US3487251A - Parallelogram mounting fixture for shadow mask - Google Patents

Description

5 j P. s. .LBARTEN ETAL 3,487,251

PARALLE OGRAM MOUNTING FIXTURE FOR SHADOW MASK Filed Now-14; 1967 PIE-T HANS H-SCH K- W AGE United States Patent ()flice 3,487,251 Patented Dec. 30, 1969 Claims priority, application Netherlands, Nov. 19, 1966,

6616317 Int. "Cl. H01j 29/ 46' US. Cl. 313-85 6 Claims ABSTRACT on THE DISCLOSURE A parallelogram mounting fixture is provided between the shadow mask of a color television tube and the wall which is adapted to twist upon increase in dimension of the shadow mask relative to the tube envelope so as to produce an axial movement of the shadow mask and thereby maintain the mask openings in register with electron beams.

The invention relates to a cathode-ray tube for displaying colored television images, in which a substantially rectangular color selection electrode is arranged in the proximity of the display screen and is supported in the tube by means of at least three preferably strip-shaped supporting members which are each secured at one end to the periphery of the color selection electrode and are supported at the other end by a supporting point in the tube wall. The invention particularly relates to the construction of the supporting members for the color selection electrode.

In general, such supporting members consist of a resilient strip which is secured at one end to the periphery of the color selection electrode and is provided at its other end with an opening receiving a conical cam on the wall of the tube. The position of the color selection electhe errors resulting from this displacement, the shadow mask must be displaced slightly towards the phosphor screen so that the holes are again located on the connection line between the center points of the color elements associated with these holes and the mean deflection point of the electron beams.

The errors resulting from the non-symmetrical distribution of the supporting members along the periphery of the mask can be reduced if the supporting members are arranged so that they cross the axis of the tube. When these members are twisted due to the expansion of the shadow mask, the securing point of each member to the periphery of the shadow mask describes an arc of a circle the center point of which is constituted by the supporting point of this member in the Wall of the tube, which are of a circle produces a movement having not onlya component directed towards the phosphor screen-but also a component directed at right angles to the axis of the tube. Consequently, the whole shadow mask will not only be slightly moved towards the phosphor screen, but will also be slightly displaced, so that the center point of the screen trode is entirely determined by the position and the length of the resilient supporting members and also by the area at which the opening surrounds the conical cam.

Due to thermal expansion of the color selection electrode in operation, the supporting member is twisted and the strip then pivots about the cam. This may result in wear and hence in a change of the position of the color selection electrode during the life of the tube. Moreover, the contact point between the strip and the cam can be displaced along the longitudinal axis of the cam during the pivotal movement.

These disadvantages can be fully avoided if, according to the invention, at least one of the suspension members consists of at least two parallel flat strips which are spaced apart by a certain distance and which are bent over at their ends and are directly or indirectly interconnected. The strips then form the boundaries of a parallelogram so that a straight-line guiding of the mask is obtained. Since the part of the suspension member surrounding the cam no longer performs pivotal movements with respect to the cam, displacement and wear at this area are avoided. If it is ensured that the parallel strips are twisted only at the kink points, this twisting and hence the movement of the color selection electrode are accurately defined and can be calculated beforehand.

Due to thermal expansion of the color selection elec trode, which generally is a shadow mask, the disadvantage is met that the holes in this mask are displaced with respect to the associated color elements of the display screen, especially in the proximity of the edges of the shadow mask. In order to eliminate as far as possible remains on the axis of the tube and the errors produced in the proximity of the edges of the mask owing to the asymmetrical displacement of the holes can be eliminated.

The suspension members are preferably arranged so that the parallel flat strips are at right angles to the main direction of the electron beams if these beams should pass through the securing point of this supporting member to the color selection electrode. This results in such a displacement of the color selection electrode that all the parts are displaced in the beam direction at the relevant areas so that the mislandings owing to expansion of the color selection electrode are completely compensated for. The supporting members which are arranged outside the center of the straight sides of the color selection electrode are then at a given angle to the axis of the tube.

The invention will now be described more fully with reference to the drawing, in which:

FIGURES 1, 2, 3 and 4 are different embodiments of suspension members according to the invention,

FIGURE 5 is an elevation, and

FIGURE 6 is a sectional view of another embodiment of a supporting member.

