Claims
- 1. The process of forming helical grooves in the wall of revolution of a tubular body (2) without removal of the material from which said body is made, these helical grooves forming threads for screw threaded assemblies, comprising the steps of:
- (1) supporting said tubular body (2) for rotation around its own axis (X1);
- (2) mounting at least one profiling tool of revolution, freely rotatable, around an axis perpendicular to a radius of said tube;
- (3) moving said tool axis in parallel with itself along a determined closed curve (12, 22), the enveloping curve (14, 23) of the path of the edge of the profiling tool including a portion effecting cyclical engagement of said tool and said wall and wherein the diameter of said tool is greater than the length of a diagonal (DE) of the determined closed curve (22) of which the extension cuts the region of engagement (25) as well as the axis (X5) of the tubular body, the length of that diagonal (DE) being at least equal to the deepness of penetration (e1) of the edge of the profiling tool within the wall (20);
- (4) applying sufficient pressure to said profiling tool against said tubular body to form a continuous complementary profile on the wall of said tubular body, the displacement without removal of said body material in at least one profiling step; and
- (5) rotating said tubular body and moving cyclically the axis of the profiling tool along the determined closed curve while longitudinally displacing said tube and said tool relative to each other to form a helical groove over a predetermined area of said tubular body.
- 2. The process of forming helical grooves in the wall of revolution of a tubular body without removal of the material from which said body is made, these helical grooves forming threads for screw-threaded assemblies, comprising the steps of:
- (1) supporting said tubular body for rotation around an axis;
- (2) mounting at least one profiling tool of revolution freely rotatable around an axis;
- (3) moving said tool axis in parallel with itself so that its point of intersection with a perpendicular plane follows in cyclic manner a determined closed curve, the enveloping curve of the path of the edge of the profiling tool including a portion effecting cyclical engagement of said tool and said wall, the axis of said tool being in a plane substantially parallel to the plane tangential to the generating line of the wall of the tubular body passing through the region of engagement and wherein the diameter of said tool is greater than the length of a diagonal of the determined closed curve of which the extension cuts the region of engagement as well as the axis of the tubular body, the length of that diagonal being at least equal to the deepness of penetration of the edge of the profiling tool within the wall;
- (4) applying sufficient pressure to said profiling tool against said tubular body to form a continuous complementary profile on the wall of said tubular body, by displacement without removal of said body material in at least one profiling step; and
- (5) rotating said tubular body and moving cyclically the axis of the profiling tool along the determined closed curve while longitudinally displacing said tube and said tool relative to each other to form a helical groove over a predetermined area of said tubular body.
- 3. A process according to claim 1 or 2 wherein the plane of the enveloping curve is preferably orientated such that it is parallel to a tangent to the helical groove in the region of engagement.
- 4. A process according to claim 1 or 2 wherein the determined closed curve (12) is circular.
- 5. A process according to claim 1 or 2 wherein the determined closed curve (22) has an elongate shape and is orientated in such a way that a diagonal of this curve (E-D) of which the extension cuts the region of engagement (25) and also cuts the axis (X.sub.5) of the wall of the tubular body and is substantially perpendicular to the longest diagonal (BC) of this determined closed curve.
- 6. A process according to claim 1 or 2 wherein the plane of the enveloping curve of the path of the profiling tool (61, 62) is adjustable about an axis (X.sub.25) contained in this plane which intersects both the region of engagement and the axis X.sub.22 of the wall of revolution of the hollow body.
- 7. A process according to claim 1 or 2 wherein the plane of the enveloping curve is positioned parallel to a tangent to the helical groove (31) being produced in the region of engagement.
- 8. A process according to claim 1 and 2, wherein a plurality of profiling tools are employed, the enveloping curves of the path of the edge of each profiling tool being positioned around the wall of the tubular body in such a way that each of them has a different region of engagement with this wall.
- 9. A process according to claim 1 or 2, wherein a helical groove is produced on a non-cylindrical wall (34) of revolution of a hollow tubular body, and wherein the distance between the axis of said wall and at least one enveloping curve corresponding to the path of the edge of a profiling tool (36) is varied to control the depth of the region of engagement between said tool and said tubular body.
