EP2872284A1

EP2872284A1 - Weld head for holding a spring assembly

Info

Publication number: EP2872284A1
Application number: EP13730559.5A
Authority: EP
Inventors: Johann Kaussler
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2012-07-12
Filing date: 2013-06-19
Publication date: 2015-05-20
Also published as: MX2015000494A; CN104602856A; DE102012212212A1; WO2014009123A1

Abstract

The disclosed weld head has a mounting position for holding a self-contained and replaceable spring assembly which, in the mounted position, is arranged in the power flow between the drive unit and the electrode. The mounted position of the spring assembly offers great flexibility in terms of the range of required spring forces. The weld head can thus be easily and quickly retooled to substitute one method for another one. All it takes to do that is to place a suitable spring assembly in the mounted position. It is not absolutely necessary to carry out other mounting steps such as screwing parts together. The spring assembly that is mounted in the weld head has the advantage of controlling the slipping path of the weld head while keeping the welding force nearly constant during the entire process. The spring assembly thus allows for an optimal and very quick slipping behavior of the electrode during the welding process. The weld head can therefore be used for highly complex welding operations with nonferrous metals. Furthermore, the compact design allows the weld head to be used as the basic feature of a platform concept using said resource. In addition, the movable electrode allows the weld head to be used for various material flow systems such as slider mounts, rotary tables, or workpiece holders.

Description

Description / Description

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) bonded together or via solder become.

In resistance welding, two electrically conductive workpieces are heated by an electrical current flow until they melt. 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 flow of current (resistance - pressure welding). Resistance welding generally takes place without supply of additional material. Resistance spot welding as a special form of resistance welding is used, for example, to join steel sheets in bodywork and vehicle construction. But it also serves to weld 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 joint forms an electrical resistance and heats up directly. Welding heads are known for the described fields of application. These carry an electrode, which are movably mounted in the direction of a counter electrode. The workpieces to be joined are first posi - tioned between the two electrodes and then pressed onto the counterelectrode by a movement of the electrode of the welding head. During the bonding process, a required process temperature and welding force lead to a softening of the material, which leads to a so-called repositioning of the welding head due to the pressure of the electrodes on the workpieces.

From the prior art, a welding head with a drive and with an electrode which is movably mounted, known. "Micro welding head with adjustable electrode 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 htt: // www. macgregorsystems. com / files / downloads / Constant% 2 QFo rce% 20Weld% 20Head.pdf on 05.10.2010, known.

In this prior art, adjustment and control of a welding force, that is, the pressing force exerted by the electrode on the workpieces, is performed indirectly by a pressure reducer on a pneumatic cylinder of the drive. Alternatively, a force sensor is positioned between the electrode and a workpiece carrier receptacle to measure the welding force. However, this direct type of measurement is different and expensive for each application. From WO 2012045763 AI a resistance welding head for resistance welding and soldering is known. Due to its physical structure, this resistance welding head is able to absorb very large forces above 2000 N. Of the Power flow from a pneumatic cylinder to the electrode is in line. Therefore, no moments of force occur. The movable part of the welding head has a low mass, which favors a quick readjustment. The welding force is measured directly in the force flow and can be queried continuously. It remains almost constant during the welding process and is very precisely adjustable. The welding head is designed according to a platform concept and can be mounted in any position. The repositioning is realized by a compression spring. The welding head is suitable for carrying out resistance welding. Due to its physical structure, it is able to convert even very large forces with a fast setting behavior and to keep the change in the welding force during the process negligibly small. The

Nachsetzverhalten is realized via a compression spring. This welding head is shown in Figures 1, 2a, 2b, 3 and 4 of the present application. The invention has for its object to provide a welding head, which allows a quick conversion for different applications.

This object is achieved by a welding head with a drive and a movably mounted electrode. The welding head has an installation position for receiving a self-contained and replaceable spring assembly, wherein the spring assembly is arranged in the installed position in the power flow between the drive and the electrode.

The advantages mentioned below need not necessarily be achieved by the subject-matter of the independent patent claims. Rather, these may also be advantages that are achieved only by individual embodiments, variants or developments.

The installation position for the spring package provides great flexibility in terms of a bandwidth of required spring forces ready. As a result, the welding head can be retrofitted easily and quickly for various processes in terms of process substitution. A suitable spring package must be used only in the installation position. Further assembly steps such as screwing are not mandatory.

