EP2156909A2 - Method and device for producing fixing or connection components with radial outer contours, in particular screws or threaded bolts - Google Patents

Abstract

The method involves placing a blank with recesses (13) in a multi-sectional split mold by die stocks (15,16) provided with inner profiling formed in an outer contour. The opened die stocks are inserted in an initial condition, such that recesses are formed at the locations where the die stocks are opened. An independent claim is included for a device for executing the mounting or connecting unit manufacturing method.

Description

The invention relates to a method for producing fastening or connecting means with radial outer contours, in particular screws or threaded bolts, of metallic solid material, and a device intended for carrying out the method.

Screws or threaded bolts with diameters up to M36 consisting of solid metal material are mass-produced in a manner known per se by the cold extrusion method on multi-stage presses.

As a starting material wound on coils "wire" is used and prepared after appropriate pretreatment (uncoiling, dressing) in multi-stage presses, by forming operations (upsetting, reducing, trimming) of the screw blank.

In a so-called multi-stage press several tool units consisting of punch and die and auxiliary tools are arranged, in which the individual forming operations in a defined order, stepwise, are performed. For producing a screw blank starting from wire material, e.g. three compression stages required: compression, pre-forming of the screw head, final formation of the screw head. After the third stage, the finished screw blank is available. On these, the external thread is formed in a subsequent separate process by thread rolling or thread rolling without cutting. The surface of the threaded part is plastically deformed by the action of radial forces.

Also known are cold extrusion with integrated thread rolling machine.

Also known is the production of screws by hot pressing on forging presses. After being cut to length, the rod-shaped round material is fully or partially heated (in gas, oil or induction furnaces) to forging temperature (depending on the material, up to 1250 ° C.) and partially reshaped in presses. For the completion of such screws then usually machining processes (CNC turning, threading) are used, the threads are mainly without cutting on thread rolling machines (2- or 3-reel machines) are produced.

However, the hot pressing process is only suitable for small to medium quantities and diameters up to M200 and for materials that are difficult to form.

For the production of screws by the cold extrusion process and subsequent rolling of the external thread by means of thread rolling machines two separate forming processes are required. During the production of the screw blank on the cold extrusion press this is plastically deformed over the entire cross section. The generated material flow takes place on the shaft mainly in the axial direction and at the head in the radial direction. When rolling up the thread by means of a thread rolling machine, the required Deformation generated only on the surface by multiple rolling over, under radial force.

From the DE 197 23 634 A1 a method for the production of connecting screws for the furniture industry is known. From a wire blank, a rivet-shaped screw blank is produced by upsetting and extrusion in a multi-stage press with up to six stages. This is done in upsetting and extrusion press stations by means of suitable compression punches, which interact with associated dies. The finished screw blank is then fed to a thread rolling machine, on which the thread is rolled up by means of rolling jaws.

According to the known state of the art, two different machine systems, multi-stage press and thread rolling machine with different tools are required for the production of threaded screws. Multi-stage press and thread rolling machine require separate Antriebselnheiten due to the different force applications.

The machine systems required for the production of threaded screws are very costly in their procurement and maintenance.

The invention has for its object to provide a method for producing fastening or connecting means with radial outer contours, in particular screws or threaded bolts, which enables a more economical production, in particular on a multi-stage press. Furthermore, a device suitable for carrying out the method is to be provided.

According to the invention the object is achieved by the features specified in claim 1. Advantageous developments of the procedure are subject matter of claims 2 to 6. The device provided for carrying out the method is the subject of claim 7. Advantageous embodiments of the device are specified in claims 8 to 15.

From a blank of metallic solid material, such. a cut wire section, is prepared by one or more pressing operations, a prefabricated blank having a shaft-shaped portion on which a certain radial outer contour, preferably a thread to be formed. The number of extrusion stages depends both on the blank and on the geometry of the final product. In one of the upstream pressing stages (extrusion processes) a plurality of axially extending recesses are formed in the shaft-shaped portion at a fixed radial distance. In a further stage, the finished blank is inserted into a multi-part jaw tool with jaws that are open in the initial state, so that recesses extending in the axial direction are located at least at the locations where the jaws are open. The individual jaws of the pressing tool have on their inner side for forming the radial outer contour a corresponding inner profiling as a negative.

