MXPA98009701A - Perforated mascara frame of a cathode ray tube, its manufacturing procedure and suspension elements of a perfor master frame - Google Patents

Abstract

The present invention relates to a frame comprising flat sides (30a, 30b, 30c, 30d) placed following the lateral faces of a straight prismatic surface. The sides (30a, 30b, 30c, 30d) of the frame (30) comprise an outer membrane (31) and an inner membrane (32) spliced together and fixed against each other and each constituted by a portion of thin metal strip preferably reinforced by ribs. The suspension devices (34) of the frame (30) in the glass casing of the cathode ray tube can be fixed by welding by welding the angled portions (33) of the frame (3).

Description

- - PERFORATED MASCARA FRAME OF A CATHODIC RAY TUBE, ITS MANUFACTURING PROCEDURE AND SUSPENSION ELEMENTS OF A PERFORATED MASCARA FRAME FIELD OF THE INVENTION The invention relates to a perforated mask frame of a cathode ray tube and especially a color television tube. The perforated mask color television tubes comprise a glass envelope in which metal parts are fixed, where one is constituted by the perforated screen that is integral with a frame and the other by a magnetic shield disposed inside the glass envelope . The glass envelope is made up of two pieces, a slab comprising the screen on which the image is formed and a cone on which the electron guns and the deflection coils of the electron beams of an electron beam are fixed. CRT. The perforated mask is made from a thin metal strip in which pieces of small dimensions and adapted shape are made or manufactured by a chemical process. The bands Rßf. Metallic 02TT64 used are usually made of low carbon steel or an iron-nickel alloy such as Invar. The perforated mask is shaped by heat or cold stamping in order to present a peripheral rim that follows that which is welded to a metal frame. The assembly constituted by the frame and the mask is fixed inside the glass slab, by the intermediation of suspension devices fixed on the frame and which are attached to the pawns sealed in the glass of the slab. The internal shielding of the tube can be fixed either on the frame of the perforated mask, or on the fixation pins sealed in the glass of the slab. The cathode ray tubes of different types are known, which are distinguished in particular by the type of perforated mask or the type of frame used or even by the way in which the frame is hooked into the glass shell of the tube. With regard to the different types of frames used, in particular the thin and light frames are distinguished where the thickness can be, for example, of the order of 0.2 mm and the thick, rigid and heavy frames.

As regards the ways of attaching the frame to the interior of the glass envelope, the suspension of the frame is distinguished in the vicinity of the corners of the screen and the suspension of the frame to the middle part of the peripheral edges of the frame. slab, by the intermediation of fixed bimetallic compensation devices on the outer surface of the sides of the frame. The suspension of the perforated mask, by means of its frame, inside the glass envelope of the tube must allow several functions to be filled.

By account principles, this suspension must allow to control the relative movements of the glass screen and the perforated mask that are caused in particular by the dilatation of the perforated mask that is heated under the impact of the electron beams, in the manner of Keep the purity of the colors of the image formed on the screen. On the other hand, the suspension devices must keep the perforated mask in position inside the glass envelope, when the cathode ray tube receives a shock, and protect the perforated mask against external mechanical pressures. Finally, the suspension systems must allow to demonstrate or displace the perforated mask, during the manufacture of the cathode ray tube, then send it back to its place inside the glass envelope, as long as this is necessary. The assembly consisting of the perforated mask, the frame and the suspension devices of the frame must present in particular two following properties: on the one hand, they must allow to accommodate the dimensional variations resulting from a global warming of the assembly, on the other hand, they must present a great mechanical stability. Most assemblies known in the state of the art use a steel frame, thick, heavy and rigid, hooked with the help of three or four bimetallic springs coupled on the pawns sealed to the middle of the peripheral edges of the slab of glass. The disadvantages of such known assemblies are that the frame has a high thermal inertia and that the mode of compensation of dimensional variations of thermal origin is not completely symmetrical. It is also known to use thick, heavy and rigid steel frames that are hooked in the corners of the slab or wall with the help of four suspension systems. This arrangement that is symmetrical has the advantage of performing a thermal self-compensation; however, the frame always has a large thermal inertia. In addition, the thick frames known in the prior art often have a very important weight, which may be, for example, of the order of or greater than 2 kg, in the case of so-called "stretched-mask" technologies, the perforated mask is placed in tension on the frame where the rigidity of this is sufficient to resist the pressures resulting from the tensioning of the mask. It is also known to use thin frames where the thickness can be, for example, of the order of 200 μm, these lightweight frames are hooked at the corners of the slab. These thin frames have the advantage of having a low thermal inertia but they are very fragile due to their thin thickness. These frames also have insufficient stiffness. From this fact, it may be necessary to loosen the suspension devices on the fixing pegs to avoid unhooking the frame. The manufacture of the cathode ray tube thus becomes more complex. The object of the invention then is to propose a perforated mask frame of a cathode ray tube and in particular of a color television tube having flat sides placed substantially following the lateral faces of a straight prismatic surface and having a rigidification edge for fixing the perforated mask on the frame by the intermediation of which the perforated mask is put in place inside a glass envelope of the cathode ray tube comprising a cone and a slab comprising a screen, this The frame has a good mechanical stiffness, a weight as weak as possible, for a given stiffness, a weak thermal inertia and other advantages, for example a limited sensitivity to external periodic pressures, in a range of frequencies ranging from 100 to 400 Hz. In this objective, the flat sides of the frame comprise an outer membrane and an inner membrane attached and fixed one against the other and each constituted by a portion of a thin metal band. Preferably, in order to increase the mechanical stiffness of the frame, at least one of the outer and inner membranes is reinforced with at least one embossed part of the membrane. Following the preferred embodiment, one of the membranes, or the two membranes are reinforced by ribs. In order to properly understand the invention, it will now be described, by way of non-limiting examples, referring to the appended figures, various embodiments of a perforated mask frame, can be obtained according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary perspective view of a cathode ray tube with a perforated mask. Figures 2A and 2B are plan views of the metal strips cut before being shaped, so as to constitute an outer membrane and an inner membrane respectively of a perforated mask frame according to the invention and following a first mode of realization. Figures 3A and 3B are plan views of metal strips cut and shaped, so as to constitute an outer membrane and an inner membrane respectively, of a perforated mask frame following the invention and following a second embodiment. Figure 4 is a fragmentary perspective view showing the shaping by doubling and assembling the two metal strips as shown on Figures 2A and 2B, according to the embodiment of a perforated mask frame according to the invention and following the first embodiment. Figure 5 is a top view of the metal strips shown on Figure 4, in which their mounting position is shown before welding. Figure 6 is a top view, analogous to the view of Figure 5, showing the sheet metal bands such as those shown in Figures 3A and 3B, in their mounting position before welding. Figures 7A, 7B, 7C and 7D are views in vertical section following line 7-7 of Figure 5 or Figure 6 showing an outer membrane and an inner membrane of a frame of the perforated mask according to the invention in its mounting position as well as a part of a mask in its mounting position as well as a mask in its mounting position as well as a part of a mask in mounting position on the frame. Figures 8A, 8B and 8C are plan views showing the welding zones of an internal membrane and an outer membrane of a perforated mask frame according to the invention, joined and fixed against each other.