The spring pack installed in the welding head offers the advantage that it controls the trajectory of the welding head and at the same time keeps the welding force almost constant during the process. The spring package thus allows an optimal and very fast Nachsetzverhalten the electrode during welding. The welding head can therefore be used for the most demanding non-ferrous metal welds.

If one wanted to retrofit the welding head known from WO 2012045763 AI for a new application, one would have to replace its compression spring with another one. This requires in the prior art, a complex disassembly of the

Welding head. In contrast, the new welding head with the spring assembly allows a very rapid replacement of the compression spring.

The construction also allows a compact construction of the welding head. As a result, ergonomic and semi-mechanized solutions are possible. Furthermore, an installation position of the welding head is arbitrary. Also, the welding head can be easily isolated. 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 different material flow systems such as slide holder, turntable or workpiece carrier. According to one embodiment, the welding head includes a frame which is adapted to receive the spring assembly. In a further development, the frame has a recess through which the spring assembly, in particular for setting a bias of the spring assembly, remains accessible externally even when installed.

This development has the advantage that the spring assembly can be quickly and easily inserted and removed through the recess. Furthermore, the recess offers the advantage that the setting of a bias of a compression spring of the spring assembly can be carried out in the installed state through the recess.

According to one embodiment, the frame in the axial direction of the spring assembly has a round opening with an internal thread.

This embodiment has the advantage that a piston rod can be guided through the round opening of the frame, which cooperates in an advantageous manner with the spring assembly and the frame for transmitting power, and on the other hand by means of a form fit for easy clamping of the spring assembly and thus for quick conversion of the welding head can be designed. In a further development, the welding head includes a piston rod, which is movably guided by a spring-locking screw, which forms a back stop for a head of the piston rod. The spring locking screw can be screwed with an external thread in the frame so that the head of the piston rod is pressed by the spring locking screw on the spring assembly and applies an additional bias on the compression spring of the spring assembly.

This development has the advantage that the head of the piston rod and the spring locking screw in an advantageous

Way interact with the spring assembly and the frame for power transmission and the other by means of a positive connection are designed for easy clamping of the spring assembly and thus for rapid retooling of the welding head.

According to one embodiment, the head of the piston rod is shaped to produce a positive connection with the spring assembly. Alternatively or additionally, the head of the piston rod has a central recess, which is dimensioned for receiving one end of a rigid axially arranged in the spring assembly guide pin upon compression of the spring assembly.

This embodiment has the advantage that the head of the piston rod forms a positive connection with the spring assembly. For example, for this purpose, the head of the piston rod slightly encompasses one end of the spring assembly. This ensures that the spring pack can not pop out even under high pressure forces under any circumstances. The central recess has the advantage that a spring assembly with a short axially arranged in the spring assembly guide pin can be inserted into the welding head. Such a spring package has a very compact and modular form of construction.

In a development, the welding head has a water connection and a cooling water feedthrough, which is set up to cool the electrode. Alternatively or additionally, the welding head has a power connection and an insulation, which electrically isolates the frame from the electrode, so that a current path through the spring assembly and the drive is excluded.

According to one embodiment, after installation of the spring assembly, the drive, the spring assembly, a force sensor and the electrode are arranged in a line, so that a line of action of a force which acts on the electrode starting from the drive or the spring package, centric by the force sensor and the electrode runs. The linear arrangement of drive, spring assembly and electrode optimizes the Nachsetzverhalten the 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 entail. In contrast, the welding head allows optimally designed control of the Nachsetzverhaltens, which is realized in the immediate vicinity of the joint. An important

The advantage of this design is the direct power flow from the drive via the spring assembly to the electrode. Here, the spring package of Nachsetzregelung. Since the line of action of the welding force runs centrally and longitudinally through the electrode, there are no relative movements to the

Workpieces on. This leads to a high reproducibility and little electrode wear.

In one development, the welding head is set up to move the electrode in synchronism with the drive, as long as the

Electrode abuts no workpiece by a compressive force is exerted by the drive to the electrode. Furthermore, the welding head is arranged for a decoupling of the electrode from the drive and for a movement of the electrode relative to the drive by means of the spring assembly, as long as the electrode rests against a workpiece.

According to one embodiment, the spring assembly for transmitting the welding force is arranged on the electrode and designed for controlling a Nachsetzbewegung of the electrode relative to a workpiece.

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

The spring assembly thus enables optimum Nachsetzverhalten the electrode during welding. The welding head can therefore be used for the most demanding non-ferrous metal welds.

