CA2666551A1 - Method and device for producing a screw connection point - Google Patents
Method and device for producing a screw connection point Download PDFInfo
- Publication number
- CA2666551A1 CA2666551A1 CA002666551A CA2666551A CA2666551A1 CA 2666551 A1 CA2666551 A1 CA 2666551A1 CA 002666551 A CA002666551 A CA 002666551A CA 2666551 A CA2666551 A CA 2666551A CA 2666551 A1 CA2666551 A1 CA 2666551A1
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- CA
- Canada
- Prior art keywords
- hollow profile
- attachment
- punch
- electrode
- connection point
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/002—Resistance welding; Severing by resistance heating specially adapted for particular articles or work
- B23K11/004—Welding of a small piece to a great or broad piece
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D26/00—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces
- B21D26/02—Shaping without cutting otherwise than using rigid devices or tools or yieldable or resilient pads, i.e. applying fluid pressure or magnetic forces by applying fluid pressure
- B21D26/033—Deforming tubular bodies
- B21D26/035—Deforming tubular bodies including an additional treatment performed by fluid pressure, e.g. perforating
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D28/00—Shaping by press-cutting; Perforating
- B21D28/24—Perforating, i.e. punching holes
- B21D28/28—Perforating, i.e. punching holes in tubes or other hollow bodies
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/30—Features relating to electrodes
- B23K11/3081—Electrodes with a seam contacting part shaped so as to correspond to the shape of the bond area, e.g. for making an annular bond without relative movement in the longitudinal direction of the seam between the electrode holder and the work
Abstract
The invention relates to a method and a device for producing a screw connection point (1) on the periphery (34) of a hollow section (7), that is expanded by a high-pressure fluid. An attachment (17, 31) comprising a bore (18) with an inner thread is mounted on the hollow section (7) in the hydroforming mould (2) and a hole is then made in the hollow section (7) in alignment with the bore (18). The aim of the invention is to produce a durable screw connection point (1) on the periphery (34) of a hollow section (7) in a simple and reliable process. To achieve this, the attachment (17, 31) is advanced towards the hollow section (7) with the aid of an electrode (11, 30) that is integrated into the hydroforming mould (2). The attachment (17, 31) is resistance welded to the hollow section (7) by means of the electrode (11, 30), once said attachment has been placed on the mould relief (5) in the vicinity of the screw connection point (1) to be created.
Description
METHOD AND DEVICE FOR PRODUCING
A SCREW CONNECTION POINT
The invention relates to a method for producing a screw connection point, according to the preamble of claim 1, and to a device for executing the method, according to the preamble of claim 7.
A method of the generic type, or a device of the generic type, is known from DE
197 33 477 Al. In that case, a punch having a central bore, in which a stamping punch is guided, is integrated into a hydroforming tool. The free end of the stamping punch projects beyond the end of the punch in which it is received, an attachment having a through opening being threaded onto the end of the stamping punch. When the stamping punch is in the position of non-use, the free end terminates flush with the side of the attachment that faces away from the receiving punch. The punch, for its part, is displaceably guided in a guide bore in the hydroforming tool, which guide bore opens into the die relief of the forming tool, which die relief delimits a forming cavity. There is inserted in the forming cavity a hollow profile blank, which, after the hydroforming tool has been closed, is expanded, through the generation of a fluidic inner high pressure, until it bears on the die relief of the hydroforming tool in a true-to-contour manner, thereby creating the wanted form of the hollow profile. The punch, together with the piercing punch and the attachment, is then moved towards the hollow profile, as a result of which the latter becomes impressed, such that there is realized a pocket having approximately the dimensions of the attachment. Owing to the continued action of the fluidic inner high pressure, the wall of the hollow profile bears intimately on the outside of the attachment, and binds the latter in the wall of the hollow profile.
Finally, in the position assumed by the receiving punch, the piercing punch is moved further forwards, as a result of which the hollow profile is pierced through by the attachment, which has an internal thread. The hole slug falls into the interior of the hollow profile.
An attachment joined in such manner to a hollow profile is subject to relatively large tensile forces, however, it being possible for this attachment to become detached from the pocket. In this case, the screw connection point is destroyed.
The invention is based on the object of so developing a method of the generic type that the production of a durable screw connection point on the periphery of a hollow profile is rendered possible in a manner that is simple and reliable in respect of the process. Furthermore, a device for executing the method is to be specified.
The object is achieved, according to the invention, by the features of claim 1 in respect of the method, and by the features of claim 7 in respect of the device.
The resistance welding of the attachment, which carries an internal thread, onto the hollow profile creates an extremely durable screw connection point, which also withstands large mechanical stresses in the tensile and compressive directions.
