EP0348279B1 - Method of finish-machining the two opposed edges of a work piece, and device for carrying out the method - Google Patents

Description

The invention relates to a device allowing the implementation of a method of finishing machining of two opposite edges of the same part, such as those delimiting in particular a female (bore) or male (shaft) cylindrical face of said part. , according to which each edge is shaped by applying two tools under pressure, by controlling simultaneous movements in translation towards each other of the two tools, this device comprising a frame, two pressurized fluid jacks mounted on the frame, having respective movable elements arranged opposite one another and each supporting one of the two said tools, a source of pressurized fluid and a selective device for distributing pressurized fluid disposed between respective working chambers of the two jacks and the source of pressurized fluid, said working chambers being connected in parallel to the source of pressurized fluid by respective supply conduits, so that the effective connection of said working chambers to said source of pressurized fluid by means of said selective distribution device performs said control of the simultaneous movements in translation of the two tools.

FR-A-2 455 489 describes a similar machining process, but in fact limited to a very specific machining application on a relatively thin sheet, which does not have the mechanical strength of the parts machined in accordance with the present invention. In particular, according to this prior art, one of the tools is fixed: if such a means were retained in the method according to the invention, it would cause deformations of the part, incompatible with the desired machining precision.

SU-A-948 488 which represents the closest prior art, describes a device which comprises a frame, two pressurized fluid jacks mounted on the frame, having respective movable elements arranged opposite one of the and each supporting one of the two tools, a source of pressurized fluid and a selective device for distributing pressurized fluid disposed between respective working chambers of the two jacks and the source of pressurized fluid, said working chambers being connected in parallel to the source of pressurized fluid through respective supply conduits, so that the effective connection of said working chambers to said source of pressurized fluid via said selective dispensing device performs said control of the simultaneous movements in translation of the two tools.

The parallel connection of the working chambers is not shown in the prior document, but is implicit and known in the field of presses.

Experience has shown that undesirable deformations occur when the tools are moved towards one another without first making provision for the contact of one particular of these tools on the workpiece.

In order to eliminate the risk of undesirable deformation, the invention provides for a two-phase sequence, according to which the first contact with the part is always made by the same tool, the compression of the part by the two tools moving one towards the other occurring after said first contact. For the realization of this sequence, according to the invention a calibrated relief valve is placed on the supply duct of the working chamber of a first of the two said jacks so that, during said effective connection produced by means of the selective distribution device, the supply of the second of the two said working chambers is first carried out, then that the simultaneous supplies of the two working chambers are then carried out

It may be recalled that to date, the completion of the machining that the invention aims for is done by hand, by particularly skilled workers, capable in particular of performing polishing by grinding the edges of the two ends of each bore of a group of 50 to 100 bores of a mounting flange used in the manufacture of an aircraft jet engine, for example.

Despite their skill and dexterity, it is also obvious that these workers do not manage to obtain consistency in the final shapes of the edges thus finished.

The invention therefore intends to propose a device capable of making it possible to obtain machining precision and to avoid any undesirable deformations, as well, of course, as obtaining automation and repeatability of machining.

Advantageously, before applying the two said tools under pressure to the two said opposite edges, a surface nitriding of the areas of these two edges is carried out.

• tout d'abord, à l'usure près de l'outil, arête après arête, la même forme est obtenue, de sorte que la forme idéale peut être réalisée par répétition non plus d'un tour de main exceptionnel, mais d'une opération mécanique répétitive ;
• un gain de temps pour la finition d'une arête est obtenu ;
• l'état de surface obtenu est également amélioré bien entendu en ce qui concerne les dimensions, mais aussi la rugosité de l'arête qui, après finition, est très faible ;
• le matériau est en outre, dans la zone de l'arête, écroui, ce qui renforce les caractéristiques mécaniques de ce matériau, notamment sa résistance mécanique aux contraintes superficielles, et augmente par conséquent la durée de vie de la pièce.

The advantages derived from the adoption of the process according to the invention are numerous and indicated below:

• first of all, with wear near the tool, edge after edge, the same shape is obtained, so that the ideal shape can be achieved by repeating no longer an exceptional twist, but a repetitive mechanical operation;
• time saved for finishing an edge is obtained;
• the surface condition obtained is also improved of course with regard to the dimensions, but also the roughness of the edge which, after finishing, is very low;
• the material is also, in the region of the edge, hardened, which strengthens the mechanical characteristics of this material, in particular its mechanical resistance to surface stresses, and consequently increases the service life of the part.