In a further development, the welding head is adapted to advance the electrode by one electrode stroke during extension of a piston rod until the electrode touches a workpiece. It is further adapted for compression of the spring assembly by a spring travel during extension of the piston rod after the electrode has placed on the workpiece, wherein the spring travel is the difference of a cylinder stroke and the electrode stroke and defines together with a bias of the spring assembly, a welding force, which the workpiece is exercised. Furthermore, the

Welding head adapted to feed the electrode by a Nachsetzweg during a welding operation using the spring assembly, wherein the compression of the spring assembly is reduced by the Nachsetzweg.

According to one embodiment, the welding head has a switch, in particular a contactless limit switch with fed-back oscillator. The switch is set up to detect a relative movement between the electrode and the piston rod, which is produced by overpressing the spring assembly after placing the electrode on a workpiece. The welding head further includes a controller, which releases a welding current when relative movement is present and releases no welding current in the absence of relative movement. In a development, the piston rod is provided with a fine thread. On the piston rod, an upper lock nut is screwed to stop with an upper adjusting nut, the upper adjusting nut strikes against a component in return of the piston rod, whereby a stroke of the piston rod is limited. Furthermore, a lower lock nut is screwed to stop with a lower adjusting nut on the piston rod, the lower adjusting nut at feed the Piston rod abuts against a component, whereby the stroke of the piston rod is limited.

The development provides a stroke limitation for a pneumatic cylinder of the welding head. As a result, the exporting force of the spring package can be precisely defined. Furthermore, the stroke limitation solves the problem that in a drive with several pneumatic cylinder packages, which are screwed one above the other, concatenated and connected in series, the lowest cylinder can not drive to the limit due to the tolerances of the cylinder.

According to one embodiment, the welding head is adapted to set a welding force between 500N and 10,000N by equipping with different spring packs.

The welding force in this case falls only slightly higher than a bias of the spring assembly, if the spring assembly is only slightly suppressed by the drive of the welding head with a dynamic travel of 1.5mm to 2mmm. The cylinder force of a pneumatic cylinder of the drive should be greater than the maximum bias of the spring pack to overcome this and to be able to overpress the spring pack. Advantageously, however, the cylinder force is not chosen to be much higher than the maximum bias of the spring pack by reducing a number of cylinder packs connected in series or down-controlling a compressed air of the cylinder. If very different spring assemblies are used, the cylinder force should be above the maximum preload of 10,000 N.

If a cylinder force of a pneumatic cylinder of a drive of the welding head is not sufficient to overpress a spring assembly with a high pretensioning, then additional cylinder packages can advantageously be screwed as cells over the pneumatic cylinder and connected in series therewith. This makes it possible to retrofit the welding head in the sense of a process substitution for resistance soldering or hot riveting, since the forces required for this process differ significantly. The spring pack allows this a particularly simple spring change. In particular, the spring assembly in this case, if necessary, by a variable bias to a stepless fine adjustment of the welding force. The welding head can be used for welding, in particular resistance welding, resistance pressure welding or resistance spot welding, for soldering, in particular resistance soldering, or for hot riveting. This offers the advantage that the welding head can be used by process substitution as a resource for different technologies.

In the welding head calibration procedure, the spring pack is inserted into the frame. The electrode of the

Welding head is placed on a workpiece. A welding pressure is repeatedly measured by means of a force sensor which is arranged between the spring assembly and the frame. A preload of the spring pack is adjusted until the measured welding pressure corresponds to a nominal value.

In the manufacturing process, the spring pack is inserted into the frame. The spring locking screw is screwed into the frame, so that the head of the piston rod is pressed by the spring locking screw on the spring assembly and applies an additional bias on the compression spring of the spring assembly. In the following, embodiments of the invention will be explained in more detail with reference to figures. Show it: 1 shows a view of a prior art welding head with a decomposition into its components, FIG.

Figure 2a is a front view with a section through the

Welding head of Figure 1,

FIG. 2b shows a side view of the welding head from FIG. 1,

FIG. 3 shows a first detailed view of the welding head from FIG. 1,

FIG. 4 shows a second detail view of the welding head from FIG. 1, FIG. 5 shows a spring package,

FIG. 6 shows a welding head with built-in spring package,

Figure 7 shows the spring assembly of Figure 5 in a detailed

Presentation,

FIG. 8 shows the components of the spring package,

FIG. 9 shows a spring assembly in the installed state in a machine,

FIG. 10 shows a stroke limitation for a pneumatic cylinder, FIG. 11 shows an operating method for a welding head with built-in spring assembly,

FIG. 12 shows an expansion of the spring assembly from a machine, FIG. 13 shows a welding head with water and electrical connection,

FIG. 14 shows a welding head with electrical insulation, FIG. 15 shows an adjusting nut with electrical insulation,

16 shows a welding head with built-in spring assembly. FIG. 1 shows a known from WO 2012045763 AI

Welding head 1 with a drive 2, an electrode 3 and an elastic element 4, for example a compression spring, which are arranged on a line of action 5. In addition, a sensor 8, a spacer sleeve 21, a piston rod 20 and an electrode guide 31 are shown. Figure 1 shows the assembly of said elements in detail.

