler must be made of deformable material.

To overcome these drawbacks, a machine has been proposed in French patent application No. 87 03922 for implanting a cathode in an eyelet of an electronic gun comprising a mobile support device for the gun moving in the direction of its axis, this device being movable between two fixed positions, and a probe with retractable rod, movable perpendicular to the axis of the barrel.

In the case of the implantation machine described above, when the barrel support device is placed in its position furthest from the cathode, the retractable rod probe is inserted between the barrel and the cathode. The probe rod is then brought into abutment against the grid G1 and one can thus determine the distance between the probe and the active face of the cathode. Thus, the active face of the cathode is positioned so that, when the probe is removed and the barrel support device is brought into its second fixed position, the desired distance between the active face of the cathode and the grid is obtained. G1. This machine for implanting a cathode in the eyelet of an electronic gun therefore allows exact positioning of the cathode relative to the grid G1, however it does not take into account the positioning of the grid G2 nor the spacing between grid G1 and grid G2. However, for correct operation of a cathode ray tube, the distance between the grids G1 and G2 must be between specific values so as to obtain a precise cut-off.

The object of the present invention is to remedy these drawbacks by proposing a cathode implantation machine in a grommet of a cathode-ray tube making it possible to carry out in a single measurement the position of the grid G1, of the grid G2 and of the cathode.

Consequently, the subject of the present invention is a cathode implantation machine in a cathode ray tube cannon eyelet of the type comprising a support device for the movable barrel along the axis of the barrel, a cathode support device positioning the cathode according to the axis of the barrel and a probe with retractable rod cooperating with a first detector giving the position of the cathode when the rod is in abutment on the grid G1, said probe being movable perpendicular to the axis of the barrel, characterized in that it comprises in addition a calibrated length rod coming to bear on the grid G2 and emerging on the side opposite to the eyelet, a second detector recording the position of the rod and a control device determining from the measurements made by the two detectors, the displacement of the barrel support device.

According to a preferred embodiment, the first detector is constituted by an electromagnetic sensor while the second detector is constituted by a sensor with optical aiming developing a measurement signal.

On the other hand, the probe is mounted axially movable at the end of an L-shaped arm carrying at its other end the second detector, said arm being displaceable perpendicular to the barrel / cathode axis.

According to another characteristic of the present invention, the cathode support device is fixed along the axis of the barrel but movable substantially perpendicular to the axis of the barrel.

In addition, the probe with retractable rod is preferably produced as described in French patent application No. 87 03922. Thus the probe has a cylinder in which a piston moves on which is fixed a probe rod opening at one end of the probe. cylinder and intended to come into contact with the grid G1 of the barrel, the other end of the cylinder comprising a detector detecting, when the probe is arranged in the axis of the barrel and that the piston is in abutment against the end by which leaves the rod, the position of the active face of the cathode also positioned in the axis of the barrel.

FR-A-2 205 738 describes a cathode implantation machine in a cathode ray tube barrel eyelet comprising a support device for the movable barrel along the axis of the barrel, a cathode support device positioning the cathode along the axis of the barrel and a retractable rod probe cooperating with a first detector giving the position of the cathode when the rod is in contact with the grid G1, the probe being movable perpendicular to the axis of the barrel.

RCA Technical Notes, No. 1322, 12/22/82, pages 1 and 2, Princeton, US; R.Schlack et al .: "G1-G2 compensating cathode inserter" describes a cathode insertion device in which account is taken of the spacing between grid G1 and grid G2 for the exact positioning of the cathode relative to to grid G1. A probe is introduced into the openings of the grids G1 and G2.

• la figure 1 est un schéma simplifié d'une machine conforme à la présente invention, et
• la figure 2 est une vue en coupe du palpeur utilisé dans la figure 1.

Other characteristics and advantages of the present invention will appear on reading the detailed description of an embodiment, made with reference to the attached drawings in which:

• FIG. 1 is a simplified diagram of a machine in accordance with the present invention, and
• FIG. 2 is a sectional view of the probe used in FIG. 1.

To simplify the description, in the figures the same elements have the same references.

Although FIG. 1 represents a simple gun, it is understood that, for a person skilled in the art, the invention can also be applied to a triple gun for trichrome cathode ray tube.

There is shown in Figure 1 a schematic view of an implantation machine according to the present invention. This machine includes an electron gun support device 1 for a cathode ray tube movable along an axis 2, a probe 4 with retractable rod, a cathode support device 5, a calibrated rod 7, position detectors 8 and 9 and a control device 10 determining from the measurements made by the two detectors the displacement of the gun support device.

The barrel 3 of the cathode-ray tube used in the embodiment shown in FIG. 1 is made up of four grids referenced G1, G2, G3 and G4 fixed on two ceramic pieces 11, 12, generally called "beading". It is understood that the invention can be applied to cannons comprising a different number of grids, in particular to cannons with six grids. The barrel 3 also includes an eyelet 13 for the cathode. The machine of the invention is used to introduce the cathode 6 into the eyelet 13 so that the anterior face 6a of the cathode, that is to say the face on which the emissive substance is applied, is located a determined distance from grid G1. Once the cathode is positioned, it is then welded into the eyelet 13. The cathode 6 is mounted on a support device 5 which is fixed according to axis 2 but mobile substantially perpendicular to axis 2 to be able to position the cathode along this axis.

