DE202022003003U1 - Laser welding gun - Google Patents

Abstract

Laser welding gun (10) for producing a weld seam for joining workpieces (36, 37), in particular in an overlap joint, comprising
a support device (11) extending along a longitudinal axis (12),
an optical coupling element (13) which is provided for coupling a laser beam (16) onto a welding zone (23) in the laser welding gun (10) and which is arranged or formed on the support device (11),
a first clamping jaw (18) in the form of a holding element which is provided for holding the workpieces (36, 37) during the welding process, which is arranged or formed in the beam direction (16a) of the laser beam (16) in front of the welding zone (23), wherein the first clamping jaw (18) is arranged or formed axially displaceable along the support device (11) on the support device (11), in particular via a first support arm (17), or wherein the first clamping jaw (18) is a component of the support device (11), which is axially displaceable, and
a drive (24) provided for displacing the first clamping jaw (18) or the first support arm (17) or the support device (11) between a starting position and a welding position, or an interface to a drive (24) provided for displacing the first clamping jaw (18) or the first support arm (17) or the support device (11) between a starting position and a welding position,
characterized,
that the laser welding gun (10) is provided for laser welding of workpieces in a vacuum,
that the first clamping jaw (18) is designed as a first vacuum chamber (19), or that the first clamping jaw (18) has a first vacuum chamber (19),
that the first vacuum chamber (19) is optically coupled to the optical coupling element (15),
that an exit opening (26) for the laser beam (16) is formed in the first clamping jaw (18) and that the first vacuum chamber (19) is arranged or formed around the exit opening (26) in the beam direction (16a) of the laser beam (16) on the exit side of the exit opening (26), wherein the first vacuum chamber (19) is configured in such a way that that it encloses the welding zone (23) in the welding position and generates a limited local vacuum around the welding zone (23).

Description

The present invention relates firstly to a laser welding gun according to the preamble of claim 1.

The present invention is located in the technical field of laser welding in a vacuum. Laser welding in a vacuum is a process combination of the established joining techniques laser welding and electron beam welding.

In laser welding, processing laser light generated by a laser device is focused onto a small spot using focusing optics. Since the energy density of the laser light is very high, the material to be welded is quickly melted and partially vaporized, and a weld seam is quickly formed. Laser welding usually takes place at atmospheric pressure.

In electron beam welding, the beam is generated in the so-called electron beam gun by heating a hot cathode and applying an accelerating voltage. In the common variants of electron beam generators, the hot cathode is a wearing part and must be replaced after a few hours, depending on the material being welded. Installation errors, contamination or other changes to this delicate component immediately result in a change in the beam properties and thus in the quality of the weld seam. The beam is formed and focused by magnetic coils. In electron beam welding, a high vacuum is necessary due to the process. This is because a collision of the electrons with the air molecules leads to an expansion of the beam and thus a reduction in the intensity on the workpiece.

In recent times, laser welding in a vacuum has developed, with increasingly new and constantly expanding areas of application. Laser welding in a vacuum or laser beam welding in a vacuum is a process modification of laser welding or laser beam welding. It combines the vacuum technology that is normally used in electron beam welding with the established joining technology of laser welding. The reduction in the boiling temperature that can be achieved in this way means that less energy is required to vaporize the material to be processed, usually metal. While the size of the vapor capillary is largely determined by the beam diameter, a reduction in temperature in the vapor capillary also leads to a reduction in the size of the surrounding melt pool. The tendency for spatter and pores is significantly reduced. In addition to improving the quality of the laser weld seam, laser welding in a vacuum also leads to a significantly reduced heat input, with the same welding depth. This effect is particularly useful for temperature-sensitive materials or materials that are susceptible to hot cracking, or when welding is to be carried out with particularly low distortion.

Laser welding in a vacuum is usually carried out in vacuum chambers designed for this purpose. For example, welding can be carried out in stationary vacuum chambers. Here, the workpieces to be welded are placed in the vacuum chamber. The welding process then takes place within the vacuum chamber. However, not all types of welding processes are possible in stationary vacuum chambers. For example, in the field of welding car bodies, a stationary vacuum welding chamber is not suitable. This would have to be far too large, which is at least uneconomical.

