EP2149411B1 - Rotary swaging hammer - Google Patents

Abstract

The hammer (12) has a percussion surface (13) for shaping a work piece (10') at different contact points (KP, KP', KP'') of the percussion surface. The percussion surface includes a concave curve section in a normal plane of a longitudinal axis of the hammer. The curve section is varied between a crown line (26') of the percussion surface and edge regions of the surface. Each contact point exhibits a curve radius (R) defining a circle of curvature with middle points (M, M', M''). The middle points lie in a middle symmetry plane (24) extending along the axis and contain the crown line.

Description

The present invention relates to rotary swaging tools, in particular round kneading, for non-cutting forming of workpieces with ultimately rotationally symmetrical cross section.

Rotary swaging is a pressure forming process which is used to reduce the cross-section of workpieces - usually made of metal. In rotary swaging, the workpiece to be formed is reshaped by intermittent knocks of round knime hammers or pairs of hammers. In other words, radial deformation forces are applied to the workpiece by two or more hammers arranged on the circumference of the workpiece. The workpiece is acted upon by the concave face of the round kneam or the round kneam hammer. By suitable choice of the impact surface, the reduction of the cross-section can be constricted or punctured by the forming variants (see also Fig. 1a or 1b) are brought about.

Known Rundknethämmer have concave cylindrical and possibly additionally in the inlet region of the workpiece conical faces. The cross section of the striking surfaces (curvature profile) is thus in a plane perpendicular to its longitudinal axis substantially a circle segment.

As a result, in the initial state of the workpiece, that is to say at the beginning of the kneading process, such a hammer fits snugly against the workpiece. However, as the cross-sectional diameter of the workpiece decreases, the osculation of the hammer on the workpiece deteriorates. In the course of the kneading process, a large-area contact zone between the hammer and the workpiece at the beginning of the kneading process reduced. The edge areas of the hammer then no longer contribute to the loading of the workpiece with forming forces. The contact zone thus concentrates towards the end of the rotary kneading on the central region of the striking surface along the longitudinal axis of the round kneading hammer. The central area of the clubface is therefore particularly stressed and exposed to wear much more than the edge areas. The uneven wear of the face leads to a reduction in the service life of the round kneading hammer.

Another undesirable effect of the increasingly punctiform contact zone in the course of the kneading process is the occurrence of impact grooves on the workpieces.

In addition, the effect of the ovalization of the workpiece is enhanced by focusing the forming forces acting on the workpiece. By ovalization is meant an undesirable local alternating bending which occurs between the contact zones of, for example, two orthogonal pairs of hammers with each stroke. The four hammers of the two pairs of hammers hit each contact simultaneously on each contact zone. Each stroke thus produces an oval deformation of the workpiece in the respective area between two adjacent hammers. On the one hand, this does not efficiently use the forming work that is required to reduce the cross-section; on the other hand, the material of the workpiece is unnecessarily stressed, which can lead to increased pre-damage and thus to a reduction in component strength. If the workpiece is rotated by an angle step between two successive beats, all areas of the machined workpiece surface are affected by the ovalization in the course of forming. When using a forging mandrel (internal mandrel) in the production of the workpiece also suffers from the effect of ovalization.

The JP 57-165151 and the JP 2002 263 776 A each describe a Rundknethammer with the features of the preamble of claim 1.

Although described by the publications described by the embodiments of the striking surface osculation at the beginning and at the end of the kneading process. Between these two states, however, the disadvantageous effects described above can not or only insufficiently be avoided.

The invention is therefore based on the object to provide improved Rundknethämmer having over the course of a rotary swaging process on average improved osculation of the workpiece.

The solution of this object is achieved by the features of claim 1.

The roundknife hammer according to the invention therefore has a striking surface which has a concave curvature profile in a normal plane of a longitudinal axis of the hammer, the striking surface deviating from a concave cylindrical shape or conical shape. The cross-section of the face of the roundkneading hammer according to the invention can thus not be described by a circle segment, the curvature profile is not circular. In other words, the curvature of the striking surface has different radii of curvature and varies between the peak line of the striking surface and the mutual edge regions of the striking surface. This variation of the radius of curvature is provided at least in that area of the striking surface which acts on the workpiece to be machined during operation of the hammer, ie along the contact points already mentioned.