- - Figure 9A is a perspective view of a perforated mask frame following the invention in an assembled state. Figure 9B is a top view of an area of the frame angle shown on Figure 9A.

Figure 9C is an elevation view of the angle area of the frame, shown on Figure 9A. Figure 10 is a plan view of an outer membrane and an internal membrane of a perforated mask frame according to the invention illustrating a variant of the method of manufacturing a frame according to the invention. Figure 11 is a perspective view of a perforated mask frame following the invention, which allows to practice the technology of "stretched mask". Figure 12A is a perspective view of a part of one side of the perforated mask frame according to the invention and according to a variant embodiment. Figure 12B is a sectional view following line 12B-12B of figure 12. Figure 12C is a sectional view following line 12C-12C of figure 12. Figures 13A, 13B and 14 represent a suspension element. Fixed by joining a part of an angle of a frame.

DETAILED DESCRIPTION OF THE INVENTION In Figure 1, the different pieces that constitute a cathode ray tube with a perforated mask used as a color television tube are shown. The cathode ray tube designated in its assembly by reference 1, comprises a glass envelope consisting of a cone 2 and a slab 3 and two metal parts 4 and 9 where the fixing is made inside the glass shell of the tube . The piece 4 is a pre-assembled assembly comprising the perforated mask 5 constituted by a metal sheet crossed by the openings 6, the frame 7 of the perforated mask and the suspension devices 8 of the assembly 4 inside the slab 3 of the glass envelope. The piece 9 is a metal wall shaped so as to constitute an internal magnetic shield coupled in the cone 2 of the glass envelope, more often fixed on the frame. The cone 2 of the glass envelope has a rectangular base with rounded corners and a curved wall having a shape very similar to that of a cone where the section decreases in the direction of the rear end of the cathode tube 1 at the level of which fix on the cone 2 the electron guns and the windings of the cathode ray tube deflection. The slab or surface 3 comprising a slightly curved wall 3a constituting the screen of the cathode ray tube and a flange 3b where the rectangular base of rounded corners can be perfectly superimposed with the base of a cone 2. On the internal surface of the flange 3b of the slab 3, the pawns 10 are fixed and coming out towards the inside, allowing the coupling of the assembly 4 comprising the perforated mask 5 and the frame 7, by means of the suspension devices 8. fixed on the edges of the frame 7. The cathode ray tube 1 shown in FIG. 1 is of the type comprising the fixing pins 10 fixed in the middle part of the edges of the slab intended to cooperate with the fixed suspension devices 8 in an average position on the sides of the frame 7 of the perforated mask 5. In figure 1, the constituent parts of the cathode ray tube 1 have been represented before their assembly to constitute the cathode ray tube.

To manufacture and assemble the cathode ray tube, the manufacture, separately, of the constituent parts 2 and 3 of the glass envelope, of the assembly 4 and of the magnetic shield 9. These parts are assembled, as will be described later. The manufactured mask 5 is made from a thin strip in which holes 6 are made by chemical manufacture. The perforated plate is then put into shape by heat or cold drawing to form a mask 5 comprising a peripheral mounting flange of substantially rectangular shape with rounded corners. The frame 7 is fixed by welding on the mounting edge of the perforated mask 5. The fixing devices 8 are then welded on the edges of the frame. The assembly 4 is thus made and fixed to the interior of the slab 3 after various thermal treatments. The magnetic shield 9 is fixed immediately, for example by joining, on the frame 7. In certain embodiments, it is necessary to fix the shield on the sealed pins on the internal wall of the slab. The glass envelope can be assembled immediately.

As it has been explained above, in the case of the cathode ray tubes with perforated mask following the prior art, the frame for the perforated mask, which presents at the same time a very great mechanical rigidity, a weight and an inertia, has never been realized. Weak thermal sensors and that can thus have a limited sensitivity to periodic pressures in certain frequency ranges. The perforated mask frame according to the invention that will be described later allows to remedy the drawbacks of the devices according to the prior art. In FIGS. 2A and 2B, respectively, an outer membrane 11 and an inner membrane 12 of a perforated mask frame according to the invention are shown. The membranes 11 and 12 are made of or fabricated from a sheet or sheet metal strip of a metallic material, such as a steel, an alloy of iron-nickel or of another alloy. The band of the thin metal sheet is cut following an external contour that allows to delimit four zones lia, llb, 11c, lid or 12a, 12b, 12c, 12d following the length of the band, destined to constitute the outer membrane and the inner membrane , respectively, of each of the sides or sides of the perforated mask frame, according to the assembly of the strips 11 and 12 to realize a frame where the flat sides are placed following the lateral faces of a rectangular parallelpipe. The zones Ia and 11c of one part and 12a and 12c of another part of the bands 11 and 12 respectively are identical in shape and are intended to constitute the membranes of a large side or side part of the frame. The zones 11b and lid of a part and 12b and 12c of another part of the bands 11 and 12 respectively are identical and are intended to constitute the membranes of the small sides of the frame. Between two successive zones intended to form the membranes of the sides of the frame and at one of the ends of the band 11 or 12, there are provided angular or connecting areas lie, llf, llg and llh for the band 11 or even 12e, 12f, 12g and 12h for the band 12. In each of the areas intended to constitute an internal or external membrane of one of the sides of the frame, the metal band is put into shape, for example by embossing or cuts, to present parallel reinforcement ribs between them. The successive zones of the strip 11 intended to constitute the outer membranes of the frame comprise ribs 13 parallel to the longitudinal edges of the band. The zones of the band 12 intended to form the internal membranes of the sides of the frame comprise ribs 14 perpendicular to the longitudinal edges of the band. It will also be possible to provide the reinforcing ribs parallel to the longitudinal edges of the strips to the areas intended to form a membrane of a large or small side of the frame and of the reinforcement ribs perpendicular to the longitudinal edges of the band in the areas intended for reinforcement. to constitute a membrane of the other sides of the frame.