When welding car bodies, locally acting welding devices, also known as welding guns, are therefore primarily used.

Resistance spot welding is currently the predominant welding method for welding car bodies. Spot welding guns are used here. The components to be joined are positioned between two electrodes, which press the components to be welded together. The electrodes are then subjected to a welding current, which heats up the joint. This creates a point-by-point heating so that the components to be welded bond together under pressure. The electrodes are then removed from the welding zone and the next welding point can be set. The principle of resistance spot welding is that current is supplied to the components to be welded via the electrodes under the effect of force. One of the problems with resistance spot welding is the so-called current bypass. If the welding points are not far enough apart, the welding current flows not only over the current welding point, but also over neighboring welding points. Problems can also arise if workpieces of different thicknesses, such as sheet metal, are to be welded together. Another disadvantage is electrode wear. There is therefore a need to find alternatives to resistance spot welding in the field of locally operating welding equipment.

In this regard, it has already become known to use welding guns designed for laser beam welding when welding car bodies. Laser welding guns are an alternative clamping and joining technology to resistance spot welding. In contrast to resistance spot welding, laser welding guns not only avoid the above disadvantages, but also offer a higher welding speed and a higher transferable force of the weld seams.

Such a laser welding gun is used, for example, in the EP 2 149 421 B1 described. The known laser welding gun has a device for generating a laser beam. The laser is a fiber laser. A collimator and a wobble generator are also provided. These components are located on a movable first, upper gun arm. The components mentioned are arranged in a housing on the upper gun arm. The laser beams can only exit the housing through an exit slot. The laser beam is completely enclosed by the housing. During the welding process, the upper gun arm is moved in the direction of the component to be welded so that the exit slot sits on the component surface and forms an upper pressure piece. This known solution also features a lower gun arm, at the free end of which there is also a pressure piece. The pressure pieces have the function of joining the components together precisely. However, this laser welding gun is not designed for laser welding in a vacuum.

The WO 2014/063153 A1 also relates to a welding gun, similar to the above solution. Here, the gun arm has a suction device at its free end, which concerns a holding element for the component to be processed, which can generate a negative pressure. The purpose of this design is, however, to suck out impurities that arise during the welding process, but not to provide a vacuum chamber for laser welding.

In the US$5,170,028 B, a component to be welded is held in a clamping device which has a lower housing and an upper housing. A vacuum is set in the upper housing. The two chambers are connected to one another via a sealing element which can be made of rubber. However, this known solution relates to a method for electron beam welding.

In the EN 10 2019 102 233 A1 describes a method for welding components. The welding process takes place at a system pressure that is lower than atmospheric pressure. However, welding in a vacuum is explicitly described as disadvantageous. Since the process requirements for welding with such a system pressure are different from the process requirements for welding in a vacuum, the teaching of this known publication cannot simply be transferred to the field of application of laser welding in a vacuum. Another problem occurs with the known solution when two workpieces are welded in an overlap joint. With the known solution, it cannot be guaranteed that there is a "zero gap" between the workpiece surfaces during the welding process. This problem is explained in more detail below in connection with the description of the invention.

All previously described state-of-the-art solutions are not suitable for laser welding in a vacuum.

Based on the above-mentioned prior art, the present invention is therefore based on the object of providing a laser welding gun that works with vacuum and combines the process advantages of resistance spot welding, laser beam welding and electron beam welding.

This object is achieved according to the invention by the laser welding gun with the features of independent claim 1. Further features and details of the present invention emerge from the subclaims, the description and the drawings.

First, the basic relationships of the laser welding gun according to the invention are described.

The basic idea of the present invention is that laser beam welding is carried out in a vacuum, whereby the vacuum is a limited local vacuum. This means that the vacuum is limited to a specific area or a specific volume. This area is in particular the welding zone in which the actual welding process takes place, or the immediate surroundings of the welding zone. The vacuum is limited to this specific area, i.e. locally. The vacuum is thus only provided where it is actually needed for the welding process. In comparison to stationary vacuum chambers, this has the advantage, among other things, that only very short extraction times are required. This is because the vacuum required for the welding process is only generated in a very small volume around the welding zone or the welding point. The welding zone is in particular especially the molten area in which the welding process itself takes place.

