EP0634959A1

EP0634959A1 - Process and device for the continuous production of cylindrical rods with at least one internal helical channel, and sinter blank made by this process.

Info

Publication number: EP0634959A1
Application number: EP93908925A
Authority: EP
Inventors: Joachim Heisinger
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-04-08
Filing date: 1993-04-07
Publication date: 1995-01-25
Anticipated expiration: 2013-04-07
Also published as: DE59305967D1; JPH08502015A; WO1993020961A1; JP2004339610A; JP3662249B2; ATE150675T1; EP0634959B1

Abstract

The description relates to a process for the continuous production of cyclindrical rods (24) with at least one and preferably a plurality of internal helical channels (26) of predetermined cross-section uniformly distributed around the periphery. This process is used especially in the production of a sintered metal or ceramic blank in which the plastic compound forming the blank is pressed out of a nozzle mouth (14), with the compound (12) flowing along the axis (44) of the helically twisted pin (40, 42) journal secured on a nozzle mandrel. To simplify the process and eliminate as far as possible the dependence of the result of extrusion on the extrusion process parameters, there is a rotatable cooling channel former in the nozzle aperture having at least one helically pretwisted pin (40, 42) rigidly attached to a shaft (30) at least at the securing point, thus being dimensionally stable. The helical pretwist exactly corresponds to the shape of the helix of the internal channels (26) to be formed in the blank. Thus a constant rotary impulse defined by the pitch of the helix is imposed on at least one pin (40, 42) by the plastic compound (12) flowing along its axis (44) essentially over its entire length, with the result that the compound (12) cannot be plastically deformed in the nozzle mouth (26).

Description

Method and device for the continuous production of cylindrical rods with at least one internal, helical channel, and sintered blank produced by this method

The invention relates to a method for the continuous production of cylindrical rods with at least one internal helical channel according to the preamble of claim 1, further to an apparatus for performing the method, i. H. on a suitable for performing the method extrusion tool according to the preamble of claim 11 and 28, and finally on a cylindrical molded body produced by the method according to the preamble of claim 44.

From a plasticized ceramic or powder metallurgy mass continuously, for example in the extrusion process, cylindrical shaped bodies with internal, at least partially helical channels of a predetermined cross-section are increasingly used, for example, in the tool industry, and here in particular in the manufacture of drilling tools needed, which have an internal coolant or flushing agent supply, so that the coolant or flushing agent can exit the tool in the immediate vicinity of the cutting edge. The turning profile of the at least one internal cooling channel is necessary when the tool to be manufactured, such as. B. on a drilling tool helical flutes are provided, for example, are ground. Since the axial length of such drilling tools has been significantly increased, it is particularly important to precisely control and control the slope of the at least one internal helical cooling channel during manufacture, so that the position of the cooling channel in the drill or tool steps over the entire length of the cutting part is in the range of predetermined, narrow tolerances.

In the meantime, numerous attempts have already been made to create an economical extrusion process for the production of cylindrical, rod-shaped blanks for the manufacture of tools.

An extrusion method is already described in US Pat. No. 2,422,994, in which a plasticized powder metallurgy composition is pressed through an extrusion die, the inner surface of which has projections of a predetermined cross section. In the area of the center of the extrusion die, rod-shaped bodies extend in the axial direction, which are attached to a mandrel lying in front of the extrusion die and surrounded by the plasticized mass. This process works in several stages, in that the plasticized raw material is first formed into a drill blank with at least one straight, external groove, whereupon the blank designed in this way is twisted by a relative rotary movement between the extrusion die and the raw material. It has been shown that such a two-stage shaping process is out of the question for most of the raw materials used in the meantime because the blank emerging from the extrusion die is regularly so sensitive to pressure that even the smallest forces acting on it are undesirably large Deformation leads not only to the outer contour, but also to the inner, molded channels, as a result of which the reject rate increases excessively. In DE-PS 36 01 385, therefore, a method for producing a drilling tool with at least one, helically running, internal coolant channel is already presented, in which the helical course of the at least one internal coolant channel is generated simultaneously with the extrusion of the plastic mass. For this purpose, the inside of the nozzle mouthpiece is equipped with a helical egg-shaped profile, the helical pitch of these projections being matched to the helical pitch of the cooling channels to be aimed at. In the center of the extrusion nozzle, elastic pins are provided which are attached to a nozzle mandrel with their upstream ends and whose elasticity is selected so large that the pins can follow the swirl flow induced by the inner contour of the nozzle mouthpiece. Apart from the fact that with this type of production a relatively large amount of energy has to be applied in order to impart a homogeneous swirl flow to the entire flow cross-section, it has been shown that in the blanks produced by this known method, the pitch of the cooling channel coil often depends on the pitch of the coil the projections or depressions on the inner surface of the nozzle mouthpiece deviate. This has the consequence that the projections or depressions on the inner surface of the nozzle mouthpiece had to be formed in large numbers, but with a relatively small depth, in order to keep the material losses as small as possible. Accordingly, the finished sintered parts are first regularly ground on the outside before the flute is introduced.

In order to save the process step of grinding the finished sintered cutting part blanks externally, a method is proposed in DE-OS and in EP 0 465 946 A1, in which the inner surface of the nozzle mouthpiece is formed by the outer surface of a circular cylinder is. The nozzle mouthpiece is positioned within the mass flow.

REPLACEMENT LEAF Suspended swirl device upstream. According to an alternative, a swirl movement which is uniform over the cross section of the strand is forced on the extrusion by means of this swirl device, while according to the second alternative of the swirl device a swirl or rotary movement is forced on by the extrusion. To form the inner channels, the following thread-like material projects into the mass flow of the swirl or rotary movement. In this case, the circular diameter on which the cross sections or the cross section of the at least one internal coolant channel in the extruded blank comes to lie is influenced by the flow speed and by the frictional losses in the nozzle mouthpiece, which is particularly the case when changing the extrusion mass from a batch to the other can have a negative impact. According to a further variant of this method, it is therefore proposed to make the nozzle mouthpiece rotatable, the rotational movement of the nozzle mouthpiece being intended to correct the swirl movement of the mass flow.

Document EP 0 431 681 A2 finally discloses a method and a device for producing a cylindrical, metallic or ceramic blank of the type described in the introduction, in which at least one twisted through the center of an internally smooth, circular-cylindrical nozzle mouthpiece Middle pin extends from a rigid material. This at least one twisted center pin is attached to a stationary mandrel in front of the inlet area of the nozzle mouthpiece. The pins are thus pre-shaped helically in this process and made of a rigid material such as. B. made of hard metal or steel. It could be shown that it is possible up to a best-l-mm, relatively small ratio between the inside diameter of the nozzle mouthpiece and the outside diameter of the at least one center pin in the region of the nozzle mouthpiece towards additional twisting devices ε waive. It is assumed that the rigid center pins are able to force the mass flow over the entire cross-section to have a uniform swirl movement. If the ratio mentioned above is larger, the swirl of the blank must be increased by additional swirl aids in the nozzle. It has also been shown that it is regularly necessary to twist the center pins more than the twist of the helical channels then actually present in the blank. This requires extensive tests for each extrusion molding compound, which make the manufacturing process more expensive and necessitate complex quality assurance measures.