Thus, the same band can comprise, in the successive zones, the longitudinal direction ribs and the ribs perpendicular to the longitudinal direction. In addition, the angle and splice or connection zones may also comprise the ribs 15 (in the case of the band 11) or 16 (in the case of the band 12) which are perpendicular to the ribs 13 or 14 of the areas that they constitute the membranes of the sides of the frame.

The plates 11 or 12 are pierced, at the level of the each of the ribs 13, 15, 14 and 16, of the holes 17 or 18 that traverse the strip over their entire thickness, in order to avoid trapping the gas between the membranes internal and external sides of the frame, when the membranes are joined one over the other and welded together, as will be described later. In addition, at least one of the two bands (the outer band 11 in the case of the embodiment represented on FIGS. 2A and 2B) comprises, following one of its edges, the legs 19 at the level of each of the successive zones that they constitute a membrane of a frame wall and at the level of the angle and junction zones. As it is visible in Figure 7B, when the band is bent to form a frame, the legs 19 are inwardly 90 °, relative to the plane of the strip 11. It is also visible on Figure 7B that a part 20 of an upper edge of the strip 11 of a length lower than the lower edge 19, is likewise bent inside to 90 °, which contributes to the rigidification of the frame. The perforated mask 5 is spliced and welded along the upper edge 20 of the frame. In FIG. 7B, the perforated mask 5 is shown in the assembly position. The flange 5a of the mask 5 is spliced against the upper part of the outer membrane of the frame, the length of the edge 20 bent towards the inside of the frame. The welding of the mask is carried out on the outside of the frame, as shown by the arrow 51. In FIG. 7C, a variant embodiment of the frame and the manner of fixing the perforated mask 5 have been shown. the external membrane of the frame is bent towards the outside of the frame and the rim 5a of the mask 5 is connected to the inner membrane of the frame along the edge 20. The welding can be carried out on the outside (arrow 51) or on the outside. inside the frame (arrow 51 '). As a variant, the stiffening edge 20 could be made by bending the upper edge of the inner membrane towards the outside above the outer membrane and the rim 5a of the mask 5 welded on the inner membrane. In Figure 7D, the case of a stretched mask frame has been represented. In this case, the edge 20 and the mask 5 have the shape of cylinder portions with a circular section. The mask 5 is spliced against the edge 20 and is fixed on the edge 20 by welding. The assembly of the mask on the frame according to the invention will be described in more detail below, in the case of the "spread mask" technique, referring to FIG. 11.