The barrel is deposited on a support device 1 movable parallel to the axis 2. The barrel support device consists of a sleeve 14 of outside diameter slightly less than the diameter of the electron passage holes of the grids G3 and G4 provided with one of its ends of a flange 15. The flange 15 is integral with a movable bearing 16 moving on a fixed guide 17 and parallel to the axis 2. The bearing 16 is driven by a motor not shown.

The generally cylindrical feeler 4 is mounted at the end of a support arm 18 movable perpendicular to the axis 2 between a measurement position for which the feeler axis coincides with the axis 2 as shown in the figure 1 and a release position. As shown in FIG. 1, the arm 18 is slidably supported by a U-shaped arm 19 carrying at its two ends sleeves 20 and 20 ′ positioned between two stops 21 and 21 ′ secured to the arm 18 with interposition of a spring 22 between the sleeve 20 and the stop 21. The arm 19 can be moved perpendicular to the axis 2 using a spring device 23 or other similar device. On the other hand, the probe 4 essentially comprises a retractable measuring rod 24 driven by a piston 25 moving in the chamber formed by the cylindrical body 26 of the probe. The probe further comprises at its other end a detector device 9 facing, in the measurement position, the active surface 6a of the cathode 6. In the release position, the measurement rod 24 of the probe is retracted. When the probe 4 arrives in the measurement position, its rod is extended to come into contact with the first grid G1 of the barrel 3.

The probe used in the context of the present invention may be identical to the probe described in French patent application No. 87 03922. This probe is shown in detail in Figure 2. In this figure the probe is shown in the measurement position . The feeler device described here is of the control type pneumatic, but it is obvious to a person skilled in the art that the invention is not limited to such a probe and that any probe fulfilling the same function, namely using a retractable rod for measuring the distance between the first grid of the barrel and the cathode, may be suitable. Such probes can be electromagnetic, hydraulic, etc.

The body 26 of the probe 4 is mounted movable in axial translation relative to the support arm 18 by means of a ball bearing 27. This translation is limited on one side by a shoulder 28 of the body 26 and on the other side by a spring with flange 29 disposed around the body 26 and pressing against a cap ring 30 screwed to the end of the body 26. The cap ring 30 allows the rod 24 to pass in leaktight manner and acts as an adjustable stop for the piston 25. The other end of the body 26 is closed. A coil spring 31 is disposed inside the body 26 pressing against the closed end and prevents the piston 25 from abutting too abruptly against this end in its withdrawal movement.

The body 26 of the probe is pierced, near the end on which the spring 31 is supported, with a radial hole 32 connected to a pneumatic control device not shown. The closed end of the body 26 has a cavity 33 in which is mounted a detector, namely an electromagnetic sensor 9 used to determine the distance 6a-G1. In fact, the sensor 9 will determine the penetration of the rod 9a urged by the spring 9b against the front face 6a of the cathode. This type of detector is known per se and will not be described in more detail. Other types of detectors can be used, in particular devices of the type described in patent application FR-87 03922.

As shown in FIG. 2, in the measurement position the piston 25 abuts against the cap 30, its rod 24 being in abutment against the first grid G1 of the barrel 3. When the probe is in the position shown in FIG. 1 with its rod 24 resting against the grid G1, it constitutes a calibrated rod and thus allows the determination of the distance of the cathode relative to the grid G1 by using the electromagnetic sensor 9. The information coming from the sensor 9 is sent to the control device 10 which develops a command positioning the stop 41.

The probe is actuated by a control device which may be of the type described in French patent application No. 87 03922. Consequently, this pneumatic type control device will not be described again here.

On the other hand, in accordance with the present invention a rod 7 whose diameter is less than the internal diameter of the sleeve 14 and whose length is greater than the distance between G2 and the end of the barrel on the side of the grids G4 or G6, is movable along axis 2. The rod 7 is preferably introduced into the barrel when the sleeve 14 is itself introduced into the barrel, the flange 15 being in abutment against the beading 12. This rod 7 is actuated by a mechanism appropriate automatic (not shown). A spring 40 or similar device then applies the rod against the grid G2.

A position detector 8, for example an optical sighting sensor producing an electrical measurement signal, determines the position of the free front face 7a of the rod 7. The electrical measurement signal is sent to a control and display device 10 which also receives the signal emitted by the detector 9. In accordance with the present invention the detector 8 is placed at the end of the arm 18 opposite the end supporting the probe 4. It determines the position of the face 7a of the rod 7 when the barrel 3 is in the retracted position P1 as shown in FIG. 1, so as to allow the introduction of the probe 4 into the measurement position. As the detector 8 and the probe 4 are arranged at each end of the same arm 18, the two detectors 8 and 9 will therefore be in position aligned along the axis 2.