By closing the jaws by means of a radial force, the desired radial outer contour is pressed onto the shaft-shaped section of the finished blank. By the in the shaft-shaped portion of the blank molded recesses is prevented that material passes between the jaws of the baking tool during the pressing process. In the region of the recesses extending in the axial direction, no radial outer contour is produced during the pressing process.

The recesses may be arcuate or semi-circular. Their size depends on the size of the outer contour or thread to be formed.

The depth should be slightly greater than half the difference between the outer diameter and core diameter of the outer contour or the thread to be formed.

The width of the recesses should be at least as large as the opening gap between the jaws, when the jaws come into touching contact with the blank. For the formation of the recesses formed on the inside of the Schaftmatrize In their geometry correspondingly formed bead-shaped sections.

By pressing the outer contours and the consequent material flow in the radial direction, a solidification of the surface of the shaft-shaped portion is also achieved. The profiles produced in this way are characterized by a higher mechanical strength. The process steps for producing the fastening or connecting means with radial outer contours are preferably carried out within a multi-stage press.

By means of the proposed procedure, fastening or connecting means with radial outer contours can be produced in a particularly economical manner. Preferred field of application is the production of screws of all kinds and threaded bolts. The threads can be designed differently in their geometry. The term radial outer contours are understood to mean, besides threads, other profilings, such as e.g. individual grooves or undercuts, e.g. serve as locking aids for the fastening or connecting means. These can be arranged over the entire circumference of the shaft-shaped portion or even at certain locations. As attachment or connection means are those in question, which are screwed or einschlagbar. These include, for example, screw nails, groove nails, anchor nails or hooks.

According to a further embodiment, preferably the number of recesses formed in the shaft-shaped section and extending in the axial direction depends on the number of jaws of the jaw tool. In certain applications, it may also be appropriate to mold more recesses than jaws are present.

For example, six axially extending recesses may be formed in the shaft-shaped portion, whereby the blank is radially divided into six segments. In this case, a jaw tool with three jaws is provided for the subsequent pressing of the radial outer contours. The radial outer contours are then on the individual segments.

Depending on the shape of the fastening or connecting means to be produced, the shaft-shaped portion may be cylindrical or conical. The conical Training of the shaft takes place during one of the upstream pressing or compression stages within the multi-stage press.

While pressing the radial outer contour into the blank, it should be prevented from expanding in the longitudinal direction. For this purpose corresponding stop means are provided in the jaw tool.

The radial force component required for moving the jaws of the jaw tool can be generated by the applied pressing force of the slide arranged in the multi-stage press. This is an additional advantage, as can be dispensed with a separate drive for the closing and opening movement of the baking tool. The axial pressing force of the pressing carriage can be converted into a radial force component by means of one or more wedge-shaped or conical elements which act on the jaws of the baking tool. For this purpose, either the jaws or the wedge or conical elements are moved synchronously. To open the baking tool, the movement takes place in the opposite direction.

For certain applications, it may be expedient to heat the blank before pressing the outer contour, either half-warm, to temperatures of about 700 ° C, or warm, to temperatures of about 1200 ° C. The heating can take place directly in a heatable baking tool or in a separate upstream heating device.

A device suitable for carrying out the method is preferably designed as a multi-stage press which has a fixed tool carrier unit and a slide movable in the direction of the tool carrier unit, and at least one extrusion tool and a downstream baking tool with at least two radially movable pressing jaws which have a negative side on their inner side have radial profiling. The extrusion die consists of a head die and a shank die, with the shank die on the slide and the head die opposite to each other on the tool carrier unit. The shaft die has on its inner side at least two bead-shaped sections extending in the axial direction, which are arranged radially at the same distance as the opening gaps between the pressing jaws of the jaw tool. The device, in particular the jaw tool, is equipped with locking elements which prevent longitudinal expansion of the blank located in the tool during the closing movement of the pressing jaws. The jaw tool is connected to a drive unit for the radial movement of the pressing jaws in the closed and open position in conjunction.

The jaw tool can also be equipped with its own drive unit. However, in terms of machine technology, it is advantageous if the radial movement of the pressing jaws in the closed and open position is triggered by the movement of the carriage. The jaw tool can be arranged either on the tool carrier unit or the carriage. Similarly, the arrangement of head die and Schaftmatrize the extrusion tool can be changed.