In the figures, reference numeral 1 denotes the glass window and reference numeral 2 a color selection electrode which has the form of a shadow mask and is secured to an annular frame 3. The window 1 is provided with three glass cams 4 which are distributed asymmetrically along the periphery of the frame 3. The parallel strips 5 and 6 are spaced apart by a certain distance and are bent over at their ends. Though in FIGURES 1 and 2, the bent-over ends of the strips are interconnected, they bear by means of an auxiliary strip 7 on the cam 4. In FIG- URES 3 and 4, the ends are on the one hand relatively independently secured to the annular frame 3 and on the other hand to the auxiliary strip 8. The strips from the boundaries of a parallelogram. It should be ensured that the straight sides of the parallelogram have a sufiicient rigidity so that twisting mainly occurs at the kink points of the strips 5 and 6. This may be achieved by welding auxiliary strips to the straight sides. If desired, the straight strips 5 and 6 may also be reinforced by pressing ribs into them. The supporting members may consist of more than two parallel strips. The material of the strips may then be thinner, the rigidity of the members being the same, so that reinforcing ribs can be more readily pressed.

In the embodiment of FIGURES l and 2, the advantage is obtained that the supporting members can be manufactured as separate units.

A very advantageous embodiment is shown in FIG- URES 5 and 6, in which a reinforcing strip 9 is arranged 3 on the fiat side of the parallelogram which must be secured to the mask ring 3. Due to the fact that the strip 9 projects on both sides beyond the strip 6, the projecting parts of the strip 9 can be rigidly secured to the mask frame 3 by means of spotwelding. The strip 5 is provided with a hole 10 for receiving the cam 4, which hole has the usual substantially triangular form so that the mask can be more readily removed from the window, for a round opening tightly surrounds the conical cam 4.

The supporting members are preferably arranged so that the strips 5 and 6 are at right angles to the'main direction of electron beams which would pass through the securing points of the supporting member to the mask frame; Upon heating, the mask will then be displaced so that all its holes are displaced in the beam direction at the relevant areas so that a full compensation is obtained;

What is claimed is:

1. A cathode-ray tube for displaying colored television images comprising an envelope having a display window at one end thereof, a luminescent screen supported by said window, a substantially rectangular shadow mask arranged in the proximity of the luminescent screen, said shadow mask having a plurality of apertures aligned with selected areas of the luminescent screen, at last three stripshaped supporting members for supporting said shadow mask within said envelope, said supporting members being arranged off the center of a straight side of the mask, each of said supporting members being secured at one end to the periphery of the shadow mask at the other end by a supporting stud in the wall envelope, at least one of the suspension members consisting of four flat spaced strips forming a parallelogram having a side fastened to the frame of said shadow mask and having an opposite side forming part of a strip longer than said side and including an aperture therein fitting over said supporting stud, the sides connecting said opposite sides being substantially at right angles to a line from the deflection center of said tube.

2. A cathode-ray tube as claimed in claim 1 in which the parallel strips are each independently secured to the shadow mask.

3. A cathode-ray tubefas claimed in claim 1 in which the strips are supported by an auxiliary strip by the supporting studin the wall of the'tube.

4.- A cathode-raytube as-clairned in claim 1 in which at least one of the parallel strip-shaped part's'of the suspension member' is reinforced by an auxiliary strip so that it is twisted mainly 'at the kink points.

5. A cathode-ray tube as claimed in claim 1 in which the parallel fiat strips are reinforced by pressing ribs into them. v

6. A cathode-ray tube as claimed in claim 1 in which an auxiliary strip projects 'on both sid'es beyond the supporting member" and is secured by the projecting ends to the shadow mask.

References Cited UNITED STATES: PATENTS 3,399,319 8/1968 Schwartz et al. 2,846,608 8/ 1958 Shrader. 3,296,477 1/1967 Shrader et al. 3,330,980 7/1967 Shrader. 3,334,259 8/1967 .Shrader. 3,370,194 2/1968 Schwartz et al. 3,387,160 6/1968 Schwartz.

ROBERT SEGAL, Primary Examiner US. Cl. X.R.

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