The laser welding gun is preferably used in the process of laser beam welding in a local vacuum. The laser welding gun is in particular a mobile and/or locally operating laser welding gun. The laser welding gun is in particular a mobile welding device that is guided to the welding location, for example by hand or by means of a manipulator, such as an industrial robot.

The laser welding gun according to the invention can be used for a wide range of materials and material combinations. The present invention is particularly suitable for welding various aluminum alloys, steel alloys, metallic lightweight materials and the like, which are of great interest in particular for the automotive industry, although the invention is of course not limited to these metals and other types of metals can also be welded with the laser welding gun. The invention is intended to be used in particular in the manufacture of bodywork components. Resistance spot welding is currently still a predominant welding method here. Of course, the invention is not limited to this specific application. Rather, the invention can be used wherever locally acting welding devices are advantageous.

The basic idea of the solution according to the invention is that the vacuum required for the welding process is generated in a very small volume around the welding zone. The clamping technology also functions as a vacuum chamber, with the laser processing taking place in the vacuum chamber to enable a vacuum welding process. The laser beam must therefore be positioned within the vacuum chamber. At the same time, a zero gap can always be achieved during the welding process, which is described in detail below.

In one application, laser welding processes are automated, in particular using robots, i.e. robot-guided. With the laser welding gun according to the invention, it is particularly possible to attach it to a manipulator, for example to a robot arm. In particular, it is possible to replace and exchange the laser welding gun according to the invention with existing resistance spot welding guns. Complex clamping devices, such as those commonly used in stationary vacuum chambers or in remote laser welding, can be omitted because the clamping technology is integrated directly into the laser welding gun.

The welding process, for example the creation of a weld seam, takes place within the laser welding gun. For this purpose, the laser welding gun preferably has one or two clamping jaws in a manner known per se. A clamping jaw is in particular a holding element which holds a workpiece to be processed during a processing process, for example a welding process, and fixes it in the processing position. According to the present invention, the clamping jaws also simultaneously fulfill the function of the vacuum chamber. In principle, it is sufficient if only one such clamping jaw with vacuum chamber function is present. The clamping jaws are an essential component of the laser welding gun. This is because they press the workpiece or workpieces to be welded together. This is a very important requirement because during the vacuum laser welding process there must be a zero gap between the components to be welded. This means that there is no gap between the components to be welded. If there were a gap between the components to be welded, this would have a negative effect on the vacuum and thus on the vacuum laser welding process, as the gap could result in a leaky vacuum chamber. The zero gap is therefore important so that the sheets shield the weld seam from the ambient pressure when pressed together and vacuum welding is made possible. Furthermore, avoiding a gap between the components to be welded, i.e. creating a zero gap, is also very important because otherwise air, especially drafts, can or does penetrate between the workpieces to be welded, which then pushes the molten material into the vacuum chamber due to the pressure difference.

In a preferred embodiment, the laser welding gun is provided for lap joint welding. When lap joint welding, several workpieces, for example metal sheets, lie on top of one another, preferably in parallel, and overlap. One workpiece can protrude over another. For example, two workpieces can lie on one level and be overlapped by a third workpiece.

For example, two workpieces lying on top of each other, for example metal sheets, are welded together, preferably in an overlapping joint, using the laser welding gun according to the invention. As the sheet thickness increases, the stiffness of the sheet also increases. With increased sheet thickness, the The clamping force of the clamping jaws can be increased in order to create a zero gap between the sheets. Of course, the invention is not limited to this application example.

According to the invention, a laser welding gun for producing a weld seam for joining workpieces, preferably in an overlap joint, is provided, which has the features of independent claim 1.

In a conventional manner, the laser welding gun first has a support device that extends along a longitudinal axis. The individual components of the laser welding gun are arranged on the support device. The support device can be, for example, a support arm, a support frame, a support structure or the like. The laser welding gun can be mounted or mountable on a manipulator, such as a robot arm, via the support device, or can also be guided by hand if necessary.