Furthermore, FIG. 1 shows a force sensor 7, which is arranged between the elastic element 4 and the electrode 3. The force sensor 7 thus lies in the direct flow of force between the drive 2, the elastic element 4 and the electrode 3. A stop pin 72 is connected to a guide shaft 75 of the elastic element 4. It allows in conjunction with an adjusting nut 73 which is fixedly mounted by means of a rotation over O-ring on an extension of the drive 2, a simple installation and removal of the force sensor. 7

A second adjusting nut 74, which is mounted on the guide shaft 75, serves to set a bias of the elastic element 4.

FIG. 2 a shows a front view of the welding head 1 from FIG. 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. A spacer sleeve 20 and electrode guides 30 are also clearly visible. In addition to a cylinder stroke Z, a spring deflection F and an electrode stroke E, a bias voltage V is also shown in FIG. 2a, around which the elastic element 4 is prestressed. Furthermore, FIG. 2 a shows a force sensor 7 which is arranged between the elastic element 4 and the electrode 3. The force sensor 7 thus lies in the direct flow of force between the drive 2, the elastic element 4 and the electrode 3. A stop pin is connected to a guide shaft 75 of the elastic element 4. In conjunction with an adjusting nut 73, which is fixedly mounted on an extension of the drive 2 by means of an anti-twist device via an O-ring, it permits simple installation and removal of the force sensor 7. The second adjusting nut 74, which is mounted on the guide shaft 75 is, behaves as previously described.

FIG. 2b shows the welding head 1 from FIG. 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, FIG. 2b also shows a spacer sleeve 21, a sensor 8 and a connection for a voltage measuring line 50. The connection serves for a voltage measuring line 50 in this case, a measurement of a voltage drop between the electrodes. The other elements have the same function as described above.

FIG. 3 shows a first detailed view of the welding head 1 from FIG. 1. In the illustration, the guide shaft 75, which serves as a guide for the pressure spring, is highlighted. The guide shaft 75, which may also be referred to as a guide pin, extends far beyond the compression spring through other components of the welding head 1 such as the adjusting nut 73 shown in Figures 3 and 4, which cooperates with a stop pin 72. This results in that the compression spring can be replaced in practice only with great effort, since many components of the welding head 1 have to be disassembled and disassembled for this purpose.

Figure 4 shows the construction for transmitting power to the compression spring of the welding head 1 in detail. FIG. 5 shows a spring assembly 100 which at least partially replaces the components of the welding head known from the prior art, as shown in FIG. 3 and FIG. 4, and also has distinct advantages. Shown are in addition to a compression spring 104, an insert 102, which is fixed by means of a hex screw 101 and applies a biasing force on the compression spring 104 together with an adjusting nut 120. Compression springs are components which give way under load and return to their original shape after relieving, thus behaving elastically restoring. According to Hooke's law, the restoring force of a compression spring is proportional to a displacement of a point of application of force against a direction of force in which the pressure spring acts.

FIG. 6 shows a welding head 1 in which the spring assembly 100 from FIG. 5 is inserted. The spring assembly 100 is here inserted into a frame 180. An electrode 3 and a drive 2 of the welding head 1 are also clearly visible. The spring assembly 100 is additionally compressed by means of a spring-locking screw 130 by pressing a head of a piston rod onto the spring assembly 100. As a result, a defined amount of force is exerted on the head of the piston rod and the spring assembly 100, resulting in a

Adhesion results. The head of the piston rod also forms a positive connection with the spring assembly 100, which ensures that it does not jump out of the welding head 1.