Owing to the fact that the electrode simultaneously guides the attachment up to the site where the welded connection point is to be effected, production of the screw connection point is rendered simpie in respect of the economy of the process. Owing to the attachment being arranged in a receiving cavity constituted by the electrode and its guide bore, it can be positioned on the hollow profile in a defined, reliable, precise and, above all, reproducible manner. This applies irrespective of the production tolerances of the attachment, since the electrode is integrated within the hydroforming tool, and the electrode thus always approaches the same point on the hollow profile upon each new welding operation. The forming by expansion results in the hollow profile bearing on the attachment in a true-to-contour manner, as a result of which the joint surface extends over the entire side of the attachment that faces towards the hollow profile, and thus guarantees maximum hold. The mutual bearing contact is thus not localized, but planar. Furthermore, in the case of mechanical stresses the introduction of force is distributed, as a result of which these stresses can be better absorbed by the hollow profile, and the screw connection point remains undamaged. Since the operation of guiding-up and positioning the attachment is assumed by the electrode, there is no need for additional tools respectively serving one of these purposes. Owing to the electrodes of the resistance welding facility being integrated into the hydroforming tool, the amount of required equipment is reduced and there is a substantial saving in structural space. In addition, there is no need for the attachment to be clasped mechanically by the hollow profile, which would result in a thinning of material on the hollow profile.
Consequently, in the case of the screw connection point according to the invention, there is no susceptibility to cracking, particularly on the hollow profile, during the joining operation, a high process reliability being ensured in the case of the production method according to the invention.
A SCREW CONNECTION POINT
The invention relates to a method for producing a screw connection point, according to the preamble of claim 1, and to a device for executing the method, according to the preamble of claim 7.
A method of the generic type, or a device of the generic type, is known from DE
197 33 477 Al. In that case, a punch having a central bore, in which a stamping punch is guided, is integrated into a hydroforming tool. The free end of the stamping punch projects beyond the end of the punch in which it is received, an attachment having a through opening being threaded onto the end of the stamping punch. When the stamping punch is in the position of non-use, the free end terminates flush with the side of the attachment that faces away from the receiving punch. The punch, for its part, is displaceably guided in a guide bore in the hydroforming tool, which guide bore opens into the die relief of the forming tool, which die relief delimits a forming cavity. There is inserted in the forming cavity a hollow profile blank, which, after the hydroforming tool has been closed, is expanded, through the generation of a fluidic inner high pressure, until it bears on the die relief of the hydroforming tool in a true-to-contour manner, thereby creating the wanted form of the hollow profile. The punch, together with the piercing punch and the attachment, is then moved towards the hollow profile, as a result of which the latter becomes impressed, such that there is realized a pocket having approximately the dimensions of the attachment. Owing to the continued action of the fluidic inner high pressure, the wall of the hollow profile bears intimately on the outside of the attachment, and binds the latter in the wall of the hollow profile.
Finally, in the position assumed by the receiving punch, the piercing punch is moved further forwards, as a result of which the hollow profile is pierced through by the attachment, which has an internal thread. The hole slug falls into the interior of the hollow profile.
An attachment joined in such manner to a hollow profile is subject to relatively large tensile forces, however, it being possible for this attachment to become detached from the pocket. In this case, the screw connection point is destroyed.
The invention is based on the object of so developing a method of the generic type that the production of a durable screw connection point on the periphery of a hollow profile is rendered possible in a manner that is simple and reliable in respect of the process. Furthermore, a device for executing the method is to be specified.
The object is achieved, according to the invention, by the features of claim 1 in respect of the method, and by the features of claim 7 in respect of the device.
The resistance welding of the attachment, which carries an internal thread, onto the hollow profile creates an extremely durable screw connection point, which also withstands large mechanical stresses in the tensile and compressive directions.
Owing to the fact that the electrode simultaneously guides the attachment up to the site where the welded connection point is to be effected, production of the screw connection point is rendered simpie in respect of the economy of the process. Owing to the attachment being arranged in a receiving cavity constituted by the electrode and its guide bore, it can be positioned on the hollow profile in a defined, reliable, precise and, above all, reproducible manner. This applies irrespective of the production tolerances of the attachment, since the electrode is integrated within the hydroforming tool, and the electrode thus always approaches the same point on the hollow profile upon each new welding operation. The forming by expansion results in the hollow profile bearing on the attachment in a true-to-contour manner, as a result of which the joint surface extends over the entire side of the attachment that faces towards the hollow profile, and thus guarantees maximum hold. The mutual bearing contact is thus not localized, but planar. Furthermore, in the case of mechanical stresses the introduction of force is distributed, as a result of which these stresses can be better absorbed by the hollow profile, and the screw connection point remains undamaged. Since the operation of guiding-up and positioning the attachment is assumed by the electrode, there is no need for additional tools respectively serving one of these purposes. Owing to the electrodes of the resistance welding facility being integrated into the hydroforming tool, the amount of required equipment is reduced and there is a substantial saving in structural space. In addition, there is no need for the attachment to be clasped mechanically by the hollow profile, which would result in a thinning of material on the hollow profile.
Consequently, in the case of the screw connection point according to the invention, there is no susceptibility to cracking, particularly on the hollow profile, during the joining operation, a high process reliability being ensured in the case of the production method according to the invention.
In a particularly preferred development of the invention, according to claim 2, the welding is effected before the piercing. Pressure fluid is thereby prevented from reaching the welding point, which can impair the quality of the welding operation.