The electrical signals produced by the detectors 8 and 9 are sent to a control and display device 10 which determines from these signals the value of the displacement of the stop 41. This stop 41 in fact determines the final position of the support device barrel, position for which cathode 6 occupies its normal position in the eyelet 13, that is to say when the face 6a of the cathode is at the desired distance from the grid G1. In fact, the control device 10 sends a control signal to the motor 42 which moves the stop.

With the machine described above, the standard position of the abutment is first determined for a barrel and a reference cathode which will have been measured and chosen beforehand. The standard distance Y of displacement of the barrel support device is thus obtained, which gives the standard position of the stop.

When using any of the above-described machines cannons and any cathodes, the detectors 8 and 9 measure deviations X1 and X2 respectively from the measurements previously made with the reference elements. These deviations can be positive or negative and determine the variation of the stop position.

It is then easy for a person skilled in the art to produce a control device 10 controlling the motor 42 so that it performs a movement corresponding to this variation.

In the machine described above, the detectors 8 and 9 take into account the variations in distance between the grid G1 and the grid G2 and allow positioning of the cathode relative to the grid G1 which corresponds to a value determined in advance.

Thus, the final positioning of the cathode takes place by a displacement of the beading of a magnitude x, such that:
x = β - (desired final distance KG1) - f (G1G2)
or
β = value measured between the lower edge of G1 - and the face 6a of the cathode in the measurement phase
f (G1G2) = linear function dependent on the type of gun used (for example with 4 grids or 6 grids).

• les sensibilités d'un canon 6 grilles sont :
     + pour KG1, une valeur γ de variation de tension de cut-off
     + pour G1G2, une valeur δ de variation de tension de cut-off
• une mesure de G1G2 supérieure de 1 millième de pouce (soit 2,54 millièmes de centimètre) à la valeur nominale impliquera donc de positionner la cathode à une distance d'environ δ / γ millième de pouce (soit 2,54 δ / γ millièmes de centimètre) inférieure à la valeur nominale.

For exemple :

• the sensitivities of a 6-grid gun are:
  + for KG1, a cut-off voltage variation value γ
  + for G1G2, a value δ of cut-off voltage variation
• a measurement of G1G2 greater than 1 thousandth of an inch (i.e. 2.54 thousandths of a centimeter) at nominal value will therefore involve positioning the cathode at a distance of approximately δ / γ thousandth of an inch (i.e. 2.54 δ / γ thousandths of centimeter) lower than the nominal value.

Of course the machine of the invention further comprises a device for welding the cathode 6 in the eyelet 13, for example a device for welding by laser beam, this welding device is well known per se and does not form part of the the invention will not be re-described.

Claims (7)

1. Device for installing a cathode (6) in an eyelet (13) of a cathode ray tube gun (3), also including at least a first grid (G1) and a second grid (G2), the said device comprising:

   - a mobile gun support device (1) parallel to the gun axis (2) between a withdrawn position in which the gun is moved away from the cathode, and a final position in which the cathode is in its normal position in the eyelet;

   - a cathode support device (5) fixed along the axis of the gun positioning the cathode on the gun, but capable of moving perpendicularly to the gun axis;

   - a sensor (4) capable of moving perpendicularly to the gun axis between a measurement position in which the sensor axis coincides with the gun axis, and a released position, the said sensor (4) including a retractable rod (24) at one end which, in the measurement position, touches the first grid but does not penetrate into it, and which is retracted in its released position, and a first detector (9) at its other end which senses the cathode emitting surface(6a) when in the measurement position;

   - a gauge (7) with a calibrated length, which touches the second grid without penetrating it and which extends towards its front surface (7a) in a direction moving away from the eyelet;

   - a second detector (8) that determines the position of the front surface of the gauge (7) with the gun support device in the withdrawn position; and

   - a control device (10) that receives signals emitted by the first and second detectors (9, 8), to determine the final position of the gun support device, in which the cathode emitting surfaces are located at a required distance from the first grid.
2. Device according to claim 1, wherein the first detector (9) consists of an electromagnetic sensor (9).
3. Device according to claim 1 or 2, wherein the second detector consists of an optical sight sensor (8) generating a measurement signal.
4. Device according to any one of claims 1 to 3, wherein the sensor (4) is mounted so that it can move axially on the end of an L-shaped arm (18), and bearing the second detector (8) at its end, the said arm moving perpendicularly to the gun axis.
5. Device according to any one of claims 1 to 4, wherein the gun support device (1) comprises a sleeve (14) with a diameter less than the diameter of the grid holes other than the first two holes, this sleeve comprising a collar (15) bearing on the pearling (11, 12) when the sleeve fully inserted in the gun, this collar being attached to the device controlling the movement (16, 17) of the gun support device.
6. Device according to any one of the claims 1 to 5, wherein the sensor (4) comprises a cylinder (26) within which a piston (25) moves, and on which the sensor rod (24) project through one end of the cylinder and will come into contact with the first gun grid G1, the other end supporting the second detector (9) that, when this sensor is placed along the gun center line and when the piston is in contact with the end through which the rod projects, determines the distance of the cathode, placed along the gun axis, from the active face (6a).
7. Device according to any one of claims 1 to 6, wherein the displacement distance of the gun support device (1) is determined by an adjustable stop (41) controlled by the control device (10).

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