The laser welding gun also has an optical coupling element, which is provided for coupling a laser beam onto/into a welding zone in the laser welding gun. A generated laser beam is coupled in via the optical coupling element and directed in the laser welding gun onto the workpiece to be processed and positioned on the workpiece. How this is implemented in detail is explained in more detail in the further course of the description using preferred exemplary embodiments. The optical coupling element is, for example, a coupling glass, which preferably also takes on the function of a protective glass. In a preferred embodiment, which is described in more detail below, the optical coupling element separates the atmospheric pressure outside the laser welding gun from the pressure inside the vacuum chamber. The optical coupling element is arranged or formed on the support device. In the first case, it is an independent element that is mounted on the support device. In the second case, it is an integral part of the support device.

For example, a sensor element can be assigned to the optical coupling element, which is provided in such a way that it is able to detect contamination of the optical coupling element. This is because a dirty optical coupling element negatively influences the laser beam and thus the laser welding process.

Furthermore, the laser welding gun has a first clamping jaw for holding the workpiece(s) during the welding process. A clamping jaw is in particular a device by means of which the workpiece(s) to be processed are picked up, held and fixed during the welding process.

The first clamping jaw is arranged or designed in front of the welding zone in the direction of the laser beam. The first clamping jaw thus generates a clamping force acting on the workpiece to be welded from above. The first clamping jaw is arranged or designed to be axially displaceable along the support device. In this way, the first clamping jaw can be placed on the workpiece to be welded and lifted off again. For example, the first clamping jaw can be arranged on the support device so that it can be axially displaced via a first support arm. This means that the first clamping jaw or the first support arm is movable, whereby the first clamping jaw or the first support arm can preferably be moved linearly along the longitudinal axis. Either the first clamping jaw or the first support arm is an independent component which is arranged movably on the support device. Or the first clamping jaw or the first support arm is designed as an integral part of the support device. In this case, the entire support device must be correspondingly movable in order to generate the mobility mentioned.

The first clamping jaw is moved in the direction of the workpiece to be processed to initiate a welding process and, after the welding process has been completed, is moved away from the now welded workpiece so that it can be removed or taken away from the laser welding gun. The workpiece to be welded, for example two sheets of metal to be welded, is pressed via the first clamping jaw in such a way that a zero gap is created between the clamping jaw and the workpiece, as well as between the two sheets of metal.

In order to be able to realize the mobility of the first clamping jaw and in particular of the first support arm, the laser welding gun has a drive that is provided for moving the first clamping jaw or the first support arm or the support device between a starting position and a welding position. In this case, the drive is part of the laser welding gun and is preferably arranged on the support device. In another embodiment, the laser welding gun has an interface to a drive that is provided for moving the first clamping jaw or the first support arm or the support device between a starting position and a welding position. is provided. In this case, the drive itself is not part of the laser welding gun. The drive force is then generated outside the laser welding gun and transmitted via a suitable interface, for example a cable or hose.

The invention is not limited to specific types of drive. For example, the drive is designed such that it generates a uniform, in particular linear, travel movement. For example, the drive can also be designed to generate a speed variation. The drive is designed, for example, as a pneumatic drive or as a hydraulic drive. In a preferred embodiment, however, the drive is designed as an electric drive, for example as an electric motor, such as a servo motor. In the case of an electric drive, this preferably also includes a converter device that is provided in such a way that it can translate the motor rotation into a linear translation movement, for example around a ball screw.

According to the invention, the laser welding gun, as generally described above, is provided for laser welding of workpieces in a vacuum.

For this purpose, the first clamping jaw is designed as a first vacuum chamber, or the first clamping jaw has a first vacuum chamber. In the first case, the first vacuum chamber is an integral part of the first clamping jaw. In the second case, the first vacuum chamber is an independent component which is/will be arranged on the first clamping jaw.

The first vacuum chamber is optically coupled to the optical coupling element so that the generated laser beam, which is coupled into the laser welding gun via the optical coupling element, can be positioned in the first vacuum chamber and thus, when the laser welding gun is in operation, in the welding zone on the workpiece to be welded.