Additionally achieved is the fact that, in the production of the screw connection point, there is no premature drop in pressure, which might possibly occur upon piercing and, owing to the pressure of the electrode, result in a sink point on the hollow-profile. Such a sink point is disadvantageous to full-surface welding of the attachment onto the hollow profile. Moreover, the attachment has already been immovably located on the hollow profile at a particularly early point in time, such that there can be no difficulties whatsoever in positioning the attachment in relation to the hollow profile. In the case of very rapidly succeeding process steps of welding and piercing, there additionally ensues the advantage that the welding heat following the welding operation is at least partially concentrated on the welding point, as a result of which the hollow profile material is still readily formable and workable in the region of the screw connection point. The result of this is that the process step of piercing is facilitated, owing to the relative softness of the hollow profile material caused by the heat.
In a further particularly preferred development of the invention, according to claim 3, the hollow profile is pierced through the bore of the attachment. Achieved thereby is a taught guidance of the piercing punch, as a result of which the latter always impacts the hollow profile at the correct point. Very high production accuracies are thereby achieved for the screw connection points.
In an alternative preferred development of the method according to the invention, according to claim 4, the attachment is pressed into the hollow profile wall by means of the electrode. The attachment, which has an end-face cutting geometry, itself produces the hole in the hollow profile wall. Welding to the hollow profile is then effected. In the case of this variant of the invention, the attachment attains its exact position relative to the hollow profile as it is pressed into the hollow.profile wall. The preliminary, but precise locating of the attachment on the hollow profile and the simultaneous creation of a hole by the attachment simplify the entire production process, since there is almost no more need for the attachment to be held in its pressing-in location and pressed onto the hollow profile. The production process is accelerated, since creation of the hole is already effected at the point in time at which the attachment is positioned on the hollow profile. Since the attachment has already been pressed into the hollow profile wall, there is no need for any additional mechanical welding pressures to be applied upon the subsequent, final locating of the attachment to the hollow profile by resistance welding, this in turn simplifying the welding equipment, since there are no corresponding pressing devices. In order to keep the hollow profile as tight as possible upon being pierced, the stub, realized on the attachment, that is pressed in has a shape having a slight conical taper towards the interior of the hollow profile. In the case of the corresponding advantageous development of the device, according to the invention, as claimed in claim 9, the electrode itself constitutes the punch, the attachment bearing on the end face of the latter.
As already stated, the attachment has a cutting geometry that faces towards the hollow profile. The electrode in this case does not constitute a piercing punch per se, but a punch that can press the attachment into the hollow profile. There is no separate piercing punch whatsoever, since the cutting geometry is advantageously provided on the attachment itself, and the latter thereby assumes the function of the piercing punch. The absence of the piercing punch additionally simplifies the control of the device for producing the screw connection point.
In a preferred development of the invention, according to claim 5, the piercing is effected from the outside inwards, through material displacement of the hollow profile material. Based correspondingly thereon, according to the preferred development of the device according to the invention, according to claim 11, the punch has an arrow-shaped tip at its free end. Owing to the material displacement of the hollow profile that is effected through the inner high pressure acting in combination with the arrow-shaped tip of the punch penetrating the hollow profile for the purpose of piercing, no hole slug is produced, removal of which would entail resource expenditure. At the same time, the punched displacement bead constitutes an extension of the guide for a screw that is screwed into the attachment and the hollow profile. This screw, for example by means of its thread, can then cut an internal thread into the displacement bead as its is screwed in.
In a further preferred development of the invention, according to claim 6, during piercing a hole slug is parted out from the hollow profile wall, from the outside inwards. The production of a hole slug results in the achievement of a highly precise hole size. Also prevented thereby is the occurrence of dimensional reductions that reduce the bearing contact surface of the hollow profile on the attachment. With the therewith associated maintenance of the entire available surface of the hollow profile for the joining connection to the attachment, this connection, if already effected, is not damaged, and if not yet effected is afforded a particularly good durability with the welding operation, owing to the bearing contact surface having remained maximal.
In a further particularly preferred development of the device according to the invention, according to claim 8, the electrode arranged in the guide . bore surrounds the punch concentrically. This results in the punch being delivered accurately to the bore of the attachment, which is located in the receiving cavity that is itself coaxial in relation to the electrode. The punch is thereby prevented from colliding with the attachment. Owing to the punch being enclosed by the electrode almost without play, the punch is guided in a taught and reliable manner in the electrode.
In a further particularly preferred development of the invention, according to claim 10, one of the electrodes is constituted by the hydroforming tool itself. This reduces quite considerably the amount of equipment required for arrangement of the device, since it is not necessary for the second electrode then to be additionally introduced into the device, or into the hydroforming tool. Since the hydroforming tool consists of a conductive metal, in particular iron, or of a steel in any case, it is easy to connect this hydroforming tool to an electric pole.
Advantageously, this pole can be attached to any given location of the forming tool, such that the electrical connection can be arranged at the location that appears most suitable to the constructor of the installation. Owing to the absence of a separate electrode, the number of components of the device is reduced, which again simplifies the latter.
Otherwise, it remains to be noted here that, owing to the attachment being welded onto the hollow profile before the piercing operation, the hollow profile is reinforced by the attachment, countering an impressing movement of the hollow profile wall upon the impingement by the piercing punch. Consequently, the hollow profile wall does not sink-in in an unwanted manner.
Advantageously, capacitor discharge welding is to be used for resistance welding.