By a contact point of the striking surface is meant the point where the striking surface contacts the workpiece during a stroke. In practice, this is not a single point in the mathematical sense, but a zone (area) in which touch the face and the workpiece during a strike of Rundknethammers.

The contact point has a radius of curvature which defines a circle of curvature due to its direction and magnitude. The center of the circle of curvature lies in a plane that runs along the longitudinal axis of the hammer and contains the apex line of the clubface. In other words, the centers of the circles of curvature of the contact points are always in the said plane even with a shift of the contact points during the forming process.

The curvature profile of the face is thus designed such that during the entire forming process, the respective "active" contact points can be described by curvature circles that obey a boundary condition. This constraint is the location of the centers in the level defined above.

In rotary swaging processes using such knee hammers results in a mean improved vibration over the entire forming process, which, inter alia, less impact scoring occur. By varying the radius of curvature of the face, the point of contact - or points of contact - of the hammer "migrates" with the workpiece during swaging. Overall, therefore, the osculation, that is, the effective contact surface between the hammer and workpiece, improved. This also reduces the effect of the explained ovalization. In addition, the "rounding" of the contact zone of the roundknife hammer loads more uniformly and longer service lives of the forming tool are achieved, which leads to significant cost savings.

Thus, by means of the round-seed hammers according to the invention, it is possible to produce workpieces of higher quality more efficiently, whereby the production costs are also reduced by extending the service life of the round-seed hammers and a possibly used forging mandrel.

Advantageous embodiments of the invention are set forth in the subclaims, the description and the drawings.

According to one embodiment of the invention, the slope Y 'of a perpendicular to the respective radius of curvature in the points of contact satisfies the relation Y' = tan (arcsin (X / Ra)), where X is the distance of the contact point projected onto the tangent plane of the crest line is the peak line of the face, and Ra is the amount of the respective radius of curvature. In other words, the slope Y 'of the respective tangent of the curvature profile in the individual contact points is in each case a function of the distance X from the apex line of the striking surface. A curvature profile defined by said relation fulfills the boundary condition discussed above and leads to improved osculation of the round-kneading hammer on the workpiece to be formed during the forming process.

The advantageously improved osculation is achieved according to the invention by a variation of the parameter Ra as a function of the distance X, which defines a linear dependence. This proves to be particularly advantageous in order to achieve a spatially and temporally uniform stress on the respective face during the forming process.

Ra may also be a linear function dependent on an arc length S, where S is the length of the curvature profile between the point of contact in question and the vertex line.

Preferably, Ra can be described by the equation Ra = k * X + R0 or Ra = k * S + R0, where k is an arbitrary constant and R0 corresponds to the magnitude of the radius of curvature of the face in the crest line. This linear relationship between the distance X and the amount of the respective radius of curvature ensures a uniformly progressive deformation over the course of the entire process, which additionally contributes to the quality of the workpiece and increases the service life of the round-seed hammers. In other words, the loads occurring are distributed evenly over the entire forming process so that "load peaks" are lower.

In one embodiment of the round kneading hammer according to the invention, the curvature profile of the striking face is symmetrical to a plane of symmetry. This plane of symmetry runs along the longitudinal axis of the hammer and contains the aforementioned apex of the clubface.

In principle, however, the striking surface can also be asymmetrically shaped, in particular if the workpiece is acted upon simultaneously by four hammers arranged in a circumferentially distributed manner.

Preferably, the radius of curvature increases from the apex line of the face to the edge regions.

According to a further embodiment, the function of the radius of curvature is a continuous function in order to be able to reliably prevent the occurrence of impact notches.

The curvature profile can be selected and adjusted depending on the diameter of the workpiece, the cross-sectional reduction to be achieved and / or depending on other specific requirements of the rotary kneading process.

It is particularly advantageous here if the contact between the hammer and the workpiece at the beginning of the kneading does not take place in a central zone of the striking surface, but in two separate zones - and optionally mirror images - arranged zones of the striking surface. This applies as long as the radius of the workpiece currently being processed is greater than the smallest Hammerschmiegeradius, as it is preferably carried out on the apex line of the clubface. By these spatially favorably arranged multiple contacts the ovalization effects and the associated material stress are reduced.