On the carriage or on the tool carrier unit is an actuating element, via which the radial displacement of the pressing jaws can be triggered.

The jaw tool preferably consists of an outer ring in which the pressing jaws are mounted radially displaceable, wherein the lateral surfaces of the pressing jaws and the inner surface of the ring are conical or wedge-shaped, such that upon axial displacement of the ring or the pressing jaws, the pressing jaws In Closing and opening position are movable. Either the ring is stationary and the jaws additionally axially movable or the jaws are only radially movable and the ring axially displaceable. Depending on the structural design of the respective jaw tool, the ring can be made in one or more parts.

The triggering of the axial movement of the ring or the jaws via an actuating element, which is for example designed as an annular collar which engages one of the end faces of the pressing jaws or the outer ring. When the jaw tool is located on the tool carrier, the annular collar is arranged on the carriage or vice versa. On the inside of the Schaftmatrize also several bead-shaped sections can be arranged, the number of which is greater than the number of existing pressing jaws.

The extrusion tool can be equipped with ejectors, wherein at least one ejector as a forming die for forming an inner contour, e.g. as a hexagon socket of the screw head is formed. The movement of the ejector is controlled by a separate drive. The multi-stage press may also contain other pressing or upsetting tools and a shearing device for cutting the supplied wire.

Fig. 1

die einzelnen Verfahrensstufen zur erfindungsgemäßen Herstellung einer Innensechskant-Schraube in chronologischer Reihenfolge, In vereinfachter Darstellung,

Fig. 2

einen Schnitt gemäß der Linie B-B des Fließpresswerkzeuges (ohne Rohling) der Verfahrensstufe III In Fig. 1,

Fig. 3

einen Schnitt gemäß der Linie A-A des Gewindepresswerkzeuges der Verfahrensstufe IV in Fig. 1, bei geöffnetem Backenwerkzeug und

Fig. 4

einen Schnitt gemäß der Linie A-A des Gewindepresswerkzeuges der Verfahrensstufe IV in Fig. 1, bei geschlossenem Backenwerkzeug.

The invention is explained below using an exemplary embodiment for producing a hexagon socket screw. In the accompanying drawing show:

Fig. 1

the individual process stages for the inventive production of a hexagon socket screw in chronological order, in a simplified representation,

Fig. 2

a section along the line BB of the extrusion tool (without blank) of process stage III In Fig. 1 .

Fig. 3

a section along the line AA of the thread pressing tool of process stage IV in Fig. 1 , with open baking tool and

Fig. 4

a section along the line AA of the thread pressing tool of process stage IV in Fig. 1 , with closed jaw tool.

The In the Fig. 1 Process stages I to IV, which are illustrated in a simplified manner, for the production of a hexagon socket screw according to the invention are carried out within a multistage press, which is designed as a three-stage press. The not-shown multi-stage press has a machine frame with a sliding carriage 5 and a stationary tool carrier unit 6 in a known per se. In addition, a shear tool 1 (process step I) and two extrusion tools 2, 3 (process stages II and III) and a threaded die 4 ( Process stage IV) arranged. The two extrusion dies 2 and 3 each consist of a head die 2a, 3a and a Schaftmatrize 2b, 3b. The head matrices 2a and 3a are in the sliding carriage 5 and the opposite Schaftmatrlzen 2b and 3b arranged in the stationary tool carrier unit 6, wherein a reverse arrangement is possible.