The invention is therefore based on the object of developing a method and a device in accordance with the preamble of patent claim 1 or patent claim 11 or patent claim 28 such that extrusion blanks with a precisely defined course of internal, helical cooling channels with a maximum dimension reproducibility and high structure quality can be produced, there should be no restrictions with regard to the area of application of the method with regard to the composition of the extrusion, the process parameters or with regard to the geometry of the blank. This object is solved by the features of claims 1, 11 and 28, respectively.

The inner channels are produced without plastic deformation of the mass located in the nozzle mouthpiece in the master molding process, the mass preferably entering the nozzle mouthpiece essentially without swirl, flowing over the entire flow cross-section either swirling substantially at least one pin and passing through it as it passes sets the nozzle mouthpiece in a continuous rotary movement corresponding to the pitch of its helix, or flows past a pin suspension, depending on the situation

REPLACEMENT LEAF έ can be driven by the flow velocity. The device according to a variant is characterized in that the at least one pin is connected in a rotationally and axially fixed manner to a shaft mounted in the nozzle mandrel about an axis parallel to the axis of the nozzle 5 and is twisted such that the plastic mass flowing along its axis im impresses a constant angular momentum, essentially defined over the entire length, by the pitch of its helix. According to a further variant, the shaft carrying the at least one pin, the connection point to the pin located radially inside the pin in the nozzle mouth, has an additional drive, in which case the pin can be flexible and the drive can be controlled independently of the desired pitch is.

1.5

The invention fundamentally frees itself from the idea of imposing a swirl movement corresponding to the helix pitch to be produced on the highly viscous mass flow during extrusion, and at the same time plastically increasing the mass relatively strongly

20 deform. Rather, the invention is based on the idea of setting the at least one wire into a rotational movement by the flow inflow forces accumulating over the length of the pin, such that when the plastic mass passes through the nozzle mouthpiece, at least one

25 helical inner channel is created, the slope of which corresponds exactly to the slope of the pre-twisted pin. To this extent, the method according to the invention works by reversing a corkscrew effect, the corkscrew spiral with the pin and the cork with the plastic one

30 extrusion is to be compared. The at least one inner helix thus arises according to the invention in the primary molding process. The particular advantage of the method according to the invention lies in the fact that virtually no energy has to be expended to twist the cross-section of the extrusion compound.

35 impress flow, which also means that the cooling duct former in the form of the rotating parts only

REPLACEMENT LEAF wrestle and subjected to reproducible forces. In this case, the invention takes advantage of the fact that, for a given helix pitch, the pitch angle increases with increasing proximity of the helix surface to the central axis, so that the approach angles become smaller. In comparison to the arrangement of swirl device inflow surfaces in the area of the inner jacket of the nozzle mouthpiece or. at radially further outward locations to energetic advantages. In other words, the flow of the extrusion compound is claimed as little as possible in the manufacture of the internal cooling channels, which results in the particular advantage that the blank has a very homogeneous structure at the outlet of the nozzle mouthpiece. It has surprisingly been found that the accuracy of the introduced, at least one helical cooling channel, namely with respect to the slope, radial position, angular position and cross-section, could be kept at a very high level, regardless of whether and if appropriate, in which way a certain roughness of the inner surface of the nozzle mouthpiece is selected or not.

According to the invention, a cylindrical extrusion body with internal, helical cooling channels can thus be produced for the first time, which has a cross-sectional shape that deviates from the circular shape, for example a rectangular, polygonal or elliptical shape arrives. Because of the method according to the invention, there are no longer any dependencies between the cross section or the diameter of the blank and / or the degree of plasticization and / or the extrusion parameters, such as the extrusion speed, for a large area. In any case, the helix in the blank corresponds exactly to the preformed helix of the twisted wires. Advantageous developments of the invention are the subject of the dependent claims.

With the development of claims 2 or 12 or 29, the manufacturing accuracy and reproducibility are further improved with little outlay on the device.

In this case, the rigid or flexible pins are supplied with a friction-reducing fluid, preferably a friction-reducing liquid or a liquid-like substance, preferably under pressure. The greatly reduced friction in this way leads to the smallest reaction forces between the molding compound and the at least one pin. These smallest reaction forces in turn make it possible to design the pin carrier organs with the smallest possible cross section. These pin carrier organs are formed by the components such as webs, shafts and shaft bearings. Because these pin carrier members can thus be designed with a smaller cross-section according to the invention, they also lead to smaller reaction forces which would otherwise disrupt the molding compound flow. The sum of the forces acting radially on the molding compound according to the invention is so small due to the measures according to the invention that they are no longer reproducibly able to force the molding compound flow either locally or over the cross section. It could be shown that the internal and external holding forces of the molding compound counteract this tendency effectively. In this case results from the inventive Maß¬ took the additional advantage that _r to the cooling channel forming, at least one pin with no appreciable wear longer occurs. The development according to the invention of the subject of the main patent is thus comparable to a quasi hydrostatic mounting of the cooling channel former in the molding compound. The fluid is preferably supplied under pressure and the fluid consists of the plasticizer of the molding compound or it has at least one component of this plasticizer.

Favorable effects which reduce the frictional force already result when the fluid reducing the frictional force is present in the region of the pins, ie. H. whose surface is wetted. An additional improvement results with the development of patent claim 4 or patent claim 31. Here, the fluid reducing the frictional force is supplied to the shaft bearing through the bearing sealing gap at the shaft outlet. In this way, a hydrostatic carrier film is formed over the entire surfaces of the cooling channel former located downstream of the shaft bearing. This hydrostatic carrier film then exits exclusively through the channels which are then formed. It can be assumed that there are no inclusions on the flow around organs, such as the shaft or the shaft-web connection within the molding compound. This is due to the fact that the fluid forming the hydrostatic gap, i. H. the liquid forming the hydrostatic gap looks for the simplest way over the surfaces into the channels formed by the internal pressure of the molding compound.

Particularly good pressure conditions when passing through the nozzle mouthpiece are achieved with the further development of claim 5 or claim 13. Since the highly viscous mass does not behave like an ideal liquid, but instead has a certain elasticity, care must be taken that When flowing through the nozzle mouthpiece and the helical rods located therein, there is sufficient pressure at all points to close the cross section. This is particularly important in the inlet area of the nozzle mouthpiece or in the areas in which either by the design of the extrusion die or

HE changes in the flow cross-section occur due to other obstacles in the flow. According to an advantageous development of the invention, the pressure is controlled via the mass flow cross section by the design of the inner surface area of the nozzle mouthpiece. This lateral surface can, for example, also be designed in such a way that the flow cross-section gradually decreases towards the outflow side in order to counteract the pressure reduction to the environment caused by the fluid mechanics (exit cross-section of the nozzle mouthpiece).

When the mass entering the nozzle mouth meets the twisted rods, it must absorb a reaction moment. By suitable design of the inner jacket and / or by suitable measures in the area of the cooling channel former in the area of the nozzle inlet, the traction forces of the cooling channel former can be absorbed in such a way that the mass flows swirl-free through the nozzle mouth and emerges from it.