As the radius of the workpiece in the machined zone is progressively reduced to the smallest possible hammer radius, the two disjointed contact zones converge on the face until they unite at the apex line into a single contact zone of the respective hammer. As a result, the contact zone is formed over a large area, in particular also in the final phase of shaping, and the formation of harmful impact notches is minimized.

The invention further relates to a rotary swaging machine with at least two round kneam hammers according to at least one of the embodiments described above.

Fig. 1a

eine Anordnung von Rundknethämmern zum Umformen (Einstechen),

Fig. 1b

eine Anordnung von Rundknethämmern zum Umformen (Einschnüren),

Fig. 2a

eine schematische Ansicht eines Rundknethammers,

Fig. 2b und 2c

eine schematische Querschnittsansicht eines Rundknet- hammers (Krümmungsprofil),

Fig. 3a bis c

den Verlauf eines Rundknetprozesses mit herkömmlichen Rundknethämmern,

Fig. 4a bis c

den Verlauf eines Rundknetprozesses mit erfindungsge- mäßen Rundknethämmern, und

Fig. 5

eine schematische Darstellung der Veränderung der geo- metrischen Verhältnisse im Laufe des Umformprozesses.

The invention is described below purely by way of example with reference to advantageous embodiments and with reference to the drawings. Show it:

Fig. 1a

an arrangement of round kneams for forming (grooving),

Fig. 1b

an arrangement of round kneam hammers for forming (constricting),

Fig. 2a

a schematic view of a Rundknethammers,

Fig. 2b and 2c

a schematic cross-sectional view of a rotary swaging hammer (curvature profile),

Fig. 3a to c

the course of a rotary swaging process with conventional round kneading,

Fig. 4a to c

the course of a rotary swaging process with round knives according to the invention, and

Fig. 5

a schematic representation of the change in the geometric conditions in the course of the forming process.

Fig. 1a schematically illustrates the piercing of a rod-shaped workpiece 10 (eg, shaft) using circular kneaders 12, 12 '. The Rundknethämmer 12, 12 '(hereinafter also referred to as hammers) are each arranged in pairs on opposite sides of the workpiece 10. In the case illustrated the Fig. 1a it is a first pair of hammers with the hammers 12 and a second pair of hammers with the hammers 12 ', wherein the representation of one of the hammers 12' was omitted in order to improve the clarity of the figure. In principle, however, a plurality of pairs of hammers may be provided.

In order to reduce the cross-section of the workpiece 10, the hammers 12, 12 'of a pair of hammers moved along hammer-moving directions 20 simultaneously exert radial compressive forces on the workpiece 10 when they strike through their concave striking surfaces 13. At high impact frequency while the workpiece 10 is simultaneously machined by the oscillating hammer pairs 12 and 12 ', wherein the workpiece 10 during the lifting of the hammers 12, 12' rotated stepwise (rotation 18) and optionally also moved in the axial direction. As a result, rotationally symmetrical workpieces can be produced.

At the in Fig. 1a illustrated example of the so-called Einstechverfahrens a local necking, for example, to produce steep transition angle 14 between the output cross-section of the workpiece 10 and the pierced cross section generated.

In Fig. 1b is analogous to Fig. 1a the constriction of a workpiece shown schematically. The face surfaces 13 of the round-seed hammers 12, 12 'used in the necking process also have, in addition to cylindrically shaped face surface sections, a conical face surface section 15, which therefore corresponds to a conical segment. As a result, comparatively flat transition angles 14 are generated. By a feed 16 of the workpiece 10 and longer sections can be produced with reduced cross section at shallow transition angles 14. Also in this method, a rotation 18 of the workpiece 10 is provided about its own axis, while the pairs of hammer 12, 12 ', the workpiece 10 to transform incrementally.

Fig. 2a shows a schematic view of a Rundknethammers 12. As described above, the hammer 12 has a striking surface 13, which serves to machine the workpiece 10. Furthermore, the hammer 12 comprises a hammer end face 22, which also corresponds to the cross section of the hammer 12 perpendicular to its longitudinal axis. The hammer 12 is symmetrical about a mid-symmetry plane 24 that extends along the longitudinal axis of the hammer 12 and is perpendicular to the hammer face 22. The mid-symmetry plane 24 also contains the apex line 26 of the striking surface 13. On both sides of the striking surface 13 are inclined surfaces 27. The bevel can not be minimized during a strike by the striking surfaces 13 of the hammers 12, 12 'areas of the workpiece surface.