As can be seen from FIG. 7A, in certain cases, the inner membrane of the frame can also behave likewise or can also have a flange 19 'folded 90 ° inwards and superimposed on the edge 19 of the outer membrane. After having cut, formed and pierced the bands 11 and 12, the assembly and the formation of the frame is carried out. According to a first example of the start-up illustrated by figures 4 and 5, the assembly by welding of the external and internal membranes of the frame is carried out after the bending of the bands 11 and 12 constituting these membranes. According to a variant embodiment that will be explained in relation to FIG. 10, the assembly by welding of the external and internal membranes of the frame in the superimposed positions can be carried out prior to the bending of the membranes. In the case of the first embodiment, the bending of a part of the edge of the strip 11 intended to form the outer membrane, located on the opposite side of the legs 19, is made to form the flange of stiffening along which the perforated mask is fixed. In certain cases, it is also possible to fold the corresponding edge of the band 12 constituting the inner membrane, the stiffening rim along which the perforated mask is fixed which is then constituted by the juxtaposed flanges of the outer and inner membranes. The legs 19 of the band 11 are then folded inwards, as shown on the figures 7A and 7B. The corresponding legs 19 'can be positioned or provided on the band constituting the inner membrane 12, these legs 19' are also bent inwards at 90 °. The doubling of the band 11 constituting the outer membrane is made, as shown in Figure 4, along the edges perpendicular to the longitudinal edges of the band that delimit the areas of the angles lie, llf, llg and the Splice area llh. The band 11 is placed, after dubbing, inside a template that allows to maintain the zones of the band located between the two zones of the angle by following the side faces of a rectangular parallelpipe, as shown in figure 5. It is secured then the maintenance of the outer band 11 under the shape given by the template, by welding one on the other of the legs 19 constituting one of the folded edges of the band then the band 12 is introduced, after bending, as shown in FIG. they represent on figures 4 and 5, inside the band 11 that constitutes the external membrane bent and preassembled following the required shape. The bent strip 12 is inserted into the bent and pre-assembled band 11, in an arrangement as shown in figure 5, that is to say with the lid area of the band 11 facing the front of the area 12b of the band 12. In this way, the splice areas 11h and 12h of the strips 11 and 12 respectively are in the frame angles located at the ends of a diagonal. After having placed the bands 11 and 12 folded in their position shown on FIG. 5, the welding of the superimposed strips is carried out, in particular to perform the fixing of the connection areas 11h and 12h against an area of an angle facing front, as represented by the arrows 24. The welding can be an electric welding or a laser or plasma welding. It is also possible to use an alloy for welding as long as it is compatible with the requirements of the vacuum content and the electronic characteristics expected from the cathode ray tube. The embodiment of the frame that has been described in relation to figures 4 and 5 uses two bands 11 and 12 as shown in figures 2A and 2B. It is also possible, according to the second embodiment, to realize a frame using four cut-out and shaped bands, two of these bands that constitute an outer membrane of the frame and the other two bands that constitute the internal membrane. In FIGS. 3A and 3B, there is shown respectively a band 21 constituting a part of an outer membrane of a perforated mask frame according to the invention and a cut-away band 22 constituting a part of an internal membrane of a perforated mask frame. following the invention and according to the second embodiment. To form the frame, two bands are used, such as the band 21 and two bands such as the band 22 that are assembled after bending, as shown in Figure 6. The band 21 comprises two successive zones 21a and 21b intended for constituting the outer membrane of a large side and a small side respectively of the perforated mask frame. Similarly, the band 22 comprises two successive zones 22a and 22b intended to constitute the membranes - -international of a large side and of a small side of the perforated mask frame. In the same way as the bands 11 and 12 shown in figures 2A and 2B, the bands 21 and 22 comprise zones of angle between the areas intended to constitute the membranes of the sides of the frame and a splice zone in one of its ends. It is not necessary to describe in detail the bands 22 and 22 which are manufactured analogously to the bands 11 and 12 and which correspond to a portion of these bands in the longitudinal direction. To make the perforated mask frame, as shown in FIG. 6, two strips 21 and 21 'are used to form the outer membranes of the frame and two strips 22 and 22' intended to constitute the internal membranes. The outer bands 21 and 21 'are folded and placed in a template in such a way that the zones of the bands such as 21a and 21b are arranged following the lateral faces of a rectangular parallelpipedo. A pre-assembly of the strips 21 and 21 'is then carried out following the defined parallelopiped contour, by welding between them the legs or tongues 23 provided along a longitudinal edge of the band 21 and bent 90 ° inwards. The bands 22 and 22 'are bent and introduced into the interior of the frame formed by the bands 21 and 21 'folded and preassembled following a parallelopiped contour and kept inside the template. The bands 22 and 22 'are introduced, after folding, into the interior of the external frame constituted by the bands 21 and 21', so that their splice end areas 22h and 22'h are located opposite each other in the zones. angle of the bands 21 and 21 'respectively and aligned on a diagonal of contour defined by the bands 21 and 21' preassembled differently from the diagonal that follows in which the splice areas 21h and 21 'h of the lines are aligned. bands 21 and 21 'respectively. The welding of the strips 11, 21 ', 22 and 22' spliced against each other in the arrangement shown in figure 6 is carried out immediately. In particular, welding of the splice areas of the strips is carried out following the four angles of the frame, as represented by the arrows 25. Referring to FIGS. 7A and 7B, which represent a simplified sectional view of the bands constituting respectively the outer membrane and the internal membrane of the frame, during the welding of these bands one on the another, it is seen that, in the mounting position, the ribs 13 of the outer band 11 (or 21) are directed towards the outside and the ribs 14 of the inner band 12 (or 22) are directed inwards, so that the flat areas of splice of the outer and inner bands are spliced against each other in their position of welding. Welding is performed in these flat areas spliced against each other, inside or outside the frame, as represented by the arrows 26 and 26 '. It is not necessary that the external and internal bands have the same length and the same thickness, these dimensions can be adapted according to the characteristics sought by the frame of the perforated mask. On the other hand, the inner membrane must cover the largest possible surface of the outer membrane between its upper edge of fixation of the perforated mask and its edge trimmed in the form of a tongue and bent inwards. The inner membrane may or may not comprise an edge 19 'folded inwardly and superimposed on the edge 19 (or 23) of the outer membrane. In FIGS. 8A, 8B and 8C, there is shown an internal membrane 12 spliced and welded on an outer membrane 11 and constituting one side of a perforated mask frame according to the invention. The embodiments illustrated by the figures 8A, 8B and 8C differ by the type of welding performed to join the two membranes arranged in an overlapping manner. The membranes 11 and 12 comprise the reinforcing ribs respectively 13 and 14 which are placed following the perpendicular directions between them. The membranes 11 and 12 are traversed by the openings 17 and 18 at the level of each of the ribs 13 and 14, such that the space between a rib of a membrane exiting inwards or outwards and the surface of the other membrane can be put in communication with the outside. This avoids accumulating the gas on the inside of the walls of the frame, such gases that generate the risk of clogging and disturbing the operation of the cathode ray tube. In the case of the embodiment shown in FIG. 8A, the welding of the membranes 11 and 12 was carried out by the points of the weld 27. The welding points 27 are aligned along the two longitudinal edges of the membranes 11 and 12. and interspersed between ribs 13 and 14.

In the case of the embodiment of the assembly of the membranes 11 and 12 shown in FIG. 8B, the connection or bonding of the two membranes is carried out by the continuous welding lines 28. In particular, two continuous welding lines 28 are carried out following the longitudinal edges of the membranes 11 and 12, the welding lines surround the reinforcing ribs 13 and 14 and the welding lines are generally closed between the reinforcing ribs 13 and 14. In the case of the embodiment shown in the figure 8C, the connection between the membranes 11 and 12 is carried out by distributing a leg to be welded in certain zones 29 located between the membranes 11 and 12 and which bring the frame pre-assembled to a welding temperature, inside a furnace. The connection is thus made by welding the two membranes 11 and 12, in the zones 29.

Preferably, the zones 29 are positioned along the longitudinal edges of the membranes 11 and 12 between the reinforcing ribs 13 and 14. It has been found that the embodiment shown in Figure 8B in which the membranes are bent by the lines of continuous welding and the preferential embodiment that ensures the best bonding of the membranes 11 and 12 spliced against each other.