- 10. A process according to claim 1 or 2, wherein, for an observer placed in the extension of the axis of the wall of the tubular body, the direction of rotation (F1, F6) of said 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 tool are the same.
- 11. A process according to claim 1 or 2 wherein a smoothing tool includes an axis maintained at a substantially constant distance from the wall of said tubular body and in a groove previously formed upstream of this smoothing tool.
- 12. A device for forming grooves on the wall of revolution of a tubular body, composed of a ductile or plastic material without removal of matter, comprising a first driving support means including gripping means for said tubular body grasping said body in such a way that the axis of the body coincides with the axis of rotation of the support, and wherein at least one rigid profiling tool holder (42, 67) mounts a single profiling tool (41, 65), of revolution, freely rotatable on an axis (X.sub.16, X.sub.23) integral with said tool holder, and a second driving means (43, X.sub.24) moves said tool holder cyclically to move said tool axis in parallel with itself, wherein its point of intersection with a perpendicular plane defines, in cyclic manner, a determined closed curve (46), adjustment means (44, 71) permitting the adjustment of the distance between the tool holder and the wall of said tubular body to be varied wherein the enveloping curve of the cyclic path of at least one edge of a profiling tool defines a region of engagement with the wall of said tubular body.
- 13. A device according to claim 12 wherein the tool (41) includes at least one edge having a diameter greater than the length of a diagonal of the determined closed curve (46) of which the extension cuts the region of engagement (48) as well as the axis (X.sub.15) of the wall of the tubular body.
- 14. A device according to claim 12, wherein the determined closed curve followed cyclically by the axis (X.sub.23) of a profiling tool (65) is a circumference.
- 15. A device according to claim 12 wherein translation means moves the hollow body (59) along its axis (X.sub.22) in a relative manner with respect to said tool and in synchronization with its movement about the same axis (X.sub.22) to form a helical groove in said tubular body.
- 16. A device according to claim 12 wherein the determined closed curve (46) is non-circular and is orientated relative to the wall of said tubular body so that its greatest diagonal is substantially perpendicular to a diagonal of which the extension cuts the region of engagement as well as the axis of the wall of said tubular body.
- 17. A device according to claim 12 wherein at least one tool holder (67) is adjustable about an axis (X.sub.25) located in the plane of the enveloping curve of the path of at least one tool which corresponds to said tool holder, said axis cutting both the region of intersection and the axis X.sub.22 of the wall of said tubular body.
- 18. A device according to claim 17 wherein a plurality of profiling tools (26, 27, 28, 29) engage a common groove each to a different depth.
- 19. A device according to claim 12 wherein a driving means (79) drives at least one tool holder in the direction of the axis (X.sub.25) of the wall of said tubular body (60) as a function of the relative translation of said wall along said axis relative to said tool holder.
- 20. A device according to claim 12 wherein a plurality of tool holders each equipped with a single tool (61, 62) are distributed around the axis of said tubular body.
- 21. A device according to claim 34 wherein at least one profiling tool (26, 27, 28, 29) includes a plurality of shaping edges (A1-B1), A2-B2, A3-B3, A4-B4).
- 22. A device according to claim 12 wherein at least one tool holder is equipped with a smoothing roller, the axis of which does not perform cyclic movement, the device further comprising at least one tool holder equipped with a profiling tool configured to form a groove within which said smoothing roller rolls continuously.
Priority Claims (1)
| Number |
Date |
Country |
Kind |
| 85 01330 |
Jan 1985 |
FRX |
|
Parent Case Info
This is a continuation of co-pending application Ser. No. 919,147 filed on Sept. 23, 1986, now abandoned.
The process and the device forming the subject of the invention relate to the production of grooves on the wall of revolution of a hollow body without removal of matter.
They relate more particularly to the production of grooves in the form of helical threads on the wall of revolution of tubes composed of ductile materials such as metals or alloys.