Fig. 2b shows a cross section through the hammer 12 in a plane parallel to the hammer face 22. The striking surface 13 has a concave curvature profile 28, 28 'on. The curvature profile 28 of conventional hammers 12 is a circle segment. In other words, the radius of curvature of all sections of the curvature profile 28 of the face 13 is substantially equal.

In contrast, the curvature profile 28 '(dashed line) of a hammer 12 according to the invention has a variable radius of curvature which varies between the apex line 26' of the hammer 12 according to the invention and the two edge regions 30 of the striking surface 13 adjacent to the inclined surfaces 27. The profile 28 'is therefore not circular.

In the illustrated embodiment of the hammer 12 according to the invention with the curvature profile 28 ', this is formed symmetrically to the central symmetry plane 24. The curvature decreases starting from the apex line 26 'of the striking surface 13 toward the edge regions 30 (ie the radius of curvature increases).

The curve profile 28 'is also free of cracks, edges or similar discontinuities parallel to the apex line 26' to obtain a uniformly machined surface of the workpiece 10.

Fig. 2c illustrates the geometric relationships of the curvature profile 28 'of a round knotter 12 according to the invention. The radius of curvature R of a point P on the face 13 depends on a distance X. The distance X is the distance of the respective point P from the apex line 26 'projected onto a tangential plane 32 at the apex line 26' of the curvature profile 28 '. The function can also be done by the X off. The distance X is the distance of the respective point P from the apex line 26 'projected onto a tangential plane 32 at the apex line 26' of the curvature profile 28 '. However, the function may also depend on the arc length S of the curvature profile between the apex line 26 'and the point P of the curvature profile.

The curvature profile 28 'is designed such that the amount Ra of the radius of curvature R depends linearly on X and can be described by the equation Ra (X) = k * X + RO. k is an arbitrary constant that indicates how "fast" the radius of curvature should vary. The parameter RO indicates how large the radius of curvature R in the crest line 26 'is (X = 0). As a rule, RO is selected according to the desired radius of the workpiece 10 at the end of the forming process.

In other words, Ra increases with increasing angles α between the radius of curvature R to be considered as vector and the center symmetry plane 24. Each point P on the curvature profile 28 'is thus assigned its own circle of curvature whose radius has the amount Ra (X) (Ra = | R |). The center M of the circle of curvature lies on the mid-symmetry plane 24. Since the radius R must be perpendicular to a tangent Y 'on the curvature profile 28' of the face 13, the center M moves away from the apex line 26 'with increasing distance X, as will be seen below based on Fig. 5 will be explained in detail.

The Fig. 3a to 3c illustrate the course of a rotary swaging process of a workpiece 10 with conventional hammers 12 Fig. 4a to 4c the effect of a hammer 12 according to the invention with a curvature profile 28 'deviating from a circle segment is subsequently clarified. With the progress of the forming of the workpiece 10 Blacksmith mandrel can be arranged. For the sake of clarity, in the Fig. 3a to 3c and 4a to 4c only one hammer represented and also an optionally existing forging mandrel not shown.

The hammer 12 points in the Fig. 3a to 3c a circular segment-shaped curvature profile 28. At the beginning of forming ( Fig. 3a ), the hammer 12 nestles over a large area against the surface of the workpiece 10. A (single) contact zone 34, that is to say the contact surface between the hammer 12 and the tool 10 during impact of the hammer 12, essentially covers the entire striking surface 13. As the process progresses, the contact zone 34 becomes continuously smaller (FIG. Fig. 3b ), and in the edge regions 30 of the striking surface 13, the striking surface 13 and the workpiece 10 'no longer touch. Towards the end of the forming process, this reduction of the contact zone 34 is even more pronounced, and the contact zone 34 comprises only a small part of the striking surface 13 in the region around the crest line 26.

