EP0809272B1 - Shadow mask frame of a cathode ray tube and method of fabricating the same - Google Patents

Abstract

Device for fixing the element on the frame wall comprises: upright (56) attached to plate having at least 2 locking tabs (60a, 60b) on the side of the frame (61) wall (62); spring (57) projecting on to an internal face of upright (56) coming into contact with the frame wall; and at least one strip (59a, 59b) comprising fixing bar (59'a, 59'b) at its end to attach the element on frame by clipping. The fixing bars (59'a, 59'b) of the strip (59a, 59b) are engaged on an element for retention of the frame (61) and the spring (57) compressed between the upright (56) and the wall (62) of the frame (61). The suspension element consists of a thin metal strip cut out and bent.

Description

The invention relates to a shadow mask frame a cathode ray tube and in particular a tube of color television.

Color television tubes with shadow mask have a glass envelope in which are fixed metal parts of which one is made by the perforated screen secured to a frame and another by a magnetic shield placed inside the envelope of glass.

The glass envelope consists of two parts, a slab including the screen on which is formed the image and a cone on which are fixed the electron guns and the deflection coils of electron beams from the cathode ray tube.

The shadow mask is made from a thin metal strip in which small holes dimensions and adapted shape are produced by machining chemical. The metal bands used are generally low carbon steel or iron-nickel alloy such than Invar. The shadow mask is shaped by stamping hot or cold, so as to present a peripheral edge along which a frame is welded metallic.

The set consisting of the frame and the mask is fixed inside the glass slab, via suspension devices attached to the frame and coming to engage on pawns sealed in the glass of the slab.

The internal shielding of the tube can be fixed either on the frame of the shadow mask, or on the pawns of fixing sealed in the glass of the slab.

We know cathode ray tubes of different types which are distinguished in particular by the type of mask or the type of frame used or again by the method of hanging the frame inside the glass envelope of the tube.

Regarding the different types of framework used, we distinguish in particular thin frames and light whose thickness can be for example of 0.2 mm and thick, rigid and heavy frames.

Regarding the hanging methods of the frame inside the glass wrapped, there are hanging the frame near the corners of the screen and hanging the frame from the middle of the edges slab peripherals, via devices bimetallic compensation fixed on the surface outside of the sides of the frame.

The suspension of the shadow mask, via of its frame, inside the envelope of Glass of the tube must allow to fulfill several functions.

First of all, this suspension must allow control the relative movements of the glass screen and of the shadow mask which are caused in particular by dilation of the shadow mask which heats up under impact of the electron beam, so as to maintain the color purity of the image formed on the screen.

On the other hand, the suspension devices must keep the shadow mask in position inside of the glass envelope, even when the tube to cathode rays receives a shock, and protect the mask perforated against external mechanical stress.

Finally, the suspension systems must allow dismantle or move the mask while manufacturing the cathode ray tube and then replace inside the glass envelope, as many times as it may be necessary.

• d'une part, il doit permettre d'accommoder les variations de dimension résultant d'un échauffement global de l'ensemble,
• d'autre part, il doit présenter une grande stabilité mécanique.

The assembly consisting of the shadow mask, the frame and the frame suspension devices must in particular have the following two properties:

• on the one hand, it must make it possible to accommodate the variations in dimension resulting from an overall heating of the whole,
• on the other hand, it must have great mechanical stability.

Most of the known sets of the state of technique use a steel frame, thick, heavy and rigid, hung with three or four springs bimetallic engaged on pawns sealed to the game median of the peripheral edges of the glass slab. The disadvantages of such known sets are that the framework has a large thermal inertia and that the mode of compensation for variations of dimension of thermal origin is not completely symmetrical.

It is also known to use frames in thick, heavy and rigid steel which are hung in the corners of the slab using four systems of suspension. This symmetrical arrangement presents the advantage of performing thermal self-compensation; however, the frame still has too much thermal inertia.

In addition, the thick frames known from the prior art are often too heavy which can be for example of the order of or greater than 2 kg, in the case of so-called "stretched mask" technologies, the mask perforated being tensioned on the frame whose rigidity must be sufficient to withstand the stresses resulting from the tensioning of the mask.

It is also known to use frames thin whose thickness can be for example of the order 200 µm, these light frames being hung in the corners of the slab.

These thin frames have the advantage of having a low thermal inertia but are very large fragility, due to their small thickness. These frames also have insufficient rigidity. Therefore, it may be necessary to weld hangers on the fixing pins to avoid dropping out of the frame. The manufacturing of the cathode ray tube is thus made more complex.

The object of the invention is therefore to propose a mask frame perforated with a cathode ray tube and in particular a color television tube having flat sides arranged substantially along lateral faces with a straight prismatic surface and having a stiffening edge for fixing the shadow mask on the frame through which the shadow mask is placed inside a glass envelope cathode ray tube which has a cone and a slab comprising a screen, this frame having good mechanical rigidity, the lowest possible weight, for a given rigidity, a low thermal inertia and other benefits, such as limited sensitivity to external periodic stresses, in a range frequency ranging for example from 100 to 400 Hz.

For this purpose, the flat sides of the frame have an external membrane and an internal membrane added and fixed one against the other and each constituted by a portion of thin metal strip.

A shadow mask frame according to the present invention is defined in claim 1. A method of manufacturing a mask frame perforated according to the present invention is defined in claim 19.

Preferably, in order to increase the mechanical rigidity of the frame, at least one of the outer membranes and internal is reinforced by at least a stamped part of the membrane.

