EP0099874B1 - Drawing die - Google Patents

Description

The present invention relates to a drawing tool, the drawing die or drawing core can be removed in a simple manner from the holder carrying it and used to absorb the forces occurring during the drawing process, or can be inserted or reinserted into it, but in the ready-to-use state and during the drawing process an absolutely firm and stable position of the drawing core is guaranteed in the socket without separate attachment.

With such drawing tools, for example, obtained by rolling, primary materials to rods, tubes, profiles, wires, fine wires and the like. Like. pulled and "reduced".

Areas of application and dimensions of drawing tools and their parameters and designations can be found, for example, in Ö-Norm N 4450, parts 1 and 2. There are ISO recommendations for drawing tools and manufacturers also bring tools corresponding to the standards and recommendations onto the market.

It should be mentioned briefly that drawing tools for a long time have been known which have a drawing core made of hard metal or diamond, which is used in a non-detachable manner with steel or brass, for example by hot drawing or extrusion. Grasping the drawing core requires high precision.

The jacket, which is permanently attached to the drawing die, protects the core against the forces that occur during drawing. After repeated drilling or after a break in the core, the socket is usually damaged and must be removed. One used several times. Socket can only be achieved by mechanical separation of core and core socket.

A non-releasable connection of the drawing core and its socket is particularly disruptive when a core provided with a wear-resistant coating is to be regenerated by renewed coating after wear. The socket was irreversibly damaged at the high temperatures during the application of the hard material layer. This also applies to the fastening of the drawing core in an inner frame described in US Pat. No. 3,918,288, heating of an inner frame having a shoulder on both sides for holding the core and divided into two sectors, and after shrinking the core then a complete contraction of the two sectors takes place with previously heated bolts. The radius of the recess of the inner frame is smaller than that of the drawing core when not heated. Another disadvantage of this tool is that its disassembly requires the solution of the axial shrinkage by heating the inner frame, whereby the heating and subsequent cooling as well as the introduction of the heated tension bolts in addition to the resulting material stress, which can lead to a loss of strength, practically warp the inner frame is inevitable. In addition, the manipulation effort is high.

As has already been stated above, there has been a desire for some time to make the drawing die and socket as simple as possible, separable from one another. For this, e.g. proposed to insert the hard metal core in an externally conical clamping sleeve provided with a groove-like longitudinal slot, which is clamped in an internally conical holding socket. Furthermore, it was proposed to give the core a conical outer jacket and to insert it without an intermediate ring into a socket with a corresponding inner cone, with the axially directed drawing pressure in each case holding the core in the socket. This embodiment requires precisely machined, that is, expensive, parts, but the drawing pressure after reaching the yield point is not sufficient to give the hard metal core the pretension necessary for continuous use in order to prevent the core from working and stretching.

From AT-B-329 007 a drawing tool with a core releasably inserted in a socket is known, which has an inner core part with sheathing, the core having several individually interchangeable parts, which are held in a version corresponding to their external dimensions by means of a pressure ring are. In particular, it is provided there that the casing is shrink-fitted onto the drawing die so that it must be replaced with it after wear.

In the case of the drawing tool described in AT-B-354 391 with a one-piece drawing core and a multi-part holder holding the core, the core is clamped between two disc-shaped holder parts which are clamped together by means of screws in the direction of drawing under a given clamping force. The core, together with its holder, can be pivoted in an outer holder. This tool makes it possible to remove the core after wear, to reinsert it after regeneration or to replace it with a new one. Disadvantages are the relatively complex manipulations when changing and the latent risk of evenly clamping the core between the two disc parts of the frame.