In FIG. 9A, the perforated mask frame 30 is shown in its assembled and welded state. The frame 30 shown in Figure 9A comprises four sides in the form of plates 30a, 30b, 30c and 30d placed following four side faces of a rectangular parallelpipe. Each of the plate-like sides of the frame 30 is constituted by an outer membrane 31 and an inner membrane 32 joined together and welded together. The outer membranes and the internal membranes of the four sides of the frame can each be made from one or more metal bands. The inner membranes and outer membranes are reinforced by ribs that have the perpendicular directions between them. Between two successive plate-shaped sides, the frame comprises a flat angle region 33 in which a suspension device 34 of the frame can be fixed inside the glass envelope of the cathode ray tube. The angle zones 33 of the frame can comprise holes that pass through them, which allows the fixing by means of attachment of the suspension device 34. It is thus possible to carry out an effective fixation of the suspension devices without having to resort to welding operations. One of the edges of the frame, which will be designated as upper edge 35, in fact of its arrangement in Figure 9, is used to increase the stiffness of the structure. The upper edge of the frame 30 is made by bending it inwards or outwards from one of the longitudinal edges of one of the membranes 31 and 32, preferably the longitudinal edge of the outer membrane 31, or possibly by folding the longitudinal edges facing each other of the outer membrane 31 and of the inner membrane 32. As explained above, the perforated mask is fixed on the frame, along the upper edge of the frame 30. The edge the outer membrane opposite the edge 35, called the bottom edge , it is also folded inwards to form the tabs 36 used in particular to carry out the pre-assembly of the frame 30. It is also possible to provide folding tabs, at the level of each of the sides of the frame, as well as with regard to the outer membrane 31 and as regards the inner membrane 32. In this case, the lower edge folded down of the frame 30 is constituted by overlapping tabs and welded together of the outer membrane 31 and the outer membrane 32.

The tongues 36 folded or folded towards the interior of the frame may comprise reinforcing ribs 37. The membranes may comprise openings that pass through them 38 at the level of each of the reinforcing ribs 37. In this case, the tongues 36 reinforced by the ribs , lowered towards the inside and welded together, constitute a highly rigid assembly on which it is possible to fix the magnetic shielding of the cathode ray tube, for example by joining. As can be seen from FIGS. 9B and 9C, two tongues 36 of two successive sides of the frame 30, for example the sides 30b and 30c are fixed with respect to each other by a tongue 36 'cut away, for example, in the part bottom of the outer membrane, vertically of the area of the angle 33. The tongue 36 'is in an inclined position inwardly at 90 °, superimposed on the end portions of the tabs 36 and fixed on them by the welding points 39. This operation is carried out after the pre-assembly of the frame into a template that gives it its shape. It is then possible to carry out the start-up of the internal membrane 32 inside the preassembled frame and it is maintained in the template for welding against the pre-assembled outer membrane. In figure 10, two metal strips 41 and 42 cut out and shaped so that they can constitute the outer membrane and the inner membrane respectively of a frame or frame for perforated mask according to the invention have been represented. The membranes 41 and 42 are manufactured in a substantially identical manner to the membranes 11 and 12 shown in FIGS. 2A and 2B respectively. In particular, the strips 41 and 42 are cut so as to have distributed areas that follow the length of the strip intended to constitute the outer and inner membranes of the flat sides of the frame, arranged following the lateral surfaces of a rectangular parallelpipe. These zones are separated by angle zones. The fold lines of the membranes 41 and 42, after the construction or manufacture of the frame are lines perpendicular to the longitudinal direction of the corresponding band separating the zones of the angle of the areas intended to constitute the sides of the frame. The outer membrane 41 comprises an edge, called the bottom edge, from which the tongues 43 are cut, which are bent at 90 ° towards the inside of the frame, before bending and shaping the frame. The opposite longitudinal edge of the membrane 41 is bent inwards or outwards at 90 °.

The trimming and bending inwards of the edges of the membrane can be done only for the outer membrane or even on the outer membrane and on the inner membrane as well. The metal bands that make up the membranes 41 and 42 are each cut at one of their ends to present a splice area or connection 44 or 45, these splice or connection areas are related or superimposed on one another and welded, after bending the strips 41 and 42, at the time of mounting the frame. The assembly and welding of the frame constituted by the metal strips 41 and 42 shown in FIG. 10 are carried out following a variant of the first embodiment described above. The fabrication of the membranes 41 and 42 from the metal strips is carried out in the same manner as in the case of the first embodiment. In particular, it is carried out on each of the zones such as 41 a and 42 a of the strips 41 and 42 intended to constitute the external and internal membranes on one side of the frame, the reinforcement grooves, for example by embossing or by roller cutting . In the case of the first embodiment, the bending of the strips and their assembly by welding will be carried out successively. In the case of the variant, the welding of the superposed strips before bending is carried out in a first step, then the bending of the double strip obtained and finally the welding of the overlap zones. Preferably, the bands are welded one on top of the other in an overlapping position by welding with light alloy. In order to carry out the welding, one of the bands is extended in different zones, for example the band 41 intended to constitute the outer membrane, a solder paste. The solder paste with light alloy can be distributed, in each of the areas intended to constitute a membrane on one of the sides of the frame, as shown in Figure 8c. The paste or portion to be welded with light alloy is placed on the surface of the band 41 opposite the surface with respect to which the reinforcing ribs are placed or protruding. It is superimposed on the band 41 coated with paste to weld the band 42, so that the band 42 rests on the band 41 by intermediation of its surface opposite the face with respect to which the ribs are placed in a protruding manner. After the start of the band 42 on the band 41, the zone 42a is superimposed on the area 41a, as shown by the arrow 40. In this way, the double band obtained by the superposition of the bands 41 and 42 has the coupling areas at their ends 44 and 45. The connection is made by welding with light alloy of the strips 41 and 42 introducing the strips 41 and 42 in an overlapping position in an oven. At the temperature of the furnace, the solder paste ensures the welding connection of the two strips 41 and 42 in an overlapping position. The bending of the obtained double band is done immediately, the length of the transversal lines separates the zones of the angle of the zones that constitute the membranes of the sides of the frame. The pre-assembly of the frame is then carried out by welding one on the other of the tongues 43 cut out at the lower edge of the band 41 which have been bent towards the inside. The frame or frame is closed by welding the splice areas 44 and 45 mounted one on top of the other. As in the case of the first and second embodiments, the shape of the folding frame is imposed and maintained by a template in the form of a rectangular parallelpipe. However, it is preferable to manufacture the frame as described above in relation to FIGS. 4, 5 and 6. In FIG. 11, there is shown a frame 46 according to the invention comprising two opposite sides 47a and 47b where one of the longitudinal edges it is cut out to present a circular arc shape and bent inward to form a rim 48a and 48b of cylindrical shape. The edge 48a of side 47a and the edge 48b on the side 47b of the frame 46 are carried by the same cylindrical surface of the axis ZZ '. The flanges 48a and 48b allow the fixation by welding on the frame 46, of a perforated mask that is thus placed and maintained following a cylindrical surface of the axis ZZ '. The frame 46 allows to easily assemble a perforated mask of the "stretched mask" type. For this, as indicated by the arrows 49 and 49 ', a force F is exerted on the surfaces 47a and 47b which makes a bending of the sides 47a and 47b of the frame towards the interior of the frame and on the surfaces 47c and 47d a force F 'in such a way that the deformation of the edges 48a and 48b is a translation.