This device comprises a knurling tool 1 mounted freely rotatably on an axis X.sub.0 which rolls continuously on the external wall of the tube 2 which is rotated about its axis X.sub.1. The axis X.sub.0 is perpendicular to the radius 3 of the tube 2 passing through the region of intersection 4 between the edge 5 of the knurling tool 1 and the wall of the tube 2. This axis X.sub.0 is inclined by an angle .alpha.1 to a straight secant parallel to the axis X.sub.1. It is thus possible to produce a helical thread 6 on the wall of revolution of the tube 2 by a relative translation movement of this tube 2 along its axis X.sub.1 relative to the knurling tool 1 combined with its rotational movement about this same axis.
The desired depth of the thread 6 is obtained by exerting on the knurling tool 1 sufficient pressure to enable its edge 5 to penetrate to the desired depth into the wall of the tube 2. This pressure depends on the dimensions of the tube 2 and of the knurling tool 1 and on the depth of the thread 6 to be produced. In the case of tubes of which the wall thickness is relatively small it is observed that, instead of achieving displacement of material limited to the zone of intersection 4 and to its immediate vicinity, deformation of the entire tube which may be elastic or even permanent and which renders the process inapplicable is produced.
To reduce the pressure exerted locally on the tube, it is possible to use several knurling wheels which roll continuously on the tube while following the same groove or helical thread and are also distributed round the periphery of the tube. By exerting a relatively limited pressure on each of these knurling tools by means of its shaft, it is possible to form a groove or thread having a depth greater than that which could be produced by applying the same pressure to a single knurling tool without significant deformation of the tube wall. The furrow dug by the first knurling tool is deepened during the passage of each of the following knurling tools. Furthermore, the distribution of the knurling tools about the tube allows the stresses to be balanced.
However, in a large number of cases, such a process cannot be applied because the tubes are too thin to tolerate the pressure of the knurling tools without significant deformation.
The use of an internal mandrel does not permit the problem to be solved either because swelling of the tube which alters its dimensions and, in particular, those of the thread or of the groove to be produced is observed.
French Patent No. 1 551 913 describes a process for forming metal articles from billets or blanks (page 1, right-hand column, lines 1-10) which involves turning a row of small continuously working rollers one after the other over an orbit, mounting a blank so that its surface region intersects the orbit and is in turn struck by the rollers in uninterrupted succession so that the metal of the surface region is subjected to a plastic deformation while matching the contour of the rollers. It is essential that these rollers are held by support rollers or members which are stationary in their region of action. FIGS. 1 to 4 of this patent show a cylindrical blank about which a helical groove is formed by means of small rollers 12 mounted rotatably about axes, these axes being distributed over the periphery of a circular rotating cage 10. These rollers are held by a central roller 16 against which they rest. As shown in FIG. 2, use can also be made of a cage which is articulated in the form of a chain 10 provided with rollers 22 which travels in a closed circuit along an elliptical orbit while resting on a central support 20 on which the rollers 22 rest. The working rollers 12 are also connected to the chain and rest on the rollers 22. The chain is driven by a suitable mechanism. Rectilinear grooves may also be produced over a certain length, as shown in FIG. 2 in which the central support comprises two rectilinear large faces connected by small rounded sides. Toothing may also be formed on the periphery of a wheel. Although the document only describes the forming of solid parts, the possibility of also forming hollow blanks is mentioned without further details.
Tests have shown that it is possible to use small forming rollers similar to those just described for forming annular or helical grooves on the cylindrical wall of revolution of hollow bodies such as tubes by mounting these rollers on at least one rotating cage which rotates them about its axis. These rollers successively strike the wall of the hollow body which is itself rotated about its axis. An annular groove is thus produced. A helical groove is obtained by simultaneously moving the hollow body along its axis. French patent application No. 8501330, on whose priority the present application is based, describes such a method of producing grooves on a hollow body wall.