A suitable measure is, for example, the rotational movement of the rods forming the cooling channels, i.e. the mass flow. to support the cooling channel former by means of an additional drive, the most advantageous embodiment of such an additional drive being to be constructed in such a way that the additional drive torque is just large enough to compensate for the reaction counter-torque.

According to a further variant of the invention, as described in claim 28, the additional drive can advantageously be combined with a cooling duct former, in which at least one flexible core pin sits at the end of a shaft projecting into the nozzle mouth, so that the shaft is rotated in a controlled manner depending on the desired pitch of the channel helix. The same advantages explained above are achieved here as well // in this case the entire mass flow cross section is not subjected to a swirl and the channel is again formed in the primary shaping process.

A further, particularly simple possibility of providing this additional drive torque is the subject of patent claim 5 or claim 19. The friction-related braking torque can be largely compensated for by a beveling of the upstream end faces of the rods forming the cooling channels . This is the subject of patent claim 20.

If the at least one pin, which forms the associated internal cooling channel, is extended in the upstream direction beyond the hub body producing the connection to the shaft, which is the subject of claim 18, the introduction of the bending moment from the bars into the hub body is additionally very favorable , whereby the connection point between the hub body and the pin can be kept shorter.

The initiation of the uniform rotary movement on the pins sitting on the shaft takes place mainly in the first section, i. H. in the actual guide section of the nozzle mouthpiece. For this reason, the stiffness of the wires, which decreases with increasing distance from the connection point to the shaft, does not affect the dimensional accuracy of the inner channels.

A further or additional measure to exclude any rotation of the emerging blank - this could interfere in certain applications - is that at least in this area of the flow inlet a linearization, ie. H. axial alignment and stabilization of the flow with the aid of a flow guide

REPLACEMENT .2. Chenanagement is carried out. An advantageous possibility of forming such a flow guide arrangement is the subject of claim 34. Here, for example, regular axial grooving can be used, this design of the inner surface of the nozzle mouthpiece advantageously being used at the same time, which is located at the end of the hub to compensate for the cross-sectional change resulting from the rotary shaft. In this case, the axial grooves then only run to the end of the connecting hub between the pins and the rotary shaft.

With the developments according to patent claims 37 to 40, it is advantageously prevented that in the spatial flow around the hub body due to the frictional behavior of rigid or flexible pins or threads attached to it, which either by their pre-coiled shape or by a controlled one Rotary drive exert an angular momentum on the swirl-free molding compound, which has a negative influence on the structure and the accuracy of the molded article production. These negative influencing factors also include an angular momentum which only triggers a swirl movement of the molding compound with a small radial extension towards the nozzle jacket. In order to compensate or eliminate this swirl movement occurring near the axis of rotation or near the pitch circle of the at least one pin, guiding devices are advantageous, which can also have the smallest dimensions, the axially flowed cross-section being similar to that of a Turbomachine with a small axial gap next to the turbine-like channel former, ie at least one pin is placed. These guide devices are preferably fin-like and, for example, are made in one piece with the mandrel. However, they can also be attached to this mandrel as required. The flow guide surface arrangements, which act as swirl prevention surfaces, preferably do not extend over the entire flow cross-section, because the above-mentioned swirl movement in this case also has only a small radial extent. However, it is of course also possible to allow these swirl prevention devices to act over the entire flow cross section.

A particularly effective device for compensating the swirl acting on the molding compound from the cooling channel former is the subject of patent claim 39. In this case, the swirl impulse triggered by the cooling channel former on the molding compound is compensated for by a counter-swirl introduced in the opposite direction of swirl. This guide device compensating the swirl can, for example, have the exact shape of the hub body or be designed such that the frictional forces of the center pins which trigger the swirl pulse are also compensated. This part in the flow, i. H. this flow part can then also be driven in a controlled manner or stored freely and rotates in the opposite direction to the direction of rotation of the channel former.

Because of its functional principle, the invention can be used for any cross-sectional configuration of the blank, but also for any cross-sectional and positional configuration of the internal cooling channels. Particularly simple, because symmetrical conditions arise when the rods are arranged point-symmetrically to the axis of the rotating shaft. With the development of claim 41, the inflow conditions of the highly viscous, ie. H. Optimize the plastic mass in the nozzle mouthpiece and the inflow conditions of the helical core rods.

Further advantageous refinements are the subject of the other subclaims.

Exemplary embodiments of the invention are explained in more detail below with the aid of schematic drawings. > v

Show it:

1 shows a schematic axial section in the region of the front end of an extrusion die to explain the functional principle of the method according to the invention;

1A shows the section corresponding to IA-IA in Fig. 1.

Fig. 2 is a view similar to FIG. 1, but expanded, of the extrusion die to explain the structure of the die mandrel according to the invention

Fig. 3 is a sectional view corresponding to III-III in Fig. 2;

4 shows a partial sectional illustration of the nozzle mouthpiece with a somewhat modified contour of the inner lateral surface;

5 shows a schematic axial section in the region of the front end of an extrusion die to explain the

Operating principle of a modification of the method;

6 shows a modified embodiment of the extrusion die;

7 and 8 are partial sections to show further embodiments of the extrusion die;

9 is a view similar to FIG. 5 of a further embodiment of the extrusion die with a modified feed of a substance that reduces the frictional forces;

Fig. 10 on a somewhat smaller scale another embodiment of the extrusion die with a modified guide surface arrangement for swirl reduction or swirl compensation;

11 shows the section XI-XI in FIG. 10;

FIG. 12 shows a view similar to FIG. 10 of a further embodiment with a modified guide surface arrangement for swirl reduction or swirl compensation;

Fig. 13 is view XIII in Fig. 12;

FIG. 14 is a view similar to FIG. 10 of a modified embodiment of a device for reducing what is exerted on the molding compound

Swirls;

Figure 15 shows the section XV-XV in Fig. 14 .;

Fig. 16 is a view similar to Fig. 10 of another

Embodiment of an extrusion die with a special, swirl-compensating flow part; and

17 shows the section XVII-XVII in FIG. 16.

In the following, reference is first made to FIGS. 1 to 4 in order to be able to clarify the principle of the cooling channel shaping on which the method is based in the primary molding process.

In FIG. 1, the reference numeral 10 denotes an extrusion tool which, according to FIG. 14, is flowed through from right to left by a highly viscous, plasticized metallic or ceramic compound 12. 14 denotes a nozzle mouthpiece, which is either formed in one piece with a nozzle carrier part 16, or is replaceable on the last one.

REPLACEMENT LEAF / - rem is held. The nozzle mouthpiece 14 and / or the nozzle carrier part are preferably fixed interchangeably in the extrusion tool 10.

The extrusion nozzle has two sections, namely a nozzle mouth DM and a nozzle inlet area DE, in which the plastic mass 12 is guided in a funnel shape into the nozzle mouth. A nozzle mandrel 18 is provided in the center of the nozzle inlet area DE, which will be described later with reference to FIG. 15 and has a conical surface 20 on its downstream side, so that an annular space is formed between the nozzle dome 18 and the nozzle carrier part 16 22 is formed, which opens into the nozzle mouth DM.

