EP2603335B1 - Process and device for the manufacture of solid self-piercing rivets - Google Patents

Description

The invention relates to a method for producing a full punch rivet according to claim 1. The invention further relates to a tool for producing a full punch rivet according to claim 5.

Punched rivets are used to join flat workpieces, especially sheet metal. The punch rivet is pressed with the simultaneous formation of two punched holes with its shaft through the workpieces. Near its shank end, the shank has at least one shank groove in which the material of the lower workpiece seen in the punching direction is pressed during the punching process.

Such punch rivets are set in particular in the automotive sector via automated Nietsetz devices (so-called rivet eyes) through the workpieces, such as in the DE 10 2004 011 846 A1 disclosed. In order to be able to ensure the required small dimensional tolerances, such punch rivets are manufactured in the prior art by machining processes, in particular by means of turning. However, these methods prove to be very costly, which is partly due to the increased loss of material.

It was therefore proposed to produce a stamped embossment using at least one pressing operation in cold forming. For this purpose, it has been proposed to first produce a rivet blank using a press and subsequently to introduce in a second process step by a rolling or rolling process, in particular with a flat jaw or round jaw rolling machine, the at least one shank groove necessary for the riveting process. However, a reworking of the method only slightly described has revealed that this is not only designed to be very expensive and costly. In addition, the consistent dimensional stability required for an automated processing process could not be achieved.

Furthermore, in the DE 10 2011 009 649 A1 , on which the preamble of claims 1 and 5 is based, mentions the production of a punch rivet by means of forming. An apparatus and a method for generating a profiling on a fastener is in the DE 10 2004 05 638 B disclosed. The US 5,296,317 discloses a similar method but for cold-forming battery poles.

The invention aims to remedy this situation. The invention is based on the object to provide a method for producing a Vollstanzniet, which allows a cost-effective production of a full punch rivet at a consistently high dimensional accuracy. According to the invention, this object is solved by the features of claim 1.

With the invention, a method for producing a solid rivet is created, which allows the cost-effective production of a full punch rivet while maintaining high dimensional accuracy. Due to the clamping of the piece of wire between the cheek-like, radially adjustable moldings, which depict the Nietumfangskontur and the subsequent application of the wire piece at its two ends via a respective pressure pin with an axial force, the wire material is temporarily placed in a pseudo-liquid state, whereby the material in the The peripheral contour formed by the fittings flows and fills them. It has been shown that in this way a high dimensional stability is achieved.

The piece of wire is pre-compressed prior to clamping in the die by means of a second tool comprising a second die and a second punch. As a result, a Vorkonturierung the piece of wire is achieved.

The pre-upset wire piece is further advanced in the second die of the second tool by means of the first punch, with a radially projecting head being formed at one end of the wire piece. As a result, an exact axial positioning of the preformed piece of wire between the baking-like shaped pieces of the die of the first tool is possible. The geometry corresponds to the bottom of the head preferably of the geometry of the rivet head outlet of the Nietumfangskontur formed by the fittings.

In a further development of the invention, the further compressed wire piece between the radially engageable fittings of the die is positioned before it is clamped between the fittings, wherein the molded head rests axially on the fittings. As a result, a constant axial positioning of the wire pieces is achieved, whereby a constant dimensional accuracy of the finished solid punch rivet is ensured.

In a further embodiment of the invention, the radially engageable fittings are conically guided axially and the fittings are moved axially by the first punch, whereby the piece of wire is clamped between the fittings. This achieves an integrated clamping and forming process.

The present invention is further based on the object to provide a tool for producing a full punch rivet by means of the aforementioned method, so that a cost-effective production of a full punch rivet is possible with constant dimensional accuracy. According to the invention, this object is achieved by a tool having the features of patent claim 7.

With the invention, a tool for producing a full punch rivet by means of the aforementioned method is provided, which allows a cost-effective production of a full punch rivet with constant dimensional accuracy. The peripheral shape of the tool is formed by at least three fittings, which are guided radially adjustable and together form the peripheral shape. The at least one undercut forming an annular groove causes a circumferential ridge of the solid punch rivet produced. This circumferential ridge in turn, together with the rivet foot, defines a circumferential groove into which the material of the sheet to be joined, which is plastically deformed during the punching process, penetrates. By the bias of the fittings via spring elements in the direction of the largest cone diameter of the Frame element, the fittings are arranged spaced apart in the unloaded state, such that a simple positioning of the piece of wire to be deformed is possible. When the shaped pieces are subjected to an axial force, they are moved axially in the direction of the smallest cone diameter of the frame element, as a result of which the shaped pieces are set radially against the wire piece via the conical shape of the leadthrough. As a result, a clamping of the piece of wire between the fittings is achieved.

The punch has an outer axially displaceable punch part which is coaxially penetrated by an inner axially displaceable pressure pin, wherein the outer punch part has a conical shoulder, which corresponds with the conical feedthrough enlarged diameter at its diameter. In this way, a two-stage Anstellprozess allows, initially the outer punch member causes axial movement of the mold pieces of the die, whereby a clamping of the piece of wire is achieved. Subsequently, a force is applied to the piece of wire via the inner pressure pin. In this case, the outer stamp member is biased in the punch via a spring. As a result, a gentle, spring-loaded hiring of the outer punch part is made possible on the fittings.

The inner pressure pin can be positioned relative to the outer punch part in such a way that the two punch parts delimit a receptacle for the head of a pre-compressed rivet. As a result, a gripper function is effected, which allows a transport of a pre-compressed rivet from a pre-upsetting die in the die of the tool.

In a development of the invention, the frame element has at least three holes which open radially into the conical feedthrough and in which pins for axial guidance of the shaped pieces are introduced. As a result, an axially guided movement of the fittings is effected with axial application of force.

In a further embodiment of the invention, the fittings have lateral bores for receiving guide pins, via which the fittings are connected to each other. As a result, a guided radial adjustment of the fittings is effected on the wire piece.

• Fig. 1 die schematische Darstellung eines Werkzeugs zur Herstellung eines Vollstanznietes im Querschnitt:
  1. a) Matrize mit vier Formstücken;
  2. b) Stempel (Position "ausgefedert");
  3. c) Stempel (Position "eingefedert")
• Fig. 2 die schematische Darstellung des Formstückeinsatzes der Matrize aus Figur 1
  1. a) im Querschnitt;
  2. b) in der Draufsicht mit eingesetzten Formstücken;
  3. c) im Schnitt A-A der Figur a);
• Fig. 3 die schematische Darstellung der Formstücke der Matrize aus Figur 1
  1. a) in der Draufsicht;
  2. b) im Schnitt A-A der Figur a);
  3. c) im Schnitt B-B der Figur b);
  4. d) im Schnitt C-C der Figur c)
  5. e) in räumlicher Einzeldarstellung;
• Fig. 4 die schematische Darstellung eines Vorstauchwerkzeuges im Querschnitt:
  1. a) Matrize;
  2. b) Stempel (Position "Drahtabschnitt einsetzen");
  3. c) Stempel (Position "Vorstauchen");
• Fig. 5 die schematische Darstellung eines abgelenkten Drahtstücks
  1. a) vor der Verformung;
  2. b) nach erstem Vorstauchen;
  3. c) nach zweitem Vorstauchen;
  4. d) nach Fertigstauchen.

Other developments and refinements of the invention are specified in the remaining subclaims. An embodiment of the invention is illustrated in the drawing and will be described in detail below. Show it:

• Fig. 1 the schematic representation of a tool for producing a solid rivet in cross section:
  1. a) template with four fittings;
  2. b) punch (position "rebounded");
  3. c) stamp (position "compressed")
• Fig. 2 the schematic representation of the fitting insert of the die FIG. 1
  1. a) in cross-section;
  2. b) in plan view with inserted fittings;
  3. c) in section AA of Figure a);
• Fig. 3 the schematic representation of the fittings of the die FIG. 1
  1. a) in plan view;
  2. b) in section AA of Figure a);
  3. c) in section BB of Figure b);
  4. d) in section CC of FIG.
  5. e) in a single spatial representation;
• Fig. 4 the schematic representation of an upsetting tool in cross section:
  1. a) template;
  2. b) punch (position "insert wire section");
  3. c) stamp (position "pre-dipping");
• Fig. 5 the schematic representation of a deflected piece of wire
  1. a) before deformation;
  2. b) after first screening;
  3. (c) after second screening;
  4. d) after finishing.

The tool 1 chosen as an exemplary embodiment for producing a full punch rivet is essentially formed by a die 2, which accommodates a fitting insert 3, and a punch 4.

The die 2 consists essentially of a socket 21 which receives a fitting insert 3. The fitting insert 3 abuts against an intermediate sleeve 22, in which a pressure pin 23 is arranged. The pressure pin 23 is held by two thrust pin receptacles 231, between which a coil spring 25 is arranged. The pressure pin 23 abuts against a pressure piece 24, which is in communication with an ejector pin 29 and bears against a clamping screw 27 for adjusting the spring tension of the disk spring assembly 26. The clamping screw 27 in turn abuts a rear bearing 28, through which the ejector pin 29, which also penetrates the clamping screw 27, is guided. The intermediate sleeve 22 has a substantially T-shaped cross-section and is biased by a plate spring 6 against the fitting insert 3, which bears against the rear bearing 28.

The molding insert 3 is formed by a substantially cylindrical retaining ring 31, which is provided with an axial, tapered passage 311. Surrounding each are offset by 90 degrees to each other in the retaining ring 31 four holes 312 introduced, which open into the bushing 311.

In the conical feedthrough 311, a rivet mold 32 is used, which is formed from four fittings 33. The rivet mold 32 defines a rivet peripheral contour 321, which has an annular groove 322 forming an undercut. Farther the Nietumfangskontur 321 includes the contour of the rivet head 323 and the Nietfußes 324. Outside are in the shell of the rivet 32 each offset by 90 degrees to each other four keyways 325 introduced. In the middle of the splines 325 is in each case the parting plane in each case two adjoining shaped pieces 33. The shaped pieces 33 are each provided at their parting surfaces with a bore 331 for receiving a guide pin 35. The rivet 32 is axially guided in the passage 311 of the retaining ring 31 via locking pins 34 which engage in the keyways 325.

The punch 4 consists essentially of a cup-shaped socket 41, which is penetrated by an insert 42, wherein the insert 42 has a circumferential edge 420 which rests against the bottom edge 410 of the socket 41. The insert 42 is followed by an intermediate bushing 43, which receives a pressure pin 46, which opens into a bore 422 introduced axially through the insert 42. The pressure pin 46 is held in the intermediate sleeve 43 via a pressure pin receptacle 461, wherein between the pressure pin receptacle 461 and the insert 42 the pressure pin 46 surrounding a coil spring 47 is arranged, via which the insert 42 is biased against the socket 41. The pressure pin 46 is applied to a pressure piece 48, which in turn opens into a clamping screw 45. Between the clamping screw 45 and a T-shaped cross-section intermediate bushing 43 a Tellerfedempaket 44 is arranged, via which the intermediate sleeve 43 is biased against the insert 42. The bias is adjustable via the clamping screw 45, which in turn rests against the rear layer 39.

For producing a full punch rivet, an expanding tool is also used in the exemplary embodiment, as is shown in FIG FIG. 4 is shown schematically. The pre-upsetting tool 5 is formed from a second die 6 and a second punch 7.

The second die 6 consists essentially of a socket 61, which receives a mold core 62 which is surrounded by a sleeve 63. Mold core 62 and Sleeve 63 abut against a support core 64, which receives a pressure piece 66 against which an ejector pin 65 abuts, which opens into the mold core 62. The mandrel 62 has the shape contour 621 of the wire piece 8 to be pre-clinched.

Support core 64 and thrust piece 66 are applied to the rear layer 67, which is penetrated by an ejector pin 68 which bears against the pressure piece 66. At its end opposite the pressure piece 66, the ejector pin 68 is held in a receptacle 69.

The second punch 7 of the pre-upsetting tool 5 consists essentially of a pre-upsetter 71, which receives a pressure piece 73, against which a pressure pin 72 abuts, which projects out of the pre-upsetter 71. The pressure member 73 is biased by a coil spring 74 against the pre-diver 71, which rests together with the pre-diver on a rear 75.

To produce a full punch rivet, a wire piece 8 is first cut to length, which is inserted into the second die 6 of the pre-upsetting tool 5 so that it rests on the ejector pin 68 in the mandrel 62. Subsequently, the second punch 7 is placed with the pre-upsetter 71 on the second die 6, wherein the pressure pin 72 rests on the wire piece 8. Subsequently, the wire piece 8 is acted upon by the pressure pin 52 in such an axial force that this is pre-dipped into the mold contour 621 of the mandrel 62. The shape of the pre-bent wire piece 81 is shown in FIG FIG. 5 b) shown.

The second punch 7 is now removed from the second die 6 of the pre-upsetting tool 5 and the punch 4 of the tool 1 is positioned on the second die 6 of the pre-upsetting tool 5, so that the pressure pin 46 of the punch 4 rests on the preformed rivet 81. Subsequently, an axial force is applied to the pre-upset rivet 81 via the pressure pin 46, wherein the rivet head 831 is preformed. The shape of the thus pre-compressed piece of wire 82 is in FIG. 5c) shown. The thus pre-compressed wire piece 82 is now on the ejector pin 68 with its rivet head 831 in the bore 422 of the insert 42nd of the punch 4, wherein the pressure pin 46 is moved back within the punch 4. The pre-compressed wire piece 82 is now held in the formed by the bore 422 of the insert 42 and the pressure pin 46 recording.

The pre-compressed wire piece 82 is subsequently positioned by means of the punch 4 between the shaped pieces 33 of the rivet mold 32. In this case, the conical shoulder 421 of the insert 42 bears against the shaped pieces 33 and presses them against the spring force of the helical spring 25 along the conical leadthrough 311 in the direction of the intermediate sleeve 22 of the die 2, whereby the shaped pieces 33 are radially applied to the pre-compressed wire piece 82. In this way, the pre-formed wire piece 82 is clamped between the mold pieces 33, wherein the preformed rivet head 831 rests on the shaped pieces 33. The geometry of the underside of the preformed rivet head 831 corresponds to the geometry of the rivet head-side outlet of the rivet peripheral contour 321 formed by the shaped pieces 33 and rests on this.

Subsequently, a continuous force is exerted on the pre-compressed wire piece 82 by the pressure pin 46 of the punch 4 as well as by the pressure pin 23 abutting the other end of the pre-compressed wire piece 82 until its material begins to flow and the rivet peripheral contour 321 of the rivet mold 32 fills. The completed solid rivet 83 now has the in FIG. 5 d) the reproduced form. Due to the material flowed into the annular groove 322 of the rivet mold 32, a peripheral web 834 is formed here, which, together with the rivet foot 833, delimits a peripheral groove 835.

The punch 4 is now removed from the die 2, wherein the shaped pieces 33 are moved by the restoring force of the coil spring 25 via the pressure pin receptacle 231 along the conical passage 311 of the retaining ring 31 upwards. As a result, the shaped pieces 33 are moved apart, whereby the finished Vollstanzniet 83 is released. The released Vollstanzniet 83 is now ejected via the pressure pin 23 from the die 2.

Claims (7)

1. Process for the manufacture of a solid self-piercing rivet, where a piece of wire (8) cut to the correct length is formed by a tool (1) comprising a punch (4) and a die (2), characterised in that the length of wire (8) is clamped between jaw-like radially adjustable moulding elements (33) which form the circumferential contour (321) of the rivet and which have at least one ring groove (322) to form an undercut, following which the length of wire (8) is subjected to an axial force by a pressure pin (23, 46) at either end which causes the length of wire to flow into and fill the circumferential contour of the rivet formed by the moulding elements (33), where the length of wire (8) before being clamped into the die (2) is pre-compressed by a second tool (5) comprising a second die (6) and a second punch (7), and the pre-compressed length of wire (82) continues to be compressed in the second die (6) by the first punch (4), thereby forming a radially projecting head (831) at one end of the length of wire (8).
2. Process in accordance with claim 1, characterised in that the compressed length of wire (82) is positioned between the radially adjustable moulding elements (33) of the die (2) before being clamped between the moulding elements (33), where the previously shaped head (831) lies axially against the moulding elements (33).
3. Process in accordance with either of the aforementioned claims, characterised in that the radially adjustable moulding elements (33) are guided conically in the axial direction and that the moulding elements (33) are moved axially by the first punch (4), thereby clamping the length of wire (8) between the moulding elements (33).
4. Process in accordance with any of the aforementioned claims, characterised in that the length of wire (8) is formed in the cold state.
5. Device for manufacturing a solid self-piercing rivet using a process in accordance with any of the aforementioned claims, comprising a die (2) and a punch (4) which is moved axially towards the die (2), characterised in that the die (2) is formed by a frame element (31) with a conical passage (311) in which at least three moulding elements (33) are guided for radial adjustment, which delimit the circumferential contour (321) of a rivet and have at least one ring groove (322) forming an undercut, where the moulding elements (33) are pre-loaded by spring elements (44) in the direction of the large diameter of the cone of the frame element (31), where the stamp (4) has an outer axially movable punch section (42) which is penetrated co-axially by an inner axially movable pressure pin (46), where the outer punch section (42) has a conical shoulder (421) which corresponds to the end of the conical passage (211) with the larger diameter, where the outer section (42) in the punch (4) is pre-loaded by a spring (26), where the inner pressure pin (46) is pre-loaded by a spring against the outer punch section (42) and where the inner pressure pin (46) can be positioned in relation to the outer punch section (42) in such a way that the two sections of the punch form the limits of a seat for the head of a pre-compressed rivet (82).
6. Device in accordance with claim 5, characterised in that the frame element (31) has at least three radial bores (312) running into the conical passage (311) in which pins for the axial guidance of the moulding elements (33) are arranged.
7. Device in accordance with claim 5 or claim 6, characterised in that the moulding elements (33) have lateral bores to receive guiding pins, by means of which the moulding elements are connected to one another.

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