An exit opening for the laser beam is formed in the first clamping jaw. The laser beam exits from the exit opening and is then positioned in the welding zone. The invention is not restricted to specific designs of the exit opening. It is only important that the exit opening is dimensioned such that the laser beam exiting it can reach and cover the entire welding zone. For example, the exit opening can be round, oval or angular in any way. In a preferred design, the exit opening is designed as an exit slot. A slot is in particular an elongated narrow opening whose length is many times greater than its width. For example, the exit opening can be an elongated hole. An elongated hole is in particular an elongated hole or groove whose narrow sides are closed off by semicircles whose diameter corresponds to the width of the elongated hole. The long sides of the elongated hole preferably run parallel.

The first vacuum chamber is arranged or formed around the exit opening in the beam direction of the laser beam on the exit side of the exit opening. This is described in more detail below in connection with preferred embodiments of the vacuum chamber. The first vacuum chamber is configured as generally described above, such that it encloses the welding zone in the welding position and generates a limited local vacuum around the welding zone.

According to the invention, the weld seam is created within the first clamping jaw, which simultaneously fulfils the function of a vacuum chamber. There are therefore two energetic input variables for the welding process: the laser radiation and the vacuum environment in the vacuum chamber.

In a preferred embodiment, the laser welding gun has a second clamping jaw for holding the workpiece(s) during the welding process. The second clamping jaw is arranged or formed behind or below the welding zone in the direction of the laser beam. The second clamping jaw thus generates a clamping force acting on the workpiece to be welded from below. The second clamping jaw is either arranged or formed on the support device so as to be axially displaceable along the support device. Or the second clamping jaw is arranged fixedly on the support device. For example, the second clamping jaw can be arranged on the support device via a second support arm which is arranged on the support device so as to be axially displaceable along the support device, or which is arranged fixedly on the support device, or which is part of the support device. The welding zone is formed between the first and second clamping jaw. The second clamping jaw is also preferably designed as a second vacuum chamber, or the second clamping jaw has a second vacuum chamber. With regard to the design and function of the second support arm, the second clamping jaw and the second vacuum chamber, reference is also made to the explanations regarding the first support arm, the first clamping jaw and the first vacuum chamber.

In principle, one-sided accessibility by placing the first, upper clamping jaw or the first vacuum chamber on the workpiece to be welded is sufficient for the invention. A second clamping jaw or a second vacuum chamber can be omitted here. The required sealing is then achieved in particular by pressing the first, upper vacuum chamber on one side and welding takes place, instead of through-welding, for example into the lower workpiece when two workpieces lying on top of one another, for example two sheets of metal, are welded together. In the case of through-welding, the second, lower clamping jaw is particularly implemented with the second, lower vacuum chamber.

Preferably, in the same way as described above in connection with the first clamping jaw, the second clamping jaw can also have a corresponding outlet opening, although this is not absolutely necessary.

Preferably, a force measuring device is arranged or formed on or in the first clamping jaw and/or the second clamping jaw, in particular on or in the first support arm and/or the second support arm, which is provided in such a way that it is able to monitor the forces applied to the workpieces to be welded during the welding process. The force measuring device is designed, for example, in the form of a load cell. Preferably, the force measuring device is only loaded or can be loaded in tension or compression on one axis. This provides a real measurement result and prevents the force measuring device from being destroyed, for example if the transverse force is too high.

The laser welding gun preferably has a device for generating a laser beam, which is then arranged on the support device. The device has a number of components, with at least some of the components then being arranged on the support device. In this case, the laser beam is generated inside the laser welding gun, above the optical coupling element. Or, in another embodiment, the laser welding gun has an interface to a device for generating a laser beam. In this case, the laser beam is generated outside the laser welding gun and coupled into the laser welding gun via the optical coupling element. The device for generating the laser beam does not necessarily have to be installed on the laser welding gun. The device firstly has a laser source, whereby all types of laser sources can be used, possibly also electron beam sources. In addition, the device preferably also has laser optics. 0 to 3D optics can be installed. Furthermore, the device can also have a collimator, a device for optics manipulation, and the like. The device, or at least individual components thereof, can be arranged on the support device so that it can move, in particular linearly, in particular in the longitudinal direction of the support device. The movable components can thus also be moved when the clamping jaws of the laser welding gun are firmly clamped.

In a further embodiment, the laser welding gun preferably has a device for deflecting a generated laser beam, which is arranged on the support device. Or, in another embodiment, the laser welding gun has an interface to a device for deflecting a generated laser beam, wherein the device for deflecting the generated laser beam is preferably linearly displaceable. Such a deflection device is also referred to as a laser scanner. It enables the surfaces of the workpiece to be processed to be scanned in a line-like and/or grid-like manner in order to be able to process it. Instead of a laser scanner, a fixed optics could also be used, which is then moved, preferably linearly, in the direction of the weld seam. It is preferably implemented that the deflection device is arranged on the support device so that it can be moved, in particular linearly, for example along the longitudinal axis of the support device. The deflection device can therefore also be moved when the clamping jaws of the laser welding gun are firmly clamped.

By means of a movable device for generating the laser beam and/or a movable deflection device, for example, the focus distance of the generated laser beam can be varied. In particular, the laser beam striking the workpiece can be defocused. The inventors have found that this optimizes the end craters of a weld seam and in particular reduces the formation of end crater cracks. Such end craters or end crater avoidance is/are described in detail below in connection with the method according to the invention.

In addition, the laser welding gun can have a laser head, which is preferably arranged on the support device and which connects the device for generating the laser beam and/or the device for deflecting the laser beam, or at least individual components thereof, to the laser welding gun, for example the laser welding gun. The optical coupling element can be arranged or formed in the laser head.

In the following, some preferred embodiments are described as to how the first and/or second vacuum chamber is preferably designed.

Preferably, the first vacuum chamber and/or the second vacuum chamber has a contact surface for the workpieces. The vacuum chamber comes into contact with the workpiece via the contact surface during the clamping process and remains in contact with it during the subsequent welding process. During the clamping process, the workpiece to be welded is held by the clamping jaw(s) or the vacuum chamber(s) with a clamping force, which is then applied to the workpiece surface via the contact surface of the clamping jaw(s), in particular from their vacuum chamber(s).

The first, upper vacuum chamber is preferably open in the direction of the welding zone. The first vacuum chamber is delimited by a vacuum chamber wall, in particular by a circumferential web, which projects in the direction of the welding zone, i.e. downwards, in particular from the first clamping jaw. The free end of the first vacuum chamber wall, in particular of the web, is preferably designed as the contact surface described above. For example, the first clamping jaw has a base plate or basic structure provided with an exit opening, wherein the generated laser beam passes through the exit opening from above in order to be positioned on the workpiece to be processed. With regard to the exit opening, reference is also made to the corresponding explanations above. This exit opening defines or delimits in particular the welding zone. The vacuum chamber wall, in particular the circumferential web, then projects downwards from this base plate or basic structure of the clamping jaw, i.e. in the direction of the welding zone. The vacuum chamber wall is designed in particular such that it surrounds the exit opening for the laser beam. In a preferred embodiment, the vacuum chamber wall, in particular the surrounding web, adjoins the outlet opening directly and without offset. The contour of the vacuum chamber wall preferably corresponds to the contour of the outlet opening. In this case, the vacuum chamber wall can be viewed as a type of extension of the outlet opening. In another embodiment, the vacuum chamber wall, in particular the surrounding web, can be provided at a short distance from the outlet opening. In this case, there is a slight offset between the outlet opening and the vacuum chamber wall. For example, this offset can be 1 cm or less. In this case, the contour of the vacuum chamber wall does not necessarily have to match the contour of the outlet opening. The closer the vacuum chamber wall is to the outlet opening, the smaller the volume that has to be evacuated for the welding process to be carried out.

The vacuum chamber, and in particular the vacuum chamber wall, is the element or component of the clamping jaw that first comes into contact with the workpiece to be machined, in particular via the contact surface. The vacuum chamber therefore also takes on the function of a clamping jaw.