The extrusion die 10 or the extrusion die 14, 16 is used for the continuous extrusion of cylindrical rod-shaped shaped bodies 24 with at least one inside and helical, left or longitudinal channel 26. Such blanks are required, for example, in the manufacture of drilling tools, in this case the extrusion process is first followed by a drying or presintering process before the correspondingly deflected blank bars are subjected to the actual sintering process. The finished sintered blanks are then regularly machined by grinding at least one helical flute into the outer surface of the blanks. Since the course of the internal cooling ducts 26 cannot be monitored during machining, it is necessary to manufacture the blank 24 in such a way that in the region of the inner duct 26 the tolerances with regard to cross section, pitch circle diameter and eccentricity of the pitch circle to the axis 28 are as small as possible occur, namely in each radial section of the blank, which furthermore requires the exact adherence to a predetermined helical pitch WS. Otherwise, the case may arise that, particularly when grinding flutes into longer sintered ones

E _RSAT ZBLATT ZT blanks the groove comes too close to the inner channel, which either leads to a loss of strength or leads to the fact that the entire blank is no longer usable. This problem addressed above occurs irrespective of how many internal coolant or rinsing agent channels are formed in the drill and what shape these channels have, with another aspect to be taken into account in the production of metallic or ceramic blanks: the blanks in the drying and / or sintering phase are subject to considerable shrinkage, which regularly takes place depending on the structure. It is therefore important to take measures during the extrusion of the plasticized hard metal or ceramic mass which ensure that the extruded blank can be produced not only with great dimensional accuracy, but also with a maximum degree of homogeneity of the structure across the cross section . For this purpose, the extrusion die is constructed as follows:

A shaft 30 is rotatably supported in the center of the nozzle mandrel 18. The shaft 30 extends beyond the front end 32 of the nozzle mandrel 18 into the nozzle mouth DM and carries at the downstream end a plate-shaped hub body 34 (see also FIG. 16), which extends over its radially outer side surfaces 36, 38 is firmly connected to a helically pre-twisted pin or core pin 40, 42, respectively. In the exemplary embodiments shown, two such pins 40, 42 are provided, which are point-symmetrical to the axis 44 of the shaft 30 and thus of the hub body 34. However, it should be emphasized at this point that the invention is not limited to such a number and arrangement of the pins. It is equally possible to attach either one pin or a plurality of pins with a uniform circumferential distribution or with an uneven circumferential distribution to a hub, the individual cross sections of the pins also being able to differ from one another. It is equally possible to place the pins on different

REPLACEMENT LEAF ] δ> to arrange partial circles, where even the axes and / or the direction of rotation of the pins can differ.

The helically pre-twisted pins 40, 42 have exactly the pitch that the extruded blank 24 has. The dimension of the slope WS is determined taking into account the expected sintering shrinkage, as is the pitch circle diameter TKD. The helical axis 28 coincides with the axis 44 of the shaft 30, so that the cross section of the pin 40, 42 always moves on the pitch circle 46 when the shaft 30 rotates. For this purpose, it is necessary to fasten the pins 40, 42 in an exactly aligned manner on the side surfaces 36, 38 of the hub body 34, which is preferably done via a welded or soldered connection. As a material for the pins 40, 42, a material with a large modulus of elasticity, such as. B. steel, hard metal or a ceramic material is used.

In the embodiment shown, the pins 40, 42 have essentially the length of half a helical pitch WS / 2 and the arrangement is such that the pins 40, 42 extend at least up to the end face 48 of the nozzle mouthpiece 14, so that those of the rods 40, 42 internal channels 26 formed during the extrusion process maintain their shape and position outside the nozzle.

In the exemplary embodiment shown, the hub body 34 is seated in the nozzle mouth DM so that it has a predetermined axial distance AX from the front end 32 of the nozzle mandrel 18. This axial distance AX is preferably adjustable in order to be able to influence the flow conditions of the nozzle mouth DM and thus of the at least one pin 40, 42.

As indicated by arrows 50 in FIG. 1, the

Pins 40, 42 defined, and flowed axially in the region of the nozzle mouth DM. The flow thus hits below that determined by the slope WS and the pitch circle diameter TKD

REPLACEMENT LEAF A3

Angle PHI on the pins 40, 42. Since these are fixed via the hub body 34 and the shaft 30 about the axis 28 of the helix, namely about the axis 44 in the nozzle mouth DM, the wires 40, 42 become in the passage the plastic mass 12 through the nozzle mouth in a continuous rotary motion corresponding to the slope of the helix of the preformed pins with the angular velocity OMEGA. The force components acting in the circumferential direction caused by the inclination of the helical pins in relation to the direction of flow add up over the length of the pins 40, 42. The arrangement of shaft 30, hub body 34 and at least one helically twisted pin 40, 42 will therefore execute a uniform rotational movement predetermined by the flow velocity, the bending stress of the pins 40, 42 being kept relatively small. In this way, the pins 40, 42 function according to the principle of an axially flowing turbine with the output shaft 30, although the medium is not formed by an ideal, incompressible liquid, but by a highly viscous and to a certain extent elastic mass.

Since the hub body 34 with the fastening points 36, 38 is located in the region of the nozzle mouth DM, special measures have been taken in the embodiment shown to control the flow and pressure conditions in the nozzle mouth DM. The nozzle mouth is basically divided into two areas, namely a nozzle mouth entry area DME and a pure nozzle mouth flow area DMS. In the section DMS, the nozzle mouth has a predetermined, essentially constant cross-section, through which the flow rate can be controlled. If the cross section does not change in the DMS area, a constant flow velocity can also be assumed in this area in the first approximation. In the DME area, it is important to ensure that the effective flow

E _RS ATZBLATT to keep the cross-section substantially constant at least over the axial length of the DME area, but preferably over the entire axial length of the nozzle mouth DM. For this purpose, the diameter in the DME area is just increased by a dimension M in comparison with the section DMS, so that the ring area defined by the two diameters of the areas DMS and DME becomes approximately as large as that which can be seen in FIG. 3 Cross-sectional areas of the shaft 30 and the radial sectional area of the hub body 34, including the connection points 52. Excessive pressure fluctuations in the mass 12 when flowing through the nozzle mouth DM can be eliminated by suitably designing the transitions between the inner jacket surfaces in the DME and DMS area. In particular, the design of the nozzle mouth DM according to the invention prevents an excessive pressure drop precisely in the transition area between the sections DME and DMS, so that it is ensured with certainty that there is sufficient pressure in the section DMS to close the cross section .

Some possible designs of the edges 54 and 56 of the hub body 34 located upstream and / or downstream are indicated from the figures. The shown courses of these edges are only exemplary and can of course be varied within wide limits in order to determine the flow and pressure conditions in to influence or control this area accordingly. An alternate configuration of an edge 156 on the downstream side is indicated by dash-dotted lines. With such designs, the flow conditions can be influenced as desired.