The invention will be better understood, and secondary characteristics and their advantages will appear during the description of embodiments given below by way of example.

It is understood that the description and the drawings are given for information only and are not limiting.

• la figure 1 est la coupe axiale d'un alésage, dont les arêtes d'extrémité n'ont pas encore subi la phase de finition conforme à l'invention ;
• la figure 2 est une coupe axiale analogue à celle de la figure 1 et de la même pièce, les arêtes subissant la phase de finition conforme à l'invention ;
• la figure 3 est une coupe suivant III-III de la figure 2 ;
• la figure 4 est une coupe axiale d'un arbre cylindrique, dont les arêtes d'extrémité subissent la phase de finition conforme à l'invention ; et
• la figure 5 est un schéma du dispositif de commande hydraulique d'une machine conforme à l'invention.

Reference will be made to the accompanying drawings, in which:

• Figure 1 is the axial section of a bore, the end edges of which have not yet undergone the finishing phase according to the invention;
• Figure 2 is an axial section similar to that of Figure 1 and of the same part, the edges undergoing the finishing phase according to the invention;
• Figure 3 is a section along III-III of Figure 2;
• Figure 4 is an axial section of a cylindrical shaft, the end edges of which undergo the finishing phase according to the invention; and
• Figure 5 is a diagram of the hydraulic control device of a machine according to the invention.

The machining, which is at the origin of the invention, relates to certain fixing flanges that comprise high-performance gas turbine engines, these flanges comprising numerous holes whose finish, in particular of the edges, must be very careful . The solution provided by the invention to the problem posed could a priori be applied to a machining problem close to the first: that concerning the finishing of the edges of a cylindrical part, and not the edges of a bore. And in fact, the invention also applies to the finishing of this second type of part.

Two applications are set out below, and the differences of the process according to the invention, compared to already known processes, are also indicated.

The first application is schematically represented by Figures 1, 2 and 3.

With reference to FIG. 1, it is noted that a part 1 is already provided with a bore 2 which opens into two parallel faces 3 and 4 delimiting said part. The internal cylindrical face 2 has a bore intersects the faces 3 and 4 along edges 5 and 6, which, in the example shown, have been deburred. According to the axial section of FIG. 1, the edges 5 and 6 are the vertices of right angles, intersections of the cylindrical face 2 a and the plane faces 3 and 4.

Next to each edge 5, 6 is arranged a mandrel 7, 8 which is provided with a surface, in this case toroidal 9, 10, the shape of which is complementary to that which should have, after application under pressure of this mandrel on the corresponding edge 5, 6, said edge, respectively.

• suivant le dessin de la figure 1, le rayon de courbure R de chacune des surfaces 9, 10, contenu dans un plan passant par l'axe 11 de l'alésage 2 (par exemple, contenu dans le plan de la figure 1), est relativement grand : ceci a été voulu afin de bien montrer en quoi consistent les surfaces 9 et 10, étant entendu que, dans la réalité, le rayon R est considérablement plus petit que celui représenté sur là figure ;
• dans la réalité, le rayon de courbure R est tel qu'on peut indiquer que la forme générale de la pièce 1 n'est pas modifiée par l'application sous pression des mandrins 7, 8 sur les arêtes 5, 6, la distance entre les faces 3 et 4 restant inchangée, de même que le diamètre de l'alésage 2 (sauf dans la zone des arêtes 5, 6) :
• la coupe de la figure 3 montre que, dans l'exemple décrit, la surface 2a a une section droite circulaire (et en outre plane) : il convient d'observer que l'invention n'est absolument pas limitée à cette forme de section, et qu'en particulier elle est applicable aussi à la finition d'arêtes 5, 6 de formes gauches (non contenues dans un plan), non nécessairement circulaires ;
• il convient enfin de remarquer qu'aussi bien lorsque les arêtes 5, 6 ont une forme gauche, que lorsque leur forme est plane et circulaire, les mandrins 7 et 8 conservent une orientation constante par rapport à une direction radiale déterminée D (figure 3), la forme définitive des arêtes étant donc obtenue uniquement par pression, à la suite d'un déplacement de translation des mandrins suivant l'axe 11 de l'alésage 2.

