EP2611563A1

EP2611563A1 - Welding head with a flexible element that can variably set a prestress

Info

Publication number: EP2611563A1
Application number: EP11767237.8A
Authority: EP
Inventors: Johann Kaussler
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2010-10-06
Filing date: 2011-10-04
Publication date: 2013-07-10
Also published as: WO2012045746A1

Abstract

A movable resistance-welding head (1) produces its welding force by means of a helical spring (4), which is arranged on a line between a pneumatic cylinder (2) and the electrode (4) of the welding head (1). The helical spring (4) makes it possible for the electrode (3) to be decoupled from the pneumatic cylinder (2) as long as the electrode (3) is lying against a workpiece. Furthermore, it regulates a slipping movement of the electrode (3). The linear construction avoids moments of force and thus reduces electrode wear. By means of the helical spring (4), a welding force of between 240 and 1400 N can be variably set. Furthermore, the welding force remains virtually constant during the slipping movement. The compact construction of the welding head (1) allows high electrode accelerations, any desired installation positions and use in ergonomic, partly mechanized arrangements.

Description

description

WELDING HEAD WITH A VERTICAL VARIABLE ADJUSTABLE ELASTIC ELEMENT

The invention relates to a welding head for carrying out the resistance welding, resistance soldering or hot riveting, wherein the workpieces to be joined by resistance heating at the same time exerted compressive force (welding force) on a joint (welding the so-called. Welding) are bonded together by material or solder.

In resistance welding two electrically conductive workpieces are heated by an electric current flow until melting ^{¬ on} . The melt solidifies after the flow of current and forms a welded joint. In this case, the formation of an intimate connection is possibly supported by compression during and after the current flow (resistance pressure welding). Resistance welding generally takes place without supply of additional material. The resistance point ^¬ welding as a special form of resistance welding is used in ^¬ example, for the connection of steel sheets in body and vehicle. But it also serves for welding ^¬ Shen of aluminum or other metals, eg. As in the manufacture of capacitors, terminals of coils and motor windings or contact sets for relay and line circuit breaker. Resistance spot welding offers the advantage of concentrating a high energy in the form of electric current in a short time on a small area of a workpiece, whereby a non-detachable connection is created under application of high pressure, which is applied pneumatically or electromechanically.

In resistance soldering, an electrical current closure at a soldering point generates heat. It is suitable for soldering parts of unequal mass, for example of small parts on sheets, which have a high thermal conductivity. The solder ^¬ put this forms an electrical resistance and he ^¬ heated directly. Welding heads are be ^¬ known for the described application. These carry an electrode, which are movably mounted in the direction of a counter electrode. The to be joined

Workpieces are first positioned between the two electrodes and then pressed by a movement of the electrode of the welding head on the counter electrode. During the bonding process occurs by a required process temperature Pro ^¬ and welding force to a material softening that results by the pressure of the electrodes on the workpieces to be a so-called repositioning of the welding head.

From the prior art, a welding head with an on ^¬ drive and with an electrode which is movably mounted, known, see. "Micro welding head with adjustable electric ^¬ force", available on the Internet at

www. isomatic. com / html / Deutsh / ksk. htm on 28.09.2010. Here, the welding force can be adjusted between 0.7 and 200 Newton.

A welding head with a drive and an electrode, which is movably mounted, is also available from the document "Constant Force Head by MacGregor" on the Internet at http: //www.macgregorsystems. com / files / downloads / Constant% 2 OFo rce% 20Weld% 2 OHead. pdf on 05.10.2010, known.

In the cited prior art, the repositioning of the

Welding head or mounted thereon electrode via a pneumatic device. Negative effects here are their sluggish behavior and thereby a reduction in the welding force during the resetting of the electrode during the

Welding, which leads to a reduced quality of the connection process. When linear drives in the electrode control, it is disadvantageous that the welding force during the entire welding process can not be held con ^¬ stant. However, high-quality and convenient access processes require optimum ^¬ put control of Nachsetzverhaltens. The invention is therefore based on the object, a

Specify welding head, which improves a Nachsetzverhalten the welding head compared to the prior art.

This object is solves ge ^¬ by a welding head with a drive and with an electrode that is movably supported. The drive, an elastic element and the electrode are arranged in a line so that a line of action of a force acting from the drive or the elasti ^¬ rule element to the electrode, centrally extends through the electrode. The welding head is characterized ^¬ net, that a bias of the elastic member is variably adjustable, whereby a welding force, which is transmitted via the elastic member to the electrode, is variably adjustable ^¬ bel.

By adjusting the bias of the elastic member 4, the welding force can be set efficiently between 240 and 1400 N. Depending on the design, other limits and guidelines for the welding force may result.

However, the welding head achieves even more advantages. The linear arrangement of the drive, the elastic element and the electrode optimizes the tracking behavior of the actuator

Electrode, since no force moments between the drive and the joint or between the elastic member and the joint may occur. A moment of force would cause increased friction in guides of the electrode and a higher inertia and thus a poor Nachsetzverhalten the

Welding head to pull. In contrast, the welding head according to the invention allows optimally designed control of the Nachsetzverhaltens, which is realized in the immediate vicinity of Fügestel ^¬ le. An important advantage of this construction compared to the prior art is thus the direct one

Power flow from the drive via the elastic element to the electrode. Here, the elastic element of the post ^¬ releasing control is used. Because the line of effect of the welding force is centric and extends longitudinally through the electrode, there are no relative ^¬ movements to the workpieces. This leads to a high reproducibility and little electrode wear. The construction also allows a compact construction of the welding head. As a result, ergonomic and teilmecha ^¬ nized solutions are possible. Furthermore, an installation position of the welding head is arbitrary. The welding head can also be isolated one ^{after the} other. The compact design also allows the use of the welding head as a basic concept in the context of a platform concept that uses this resource. Also, the welding head can be used by its movable electrode for un ^¬ different material flow systems such as Schieberaufnah ^¬ me, turntable or workpiece carrier.

According to one embodiment, the bias is adjustable with an adjusting nut which is mounted on a guide shaft of the elastic element. In a development, the welding head is set up to move the electrode in synchronism with the drive, as long as the electrode is not in contact with any workpiece, because a pressure force is exerted by the drive on the electrode. Furthermore, the welding head is adapted to decouple the electrode from the drive and to move the electrode relative to the drive by means of the elastic drive, as long as the electrode rests against a workpiece.

A compressive force on the workpieces to be joined is hereby transmitted directly from the drive to the movable electrode of the

Welding head introduced. Also, a spring action of the elastic ^¬ rule element is a direct way into the electrode. The power flow of the drive and elastic element is separated in Nachsetzverhalten however. Thus, a spring force of the elastic element is decoupled mecha ^¬ nically by a force of the drive. This results in a high reproducible quality of resistance welding and makes it possible to perform even the most challenging non-ferrous metal welds. The Decoupling the drive from the electrode by means of the elastic element reduces friction losses and increases the reproducibility. According to one embodiment, the elastic element of the

Welding head a compression spring, in particular a Schraubenfe ^¬ the, which is arranged for transmitting the welding force to the Elektro ^¬ de and designed for controlling a Nachsetzbewegung the electrode relative to a workpiece.

Compression springs are components which give way under load and return to their original shape after relieving, thus behaving elastically restoring. The restoring force of a compression spring is according to the Hooke's law proportional to a displacement of the force application point ent ^¬ against a force direction in which the pressure spring acts.

The aforementioned embodiment has the advantage that the compression spring regulates the Nachsetzweg while maintaining the welding force during the process almost constant.

The compression spring thus enables optimum Nachsetzverhal ^¬ th the electrode during welding. The welding head can therefore be used for the most demanding non-ferrous metal welds.

In a further development, the drive of the welding head is realized by at least one pneumatic cylinder. In a refinement which is based thereon, the welding head is set up to advance the electrode by an electric extension during extension of the pneumatic cylinder until the electrode touches a workpiece. Furthermore, the welding head is adapted to a compression of the elastic element by a spring travel during the extension of the pneumatic Zy ^¬ Linders after the electrode has placed on the workpiece, wherein the spring travel is the difference of Zylin ^¬ derhubs and the electrode stroke and together with the bias of the elastic element, the welding force defi ned ^¬ exerted on the workpiece. Finally the welding head is adapted to advance the electrode about a Nachsetzweg during a welding operation using the elastic element, wherein the compression of the elastic ^¬ rule element is reduced by the Nachsetzweg.

This further describes the above-described Entkop ^¬ pelung of electrode and drive in detail. The previously genann ^¬ th advantages apply accordingly.

According to a further development, the

Welding head on a sensor which is adapted to detect a lack of compression of the elastic member during the extension of the pneumatic cylinder. As a result, a lack of a workpiece is detectable. The signal of the sensor can also be used as a start signal for egg ^¬ NEN welding process in this case, as can be CONTROL ^¬ profiled here is whether workpieces are present for welding.

In another development, the welding head is equipped with a measuring probe, which is arranged to measure the Nachsetzwegs the electrode. The probe measures the Nachsetzweg the electrode during welding. Before ^¬ geous affects of this is that the probe can work throughout the welding process continu ^¬ ously. This leads to a secure process control. The Nachsetz ^¬ way can be obtained directly from the travel.

According to one disclosed is form the electrode of the welding head between two ^¬ electrode guides arranged on both sides, in particular ball guides, movably guided.

In this case, the electrode guides are arranged in an electrode plane in pairs of the electrode, wherein the welding ^¬ force is guided centrally through the electrode. This offers the advantage that a friction in the electrode guides is reduced. This also reduces the inertia of the

Welding head and leads to a better overall Behavior of the electrode during welding. Here, too, has an advantageous effect that the force flow described above or the line of action of the force in a line with the

Electrode, but also the electrode guide are. Furthermore, this construction offers the advantage that an electrode holder, which accommodates the movable electrode, has only a small mass. This leads to a low mass inertia and high ^¬ electrodes accelerations. The ball guides offer the particular advantage of additionally reducing the coefficients of friction in the electrode guides. Overall, the dynamic behavior of the welding head is thereby supported under ^¬.

According to one embodiment of the invention, the welding head has a cooling water feedthrough, which is set up to cool the electrode. As a result, constant heat ^{¬ conditions} can be achieved.

The welding head is suitable for welding, in particular resistance welding, resistance pressure welding and resistance spot welding, for soldering, in particular also for resistance soldering, or also for hot riveting. This offers the advantage that the welding head can be used by process substitution as a resource for different connection technologies.

In the following, embodiments of the invention will be explained in more detail with reference to figures. FIG. 1 shows four operating states of the welding head,

2 is a view of the welding head with a cerium ^¬ interpretation into its components, Figure 3A is a front view with a section through the welding head,

FIG. 3B shows a side view of the welding head, FIG. 3C is a plan view of the welding head.

FIG. 1 shows a welding head 1 in a first operating state 11, a second operating state 12, a third operating state 13 and a fourth operating state 14. The welding head 1 is composed of a drive 2, an electrode 3, an elastic element 4, respectively Sensor 8, a probe 9 and electrode guides 30 together. The drive 2, the elastic element 4 and the electrode 3 are arranged in a line of action 5. Under the welding head 1 are each two workpieces 6, which are ver ^¬ welded together ver, located. The drive 2 beinhal ^¬ tet two status scans 40. The exact arrangement of the transmitter sors 8 can be taken from the other figures that will be described later. The elastic element 4 is shown in Figure 1 as a compression spring, more precisely as a coil spring. The drive 2 includes, for example, one or more pneumatic ^¬ tables cylinder, which are not shown in detail in Figure 1. The drive 2 develops its driving force along the line of action 5 and transmits it along the vertical to the other visible in Figure 1 elements of the welding head 1, in particular the elastic element 4 and the electrode 3. A galvanic coating of the electrode 3 prevents corrosion of the Electrode 3 and avoids contact resistance changes.

An adjusting nut 74, which is mounted on a guide shaft 75 of the elastic member 4, serves to adjust a bias voltage of the elastic member 4.

In the first operating state 11, the welding head 1 is in a basic position. In the following it is assumed that the drive 2 is realized with a pneumatic cylinder, which has retracted in the first operating state 11. The pneumatic cylinder is located in this case along the line of action 5 in the actuator 2. In the extension of the cylinder pneumati ^¬ rule in Figure 1, a spacer sleeve 21 is einge- lines, which defines a cylinder stroke Z of the pneumatic cylin ^¬ DERS in the first operating state 11 in which the pneumatic cylinder is retracted. By means of the spacer sleeve 21 of the cylinder stroke Z of the pneumatic cylinder is variably adjustable. To change the piston stroke in the Z, the spacer sleeve must be replaced by a spacer sleeve 21 with suitable Abmessun ^¬ gen. The elastic member 4 is biased in the first operating state Be ^¬. 11 In the second operating state 12 of the pneumatic cylinder is fully extended and in this case has the cylinder stroke Z to ^¬ back. The electrode 3 has completed the transition from the first Be ^¬ operating state 11 in the second operation state 12 and sets a Elektrodehub E listed on the workpieces. 6 Since the electrode 3 on the workpieces 6 already on ^¬ sets before the pneumatic cylinder is extended to the entire cylinder stroke Z, the elastic element 4 to ^¬ addition to the already in the first operating state 11 vorhan ^¬ that bias is still compressed by a spring travel F. which is also shown in FIG. The elastic element 4 is thus suppressed in the second operating state 12. The electrode 3 now presses with a welding force on the

Workpieces 6. The welding force results from the prestressing of the elastic element 4 and the spring travel F. It can be set variably between 240 and 1400 N. The adjustment is made, if necessary, in the second operation state 12. For this purpose, a bias voltage V (shown in Figure 3A) of the elastic element 4, for example 1.8 to 8.5 mm is ^¬ represents. The spring travel F is set for example between 1 and 3 mm, preferably at 1.5 mm. Depending on the construction, other limits and guidelines for the

Welding force, the spring travel F and the bias voltage V result.

The cylinder stroke Z is composed of the Elektrodehub E and the spring travel F. The probe 9 is designed as an inductive executed and measures during the welding process, the repositioning of the electrode. 3

The welding process takes place between the second operating state 12 and the third operating state 13, and is already completed in the latter. During the welding process, the electrode 3 sinks by the Nachsetzweg N in the workpieces 6 a. Accordingly, the compression of the elas ^¬ tical element 4 decreases starting from the spring travel to the Nachsetzweg N.

The fourth operating state 14 shows the case that the pneu matic cylinder around the cylinder stroke ^¬ Z is completely ausgefah ^¬ reindeer, but no workpieces are present 6, therefore, the electrode 3 is pushed into the void. In this

Thus, no compression of the elastic element 4 takes place about the spring travel F, i. the elastic element 4 is not acted upon in the fourth operating state 14. This can be detected by the sensor 8 and serves to check whether workpieces are available for welding.

In summary, the electrode 4 moves as long as synchronously to the drive 2 or to the movement of the pneumatic cylinder, as it rests against any workpiece 6. As soon as the electrode is applied to a workpiece 6 3, it is entkop ^¬ pelt from the actuator 2 and moves relative to the movement of the pneumati ^¬ rule cylinder. This is achieved by the elastic element 4 it enables ^¬. FIG. 2 again shows a welding head 1 with a drive 2, an electrode 3 and an elastic element 4, which are again arranged on a line of action 5. In addition, a sensor 8, a spacer sleeve 21, a pneumati ^¬ shear cylinder 20 and electrode guides 31 are located. The elements mentioned have the same function as described above. In particular, an adjusting nut 74 which is mon ^¬ features on a guide shaft 75 of the elastic member 4 serves to bias of the elastic member 4 adjust. Figure 2 shows the assembly of said elements in detail.

3A shows a front view of a welding head 1 with a section through the welding head 1. Shown again are a drive 2, an electrode 3 and an elastic element 4, which are arranged linearly on a line of action 5. Continue to recognize well a spacer sleeve 21 and

Electrode guides 30. In addition to a cylinder stroke Z, a spring travel F and a Elektrodehub E, a bias voltage V is shown in Figure 3A, around which the elastic ^¬ cal element 4 is biased. The bias voltage V is adjusted with an adjusting nut 74 which is mounted on a guide shaft 75 of the elastic member 4. The named elements have the same function as described ^above .

FIG. 3B shows a welding head 1 in a side view. In addition to a drive 2, an elastic element 4 and an electrode 3, which are again arranged linearly in a line of action 5, Figure 3B also shows a spacer sleeve 21, a sensor 8 and a connection for a Spannungsmesslei ^¬ tion 50. The connection for a voltage measuring line 50 serves to measure a voltage drop between the electrodes. The other elements have the same function as described above. In particular, here also an adjusting nut 74, which is mounted on the guide shaft 75, serves to einzustel ^¬ len a bias of the elastic member 4.

Figure 3C shows a plan view of a welding head 1. This is partly a sectional view shown by the welding head 1, in particular, an electrode 3 and a drive are know to 2 ^¬ it.

The aforementioned embodiments, developments and embodiments can be freely combined with each other.

Claims

claims

1. welding head (1),

- With a drive (2) and with an electrode (3) which is movably mounted,

wherein the drive (2), an elastic element (4) and the electrode (3) are arranged in a line, so that a line of action (5) of a force which originates from the drive (2) or the elastic element (4) on the

Electrode (3) acts centrally through the electrode (3),

characterized in that

a bias voltage (V) of the elastic member (4) is variably adjustable, whereby a welding force which is transmitted via the elastic element (4) to the electrode (3) übertra ^¬ gene is variably adjustable.

2. Welding head (1) according to claim 1,

- In which the bias voltage (V) with an adjusting nut (74) which is mounted on a guide shaft (75) of the elastic ele ^¬ management (4) is adjustable.

3. Welding head (1) according to one of the preceding claims, - arranged to move the electrode (3) synchronously to

Drive (2), as long as the electrode (3) on any workpiece is not applied by a compressive force from the drive (2) on the electrode (3) is applied, and

set to a decoupling of the electrode (3) by the drive (2) and to move the electrode (3) rela ^¬ tively to the drive (2) by means of the elastic member (4) as long as the electrode (3) (on a workpiece 6 ) is present.

4. Welding head (1) according to one of the preceding claims, - in which the elastic element (4) is a compression spring, in particular ^{¬ a} special helical spring, which arranged for transmitting the welding force to the electrode (3) and for a control of a Nachsetzbewegung the electrode (3) ge compared to a workpiece (6) is designed.

Welding head (1) according to any one of the preceding claims, wherein the drive (2) by at least one rule pneumati ^¬ cylinder (20) is realized.

Welding head (1) according to claim 5,

arranged to feed the electrode (3) by a Electrode (E) during an extension of the rule pneumati ^¬ cylinder (20) until the electrode (3) seated on a work piece ^¬ (6),

arranged for compression of the elastic element (4) by a compression spring travel (F) during the extension of the pneumatic cylinder (20) after the electrode (3) has been placed on the workpiece (6), wherein the compression spring travel (F) is the difference of cylinder stroke (Z) and the electrode stroke (e) and which together with the bias voltage (V) of the elastic member (4) defines the welding force, wel ^¬ che is exerted on the workpiece (6), and

arranged to advance the electrode (3) by a post-setting (N) during a welding operation by means of the elastic member (4), wherein the compression of the elastic member (4) is reduced by the Nachsetzweg (N).

Welding head (1) according to claim 6,

with a sensor (8) for detecting a lack of compression of the elastic element (4) during the extension of the pneumatic cylinder (20), whereby a lack of a workpiece (6) is detectable.

Welding head (1) according to claim 6 or 7,

with a probe (9), arranged to measure the setting path (N) of the electrode (3).

9. Welding head (1) according to one of the preceding claims, wherein the electrode (3) between two electrodes arranged on both sides ^¬ guides (30), in particular ball bearings, is movably guided.

, Welding head (1) according to one of the preceding claims with a cooling water passage, adapted for Kühlun the electrode (3).

11. Use of a welding head (1), which is designed according to one of the preceding claims, for welding ^¬ Shen, in particular resistance welding, resistance pressure welding or resistance spot welding, soldering, in particular resistance brazing, or hot riveting.