When the hub body 34 and the pins 40, 42 flow axially, reaction forces also act in the axial direction, which have to be absorbed by the shaft 30. For this purpose, shaft 30 is assigned not only a radial bearing 58 but also an axial bearing 60, 2. \ which will be explained in more detail below with reference to FIG. 15. Otherwise, the embodiment according to FIG. 15 essentially corresponds to that according to FIG. 14, so that the same reference numerals are also used for the comparable components.

The axial bearing 60 is formed by a roller bearing, preferably a needle bearing, the needles 62 of which roll on running surfaces 64, 66 in the form of support disks. The disks are threaded onto the shaft 30. One of the disks, namely the disk 64, is supported flatly on an end face 68 of a mandrel insert 70 which is screwed into a central body 72 of an annular nozzle insert 74. Between the central body 72 and the assembly outer ring 76 of the nozzle insert, narrow ribs 78 are preferably provided at a uniform circumferential distance from one another, preferably connected in one piece to the outer ring 76. With 80 seals or seal packs between the mandrel insert 70 and the central body 72 are designated. The second running disk 66 on the other side of the needles 62 is supported by a thrust washer 82 which in turn is supported on the shaft 30 by a bearing adjusting nut 84. A plug labeled 86 can be removed from the mandrel central body 72 to lubricate the bearing.

Reference number 88 denotes a gap seal which has proven to be completely sufficient for the effective sealing of the bearings 58 and 60 against the mass 12. In addition, an O-ring can be provided behind the gap seal.

The construction of the bearing of the rotatable cooling duct former described above opens up the possibility of converting the extrusion head within a very short time, for example by exchanging the entire mandrel attachment 70 with the preassembled bearing 60. -----

The embodiment shown in FIG. 2 does not differ in terms of the design of the channel former in the form of the helically pre-twisted wires or rods 40, 42 from the embodiment according to FIG. 14. However, the transition of the pins or wires 40, 42 to the shaft is somewhat different solved otherwise:

In this case, the shaft 30 has a thickening 134 at its downstream end, and the pins 40, 42 are connected to the shaft 30 via a soldered or welded connection or a corresponding connection. It has been shown that even with this arrangement it is possible to ensure a very homogeneous structure of the extruded blank at the outlet of the nozzle mouth DM when using the method according to the invention or the extrusion device according to the invention.

It is of course possible to take measures in the area of the shaft thickening 134 in order to keep the flow resistance of the fastening section as minimal as possible. This is to be clarified by the sectional view according to FIG. 3. The web designated 234 is kept very narrow in cross-section and is preferably also formed on both sides of the axis by a helical surface, so that the continuous rotational movement of the cooling channel former 40, 42 results in the lowest possible flow resistances. The axial length of the connecting section between the wires 40, 42 and the hub body 34 or 134 or 234 can be made relatively short, since the pins or wires 40, 42 only rotate and slightly during rotation through the mass 12 - similar to a coil spring - be subjected to torsion.

The extrusion device described above works as follows: Second

The highly viscous mass 12 enters from the annular space 22 over a short run-in distance over the axial distance AX into the inlet area of the nozzle mouthpiece DME in the axial direction and displaces it from the rods or wires 40, the hub body 34 or 134 or 234 and the shaft 30 existing cooling channel former due to the inflow angle PHI into a continuous rotary movement corresponding to the pitch WS of the pin helix. The position of the helix in the nozzle mouth DM and the slope of the helix WS correspond exactly to the position and the slope of the helix of the cooling channel formed in the blank. Accordingly, in contrast to all conventional comparable extrusion processes, the flow through the nozzle mouth DM does not result in any plastic deformation of the mass passing through, but rather the formation of the internal, helical cooling channels in a primary molding process. The rods 40, 42 are mainly stressed in train. The same applies to the stress on the shaft 30, which can thus be formed with a relatively small diameter.

In the exemplary embodiments described above, the jacket 90 of the cylindrical inner recess of the nozzle mouth DM is smooth, and also in the area of the nozzle mouthpiece inlet DME. In the case of such a smooth design and in the event that the cross section of the nozzle mouth DM has a circular shape, the - although small - frictional moments caused by the surface flow against the coiled pins 40, 42 and the bearing friction forces lead to that the blank 24 emerges with a slight rotation about the axis 44. The dimensional accuracy of the inner channels formed with the cooling channel former is not affected by this, but in some applications this self-rotation can be undesirable. Various measures can therefore be taken to switch off this self-rotation:

TT One measure - not shown in the figures - consists in assigning an additional drive to the shaft 30, which applies an additional torque to the shaft 30 which is just large enough to cover the reaction moments 5.

A further measure, shown in FIG. 1, is to provide the upstream end faces 92 of the pins 40, 42 with a bevel such that an additional torque is applied to the cooling duct former by the inflow.

Finally, another possibility is indicated in FIG. 2 with dash-dotted lines. This is

1.5 to provide the wires 40, 42 upstream of the hub body 134 with an extension section 140, 142 and to provide this extension section with a spiral pitch which deviates from the desired helix pitch in the blank in such a way that the extensions 140, 142 flow against it Mass 12 that

20 applies additional torque covering the reaction torque to the cooling duct former.

Finally, it is also possible to provide flow guiding surfaces in the area of the nozzle mouth DM that block the flow of the

25 Axially align mass 12 in the nozzle mouth, d. H. help linearize. Flow guiding surfaces of this type can be provided, for example, in the inlet area DME, but also in the remaining area of the nozzle mouth DM. 4 shows such a flow guide surface arrangement in the form of an internal toothing

30 94 indicated. If the internal toothing 94 is limited to the nozzle mouth entry area DME, it is advantageous to choose the toothing in such a way that the toothing cross sections 96 protruding beyond the diameter 98 add up over the circumference, just the sum of the cross sections of the

35 shaft and hub 134 or 234. Of course, deviations from the previously described embodiment are possible without departing from the basic idea of the invention, which consists in precluding plastic deformation of the mass 12 in the nozzle mouth DM by pre-twisting a cooling duct former with a rigid connection between helically Bars 40, 42 and a rotatably mounted shaft 30 is moved with a predetermined relative rotational movement by the mass flowing in the nozzle mouth. In this way, the manufacturing method according to the invention can be used for all possible cross-sections, which is indicated in FIG. 1A, for example, by dashed lines through the cross-sectional boundary 100. In this way, the axis of the cooling channel former can also be arranged at will within the cross section of the nozzle mouth DM. Because of the structure according to the invention, there are no dependencies between the dimension in a wide range, for example the diameter of the blank, the degree of plasticization and the extrusion parameters, such as, for example, B. the extrusion speed. Accordingly, contrary to the prior art, the rods pre-twisted to the exact helix pitch aimed for in the blank no longer have to be over-twisted by expensive preliminary tests in order to achieve the desired pitch and position of the inner channel in the blank. The mass 12 is not subjected to any deformation work when it flows through the nozzle mouth DM and the moving components of the inner channel former are mechanically comparatively little stressed, since the cross-sectional areas claimed by the cooling channel former are relatively small compared to the total passage area of the nozzle mouth DM is.