According to a preferred embodiment, one of the membranes, or both membranes are reinforced by ribs.

In order to clearly understand the invention, we will now describe, by way of nonlimiting examples, in referring to the attached figures, several embodiments of a following mask mask the invention.

Figure 1 is an exploded perspective view a cathode ray tube with a shadow mask.

Figures 2A and 2B are plan views of metal strips cut before shaping, of so as to constitute an outer membrane and a membrane internal respectively of a mask mask according to the invention and according to a first embodiment.

Figures 3A and 3B are plan views of cut and shaped metal strips, of so as to constitute an outer membrane and a membrane internal respectively, of a mask mask according to the invention and according to a second embodiment.

Figure 4 is an exploded perspective view showing the folding formatting and assembly of two metal bands as shown on the Figures 2A and 2B, when making a frame shadow mask according to the invention and according to the first embodiment.

Figure 5 is a top view of the bands shown in Figure 4, in their assembly position before welding.

Figure 6 is a top view, similar to the view of FIG. 5, showing strips of sheet metal such as shown in Figures 3A and 3B, in their assembly position before welding.

Figures 7A, 7B, 7C and 7D are views in vertical section along 7-7 of figure 5 or of Figure 6 showing an outer membrane and a membrane internal of a shadow mask frame according to the invention in their assembly position as well as part of a mask in assembly position on the frame.

Figures 8A, 8B and 8C are plan views showing the welding areas of an internal membrane and an outer membrane of a shadow mask frame according to the invention, attached and fixed one against the other.

Figure 9A is a perspective view of a mask mask according to the invention in the assembled state.

Figure 9B is a top view of an area angle of the frame shown in Figure 9A.

Figure 9C is an elevation view of the area angle of the frame shown in Figure 9B.

Figure 10 is a plan view of a membrane outer and inner membrane of a mask frame perforated 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 mask mask according to the invention allowing to implement "stretch mask" technology.

Figure 12A is a perspective view of a part of one side of a shadow mask frame next the invention and according to an alternative embodiment.

Figure 12B is a sectional view along 12B-12B in Figure 12.

Figure 12C is a sectional view along 12C-12C in Figure 12.

In Figure 1, we see the different parts constituting a cathode ray tube with mask perforated used as color television tube.

The cathode ray tube, designated in its together by mark 1, has a glass envelope consisting of a cone 2 and a slab 3 and two pieces metal 4 and 9 which are attached inside of the glass envelope of the tube.

Part 4 is a pre-assembled assembly comprising the shadow mask 5 consisting of a metal sheet crossed by openings 6, the frame 7 of the mask perforated and assembly suspension devices 8 4 inside the slab 3 of the glass envelope.

Part 9 is a shaped metal wall so as to constitute an internal magnetic shielding engaged in cone 2 of the glass casing, the most often attached to the frame.

The cone 2 of the glass envelope has a rectangular base with rounded corners and a curved wall having a shape close to that of a cone whose section decreases towards the posterior end cathode ray tube 1 at which are attached to the cone 2 the electron guns and the coils of deviation of the cathode ray tube.

Slab 3 has a slightly curved wall 3a constituting the screen of the cathode ray tube and a ledge 3b including rectangular base with rounded angles can be perfectly superimposed with the base of the cone 2. On the internal surface of the edge 3b of the slab 3 are fixed pawns such as 10 projecting inward allowing the attachment of the assembly 4 comprising the shadow mask 5 and the frame 7, via of 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 pawns of fixing 10 fixed in the middle part of the edges of the slab intended to cooperate with the suspension devices 8 fixed in a middle position on the sides of the frame 7 of the shadow mask 5.

In FIG. 1, the constituent parts of the tube 1 have been represented before their assembly to constitute the cathode ray tube.

To manufacture and assemble the cathode ray tube, we manufacture, separately, component parts 2 and 3 of the glass envelope, assembly 4 and the shielding magnetic 9. These parts are then assembled, as it will be described below.

The shadow mask 5 is made from a thin strip in which holes 6 are made by machining chemical. The perforated sheet is then shaped by hot or cold stamping to form a mask 5 comprising a peripheral assembly rim substantially rectangular in shape with rounded corners.

Frame 7 is fixed by welding to the edge mask mask assembly 5. The fixing 8 are then welded to the edges of the frame. The assembly 4 thus produced is fixed inside the slab 3 after various heat treatments.

The magnetic shield 9 is then fixed, by example by clipping, on frame 7. In certain modes of realization, it is necessary to fix the shielding on the pins sealed on the inner wall of the slab.

The glass envelope can then be assembled.

As explained above, in the case cathode ray tubes with shadow mask according to prior art, no frame has ever been made for the perforated mask which has both a very large mechanical rigidity, weight and thermal inertia weak and may also have limited sensitivity to periodic stresses in certain ranges of frequency.

The frame for a shadow mask according to the invention which will be described below overcomes the drawbacks devices according to the prior art.

In FIGS. 2A and 2B, there is shown, respectively, an outer membrane 11 and a membrane interior 12 of a shadow mask frame according to the invention.

The membranes 11 and 12 are made from of a strip of thin sheet or strip of material metallic, such as steel, iron-nickel alloy or another alloy.

The strip of thin metal sheet is cut out following an external contour allowing to delimit four zones 11a, 11b, 11c, 11d or 12a, 12b, 12c, 12d depending on the length of the strip, intended to constitute the membrane outer and inner membrane, respectively, of each sides of the mask mask, during assembly bands 11 and 12 to make a frame whose flat sides are arranged along the side faces of a rectangular parallelepiped.

