EP0192584B1 - Method and apparatus for making grooves in a surface of revolution - Google Patents

Abstract

The process according to the invention relates to the production of grooves such as helical threads on the wall of tubes composed of ductile or plastic materials without removal of matter. It involves using a knurling tool (11) of radius (R1) which is freely rotatable about an axis (X3). This axis covers, in the direction indicated by the arrow F2, a determined closed curve (12) which, in the figure, is a circumference of radius (R2) and of axis (X4). The enveloping curve of the path of the shaping edge (15) of the knurling tool has a region of intersection (13) with the wall of revolution (10) of axis (X2). The diameter of the knurling tool is greater than the diameter of the circumference (12). A helical thread is obtained by moving the wall of revolution (10) in relative manner along its axis (X2) relative to the knurling tool (11).

Description

The method and the device which are the subject of the invention relate to the production of grooves on the wall of revolution of a hollow body, without removal of material.

They relate more particularly to the production of grooves in the form of helical threads on the wall of revolution of tubes made of ductile materials such as metals or alloys.

Known means are indicated below for making such grooves or helical threads.

Figure 1 is a perspective view of a known device for forming a helical groove by wheel.

This figure schematically represents, in perspective, an existing device.

This device comprises a wheel (1) mounted free in rotation on an axis (X _o ) which rolls continuously on the external wall of a tube (2) which is driven in rotation around its axis (X _l ). The axis (X _o ) is perpendicular to the radius (3) of the tube (2) passing through the intersection zone (4) between the edge (5) of the wheel (1) and the wall of the tube (2). This axis (X _o ) is inclined at an angle (a1) relative to a secant line parallel to the axis (X _i ). It is thus possible to produce on the wall of revolution of the tube (2) a helical thread (6) by a relative movement of translation of this tube (2) along its axis (X ₁ ) relative to the wheel (1 ), combined with its rotational movement around this same axis.

The desired depth of the thread (6) is obtained by exerting sufficient pressure on the knurl (1) so that its edge (5) penetrates the wall of the tube (2) to the desired depth. This pressure depends on the dimensions of the tube (2) and the knob (1), as well as on the depth of the thread (6) to be produced. In the case of tubes whose wall thickness is relatively small, it can be seen that, at instead of obtaining a displacement of material limited to the intersection zone (4) and its immediate vicinity, there is an overall deformation of the tube, elastic, or even permanent, which renders the method inapplicable.

In order to reduce the pressure exerted locally on the tube, it is possible to use several knurling wheels which roll continuously on the tube, passing through the same groove, or helical thread, and are distributed equally around the periphery of the tube. By exerting on each of these rollers, via its axis, a relatively limited pressure, one can obtain, without noticeable deformation of the wall of the tube, the formation of a groove or a thread of depth greater than that that would have been possible by applying the same pressure on a single wheel. The groove created by the first wheel is deepened as each of the following wheels passes. In addition, the distribution of the rollers around the tube makes it possible to balance the forces.

However, in a large number of cases such a method cannot be applied because the tubes are too thin to withstand the pressure of the rollers without significant deformation.

The use of an internal mandrel also does not make it possible to solve the problem because one then observes a swelling of the tube which modifies its dimensions and in particular those of the thread or the groove which one proposes to carry out.

The characteristics contained in the preamble of claims and It are known from document FR-A 1551913.

Patent FR-A 1 551 913 describes a process for forming metallic objects from billets or blanks (page 1, right column, lines 1 to 10) which consists in rotating a series of small working rollers continuously, one after the other in an orbit, mounting a blank so that its superficial zone intersects the orbit and is struck in turn by the rollers, in an uninterrupted succession, so that the metal of the surface area undergoes plastic deformation by following the outline of the rollers. It is essential that these rollers are supported by support rollers or fixed members in their area of action. Figures 1 and 4 of this patent show a cylindrical blank around which a helical groove is formed by means of small rollers (12), mounted in rotation on axes, axes which are distributed around the periphery of a circular cage (10 ) rotary. These rollers are supported by a central roller (16) against which they are supported. It is also possible, as shown in FIG. 2, to use a hinged cage in the form of a chain (10), provided with rollers (22), which performs a closed circuit course in an elliptical orbit by bearing on a support. central (20) against which the rollers (22) bear. The working rollers (12) are also connected to the chain and resting on the rollers (22). The chain is driven by an appropriate mechanism. It is thus possible to produce rectilinear grooves over a certain length as shown in FIG. 2 according to which the central support has two large rectilinear faces connected by short rounded sides. It is thus possible to form a toothing on the periphery of a wheel. Although this document describes only the forming of solid parts, the possibility of also forming hollow blanks is indicated without further details.

Tests have shown that it is possible to use small forming rollers, similar to those which have just been described, to form annular or helical grooves on the cylindrical wall of revolution of hollow bodies, such as tubes, by mounting these rollers on at least one rotary cage which drives them in rotation about its axis. These rollers successively strike the wall of the hollow body which is itself driven in rotation about its axis. This produces an annular groove. By simultaneously moving the hollow body along its axis, a helical groove is obtained.