A holder of the drawing die with only one gap passing through the clamping sleeve body and circumferentially a plurality of longitudinally extending, groove-like clamping collets, which is arranged braced by means of a pressure screw in a conical recess of an outer holder, is known from DE-A-29 51 056 . A column in several parallel to the tool axis Sectors split adapter sleeve for the drawing core according to US-A 2 028 652 forms a cylindrical recess for the drawing core in the installed state and has a projection or projections in the direction of drawing for supporting the core. The sleeve parts have conical outer surfaces, are inserted in a conical recess in an outer socket and are held in the outer socket by means of screws. From AT-B-206 390 a drawing tool with a cylindrical outer jacket having a drawing core, which is releasably inserted in a cylindrical inner socket with conical outer surfaces, which has a shoulder-like projection in the pulling direction and runs in the direction of the axis, is known, the inner socket in a conical recess of an outer socket is arranged. There is also a discussion of the possibility of forming the inner frame in two or more parts. With this, as with all detachable versions, which have cylindrical recesses for the drawing die, the radius of the version is precisely matched to the radius of the drawing die. If, for example, the drawing die has to be re-coated after wear, the layer applied on its jacket, the radius of which increases, must be worked off. In addition, a high-strength, precise fit of the drawing core in the socket is not fully guaranteed.

Starting from AT-B-206 390, the invention has set itself the task of creating a drawing tool with a drawing core releasably inserted in its socket, in which the manipulations required when removing or inserting the core are small and in terms of positional stability and also mechanical strength optimal fit of the drawing core in the version holding it directly, and this core version in turn is fully guaranteed in an outer version serving the stability of the entire drawing tool, the tool against fluctuations in the dimension of the drawing core, for example by the above-mentioned re-coating, should be as little sensitive as possible.

The invention thus relates to a drawing tool with a drawing core which has the pulling, preferably one-piece, for example cylindrical outer jacket, which has a shoulder-like projection in a, preferably multi-axis symmetrical, essentially limited by tool-axis-parallel generators and a shoulder-like projection in the direction of Axial column in two or more sectors divided inner frame with substantially conical outer surfaces is releasably inserted, the inner frame is in turn arranged in a correspondingly conical outer recess of an outer frame, which is characterized in that the substantially cylindrical or Multi-surface prismatic outer jacket of the drawing core has a radius of the jacket or distances of the prism surfaces from the central axis, which preferably by at least 3 µm, in particular by 4 - 40 µm e by 5 - 20 µm, is or are greater than the radius or the corresponding distances of the prism surfaces from the central axis of the essentially cylindrical or multi-surface prismatic inner walls of the inner frame sectors, which are preferably connected to one another by position-retaining elements and which are essentially conical. or having truncated pyramid-shaped outer surfaces, are arranged in a recess of an outer mount which is substantially frustoconical or truncated pyramid-shaped.

It should be noted separately that the recess of the outer frame, which ensures the stable fit of the multi-part inner frame, cannot be purely conical but also truncated pyramid-shaped. Ellipsoidal or spheroidal formation of the inner wall of the outer frame is also possible. In any case, the recess should be designed so that its cross section is reduced in the direction of drawing.

The outer surface of the inner frame, which houses the drawing die and is arranged in the recess of the outer frame, can be designed in accordance with the shape of the inner surface of the recess of the outer frame that has just been discussed. A substantially frusto-conical shape, that is to say a fit in the conical recess of the outer socket, is preferred for the outer shell of the divided inner socket.

It has been shown in the tool according to the invention that an optimal interaction of the outer and inner frames and the drawing core can be achieved if the generators of the frustoconical outer surface or if the surfaces of the frustum-shaped outer surface of the inner frame and those of the correspondingly shaped conical or frustum-shaped inner wall form an angle with the axis of the two sockets, the tangent of which is 0.08-0.125, preferably approximately 0.1.

The sectors of the inner frame are not clamped into the recess of the outer frame by means of a pressure screw in order to hold the drawing core and absorb the pulling forces acting on it, rather the difference in radius or distance between the drawing core and the “too small” dimensioned multi-part inner frame allows the No element for clamping. This is done by the forces from the drawing process and, as was found, ensures an excellent fit of the drawing core and its optimal strength and durability during operation. A preferred number of the segments forming the inner frame is two, so that the effect is achieved with little effort.