Zones 11a and 11c on the one hand and 12a and 12c on the other hand bands 11 and 12 respectively are of identical form and are intended to constitute the membranes on one side of the frame.

Zones 11b and 11d on the one hand and 12b and 12d on the other hand bands 11 and 12 respectively are of identical form and are intended to constitute the membranes on the short sides of the frame.

Between two successive zones intended to constitute membranes on the sides of the frame and at one of the ends of the strip 11 or 12, zones are provided angle or connection 11e, 11f, 11g and 11h for the band 11 or 12e, 12f, 12g and 12h for band 12.

In each of the zones intended to constitute a internal or external membrane on one side of the frame, the metal strip is shaped, for example by stamping or burnishing, to present ribs of reinforcement parallel to each other.

The successive zones of the strip 11 intended for constitute the outer membranes of the frame include ribs 13 parallel to the longitudinal edges of the bandaged.

The zones of the strip 12 intended to constitute the inner membranes on the sides of the frame have ribs 14 perpendicular to the longitudinal edges of the band.

It would also be possible to provide ribs reinforcement parallel to the longitudinal edges tape in the areas intended to constitute a membrane of a large or a small side of the frame and reinforcement ribs perpendicular to the edges longitudinal of the strip in the areas intended for form a membrane on the other sides of the frame. So, the same strip may comprise in successive zones, longitudinal direction ribs and ribs perpendicular to the longitudinal direction.

In addition, the corner and connection areas may also have ribs 15 (in the case of band 11) or 16 (in the case of band 12) which are perpendicular to the ribs 13 or 14 of the zones constituting the membranes of the sides of the frame.

The sheets 11 or 12 are drilled, at the level of each of the ribs 13, 15, 14 and 16, of holes 17 or 18 crossing the strip over its entire thickness, so to avoid trapping gases between the internal membranes and external of the sides of the frame, when the membranes are brought together and welded together, as will be described below.

In addition, at least one of the two bands (the band external 11 in the case of the embodiment shown in FIGS. 2A and 2B) comprises, according to one of its edges, tabs 19 at each of the successive zones constituting a membrane of a wall of the frame and at the corner and connection areas.

As seen in Figure 7B, when the strip is folded to form a frame, legs 19 are folded inward at 90 ° to the plane of band 11.

It is also visible in FIG. 7B that a part 20 of the upper edge of the strip 11, of a width lower than the lower edge 19, is also folded inward at 90 °, which contributes to stiffening of the frame. The shadow mask 5 is attached and welded along the upper edge 20 of the frame.

In FIG. 7B, the shadow mask has been represented 5 in the assembly position. The rim 5a of the mask 5 is fitted against the upper part of the membrane outside of the frame, along the edge 20 folded inwards of the frame. The welding of the mask is carried out by the outside of the frame, as shown by arrow 51.

In FIG. 7C, a variant of creation of the mask frame and method of attachment perforated 5. The edge 20 of the outer membrane of the frame is folded out of the frame and the rim 5a of the mask 5 is fitted against the internal membrane of the frame on along edge 20. Welding can be done from the outside (arrow 51) or from inside the frame (arrow 51 '). Alternatively, the stiffening edge 20 could be achieved by folding the top edge of the internal membrane outwards above the membrane outer and the rim 5a of the mask 5 welded to the internal membrane.

In FIG. 7D, the case of a frame with stretched mask. In this case, the edge 20 and the mask 5 have the shape of cylinder portions to circular section. Mask 5 is attached to the edge 20 and fixed to edge 20 by welding. We will describe in more detail later, mounting a mask on a frame according to the invention, in the case of the technique "with stretched mask", referring to FIG. 11.

As shown in Figure 7A, in some case, the inner membrane of the frame may have also a flange 19 'folded 90 ° inwards and superimposed on the edge 19 of the outer membrane.

After performing the cutting, forming and drilling the strips 11 and 12, the assembly is carried out and forming the frame.

According to a first example of illustrated implementation in FIGS. 4 and 5, the assembly by welding of the outer and inner membranes of the frame is made after folding of the strips 11 and 12 constituting these membranes.

According to an alternative embodiment which will be explained opposite FIG. 10, the assembly by welding outer and inner membranes of the frame in positions can be superimposed before folding the membranes.

In the case of the first example of implementation, a part of the edge of the strip 11 is folded intended to constitute the external membrane, located opposite lugs 19, to constitute the stiffening rim 20 along which the shadow mask is attached. In some cases, it is also possible to fold the corresponding edge of the strip 12 constituting the internal membrane, stiffening rim along which is attached the shadow mask then being made by the juxtaposed edges of the outer membranes and internal.

Then fold the tabs 19 of the strip 11 inward, as shown in Figures 7A and 7B.

Corresponding legs 19 'can be provided on the strip constituting the internal membrane 12, these legs 19 'are also folded inwards at 90 °.

The band 11 constituting is folded the outer membrane, as shown in Figure 4, the along the edges perpendicular to the longitudinal edges of the strip delimiting the corner areas 11e, 11f, 11g and the connection area llh. We place the strip 11, after folding, inside-a template to maintain the zones of the strip located between two corner zones along the side faces of a parallelepiped rectangle, as shown in figure 5. We assure then maintaining the external strip 11 in the form given by the template, by welding one on the other of tabs 19 constituting one of the folded edges of the strip then we introduce the strip 12, after folding, as shown in Figures 4 and 5, inside the strip 11 constituting the folded and pre-assembled outer membrane according to the required form.