However, it was found during tests that the use of a series of small rollers or working wheels, following the teaching of FR- A-1 551 913, having a small diameter compared to the dimensions of the orbit or closed path along which they move, presents serious drawbacks. Indeed, if the small diameter of the rollers reduces the stress exerted on the wall of the hollow body, it affects the accuracy of the grooves and the sides thereof. It is also noted that the circular trajectory traversed by knurls of small dimensions relative to the diameter of this trajectory, such as those represented in FIG. 6 of the priority request, has the drawback of being the cause of a succession of shocks exerted by each wheel at the moment when it comes into contact with the wall of the hollow body. These shocks create local faults and in particular tears and folds which it is, in many cases, impossible to eliminate or reduce. They are also a cause of vibrations, which also affect the quality and precision of the profile of the grooves produced.

The tests have in particular shown that the process and the device described in FR-A-1 551 913 do not make it possible to produce on the wall of revolution of a hollow body grooves or helical threads of sufficient quality to allow the 'assembly in good condition of tubes thus threaded at their ends.

These tests also showed that it is not possible to produce such grooves or such threads on non-cylindrical walls of revolution of hollow bodies.

We looked for the possibility of developing a method and a device for its implementation which make it possible to produce annular or helical grooves of high precision, free of local defects. The possibility has also been sought of producing such grooves in walls of relatively thin hollow bodies without significant deformation outside the region in the immediate vicinity of the groove. Finally, we looked for the possibility of developing a process for making such grooves or threads on the wall of revolution of hollow bodies of non-cylindrical shape, in order to be able in particular to adapt the process to the production of helical threads on ends. conical tubes to obtain screw connections with conical threads of satisfactory quality.

The method and the device according to the invention make it possible to solve these problems in a particularly effective manner.

The method according to the invention makes it possible to form, without removing material, at least one groove, on the wall of revolution of a hollow body made of a ductile or plastic material. In this process, at least one revolution wheel is used, comprising at least one forming edge, mounted to rotate freely on an axis. This axis moves parallel to itself so that its point of intersection with a perpendicular plane cyclically performs a course reserved for it along a determined closed curve, of circular or elongated shape, said course not being followed by no other wheel. The envelope curve of the path of at least one forming edge of the thumbwheel comprises an area of intersection with the wall of revolution, an area which moves relatively around this wall.

The wheel has at least one forming edge, the largest diameter of which is greater than the length of the diagonal of the determined closed curve, the extension of which intersects the intersection zone in the middle as well as the axis of the hollow body. If the determined closed curve is a circumference, the diameter of the latter is therefore less than that of the wheel. Advantageously, the determined closed curve has an elongated shape. It is preferably oriented so that the diagonal of this curve, the extension of which intersects the intersection zone in its middle as well as the axis of the wall of revolution of the hollow body, is substantially perpendicular to the longest diagonal of this curve. closed determined.

A helical groove is produced on the wall of revolution of the hollow body by a relative translational movement of this wall of revolution along its axis with respect to the intersection zone associated with a rotational movement of said wall.

Advantageously, the plane of the envelope curve of the path of the forming edge of the wheel can be oriented around an axis contained in this plane and intersecting both the axis of the wall of revolution and the intersection zone.

Preferably, when a helical groove is formed, the plane of the envelope curve is oriented so that, in the intersection zone, it is parallel to a tangent to the helical groove in progress.

Advantageously, several knurls are used distributed around the axis of the wall of revolution of the hollow body so that the envelope curves of their forming edges have with the wall of revolution different areas of intersection distributed around this wall. of revolution. Advantageously also when at least two knurls are used to produce the same groove in a wall of revolution, the envelope curves of their forming edges have, in their areas of intersection with this wall, different penetration depths.

When a helical groove is produced on a non-cylindrical wall of revolution of a hollow body, the distance between the axis of this wall of revolution and at least one envelope curve corresponding to the path of the forming edge of the material is varied. a wheel to control the depth of the intersection area.

Preferably for an observer placed in the extension of the axis of the wall of revolution of the hollow body, the direction of rotation of this wall of revolution and the direction of travel of a closed curve determined by the axis of the corresponding wheel are the same.

Advantageously, a smoothing wheel whose axis is hand is used in combination with at least one forming wheel. kept at a substantially constant distance from the wall of revolution and the edge of which rolls in a groove already formed by the forming wheel, by continuously exerting pressure on the bottom and the side walls of this groove.

The method according to the invention applies in particular to the production of grooves, in the form of helical threads, on the end wall of metallic, cylindrical or conical tubes, in order to produce good quality screwed assemblies for example by means of of female threaded fittings.

The invention also relates to a device for forming grooves without removing material, on the wall of revolution of a hollow body made of a ductile or plastic material by means of at least one revolution wheel, mounted freely in rotation on an axis and provided with at least one forming edge. This device comprises a support rotatable around an axis, connected to a first means for driving in rotation, and provided with gripping means making it possible to grasp a hollow body, comprising a wall of revolution, so that the axis of this wall coincides with the axis of rotation of the support. This device also comprises at least one rigid wheel holder on which is mounted a single free wheel in rotation on an axis integral with this wheel holder. A second drive means cyclically moves this wheel holder so that the wheel axis moves parallel to itself and its point of intersection with a perpendicular plane cyclically traverses a determined closed curve, circular or elongated shape, an adjustment means making it possible to vary the distance between the wheel holder and the wall of revolution, so that the envelope-curve of the cyclic movement of at least one forming edge of the wheel has a zone of intersection with this wall of revolution.