This method is distinguished by a rapid current rise with a high-current pulse, of several hundred thousand amperes, lasting only for milliseconds, a short welding time and high welding currents. The application of this method for connecting the attachment to the hollow profile has the consequence that no cooling is required for the welding operation, and welding is effected without annealing and delay, such that the finished, worked parts retain their dimensional accuracy following welding. The welding method renders possible the use, reliably in respect of the process and with the achievement of a joining quality that can be subjected to large mechanical stresses, of heat-sensitive parts, coated metals, steels having a carbon content greater than 0.2 per cent, and differing material thicknesses of the two elements to be joined. Quality monitoring, with recording of the welding data (force, energy, welding current and melt) is very simple. At the same time, there is only a small demand upon the electrical power network, owing to the use of storage capacitors.
The invention is explained more fully in the following with reference to a plurality of exemplary embodiments represented in the drawings, wherein:
Fig. I shows a cross-sectional representation of a device according to the invention during the piercing operation, with the production of a hole slug, Fig. 2 shows a cross-sectional representation of a dev.ice-according tothe _ invention during hole formation by material displacement by a punch, Fig. 3 shows a cross-sectional representation of a device according to the invention, with an attachment pressed into a hollow profile wall, with realization of a hole slug.
Represented in Figure 1 is a device for producing a screw connection point 1 on the periphery 34 of a hollow profile 7. The device includes a hydroforming tool 2, which consists of a top die 3 and a bottom die 4. Worked-in on the mutually facing sides of the dies 3 and 4 is a die relief 5, which, when the tool 2 is closed, i.e. when the top die 3 bears on the bottom die 4, delimits a forming cavity 6. The hollow profile 7 is received in this forming cavity 6, for the purpose of forming and piercing. Worked into the mutually facing sides of the top die 3 and the bottom die 4 is a guide bore 9, the axis 35 of which lies in the plane of the parting line 8 of the two dies 3 and 4. The guide bore 9 leads, on the one hand, out of the hydroforming tool 2 and, on the other hand, it opens into the die relief 5 of the forming tool 2. Inserted in the guide bore 9 is an electrically insulating sleeve 10, which extends over the entire guide bore 9 and bears closely on its wall 36.
An electrode 11 of an electric resistance welding facility of the device according to the invention is guided displaceably, with little play, in the sleeve 10. The electrode 11, with its end face 14 and the inside 15 of the sleeve 10, delimits a receiving cavity 16, in which an attachment 17 is arranged coaxially in relation to the electrode 11. The receiving cavity 16 is fashioned such that it is open towards the die relief 5, or towards the hollow profile 7. The electrode 11 has a central bushing 12, through which there extends a punch 13. The electrode 11 in this case surrounds the punch 13 concentrically, the latter being displaceably driven in the bushing 12.
For the purpose of producing the screw connection point 1, a hollow profile blank is first inserted in the forming cavity 6 of the hydroforming tool 2 and expanded through generation of a fluidic inner high pressure in the interior 23 of the hollow profile blank, until the latter is pressed onto the die relief 5 of the hydroforming tool 2 in a true-to-contour manner. The receiving cavity 16 is thereupon provided with an attachment 17, which has a central through bore 18 having an intemal thread.
In a feed movement of the electrode 11 together with the punch 13, the attachment 17, which is threaded onto the end 37 of the punch 13 that projects out of the electrode 11, is moved up to the hollow profile 7 such that it is enclosed between the latter and the end face 14 of the electrode 11, the attachment 17 being pressed, on its end face 19 that faces towards the electrode 11, onto the end face 14 of the electrode 11, and on its end face 20 that faces towards the hollow profile 7, onto the periphery 34 of the latter. In this state, the electric resistance welding facility is put into operation, an electric pole being applied to the hydroforming tool 2, i.e. either the top die 3 or the bottom die 4, such that the respective tool part constitutes the other electrode of the resistance welding facility. In the flow of electric current that is generated, the attachment 17 is thereby welded onto the periphery 34 of the hollow profile 7, with a welded connection 24 being formed. As soon as the attachment 17 has been firmly attached to the hollow profile 7 by the welded connection 24, the punch 13, which is realized as a stamping punch, travels forwards in the direction of the hollow profile 7, traveling through the bore 18 of the attachment 17 and stamping out of the hollow profile 7 a piece of wall, which constitutes a hole slug 22, forming the hole 21 into the interior 23 of the hollow profile 7. This is effected while there is inner high pressure in the interior 23 of the hollow profile 7. After formation of the hole, the fluidic inner high pressure in the hollow profile 7 is then removed, and the punch 13 is withdrawn from the forming cavity 6, or from the interior 23 of the hollow profile 7. The hole slug 22 in this case falls into the interior 23 of the hollow profile 7. The hydroforming tool 2 can now be opened, and the hollow profile 7, with the screw connection point 1 constituted by the attachment 17 and the hole region of the pierced hollow profile wall, can be removed from the forming tool 2. In order to effect the purpose of-the screw connection point 1, a screw or a pin having an external thread can be screwed into the latter.