It can be clearly seen that the area around the crest line 26 is always loaded and therefore particularly stressed. Due to the very small contact zone 34 in Fig. 3c In addition, impact grooves and thus damage to the workpiece 10 "can arise Fig. 3c The effect of ovalisation is particularly pronounced. In other words, the workpiece 10 "reacts to a hammer movement 20 by a deformation outside the contact zone 34 of the respective hammer 12, 12 '.This deformation direction is symbolized by the arrows V. In subsequent impacts of the hammer pairs 12, 12', the workpiece 10" this ovalization in each case at a further rotated by an angular step position. In the lateral areas or columns outside the respective contact zone 34 of the hammer pairs 12, 12 ', in particular between adjacent hammers 12, 12', the workpiece 10 'a damaging alternating bending (ovalization) is exposed.

When using a Rundknethammers 12 according to the invention with a curvature profile 28 ', which differs from a circular curvature profile 28, are in the Fig. 4a to 4c conditions shown before. Analogous to the Fig. 3a to 3c the course of a rotary swaging process is shown.

Due to the varying curvature profile 28 ', the contact zone 34 is limited at the beginning of the process to the edge regions 30 of the impact surface 13, ie there are two separate contact zones 34 ( Fig. 4a ). In the further course of the forming process, the contact zones 34 "wander" in the direction of the apex line 26 'of the striking surface 13 (FIG. Fig. 4b ). Towards the end of the forming, the contact zone 34 extends essentially in the region of the apex line 26 '(FIG. Fig. 4c ). The contact zone 34 of Fig. 4c However, includes a significantly larger area than the corresponding contact zone 34 of Fig. 3c , Thus, there are less punctual forces in a round knob hammer 12 according to the invention than in conventional round kneading 12. In this way, notching and damage can be avoided by ovalizing. At the same time, the service life of the hammer 12 according to the invention is extended compared to conventional hammers 12, since the striking surface 13 is stressed more uniformly. When using a forging mandrel, the use of a hammer 12 according to the invention also has a positive effect, since overmolding is prevented or the wall thickness of the initial geometry can be reduced.

When using round kneam hammers 12 with a curvature profile 28 'according to the invention, a complete nestling of the striking surface 13 of the hammer 12 on the workpiece 10 at the beginning of the rotary kneading process is deliberately avoided. In the course of rotary kneading, however, the roundknife hammer 12 according to the invention results in improved forming conditions compared with conventional hammers 12.

Fig. 5 illustrates the changes in the geometric conditions in the course of the forming process. Shown is only a part of a Rundknethammers 12 which is symmetrical to the Mittenymmetrieebene 24 is formed. Furthermore, a section of a workpiece 10 'is shown, which has already undergone a transformation - here a cross-sectional reduction. When a blow of Rundknethammers 12 on the workpiece 10 'they are in contact point KP in contact. In practice, the contact is not limited to one point but comprises a zone that extends around the contact point KP (often symmetrically) (contact zone 34, in FIG Fig. 5 shown disproportionately for clarity). As already from the Fig. 4a to 4c can be seen, lies another - in Fig. 5 not shown - contact point between the workpiece 10 'and the striking surface 13 of the round kneading cylinder 12 before, which is arranged symmetrically to the plane of symmetry 24.

In the course of a forming process, the contact points move from outside to inside (KP ', KP, KP "), thereby reducing the workpiece radius R. At each time of the forming process, the radius of curvature R of the striking surface 13 is in the" active "contact point KP That is, the center Mw of the workpiece 10 'and the center M of the circle of curvature (defined by the radius of curvature R of the face 13) coincide.

In the contact point KP ', which was "active" in an earlier stage of the forming process, the ratios are in relation to the in Fig. 5 different point of time: the radius of curvature R of the face 13 is greater here than that of FIG Fig. 5 currently "active" point of contact KP. The center point M 'of the circle of curvature associated with the contact point KP' no longer coincides with the workpiece center point Mw in an advanced forming process. The (perpendicular to the workpiece surface) workpiece radius R 'is in the illustrated state according to Fig. 5 thus in the meantime smaller than the radius of curvature R at the contact point KP ', which came into contact with the workpiece 10' in the earlier phase of deformation, namely when the workpiece radius R 'still corresponded to the radius of curvature R of the striking surface 13 at the contact point KP'.

At the contact point KP ", in which the striking surface 13 will come into contact with the workpiece 10 'only in a further advanced forming of the workpiece 10, the conditions are reversed as in the contact point KP': The radius of curvature R of the contact point KP" is smaller as the in Fig. 5 shown current workpiece radius R '. The center M "of the circle of curvature associated with the contact point KP" is therefore closer to the apex line 26 'than the center of the workpiece Mw.