The folded strip 12 is introduced inside the strip 11 folded and pre-assembled, in a layout as shown in Figure 5, i.e. with zone 11d of strip 11 opposite zone 12b of the strip 12. In this way, the connection zones 11h and 12h of bands 11 and 12 respectively are in corners of the frame located at the ends of a diagonal.

After placing the folded strips 11 and 12 in their position shown in FIG. 5, the welding of superimposed strips, in particular to produce the fixing of the 11h and 12h connection zones against a corner area opposite, as shown by the arrows 24.

Welding can be electric welding or a laser or plasma welding. We can also use solder as long as it is compatible with vacuum resistance and performance requirements to be expected from the cathode ray tube.

The embodiment of the framework which has been described opposite Figures 4 and 5 uses two bands 11 and 12 as shown in Figures 2A and 2B.

It is also possible, according to a second mode of realization, to realize a frame using four cut and shaped strips, two of these strips constituting an outer membrane of the frame and the two other bands constituting the internal membrane.

In Figures 3A and 3B, there is shown respectively a strip 21 constituting part of a membrane outer of a shadow mask frame according to the invention and a cut strip 22 constituting a part an inner membrane of a mask mask according to the invention and according to the second embodiment.

To make the frame, we use two bands such as band 21 and two bands such as band 22 which are assembled after folding, as shown in Figure 6.

The strip 21 has two successive zones 21a and 21b intended to constitute the outer membrane of a large side and a small side respectively of the frame of shadow mask.

Likewise, the strip 22 comprises two successive zones 22a and 22b intended to constitute the membranes internals on one large side and one small side of the frame for shadow mask. In the same way as bands 11 and 12 shown in FIGS. 2A and 2B, the bands 21 and 22 have corner zones between the zones intended to form the membranes on the sides of the frame and a connection zone at one of their ends. he it is not necessary to describe in detail the bands 21 and 22 which are produced analogously to the bands 11 and 12 and which correspond to half of these bands in the longitudinal direction.

To make the frame for a shadow mask, as shown in FIG. 6, two bands 21 and 21 'intended to constitute the external 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 arranged in a template so that the areas of bands such as 21a and 21b are arranged according to the lateral faces of a rectangular parallelepiped. We realize then a pre-assembly of the bands 21 and 21 'according to the defined parallelepiped contour, by welding between them tabs or tabs 23 provided along an edge longitudinal of the strip 21 and folded 90 ° inward.

The strips 22 and 22 'are folded and inserted inside the frame formed by the bands 21 and 21 ' folded and pre-assembled in a parallelepiped shape and kept inside the template.

The bands 22 and 22 'are introduced, after folding, inside the external frame formed by bands 21 and 21 ', so that their end zones 22h and 22h connection are located opposite of two corner zones of the bands 21 and 21 'respectively and aligned on a diagonal of the outline defined by the bands 21 and 21 'pre-assembled different from the diagonal according to which the connection zones are aligned 9 p.m. and 9 p.m. of bands 21 and 21 'respectively.

The strips 21, 21 ′ are then welded, 22 and 22 'reported against each other in the provision shown in Figure 6. In particular, we welds the strip connection areas along the four corners of the frame, as shown by arrows 25.

Referring to Figures 7A and 7B which represent a simplified sectional view of the constituent bands respectively the outer membrane and the inner membrane of the frame, during the welding of these strips one on the other, we see that, in the assembly position, the ribs 13 of the outer strip 11 (or 21) are directed outwards and the ribs 14 of the internal strip 12 (or 22) are directed inwards, so that flat areas for connecting the external strips and internal are reported against each other in their welding position. Welding is carried out in these areas planes brought together against each other, from the inside or outside the frame, as shown by the arrows 26 and 26 '.

The external tapes and internal have the same width and the same thickness, these dimensions can be adapted according to characteristics sought for the mask frame perforated.

However, the internal membrane must cover the largest possible surface of the outer membrane between its upper edge for fixing the shadow mask and its edge cut in the form of a tongue and folded inwards.

The internal membrane may or may not have an edge 19 'folded inwards superimposed on edge 19 (or 23) of the outer membrane.

In FIGS. 8A, 8B and 8C, there is shown a internal membrane 12 attached and welded to a membrane external 11 and constituting one side of a mask frame perforated according to the invention.

The embodiments illustrated by the figures 8A, 8B and 8C differ in the type of welding performed to connect the two membranes arranged so superimposed.

The membranes 11 and 12 have ribs of reinforcement 13 and 14 respectively which are arranged in directions perpendicular to each other. The membranes 11 and 12 are crossed by openings 17 and 18 at each of the ribs 13 and 14, of so that the space between a rib of a membrane projecting inward or outward and the surface of the other membrane is put in communication with the outside. This avoids trapping gases inside the walls of the frame, such occluded gases risking disturbing the operation of the spoke tube cathode.

In the case of the embodiment shown in FIG. 8A, the welding of the membranes 11 and 12 has been produced by solder points 27.

The weld points 27 are aligned along the two longitudinal edges of the membranes 11 and 12 and interposed between the ribs 13 and 14.

In the case of the embodiment of the assembly membranes 11 and 12 shown in FIG. 8B, the connection of the two membranes is carried out by lines continuous welding 28. In particular, two continuous welding lines 28 along the longitudinal edges membranes 11 and 12, welding lines surrounding the reinforcing ribs 13 and 14 and generally closed welding lines between the ribs reinforcement 13 and 14.