The perforated mask is fixed on the edges 48a and 48b always maintaining the force that ensures the flexion of the sides 47a and 47b of the frame. After the welding of the perforated mask, the bending forces F and F 'are relaxed, so that the sides 47a and 47b of the frame are turned outwards by elasticity and ensure a tensioning of the perforated mask. The frame 46 according to the invention thus allows the extended mask technique to be started very simply and very quickly, avoiding the use of a massive, heavy and rigid frame. The frame 46 can also carry, along its opposite surface at the edges 48a and 48b, a cut-out flange in the form of tabs 50 reinforced by ribs that are bent at 90 ° towards the interior of the frame. In this case, the magnetic shielding of the magnetic tube can be fixed on the reinforced tongues 50 resting between them by welding. Figure 12A shows a side 51 of a frame according to the invention and according to a variant embodiment.

The sides of the frame, such as the side 51, are constituted by an outer membrane 51a and an inner membrane 51b spliced and fixed against each other. With regard to the embodiments described above, the membranes have no ribs and consist of metal strips, thin and / or recessed, in order to present the flat joining parts that come into contact with each other and on which the welding of the membranes is carried out. As is visible from FIGS. 12B and 12C, the membranes 51a and 51b may be welded together on one another following the upper edge 52 and following the lower edge 53 of the frame. In addition, the membranes have molded or embossed zones 54 of substantially square shape that are reported to the inside of the side of the frame that come into contact and welded two by two with the assembly of the membranes, as is visible from Figure 12B (the parts molded 54a and 54b). At least one of the membranes 51a, as shown in FIG. 12A or the two membranes, are optionally perforated by passing holes 55 which make it possible to prevent the gas from accumulating in the internal space of the frame wall. In addition, the outer membrane 51a is bent at its upper part and at its lower part to form the stiffening flanges and the assembly of the perforated mask. The frame made as shown by FIGS. 12A, 12B and 12C and the membranes have no ribs and have an overall stiffness in relation to the torsion and in relation to the flexure which is slightly lower than the overall stiffness of a frame made from of metal bands having ribs, as described above. A change in the amplitude of certain vibration modes of the frame structure is observed. It is well understood, in the case where the frame is made from membranes that do not have ribs, that these membranes can be mounted between them, by welding, according to any of the mounting modes represented by figures 8A, 8B and 8C. A good rigidity of the structure of the frame can be obtained when the contact surface of the two membranes, for example represented by the welded zone 29 in Figure 8C, it is much less than the molded surface of the membranes that follow which membranes are separated one from the other. It is also possible to realize the frame from a metal band embedded or molded and from a metal band not embedded, entirely flat. Furthermore, in this case, a sufficient stiffness of the frame structure modifies the vibration modes of this structure. In general, the rigidity of the structure can be optimized as a function of the number and length of the ribs made in the membranes. It is possible, in particular, to increase the number of ribs as long as the surfaces allow or even limit the number of ribs and increase the surface area of these ribs. The ribs can also communicate between them to constitute a single volume. The perforated mask frame according to the invention where the flat sides are constituted by two membranes welded together presents, in particular in the case where the membranes have ribs, a very good mechanical rigidity in relation to the bending, in relation to the torsion and traction and compression, in the case of static pressures. In addition, due to the fact that they are made or manufactured from thin metallic strips, their weight becomes very weak for the stiffness sought in the case of the manufacture of the perforated mask cathode ray tubes. Furthermore, it has been possible to show that the frame according to the invention has a limited sensitivity to the external periodic pressures in a range of frequencies ranging from 100 to 400 Hz. The frame according to the invention also has a structure that facilitates the mounting of the perforated mask inside the glass envelope of the cathode ray tube, for example using the suspension elements fixed in the frame by joining and also fixing the magnetic shield of the cathode tube. In FIGS. 13A, 13B and 14, there is shown a suspension element of a new type that can be fixed by joining a part of an angle of a frame according to the invention or of a frame according to the prior art. . As it is visible from FIGS. 13A and 13B, the suspension element generally designated by the signal 55 carries an upright 56 on which a spring 57 that projects on an internal side of the upright 56, a connection plate is made or coupled. or hook 58 attached to the upper edge of the upright, in an inclined arrangement with respect to the upright and two fixing tabs 59a and 59b attached to the lower edge of the upright, substantially perpendicular to the upright and comprising at its end a projection, respectively. 'and 59'. furthermore, the upright comprises, following its upper edge, two hooking legs 60a and 60b. The suspension element 55 can be fixed by joining it to a wall 62 of a mask frame 61 that constitutes an angle zone of the mask, as shown in FIG. 13A. In Figure 13A, the mask frame is represented with its vertical edges and its fixing flange of the perforated mask, in its upper part. The hooking legs 60a and 60b are coupled on the upper edge of the mask angle wall 62 in such a way that the upright 56 is supported on the angle wall 62 by means of its spring 57. The tabs 59a and 59b they slide below the lower flange 63 of the frame 61 opposite the flange on which the perforated mask is fixed. By exerting a pressure on the upright 56, the spring is compressed and the tongues 59a and 59b are moved under the lower flange 63 of the mask until the projections 59 'and 59' b engage in the openings provided in a desired position through of the flange 63. The projections 59 'a and 59' b of the tongues 59 a and 59 b could, as a variant, be coupled in the position of fixing the suspension element 55, on the lower edge of the flange 63. The fixing of the suspension element 55 in - the frame 61 is made by a joint, the spring 57 is compressed against the angle wall 62 of the frame and exerts a pulling force on the tabs 59a and 59b where the projections 59 'a and 59' b are engaged in the openings against the inner edge of the flange 63. The suspension element which is furthermore hooked on the upper edge of the frame by the legs 60a and 60b is perfectly fixed on the frame. Optionally, the fixing of the suspension element can be completed by a laser welding or electric welding edge. The coupling plate 58 is crossed by an opening 64 which engages a sealed engagement pin 65, in an internal part of the slab of the cathode ray tube, in the vicinity of an angle of the slab.