For the precise positional adjustment of the inner frame sectors to each other, the previously mentioned positional elements, e.g. form-fitting interlocking projections and matching recesses, on the opposite end faces delimiting the gaps between the individual sectors.

The inner wall of each of the inner frame sectors ends in the direction of drawing with an annular shoulder-like projection which advantageously extends from one end face directed towards the gap between the sectors to the other, similar end face and serves for the stable support of the drawing core during the drawing process. The support of this shoulder is advantageously flat, but it can also be, for example, flat-tapered if the drawing core is designed accordingly.

Maintaining in the drawing tool according to the invention a difference between the radii or distances of the prism surfaces from the central axis of the drawing core and the inner wall of the inner frame sectors in such a way that the radius of the outer surface or the distances of the prism surfaces of the drawing core from its central axis essentially All areas of the area (s) must be or must be larger by a small amount than the radius or the distances from the central axis of the interior mounting sectors at the respective corresponding locations, as has surprisingly been found, in association with the other design features of the drawing tool according to the invention, on the one hand, an optimal pre-tensioning of the core, evenly over the area of the circumference encompassed by the sectors, and on the other hand, an extremely stable position of the core in the socket, without a pressure screw for clamping the inner frame together Core in the outer version see is.

These advantages of the tool in the assembled or operating state are supplemented by the further advantages of simple handling when the drawing core is removed from the socket, be it for reworking after wear or, for example, for re-coating the core and drawing hole and when inserting or reinserting the core.

The construction according to the invention is unexpectedly less sensitive to changes in the difference between the two radii or the corresponding distances from the central axis of the core outer jacket and inner frame inner surfaces. This has the advantage that cores, without having to cover their outer sheath or have to be reworked later, can be repeatedly subjected to a re-coating of the draw hole which has been robbed due to wear of its hard material coating, and which occurs as a result of the respective co-coating of the outer sheath which is not subject to wear additive enlargement of its radius or distance of the prism surfaces from the central axis has no adverse effects on the preload and fit of the drawing core in the socket. Thus, despite the increase in the radius of the outer jacket or the spacing of the prism surfaces that occurs with multiple re-coating, the pull core used several times due to the difference between the two radii to be observed from the outset according to the invention, or the corresponding spacing effect of effectively clamping the core with the Sectors of the inner frame fully preserved. The difference in the differences observed here is presumably supported by the self-locking seat of the inner frame in the tapered recess of the outer frame. Since on the one hand a re-coating of a drawing core causes a fraction of the cost of a new drawing core, and on the other hand there is no need to rework the core on its outer surface to adjust the original radius dimension, the drawing tool according to the invention provides an economic advantage that should not be underestimated.

The drawing core itself usually consists of a hard material or a hard metal, for example only carbidic, nitridic and / or oxidic hard materials, or a high-speed steel.

The stone, and in particular the drawing hole, is preferably provided with a hard material coating, for example based on titanium or hafnium nitride or carbonitride, in order to increase the wear resistance and thus the service life.

As already stated, the drawing core can have a multi-surface prismatic outer jacket. It can be provided that a cylindrical core is inserted into such a multi-surface prismatic recess of the divided inner frame or vice versa, the criterion of the difference between the distance between the surfaces and the radius or vice versa must always be met.

In the tool according to the invention, it is generally expedient to provide an undivided drawing core, but if, e.g. a division of the drawing process into two parts is desired, for example two drawing cores, one of which has a first drawing part and the second of which has a supplementary part, can be arranged in drawing tools according to the invention which are connected directly one behind the other.

Depending on the thickness of a coating of a core applied layer can be carried out up to about ten post-coating operations without any changes to the frames and without their replacement.

Additional advantages are the uncomplicated manipulation of the simple plugging together of the inner frame sectors with the position holding elements arranged in their end faces facing the columns for fixing the drawing core and the likewise simple insertion of the inner frame into the conical or pyramidal recess of the outer frame. When replacing the core, neither a screwing process nor a careful, correct fitting of the core between the parts of the socket is necessary.