Although the nozzle mouth DM in the device described above is approximately as long as half the helix pitch WS, it should be emphasized that the nozzle mouth DM can also be shortened compared to the helix pitch, but then the wires are also shortened accordingly, so 2. that they in turn end in the area of the nozzle outlet. Instead of the point-symmetrical arrangement of the rods 40, 42 described above, it is also possible to choose a different arrangement in comparison to the axis 44 or 28, it even being possible to use different cross-sections of the rods or Work wires.

In order to improve the positional accuracy of the internal cooling channels and the homogeneity of the structure of the extruded blank while at the same time increasing the reproducibility, further embodiments of extrusion dies are shown below with reference to FIGS. 5 to 17. The geometry of the extrusion die of these further variants largely corresponds to that of the previously described embodiments. For comparable components, reference numerals are therefore used which correspond to the reference numerals given above, but which are preceded by further numbers "3" to "9".

With regard to the geometry, the cooling duct former according to FIG. 5 differs only slightly from that according to FIG. 1. The helically pre-twisted pins 340, 342 are fastened to a shaft 330 via webs 392. The special feature is that the shaft 330 mounted in the nozzle mandrel 318 is equipped with an inner bore 331 and that the webs 392 are also provided with radial bores 393, which emerge at 395 on the surface of the pins 340, 342. The inner bore 331 and the radial bores 393 form a flow path for supplying a substance which reduces the frictional force between the molding compound and the pins 340, 342, for example a fluid, preferably a friction-reducing liquid or liquid-like substance. The feed is indicated by arrow 397 and is preferably carried out under pressure. As such a friction-reducing liquid or liquid-like Substance, for example, the plasticizer of the molding compound can be used. This substance emerges at 395 (a large number of such radial channels can also be provided over the circumference and also in the longitudinal direction of the pins 340, 342) and flows along the surface of the pins 340, 342, the entire surface of the pins being wetted becomes. This results in a greatly reduced friction between pins 340, 342 and the molding compound, which in turn leads to the smallest reaction forces between the pressing die and the pins. In this way, the cross section of the webs 392 and the shaft 330 can be reduced, as a result of which the reaction forces between the pin carriers and the molding compound are also reduced. The sum of the forces thus acting radially on the molding compound is so small by means of these developments according to the invention that they are no longer able to influence the molding compound flow either locally or over the cross section in such a way that a swirl movement is forced on. This is due to the fact that the internal and external cohesive forces of the molding compound are greater than this reaction force. There is the further side effect that the complete wetting of the pins 340, 342 with the low-friction liquid or the low-friction fluid virtually eliminates the wear of the pins.

FIG. 6 shows a variant of the extrusion tool, in which, in contrast to the illustration according to FIG. 5, no rigid, pre-used pins, but flexible pins 440, 442 are used, which are fixed to a fork-like branch 492 of a drive shaft 430. The shaft 430 and the fork 492 are hollow, so that - as indicated by the arrow 497 - a friction-reducing fluid is introduced through an inner bore 431 in the shaft 430 into the fork-like branch 492 and there to the flexible pins 440 , 442 can be passed on. In contrast to the embodiment according to FIG. 5 are consequently

REPLACEMENT LEAF the pins are flexible and they are actively driven via shaft 430. In order to be able to monitor the swirl-free exit of the press strand, a friction wheel 441 is provided at the exit of the nozzle, which is equipped with a displacement measuring device, not shown in detail.

Both embodiments have in common that the fluid supplied to the pins or threads results in a quasi-hydrostatic mounting of the pins or threads in the molding compound, which drastically reduces the influence of disturbance variables.

FIGS. 7 and 8 show variants of the suspension for the pins 440, 442. 7, orifices 495, which are distributed over the circumference and in the longitudinal direction of the pins 440, 442, in order to ensure a uniform outlet of the fluid fed in at 497 in order to reduce the frictional forces. The fork-like branch 492 in the embodiment in FIG. 6 is replaced in the variant in FIG. 7 by a diametral web 492 'which has an inner bore 493'.

8 is particularly advantageous when a thread-like band 441 ″ is fastened to the shaft 430. The shaft 430 ″ is again hollow and carries a fork piece at its end facing the nozzle mouth 492 ", in which the thread or a cord 441" is suspended. The point at which the friction-reducing substance emerges from the fork piece 492 "is designated by A.

In the embodiments described with reference to FIGS. 5 to 8, the components forming the inner channel are wetted exclusively in the area of the pins. Fig. 9 shows a variant in which all components of the cooling channel former downstream of the nozzle mandrel 518 with the 23

Friction-reducing substance are wetted. For this purpose, the nozzle mandrel 518 forms a shaft bearing 519 at its front end. In front of this shaft bearing 519 there is a bore 521 which is larger in diameter and surrounds the shaft 530, which in this embodiment can be designed as a solid shaft. The shaft 530 can be driven or can be rotated freely in the nozzle mandrel 18. Pins 540, 542 can be rigid or flexible.

The space between the shaft 530 and the inner bore 521 is the one that reduces the frictional force. Fluid, preferably filled the liquid, which in turn is preferably supplied under pressure, which is indicated by the arrow 597. The advantage of this embodiment is that this fluid is supplied through the shaft bearing 519, which can thus advantageously be designed as a hydrostatic bearing. Accordingly, in this embodiment, the entire surface of the cooling channel former downstream of the nozzle mandrel 518 is wetted with the substance with reduced friction, as a result of which the cross sections of the shaft 530 and the fork-shaped holding part 592 can be restricted to a minimum. Points 595 indicate that the friction-reducing liquid along the pins 540, 542 forms a hydrostatic carrier film on the entire surfaces of the cooling channel former located downstream of the nozzle mandrel. The liquid only exits through the channels that are then formed. The variant shown in FIG. 9 has the advantage that the hub body 592 can be equipped with the smallest possible cross-section that can be designed to be very aerodynamic.

The aim of the configurations according to FIGS. 10 and 10 is to minimize or compensate for the angular momentum exerted on the molding compound by the flow around the cooling channel former. Deviating from the embodiment according to FIG. 4, flow guide surface arrangements are in these embodiments S o is provided, which can also compensate for the angular momentum which triggers only a swirl movement of the molding compound with a small radial extent toward the nozzle jacket. For this purpose, guide vanes 641, 643 are attached to the nozzle mandrel 618 parallel to the axis of the extrusion die, which extend close to the upstream ends of the pins 640, 642 and have flattened portions 647, 645 at their front areas. The Lei sheet bodies are accordingly fin-like and they end with a very small gap SP upstream of the pins 640, 642, which act like a turbine. The guide bodies 643, 641 act like a guide device of a turbomachine, in which swirl compensation takes place at the crucial point.

A first variant of this swirl prevention device is shown in FIGS. 12 and 13. In this embodiment, the interface between flow guide pin 741, 743 and turbine-like pins 740, 742 differs from the variants described above. In other words, the gap SP is set here in the direction of flow. It can best be seen from the illustration according to FIG. 13 that the flow guide pin 741, 743 attached to the nozzle mandrel 718 forms a flattened portion 745, 747 at the downstream end.