The following points should be noted now:

• according to the drawing in FIG. 1, the radius of curvature R of each of the surfaces 9, 10, contained in a plane passing through the axis 11 of the bore 2 (for example, contained in the plane of FIG. 1), is relatively large: this was intended to show clearly what are the surfaces 9 and 10, it being understood that, in reality, the radius R is considerably smaller than that shown in the figure;
• in reality, the radius of curvature R is such that it can be indicated that the general shape of the part 1 is not modified by the pressure application of the mandrels 7, 8 on the edges 5, 6, the distance between the faces 3 and 4 remaining unchanged, as well as the diameter of the bore 2 (except in the region of the edges 5, 6):
• the section in FIG. 3 shows that, in the example described, the surface 2 a has a circular (and also planar) cross section: it should be observed that the invention is absolutely not limited to this form of section, and that in particular it is also applicable to the finishing of edges 5, 6 of left shapes (not contained in a plane), not necessarily circular;
• Finally, it should be noted that both when the edges 5, 6 have a left shape, and when their shape is planar and circular, the mandrels 7 and 8 maintain a constant orientation relative to a determined radial direction D (FIG. 3). , the final shape of the edges therefore being obtained only by pressure, following a translational displacement of the mandrels along the axis 11 of the bore 2.

The desired finished shape of each edge is obtained, from the configuration of FIG. 1, by moving the two mandrels 7 and 8 using a press, and applying compression forces to them 7 a , 8 a (Figure 2) of a value such that each edge takes the finished shape 5 a , 6 a corresponding to the shape 9, 10 of the corresponding mandrel.

It is noted that the two edges are formed by applying compressions having opposite directions (FIG. 2), which is obviously advantageous for the balance of the part 1 being finished, and of the machine itself, but which , in addition, avoids the creation of undesirable deformations of the surface 2 a , deformations which would be caused, otherwise, by the displacement of only one of the two mandrels 7 and 8.

In addition, the areas of edges 5 and 6 have, prior to the finishing with the mandrels 8 and 9, been surface nitrided, according to a treatment depth of between 0.5 mm and 1.5 mm for example. This nitriding facilitates the sliding of the faces 9 and 10 of the mandrels on the edges 5 and 6, and the finished shapes 5 a and 6 have said edges.

It should also be noted that the compressions of the material of the edges 5, 6 by the mandrels 7, 8 are carried out, preferably accompanied by lubrication under very high pressure.

Naturally, a similar process to that just described is also applicable to the finishing of the edges 12 a, 13 has a cylindrical part 14, again using mandrels 7 and 8, of course of suitable forms, including surfaces 15, 16, in the completion of the finishing of such edges 12 a , 13 a (FIG. 4).

The compressions 7 a , 8 a were all carried out cold, in the actual machining operations carried out, that is to say without prior heating of the parts 1 or 14.

This type of finish has, up to now, been carried out on parts whose materials are relatively malleable: refractory alloys used in gas turbines, comprising of the order of 50% chromium and / or nickel, or titanium, and whose elongation coefficient is around, or greater than, 8%.

It is however not excluded that with heating, parts, made of other less malleable materials than those mentioned above, may undergo a finishing of their edges, such as that which has just been described.

• deux vérins hydrauliques 18, 19, dont les cylindres sont fixés sur le bâti 17 de la machine de finition, et dont les pistons 24, 25 délimitent à l'intérieur desdits cylindres deux chambres de travail 20, 21 pour l'extension des vérins, et deux chambres de rétraction 22, 23 pour la rétraction desdits vérins, des tiges de piston 26, 27 étant solidaires des pistons 24, 25 se faisant face et suportant les mandrins 7, 8, respectivement ;
• une pompe 28 ;
• un distributeur de fluide à trois positions 29 ;
• un réservoir de fluide 30 ;
• les conduits d'aspiration 31 et de refoulement 32 reliant la pompe 28 au réservoir 30 et au distributeur de fluide 29 ;
• un conduit 33 reliant le distributeur de fluide 29 au réservoir 30 ;
• un conduit 34 reliant le conduit de refoulement 32 au réservoir 30 ;
• un clapet de décharge 35, de protection contre les surpressions, taré à 350 bars, disposé sur le conduit 34 ;
• un conduit 36, qui est raccordé au distributeur de fluide 29, et auquel sont raccordés en parallèle deux conduits 37, 38, reliés, l'un 37, à la chambre de travail 20, l'autre 38, à la chambre de travail 21 ;
• un conduit 39, qui est raccordé au distributeur de fluide 29, et auquel sont raccordés en parallèle deux conduits 40, 41, reliés, l'un 40, à la chambre de rétraction 22, l'autre 41, à la chambre de rétraction 23 ;
• un clapet de décharge 42, taré à une pression moyenne, 50 bars par exemple, disposé sur le conduit 38 pour permettre le passage du fluide vers la chambre de travail 21 ;
• un conduit 43 raccordé en dérivation au conduit 38, de part et d'autre du clapet de décharge 42 ; et
• un clapet de non-retour 44, disposé sur le conduit 43 et permettant le passage du fluide seulement de la chambre de travail 21 vers le conduit 36.

FIG. 5 represents the device for controlling the respective movements in translation of the mandrels 7 and 8. This device comprises:

• two hydraulic cylinders 18, 19, the cylinders of which are fixed to the frame 17 of the finishing machine, and the pistons 24, 25 of which define two working chambers 20, 21 inside said cylinders for the extension of the cylinders, and two retraction chambers 22, 23 for the retraction of said cylinders, piston rods 26, 27 being integral with pistons 24, 25 facing and supporting the mandrels 7, 8, respectively;
• a pump 28;
• a three-position fluid distributor 29;
• a fluid reservoir 30;
• the suction 31 and discharge 32 conduits connecting the pump 28 to the reservoir 30 and to the fluid distributor 29;
• a conduit 33 connecting the fluid distributor 29 to the reservoir 30;
• a conduit 34 connecting the discharge conduit 32 to the reservoir 30;
• a relief valve 35, for protection against overpressure, calibrated at 350 bars, disposed on the duct 34;
• a conduit 36, which is connected to the fluid distributor 29, and to which are connected in parallel two conduits 37, 38, connected, one 37, to the working chamber 20, the other 38, to the working chamber 21 ;
• a conduit 39, which is connected to the fluid distributor 29, and to which are connected in parallel two conduits 40, 41, connected, one 40, to the retraction chamber 22, the other 41, to the retraction chamber 23 ;
• a discharge valve 42, calibrated at an average pressure, 50 bars for example, arranged on the conduit 38 to allow the passage of the fluid towards the working chamber 21;
• a conduit 43 connected in diversion to the conduit 38, on either side of the relief valve 42; and
• a non-return valve 44, disposed on the conduit 43 and allowing the passage of the fluid only from the working chamber 21 to the conduit 36.

• la première position, à la mise en communication des conduits 32 et 36, et, à la mise en communication des conduits 39 et 33 ;
• la deuxième position, à la mise en communication des conduits 32 et 33, et, à l'obturation des conduits 36 et 39 ; et,
• la troisième position, à la mise en communication des conduits 32 et 39, et, à la mise en communication des conduits 36 et 33.

The three positions of the fluid distributor 29 correspond

• the first position, when the conduits 32 and 36 are connected, and when the conduits 39 and 33 are connected;
• the second position, when the conduits 32 and 33 are placed in communication, and when the conduits 36 and 39 are closed; and,
• the third position, when the conduits 32 and 39 are connected, and when the conduits 36 are connected and 33.

This device operates in the manner described below.

The part 1 is placed on the frame 17 of the machine, on which it rests freely. The operator places the fluid distributor 29 in its first position, which has the effect of directing the pressurized fluid discharged by the pump 28 towards the conduits 36 and 37, and, firstly, closing the conduit 38 by the relief valve 42 and, of course, the conduit 43 by the non-return valve 44. As long as the pressure in the conduit 37 and in the upper working chamber 20 does not reach the set value (50 bars ) of the relief valve 42, only the jack 18 is supplied with fluid: only the mandrel 7 is moved and comes into contact with the part 1. The pressure in the chamber 20 of the jack 18 and in the conduit 37 increases as and measurement of the reinforcement of the support of the mandrel 7 on the part 1, until reaching and exceeding the setting pressure of the relief valve 42.

Then, from this moment, the chambers 20 and 21 of the two jacks are supplied in parallel with pressurized fluid, so that the mandrels 7 and 8 move simultaneously towards each other, and that the edges 5, 6 are formed (5 a , 6 a ). Clearly, edges of training efforts balance and experience has shown that only the provision would avoid the creation of undesirable deformations, for example of the face 2a of the bore or face 14 a from Exhibit 14.

The release of the part 1 is carried out by placing the fluid distributor 29 in its third position and, consequently, by supplying pressurized fluid to the chambers 22, 23 of the jacks 18, 19.