Additionally achieved is the fact that, in the production of the screw connection point, there is no premature drop in pressure, which might possibly occur upon piercing and, owing to the pressure of the electrode, result in a sink point on the hollow-profile. Such a sink point is disadvantageous to full-surface welding of the attachment onto the hollow profile. Moreover, the attachment has already been immovably located on the hollow profile at a particularly early point in time, such that there can be no difficulties whatsoever in positioning the attachment in relation to the hollow profile. In the case of very rapidly succeeding process steps of welding and piercing, there additionally ensues the advantage that the welding heat following the welding operation is at least partially concentrated on the welding point, as a result of which the hollow profile material is still readily formable and workable in the region of the screw connection point. The result of this is that the process step of piercing is facilitated, owing to the relative softness of the hollow profile material caused by the heat.
In a further particularly preferred development of the invention, according to claim 3, the hollow profile is pierced through the bore of the attachment. Achieved thereby is a taught guidance of the piercing punch, as a result of which the latter always impacts the hollow profile at the correct point. Very high production accuracies are thereby achieved for the screw connection points.
In an alternative preferred development of the method according to the invention, according to claim 4, the attachment is pressed into the hollow profile wall by means of the electrode. The attachment, which has an end-face cutting geometry, itself produces the hole in the hollow profile wall. Welding to the hollow profile is then effected. In the case of this variant of the invention, the attachment attains its exact position relative to the hollow profile as it is pressed into the hollow.profile wall. The preliminary, but precise locating of the attachment on the hollow profile and the simultaneous creation of a hole by the attachment simplify the entire production process, since there is almost no more need for the attachment to be held in its pressing-in location and pressed onto the hollow profile. The production process is accelerated, since creation of the hole is already effected at the point in time at which the attachment is positioned on the hollow profile. Since the attachment has already been pressed into the hollow profile wall, there is no need for any additional mechanical welding pressures to be applied upon the subsequent, final locating of the attachment to the hollow profile by resistance welding, this in turn simplifying the welding equipment, since there are no corresponding pressing devices. In order to keep the hollow profile as tight as possible upon being pierced, the stub, realized on the attachment, that is pressed in has a shape having a slight conical taper towards the interior of the hollow profile. In the case of the corresponding advantageous development of the device, according to the invention, as claimed in claim 9, the electrode itself constitutes the punch, the attachment bearing on the end face of the latter.
As already stated, the attachment has a cutting geometry that faces towards the hollow profile. The electrode in this case does not constitute a piercing punch per se, but a punch that can press the attachment into the hollow profile. There is no separate piercing punch whatsoever, since the cutting geometry is advantageously provided on the attachment itself, and the latter thereby assumes the function of the piercing punch. The absence of the piercing punch additionally simplifies the control of the device for producing the screw connection point.
In a preferred development of the invention, according to claim 5, the piercing is effected from the outside inwards, through material displacement of the hollow profile material. Based correspondingly thereon, according to the preferred development of the device according to the invention, according to claim 11, the punch has an arrow-shaped tip at its free end. Owing to the material displacement of the hollow profile that is effected through the inner high pressure acting in combination with the arrow-shaped tip of the punch penetrating the hollow profile for the purpose of piercing, no hole slug is produced, removal of which would entail resource expenditure. At the same time, the punched displacement bead constitutes an extension of the guide for a screw that is screwed into the attachment and the hollow profile. This screw, for example by means of its thread, can then cut an internal thread into the displacement bead as its is screwed in.
In a further preferred development of the invention, according to claim 6, during piercing a hole slug is parted out from the hollow profile wall, from the outside inwards. The production of a hole slug results in the achievement of a highly precise hole size. Also prevented thereby is the occurrence of dimensional reductions that reduce the bearing contact surface of the hollow profile on the attachment. With the therewith associated maintenance of the entire available surface of the hollow profile for the joining connection to the attachment, this connection, if already effected, is not damaged, and if not yet effected is afforded a particularly good durability with the welding operation, owing to the bearing contact surface having remained maximal.
In a further particularly preferred development of the device according to the invention, according to claim 8, the electrode arranged in the guide . bore surrounds the punch concentrically. This results in the punch being delivered accurately to the bore of the attachment, which is located in the receiving cavity that is itself coaxial in relation to the electrode. The punch is thereby prevented from colliding with the attachment. Owing to the punch being enclosed by the electrode almost without play, the punch is guided in a taught and reliable manner in the electrode.
In a further particularly preferred development of the invention, according to claim 10, one of the electrodes is constituted by the hydroforming tool itself. This reduces quite considerably the amount of equipment required for arrangement of the device, since it is not necessary for the second electrode then to be additionally introduced into the device, or into the hydroforming tool. Since the hydroforming tool consists of a conductive metal, in particular iron, or of a steel in any case, it is easy to connect this hydroforming tool to an electric pole.
Advantageously, this pole can be attached to any given location of the forming tool, such that the electrical connection can be arranged at the location that appears most suitable to the constructor of the installation. Owing to the absence of a separate electrode, the number of components of the device is reduced, which again simplifies the latter.
Otherwise, it remains to be noted here that, owing to the attachment being welded onto the hollow profile before the piercing operation, the hollow profile is reinforced by the attachment, countering an impressing movement of the hollow profile wall upon the impingement by the piercing punch. Consequently, the hollow profile wall does not sink-in in an unwanted manner.
Advantageously, capacitor discharge welding is to be used for resistance welding.