In the embodiment according to FIGS. 14 and 15, other flow guide surface arrangements are provided, which are designated 841 and 843. In a departure from the exemplary embodiments described above, these flow guide surfaces are formed by plate-like bodies which cover the entire flow cross section. In accordance with the previously described configurations according to FIGS. 10 to 13, a flow guide surface 841, 843 is again present for each pin which is intended to form an internal channel, with the downstream end of the flow guide surfaces 3 years

841, 843 extends as close as possible to the upstream end of the pins 840, 842.

Finally, a further variant for a guide device compensating for the swirl will be described with reference to FIG. 16. In this embodiment of the extrusion die, there is again a device for minimizing the frictional forces between the molding compound and the cooling channel former, whereas such a device was missing in the embodiments according to FIGS. 10 to 15. It should be emphasized at this point that the swirl compensation device can of course achieve the advantageous effect regardless of whether or not such a rinsing of the cooling channel forming surfaces with friction-reducing fluid takes place, which reduces the frictional force.

In this case, the shaft 930, which carries the pins 940, 942 via a web 292, is guided in an outer shaft 935, which is supported in the nozzle mandrel 918. The outer shaft 935, like the other flow guide surface arrangements of the embodiments according to FIGS. 10 to 15, protrudes into the nozzle mouthpiece DM and carries, at a small axial distance AX from the upstream end of the pins 940, 942, a flow part 937 which essentially comprises the has the same cross-sectional configuration as the web 992, but, as indicated by the arrow G, is driven in the opposite direction to the cooling duct former 940, 942 (part K). The cross section of the flow guide part 937 which compensates for the swirl can also be optimized in such a way that at the same time the frictional forces of the center pins which trigger the swirl pulse are also compensated. The flow part 937 is preferably driven in a controlled manner. However, it can also be stored freely, the adjustment of the partial flow surfaces being such that an opposite rotational movement (direction of rotation G) to the rotational movement of the cooling channel former (direction of rotation K) is induced. The invention thus provides a method for the continuous production of cylindrical rods with at least one, preferably a plurality of internal and helically extending channels of predetermined cross-section which are uniformly distributed over the circumference. This method is used in particular in the production of a sintered metal or ceramic blank, the plastic mass forming the blank being pressed out of a nozzle mouthpiece by holding the mass along the axis of the helically twisted, held on a nozzle mandrel Pen flows. In order to simplify the process and to largely eliminate the dependence of the extrusion result on the parameters of the extrusion process, a rotatably mounted cooling duct former is provided in the nozzle mouth, which has at least one helically pre-twisted pin, which is at least on a shaft at the fastening point and thus dimensionally stable bil and rigidly attached. The helical pre-twisting corresponds exactly to the helix shape of the inner channels to be molded into the blank. As a result, a constant angular momentum defined by the pitch of the helix is impressed on the at least one pin by the plastic mass flowing along its axis, essentially over its entire length, so that plastic deformations of the mass in the nozzle mouthpiece are excluded.

Claims

1. Process for the continuous production of cylindrical rods with at least one internal, at least sectionally helical channel of predetermined cross-section, in particular for the production of a sintered metal or ceramic blank for a tool part, in which the plastic forming the blank ¬ mass is pressed out of a nozzle mouthpiece, for example flowing along the axis of at least one helically twisted pin held on a nozzle mandrel, characterized in that the inner channels without plastic deformation of the mass located in the nozzle mouthpiece are produced in the master molding process can be set by preferably the mass entering the nozzle mouthpiece (DM) essentially without swirl, flowing over the entire flow cross-section either swirling at least one pin essentially without swirl, and as it passes through the nozzle mouthpiece into a continuous, incline in its helix corresponding rotary movement, or flows past a pin suspension which can be driven as a function of the flow velocity.

2. The method according to claim 1, characterized in that the at least one pin (40, 42; 340, 342; 440, 442; 540, 542; 940, 942) a fluid reducing the frictional force to the mass, in particular a frictional force reducing liquid or liquid-like substance is supplied.

REPLACEMENT LEAF

3. The method according to claim 2, characterized in that the fluid is supplied under pressure, wherein preferably the fluid consists of the plasticizer of the mass or at least has a component of this plasticizer.

4. The method according to claim 2 or 3, characterized ge indicates that the fluid is supplied to the at least one pin (540, 542) via the pin suspension, so that over the entire downstream of the nozzle mandrel (518) located surface of a cooling channel former (530 , 592, 540, 542) forms a hydrostatic carrier film.

5. The method according to any one of claims 1 to 4, characterized in that the flow cross section within the nozzle mouthpiece (DM) is kept substantially constant, and that the flow or pressure conditions over the length of the nozzle mouthpiece (DM ) are kept constant or controlled by the cross section of the nozzle mouthpiece (DM), preferably the mass (12) flowing into the nozzle mouthpiece (DM) to support the rotary drive of the at least one pin controlled by the mass flow inside the nozzle mouthpiece (DM) (40, 42) is used.

6. The method according to any one of claims 1 to 5, characterized ge indicates that the at least one pin (40, 42) has an axis of rotation (44) which coincides with the central axis (28) of the flow cross section.

7. The method according to any one of claims 1 to 6, characterized ge indicates that a plurality of pins (40, 42) flow against the plastic mass, and that the pins have their common axis of rotation (44) and over the associated pitch circle ( 46) freely distributable, preferably evenly distributed.

REPLACEMENT LEAF

8. The method according to any one of claims 1 to 7, characterized ge indicates that the reaction moments of the channel former with the at least one pin (40, 42) are taken into account by an additional drive b that the blank exits the nozzle mouth in a swirl-free manner.

9. The method in particular according to one of claims 1 to 8, characterized in that the flow of the mass through the nozzle mouthpiece (DM) is linearized at least radially outside the at least one pin (40, 42) by flow guide surfaces (94).

10. The method in particular according to one of claims 1 to 8, characterized in that the swirl pulse triggered by the at least one pin and the holder provided therefor is compensated for on the molding compound by a swirl compensating guide device () which counteracts the swirl pulse Counter-twist initiates.

11. The device for carrying out the method according to one of claims 1 to 10, with an extrusion tool, from the nozzle mouthpiece a cylindrical rod with at least one inner, at least sectionally helical channel of predetermined cross-section can be pressed out, preferably inside the Nozzle mouthpiece (DM) at least one helically pre-twisted pin (40, 42) held on a nozzle mandrel is provided with an orientation which is coaxial to the axis (44) of the nozzle mouthpiece (DM), characterized in that the at least one pin (40, 42) rotatably and axially fixed to a shaft (30) rotatably mounted in the nozzle mandrel (70, 72) about an axis (44) parallel to the nozzle axis (44) and twisted in such a way that it runs along it its axis (44) flowing plastic mass (12) in the

REPLACEMENT LEAF Significantly applies a constant angular momentum defined by the pitch of its helix over the entire length.

12. The apparatus according to claim 11, characterized in that a device is provided with which at least one pin a fluid reducing the frictional force to the mass, in particular a fluid reducing the frictional force or liquid-like substance can be supplied.