In the case of the embodiment shown in FIG. 8C, the connection between the membranes 11 and 12 is made by distributing a solder paste in certain zones 29 located between membranes 11 and 12 and while wearing the frame pre-assembled at a brazing temperature, inside an oven. The connection is thus made by brazing of the two membranes 11 and 12, in zones 29.

Preferably, the zones 29 are arranged according to the longitudinal edges of the membranes 11 and 12 and between the reinforcing ribs 13 and 14.

It turned out that the embodiment shown in FIG. 8B in which the membranes 11 and 12 are connected by continuous welding lines is the preferred embodiment ensuring the best bonding of membranes 11 and 12 added one against the other.

In FIG. 9, the frame of shadow mask 30 in its assembled and welded state.

The frame 30 shown in Figure 9 includes four flat sides 30a, 30b, 30c and 30d arranged along four side faces of a rectangular parallelepiped.

Each of the flat sides of the frame 30 is constituted an outer membrane 31 and an inner membrane 32 attached and welded together.

The outer membranes and the inner membranes each of the four sides of the frame can be made from one or more metal strips. Membranes internal and external membranes are reinforced by ribs which have perpendicular directions between them.

Between two successive flat sides, the frame has a flat corner area 33 on which can be fixed a device 34 for hanging the frame inside of the glass envelope of the cathode ray tube.

The corner areas 33 of the frame may include through holes for fixing by clipping of the suspension device 34. It is thus possible achieve effective attachment of suspension devices without resorting to welding operations. Mon edges of the frame, which will be designated as the top edge 35, due to its arrangement in FIG. 9, is used to increase the rigidity of the structure. The edge upper 35 of frame 30 is made by folding towards inside or outside one of the longitudinal edges of one of the membranes 31 and 32, preferably the edge longitudinal of the outer membrane 31, or possibly by folding the longitudinal edges arranged opposite of the outer membrane 31 and the inner membrane 32. As explained above, the shadow mask is fixed on the frame, along the upper edge of the frame 30.

The edge of the outer membrane opposite edge 35, called lower edge, is also folded inwards to constitute tabs 36 used in particular for carrying out the pre-assembly of the frame 30. It is also possible to provide tabs foldable, on each side of the frame, both with respect to the outer membrane 31 as for the inner membrane 32. In this case, the lower folded edge of the frame 30 is constituted by the tabs superimposed and welded together the outer membrane 31 and the inner membrane 32.

The tabs 36 folded towards the inside of the frame may have reinforcing ribs 37. The membranes may have through openings 38 at each of the reinforcing ribs 37.

In this case, the tongues 36 reinforced by ribs, folded inwards and welded between them, constitute a set of great rigidity on which it is possible to fix the magnetic shielding of the cathode ray tube, for example by clipping.

As can be seen in Figures 9A and 9B, two tongues 36 on two successive sides of the frame 30, for example the sides 30b and 30c are fixed one by compared to the other by a cut tab 36 ', by example, in the lower part of the outer membrane, directly above corner area 33.

The tongue 36 'is in the folded position towards inside at 90 °, superimposed on the end parts of the tabs 36 and fixed thereon by points of welding 39. This operation is carried out during pre-assembly the frame inside a template giving its shape.

We can then carry out the installation of the internal membrane 32 inside the pre-assembled frame and held in the template to weld it against the pre-assembled outer membrane.

In Figure 10, two metal bands are shown 41 and 42 cut and shaped so to be able to constitute the external membrane and the membrane internal respectively of a frame for shadow mask according to the invention.

The membranes 41 and 42 are made of a substantially identical to membranes 11 and 12 shown in Figures 2A and 2B respectively. In particular, bands 41 and 42 are cut from so as to present zones distributed according to the length of the strip intended to constitute the membranes external and internal of the flat sides of a frame, arranged along the side faces of a parallelepiped rectangle. These areas are separated by corner areas. The fold lines of the membranes 41 and 42, during the realization of the frame are the lines perpendicular to the longitudinal direction of the corresponding strip separating the corner areas from the areas intended to constitute the sides of the frame.

The outer membrane 41 has an edge, called lower edge, along which tabs are cut 43 which are folded 90 ° towards the inside of the frame, before folding and shaping the frame.

The opposite longitudinal edge of the membrane 41 is folded in or out at 90 °.

Cutting and folding inward of edges of the membrane can be made only for the outer membrane or on the membrane external and also on the internal membrane.

The metal bands constituting the membranes 41 and 42 are each cut at one of their ends to present a connection zone 44 or 45, these connection zones being attached to each other and welded, after folding strips 41 and 42, when of the frame assembly.

The assembly and welding of the frame constituted by the metal bands 41 and 42 shown on the figure 10 are carried out according to a variant of the first embodiment described above.

The manufacture of membranes 41 and 42 from metal strips is made in the same way as in the case of the first embodiment. In particular, each zone such as 41a and 42a bands 41 and 42 intended to constitute the outer and inner membranes on one side of the frame, reinforcing grooves, for example by stamping or by burnishing.

In the case of the first embodiment, we successively folded the strips and their welding assembly.

In the case of the variant, one realizes in a first welding of the overlapping strips before folding them, then folding the double strip obtained and finally the welding of the connection zones.

Preferably, the strips are welded one on the other in a position superimposed by brazing.

In order to perform the soldering, we spread in different zones of one of the bands, for example band 41 intended to constitute the external membrane, a paste with brazed.

The solder paste can be distributed in each zones intended to constitute a membrane of one of the sides of the frame, as shown in Figure 8c.

The solder paste is placed on the face of the strip 41 opposite the face with respect to which the reinforcing ribs protrude.

It is superimposed on the strip 41 covered with dough braze the strip 42, so that the strip 42 comes rest on the strip 41 via its face opposite to the face with respect to which the ribs are protruding.

When placing the strip 42 on the strip 41, area 42a is reported over area 41a, as shown by arrow 40. In this way, the strip double obtained by superposition of bands 41 and 42 has at its ends the two connection zones 44 and 45.

The connection is made by brazing the strips 41 and 42 by inserting the bands 41 and 42 in position superimposed in a passage oven. At the temperature of oven, the solder paste ensures the connection by brazing of two bands 41 and 42 in superimposed position.

Then we fold the double strip obtained, along the transverse lines separating the corner zones of the zones constituting the membranes of sides of the frame. We then carry out the pre-assembly of the frame by welding one on the other of the tongues 43 cut from the bottom edge of the strip 41 which have been folded inwards.

The frame is closed by welding the connection zones 44 and 45 reported one on the other.

As in the case of the first and second modes of embodiment, the shape of the frame by folding is imposed and maintained by a parallelepiped-shaped template rectangle.

It is however preferable to make the frame as described above with reference to FIGS. 4, 5 and 6.

In Figure 11, there is shown a frame 46 according to the invention comprising two opposite sides 47a and 47b of which one of the longitudinal edges is cut to present an arc-shaped shape and folded towards the inside to form a 48a or 48b ledge of shape cylindrical. Edge 48a on side 47a and edge 48b of side 47b of the frame 46 are carried by the same surface cylindrical with axis ZZ '.

Edges 48a and 48b allow fixing by welding on the frame 46, of a perforated mask which thus found arranged and maintained along a surface cylindrical with axis ZZ '.

The frame 46 makes it easy to carry out the mounting of a shadow mask of the "stretched mask" type.

For this, as indicated by arrows 49 and 49 ', a force F is exerted on the faces 47a and 47b realizing bending of the sides 47a and 47b of the frame towards inside the frame and on the faces 47c and 47d a force F 'in such a way that the deformation of the edges 48a and 48b is a translation.

We weld the mask on the edges 48a and 48b while maintaining the force ensuring the flexion of the sides 47a and 47b of the frame.

After welding the shadow mask, the bending forces F and F ', so that the sides 47a and 47b of the frame return towards the outside by elasticity and ensure tensioning of the mask perforated.

The frame 46 according to the invention therefore makes it possible to very quickly and easily implement the stretch mask technique, avoiding the use of a frame massive, heavy and rigid.

The frame 46 may also include, along its face opposite edges 48a and 48b, a cut edge in the form of tongues 50 reinforced with ribs which are folded 90 ° towards the inside of the frame. In In this case, the magnetic shielding of the cathode ray tube may be fixed on the reinforced tabs 50 connected between them by welding.

Figure 12 shows a side 51 of a following frame the invention and according to an alternative embodiment.

The sides of the frame, such as side 51 are consisting of an outer membrane 51a and a membrane internal 51b reported and fixed one against the other. With respect to the embodiments which have been described previously, the membranes are not ribbed and are formed by folded thin metal strips and / or stamped, so as to present parts of plane junction coming into contact with each other and according to which the membranes are welded. As can be seen in FIGS. 12A and 12B, the membranes 51a and 51b can be welded to each other the other along the upper edge 52 and along the edge lower 53 of the frame. In addition, the membranes include stamped areas 54 of substantially square shape repelled inward on the side of the frame coming in contact and welded two by two when assembling the membranes, as seen in Figure 12A (parts stamped 54a and 54b).

At least one of the membranes 51a, as it is visible in Figure 12, or the two membranes if necessary are pierced with through holes 55 allowing avoid trapping gases in the internal space of the frame wall.

In addition, the outer membrane 51a is folded at its upper part and at its lower part to constitute stiffening and mounting edges of the shadow mask.

The frame produced as shown in the figures 12, 12A and 12B whose membranes are not ribbed has overall torsional and bending stiffness which is slightly less than the overall stiffness of a frame made from ribbed metal strips, as previously described. We observe a modification of the amplitude of certain modes of vibration of the structure of the frame.

Of course, in the case where the frame is made from non-ribbed membranes, these membranes can be joined together, by welding, according to one any of the assembly methods shown on the Figures 8A, 8B and 8C.

Good rigidity of the frame structure can be obtained when the contact surface of the two membranes, for example represented by the welded zone 29 on Figure 8C, is much smaller than the stamped surface membranes according to which the membranes are separated one from the other.

It is also possible to make the frame from a stamped metal strip and a strip unpressed metal, fully flat. We keep again, in this case, sufficient rigidity of the structure of the frame but we modify the vibration modes of this structure.

In general, we can optimize the rigidity of the structure according to the number and the width of ribs formed on the membranes. It is possible, in particular, to increase the number of ribs as much as the surfaces allow or even limit the number of ribs and increase the surface of these ribs. The ribs can also communicate with each other to form a single volume.

The shadow mask frame according to the invention whose flat sides consist of two membranes welded together, especially in the case where the membranes are ribbed, a very large mechanical rigidity in bending, torsion and tension and compression, in the case of static stresses. In addition, due to its production from strips thin metal, its weight remains very low for a rigidity sought in the case of the manufacture of cathode ray tubes with shadow mask.

In addition, we were able to show that the frame according to the invention has a limited sensitivity to external periodic requests in a range of frequencies from 100 to 400 Hz.

The framework according to the invention also has a structure to facilitate assembly of the perforated mask inside the glass envelope of the cathode ray tube, for example using suspension elements fixed to the frame by clipping and also the fixing of the magnetic shielding of the tube cathode.

The metal bands used to make the membranes constituting the sides of a mask frame perforated according to the invention can be made of low steel carbon such as AK steel, an iron-based alloy, iron-nickel alloy such as Invar at low thermal expansion, iron-chromium alloy, alloy nickel-based, structural hardening alloy or hardening of the martensitic type, these alloys allowing to considerably increase the rigidity of the structure of the frame or of magnetic alloy, non-magnetic alloy or alloy damping the vibration.

The two membranes can be of the same material metallic chosen from the materials listed above.

The outer membrane and the inner membrane could also be in different materials, at least one of the materials of the membranes being chosen among the materials listed above.

a) d'améliorer les performances magnétiques du cadre en utilisant un alliage magnétique pour l'une des membranes et un acier à bas carbone pour l'autre membrane, par exemple une membrane en acier et une membrane en mumétal ou encore une membrane en acier et une membrane en Invar.

b) d'améliorer la réponse en fréquence du cadre en utilisant un alliage amortissant les vibrations dans la bande de fréquences 100 - 400 Hz pour réaliser l'une des membranes.

c) de tirer parti des avantages de l'effet de bilame inhérent à une structure hétérogène utilisant des alliages différents.

The use of two different alloys can allow in particular:

a) improve the magnetic performance of the frame by using a magnetic alloy for one of the membranes and a low carbon steel for the other membrane, for example a steel membrane and a mumetal membrane or a steel membrane and an Invar membrane.

b) to improve the frequency response of the frame by using an alloy dampening the vibrations in the frequency band 100 - 400 Hz to produce one of the membranes.

c) to take advantage of the advantages of the bimetallic strip effect inherent in a heterogeneous structure using different alloys.

In general, the metal strips used to make the frame membranes according to the invention are thin strips the thickness of which is more equal to 0.1 mm, while the known thin frames of the prior art have a thickness of the order of 0.2 mm. The realization of the frame according to the invention from two superimposed membranes provides rigidity ten times stronger from the frame with weight gain 20% compared to the thin frames known in the art earlier.

Of course, the frame is made so as to allow and facilitate the attachment of the shadow mask. In particular, the position of the reinforcing ribs membranes on the sides of the frame is provided to allow fitting and fixing the shadow mask without difficulty. This fixation of the shadow mask can be carried out by electric welding on the edges of the frame, which corresponds to the known technique.

Perforated masks of the "stretched mask" type can be manufactured using a frame whose fixing edges have a cylindrical symmetry. In in this case, the mask can be tensioned by bending on two sides of the frame, as it was explained above.

Using alloys with high elastic limit suitably chosen, we can design a framework for stretched masks with very high rigidity and a lot lighter than state mask frames of the prior art.

The invention is not limited to the embodiments that have been described.

This is how we can make the frame in using two or four portions of metal tape precut and preformed or from a number of bands greater than four, depending on the mode assembly and welding of these strips and the form of the frame section. It is of course possible to consider the production of frames whose outline is not rectangular. The cut strip portions may or may not include corner or connection in addition to side shaped areas frame dishes.

The reinforcing ribs of the membranes can have a different distribution and shape of those that have been indicated.

Claims (25)

1. Shadow mask frame of a cathode ray tube, particularly a colour television tube, the frame having flat sides (30a, 30b, 30c, 30d, 51) disposed along the side faces of a straight prismatic surface and having a stiffening edge (20, 48a, 48b) for fixing a shadow mask (5) on the frame (7, 30) by means of which the shadow mask (5) is positioned within a glass casing of the cathode ray tube which comprises a cone (2) and a faceplate (3) comprising a screen (3a), characterised in that the sides (30a, 30b, 30c, 30d, 51) of the frame (30) comprise an outer membrane (11, 21, 21', 31, 41, 51a) and an inner membrane (12, 22, 22', 32, 42, 51b) added on and fixed against one another and each consisting of a section of thin metal strip.
2. Frame according to claim 1, characterised in that at least one of the outer (11, 21, 21', 31, 41, 51a) and inner membranes (12, 22, 22', 32, 42, 51b) is reinforced by at least one dished part of the membrane.
3. Frame according to claim 2, characterised in that at least one membrane is reinforced,by ribs (13, 14).
4. Frame according to claim 3, characterised in that the outer membrane (11, 21, 21', 31, 41, 51a) and the inner membrane (12, 22, 22', 32, 42, 51b) are reinforced by ribs. and the ribs (13) of the outer membrane (1, 21, 21', 31, 41) are in a direction perpendicular to the direction of the ribs (14) of the inner membrane (12, 22, 22', 32, 42).
5. Frame according to claim 3, characterised in that at least one membrane comprises ribs arranged in two directions perpendicular to each other.
6. Frame according to any one of claims 2, 3 and 4, characterised in that the inner membrane (11, 21, 21', 31, 41) and the outer membrane (12, 22, 22', 32, 42) are drilled with at least one hole (17, 18, 55) level with each of the dished parts or reinforcing ribs (13, 14).
7. Frame according to any one of claims 1 to 6, characterised in that the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) are fixed to one another by weld points (27).
8. Frame according to any one of claims 1 to 6, characterised in that the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) are fixed to one another by continuous weld lines (28).
9. Frame according to any one of claims 1 to 6, characterised in that the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) are connected to one another by a brazing material distributed in zones (29) between the membranes.
10. Frame according to any one of claims 1 to 9, characterised in that the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) are made of the same metallic material.
11. Frame according to claim 10, characterised in that the metallic material is one of the following materials: low-carbon steel, iron-based alloy, iron-nickel alloy, iron-chrome alloy,. nickel-based alloy, structurally hardened alloy, martensitically hardened alloy, magnetic alloy, non-magnetic alloy, vibration-damping alloy.
12. Frame according to any one of claims 1 to 9, characterised in that the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) are made of different materials.
13. Frame according to claim 12, characterised in that at least one of the materials constituting the outer membrane (11, 21, 21', 31, 41) and the inner membrane (12, 22, 22', 32, 42) is selected from the among the following materials: low-carbon steel, iron-based alloy, iron-nickel alloy, iron-chrome alloy, nickel-based alloy, structurally hardened alloy, martensitically hardened alloy, magnetic alloy, non-magnetic alloy, vibration-damping alloy.
14. Frame according to any one of claims 1 to 13, characterised in that it comprises substantially planar angle zones (33) between the successive sides (30a, 30b, 30c, 30d) of the frame.
15. Frame according to claim 14, characterised in that a device (34) for suspending the frame (30) in the glass casing of the cathode ray tube is fixed by clipping it into at least one hole in each of the angle zones (33).
16. Frame according to any one of claims 1 to 15, characterised in that it comprises an edge opposite the stiffening edge (20, 48a, 48b) along which is fixed the shadow mask (5) consisting of part of at least one of the outer and inner membranes (31, 32) of the sides (30a, 30b, 30c, 30d) of the frame (30) folded at 90° towards the inside of the frame and comprising reinforcing ribs, to ensure that a magnetic shield (9) for the cathode ray tube is fixed by clipping into place.
17. Frame according to any one of claims 1 to 16, characterised in that it comprises two opposite parallel sides (47a, 47b) each having an assembly edge (48a, 48b) for the shadow mask consisting of a part of at least one membrane of the two sides (47a, 47b) of the frame (46) bent towards the inside of the frame, so that the edges (48a, 48b) for mounting the shadow mask are located on the same cylindrical surface.
18. Frame according to any one of claims 1 to 17, characterised in that the sides (30a, 30b, 30c, 30d) of the frame (30) are disposed along the side faces of a rectangular parallelepiped.
19. Process for manufacturing a shadow mask frame for a cathode ray tube such as a colour television tube, the frame having flat sides disposed substantially along the side faces of a straight prismatic surface, characterised in that at least a first membrane (11, 21, 31, 41) and at least a second membrane. (12, 22, 32, 42) are cut out from at least one thin metal strip, said membranes comprising, along the length of the metal strip, at least one zone (11a, 11b, 11c, 11d, 12a, 12b, 12c, 12d, 21a, 21b, 22a, 22b, 41a, 42a) in the shape of a flat side of the frame which is to be produced, so as to obtain, for each side of the frame which is to be produced, a first membrane and a second membrane which can be superimposed,

    in each of the zones of the first and second membranes, dished parts or reinforcing ribs (13, 14) are provided by deforming the corresponding metal strip, and

    the frame is assembled by welding the membranes in arrangements where they are abutting on one another.
20. Process according to claim 19, characterised in that the first and second membranes (11, 21, 31, 41, 12, 22, 32, 42) further comprise at least one angle zone or connecting zone (11e, 11f, 11g, 11h, 12e, 12f, 12g, 12h) adjacent to a zone in the form of a flat side of the frame.
21. Process according to either of claims 19 and 20, characterised in that the folding and positioning of the first and second membranes against one another is carried out in accordance with the shape of the frame which is to be produced, and

    the first and second membranes are welded so as to abut on one another and are held in the shape of the frame which is to be produced.
22. Process according to either of claims 19 and 20, characterised in that the first and second membranes are superimposed so that the zones (41a, 42a) corresponding to the same side of the frame are superimposed,

    the membranes are joined together in their superimposed position, and

    the superimposed membranes joined together are folded and assembled to obtain the frame.
23. Process according to claim 22, characterised in that the membranes are joined together in the superimposed position by spreading a layer of braze on one side of the first membrane, superimposing the second membrane on the side or the first membrane on which the brazing product is deposited and finally bringing the superimposed membranes to a brazing temperature.
24. Process according to any one of claims 19 to 23, to produce a frame wherein the flat sides (30a, 30b, 30c, 30d) are arranged along the side faces of a rectangular parallelepiped, characterised in that the first membrane (11) and the second membrane (12) have four zones (11a, 11b, 11c, 11d, 12a, 12b, 12c, 12d) along their length, in the shape of the four sides of the frame in the form of a rectangular parallelepiped, three angle zones (12e, 12d, 12g) each intercalated between two zones, corresponding to two sides of the frame and a zone for connecting to one of the ends of the membrane (11, 12).
25. Process according to any one of claims 19 to 23 for the manufacture of a frame wherein the flat sides are arranged along the side faces of a rectangular parallelepiped, characterised in that two first membranes (21, 21') and two second membranes (22, 22') are cut out, each comprising a first zone corresponding to a first side of the frame, a second zone corresponding to a second side of the frame, and an angle zone between the first and second zone and a zone for connection to one of the ends of the membrane.

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