In the process stage I, the wire 7 supplied as starting material is cut to a predetermined length by means of the shearing blade 1 and the cut wire section 8 is inserted into the mold cavity of the shank die 2b of the first extrusion tool 2 by means of a gripper or transport device not shown in detail. The mold cavity of the shank die 2b is limited in its depth by a first ejector 9 fitted in the shank die 2b. In the head die 2 a, a second ejector 10 is likewise arranged opposite the first ejector 9, by means of which the mold cavity of the head die 2 a is delimited. As a result of the movement of the carriage 5 in the direction of the stationary tool carrier unit 6, the inserted wire section is pre-compressed by a cold extrusion process in process stage II, forming a screw-head-like shape on the upper part of the wire section 8a. After completion of the process stage II and the movement of the carriage 5 in its starting position of the preformed screw blank 8a is moved by means of the ejector 9 and 10 to a gripper or transport device. The actuation of the ejector 9 and 10 by means of a separate drive unit, regardless of the movement of the carriage 5. The screw blank 8a is then inserted by means of the gripper or transport device in the mold cavity of the Schaftmatrize 3b of the second extrusion die 3. The mold cavity of the Schaftmatrize 3b and the head die 3a is analogous as in the first extrusion die 2 by ejector 11 and 12 limited. On the inside of the Schaftmatrize 3b are three extending in the axial direction bead-shaped portions 24 (FIG. Fig. 2 ), which are intended for forming the axially extending recesses 13 in the shaft-shaped portion of the screw blank 8a during the extrusion process in the process stage III. The bead-shaped sections 24 are arranged at a defined radial distance from each other, since the recesses 13 must be located at least at the points where the jaws of the subsequent threaded pressing tool 4 are open or close. By moving the carriage 5 in the direction of the stationary tool carrier unit 6, the preformed screw blank 8a is reshaped by another cold extrusion process in process stage III, whereby the screw head and the shank are given their final shape. By means of the upper evaluator 11, which also serves as a pressing die, the hexagon socket recess is formed in the head of the screw blank 8a. The finished screw blank 8b obtained after completion of process stage III has a shaft with three identical recesses 13 extending in the axial direction, which are arranged radially at a distance of 120 ° from each other. After completion of the process stage III, the carriage 5 is moved back to its original position.

After the extrusion die 3, a threaded die 4 is arranged in the tool carrier unit 6. In the example shown, this consists of an outer, displaceable in the axial direction ring 14, in which three jaws 15, 16, 17 are mounted radially movable.

The jaws 15, 16, 17 have on their inner side designed as a thread 18 Profillerung as a negative. The outer ring 14 is guided on a conical lateral surface 19 of the jaws 15, 16, 17, which tapers in the direction of the opening movement of the carriage 5. The outer ring 14 has one, with this corresponding, conical inner surface 20. In the open state of the jaw tool 4, the outer ring 14 projects beyond the in the direction of the carriage 5 facing end faces of the jaws. Opposite to the axially displaceable ring 14, a projecting annular collar 21 is arranged in the carriage 5, which acts on the adjacent end face of the ring 14 during the advancing movement of the carriage 5. During the feed movement of the carriage 5, the outer ring is moved in the axial direction, whereby the pressing jaws 15, 16, 17 are displaced for pressing the thread in the radial direction.

To realize the process step IV, the finished screw blank 8b is removed from the extrusion die 3 by means of the ejectors 10, 11 and placed in the open jaw tool 4 by means of a gripper or transport device. In this case, the screw blank 8b is positioned so that the three recesses 13 formed in the shank are located exactly at the point where the pressing jaws 15, 16, 17 are opened (opening gap 25), as in FIG Fig. 3 shown. In the carriage 5 is still a movable ejector 22 is arranged, which rests with one end in the hexagon recess of the screw head. Opposite this, a further movable ejector 23 is arranged in the tool carrier unit 6, which abuts against the end face of the shank of the screw blank 8b.

For pressing the thread in the shank of the screw blank 8b of the carriage 5 is delivered, while the outer ring 14 is displaced and formed on the effected radial movement of the pressing jaws 15, 16, 17, the thread 26. The two ejectors 22, 23 maintain their initial position during the thread pressing process and thus prevent an expansion of the screw blank 8b in the longitudinal direction during the pressing. Subsequently, the carriage 5 is moved back to its original position, the threaded press tool 4 is opened and ejected the finished screw.

The threaded press tool can also be designed differently in its design details. It is advantageous, however, if the opening and closing movement of the pressing jaws is realized by the movement of the carriage.

The individual process steps I to IV are synchronized in practical operation. The individual pressing tools are z. B. arranged in alignment in a row.

The number of cold extrusion stages preceded by the final thread pressing process is dependent on the shape and geometry of the fastening or connecting means to be produced in each case. Depending on the starting material used (metal wire), it may also be necessary to heat the screw blank before threading. The thread press tool can be equipped with an additional heating.