This method is distinguished by a rapid current rise with a high-current pulse, of several hundred thousand amperes, lasting only for milliseconds, a short welding time and high welding currents. The application of this method for connecting the attachment to the hollow profile has the consequence that no cooling is required for the welding operation, and welding is effected without annealing and delay, such that the finished, worked parts retain their dimensional accuracy following welding. The welding method renders possible the use, reliably in respect of the process and with the achievement of a joining quality that can be subjected to large mechanical stresses, of heat-sensitive parts, coated metals, steels having a carbon content greater than 0.2 per cent, and differing material thicknesses of the two elements to be joined. Quality monitoring, with recording of the welding data (force, energy, welding current and melt) is very simple. At the same time, there is only a small demand upon the electrical power network, owing to the use of storage capacitors.
The invention is explained more fully in the following with reference to a plurality of exemplary embodiments represented in the drawings, wherein:
Fig. I shows a cross-sectional representation of a device according to the invention during the piercing operation, with the production of a hole slug, Fig. 2 shows a cross-sectional representation of a dev.ice-according tothe _ invention during hole formation by material displacement by a punch, Fig. 3 shows a cross-sectional representation of a device according to the invention, with an attachment pressed into a hollow profile wall, with realization of a hole slug.
Represented in Figure 1 is a device for producing a screw connection point 1 on the periphery 34 of a hollow profile 7. The device includes a hydroforming tool 2, which consists of a top die 3 and a bottom die 4. Worked-in on the mutually facing sides of the dies 3 and 4 is a die relief 5, which, when the tool 2 is closed, i.e. when the top die 3 bears on the bottom die 4, delimits a forming cavity 6. The hollow profile 7 is received in this forming cavity 6, for the purpose of forming and piercing. Worked into the mutually facing sides of the top die 3 and the bottom die 4 is a guide bore 9, the axis 35 of which lies in the plane of the parting line 8 of the two dies 3 and 4. The guide bore 9 leads, on the one hand, out of the hydroforming tool 2 and, on the other hand, it opens into the die relief 5 of the forming tool 2. Inserted in the guide bore 9 is an electrically insulating sleeve 10, which extends over the entire guide bore 9 and bears closely on its wall 36.
An electrode 11 of an electric resistance welding facility of the device according to the invention is guided displaceably, with little play, in the sleeve 10. The electrode 11, with its end face 14 and the inside 15 of the sleeve 10, delimits a receiving cavity 16, in which an attachment 17 is arranged coaxially in relation to the electrode 11. The receiving cavity 16 is fashioned such that it is open towards the die relief 5, or towards the hollow profile 7. The electrode 11 has a central bushing 12, through which there extends a punch 13. The electrode 11 in this case surrounds the punch 13 concentrically, the latter being displaceably driven in the bushing 12.
For the purpose of producing the screw connection point 1, a hollow profile blank is first inserted in the forming cavity 6 of the hydroforming tool 2 and expanded through generation of a fluidic inner high pressure in the interior 23 of the hollow profile blank, until the latter is pressed onto the die relief 5 of the hydroforming tool 2 in a true-to-contour manner. The receiving cavity 16 is thereupon provided with an attachment 17, which has a central through bore 18 having an intemal thread.
In a feed movement of the electrode 11 together with the punch 13, the attachment 17, which is threaded onto the end 37 of the punch 13 that projects out of the electrode 11, is moved up to the hollow profile 7 such that it is enclosed between the latter and the end face 14 of the electrode 11, the attachment 17 being pressed, on its end face 19 that faces towards the electrode 11, onto the end face 14 of the electrode 11, and on its end face 20 that faces towards the hollow profile 7, onto the periphery 34 of the latter. In this state, the electric resistance welding facility is put into operation, an electric pole being applied to the hydroforming tool 2, i.e. either the top die 3 or the bottom die 4, such that the respective tool part constitutes the other electrode of the resistance welding facility. In the flow of electric current that is generated, the attachment 17 is thereby welded onto the periphery 34 of the hollow profile 7, with a welded connection 24 being formed. As soon as the attachment 17 has been firmly attached to the hollow profile 7 by the welded connection 24, the punch 13, which is realized as a stamping punch, travels forwards in the direction of the hollow profile 7, traveling through the bore 18 of the attachment 17 and stamping out of the hollow profile 7 a piece of wall, which constitutes a hole slug 22, forming the hole 21 into the interior 23 of the hollow profile 7. This is effected while there is inner high pressure in the interior 23 of the hollow profile 7. After formation of the hole, the fluidic inner high pressure in the hollow profile 7 is then removed, and the punch 13 is withdrawn from the forming cavity 6, or from the interior 23 of the hollow profile 7. The hole slug 22 in this case falls into the interior 23 of the hollow profile 7. The hydroforming tool 2 can now be opened, and the hollow profile 7, with the screw connection point 1 constituted by the attachment 17 and the hole region of the pierced hollow profile wall, can be removed from the forming tool 2. In order to effect the purpose of-the screw connection point 1, a screw or a pin having an external thread can be screwed into the latter.