It should be observed that the mandrels 7 and 8 act only in the limited area of the edges 5, 6 (5 a , 6 a ), but have no surface extending perpendicular to the axis of the translations 7 a , 8 a : according to the method according to the invention, there is no lateral draft of the mandrels.

• à l'évidence, ce procédé peut être automatisé et ne requiert alors aucun tour de main, aucune habileté particulière de la part de celui qui le met en oeuvre, d'où une facilité accrue d'application ;
• les formes obtenues des arêtes sont par ailleurs invariables et aussi précises que nécessaire : elles peuvent être reproduites, toujours identiques, autant de fois que l'application prévue l'exige ;
• l'état de surface obtenu est également excellent, et meilleur qu'antérieurement ;
• le matériau subissant un écrouissage superficiel dans la zone de chaque arête a ses caractéristiques mécaniques augmentées, de sorte que la durée de vie de la pièce finie, même soumise à des cycles répétitifs de contraintes, est accrue ; avant l'invention, une pièce endurait 10 000 cycles de contrainte, et peut aujourd'hui en endurer 100 000 cycles ;
• le gain de temps pour réaliser la finition des arêtes est également remarquable ;
• la formation des arêtes, même avec des profils de courbes gauches, non planes, est obtenue sans aucune déformation indésirable de la pièce munie desdites arêtes, ceci étant obtenu grâce à l'équilibrage des efforts de compression.

The main advantages of the finishing process described above are as follows:

• Obviously, this process can be automated and does not require any twist, no particular skill on the part of the one who implements it, hence an increased ease of application;
• the shapes obtained from the edges are moreover invariable and as precise as necessary: they can be reproduced, always identical, as many times as the intended application requires;
• the surface finish obtained is also excellent, and better than before;
• the material undergoing surface hardening in the region of each edge has its increased mechanical characteristics, so that the life of the finished part, even subject to repetitive stress cycles, is increased; before the invention, a part endured 10,000 stress cycles, and can today endure 100,000 cycles;
• the time saved for finishing the edges is also remarkable;
• the formation of the edges, even with profiles of left, non-planar curves, is obtained without any undesirable deformation of the part provided with said edges, this being obtained by balancing the compression forces.

• à l'estampage ou à l'emboutissage qui ont pour but de modifier les formes générales d'une pièce ;
• au galetage qui prévoit le roulement d'un galet presseur, mais ne permet pas, en principe, l'obtention de formes finies gauches (non planes) et répétitives ; et
• à la formation définitive de trous préalablement ébauchés, réalisés dans des plaques minces et ayant des cotes finales peu précises.

It is interesting to observe that the process according to the invention is new compared to:

• stamping or stamping which aims to modify the general shapes of a part;
• roller burnishing which provides for the rolling of a pressure roller, but does not, in principle, allow the production of left (non-planar) and repetitive finished shapes; and
• to the final formation of holes previously roughed out, made in thin plates and having imprecise final dimensions.

Claims (2)

1. Device for implementing a machining method for finishing two opposite edges (5, 6) of a single workpiece (1), such as those delimiting in particular a female (2a) or male (14a) (shaft (14)) cylindrical face of said workpiece, according to which each edge is shaped by pressing under pressure (7a, 8a) two tools (7, 8) by controlling (18-20, 19-21) the two tools to move simultaneously in translation, said device comprising a frame (17), two pressurized fluid actuators (18, 19) mounted on the frame, said actuators having respective moving components (26, 27) disposed in opposite relationship of the other and each supporting one of said two tools (7, 8), a source of fluid under pressure (28), and a device for the selective distribution of the fluid under pressure (29) disposed between respective working chambers (20, 21) of the two actuators and the source of fluid under pressure, said working chambers being connected in parallel (37, 38) to the source of fluid under pressure (28) via respective feed ducts so that the effective connection of said working chambers to said source of fluid under pressure via said selective distribution device causes the two tools to be controlled to move simultaneously in translation,
characterized in that a rated delivery valve (42) is placed on the feed duct (38) to the working chamber (21) of a first (19) of said two actuators, so that when said effective connection is obtained via the selective distribution device (29), feed is applied initially to the second (20) of said two working chambers and is then provided to both working chambers simultaneously.

2. Method for using the device of claim 1, characterized in that prior to pressing under pressure said two tools (7, 8) against the said two opposite edges (5, 6), the zones of said two edges are subjected to surface nitriding.

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