Advantageously, the suspension element 55 can be obtained by cutting and folding a thin metal sheet, as shown in FIG. 14, or the cutout lines of the metal strip have been shown in full lines and the lines of bending in broken lines. The suspension element 55 could also be made in several parts mounted between them by welding.

The suspension element must be made of steel or an alloy with a high elastic limit, for example: - a Maraging steel such as a steel with 18% nickel, 9% cobalt and containing molybdenum and titanium, - a hard steel with 25% nickel, 15% chromium and containing titanium and aluminum, a hard nickel-iron alloy with the carbides such as an alloy containing 37% nickel, 2% molybdenum, 0.8% chromium and 0.25% carbon, in a state heavily stranded. This alloy has the advantage of having a weak coefficient of expansion, of the order of 2.10"V ° K, - a nickel-based superalloy with a structural hardness such as alloy 718, - certain stainless martensitic alloys All these steels and alloys they have been retained from the fact that they have a high elastic limit and keep their elasticity immediately after the necessary thermal treatments, after the production of color television tubes.The alloys used must preferably be non-magnetic. as the element 55 shown in FIGS. 13A and 13B have the advantage of being able to be fixed on a perforated mask frame although it is necessary to carry out a ligation or bonding by resistant welding. From this fact, the suspension elements can be easily disassembled since it is possible in the case where, in the course of manufacture of the frame, a control shows that the frame has not been adequately shaped, and therefore recover the frame and / or the suspension elements. In addition, a suspension without welding of the suspension element on a rigid and light frame allows to avoid the deformation of the frame, after the fixing of the element. Furthermore, the suspension element such as that described above is of a simple and inexpensive embodiment and can be put in place and fixed on the mask frame simply and quickly. The metal strips used to make the membranes constituting the sides of a perforated mask frame according to the invention may be of low carbon steel such as AK steel, of iron-based alloy, of alloy based on iron-nickel such as Invar with a weak thermal expansion, a chromium-iron alloy, a nickel-based alloy, an alloy with hardness structure or a hardness of the martensitic type, alloys that allow to considerably increase the rigidity of the structure of the frame or even a magnetic alloy, a non-magnetic alloy or an alloy that dampens vibrations. The two membranes can be of the same metallic material chosen from the materials mentioned above. The outer membrane and the inner membrane could also be of different materials, at least one of the membrane materials could be chosen from the materials listed above. The use of two different alloys can allow in particular: a) to improve the magnetic compartment of the frame using a magnetic alloy for one of the membranes and a steel with a low carbon content for the other membrane, for example a steel membrane and a membrane of a mumetal or even a steel membrane and an Invar membrane. b) improve the frequency response of the frame using an alloy that dampens the vibrations of the frequency band 100 - 400 Hz for the realization of one of the membranes. c) take advantage of the advantages of the bimetal effect inherent to a heterogeneous structure using different alloys.

In general, the metal bands used to make the membranes of the frame according to the invention are thin bands where the thickness is at least equal to 0.1 mm, then the thin frames known from the prior art have a thickness of the order of 0.2 mm. The embodiment of the frame according to the invention from two overlapping membranes allows to obtain a rigidity ten times stronger than the frame with a weight gain of 20% in relation to the thin frames known from the prior art.

It is well understood that the frame is made so as to facilitate the fixing of the perforated mask. In particular, the position of the reinforcing ribs of the membranes of the sides of the frame is provided to allow the running force and the fixing of the perforated mask without difficulty. This fixing of the perforated mask can be carried out by electric welding on the edges of the frame, which corresponds to the known technique. Perforated masks of the "extended mask" type can be manufactured using a frame where the fixing flanges have a cylindrical symmetry. In this case, the tensioning of the mask can be carried out by the bending of two sides of the frame, as explained above.

By using the alloys with a high elastic limit conveniently chosen, an extended mask frame with a very large stiffness and considerably lighter than the extended mask frames according to the prior art can be conceived. The invention is not limited to the embodiments that have been described. Thus, the frame can be manufactured using two or four portions of metal band pre-cut and pre-formed or even from a number of bands greater than four, following the way of assembly and welding of these bands and the shape of the section of the frame. It is possible to foresee the manufacture of frames where the contour is not rectangular. The cut-out band portions may or may not include angle or splice zones in addition to the areas having the shape of the flat sides of the frame. The reinforcing ribs of the membranes may have a different distribution and shape than those which have been indicated. The suspension element according to the invention may comprise a single leg and a single latching tongue on the perforated mask frame or even more than two legs and more than two latching tongues.

Claims (28)

1. - A perforated mask frame of a cathode ray tube and in particular of a color television tube having flat sides and placed following the faces or surfaces of a straight prismatic surface and having a stiffening edge for fixing a mask perforated on the frame by the intermediation of which the perforated mask is placed in a place inside a glass envelope of the cathode ray tube comprising a cone and a slab comprising a screen, characterized in that the sides of the frame comprise an outer membrane and an inner membrane spliced and fixed against each other and each constituted by a portion of a thin metal strip.

2. - The frame according to claim 1, characterized in that at least one of the outer and inner membranes is reinforced by at least one embossed part of the membrane.

3. - The frame according to claim 2, characterized in that at least one membrane is reinforced by the ribs.

4. - The frame according to claim 3, characterized in that the outer membrane and the internal membrane are reinforced by ribs and that the ribs of the outer membrane have a direction perpendicular to the direction of the ribs of the internal membrane.

5. - The frame according to claim 3, characterized in that at least one membrane comprises ribs placed along two perpendicular directions between them.