FIG. 7 shows a spring assembly 100 in a detailed representation. A compression spring 104 is limited by an adjusting nut 120 with an internal thread 122 and by an insert 102 in the axial direction. The washer 102 is fastened to a guide pin 110 by means of a hexagon screw 101. For this purpose, the hexagon screw 101 is screwed into an internal thread 111 of the guide pin 110 and presses the pressure spring 104 together via the insert 102. men. This results in a defined bias of the compression spring 104. A protective sleeve 103 is loosely on the adjusting nut 120. The protective sleeve 103 is shorter than the compression spring 104 under maximum force. The outside of the protective sleeve 103 is hardened to avoid material removal by friction with the compression spring 104. It also serves as the lead. The guide pin 110 has on its underside a stop 113 and an external thread 112. The adjusting nut 120 is screwed with its internal thread 122 on the outer ßengewinde 112 of the guide pin 112. To increase the bias of the compression spring 104, the adjusting nut 120 is screwed upwards. An overall height 105 of the spring assembly 100 results from the sum of the heights of the adjusting nut 120, the compression spring 104 and the insert 102. The total height 105 corresponds approximately to the length of the guide pin 110th

FIG. 8 shows the components of the spring assembly 100 from FIG. 7. Shown in detail are the hexagon screw 101, the washer 102, the protective sleeve 103, the compression spring 104, the guide pin 110 with internal thread 111, external thread 112 and stop 113. Further, the adjusting nut 120 is located. Figure 9 shows a spring package 100 in the installed state in a machine. The spring assembly 100 with its components insert 102, guide pin 110, compression spring 104,

Protective sleeve 103 and adjusting nut 120 is first inserted into a frame 180. In the exemplary embodiment shown, a force sensor 7 is located between the underside of the spring assembly 100 and the frame 180. The frame 180 is installed, for example, in a welding head or any other machine. After inserting the force sensor 7 and the spring assembly 100 in the frame 180, a spring locking screw 130 is screwed into the frame 180 until it stops. Here, a head of a piston rod 20 by the Federfeststeil- screw 130 is pressed onto the spring assembly 100, whereby the compression spring 104 is biased by the drawn in Figure 9 Vorspannweg 131 in addition. For this purpose, the spring locking screw 130 has a stop, up to which it can be screwed into the frame 180 with an external thread. The Vorspannweg 131 results from the difference in the length of the external thread of the spring locking screw 130 relative to the thickness of the frame 180. After tightening the spring locking screw 130 forms the spring assembly 100 with the head of the piston rod 20 and the force sensor 7 a positive connection. To connect the spring assembly 100 to the head of the piston rod 20, alternatively or additionally, a positive connection is provided in order to prevent the spring assembly 100 from springing out under high pressure forces.

The biasing force of the spring assembly 100 results from an addition of three spring travel:

- The spring travel, which results from compression of the compression spring 104 when screwing in the hexagon screw, cf. For this purpose, the description of FIG. 7,

the spring travel resulting from the compression of the

Compression spring 104 by screwing the spring locking screw 130 results, and

- The spring travel, which can be additionally adjusted by the adjusting nut 120 on the spring assembly 100.

When installed, only the last spring travel is adjustable by adjusting the adjusting nut 120. When using the spring assembly 100 in a welding head, the adjustment of the bias after placing the welding head on a workpiece in response to measurements of the force sensor 7, which determines the currently set welding force.

Decisive for an executive force of the compression spring 104 is further a stroke limit of a pneumatic cylinder of the machine, in which the spring assembly 100 used is. The mechanical elements of such a stroke limitation are shown in FIG. Shown is a drive 2, which consists for example of three interlinked pneumatic cylinders as a powerhouse. A piston rod 20 of the drive is provided with a fine thread 146, on which an upper lock nut 143 is screwed to stop with an upper adjusting nut 141. The upper adjusting nut 141 strikes the drive 2 and thus forms a stroke limitation. Furthermore, a lower lock nut 144 is screwed to stop with a lower adjusting nut 142 which strikes against a stop 145 of the machine when extending the piston rod 20 and thus also limits the stroke of the piston rod 20. Furthermore, the stroke limitation solves the problem that in a drive 2 with several pneumatic cylinder packages, which are screwed together, concatenated and connected in series, the lowest cylinder can not drive to the limit due to the tolerances of the cylinder. FIG. 11 shows an operating method for a welding head with built-in spring assembly 100. A frame 180, a force sensor 7 and a piston rod 20 and a spring locking screw 130 cooperate here with the spring assembly 100 as described in FIG. In addition, an electrode 3 of the welding head, which is fixedly connected to the frame 180, as well as workpieces 6 are shown.

FIG. 11 shows the welding head in a first operating state 11, a second operating state 12, a third operating state 13 and a fourth operating state 14. The piston rod 20, the spring assembly 100, the force sensor 7 and the electrode 3 are arranged in a line of action. The welding head is operated with the aim of welding the workpieces 6 together.

The piston rod 20 develops its driving force along the vertical over the spring assembly 100, the force sensor 7, the frame 180 and finally the electrode 3 on the workpieces 6. A galvanic coating of the electrode 3 prevents corrosion of the electrode 3 and avoids contact resistance - changes. The force sensor 7 is between the spring assembly 100 and the

Frame 180 arranged. It is thus in the direct power flow between the piston rod 20, the spring assembly 100 and the electrode 3. Instead of the force sensor 7, a spacer can be installed, which can be replaced by the force sensor 7 at a later time.

A force sensor (also called a force transducer) measures a force that acts on it. For example, a dome-shaped force sensor measures a deformation of its metal body by means of strain gauges whose electrical resistance changes with the deformation.

In the first operating state 11, the welding head is in a basic position. In the following it is assumed that the piston rod 20 is driven by a pneumatic cylinder, which is retracted in the first operating state 11. The drive can also be a powerhouse, which consists of three pneumatic cylinders. The pneumatic cylinder is in this case above the piston rod 20 in the idle state. The welding head or its electrode 3 does not rest on the workpieces 6. In spring assembly 100, only a force, which results from the set bias or the three spring paths described in Figure 9 acts. In the first operating state 11, the force sensor 7 and the spring assembly 100 can be removed and replaced, provided that the assembly steps shown in FIG. 12 are carried out.

In the second operating state 12, the piston rod 20 is fully extended within the scope of the stroke limitation of FIG. The electrode 3 has covered an electrode stroke during the transition from the first operating state 11 to the second operating state 12 and placed on the workpieces 6. Since the electric 3 already rests on the workpieces 6, before the piston rod 20 abuts with its lower adjusting nut 142 against the stop 145 (shown in Figure 10), the spring assembly 100 is compressed in addition to the existing already in the first operating state 11 bias by a spring travel F. , which is drawn in Figure 11.

The spring assembly 100 is thus suppressed in the second operating state 12. The electrode 3 now presses with a defined welding force on the workpieces 6. The welding force results from the biasing force, which is composed of the three spring paths described in Figure 9, and the spring travel F. The spring travel F corresponds to the cylinder force, which over the piston rod 20 is applied to the spring assembly 100. Biasing force and cylinder force thus determine the resultant force which is exerted by the spring assembly 100 on the workpieces 6. When the force sensor 7 is inserted into the frame 180, the exact welding force can be determined in the second operating state 12 and adjusted with the aid of the adjusting nut 120 of the spring assembly 100 shown in the preceding figures. Depending on the design of the spring assembly 100, the welding force can be set, for example, between 500 N and 10,000 N, wherein a plurality of spring assemblies with different degrees of compression springs can be provided and optionally used to cover this range of values.

The bias of the compression spring is set, for example, between 1.8 and 8.5 mm. The spring travel F is set, for example, between 1 and 3 mm, preferably at 1.5 mm. Depending on the design, other limits and guide values for the welding force, the spring travel F and the preload may result. Using a Beros 162 (shown in FIG. 16), it is possible to determine whether a relative movement of the electrode 3 relative to the piston rod 20, ie an overpressure of the spring assembly 100, has taken place. If the Beros 162 is polled positively (see FIG. 16), a welding current is generated released, whereby a welding of the workpieces 6 takes place.

The welding process itself 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 workpieces heat up and become doughy. In this case, the electrode 3 sinks by a Nachsetzweg N in the workpieces 6 a. This results in a Nachsetzbewegung of the electrode 3 in the yielding material of the workpieces. 6

Correspondingly, the compression of the spring assembly 100 decreases from the spring travel F by the Nachsetzweg N. Due to the structure of the welding head repositioning is very fast, and the collapse of the welding force is minimized. With the reduction of the spring travel F has also the

Force of the compression spring of the spring pack 100 reduced by the corresponding amount. This loss of power is negligible due to the short distances in the millimeter range when repositioning.

The fourth operating state 14 shows the case that the piston rod 20 is fully extended in the context of its stroke limitation, but no workpieces 6 are present, so the electrode 3 is pushed into the void. In this case, therefore, no compression of the spring package 100 takes place about the spring travel F, i. the spring assembly 100 is not acted upon in the fourth operating state 14. This can be detected by the Bero 162 of Figure 16 and is used to control whether workpieces are present for welding. The spring travel F is in this case 0. This can be determined by the Bero 162 of Figure 16, whereupon the welding current is not released.

In summary, the electrode 3 moves as long as synchronous to the movement of the piston rod 20, as it rests against any workpiece 6. As soon as the electrode 3 abuts against a workpiece 6, it is decoupled from the piston rod 20 and moved relative to the movement of the piston rod 20. This is made possible by the spring assembly 100.

FIG. 12 shows a removal of a spring assembly 100 from a machine, for example from the welding head described above. The construction of the elements shown here corresponds to the exemplary embodiments of FIGS. 9 and 11. In order to remove the spring assembly 100, which is inserted together with a force sensor 7 into a frame 180, in a first assembly step 61 a spring locking screw 130 is provided which, as in FIG Figure 9 described, with the spring assembly 100 cooperates, solved. Thus, this coupling exerts no more power on the spring assembly 100. Since the spring assembly 100 is now loose in the frame 180, in the second assembly step 62, the force sensor 7 can be pulled out, whereby the spring assembly 100 slips or falls to the bottom of the frame 180. Then, the spring package 100 is removed in a third assembly step 63 itself from the frame 180 and replaced if necessary.

The installation of the spring assembly 100 or of the force sensor 7 takes place accordingly in the reverse order of the assembly steps. Finally, after inserting the force sensor 7, the spring locking screw 130 must then be tightened again until it stops.

FIG. 13 shows a welding head 1 with a power connection 171 and a water connection 172. The connections are located on the rear side of the welding head 1. The water connection 172 serves to water-cool the electrode 3 by means of a cooling-water feed-through.

FIG. 14 shows a section of a welding head with a spring assembly 100, a frame 180 and an insulation 150, which, during welding, have a correct current path through

Workpiece guaranteed. The insulation 150 is attached as an insulating pressure plate between the frame 180 and the lower part of the welding head with the electrode. FIG. 15 shows a sectional view of an adjusting nut 120 with electrical insulation for use in the spring packs shown in FIG. 5, FIG. 6, FIG. 7, FIG. 9, FIG. 11, FIG. 12, FIG. 14 and FIG. The adjusting nut

120 has a recess in which the lower end of the compression spring can be positioned. The diameter of the recess therefore corresponds to the spring outer diameter 121. For screwing the adjusting nut 120 on the outer thread of the guide pin, the adjusting nut 120 has an internal thread 122nd

For electrical insulation of the spring assembly, the adjusting nut 120 consists of two layers. The outer layer, which is shown in FIG. 15 by hatching sloping to the right, consists of a non-conductive plastic. From the same material of the stop 113 shown in Figures 7 and 8 of the guide pin 110 is made. Through all these measures, the current path through the spring assembly and in consequence the piston rod is excluded.

FIG. 16 shows a complete welding head 1 which operates with a quickly and easily replaceable spring assembly 100. In addition to a drive 2, the upper adjusting nut 141 already shown and explained in FIG. 10, upper lock nut 143, lower adjusting nut 142 and lower lock nut 144 are shown. Furthermore, a Bero 162 with a knurled screw 161 for setting the Beros 162 for a partial query as shown in the context of Figure 11. The spring package 100 is inserted into a frame 180.

An adjusting nut of the spring assembly 100 is still accessible even when installed from the outside to adjust the bias. Instead of a force sensor, a shim 165 is used in the welding head 1 shown. If necessary, this can be replaced by a force sensor. An electrode 3 of the welding head 1 is held by an electrode holder 166. The described embodiments, developments and embodiments can be combined freely with each other.

Claims

Patent claims / patent claims

1. Welding head (1),

with a drive (2) and a movably mounted electrode (3),

with an installation position for receiving a self-contained and replaceable spring package (100), the spring package (100) being arranged in the installation position in the power flow between the drive (2) and the electrode (3).

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

with a frame (180) which is set up to accommodate the spring package (100).

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

in which the frame (180) has a recess through which the spring assembly (100), in particular for adjusting a preload of the spring assembly (100), remains accessible from the outside even when installed.

Welding head (1) according to claim 2 or 3,

in which the frame (180) has a round opening with an internal thread in the axial direction of the spring assembly (100).

5. Welding head (1) according to claim 4,

with a piston rod (20), which is movably guided by a spring locking screw (130), which forms a rear stop for a head of the piston rod (20),

in which the spring locking screw (130) can be screwed into the frame (180) with an external thread in such a way that the head of the piston rod (20) is pressed onto the spring assembly (100) by the spring locking screw (130) and an additional preload is applied to the compression spring ( 104) of

Spring package (100) applies.

6. Welding head (1) according to claim 5, in which the head of the piston rod (20) is shaped to produce a positive connection with the spring assembly (100), and/or

in which the head of the piston rod (20) has a central recess which is dimensioned to receive an end of a rigid guide pin (110) arranged axially in the spring assembly (100) when the spring assembly (100) is compressed.

7. Welding head (1) according to one of claims 2 to 6,

with a water connection (172) and a cooling water feedthrough, set up to cool the electrode (3), and/or

with a power connection (171) and insulation (150), which electrically isolates the frame (180) from the electrode (3), so that a current path through the spring package (100) and the drive (2) is excluded.

8. Welding head (1) according to one of the preceding claims, - in which, after installation of the spring assembly (100), the drive (2), the spring assembly (100), a force sensor (7) and the electrode (3) are arranged in a line , so that a line of action (5) of a force, which acts on the electrode (3) starting from the drive (2) or the spring assembly (100), runs centrally through the force sensor (7) and the electrode (3).

9. Welding head (1) according to one of the preceding claims, set up to move the electrode (3) synchronously with the drive (2), as long as the electrode (3) is not in contact with any workpiece, by applying a pressure force from the drive (2) to the electrode ( 3) is exercised, and

set up to decouple the electrode (3) from the drive (2) and to move the electrode (3) relative to the drive (2) by means of the spring package (100), as long as the electrode (3) is on a workpiece (6). applied.

10. Welding head (1) according to one of the preceding claims, in which the spring assembly (100) is arranged to transmit the welding force to the electrode (3) and is designed to regulate a follow-up movement of the electrode (3) relative to a workpiece (6).

11. Welding head (1) according to one of the preceding claims, set up to advance the electrode (3) by one electrode stroke while extending a piston rod (20) until the electrode (3) touches down on a workpiece (6),

set up to compress the spring package (100) by a spring travel (F) during the extension of the piston rod (20) after the electrode (3) has placed on the workpiece (6), the spring travel (F) being the difference between a cylinder stroke and the Electrode hub (E) forms and, together with a preload of the spring package (100), defines a welding force which is exerted on the workpiece (6), and

set up to advance the electrode (3) by an additional travel (N) during a welding process using the spring package (100), the compression of the spring package (100) being reduced by the additional travel (N).

12. Welding head (1) according to claim 11,

- with a switch (162), in particular a non-contact limit switch with a feedback oscillator,

wherein the switch (162) is set up to determine a relative movement between the electrode (3) and the piston rod (20), which is caused by overpressing the spring package (100) after placing the electrode (3).

Workpiece (6) results, and

with a control which releases a welding current when there is relative movement and does not release a welding current when there is no relative movement.

13. Welding head (1) according to one of the preceding claims, in which the piston rod (20) is provided with a fine thread (146), in which an upper lock nut (143) is screwed to the stop on the piston rod (20) with an upper adjusting nut (141), the upper adjusting nut (141) striking against a component when the piston rod (20) is returned, thereby causing a stroke of the piston rod (20) is limited, in which a lower lock nut (145) is screwed to the stop with a lower adjusting nut (142) on the piston rod (20), the lower adjusting nut (142) striking against a component when the piston rod (20) is advanced , which limits the stroke of the piston rod (20).

4. Welding head (1) according to claim 13, set up to adjust a welding force between 500N and 10,000N by equipping it with different spring assemblies (100).

5. Use of the welding head (1) according to one of the preceding claims for welding, in particular resistance welding, resistance pressure welding or resistance spot welding, soldering, in particular resistance soldering, or hot riveting.

16. Calibration method for the welding head (1) according to one of claims 2 to 14,

in which the spring package (100) is inserted into the frame (180),

in which the electrode (3) of the welding head (1) is placed on a workpiece (6),

in which a welding pressure is repeatedly measured using a force sensor (7), which is arranged between the spring package (100) and the frame (180), and

in which a preload of the spring package (100) is adjusted until the measured welding pressure corresponds to a target value.

. Manufacturing method for a welding head (1) according to one of claims 1 to 14 with the features of the claim in which the spring package (100) is inserted into the frame (180), and

in which the spring locking screw (130) is screwed into the frame (180), so that the head of the piston rod (20) is pressed onto the spring package (100) by the spring locking screw (130) and an additional preload is applied to the compression spring (104) of the spring package (100).