During the drawing process itself, the intensity of the drawing of the drawing core is clamped in a stable manner, essentially controlled by the forces involved. A particularly simple replacement of the drawing core can take place in one embodiment of the tool, in which the position retaining elements releasably connecting the inner socket sectors to one another are formed by vertically projecting dowel pins, which are formed in each case by the end faces of the inner socket sectors facing the columns of the inner socket recesses arranged on the opposite end face of an adjacent sector engage positively.

In a further preferred embodiment of the drawing tool according to the invention it is provided, in the area of the cut lines or edges between the inner frame inner wall and the end face of the columns of the multi-part inner frame facing each of the inner frame sectors, and at least essentially in the direction of the lines or edges mentioned tending to arrange recesses, grooves, bevels, roundings or the like.

The resulting elimination of the originally described edges has the advantage that no extreme values of the clamping forces act on the drawing core, even in the area of the gaps between the individual sectors of the inner frame, so that a particularly uniform prestressing of the drawing die along its entire circumference and thus a particularly uniform absorption of the drawing forces is achieved by the sockets.

Instead of the cut edges mentioned, recesses having an essentially rectangular or square cross section are most advantageously provided.

• Fig. 1 ist eine Schnitt-Ansicht eines erfindungsgemäßen Werkzeuges, das entlang der in der von Fig. 2 dargestellten Draufsicht des erfindungsgemäßen Ziehwerkzeuges gezeigten Ebene 1-1 geschnitten ist.

The drawing tool according to the invention is explained in more detail with reference to the drawing:

• Fig. 1 is a sectional view of a tool according to the invention, which is cut along the plane 1-1 shown in the plan view of the drawing tool according to the invention shown in Fig. 2.

1 shows how the sector 20 of the inner frame 2, which has a correspondingly shaped, conical counter surface 22, is arranged in the recess 18 of the outer frame 1 which is delimited by a conical inner surface 11. To the inside, the sector 20 has a cylindrical inner wall 21 which, together with a second sector, not shown, forms a recess 28 for receiving the drawing core 4 with drawing hole 48, which has a cylindrical outer jacket 42. The common axis is designated 27.

The cylindrical recess 28 in the inner mount 2 is narrowed in the direction of drawing by an annular shoulder-like projection 23, on the flat support surface of which the drawing core 4 rests in the embodiment shown. In the area of the intersection of the mentioned contact surface of the projection 23 and the cylindrical inner wall 21 of the inner frame sector 20 there is a recess. With 26 a recessed recess is designated at the point of transition from the end faces 31 and 32 to the inner wall 21 of the sector 20.

The two end surfaces 31 and 32 delimiting the gaps between the inner frame sectors are directed towards the viewer, position pins 24 projecting perpendicularly from the end surface 31, which engage in corresponding recesses in one of the end surfaces of the inner frame sector, not shown, and in the end face 32 position-holding recesses 25 are arranged, into which corresponding position-holding pins arranged on the other of the end faces of the inner frame sector, not shown, engage.

The drawing die 4, whose outer jacket radius is larger by an amount, for example in the order of a few to a few tens of micrometers, than the radius of the cylindrical inner walls of the sectors of the inner frame 2 is surrounded by them like a jaw and also due to the radius difference additionally clamped under pre-tension (about 6% o).

The tight fit of the inner frame 2 in the recess 18 of the outer frame 1 is ensured by the conical design of the two parts, the ratio of the cone height to the cone base radius advantageously from about 8: 1 to about 12: 1, preferably about 10: 1, is.

A typical value for the opening angle of the cone is about 5.5 °

The stable seat of the inner frame 2 and thus of the drawing core 4 is particularly supported by the tapering forces, ie the forces acting in the direction of drawing, during the drawing process.

FIG. 2 shows a top view of how the outer version 1 has two identical designs in the embodiment shown Inner frame sectors 20 and 20a divided inner frame 2, which forms gaps 29, 30, is arranged centrally, and as between the two inner frame sectors 20 which are connected to one another via the position pins 24 which engage in the position hole recesses 25 and can be moved along these pins , 20a of the drawing core 4, which has a somewhat larger jacket radius, is clamped as by baking.