The thumbwheel has at least the forming edge, the largest diameter of which is greater than the length of a diagonal of the determined closed curve, the extension of which intersects the intersection zone in the middle as well as the axis of the wall of revolution. of the hollow body.

The device advantageously comprises a third drive means which allows a relative translation of the wall of revolution of the hollow body along its axis relative to at least one forming wheel mounted on the wheel holder which corresponds to it.

Advantageously, at least one wheel holder is orientable about an axis which is in the plane of the envelope curve of the path of at least one forming edge of the single wheel which corresponds to this wheel holder. This axis intersects both the axis of the wall of revolution and the area of intersection between this wall of revolution and this curve-envelope.

Advantageously, the movement of the wheel holder is carried out so that the determined closed curve has an elongated shape. It is then preferably oriented in such a way that a diagonal located in its plane, the extension of which cuts the intersection zone in its middle as well as the axis of the wall of revolution of the hollow body, is substantially perpendicular to the most long diagonal of this determined closed curve.

The device advantageously comprises a fourth drive means which makes it possible to move at least one wheel-holder in the direction of the axis of the wall of revolution as a function of the relative translation of the wall of revolution along its axis relative to this wheel holder.

Preferably the device comprises several wheel holders each equipped with a single forming wheel distributed around the axis of the wall of revolution.

Advantageously, the device comprises at least one wheel which has several forming edges.

Advantageously also the device comprises at least one wheel holder equipped with a smoothing wheel whose axis does not effect cyclic movement. This wheel holder comprises an adjustment means which makes it possible to press the edge of the smoothing wheel against the walls of a groove already formed on the wall of revolution of the hollow body.

• Les figures dont la liste suit illustrent ces modes de mise en oeuvre.
• La figure 2 est une vue en coupe schématique d'un premier mode de mise en oeuvre de l'invention.
• La figure 3 est une vue en coupe schématique d'un deuxième mode de mise en oeuvre de l'invention.
• La figure 4 est une vue en coupe partielle d'un jeu de molettes à deux bords de formage.
• La figure 5 est une vue schématique du formage d'un filet hélicoïdal sur la paroi cylindrique de révolution d'un corps creux au moyen d'une molette par un mode de mise en oeuvre de l'invention.
• La figure 6 est une vue schématique du formage d'un filet hélicoïdal sur la paroi conique de révolution d'un corps creux par un mode de mise en oeuvre de l'invention.
• La figure 7 est une vue d'un mode de réalisation du dispositif suivant l'invention dans lequel l'axe de molette effectue un parcours suivant une courbe fermée déterminée non circulaire.
• La figure 8 est une vue d'un autre mode de réalisation du dispositif suivant l'invention comportant des porte-molette orientables.
• La figure 9 est un détail d'une molette de la figure 8.
• La figure 2 représente, de façon schématique, un premier mode de réalisation du procédé suivant l'invention.

Advantageous embodiments of the method and of the device according to the invention are described below, without limitation.

• The figures whose list follows illustrate these modes of implementation.
• Figure 2 is a schematic sectional view of a first embodiment of the invention.
• Figure 3 is a schematic sectional view of a second embodiment of the invention.
• Figure 4 is a partial sectional view of a set of rollers with two forming edges.
• Figure 5 is a schematic view of the formation of a helical thread on the cylindrical wall of revolution of a hollow body by means of a wheel by an embodiment of the invention.
• Figure 6 is a schematic view of the formation of a helical thread on the conical wall of revolution of a hollow body by an embodiment of the invention.
• Figure 7 is a view of an embodiment of the device according to the invention in which the wheel axis performs a course along a closed curve determined non-circular.
• Figure 8 is a view of another embodiment of the device according to the invention comprising adjustable wheel-holders.
• FIG. 9 is a detail of a wheel of FIG. 8.
• FIG. 2 schematically represents a first embodiment of the method according to the invention.

The wall of revolution (10) of a hollow body is seen in section along a plane perpendicular to its axis (X ₂ ). The revolution wheel (11) is mounted to rotate freely on an axis (X ₃ ) which is driven in gyration parallel to itself around the axis (X ₄ ) by a drive means not shown. We see that the radius (R ₁ of the forming edge of the wheel (11) is larger than the radius of gyration (R ₂ ) of the axis (X ₃ ) around the axis (X ₄ ). of the forming edge of the thumbwheel is therefore greater than that of any diagonal of the determined closed curve (12) and therefore, a fortiori, greater than that of the diagonal whose extension cuts the intersection zone (13) in its middle as well as the axis (X ₂ ). As a result, the radius (R ₃ ) of the envelope curve (14) is greater than (R ₁ ) and tends to approach it when the value of (R ₂ ) Such an arrangement reduces the angle of incidence of the forming edge (15) of the thumbwheel when it comes into contact with the bottom of the groove (16) during formation. This results in a better state of surface of the groove walls and therefore greater precision. We also note that the directions of rotation of the wall of revolution (10) and gyration of the axis (X ₃ ) around the axis (X ₄ ) indicated by arrows ches (F ₁ ) and (F ₂ ) are the same. It is found that this is how the best results are obtained: the arrow (F ₃ ) indicates the direction of rolling of the wheel (11). As seen below, the results are particularly favorable in the case of the production of helical threads on the wall of revolution of the hollow body.

Figure 3 shows, schematically, another embodiment of the method according to the invention. The wall of revolution (20) of a hollow body with an axis (X ₅ ) is shown in section, perpendicular to this axis. A thumbwheel (21) is mounted, free to rotate, on an axis (X _s ) perpendicular to the plane of the figure. This axis, in accordance with the method according to the invention, moves parallel to itself so that its point of intersection with a perpendicular plane cyclically follows a path reserved for it, according to the closed curve determined not circular (22 ). This course is carried out in the direction of the arrow (F ₄ ) thanks to a rigid and mobile wheel-holder, not shown, which drives the axis (Y ₆ ). This curve (22) is elongated and similar in shape to an oval or an ellipse. Its largest diagonal (BC) is oriented relative to the hollow body of axis (X ₅ ) in such a way that it intersects at point (M), substantially at right angles, the diagonal (ED) whose extension cuts in its middle the intersection zone (25) between the curve-envelope (23) of the course of the forming edge of the wheel (21) and the wall (20) of the hollow body and also intersects the axis (X ₅ ). In the case of this figure the diagonal (BC) is substantially parallel to the tangent (T) to the curve (23) in the intersection zone (25). It is found that it is sufficient that the length of the short diagonal (ED) is at least equal to the depth of penetration (el) of the edge of the wheel in the wall (20) so that there is no possible interaction between this edge and this wall during the return path of the axis (X _s ) along the branch (B, E, C) of the curve (22). The arrow (F ₅ ) indicates the direction of rotation of the wheel in contact with the wall (20). The arrow (F ₆ ) indicates the direction of rotation of the wall (20) around the axis (X ₅ ). Experience has shown that the direction of rotation of this wall is preferably the same as the direction of travel of the closed curve determined by the point of intersection of the axis (X _s ) with this curve.

The observer who looks at Figure 3 and is therefore in the extension of the axis (X ₅ ) sees that the direction of the arrows (F ₄ ) and (F _e ) is that of the hands of a watch. The oval shape of the determined closed curve (22) has the very great advantage of reducing the angle of attack of the forming edge of the wheel (21), when it comes into contact with the wall (20), this which greatly reduces the shock caused at this time. The increased diameter of the wheel (21), which is made possible by the use of a single wheel, guided along the path of the closed curve (22), acts essentially in the direction of a progressive action the forming edge (24) on the wall (20). There is thus obtained a groove practically free from the defects which are observed in the case of multiple rollers or rollers of small diameter mounted on a single roll holder and describing a circular trajectory of large diameter relative to that of the rollers or rollers.

The quality of the groove is also a function of the forming work carried out at each passage of the forming edge of the wheel (21) in the intersection zone (25). This unit forming work is adjusted by acting on the one hand on the frequency of the travel of the envelope curve (23) by the forming edge (24) and on the other hand on the speed of rotation of the wall (20) around of its axis (X ₅ ). This forming work must, in any case, remain below the limit which would cause unacceptable permanent deformation of the wall of the tube (20) over its entire thickness.

In most cases it is advantageous to use several knobs.

These are distributed around the wall of revolution of the hollow body and the axis of each of them moves so that its point of intersection with a perpendicular plane traverses the determined closed curve which corresponds to it. The curve of the course of the forming edge of each wheel has its own distinct area of intersection with the wall. It is advantageous that the determined closed curves traversed by the axes of the rollers are similar in order to balance the forces exerted on the wall, but this is not a necessity. The drive of each of the wheels, so that its axis traverses the determined closed curve which corresponds to it, is carried out, as has been said in the case of FIG. 3, by means of a corresponding rigid and mobile wheel-holder. The rollers can be arranged so that the envelope curves of the paths of their forming edges lie in the same plane perpendicular to the axis of the wall of revolution of the hollow body. This forms an annular groove successively traversed by the knobs used.

You can also form a helical groove in moving along its axis the wall of revolution at a speed synchronized with the speed of rotation of the wall of revolution in order to precisely define the pitch of the propeller. It is often preferred to do the opposite, that is to say, to simply rotate the wall of revolution of the hollow body, for example by means of a tower plate to which it is fixed. A frame is then secured, on which the wheel holders which drive the wheels are mounted, with the carriage of the lathe.

This carriage can then move, in synchronism with the speed of rotation of the wall of revolution, thanks to the mother screw of the lathe. The forming edges of the rollers must be offset from each other, parallel to the axis of the hollow body, so as to contribute to the formation of the same helical groove. If for example 4 knurls are distributed at 90 ° from each other around the same wall of revolution, in order to achieve a helical groove of pitch (P), the most forward knurl attacks the formation of the groove, while that the three others who continue to form this same groove must be offset by

along the axis.

It is possible to gradually form the grooves using knobs of different diameters in order to vary the depth of penetration. The profiles of the forming edges can also vary from one wheel to another in order to gradually produce the profile of the groove which must be obtained. Instead of varying the diameters of the wheels, it is also possible to vary the depth of the intersection zone between the envelope curve of the path of the forming edge and the wall of revolution of the hollow body.

It is advantageous, in certain cases, to use multiple knurling wheels, that is to say having several forming edges; this allows several passages on the same helical groove. Such multiple knurls can also make it possible to produce threads comprising several parallel helical threads.

FIG. 4 schematically represents half-sections of four knurls (26, 27, 28, 29) mounted free in rotation around four axes (X ₇ , X ₈ , Xg, X ₁₀ ). These knobs are distributed around the wall of revolution of a hollow body and the axis of each of them traverses a determined closed curve, circular in the manner which is represented in FIG. 2. The areas of intersection of the curves- envelopes of the paths of the forming edges of each of these knurls are distributed substantially at 90 ° from one another around the wall of revolution. In addition, as has been said above, as it is proposed to produce a helical thread of pitch P, the first wheel (26) which attacks the formation of the thread, is followed by the other three (27, 28, 29) which are offset respectively parallel to the axis of the hollow body, by

Each of these wheels has two forming edges: (A ,, and B ₁ , A ₂ and B ₂ , A ₃ and B ₃ , A ₄ and B ₄ ). The forming edges (A ,, A ₂ , A ₃ , A ₄ ) have respective radii (R _I , R ₂ , R ₃ , R ₄ ) increasing, which makes it possible to form in a single revolution of the wall around its axis a helical thread having the desired depth. The second forming edges (B ₁ , B ₂ , B ₃ , B ₄ ) have substantially the same radius equal to (R ₄ ). Their passage during a second revolution of the wall, in the thread already formed by the first forming edges, equalizes the thread by eliminating certain inequalities and possibly increasing the surface hardening. Of course the second forming edge (B _i , B ₂ , B ₃ , B ₄ ) is offset on each wheel (26, 27, 28, 29) relative to the first forming edge (A ₁ , A ₂ , A ₃ , A ₄ ) the desired distance for the metal to be worked at the desired location.

When making a groove in the form of a helical thread, the accuracy is improved by orienting the axes of the knurls so that the lateral flanks of their forming edges are substantially parallel to a tangent to the helical thread in the intersection zone.

We see in Figure 5, shown in plan, the cylindrical wall of revolution of a hollow body (30) of axis (X ₁₁ ) on which a groove in the form of a helical thread (31) is being formed. A thumbwheel (32) is shown in the area of intersection of the envelope curve of its forming edge with the wall of the hollow body (30). This wheel is rotatably mounted on an axis (X ₁₂ ) which, itself mounted on a mobile wheel holder, cyclically travels along a determined closed curve while maintaining its orientation. This axis (X ₁₂ ) is in a plane substantially parallel to the plane tangent to the generatrix of the wall of the hollow body (30) passing through the intersection area specified above. In the case of Figure 5 this tangent plane is substantially parallel to the plane of the figure. We see that the axis (X ₁₂ ) is inclined at an angle "α2" relative to a parallel to the axis of revolution (X _I1 ) which intersects it. This angle "a2" is preferably substantially equal to the angle "α3" of inclination of a tangent to the helical thread (31) relative to the plane perpendicular to the axis (X ₁₁ ), the plane of which we see the trace in (33). The inclination of an axis such as (X ₁₂ ) of a wheel such as (32) is obtained by rotating the wheel holder (not shown) around an axis perpendicular to the axis (X ₁₁ ) of the wall of revolution and passing through the intersection zone between the envelope curve of the forming edge of the thumbwheel (32) and the wall of revolution (30) of the hollow body. Such a means of tilting the wheel axes can, for example, be implemented each time it is proposed to make a groove or a helical thread.

Figure 6 shows the wall of revolution (34) of a hollow body of axis (X _l3 ) whose outer surface is conical. A helical thread (35) is formed on this surface, by means of knobs such as (36), which rotate around axes such as (X ₁₄ ). Each of these wheels is mounted on a corresponding wheel holder not shown. In the case of this figure, the wheel axis (X, ₄ ) is in a plane parallel to the axis of revolution (X ₁₃ ), and perpendicular to a line, itself perpendicular to this axis, line which passes through the intersection zone between the envelope curve of the cyclic path of the forming edge of the thumb wheel and the wall. This plane therefore makes, with a parallel (37) to the generator (38) of the conical wall, an age "a4" equal to the half-angle at the top of the cone. Under these conditions, the forming edge of each wheel does not act symmetrically on the wall. This has few drawbacks if the angle "α4" is small. It is also possible, as has been explained in the case of FIG. 5, to orient the axes of knurls such as (X ₁₄ ) so that the lateral flanks of the forming edges are made parallel to the helical thread (35). This orientation is achieved by rotation of the wheel holder around an axis perpendicular to the axis (X ₁₃ ) passing through the intersection zone between curve-envelope and wall.

During the relative translation of the wall of revolution (34) along its axis (X, ₃ ) relative to the wheel (36), the distance between the wheel holder and the axis (X, ₃ ) so that the envelope curve of the course of the forming edge of the thumbwheel (36) constantly intersects the wall of revolution with a substantially constant penetration. A known means of cone tracking is used for this.

FIG. 7 describes a particular embodiment of the device according to the invention.

We see a wall of revolution (40) in section, of axis (X, ₅ ) perpendicular to the plane of the sheet. A wheel (41) is mounted for free rotation on an axis (X ₁₆ ) secured to a movable rigid wheel holder (42). This wheel-holder is mounted free in rotation on a crank pin (43) whose axis (X ₁₇ ) rotates around the axis (X, ₈ ) which drives it in rotation clockwise by a motor means not shown. A link (44) articulated at (X ₁₉ ) on the wheel holder and at (X ₂₀ ) on a retaining ring (45) contributes to guiding the wheel holder (42). The axes (X, ₆ , X ₁₇ , X ₁₈ , X ₁₉ and X _2o ) are parallel. It follows that when the axis (X ₁₇ ) of the crankpin is driven around the axis (X ₁₈ ) in a clockwise direction by the drive means, the wheel axis (X ₁₆ ) follows cyclically the determined closed curve (46) in the direction of the arrow (F ₇ ). The envelope curve (47) of the course of the forming edge of the thumbwheel has an intersection zone (48) with the wall (40). The determined closed curve (46) has a larger diagonal (X ₂₁ ), which is also the large diagonal of the envelope curve (47). The straight line (49) coming from the axis (X ₁₆ ) and passing through the middle of the intersection zone (48) cuts (X ₂₁ ) substantially at right angles. Such an arrangement makes it possible to obtain a small angle of incidence of the forming edge of the wheel when, at each cycle, it engages in the intersection zone. It is also possible, by rotating the ring (45) around its axis in a suitable direction, to move the envelope-curve (47) closer or further away from the wall of revolution (40) and therefore to adjust the penetration depth of the wheel edge, or even to follow a cone. It is therefore possible thus, to produce on a conical wall a helical thread (50) of constant depth. Note that the wheel axis (X ₁₆ ) runs along the determined closed curve (46) clockwise (arrow direction (F _l ). This direction is the same as the direction of rotation of the wall (40) indicated by the arrow (F _a ). The wheel rolls in the direction of the arrow (Fg). It is possible, by means not shown, to rotate the plane of the envelope curve (47) around 'an axis such as the straight line (49) so as to orient it parallel to a tangent to a helical thread passing through the intersection zone (48).

Figure 8 and the detail figure 9 show in perspective, partially, another embodiment of the device according to the invention. In the case of the device thus represented, 4 knurls each mounted on a knurl holder are used, distributed at 90 ° from one another around the axis (X ₂₂ ) of a hollow body (59) on the wall of revolution (60) from which it is proposed to produce a helical thread. A drive means rotates this wall (60) about its axis (X ₂₂ ) in the direction of the flece (F _lo ). In order to simplify FIG. 8, only two rollers (61 and 62), each mounted on a roll holder support (63, 64) and distributed at 180 ° around the axis (X ₂₂ ) have been shown.

Figure 9 shows clearly that the wheel (65) is an annular part mounted free in rotation by means of a rolling ring (66) on a part (67) having a cylindrical bearing axis (X ₃₃ ) which constitutes the axis of the wheel. A drive means in rotation not shown rotates a shaft (68) of axis (X ₂₄ ) which drives around it the axis (X ₂₃ ) which is parallel to it, so that the point of intersection of this axis (X ₂₃ ) with a perpendicular plane describes in a cyclic way a path following a determined closed curve. The part (67) is therefore the rigid and mobile wheel holder on which the wheel (65) is mounted. In the case of FIG. 9, this determined closed curve is a circumference whose radius is equal to the distance between the axes (X ₂₃ ) and X ₂₄ ). During its cyclical course the forming edge (69) of the wheel (65) describes an envelope curve (70).

As shown in Figure 8 each of the wheel holder supports (63, 64) can rotate around an axis (X ₂₅ ) perpendicular to the axis (X ₂₂ ) and which crosses the intersection zones of the envelope curves paths of the forming edges of the rollers (61, 62) with the wall of revolution (60). For this each wheel holder support is rotatably mounted about this axis (X ₂₅ ) on the carriage (71, 72) which carries it. Verniers (73, 74) make it possible to adjust the inclination of the support (63, 64) and therefore of the corresponding wheel holder so that the envelope curve of the course of the forming edge of the wheel is parallel to the tangent to the thread helical to perform in the intersection area. Each of the carriages (71, 72) can slide radially in one direction or the other according to the arrows (F ₁₁ , F ₁₂ ) relative to the axis (X22) in slides such as (75,76) formed in fixed support parts (77,78).

The radial movement of all of the carriages is controlled by means of a crown (79) which can be rotated in one direction or the other, according to the arrow (FI3) around its axis, which is practically coincident with the axis (X22). The crown (79) carries rollers (80, 81) engaged in inclined notches (82, 83) formed at the ends of the carriages (71, 72). Thus it is possible, thanks to an appropriate control means, to simultaneously move the wheel supports radially. This allows in particular the cone tracking. As in the examples already mentioned, helical threads are produced by moving the hollow body (59) relatively along its axis (X22) relative to the knurls in translation. In the case of the production of a helical thread on a conical wall, the translational movement of the hollow body (59) is synchronized along the axis (X22), by known means, with the simultaneous radial displacement of the doors. -wheels by the action of the crown (79).

As already indicated, it is possible to equalize the depth of a groove, in particular in the case where this is a helical thread. by rolling a smoothing wheel at constant pressure, the axis of which is kept at a substantially constant distance from the wall of revolution. In the case of the embodiment of the device according to the invention, it is possible in particular to replace on one of the wheel holder supports the cyclic drive device of the wheel holder by a device in which the wheel axis is fixed. relative to the wheel holder support. We can then have in the direction of advance of the helical thread 3 forming wheels with cyclic action, so as to gradually form the thread to the desired depth. The fourth wheel holder will be equipped with a smoothing wheel whose axis distance with the wall of revolution will be set to a fixed value so that the wheel rolls continuously in the bottom of the already formed net, equalizing its walls. The profile of this smoothing wheel will correspond to the final profile that we propose to give to the helical thread. In order to further improve the profile of the thread, one can distribute around the axis of the wall of revolution, for example, 6 wheel holder supports instead of 4, and equip 2 of these supports with smoothing wheels to fixed axis which roll continuously at the bottom of the net, equalizing the profile.

• 1 ère molette: 0,4 mm
• 2ème molette: 0,8 mm
• 3ème molette: 1,2 mm
• 4ème molette: 1,2 mm

By way of digital example, a device corresponding to that of FIGS. 8 and 9 is used to produce a helical thread on the outside wall of a steel tube 3½ inches in outside diameter and 6 mm wall thickness. This tube is rotated about its axis at the speed of 9 revolutions / min. and the tube is moved in translation along its axis, relatively with respect to the rollers at a speed of 38.1 mm / min. The four wheel holder supports, arranged at 90 ° from each other, are each equipped with a 61 mm diameter wheel provided with a single forming edge. Three of these wheels are mounted free in rotation as shown in Figure 9, that is to say that their axis moves cyclically parallel to itself following a circumference located in a plane which is perpendicular to it under the action of a drive means not shown. The radius of this circumference is 0.4 mm and the number of cycles is from 2000 to 3000 / min. depending on the material to be formed. The fourth wheel is a smoothing wheel mounted freely in rotation on a fixed axis. The wheel holder supports are adjusted in radial distance from the tube wall so that the maximum total penetration depth of each of the forming edges of the wheels is:

• 1st wheel: 0.4 mm
• 2nd wheel: 0.8 mm
• 3rd wheel: 1.2 mm
• 4th wheel: 1.2 mm

We see that the first 3 knobs gradually form the thread, each carrying a clean penetration of 0.4 mm. The fourth wheel works at the depth reached by the third, but at constant depth, thus equalizing the thread.

The wheel holder supports are inclined, as just described, so that the envelope curve of the path of the forming edge of each of the first three knobs is parallel to the tangent to the helical thread to be produced. The same inclination is given to the wheel holder support on which the fourth wheel with fixed axis is mounted. It can be seen that the helical thread thus produced has excellent precision and an excellent surface condition and that the internal dimensions of the tube have not been substantially modified in the area in which the external thread is produced.

Many modifications can be made, for their implementation, to the method and to the device, for their implementation, which have just been described without departing from the scope of the invention. It is in particular possible to adapt the knobs to the production of any groove profile that it is proposed to produce. In the case where the groove which it is proposed to produce is a helical thread, the profile of the latter can be given the optimal shape in order to obtain, for example, the qualities of tightness and tightness expected from 'a screwed junction.

Claims (20)

1. A process for the non-cutting shaping of grooves on revolving walls of hollow bodies made of ductile or plastic material, in which there is used at least one revolving wheel (11, 21) rotatably mounted on an axis which moves in parallel with itself so that its point of intersection with a perpendicular plane travels cyclically along a determined closed curve (12, 22) having a circular or elongate shape, this wheel comprising at least one shaping edge (15, 24) the envelope curve of whose cyclic path comprises a region of intersection (13, 25) with the revolving wall, this region moving relatively about this wall, characterised in that the determined closed curve (12, 22) is not traversed by the point of intersection of the axis of another wheel and in that the greatest diameter of the shaping edge (15, 24) of this wheel is greater than the length of a diagonal (E-D) of the determined closed curve, the extension of which cuts the region of intersection (13, 25) as well as the axis (X₂, X₅) of the hollow body.

2. A process according to claim 1, characterised in that when the determined closed curve (22) has an elongate shape it is orientated such that one of its diagonals (E-D), the extension of which cuts the region of intersection (25) and also cuts the axis (X₅) of the revolving wall of the hollow body, is substantially perpendicular to the longest diagonal (B-C) of this determined closed curve.

3. A process according to claim 1 or 2, characterised in that a helical groove (31, 35) is produced on the revolving wall of the hollow body (30,34) by relative translation ofthis wall along its axis with respect to the region of intersection combined with a rotational movement of said wall.

4. A process according to one of claims 1 to 3, characterised in that the plane of the envelope curve of the path of the shaping edge of the wheel (61, 62) can be orientated about an axis (X₂₅) contained in this plane which cuts the region of intersection as well as the axis (X22) of the revolving wall of the hollow body.

5. A process according to claim 4, characterised in that the plane of the envelope curve is orientated so as to be parallel to a tangent to the helical groove (31) as it is being produced in the region of intersection.

6. A process according to one of claims 1 to 5, characterised in that there are used several wheels (61, 62) distributed such that the envelope curves correponding to the path of the shaping edges of each of them have different regions of intersection with the revolving wall (60) which are distributed round this revolving wall.

7. A process according to one of claims 1 to 6, characterised in that, to produce a helical groove on a non-cylindrical revolving wall (34) of a hollow body, the distance between the axis of this revolving wall and at least one envelope curve corresponding to the path of the shaping edge of a wheel (36) is varied so as to control the depth of the region of intersection.

8. A process according to one of claims 1 to 7, characterised in that, for an observer placed in the extension of the axis of the revolving wall, the direction of rotation (F1, F6) of this wall (10, 20) and the direction of travel (F2, F4) of a determined closed curve (12, 22) through the point of intersection of the axis of the corresponding wheel are the same.

9. A process according to one of claims 1 to 8, characterised in that, in combination with at least one shaping wheel, there is used a smoothing wheel, of which the axis is kept at a substantially constant distance from the revolving wall and of which the edge rolls in a groove already formed upstream of this shaping wheel.

10. Application of the process according to one of claims 1 to 9 to the production of grooves in the form of helical threads on the cylindrical or conical end wall of metal tubes for production of screwed connections.

11. A device for the non-cutting shaping of grooves on revolving walls of hollow bodies made of ductile or plastic material, comprising a support which is rotatable about an axis connected to a first means of rotation and equipped with gripping means allowing a hollow body comprising a revolving wall to be gripped such that the axis of this wall coincides with the axis of rotation of the support, and comprising at least one revolving wheel rotatably mounted on an axis which moves in parallel with itself so that its point of intersection with a perpendicular plane travels cyclically along a determined closed curve of circular or elongate shape, this wheel comprising at least one shaping edge the envelope curve of whose cyclic path comprises a region of intersection with the revolving wall, this region moving relatively about this wall, characterised in that it comprises at least one rigid wheel holder (42, 67) on which a single wheel (41, 65) is mounted freely rotatably about an axis (X_16' X₂₃) integral with this wheel holder, a second driving means (43, X₂₄) moving this wheel holder cyclically such that the point of intersection of the wheel axis with a perpendicular plane travels cyclically along a circular or elongate determined closed curve, the wheel mounted on this axis comprising at least one shaping edge, the greatest diameter of which is greater than the length of a diagonal (E-D) of the determined closed curve (46) and of which the extension cuts the region of intersection (48) as well as the axis (X,₅) of the revolving wall (40) of the hollow body and in that it comprises an adjusting means (44,71) for varying the distance between wheel holder and revolving wall so as to adjust the depth of penetration of the edge of the wheel in the revolving wall.

12. A device according to claim 11, characterised in that a means of translation allows the hollow body (59) to move along its axis (X22) relative to the wheels and synchronously with its movement of revolution about this same axis (X₂₂) so as to form a helical groove.

13. A device according to claims 11 or 12, characterised in that the determined closed curve (46) is lengthened and its greatest diagonal (X₂₁) is substantially perpendicular to a diagonal of which the extension (49) cuts the region of intersection (48) as well as the axis (X₁₅) of the revolving wall.

14. A device according to one of claims 11 to 13, characterised in that at least one wheel holder (67) can be orientated about an axis (X₂₅) located in the plane of the anvelope curve of the path of at least one shaping adge of the wheel corresponding to this wheel holder, this axis cutting both the region of intersection and the axis (X22) of the revolving wall.

15. A device according to one of claims 11 to 14, characterised in that a driving means (79) moves at least one wheel holder in the direction of the axis (X_u) of the revolving wall (60) as a function of the relative translation of this wall along this axis with respect to this wheel holder.

16. A device according to one of claims 11 to 15, characterised in that it comprises several wheel holders each equipped with a single shaping wheel (61,62) distributed round the axis of the revolving wall.

17. A device according to one of claims 11 to 16, characterised in that at least one wheel (26, 27, 28, 29) comprises several shaping edges (A1 -81, A2-B2, A3-B3, A4-B4).

18. A device according to one of claims 11 to 17, characterised in that at least one wheel holder is equipped with a smoothing wheel, the axis of which does not move cyclically, the device also comprising at least one wheel holder equipped with a shaping wheel arranged so as to form a groove inside which the smoothing located upstream rolls continuously.

19. A device according to claim 16, characterised in that when several shaping wheels (26, 27, 28, 29) pass through the same groove or thread, they are arranged such that the depth of the region of intersection of the envelope curve of the path of shaping edge of at least one of them is different from the depth of intersection of the envelope curve corresponding to an edge of at least one other wheel.

20. A device according to one of claims 11 to 19, characterised in that when the determined closed curve (22) is lengthened, the length of the short diagonal (E-D) is at least equal to the depth of penetration (el) of the edge of the wheel in the revolving wall (20).

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