Thus, all centers M, M ', M "of the bending surface 13 describing arcs of curvature lie in the Mittenymmetrieebene 24. In the course of forming the workpiece center point Mw moves due to the reduction in cross-section of the workpiece 10' towards the apex line 26 'of the striking surface 13. Preferably, the The radius of curvature R of the face 13 in the apex line 26 'is equal to the workpiece radius R' to be achieved. It can be seen from the above geometric considerations that the center points M, M ', M "and Mw do not leave the middle symmetry plane 24 during the forming.

Simulation calculations have shown that by choosing a linear variation of the amount Ra of the radii of curvature R of the contact points KP, KP 'and KP "as a function of the distance X (distance of the projected into the tangent plane 32' contact points KP", KP, KP 'of the Crest line 26 '; Fig. 2c ) a uniform deformation of the workpiece is ensured. The design of the impact surface 13 not only leads to a reduction in the loads of both the round kneam twisters 12 used and the workpiece 10 ', but also reduces the required forming work to achieve a desired workpiece deformation.

LIST OF REFERENCE NUMBERS

10, 10 ', 10 "

workpiece

12, 12 '

Rundknethammer

13

Playing surface

14

Transition angle

15

Face portion

16

feed

18

rotation

20

Hammer moving direction

22

Hammer front side

24

Mid-plane of symmetry

26, 26 '

crest line

27

sloping surface

28, 28 '

curvature profile

30

border area

32, 32 '

tangent

34

contact zone

M, M ', M "

Curvature circle center

mw

Workpiece center

P

Point

KP, KP ', KP "

contact point

R

radius of curvature

Ra

Amount of the radius of curvature

R '

Workpiece radius

S

arc length

V

deformation

α

angle

Y '

tangent

Claims (7)

1. A swaging hammer having an impact surface for forming a work piece at different contact points of the impact surface, wherein the impact surface (13) has a concave curvature profile in a normal plane of a longitudinal axis of the hammer which varies between an apex line (26') of the impact surface (13) and mutual boundary regions (30) of the impact surface (13), wherein each contact point (KP, KP', KP") of the impact surface (13) has a radius of curvature (R) which defines a circle of curvature having a circle of curvature center (M, M', M"), wherein the circle of curvature center (M, M', M") of the contact points (KP, KP', KP") of the impact surface (13) lie in a plane (24) which runs along the longitudinal axis of the hammer (12, 12') and which includes the apex line (26') of the impact surface (13),
   characterized in that
   the amount Ra of the respective radius of curvature (R, R') is a linear function depending on the distance X or on an arc length S, wherein X is the distance of the related contact point from the apex line (26') of the impact surface (13) projected onto the tangential plane (32) of the apex line (26') and S is the length of the curvature profile between the related contact point (KP, KP', KP") and the apex line (26').
2. A swaging hammer in accordance with claim 1,
   characterized in that
   the gradient Y' of a perpendicular to the respective radii of curvature (R) in the contact points (KP, KP', KP") obeys the relation $$\mathrm{Yʹ}\mathrm{=}\tan \left(\arcsin \left(\mathrm{X}\mathrm{/}\mathrm{Ra}\right)\right)\mathrm{.}$$

   
3. A swaging hammer in accordance with claim 1 or claim 2, characterized in that
   Ra can be described by the equation Ra = k*X+RO or
   Ra = k*S+RO, wherein k is an arbitrary constant and RO is the value of the radius of curvature (R) of the impact surface (13) in the apex line (26').
4. A swaging hammer in accordance with at least one of the preceding claims,
   characterized in that
   the curvature profile (28') of the impact surface (13) is symmetrical to a central symmetry plane (24) which runs along the longitudinal axis of the hammer (12, 12') and which includes the apex line (26').
5. A swaging hammer in accordance with at least one of the preceding claims,
   characterized in that
   the radius of curvature (R) increases starting from the apex line (26') of the impact surface (13) towards the boundary regions (30).
6. A swaging hammer in accordance with at least one of the preceding claims,
   characterized in that
   the radius of curvature (R) varies in accordance with a constant function.
7. A swaging machine having at least two swaging hammers in accordance with at least one of the preceding claims and having a drive unit for the oscillated drive of the swaging hammers.

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