Claims (15)

Method for producing fastening or connecting means with radial outer contours, in particular screws or threaded bolts, made of solid metal material, characterized in that in a first pressing stage in a prefabricated blank having at least one shaft-shaped portion for an intended radial outer contour in the shaft-shaped portion more in the axial Direction extending recesses (13) are formed in a fixed radial distance, and in a second pressing stage of vorgefertlge blank with the recesses (13) In a multi-part jaw tool (4), the pressing jaws (15, 16, 17) with an outer contour forming Inside profiling are provided in the initial state open pressing jaws (15, 16, 17) is inserted so that at the points where the pressing jaws are open, recesses (13), and by closing the jaws by means of radial force acting on the shaft-shaped portion ready At least one radial outer contour is pressed in the blanks, wherein the recesses (13) extending in the axial direction prevent material from passing between the jaws of the jaw tool (4) during the pressing process. A method according to claim 1, characterized in that the number of axially extending recesses (13) depends on the number of jaws of the jaw tool (4) or is greater than the number of jaws of the jaw tool (4). Method according to one of claims 1 or 2, characterized in that the finished blank is prevented during the pressing of the radial outer contour at an extension in the longitudinal direction. Method according to one of claims 1 to 3, characterized in that the first and the second pressing step within a multi-stage press with a sliding carriage (5) and a stationary tool carrier unit (6), wherein for prefabrication of the blank used as a starting material metal wire (7) is cut to length and the cut wire section in stages, in one or more extrusion or compression stages, is converted to the blank. Method according to one of Claims 1 to 4, characterized in that the radial force component required for moving the jaws of the baking tool (4) is generated via the displacement of the carriage (5) effected in the multi-stage press. Method according to one of claims 1 to 5, characterized in that acts on the lateral surface of the jaws of the baking tool at least one axially displaceable wedge or cone-shaped element, via which by means of the movable carriage of the multi-stage press the closing and opening movement of the baking tool. Device for carrying out the method according to one of claims 1 to 6, characterized in that it comprises at least one extrusion tool (3) and a downstream jaw tool (4) with at least two radially movable pressing jaws (15, 16, 17) on its inner side a formed as a negative radial profiling (18) comprises, the Fileßpresswerkzeug (3) consists of a head die (3a) and a Schaftmatrize (3b) having on its inner side at least two axially extending bead-shaped portions (24) radially At the same distance as the opening gaps (25) between the pressing jaws (15, 16, 17) of the baking tool (4) are arranged. Apparatus according to claim 7, characterized in that it is equipped with locking elements (22, 23) which prevent a longitudinal expansion of the blank (8b, 23) during the closing movement of the pressing jaws (15, 16, 17). Apparatus according to claim 7 or 8, characterized in that the extrusion press tool (3) and jaw tool (4) within a multi-stage press with a fixed tool carrier unit (6) and in the direction of the tool carrier unit (6) movable carriage (5) are arranged, wherein the one Die (3 a) of the extrusion die (3) on the carriage (5) and the other die (3b) opposite to the tool carrier unit (6) is arranged. Device according to one of claims 7 to 9, characterized in that the jaw tool (4) with a drive unit for the radial movement of the pressing jaws (15, 16, 17) in the closed and open position is in communication. Device according to one of claims 7 to 10, characterized in that the jaw tool (4) is mounted either on the tool carrier unit (6) or the carriage (5) and on the carriage (5) or on the tool carrier unit (6) an actuating element (21 ) is arranged, over which the pressing jaws (15, 16, 17) are radially displaceable. Device according to one of claims 7 to 11, characterized in that the jaw tool (4) consists of a single or multi-part outer ring (14) in which the pressing jaws (15, 16, 17) are mounted radially displaceable, wherein the lateral surfaces (19) of the pressing jaws 15, 16, 17) and the inner surface of the ring (14) are cone-shaped, such that upon axial displacement of the ring (14) or the pressing jaws (15, 16, 17) the pressing jaws (15, 16 , 17) are movable in the closed and open position. Device according to one of claims 7 to 12, characterized in that on the inner sides of the Schaftmatrize (3b) extending in the axial direction a plurality of bead-shaped portions (24) are arranged, the number of which is greater than the number of existing pressing jaws. Device according to one of claims 7 to 13, characterized in that the bead-shaped portions (24) are arcuate, and whose maximum radial extent is slightly greater than half the difference between the outer diameter and core diameter of the outer contour to be formed. Device according to one of claims 7 to 14, characterized in that the width of the bead-shaped portions (24) is at least as large as the opening gap (25) between the pressing jaws (15, 16, 17), in the state when the jaws in touching contact get to the blank (8b).

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