13. The apparatus of claim 11 or 12, characterized gekenn¬ characterized in that the flow cross section within the nozzle mouthpiece (DM) is substantially constant, and that the flow or pressure ratios over the length of the nozzle mouthpiece (DM) by appropriate design of the cross section of Nozzle mouthpiece (DM) are kept constant or can be controlled in a targeted manner.

14. Device according to one of claims 11 to 13, characterized in that the at least one pin (40, 42) over the entire length of the nozzle mouthpiece (DM) has the same spiral pitch.

15. Device according to one of claims 11 to 14, characterized in that the fastening of the at least one pin (40, 42) to the shaft (30) via a cross section perpendicular to the flow direction or to the nozzle axis (44)) flat hub body (34; 234).

16. The device according to one of claims 11 to 15, characterized in that the connection between pin and shaft or the hub body (34; 134; 234) is in the inlet area (DME) of the nozzle mouthpiece (DM).

REPLACEMENT LEAF 3? 17. The apparatus according to claim 16, characterized in that the cross section of the nozzle mouthpiece (DM) in the region of the hub body (34; 134; 234) is substantially increased by the cross-sectional area of the hub body (34; 134; 234) such that the flow velocity of the plastic mass at the transition from the inlet area (DME) to the remaining flow section of the nozzle mouthpiece (DM) is kept essentially constant.

18. Device according to one of claims 15 to 17, characterized in that the at least one pin (40, 42) is extended beyond the hub body (134) in the upstream direction (140, 142).

19. The apparatus according to claim 18, characterized in that the extension piece (140, 142) of the at least one pin (40, 42) for supporting the rotary drive of the at least one pin (40, controlled by the mass flow within the nozzle mouthpiece (DM)) 42) is used.

20. Device according to one of claims 15 to 19, characterized in that the upstream end face (92) of the at least one pin (40, 42; 140, 142) is employed in the flow direction to support or control the angular momentum.

21. Device according to one of claims 15 to 20, characterized in that the hub body (234; 34) is designed as a helical surface with a helical pitch adapted to the pitch (WS) of the at least one pin (40, 42).

22. Device according to one of claims 15 to 21, characterized in that the inlet and / or the Auslauf¬ edge (54, 56) of the hub body (34) preferably in

REPLACEMENT LEAF 3Θ Matching to the inner contour of the nozzle mouthpiece (DM) and / or the attachment transitions to the pin (40, 42) is profiled such that the flow around the hub body (34) within the nozzle mouthpiece (DM) allows for minimal pressure fluctuations in the plastic mass occur.

23. Device according to one of claims 11 to 22, characterized in that the shaft (30) carrying the at least one pin (40, 42) in the nozzle mandrel (70, 72) has a radial dial bearing and an axial bearing (58, 60) Has.

24. The device according to claim 23, characterized in that the axial bearing and / or the radial bearing (58) is a roller bearing (60).

25 »Device according to one of claims 11 to 24, characterized in that the axial length of the nozzle mouthpiece (DM) and the pins (40,42) a fraction of the pitch (WS / 2) of the wire coil, preferably at least makes up at least half an incline.

26. Device according to one of claims 11 to 25, characterized in that the at least one pin (40, 42) has an axis of rotation (44) which coincides with the central axis (44) of the flow cross section.

27. The device according to one of claims 11 to 26, characterized in that a plurality of pins (40, 42) flow around the plastic mass, and that the pins have a common axis of rotation (44) and via the associated pitch circle (46) are evenly distributed.

28. Device for the continuous production of cylindrical rods with at least one inner channel, which runs at least in sections in a helical shape 33 predetermined cross-section, in particular for the manufacture of a sintered metal or ceramic blank for a tool part, with at least one pin projecting into the flow of the mass, which forms the at least one cooling channel when the mass flows through the nozzle mouth, in particular according to one of the claims 11 to 27, characterized in that the shaft (30) carrying the at least one pin (40, 42), the connection point to the pin lying radially inside the pin lies in the nozzle mouth, has an additional drive.

29. The device according to claim 28, characterized in that a device is provided with the at least one pin (440, 442; 440 ', 442'; 441 ") a fluid reducing the frictional force to the mass, in particular one the friction-reducing liquid or liquid-like substance can be supplied.

30. The device according to claim 28 or 29, characterized in that the at least one pin (440, 442;

440 ', 442'; 441 ") is flexible and the drive can be controlled depending on the desired gradient.

31. Device according to one of claims 11 to 30, characterized in that the substance reducing the frictional force through the rotatably mounted shaft (330; 430) and the connection point (392; 492; 492 '; 492 "992) to the at least one pin is guided onto the surface of the at least one pin that forms the cooling channel.

32. Apparatus according to claim 31, characterized in that the at least one pin has radial channels or through openings for the passage of the fluid reducing the frictional force. Ho

33. Device according to one of claims 28 to 32, characterized in that the fluid through the bearing (519) of the rotatable shaft (530) can be supplied.

34. Device according to one of claims 11 to 33, characterized in that in the region of the nozzle mouthpiece (DM) at least radially outside the at least one pin (40, 42) a flow guide surface arrangement (94) is provided for linearization or axial alignment of the mass flow , the flow guide surface arrangement preferably being formed in one piece with the inner wall of the nozzle mouthpiece (DM).

35. Apparatus according to claim 34, characterized in that the length of the flow guide surface arrangement (94) is limited to the region of the connection of the at least one pin (40, 42) to the shaft (30).

36. Device according to one of claims 32 to 35, characterized in that the flow guide surface arrangement (94) is formed by a toothing surface.

37. Apparatus according to claim 34, characterized in that the flow guide surface arrangement (641, 643, 645,

647; 741, 743, 745, 747) is arranged near the pitch circle of the relevant, assigned at least one pin and has a small radial extent.

38. Apparatus according to claim 37, characterized in that the flow guide surface arrangement is formed like a fin and is connected to the nozzle mandrel (618; 718).

39. Apparatus according to claim 34, characterized in that the flow guide surface arrangement of one of the

REPLACEMENT LEAF H l cooling channel former (930, 992, 940, 942) is formed on the swirl pulse compensating guide device (937, 935).

40. Apparatus according to claim 39, characterized in that the guide device (935, 937) is rotatably mounted in the nozzle (918).

41. Device according to one of claims 11 to 40, characterized in that the nozzle mandrel (70) ends in a predetermined and preferably adjustable distance (AX) in front of the nozzle mouthpiece (DM).

42. Device according to one of claims 11 to 41, characterized in that the nozzle mandrel (70, 72) is constructed in two parts, a part (70) supporting the shaft and sealing the bearing to the nozzle mouthpiece (DM) into a carrier body (72 ) can be used, preferably screwed in.

43. Device according to one of claims 11 to 42, characterized in that the at least one pin made of a material with a high modulus of elasticity, such as e.g. consists of steel or hard metal or ceramic material.

44. Cylindrical rod consisting of a plastic mass, in particular a plasticized powder-metallic or ceramic mass or produced in the extrusion process, with at least one internal channel of predetermined cross-section, at least in sections running helically, characterized in that the cross-section of the rod deviates from the circular shape.