6. - The frame according to any of claims 2, 3 and 4, characterized in that the inner membrane and the outer membrane are traversed by at least one hole at the level of each of the embedded parts or reinforcement ribs .

7. - The frame according to any of claims 1 to 6, characterized in that the outer membrane and the inner membrane are fixed one over the other by welding points.

8. - The frame according to any of claims 1 to 6, characterized in that the outer membrane and the inner membrane are fixed one over the other by continuous welding lines.

9. - The frame according to any of claims 1 to 6, characterized in that the outer membrane and the inner membrane are joined together by a solder alloy material distributed in the areas between the membranes.

10. - The frame according to any of claims 1 to 9, characterized in that the outer membrane and the inner membrane are of the same metallic material.

11. The frame according to the invention 10, characterized in that the metallic material is one of the following materials: low carbon steel, iron based alloy, iron-nickel alloy, iron-chromium alloy, alloy nickel base, alloy with structural hardness, alloy with martensitic hardness, magnetic alloy, non-magnetic alloy, alloy that dampens vibrations.

12. - The frame according to any of claims 1 to 9, characterized in that the outer membrane and the internal membrane are made of different materials.

13. - The frame according to claim 12, characterized in that at least one of the materials constituting the outer membrane and the internal membrane is chosen from the following materials: steel with low carbon content, alloy based on iron , iron-nickel alloy, iron-chrome alloy, nickel-based alloy, alloy with structural hardness, alloy with martensitic hardness, magnetic alloy, non-magnetic alloy, alloy that dampens vibrations.

14. - The frame according to any of claims 1 to 13, characterized in that it comprises zones of substantially flat angle between the successive sides of the frame.

15. - The frame according to claim 14, characterized in that a device for suspending the frame in the glass envelope of the cathode ray tube is fixed by joining to the inside of at least one hole in each of the zones of angle.

16. - The frame according to any of claims 1 to 15, characterized in that it comprises an edge opposite the stiffening edge of a length of which is fixed the perforated mask constituted by a part of at least one of the outer membranes and internal of the sides of the frame bent at 90 ° towards the interior of the frame and comprising reinforcing ribs, to ensure the fixing by joining a magnetic shielding of the cathode ray tube.

17. - The frame according to any of claims 1 to 16, characterized in that it comprises two opposite and parallel sides each having an assembly edge of the perforated mask constituted by a part of at least one membrane of two sides of the frame bent towards the inside of the frame, in such a way that the mounting edges of the perforated mask are located on a same cylindrical surface.

18. - The frame according to any of claims 1 to 17, characterized in that the sides of the frame are placed following the faces or lateral surfaces of a rectangular parallelopiped.

19. - The method of manufacturing a frame for a perforated mask of a cathode ray tube such as a color television tube having the plate-shaped sides or planes placed substantially following the faces or side surfaces of a straight prismatic surface, characterized due to the fact that at least one thin metal walker, at least one first membrane and at least one second membrane comprising, following the length of the metal strip, at least one area having the shape of a flat side of the metal strip are cut out. a frame to be made, in order to obtain, for each of the sides of the frame to be made, a first membrane and a second membrane that can be superimposed, which is carried out in each of the zones of the first and second membranes of the embossed parts or reinforcing ribs by the deformation of the corresponding metal strip, and that the frame is assembled by welding the membranes in the the provisions spliced against each other.

20. - The method according to claim 19, characterized in that the first and second membranes further comprise at least one angle or splice area adjacent to an area having the shape of a flat side of the frame.

21. - The method according to any of claims 19 and 20, characterized in that the folding is performed and the first and second membranes are put in place against each other following the shape of the frame to be made, and - that the first and second membranes are joined together against one another and are maintained following the shape of the frame to be made.

22. - The method according to any of claims 19 and 20, characterized in that the first and second membranes are superimposed, so that the corresponding areas on the same side of the frame are superimposed, - that the ligation of the membranes in their superimposed position, and - that the bending and assembly of the superimposed membranes are made and joined together to obtain the frame.

23. The method according to claim 22, characterized in that the bonding or ligation of the membranes is carried out in an overlapping position by spreading an alloy layer for welding on a face or surface of the first membrane, superimposing the second membrane on the surface of the first membrane on which the product of the welding alloy is deposited and finally, bringing the superimposed membranes to a welding temperature.

24. - The method according to any of claims 19 and 23, to realize a frame where the flat sides are placed following the lateral surfaces of a rectangular parallelopiped, characterized in that the first membrane and the second membrane comprise following its length four zones that have the shape of four sides of the frame in the form of a rectangular parallelepiped, three angle zones, sandwiched between two zones corresponding to two sides of the frame and a zone of connection to one of the ends of the membrane.

25. - The method according to any of claims 19 and 23, for the manufacture of a frame where the flat sides are placed following the side faces of a rectangular parallelopiped characterized by the fact that two first membranes and two second membranes are cut out. Each first zone corresponding to a first side of the frame comprises a second area corresponding to a second side of the frame, an area of angle between the first and second zone and a zone of connection to one of the ends of the membrane .

26. - The suspension element of a perforated mask frame inside a slab of a cathode ray tube comprising a plate crossed by a coupling opening of the suspension element on a paw integral with the slab of the cathode ray tube and means for fixing the suspension element on a wall of the frame, characterized in that the fixing means of the suspension element on the wall of the frame comprise: a mounting plate integral with the plate having at least one hooking leg one edge of the wall of the frame, - a spring projecting on an internal surface of the upright that comes into contact with the wall of the frame, and - at least one tongue substantially perpendicular to the upright and directed towards the interior of the frame comprising a projection of hook on its end directed towards the inside of the frame to realize the fixing of the suspension element on the b Assembling by joining, the latching projection of the tongue is coupled by a retaining member of the frame and the compressed spring between the assembly and the wall of the frame.

27. - The suspension element according to claim 26, characterized in that it is constituted by a thin metal sheet cut out and bent.

28. - The suspension element according to any of claims 26 and 27, characterized in that it is made of a metallic material with a high elastic limit and chosen from the following materials: - Maraging steel - steel with 25% nickel and 15% chromium, which contains titanium and aluminum, - nickel-iron alloys, - nickel-based superalloys, - stainless martensitic alloys.