In divergence from the preceding exemplary embodiment, in a new variant of the invention the punch 25, which is comparable to the punch 13, is realized with an arrow-shaped tip 27 at the free end 26 (Figure 2). For the purpose of producing a hole 38, after the attachment 17 has been welded onto the hollow profile 7 the punch 25 is moved onto the hollow profile 7, the punch penetrating the wall of the hollow profile 7 by means of its tip 27. Under the counteracting force of the inner high pressure prevailing in the interior 23 of the hollow profile 7, the hollow profile material impinged upon by the punch 25 is displaced away sideways, forming a hollow profile bead 28. At the same time, a sink cavity 29 is produced, which forms on the outer periphery 34 of the hollow profile 7, beneath the attachment 17. The method described in this exemplary embodiment thereby produces a hole 38 without a hole slug 22. To remove the hollow profile 7, as in the case of the stamping punch 13 of the preceding exemplary embodiment the punch 25 is drawn back out of the hollow profile 7, being so drawn that it is also at a distance from the bore 18 of the attachment 17. Clearly, the fluidic inner high pressure is removed before the hydroforming tool 2 is opened, and the pressure fluid is taken away.
A further variant of the invention is shown by Figure 3. There, the electrode 30 is of a solid design, and has no bore. The attachment 31 is realized according to the model of a stamping nut. In contrast to the two preceding exemplary embodiments, here it is the piercing of the hollow profile 7, not the welding-on of the attachment 31, that is performed first. The electrode 30, which in this case assumes the role of a punch, presses the attachment 31 against the wall of the hollow profile 7 in such a way that a stub 32 of the attachment 31, which stub has a cutting geometry 33, is pressed into the hollow profile wall, a hole slug 22 and the hole 39 being produced at the same time. The attachment 31, fixed thus in the hollow profile wall, is now resistance-welded to the latter. In order to ensure the outward tightness of the hollow profile 7 under the counteracting inner high pressure, the stub 32 is realized with a slight conical taper towards the interior 23 of the hollow profile, such that wedge faces, which effect a particularly good tightness capability with the conical shape of the stub 32, are produced at the edges of the produced hole 39.
In all three stated exemplary embodiments, it is conceivable for the electrically insulating sleeve 10 to be likewise displaceable in the guide bore 9. This is particularly helpful when the hollow profile 7, with the produced screw connection point 1, is to be removed without impediment from the hydroforming tool 2. In this case, the hollow profile 7 can be released from the forming cavity 6 in a lifting movement when the hydroforming tool 2 is open, the sleeve 10 remaining in a.
position drawn back from the screw connection point 1, or from the attachment 17, 31.
A further variant of the invention is shown by Figure 3. There, the electrode 30 is of a solid design, and has no bore. The attachment 31 is realized according to the model of a stamping nut. In contrast to the two preceding exemplary embodiments, here it is the piercing of the hollow profile 7, not the welding-on of the attachment 31, that is performed first. The electrode 30, which in this case assumes the role of a punch, presses the attachment 31 against the wall of the hollow profile 7 in such a way that a stub 32 of the attachment 31, which stub has a cutting geometry 33, is pressed into the hollow profile wall, a hole slug 22 and the hole 39 being produced at the same time. The attachment 31, fixed thus in the hollow profile wall, is now resistance-welded to the latter. In order to ensure the outward tightness of the hollow profile 7 under the counteracting inner high pressure, the stub 32 is realized with a slight conical taper towards the interior 23 of the hollow profile, such that wedge faces, which effect a particularly good tightness capability with the conical shape of the stub 32, are produced at the edges of the produced hole 39.
In all three stated exemplary embodiments, it is conceivable for the electrically insulating sleeve 10 to be likewise displaceable in the guide bore 9. This is particularly helpful when the hollow profile 7, with the produced screw connection point 1, is to be removed without impediment from the hydroforming tool 2. In this case, the hollow profile 7 can be released from the forming cavity 6 in a lifting movement when the hydroforming tool 2 is open, the sleeve 10 remaining in a.
position drawn back from the screw connection point 1, or from the attachment 17, 31.
Claims (11)
1. A method for producing a screw connection point on the periphery of a hollow profile that is expanded by means of fluidic inner higher pressure, an attachment having a bore that caries an internal thread being attached to the hollow profile in the hydroforming tool, and the hollow profile being pierced flush with the bore, characterized in that the attachment (17, 31) is guided up to the hollow profile (7) by means of an electrode (11, 30) integrated into the hydroforming tool (2), and the attachment (17, 31), via the electrode (11, 30), is resistance-welded to the hollow profile (7), in the region of the screw connection point (1) to be formed, after said hollow profile has come to bear on the die relief (5).
2. The method as claimed in claim 1, characterized in that the welding is effected before the piercing.
3. The method as claimed in either of claims 1 or 2, characterized in that the hollow profile (7) is pierced through the bore (18) of the attachment (17, 31).
4. The method as claimed in claim 1, characterized in that the attachment (31) is pressed into the hollow profile wall by means of the electrode (30), the attachment (31) produces the hole (39) in the hollow profile wall by means of an end-face cutting geometry (33), and the welding is then effected.
5. The method as claimed in any one of claims 1 to 4, characterized in that the piercing is effected from the outside inwards, through material displacement of the hollow profile material.
6. The method as claimed in any one of claims 1 to 4, characterized in that during piercing a hole slug (22) is parted out from the hollow profile wall, from the outside inwards.