It has however been found during tests that the use of a row of small working rollers or knurling tools according to the teaching of French Pat. No. 1551913 and having a small diameter relative to the dimensions of the orbit or closed path along which they travel has serious drawbacks. In fact, if the small diameter of the rollers reduces the strain exerted on the wall of the hollow body, it harms the precision of the grooves and the flanks thereof. It is also found that the circular path covered by knurling tools having small dimenions relative to the diameter of this path, such as those shown in FIG. 6 of the priority application, has the drawback of causing a succession of impacts exerted by each knurling tool at the moment when it comes into contact with the wall of the hollow body. These impacts create local defects and, in particular, wrenching and folds which it is impossible to eliminate or attenuate in many cases. These also cause vibrations which also damage the quality and precision of the profile of the grooves produced.
Tests have shown, in particular, that the process and the device described in French Pat. No. 1 551 913 do not allow helical grooves or threads to be produced on the wall of revolution of a hollow body, of a quality which is good enough to allow assembly under perfect conditions of tubes which are threaded in this way at their ends.
These tests have also shown that it is not possible to produce such grooves or such threads on non-cylindrical walls of revolution of hollow bodies.
The possibility has been investigated of developing a process and a device for carrying out the process which allow annular or helical grooves of high precision which are free from local defects to be produced. The possibility of producing such grooves in the walls of relatively thin hollow bodies without significant deformation outside the region in the immediate vicinity of the groove has also been investigated. Finally, the possibility has been investigated of developing a process for producing such grooves or such threads on the wall of revolution of hollow bodies of non-cylindrical shape so as to allow the process to be adapted, in particular, to the production of helical threads on the conical ends of tubes with the object of obtaining screw-threaded assemblies with conical threads of satisfactory quality.
The process and the device according to the invention allow these problems to be solved in a particularly effective manner.
The process according to the invention involves forming, without removing material, at least one groove on the wall of revolution of a hollow body constituted by a ductile or plastic material. In this process, at least one revolving knurling tool comprising at least one shaping edge and mounted freely rotatably on an axis is used. This axis moves in parallel with itself so that its point of intersection with a perpendicular plane follows in cyclic manner a path reserved for it along a determined closed curve, said path not being followed by another knurling tool. The enveloping curve of the path of at least one shaping edge of the knurling tool comprises a region of intersection with the wall of revolution, this region moving in relative manner about this wall.
The knurling tool comprises at least one shaping edge of which the greatest diameter is greater than the length of the diagonal of the determined closed curve of which the extension cuts the region of intersection in its centre as well as the axis of the hollow body. If the determined closed curve is a circumference, the diameter thereof is therefore smaller than that of the knurling tool. The determined closed curve advantageously has an elongated shape. It is preferably orientated such that the diagonal of this curve of which the extension cuts the region of intersection in its centre as well as the axis of the wall of revolution of the hollow body is substantially perpendicular to the longest diagonal of this predetermined closed curve.
A helical groove is produced on the wall of revolution of the hollow body by a relative translation movement of this wall of revolution along its axis relative to the zone of intersection combined with the movement of rotation of said wall.
The plane of the enveloping curve of the path of the shaping edge of the knurling tool may advantageously be orientated about an axis contained in this plane and intersecting both the axis of the wall of revolution and the region of intersection.
When a helical groove is formed, the plane of the enveloping curve is preferably orientated such that it is parallel to a tangent to the helical groove in the region of intersection during production.
Several knurling tools distributed round the axis of the wall of revolution of the hollow body such that the enveloping curves of their shaping edges offer with the wall of revolution different regions of intersection which are distributed round this wall of revolution are advantageously used. When at least two knurling tools are used for producing the same groove in a wall of revolution, the enveloping curves of their shaping edges also advantageously have different depths of penetration in their regions of intersection with this wall.
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 enveloping curve corresponding to the path of the shaping edge of a knurling tool is varied so as to control the depth of the zone of intersection.
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 the passage through a closed curve determined by the axis of the corresponding knurling tool are preferably the same.
It is advantageous to use, in combination with at least one shaping knurling tool, a smoothing knurling tool of which the axis is kept at a substantially constant distance from the wall of revolution and of which the edge rolls in a groove already formed by the shaping knurling tool while continuously exerting a pressure on the base and on the lateral walls of this groove.
The process according to the invention is applied in particular to the production of grooves in the form of helical threads, on the end wall of cylindrical or conical metal tubes so as to produce high quality screwed assemblies, for example by means of female screw-threaded connections.
The invention also relates to a device for forming grooves without removal of material in the wall of revolution of a hollow body composed of a ductile or plastic material by means of at least one revolving knurling tool which is mounted freely rotatably on an axis and is provided with at least one shaping edge. This device comprises a support which rotates round an axis, is connected to a first means of rotation and is provided with gripping means allowing a hollow body comprising a wall of revolution to be grasped such that the axis of this wall coincides with the axis of rotation of the support. This device also comprises at least one rigid knurling tool holder on which there is mounted a single knurling tool which is freely rotatable on an axis integral with this knurling tool holder. A second driving means moves this knurling tool holder in cyclic manner so that the knurling tool axis moves in parallel with itself and its point of intersection with a perpendicular plane passes in cyclic manner through a determined closed curve, a control means for varying the distance between the knurling tool holder and wall of revolution such that the enveloping curve of cyclic movement of at least one forming edge of the knurling tool comprises a region of intersection with this wall of revolution.
The knurling tool comprises at least one shaping edge of which the largest diameter is greater than the length of a diagonal of the determined closed curve of which the extension intersects the zone of intersection in its centre as well as the axis of the wall of revolution of the hollow body.
The device advantageously comprises a third driving means which allows relative translation of the wall of revolution of the hollow body along its axis relative to at least one shaping knurling tool mounted on the corresponding knurling tool holder.
At least one knurling tool holder can advantageously be orientated about an axis which is located in the plane of the enveloping curve of the single knurling tool path corresponding to this knurling tool holder. This axis intersects both the axis of the wall of revolution and the region of intersection between this wall of revolution and this enveloping curve.
The movement of the knurling tool holder is advantageously produced such that the predetermined closed curve has an elongated shape. It is thus preferably orientated such that a diagonal situated in its plane, of which the extension cuts the zone of intersection in its centre as well as the axis of the wall of revolution of the hollow body, is substantially perpendicular to the longest diagonal of the predetermined closed curve.
The device advantageously comprises a fourth driving means which allows at least one knurling tool holder to be moved 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 knurling tool holder.
The device preferably comprises several knurling tool holders each equipped with a single shaping knurling tool distributed about the axis of the wall of revolution.
The device advantageously comprises at least one knurling tool which comprises several shaping edges.
It is also advantageous if the device comprises at least one knurling tool holder equipped with a smoothing knurling tool of which the axis does not perform cyclic movement. This knurling tool holder comprises a means of adjustment which allows the edge of the smoothing knurling tool to rest against the wall of a groove already formed on the wall of revolution of the hollow body.
Some advantageous embodiments of the process and of the device according to the invention are described below in a non-limiting manner. IN THE DRAWINGS:
FIG. 1 is a perspective view of a known device for forming a helical groove with a rolling tool.
FIG. 2 is a schematic sectional view of a first embodiment of the invention.
FIG. 3 is a schematic sectional view of a second embodiment of the invention.
FIG. 4 is a partial sectional view of a set of knurling tools having two shaping edges according to the invention.
FIG. 5 is a schematic view of the shaping of a helical thread on the cylindrical wall of revolution of a hollow body by means of a knurling tool by the process according to the invention.
FIG. 6 is a schematic view of the shaping of a helical thread on the conical wall of revolution of a hollow body by the process according to the invention.
FIG. 7 is a view of an embodiment of the device according to the invention in which the knurling tool axis follows a path along a non-circular determined closed curve.
FIG. 8 is a view of a further embodiment of the device according to the invention comprising orientatable knurling tool holders.
FIG. 9 is a detail of a knurling tool from FIG. 8.
US Referenced Citations (3)
Foreign Referenced Citations (3)
| Number |
Date |
Country |
| 1306295 |
Sep 1962 |
FRX |
| 1551913 |
Nov 1968 |
FRX |
| 808865 |
Feb 1959 |
GBX |
Continuations (1)
|
Number |
Date |
Country |
| Parent |
919147 |
Sep 1986 |
|
Patent Grant
4838066