In the region of the two cuts of the inner wall 21 of the sector 20 with the end faces 31 and 32, approximately rectangular recesses 26 are arranged which run in the direction of the cut edges, not shown. Sector 20a has the same recesses. They enable the core 4, which is somewhat larger in comparison to the recess in the inner socket, to "escape" when it is clamped between the two jaw-like inner socket sectors 20 and 20a in the ready-to-operate state and by the latter as a result of their seat in the conical part being reinforced by the pulling forces Recess of the outer socket 1 is biased.

Otherwise, the same parts are designated with the same reference numerals in FIG. 2 as in FIG. 1.

In summary, it should be mentioned that the pulling device according to the invention is not only due to its simple and safe type of operation when changing the drawing core - the individual parts are simply "plugged into one another" in the simplest way, but also because of its simple and robust design even in the case of rough handling, as is the case in the pulling operation is common, shows practically no susceptibility to failure. Finally, it should be mentioned again that the drawing core can be recoated a number of times without having to process the dimensions which change as a result of the coating on the outer core jacket, which, in addition to the savings due to repeated usability of the drawing core, that is to say a substantial increase in the service life , incidentally, coupled with the practically unlimited usability of its version brings further economic advantages.

Claims (5)

1. A drawing die with a drawing core (4) having the drawing hole, preferably being in one piece, and having an outer envelope (42) which is for example cylindrical, which tore is detachably inserted into an inner frame (2) having substantially conical outer faces (22), preferably being multiaxially symmetrical, and being divided into two or more sectors (20, 20a) substantially delimited by generatrices parallel to the tool axis and having a shoulder type projection (23) in the drawing direction and a slot (29, 30) extending in the direction of the axis (27), the inner frame (2) being arranged in turn in a substantially conically formed recess (18) of an outer frame (1), corresponding to its outer faces (22), characterised in that the outer envelope (42) of the drawing core (4), which is substantially cylindrical or polyhedrally prismatic, has a radius of the (42) or distances of the prism faces from the central axis (27) at least 3 µm, more particularly 4 - 40 um, preferably 5 - 20 J.lm, greater than the radius or the corresponding distances of the prism faces from the central axis (27) of the inner walls (21), made substantially cylindrical or polyhedrally prismatic, of the inner frame sectors (20, 20a) which are preferably interconnected by means of positional holding members (24, 25) and which have outer faces (22) substantially in the form of a truncated cone or pyramid and are arranged in a recess (18) of an outer frame (1) having an inner wall (11) formed substantially as a truncated cone or pyramid.

2. A drawing tool according to claim 1, characterised in that, in the region of the intersecting edges of the inner frame inner wall (21) and the end faces (31, 32) of each of the inner frame sectors (20, 20a) facing the slots (29, 30) of the multi-part inner frame (2), recesses (26), grooves, bevels, chamfers, or the like are arranged, so as to extend at least substantially in the direction of the said edges.

3. A drawing tool according to claim 2, characterised in that the recess (26) has a substantially rectangular or square cross-section.

4. A drawing tool according to any one of claims 1 to 3, characterised in that the positional holding elements (24,25) which detachably connect the inner frame sectors (20, 20a) to one another are formed by dowel pins (24) which overlap substantially perpendicularly the end faces (31, 32) of the inner frame sectors (20, 20a) facing the slots (29, 30) of the inner frame (2), and which engage in recesses (26) arranged in the respective opposite end face of an adjacent sector (25) in a form locking manner.

5. A drawing tool according to any one of claims 1 to 4, characterised in that generatrices of the outer faces (22), made in the form of a truncated cone or pyramid, of the sectors (20, 20a) of the inner frame (2) and correspondingly the inner wall (11), in the form of a truncated cone or pyramid, of the outer frame (1) form with the axis (27) of both f rames (1, 2) an angle whose tangent is 0.08 - 0.125, preferably 0.1.

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