7. A device for producing a screw connection point on the periphery of a hollow profile, comprising a hydroforming tool in whose forming cavity, constituted by the die relief, the hollow profile is arranged for the purpose of expansion by means of fluidic inner high pressure, comprising a punch for piercing the hollow profile wall at the location of the screw connection point to be realized, which punch is displaceably guided in a guide bore opening into the die relief, an attachment having a bore that carries an internal thread being received in the guide bore, characterized in that the device additionally includes a resistance welding facility whose electrodes (11, 30) are integrated in the hydroforming tool (2), at least one of the electrodes (11, 30) is arranged in the guide bore (9) and, with its end face (14), delimits in the latter a receiving cavity (16) that is open towards the hollow profile (7) and in which the attachment (17, 31) is arranged.
8. The device as claimed in claim 7, characterized in that the electrode (11) arranged in the guide bore (9) surrounds the punch (13, 25) concentrically.
9. The device as claimed in claim 7, characterized in that the electrode (30) constitutes the punch, on the end face of which there bears the attachment (31), which has a cutting geometry (33) facing towards the hollow profile (7).
10. The device as claimed in any one of claims 7 to 9, characterized in that one of the electrodes is constituted by the hydroforming tool (2) itself.
11. The device as claimed in any one of claims 7, 8 or 10, characterized in that the punch (25) has an arrow-shaped tip (27) at its free end (26).
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE102006028773A DE102006028773A1 (en) | 2006-06-23 | 2006-06-23 | Method and device for producing a screw joint |
| DE102006028773.8 | 2006-06-23 | ||
| PCT/EP2007/001264 WO2007147453A1 (en) | 2006-06-23 | 2007-02-14 | Method and device for producing a screw connection point |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2666551A1 true CA2666551A1 (en) | 2007-12-27 |
Family
ID=38042799
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002666551A Abandoned CA2666551A1 (en) | 2006-06-23 | 2007-02-14 | Method and device for producing a screw connection point |
Country Status (7)
| Country | Link |
|---|---|
| EP (1) | EP2032278B1 (en) |
| JP (1) | JP2009541054A (en) |
| CN (1) | CN101479056A (en) |
| AT (1) | ATE453466T1 (en) |
| CA (1) | CA2666551A1 (en) |
| DE (2) | DE102006028773A1 (en) |
| WO (1) | WO2007147453A1 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102008040034B4 (en) * | 2008-06-30 | 2017-05-11 | Volkswagen Ag | Method and device for producing a sheet-metal component |
| KR101443454B1 (en) | 2012-10-31 | 2014-09-24 | 현대제철 주식회사 | Electrode unit and electric resistance spot welding machine having the same |
| DE102016005033B3 (en) * | 2016-04-23 | 2017-10-12 | Icm - Institut Chemnitzer Maschinen- Und Anlagenbau E.V. | Device for producing a tubular distributor arrangement with branches in the wall region between the ends of the tube and tubular distributor arrangement |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4020316A (en) * | 1975-08-22 | 1977-04-26 | Fastener Industries Inc. | Method and apparatus for positioning nuts to be welded to a base |
| DE19508632C2 (en) * | 1995-03-10 | 2002-09-19 | Audi Ag | Method for connecting a first component to a second component |
| DE19733477C2 (en) * | 1997-08-02 | 1999-12-02 | Daimler Chrysler Ag | Method for producing a hollow profile connected to a joining part from an initial shape by means of internal high pressure into a final shape, and device for carrying out the method |
| US6442820B1 (en) * | 2000-10-26 | 2002-09-03 | F & P Mfg., Inc. | Method and apparatus for forming a tube having an article inserted therein |
| JP2003334625A (en) * | 2002-05-22 | 2003-11-25 | Suzuki Motor Corp | Method for manufacturing pipe member with locking element and pipe member with locking element |
| JP2005052950A (en) * | 2003-08-07 | 2005-03-03 | Aisin Takaoka Ltd | Die forming-welding method of closed cross-sectional hollow metallic part and molding welding device |
-
2006
- 2006-06-23 DE DE102006028773A patent/DE102006028773A1/en not_active Withdrawn
-
2007
- 2007-02-14 DE DE502007002492T patent/DE502007002492D1/en active Active
- 2007-02-14 AT AT07703452T patent/ATE453466T1/en active
- 2007-02-14 WO PCT/EP2007/001264 patent/WO2007147453A1/en active Application Filing
- 2007-02-14 CN CNA2007800236506A patent/CN101479056A/en active Pending
- 2007-02-14 JP JP2009515717A patent/JP2009541054A/en not_active Abandoned
- 2007-02-14 CA CA002666551A patent/CA2666551A1/en not_active Abandoned
- 2007-02-14 EP EP07703452A patent/EP2032278B1/en not_active Not-in-force
Also Published As
| Publication number | Publication date |
|---|---|
| CN101479056A (en) | 2009-07-08 |
| ATE453466T1 (en) | 2010-01-15 |
| EP2032278A1 (en) | 2009-03-11 |
| DE102006028773A1 (en) | 2007-12-27 |
| EP2032278B1 (en) | 2009-12-30 |
| WO2007147453A1 (en) | 2007-12-27 |
| JP2009541054A (en) | 2009-11-26 |
| DE502007002492D1 (en) | 2010-02-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |