EP1320427B1 - Method and installation for making a workpiece comprising at least a tubular section - Google Patents

Abstract

A method of forming a tubular workpiece which consists in pre-bending a metal plate along at least two longitudinal lines of bend ( 12-13 ) then in bending the plate along at least one of the lines of bend ( 12-13 ) using a bending member ( 103-104 ) that exerts an external clamping force (F<SUB>7</SUB>, F<SUB>8</SUB>) along a part ( 23, 24 ) of the plate towards the at least one of the lines of bend ( 12, 13 ). Thereby preventing any sliding of part ( 23, 24 ) of the plate along the bending member ( 103-104 ) as the bending member bends the part. The bending member is articulated about a virtual geometrical axis (a, c) located inside a tubular section of the workpiece.

Description

The invention relates to a method and an installation. for manufacturing a part comprising at least one part tubular obtained by folding a sheet according to the preambles of claims 1 and 16. This process and this installation are, in particular, suitable for the manufacture of a shadow mask support frame for a cathode ray tube viewing.

Such a framework is used, for example, in the field of the manufacture of color televisions. Cathode ray tubes color visualization include a sheet metallic, pierced with a multitude of holes or slots, called "shadow mask" or "shadow mask" and arranged between the electron gun and the display screen. Such shadow mask is supported by a frame, usually of rectangular shape, which keeps it in position in the vicinity of the display screen and, if necessary, ensures that the mask is stretched in order to limit the resulting deformations local overheating generated by the electron beams.

It is known from EP-A-0 809 272 to produce a frame for shadow mask from two thin metal strips attached to each other and having ribs of stiffening. Such a frame is light and rigid, which allows to use it for a stretched shadow mask as well as for a deep shadow mask. By request FR-A-2 790 140, we know a shadow mask frame with parts tubular formed by folding a sheet. Folding the sheet can be carried out by different methods, in particular at by hand, manual folding, however, is not compatible with industrial production at a high rate. Through elsewhere, the known methods of folding using machines with an apron, sometimes called a "counterblade", on which is maintained a sheet to be folded using a blank holder, and an articulated folding flap, do not allow to manufacture easily tubular parts.

An object of the present invention is to provide a folding process using a folding machine allowing to manufacture parts comprising at least part tubular, in particular a part constituting one or more amounts of a shadow mask support frame.

In this spirit, the invention relates to a method of manufacture of a part comprising at least one section tubular obtained by folding a metal plate according to au minus a longitudinal edge, characterized in that it includes steps consisting in pre-folding the plate according to minus two folding edges then to exercise, during folding, a clamping force of at least part of the plate by compared to a folding member.

Thanks to the invention, the metal plate is effectively moved by the folding member, without risk of slipping may result in imprecise bending at the ridge. Thanks to pre-folding, the plate is kept in position on the apron or box spring on which it rests, without risk of buckling during subsequent folding. The effort of clamping or retaining the plate relative to the edge of folding keeps the plate in position relative to its environment without having to use pliers fasteners that could hardly be used inside tubular parts because they would interfere with folding operations.

• le pré-pliage est effectué en immobilisant la plaque sur un tablier au moyen d'un serre-flan rétractable. On peut en outre prévoir une étape de préparation du pré-pliage par affaiblissement de la tôle le long des arêtes de pliage. Cet affaiblissement peut être effectué par marquage ou poinçonnage sur une partie de l'épaisseur de la tôle, ou par tout autre procédé adapté
• on plie la plaque selon des arêtes différentes sur la longueur de la pièce à fabriquer, de telle sorte qu'il est formé des sections tubulaires de profils de base différents. Ceci permet de réaliser des pièces de géométrie élaborée, telles que des cadres support de masque d'ombre.
• on plie la plaque autour d'au moins un axe géométrique virtuel défini par la coopération de l'organe de pliage et de moyens de guidage associés.
• on exerce l'effort de bridage essentiellement par l'extérieur d'une section tubulaire de la pièce, en l'absence d'un effort de serrage exercé par un serre-flanc ou un matériel analogue. Ceci tient compte du fait que l'utilisation d'un serre-flanc est délicate avec une pièce tubulaire, voire impossible si elle présente des sections de profils de base différents.
• l'effort de bridage est dirigé globalement en direction de l'arête de pliage.
• l'effort de bridage est globalement perpendiculaire à l'arête de pliage.
• l'effort de bridage contraint une partie de la plaque métallique parallèlement à elle-même et perpendiculairement à l'effort de pliage exercé sur cette partie par l'organe de pliage.
• l'effort de bridage est adapté en fonction de la position de l'organe de pliage. Cet aspect de l'invention permet de tenir compte des variations dimensionnelles de la plaque au cours de l'opération de pliage, ces variations résultant notamment des contraintes localisées au niveau de l'arête et de son rayon de courbure. Il permet également d'éviter une interférence entre les éléments permettant d'exercer un effort de bridage au niveau de deux bords opposés de la plaque.
• le procédé comprend en outre une étape consistant, à amener une première partie de la plaque en recouvrement d'une seconde partie de celle-ci et à diminuer l'effort de bridage exercé sur la seconde partie avant soudage de ces parties ensemble. Cet aspect de l'invention assure que les parties en recouvrement sont en contact élastique lors du soudage, ce qui permet à ce soudage d'être efficace et durable.
• le procédé comprend également une étape consistant à plier la plaque autour d'au moins un axe virtuel défini comme l'axe géométrique d'un berceau cylindrique de guidage de l'organe de pliage. L'utilisation d'un axe virtuel permet de manoeuvrer l'organe de pliage sans avoir recours à une charnière susceptible d'interférer avec d'autres parties de l'installation dédiées à un pliage selon une autre arête. On peut, en particulier, prévoir de plier la plaque autour d'axes de pliage différents selon la longueur de la pièce en utilisant des organes de pliage guidés par des berceaux d'axes géométriques différents correspondant à ces axes de pliage.
• le procédé comprend une étape consistant, après formation de plusieurs sections tubulaires, à les conformer en un cadre fermé par pliage de sections de liaison, entre deux sections tubulaires adjacentes, perpendiculairement aux directions principales de ces sections tubulaires.
• le procédé comprend une étape consistant à plaquer, par aspiration ou attraction magnétique, une partie de la plaque de tôle contre une partie de l'organe de pliage.

According to advantageous but not compulsory aspects of the invention, the method incorporates one or more of the following characteristics:

• pre-folding is carried out by immobilizing the plate on an apron by means of a retractable blank holder. It is also possible to provide a step for preparing the pre-folding by weakening the sheet along the folding edges. This weakening can be carried out by marking or punching over part of the thickness of the sheet, or by any other suitable method.
• the plate is folded according to different edges along the length of the workpiece, so that it is formed of tubular sections of different base profiles. This makes it possible to produce parts of elaborate geometry, such as shadow mask support frames.
• the plate is folded around at least one virtual geometric axis defined by the cooperation of the folding member and associated guide means.
• the clamping force is exerted essentially from the outside of a tubular section of the part, in the absence of a clamping force exerted by a clamp or the like. This takes into account the fact that the use of a clamp is difficult with a tubular piece, or even impossible if it has sections of different basic profiles.
• the clamping force is directed generally in the direction of the folding edge.
• the clamping force is generally perpendicular to the folding edge.
• the clamping force constrains a part of the metal plate parallel to itself and perpendicular to the folding force exerted on this part by the folding member.
• the clamping force is adapted as a function of the position of the folding member. This aspect of the invention makes it possible to take account of the dimensional variations of the plate during the folding operation, these variations resulting in particular from the localized stresses at the level of the edge and its radius of curvature. It also avoids interference between the elements making it possible to exert a clamping force at two opposite edges of the plate.
• the method further comprises a step consisting in bringing a first part of the plate into overlap with a second part thereof and in reducing the clamping force exerted on the second part before welding these parts together. This aspect of the invention ensures that the overlapping parts are in elastic contact during welding, which allows this welding to be effective and durable.
• the method also comprises a step consisting in folding the plate around at least one virtual axis defined as the geometric axis of a cylindrical cradle for guiding the folding member. The use of a virtual axis makes it possible to maneuver the folding member without having recourse to a hinge capable of interfering with other parts of the installation dedicated to folding along another edge. One can, in particular, provide to fold the plate around different folding axes according to the length of the part using folding members guided by cradles of different geometric axes corresponding to these folding axes.
• the method comprises a step consisting, after the formation of several tubular sections, in forming them into a closed frame by folding connecting sections, between two adjacent tubular sections, perpendicular to the main directions of these tubular sections.
• the method comprises a step consisting in pressing, by suction or magnetic attraction, a part of the sheet metal plate against a part of the folding member.

The invention also relates to an installation allowing to implement the method described above and, more specifically an installation comprising at least one member for folding a metal plate along an edge longitudinal of a tubular section of the frame, characterized in that this folding member is equipped with means allowing to exert a clamping force on part of the plate opposing a sliding of part of the plate along of the folding member, while this folding member is articulated around a virtual geometric axis located inside of the corresponding tubular section.

• plusieurs organes de pliage sont aptes à plier la plaque selon des arêtes distinctes, de telle sorte qu'il est formé des sections tubulaires de profils de base différents.
• les moyens de bridage sont constitués par au moins un talon formant une butée d'appui de la plaque. Ce talon peut s'étendre sur sensiblement toute la longueur de l'arête. On peut également prévoir plusieurs talons répartis sur la longueur de l'arête de pliage et séparés par des espaces de réception de talons de retenue utilisés pour le pliage de la plaque selon une autre arête.
• les moyens de bridage ont une position variable par rapport à l'arête de pliage. Ceci peut provenir du fait que l'installation comprend des moyens de réglage ou d'adaptation de l'effort exercé par les moyens de bridage sur la plaque.
• l'organe de pliage comprend au moins une surface d'appui contre la plaque et au moins une surface cylindrique à base circulaire apte à coopérer avec une surface cylindrique à base circulaire d'un berceau, ces surfaces cylindriques étant centrées sur un axe virtuel de pliage de la plaque. L'utilisation d'un tel berceau permet de guider l'organe de pliage sans avoir recours à une charnière susceptible d'interférer avec des dispositifs voisins. Dans ce cas, on peut prévoir que l'installation comprend plusieurs organes de pliage répartis sur la longueur de la plaque et coopérant avec des berceaux dont les surfaces cylindriques ont des axes géométriques parallèles et décalés les uns par rapport aux autres. Ceci permet de plier la plaque suivant des arêtes longitudinales distinctes, sur sa longueur, ce qui permet de conformer des sections tubulaires de géométries différentes correspondant, par exemple, à des côtés distincts d'un cadre à réaliser. Le ou les organes de pliage sont avantageusement équipés d'une nervure externe formant une surface cylindrique apte à coopérer avec la surface cylindrique du berceau correspondant, ces surfaces cylindriques étant sensiblement de mêmes rayons. Selon un mode de réalisation avantageux de l'invention permettant des basculements de grande amplitude, le ou les organes de pliage sont guidés par rapport à la surface cylindrique du berceau par des segments télescopiques qui coulissent l'un dans l'autre. Les surfaces des nervures, les segments télecopiques et/ou les surfaces des berceaux peuvent être équipés de billes ou rouleaux de glissement.
• l'installation comprend un outillage de conformation de la pièce, cet outillage incluant des éléments de support de sections tubulaires de la pièce pourvus de moyens de réception et d'immobilisation de ces parties tubulaires, ces éléments étant articulés les uns par rapport aux autres. Cet outillage permet la mise en forme finale du cadre après réalisation des parties tubulaires. On peut prévoir que l'un au moins des éléments articulés est réglable en longueur, ce qui permet d'adapter l'outillage à la fabrication de cadres de dimensions différentes. On peut également prévoir que les éléments articulés sont aptes à former ensemble une figure fermée de géométrie prédéterminée correspondant à la géométrie d'un cadre formé par la pièce fabriquée. Le caractère fermé de la figure obtenue permet d'obtenir une précision géométrique accrue grâce à un positionnement univoque des différents éléments constitutifs de cet outillage. Selon un mode de réalisation avantageux de l'invention, l'un au moins des éléments articulés est équipé d'un organe, à section transversale globalement en forme de U et apte à recevoir au moins une cale de blocage d'une section tubulaire en place dans cet élément, des moyens étant prévus pour immobiliser la cale sur cet organe.
• l'un au moins des organes de pliage est équipé d'une lame formant cisaille de découpe de la plaque lors de son pliage.

According to advantageous but not compulsory aspects of the invention, the installation incorporates one or more of the following characteristics:

• several folding members are capable of folding the plate according to distinct edges, so that tubular sections of different basic profiles are formed.
• the clamping means consist of at least one heel forming a support stop for the plate. This heel can extend over substantially the entire length of the edge. It is also possible to provide several heels distributed over the length of the folding edge and separated by spaces for receiving retaining heels used for folding the plate along another edge.
• the clamping means have a variable position relative to the folding edge. This can come from the fact that the installation comprises means for adjusting or adapting the force exerted by the clamping means on the plate.
• the folding member comprises at least one bearing surface against the plate and at least one cylindrical surface with a circular base capable of cooperating with a cylindrical surface with a circular base of a cradle, these cylindrical surfaces being centered on a virtual axis of folding the plate. The use of such a cradle makes it possible to guide the folding member without resorting to a hinge capable of interfering with neighboring devices. In this case, provision can be made for the installation to comprise several folding members distributed over the length of the plate and cooperating with cradles whose cylindrical surfaces have parallel geometric axes and offset with respect to each other. This makes it possible to fold the plate along distinct longitudinal edges, along its length, which makes it possible to conform tubular sections of different geometries corresponding, for example, to distinct sides of a frame to be produced. The folding member (s) are advantageously equipped with an external rib forming a cylindrical surface capable of cooperating with the cylindrical surface of the corresponding cradle, these cylindrical surfaces being of substantially the same radius. According to an advantageous embodiment of the invention allowing tilting of large amplitude, the folding member or members are guided relative to the cylindrical surface of the cradle by telescopic segments which slide one inside the other. The surfaces of the ribs, the telescopic segments and / or the surfaces of the cradles can be fitted with sliding balls or rollers.
• the installation comprises a tool for shaping the part, this tool including elements for supporting tubular sections of the part provided with means for receiving and immobilizing these tubular parts, these elements being articulated with respect to each other. This tool allows the final shaping of the frame after completion of the tubular parts. It can be provided that at least one of the articulated elements is adjustable in length, which makes it possible to adapt the tool to the production of frames of different dimensions. It can also be provided that the articulated elements are capable of forming together a closed figure of predetermined geometry corresponding to the geometry of a frame formed by the manufactured part. The closed character of the figure obtained makes it possible to obtain increased geometrical precision thanks to an unequivocal positioning of the various constituent elements of this tool. According to an advantageous embodiment of the invention, at least one of the articulated elements is equipped with a member, with a generally U-shaped cross section and able to receive at least one blocking wedge for a tubular section in place in this element, means being provided for immobilizing the wedge on this member.
• at least one of the folding members is equipped with a blade forming a shear for cutting the plate during its folding.

The invention finally relates to the use of the process or of the installation mentioned above for manufacturing a shadow mask support frame for cathode ray tube.

• la figure 1 représente de façon schématique un cadre de masque d'ombre sur lequel est disposé un masque d'ombre partiellement représenté ;
• la figure 2 est une représentation schématique de principe en perspective d'une partie d'une installation de fabrication du cadre de la figure 1, le cadre n'étant pas représenté ;
• la figure 3 est une représentation schématique de principe d'une partie du cadre de la figure 1 lorsqu'il est en place dans l'installation de la figure 2 ;
• la figure 4 est une coupe de principe selon la ligne IV-IV à la figure 2, le cadre étant représenté en place dans l'installation ;
• la figure 5 est une coupe analogue à la figure 4 lors d'une première étape du procédé de l'invention, antérieure à la configuration de la figure 4 ;
• la figure 6 est une coupe analogue à la figure 4 lors d'une étape ultérieure du procédé de l'invention, postérieure à la configuration de la figure 4 ;
• la figure 7 est une coupe analogue à la figure 4 lors d'une seconde étape ultérieure du procédé de l'invention ;
• la figure 8 est une coupe de principe selon la ligne VIII-VIII à la figure 2, le cadre étant représenté en place dans l'installation ;
• la figure 9 est une coupe analogue à la figure 8 lors d'une étape ultérieure du procédé de l'invention ;
• la figure 10 est une coupe analogue à la figure 8 lors d'une seconde étape ultérieure du procédé de l'invention ;
• la figure 11 est une vue en perspective d'une autre partie de l'installation de l'invention, un cadre en cours de fabrication étant représenté au-dessus de cette partie de l'installation ;
• la figure 12 est une vue à plus grande échelle du détail XII à la figure 11, le cadre étant en place sur l'outillage ;
• la figure 13 est une vue analogue à la figure 12 lors d'une étape ultérieure de fabrication du cadre ;
• la figure 14 est une vue de dessus de la partie de l'installation représentée aux figures 11 à 13, en cours d'utilisation ;
• la figure 15 est une représentation schématique partielle en coupe d'une partie d'une plaque en cours de pliage ;
• la figure 16 est une représentation schématique de principe, en perspective, d'une partie de l'installation ;
• la figure 17 est une coupe schématique d'une partie d'une installation conforme à un second mode de réalisation de l'invention ;
• la figure 18 est une vue analogue à la figure 13 pour l'installation de la figure 17 et
• la figure 19 est une coupe de principe selon la ligne XIX-XIX à la figure 18.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of two embodiments of an installation for manufacturing a support frame for shadow mask and its method of implementation, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 schematically shows a shadow mask frame on which is disposed a partially shown shadow mask;
• FIG. 2 is a schematic representation in principle in perspective of a part of an installation for manufacturing the frame of FIG. 1, the frame not being shown;
• Figure 3 is a schematic representation of a part of the frame of Figure 1 when in place in the installation of Figure 2;
• Figure 4 is a principle section along the line IV-IV in Figure 2, the frame being shown in place in the installation;
• Figure 5 is a section similar to Figure 4 during a first step of the method of the invention, prior to the configuration of Figure 4;
• Figure 6 is a section similar to Figure 4 during a subsequent step of the method of the invention, after the configuration of Figure 4;
• Figure 7 is a section similar to Figure 4 during a second subsequent step of the method of the invention;
• Figure 8 is a section in principle along the line VIII-VIII in Figure 2, the frame being shown in place in the installation;
• Figure 9 is a section similar to Figure 8 during a subsequent step of the method of the invention;
• Figure 10 is a section similar to Figure 8 during a second subsequent step of the method of the invention;
• FIG. 11 is a perspective view of another part of the installation of the invention, a frame during manufacture being shown above this part of the installation;
• Figure 12 is an enlarged view of detail XII in Figure 11, the frame being in place on the tooling;
• Figure 13 is a view similar to Figure 12 during a subsequent step of manufacturing the frame;
• Figure 14 is a top view of the part of the installation shown in Figures 11 to 13, in use;
• Figure 15 is a partial schematic representation in section of a portion of a plate being folded;
• Figure 16 is a schematic representation in principle, in perspective, of part of the installation;
• Figure 17 is a schematic sectional view of part of an installation according to a second embodiment of the invention;
• Figure 18 is a view similar to Figure 13 for the installation of Figure 17 and
• FIG. 19 is a principle section along the line XIX-XIX in FIG. 18.

In Figure 1, there is shown schematically a shadow mask 1 mounted on a frame 2 mask support shade. Frame 2 has a generally rectangular shape and has two lateral uprights 3, 3 'and two uprights 4, 4 'ends. The shadow mask consists of a thin metal foil, e.g. iron-nickel alloy low expansion coefficient, drilled with 5 holes and fixed by welding on upper edges 6, 6 'of the uprights end 4, 4 '. Different forms of shadow mask are possible depending on the cathode ray tube to which it must be associated. In the example shown, the shadow mask is generally planar, but it can also be bent in portion of cylinder. The mask 1 can also be stretched, i.e. subject to tension parallel to the uprights side 3, 3 'of frame 2.

The uprights 3, 3 ', 4 and 4' are formed by folding a sheet metal so as to each constitute a tubular element. These four uprights can be obtained by folding a single metal plate. It is also possible to plan to use a folded plate for each upright or a plate for two contiguous amounts.

In the example illustrated in the figures, a single metal plate 10 is used for the realization of four tubular uprights 3, 3 ', 4 and 4'. This plate appears partially in Figure 3 after steps of cutting of assembly tabs 11 and of pre-marking longitudinal edges 12 to 17.

At the edges 12 to 14, the plate 10 forms the end upright 4. At the edges 12 and 15 to 17, the plate 10 forms the lateral upright 3. In practice, the part of the plate 10 shown in Figure 3 corresponds to the corner 7 of frame 2 at the level of which the junction between amounts 3 and 4.

The plate 10 is shaped in the configuration of FIG. 3 by cutting, stamping and folding operations using, in particular, punches intended to create in the plate 10 an edge 12 extending over substantially its entire length while the edges 13 to 17 extend over only part of the plate 10, the edges 13 and 15 being parallel to each other but offset, that is to say distant from the edge 12 by distances d ₁ and d ₂ different.

As can be seen more particularly from FIG. 5, the pre-folding of the plate 10 is carried out by immobilizing this plate on an apron or counter blade 101 thanks to a blank holder 107 and by folding the plate 10 as shown by the arrows F, which has the effect of creating the lines of folding 12 and 13. Another blank holder is used at the amount 3, which allows to continue the creation of the line of fold 12 and create the fold line 15. This second hold-down is also configured to allow creation fold lines 16 and 17.

These pre-folding operations achieve the configuration of Figure 4 in which the blank holder 107 is retracted or removed from the interior of the plate 10 as represented by the arrow F '. We note that the shape of the hold-down 107 is compatible with its removal from the inside of plate 10 in the configuration of FIG. 4.

Thanks to this pre-folding operation, the plate 10 is immobilized in relation to the installation of the invention because it is in abutment along the two folding edges 12 and 13 or 12 and 15 which are generally parallel.

Pre-folding can be prepared by marking the fold lines, for example by punching on a part of the thickness of the plate 10, in particular 25%.

Generally, the pre-folding of the plate 10 can be performed on the machine shown in the figures or on another machine, without going beyond the scope of this invention.

In the case where a section amount of more is achieved on three sides, like the upright 3, preliminary pre-folding are necessary to make the edges of the type of edges 16 and 17. Such preliminary pre-folding is also used in the case of the amount 4 for the realization of the edge 14.

The installation of the invention 100 includes the apron 101 on which a central part 21 of the plate 10 is placed. Pawns, only one of which is visible in the figures with the reference 102, extend from this plate 101 and are intended to pass through openings 22 provided in the part 21, so as to position the plate 10 on the base plate 101.

From part 21 extend two wings 23 and 24 of the plate 10 intended to form the upright 4. From this same central part 21 extend two other wings 25 and 26 intended to form the amount 3.

The wings 23 and 25 are connected to the part 21 along the edge 12. The wings 24 and 26 are respectively connected to the part 21 along the edges 13 and 15. The wing 23 is connected to an edge 27 by the fold line or edge 14 while the wings 25 and 26 are both divided into two panels 25 a , 25 b respectively 26 a , 26 b by the fold lines or edges 16 and 17.

The installation 100 comprises a folding jaw 103 intended to fold the wing 23 in the direction of the part 21 by means of a force represented by the arrow F ₁ . The jaw 103 comprises a plate 103 a whose length, parallel to a longitudinal axis XX ′ of the installation 100, is adapted to the length of the wing 23. The face 103 a 1 of the plate 103 a is intended to be in contact with wing 23 is generally flat. The plate 103 a is equipped, on its face 103 a 2 opposite the face 103 a 1, with two ribs 103 b , extending opposite the wing 23 in directions generally perpendicular to the axis X- X '. These ribs 103 b each form a convex surface 103 c in a portion of a cylinder with a circular base centered on a virtual axis a. By "virtual" is meant the fact that the axis a is not defined by a hinge, but as being the geometrical location joining the centers of curvature of the surfaces 103 c . This axis is located inside the upright 4 and is parallel to the axis XX '.

The installation 100 also includes a cradle 113 defining an internal surface 113 c that is cylindrical and with a circular base against which the ribs 103 b slide by their surfaces 103 c . The axis of symmetry of the surface 113 a is also the axis a. The radii of curvature R ₁₀₃ and R ₁₁₃ of the surfaces 103 c and 113 c are equal. It is thus possible to rotate the jaw 103 in the cradle 113 around the axis a , as shown by the arrow F ₂ in Figure 4, by relative sliding of the surfaces 103 c and 113 c .

A second jaw 104 comprises a plate 104 a intended to come to bear, by a face 104 a 1, against the wing 24 and to exert on it a force F ₃ allowing it to be folded down in the direction of the base plate 101 and of the central part 21. The plate 104 a is provided, on its face 104 a 2 opposite the face 104 a 1, of ribs 104 b of which an external or convex surface 104 c is cylindrical with a circular base and capable of coming into bearing against an internal cylindrical or concave surface with a circular base 114 c of a cradle 114. We denote by c the common central geometric axis of the surfaces 104 c , this axis being parallel to the axis XX 'and located in the interior volume of the amount 4. We denote 114 c and R ₁₀₄ and R ₁₁₄ the respective radii of the surfaces 104 c and 114 c, these radii being of the same length. The jaw 104 can pivot around the axis c while being guided by the cradle 114, as shown by the arrow F ′ ₂ .

With particular reference to FIGS. 4, 6 and 7, it is understood that it is possible to conform the plate 10 into a tubular section with a generally triangular base thanks to the forces F ₁ and F ₃ .

However, from the position of FIG. 4, if the forces F ₁ and F ₃ are exerted while the wings 23 and 24 rest respectively against the plates 103 a and 104 a without any other force, the plate 10 risks being lifted in the direction of the arrow F ₄ in FIG. 4 because the wings 23 and 24 risk sliding along the surfaces 103 a 1 and 104 a 1, as represented by the arrows F ₅ and F _{6 respectively} . This could result in imprecise bending at the edges 12 and 13, the center of curvature of which would then no longer coincide with the geometric axes a and c .

To avoid relative movements between the wings 23 and 24 and the surfaces 103 a and 104 a , the jaws 103 and 104 are each fitted with a heel 103 f , 104 f capable of exerting an effort on the wings 23 and 24, respectively noted F ₇ and F ₈ ; directed generally towards the edges 12 and 13, that is to say opposing a sliding of the wings 23 and 24 in the direction of the arrows F ₅ and F ₆ . The forces F ₇ and F ₈ therefore constitute efforts for clamping or retaining the wings 23 and 24 relative to the jaws 103 and 104. In particular, the wings 23 and 24 are not likely to project radially outside the jaws 103 and 104.

In other words, the heels 103 f and 104 f form stops for the displacement of the wings 23 and 24 in the direction of the arrows F ₅ and F ₆ .

It is noted that the forces F ₇ and F ₈ are exerted from the outside of the upright 4. Thus, the plate 10 is held on the deck 101 without the use of an insert, such as a sidewall clamp, which is favorable because a sidewall would be difficult to set up and remove once the plate folded. In addition, a sidewall could not extend to the level of the upright 3.

The invention therefore allows folding of the plate 10 in one tubular structure without the introduction of a jamming inside its different sections.

The heel 103 f is in one piece with the plate 103 a , this heel being intended to cover the edge 27 of the wing 23. This heel 103 f extends over the entire length of the jaw 103 parallel to the axis XX ' , which guarantees that the upper edge of the upright 4, on which the mask 1 is intended to be stretched, is free from irregularities. For this purpose, the bead 103f has a smooth surface on the side of the edge 27 because the heel 103 f used for forming the edge which should be as regular as possible for the mask 1, which is stretched over the upper edge of upright 4, does not have a wave or relief capable of disturbing the image generated in the cathode ray tube.

The heel 104 f , which extends over the entire length of the jaw 104, is capable of moving perpendicular to the plate 104 a and to the wing 24, as shown by the arrow F ₉ in FIG. 4.

The operation is as follows:

When the plate 10 has been positioned on the deck 101 and pre-folded using the blank holder 107, the jaw 104 is moved by an electric or hydraulic pneumatic jack, so that it folds down, thanks to the force F ₃ exerted by the plate 104 a , the plate 24 in the direction of the part 21. The heel 104 f exerts on the wing 24 a force F ₈ directed towards the edge 12, which guarantees a good positioning of the wing 24 by relative to the jaw 104. We then reach the position of Figure 6 where the angle α between the wing 24 and the part 21 is less than 90 °. From this position, the jaw 103 is actuated so that it flaps the wing 23 in the direction of the part 21 by exerting the force F ₁ , as shown in FIG. 7. The jaws 103 and 104 are guided in their displacements F ₂ and F ' ₂ thanks to the cooperation of the convex cylindrical surfaces 103 c , 104 c and concave 113 c , 114 c .

To avoid interference between the heels 103 f and 104 f , the heel 104 f is distant from the wing 24, as shown by the arrow F ′ ₉ in FIG. 7. In fact, it is possible to remove the force F ₈ in the configuration of FIG. 6 because no movement of the wing 24 is necessary between the configurations of FIGS. 6 and 7. In addition, the fact that the angle α is less than 90 ° ensures effective positioning of the 'wing 24, including in the case of removal of the force F ₈ .

In other words, in the configurations of Figures 6 and 7, the force F ₈ is not essential because the plate 104 effectively maintains the flange 24 in position relative to the c axis.

According to an alternative embodiment of the invention, it can be provided that several heels 104 f are distributed over the length of the plate 104 a , parallel to the axes XX 'and c .

Referring now to Figure 15 which is an enlargement of detail XV in Figure 4. The plate 10 has a thickness e not zero. The transition from the position shown in solid lines to the position shown in dashed lines, which corresponds substantially to that of FIG. 7, has the effect of reducing the height h of the wing 23 in the configuration in dashed lines relative to the length l of this wing in the configuration in solid lines because the neutral fiber f of the plate 10 forms an arc of circle centered on the axis a in the configuration shown in broken lines. If we consider that the axis a is located inside the area intended to form the edge 12 with a distance d from the neutral fiber f and taking the example of a plate bent from from a flat configuration to arrive at a configuration folded at 90 °, the difference between the height h and the length l is 1/2 πd. In the present case, it is less insofar as the edge 12 is already pre-marked in the configuration of FIG. 4. It is however not zero.

In view of this difference in values between the height h and the length l , the value of the force F ₇ should be adapted so that it effectively immobilizes the plate 10 in the region of the edge 12 throughout the rotational movement of the jaw 103 around the axis a. To do this, provision is made for the heel 103 f to be loaded elastically in the direction of the axis a or the edge 12. In this case, the heel 103 f is not in one piece with the plate 103 a . According to another approach, it is possible to provide that a system of cams makes it possible to vary the intensity of the force F ₇ as a function of the angular orientation of the jaw 103 around the axis a, during the pivoting F ₂ .

According to another approach, it is possible to compensate for this difference in value between the height h and the length l by shifting the pivot axis a in a direction perpendicular to the main plane of the deck 101. In this case, the heel 103 f can be in one piece with plate 103 has jaw 103.

Of course, the heel 104 f can also be provided with means making it possible to vary the intensity of the force F ₈ as a function of the jaw position 104 around the axis c during the pivoting F ′ ₂ . As a variant, the position of the axis c can also be provided for variable to compensate for the variations in length and / or height of the wing 24.

Referring more particularly to Figures 8 to 10, it is noted that the lateral upright 3 is of quadrangular section. A jaw 105 is provided to cooperate with the wing 25 and comprises a base plate 105 a , one face 105 a 1 in contact with the wing 25 allows exerting a force F ₁₁ to fold the wing 25 towards the elements 21 and 101. Like the jaw 103, the jaw 105 is equipped with ribs 105 b defining convex cylindrical surfaces 105 c centered on the axis a and making it possible to cooperate with a cradle 115 defining a concave surface 115 c for sliding the surfaces 105 c , the surface 115 c being, like the surfaces 105 c , with a circular base and centered on the axis a. The jaw 105 is equipped with several heels 105 f distributed over its length parallel to the axis XX ′, these heels being designed to come into contact with the wing 25 at the edge 17 by constituting a stop at a possible sliding of the wing 25. The heels 105 f exert on the wing 25 a clamping force F ₁₂ directed towards the edge 12 and parallel to the panel 25 a . The force F ₁₂ has the same function as the forces F ₇ and F ₈ previously mentioned. It makes it possible to effectively position the wing 25 relative to the axis a throughout the folding operation carried out thanks to the force F ₁₁ .

In the same way, a jaw 106 is provided to cooperate with the wing 26 and comprises a plate 106a forming a face 106 a 1 bearing against the wing 26 and equipped with ribs 106 b whose convex external radial surfaces 106 c cooperate with a concave surface 116 c of a cradle 116. The surfaces 106 c and 116 c are centered on a geometric axis or virtual axis b constituting the center of the edge 15 and located, like the axis a, in the volume inside the upright 3.

The jaw 106 is equipped with heels 106 f making it possible to retain the wing 26 in position relative to the plate 106 a during the folding of the edge 15. The plate 106 a is not flat but forms a concave zone of receiving the panels 26 a and 26 b , the plate 106 a being itself formed by two panels oriented relative to each other with an angle β corresponding to the angle of orientation of the panels 26 a and 26 b relative to each other. The heels 106 f are arranged to bear against the free edge 26 c of the panel 26 b .

The heels 106 f are distributed over the length of the plate 106 a .

The heels 105 f on the one hand and 106 f on the other hand are staggered relative to each other by being offset along the axis XX ', a heel 105 f being opposite an interval free 106 g defined between two heels 106 f , while a heel 106 f is placed opposite a free interval 105 g defined between two heels 105 f .

The folding of the upright 3 can be explained with reference to Figures 8 to 10. In the configuration of Figure 8, a force is exerted on the jaw 105 by any suitable means, so that it is moved and exerts the force folding F ₁₁ of the wing 25 in the direction of the part 21, the heels 105 f overlapping the junction zone 25 c , defined between the panels 25 a and 25 b and which includes the edge 17. The force F ₁₁ allows the wing 25 to be folded down into the position of FIG. 9 where the panel 25 a is generally perpendicular to the part 21, the panel 25 b being generally parallel to this part. During the folding operation carried out between the configurations of FIGS. 8 and 9, the force F ₁₂ effectively retains the wing 25 in position relative to the jaw 105 and to the edge 12.

The jaw 106 is then activated, to pass from the position of FIG. 9 to that of FIG. 10, a force F ₁₃ in bending the wing 26 in the direction of the part 21 being exerted by the plate 106 a while a force F ₁₄ is exerted by the heels 106 f on the wing 26 parallel to this wing and generally in the direction of the edge 15.

As before, the forces F ₁₂ and F ₁₄ can be modulated as a function of the orientation of the jaws 105 and 106 around the axes a and b. As a variant, the axes a and b can be offset from their representation in FIGS. 8 to 10 in order to compensate for the variations in length of the wings 25 and 26.

In addition, in the configuration of FIG. 10, the force F ₁₂ can be relaxed or reduced by a movement of the heel 105 f in a direction away from the edge 12, so that, due to the elasticity of the plate 10, the panel 25 b comes into firm elastic abutment against the face of the panel 26 b oriented towards the part 21. It is then possible to weld the panels 25 b and 26 b point by point using a beam high energy directed between two heels 105 f and 106 f adjacent.

To achieve the elastic support of the panels 25 d and 26 d , it is also possible to provide that the folding angle between the panels 25 a and 25 b is slightly more open than that obtained in the configuration of FIG. 10, so that an elastic support is obtained in this configuration without it being necessary to release the force F ₁₂ .

As shown more clearly in Figures 11 to 14, the frame 2 is shaped, after shaping the different uprights 3, 3 ', 4 and 4', by folding. When the amounts tubes have been produced, the plate 10 extends overall in the direction X-X 'in four sections connected by 8, 8 'and 8' 'junction zones. A tool 200 is provided for the shaping of frame 2 and includes four parts 201, 202, 203 and 204 each intended to receive one of the amounts 3, 3 ', 4 or 4'.

These flaps 201 to 204 are each formed of two mass pieces 201 a , 201 b , 202 a , 202 b , 203 a , 203 b , 204 a , 204 b connected by a screw-nut system 201 c , 202 c , 203 c or 204 c for adjusting the length of the flaps 201 to 204. Guide rods 201 c ', 202 c ', 203 c 'and 204 c ' are associated with systems 201 c to 204 c . The length of each flap 201 to 204 is adjusted, parallel to its largest dimension X ₁ to X ₄ , to the length of the amount that it must receive. The flaps 201 to 204 are provided adjustable in length to allow the manufacture of frames 2 of different sizes.

The parts 201 a and 201 b are respectively provided with angles 201 d , 201 e for receiving the amount 4. Jaws 201 f , 201 g are provided for immobilizing the amount 4 against the angles 201 d and 201 e . Likewise, the flaps 202, 203 and 204 are respectively equipped with angles 202 d to 204 e and jaws 202 f to 204 g . As appears more particularly from FIGS. 11 and 12, the jaws are shaped as a function of the geometry of the wings 24 and 26.

The flaps 201 and 202 are articulated together around an axis Y ₁ essentially perpendicular to the main direction XX 'of the uprights 3, 4, 3' and 4 '. The axis Y ₁ is also perpendicular to the direction X ₁ in which the flap 201 is adjustable in length. Similarly, the flaps 202 and 203 are articulated together around an axis Y ₂ while the flaps 203 and 204 are articulated together around an axis Y ₃ , these axes Y ₂ and Y ₃ being generally perpendicular to the 'axis XX' and to the directions X ₁ , X ₂ , X ₃ and X ₄ for adjusting the length of the different flaps.

Three cylinders 205, 206 and 207 respectively connect the flaps 201 and 202, the flaps 202 and 203 and the flaps 203 and 204, so that they are capable of exerting on them closing forces represented by the arrows F ₁₆ , F ₁₇ and F ₁₈ in FIG. 14. These efforts make it possible to bring the tool 200 into a generally rectangular configuration in a plane perpendicular to the axes Y ₁ to Y ₃ , which makes it possible to fold the frame 2 at the level of the zones 8, 8 'and 8''and to form corners such as corner 7, as shown in FIGS. 12 and 13. In fact, the force F ₁₇ has the effect of bringing the sides of the flaps 202 and 203 together by the cylinder 206, which results in a folding of the plate 10 along a line 18 parallel to the axis Y ₂ . The tabs 11 formed on the upright 4 are thus brought into overlap with the edge 3a of the upright 3, these tongues and this edge can then be welded by a high energy beam.

In the configuration of FIG. 14, the tool 200 forms a rectangle whose flaps 201 to 204 constitute the four sides. This rectangle is closed at an area of junction between shutters 201 and 204 where means are provided not shown locking associated with means of guidance also not shown. So the rectangle shown in Figure 14 is defined precisely by the cooperation of flaps 201 to 204, so that the geometry of frame 2 thus obtained is also defined so precise.

According to an advantageous aspect of the invention shown only in FIG. 16, the jaw 106 is equipped with a blade 106h forming a shear with the plate 101 and making it possible to cut, when folding the upright 3, the plate 10 in the junction zone of the uprights 3 and 4 so as to create a notch 19 visible in FIG. 11 compatible with the folding movement around the axis Y ₂ . Due to the use of the blade 106 h , the notch is created at the end of the operations of shaping the tubular uprights 3, 3 ', 4 and 4'. Before the use of this blade, the plate 10 has continuity in the zones 8, 8 'and 8''of junction between the uprights 3 and 4. In other words the incorporation of the blade 106 h on the jaw 106 allows the notch 19 to be produced just before the use of the tooling 200, which avoids excessive stresses at the level of the line 18 during the production of the tubular parts. In practice, the blade 106 h can have a double cutting edge, so that it allows the plate 10 to be cut along two parallel lines 28 and 29 defining between them the notch 19 until a bore 30 previously formed in the plate 10. Of course, the jaws 103, 104 and 105 can also be fitted with blades forming shears.

Depending on the geometry of frame 2, that is to say in function, in particular, of the length of the uprights and their section, different sets of jaws 103 to 106 and cradles 113 to 116 can be used, the jaws and the cradles being jointly set up in installation 100, which allows rapid standard exchange of the assembly folding members of this installation.

The use of jaws 103 to 106 which can slide on cradles 113 to 116 of different geometric axes, such as axes a and c , makes it possible to produce non-aligned edges, such as edges 13 and 15, which would not be possible. with conformation jaws articulated on common hinges.

In the figures, the jaws 103 and 105 and the cradles 113 and 115 have been shown as two separate units. It could however be the same unit forming a folding member for both uprights 3 and 4, because the folding axis a is the same for the entire edge 12 over the length of the plate 10. C 'is why, the plates 103 a and 105 a on the one hand and the cradles 103 d and 105 d could be made in one piece.

When the plate to be folded is thin and in order to avoid a phenomenon of buckling of its wings under the effect of the clamping forces, provision may be made to press the sheet against the plates 103 a to 106 has jaws 103 to 106 by suction. or by magnetic attraction. To do this, the jaws 103 to 106 can be provided with channels opening on the faces 103 to 1, 103 to 2, 105 to 1 and 106 to 1 and connected to a vacuum source. The jaws can also be equipped with permanent magnets or electromagnets allowing immobilization of the wings 23 to 26.

As shown in FIG. 17 for an installation in accordance with a second embodiment of the invention, the jaws, such as the jaws 104, can be guided by cradles, such as the cradle 114 by means of telescopic circular segments 1041 and 1042 which allow, for a given geometry of a cradle 114 to obtain effective guidance for a movement F ₂₀ of pivoting of the jaw 104 around the axis c of great amplitude. The segment 1041 is integral with the jaw 104 while it is fitted inside the segment 1042, this segment 1042 itself being movable in abutment against the internal cylindrical surface 114 c of the cradle 114.

Segment 1042 is hollow while segment 1041 is full and less than the width of the volume inside segment 1042.

The segment 1042 is provided with rollers 1042g arranged along its internal surface 1042 h and able to cooperate with the section 1041 c of the segment 1041. These rollers facilitate the relative sliding between the segments 1041 and 1042. In addition, the section 1042 c of the segment 1042 is also provided with rollers 1042 i able to cooperate with the internal surface 114 c of the cradle 114. This facilitates the pivoting of the segment 1042.

According to variants not shown of the invention, the segment 1041 and / or cradle 114 can be fitted with sliding balls or rollers.

The invention has been described, with reference to the first embodiment, with jaws equipped with ribs whose end surfaces 103 c , 104 c , 105 c and 106 c are provided to slide against the cylindrical surfaces 113 c to 116 c cradles 113 to 116. However, the ribs 103 b to 106 b can be fitted with ball or roller skates, these balls or rollers being designed to roll on surfaces 113 c to 116 c .

Other methods of guiding the jaws by the cradles can be considered.

As can be seen more particularly in FIGS. 18 and 19, the angles 201 d to 204 e and the jaws 201 f to 204 g of the first embodiment can be replaced by profiles with a generally U-shaped cross section, two of which are shown in Figure 18, with the references 202 m and 203 m . These profiles have a cross section adapted to receive respectively the amounts 3 and 4 'by being fixed on flaps similar to flaps 202 and 203 of the first embodiment.

Wedges 202 p and 203 p are respectively associated with profiles 202 m and 203 m to wedge the uprights 3 and 4 'in position. These shims have a generally triangular section with a truncated angle, that is to say in fact a trapezoidal section. When the uprights 3 and 4 ′ have been placed in the profiles 202 m and 203 m , the shims are introduced into the profiles as represented by the arrows F ₂₀ , the geometry of the shims 202 p and 203 p being such that they are each provided with a surface 202 g , 203 g adapted to rest against certain wings 24 or 26 of the sections 3 and 4 '.

Each wedge 202 p or 203 p is provided with a blind hole 202 r , 203 r for receiving a plug 202 s , 203 s intended to pass through an orifice 202 t , 203 t of the profiles 202 m and 203 m . The introduction of the plug 202 s into the orifice 202 t and the blind hole 202 r is represented by the arrows F ₂₁ . Once the plugs 202 s and 203 s in place in the holes and orifices 202 r , 202 t , 203 r and 203 t , the cables are immobilized on the profiles 202 m and 203 m and hold the uprights 3 and 4 'in place .

The invention has been shown with jaws whose internal surfaces 103 a 1 to 106 a 1 are planar while the wings 23 to 26 are also planar. Of course, these surfaces and these wings can be left depending on the geometry sought for the amounts 3, 3 ', 4 and 4'.

The invention has been shown during its implementation for the production of shadow mask support frames. Of such frames can be made in one, two or four pieces, each piece forming one, two or all four uprights of the frame.

Claims (33)

1. Method for producing a casting (2) comprising at least one tubular section (3, 3', 4, 4') obtained by bending a metal plate (10) in line with at least one longitudinal edge (12-17), characterised in that it comprises steps consisting of:

   pre-bendjng (F) the said plate 10 in line with at least two bending edges (12-17), then

   exerting, during bending (F₁, F₃, F₁₁, F₁₃), a clamping force (F₇, F₈, F₁₂, F₁₄) on at least one part (23-26) of the said plate from a bending component (103-106).
2. Method according to claim 1, characterised in that the pre-bending is achieved by immobilising the said plate on an apron (101) by means of a retractable draw-ring (107).
3. Method according to one of claims 1 or 2, characterised in that it comprises a step consisting of preparing the said pre-bending by weakening the said plate along the said bending edges (12-17).
4. Method according to one of the preceding claims, characterised in that it consists in bending the said plate (10) in line with the different edges (12-17) along the length of the said casting, such that tubular sections (3, 3'. 4, 4') of different base profiles are formed.
5. Method according to one of the preceding claims, characterised in that it consists in bending the said plate (10) around at least one virtual geometric axis (a, b, c) defined by the co-operation of the said bending component (103-106) and the associated guidance means (113-116).
6. Method according to one of the preceding claims, characterised in that it consists of exerting the said clamping force (F₇, F₈, F₁₂, F₁₄) essentially on the exterior of a tubular section (3, 3', 4, 4') of the said casting (2), in the absence of clamping force exercised by a draw-ring (107) or similar equipment.
7. Method according to one of the preceding claims, characterised in that the said clamping force (F₇, F₈, F₁₂, F₁₄) is directed overall towards the said edge (12, 13, 15).
8. Method according to one of the preceding claims, characterised in that the said clamping force (F₇, F₈, F₁₂, F₁₄) is perpendicular overall to the said bending edge (12-17).
9. Method according to one of the preceding claims, characterised in that the said clamping force (F₇, F₈, F₁₂, F₁₄) forces one part (23, 24, 25a, 26b) of the said plate (10) parallel to itself and perpendicular to the bending force (F₁, F₃, F₁₁, F₁₃) exercised on this part by the bending component (103-106).
10. Method according to one of the preceding claims, characterised in that the said clamping force (F₇, F₈, F₁₂, F₁₄) is adjusted according to the position of the said bending component (103-106).
11. Method according to one of the preceding claims, characterised in that it comprises a step consisting of placing a first part (26) of the said plate (10) to overlap a second part (25) of the said plate and reducing the clamping force (F₁₂) exerted on the said second part, such that the said first and second parts are in tensile support against each other, the said first and second parts then being welded together.
12. Method according to one of the preceding claims, characterised in that the said plate (10) is bent around at least one virtual axis (a, b, c) defined as the geometric axis of a cylindrical guidance cradle (113-116) of the said bending component (103-106)
13. Method according to claim 12, characterised in that the said plate (10) is bent around the different bending axes (a, b, c) along the length (X-X¹) of the said casting (2) using the bending components (103-106) guided by cradles (113-116) of different geometric axes (a, b, c) corresponding to the said bending axes.
14. Method according to one of the preceding claims, characterised in that it comprises a step consisting, after the formation of several tubular sections (3, 3', 4, 4'), of modelling them into a closed frame (2) by bending the linkage sections (8, 8¹, 8¹¹) between two adjacent tubular sections perpendicular to the principal directions (X-X¹) of the said tubular sections.
15. Method according to one of the preceding claims, characterised in that it comprises a step consisting of plating, by magnetic induction or attraction, one part (23-26) of the said plate against one part (103a-106a) of the said bending component (103-106).
16. Apparatus for producing a casting (2) comprising at least one tubular section (3, 3', 4, 4'), the said apparatus comprising at least one component (103-106) for bending a metal plate (10) in line with a longitudinal edge (12-17) of the said tubular section, characterised in that the said bending component is provided with means (103f-106f) allowing for a clamping force (F₇, F₈, F₁₂, F₁₄) to be exerted on one part (23-26) of the said plate, countering slippage of one part (23-26) of the said plate (10) along the said bending component (103-106), whilst the said bending component is articulated around a virtual geometric axis (a, b, c) situated on the interior of the corresponding tubular section (3, 3', 4, 4')
17. Apparatus according to claim 16, characterised in that it comprises several bending components (103-106) capable of bending the said plate (10) in line with the separate edges (12-17), such that tubular sections (3, 3', 4, 4') of different base profiles are formed.
18. Apparatus according to one of claims 16 or 17, characterised in that the said clamping means comprise at least one lug (103f-106f) forming a butted support for the said plate (10).
19. Apparatus according to claim 18, characterised in that the said lug (103f-104f) extends over approximately the whole length (X-X¹) of the said edge (13).
20. Apparatus according to claim 18, characterised in that the said clamping means comprise several lugs (105f-106f) spread along the length (X-X¹) of the said edge (12, 15) and separated by receiving spaces (105g-106g) for the bending lugs used for bending the said plate (10) along another edge.
21. Apparatus according to one of claims 16 to 20, characterised in that the said clamping means have a variable position (F₉) in relation to the said edge (13).
22. Apparatus according to one of claims 16 to 21, characterised in that it comprises means for regulating or adjusting the force (F₇, F₈, F₁₂, F₁₄) exerted by the said clamping means (103f-106f) on the said plate (10).
23. Apparatus according to one of claims 16 to 22, characterised in that the said bending component (103-106) comprises at least one support surface (104a1-106a1) against the said plate (10) and at least one circular based cylindrical surface (103c-106c) capable of co-operating with a circular based cylindrical surface (113c-116c) of a cradle (113-116), the said cylindrical surfaces being centred on a virtual bending axis (a, b, c) of the said plate.
24. Apparatus according to claim 23, characterised in that it comprises several bending components (103-106) spread along the length (X-X¹) of the said plate (10) and comprising cradles (113-116) whose cylindrical surfaces (113c-116c) have geometric axes (a, b, c) that are parallel to and offset against each other.
25. Apparatus according to one of claims 23 or 24, characterised in that the said or each bending component (103-106) is provided with an external rib (103b-106b) forming a cylindrical surface (103c-106c) capable of co-operating with a cylindrical surface (113c-116c) of the corresponding cradle (113-116), the said cylindrical surfaces being of approximately the same radius (R₁₀₃, R₁₁₃, R₁₀₄, R₁₁₄),
26. Apparatus according to one of claims 23 to 25, characterised in that the said or each bending component (104) is guided in relation to the said surface (114c) of the said cradle (114) by telescopic segments (1041, 1042).
27. Apparatus according to one of claims 25 or 26, characterised in that the said cylindrical surface (103c-106c) of the said rib, the said telescopic segments (1041, 1042) and/or the said surface (113c-116c) of the said cradle (113-116) are provided with sliding balls or rollers (1042g, 1042i).
28. Apparatus according to one of claims 16 to 27, characterised in that it comprises a shaping die (200) for the said casting (2), the said die including support elements (201-204) of tubular sections (3, 3', 4, 4') of the said casting (2) provided with reception and immobilisation means (201d-204d, 201e-204e, 201f-204f, 201g-204g) for the said tubular parts, the said elements being articulated (Y₁, Y₂, Y₃) in relation to each other.
29. Apparatus according to claim 28, characterised in that at least one of the said articulated elements (201-204) is adjustable for length (X₁, X₂, X₃, X₄).
30. Apparatus according to one of claims 28 or 29, characterised in that the said articulated elements (201-204) are capable of forming together a closed figure of predetermined geometry corresponding to the geometry of a frame (2) constituted by the said casting.
31. Apparatus according to one of claims 27 to 30, characterised in that at least one of the said articulated elements (203-204) is equipped with a component (202m or 203m) with a transverse section in the overall form of a U capable of receiving in place in the said element at least one locking wedge (202p, 203p) of one of the said tubular sections (3, 3', 4, 4'), means (202s, 203s) being provided for immobiiising the said wedge on the said component.
32. Apparatus according to one of claims 16 to 31, characterised in that at least one (106) of the said bending components (105-106) is equipped with a blade (106h) forming a cut-out shear for the said plate (10) during its bending (F₁₃).
33. Use of a method according to one of claims 1 to 15, or apparatus according to one of claims 16 to 32 for the manufacture of a shadow mask (1) support frame (2) for a cathode ray tube.

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