In the same way, additionally or alternatively, the second, lower vacuum chamber can also be open in the direction of the welding zone, wherein the second vacuum chamber is delimited by a vacuum chamber wall, in particular by a circumferential web, which projects in the direction of the welding zone, in particular from a base plate or base structure, this time upwards. The free end of the second vacuum chamber wall, in particular of the web, is preferably designed as the contact surface described above.

In this embodiment, the clamping jaw or the vacuum chamber, which is open at the bottom or at the top, i.e. in any case in the direction of the workpiece surface, is delimited by a vacuum chamber wall, in particular with a circumferential web. This creates an elastic impression of the clamping jaw in the workpiece when it hits the vacuum chamber wall, preferably the contact surface, which enables the vacuum to be generated because it shields the welding zone, which is located inside the vacuum chamber wall, from atmospheric pressure. A further effect of this impression is that the workpiece deforms elastically at this point, whereby the required zero gap can be achieved, as generally described above. The vacuum chamber wall seals the welding zone against the ambient pressure. The welding zone is located inside the vacuum chamber wall, for example the circumferential web, in order to ensure vacuum tightness on the one hand, but also protection from the laser beams on the other. The vacuum chamber wall, for example the web, also enables any required zero gap. The vacuum chamber wall, for example the web, can have a width of 1 mm, for example.

In a preferred development of this embodiment, a sealing device, in particular in the form of a sealing ring, is provided outside the vacuum chamber wall, in particular the circumferential web, or in the vacuum chamber wall, in particular in the web, for example in the contact surface. provided. To fix the sealing device, a groove, preferably wedge-shaped, dovetail-shaped or of another design, is optionally provided for receiving the sealing device. This is a design in which a workpiece deformation such as that described in the previously described embodiment is counteracted. For this purpose, a sealing device, for example in the form of a sealing ring, is provided outside the vacuum chamber wall, in particular the surrounding web, or within a correspondingly wide vacuum chamber wall, in particular a web. To fix the sealing device, this is inserted into the groove, which is formed, for example, in the contact surface. The required zero gap is again achieved via the vacuum chamber wall, in particular the web, which, spatially speaking, is located within the sealing device, i.e. closer to the outlet opening than the sealing device. When the clamping jaw is actuated, the sealing device first touches the workpiece and is compressed. This creates the vacuum seal. As the workpieces are moved closer together, the vacuum chamber wall, in particular the web, hits the workpiece surface and presses the workpieces together, for example when two workpieces are welded in an overlap joint, whereby the zero gap can be achieved. However, since the vacuum chamber wall, in particular the web, no longer has to be shielded from atmospheric pressure, the vacuum chamber wall, in particular the web, can be made wider in this embodiment, which creates a larger contact surface and prevents permanent deformation of the workpiece.

Preferably, the first vacuum chamber and/or the second vacuum chamber is/are connected to an evacuation device to generate a negative pressure. The desired negative pressure or the desired vacuum is generated in the vacuum chamber(s) via the evacuation device. Since the vacuum chambers have only a very small volume to be evacuated, particularly in comparison to stationary vacuum chambers, the evacuation can take place quickly and with little effort. Depending on the design, both vacuum chambers can be connected to one and the same evacuation device, or each to its own individual evacuation device.

Preferably, the first clamping jaw and/or the second clamping jaw is/are provided, in particular via the first vacuum chamber and/or the second vacuum chamber, preferably via the respective contact surface, for exerting a defined clamping force on the workpiece surface. This can be achieved, for example, via the drive. This means that the first clamping jaw and/or the second clamping jaw are placed on the workpiece surface in such a way that the defined clamping force is exerted on the workpiece to be welded and that the workpiece to be welded is held with the defined clamping force. The level of the defined clamping force results, for example, from the workpiece to be welded, in particular its material properties, and/or from the desired clamping results. For example, the defined clamping force can have a size that produces an elastic deformation of the workpiece surface in the clamped state. Alternatively or additionally, if two workpieces are welded in a lap joint, the clamping force can have a size that produces a zero gap in the clamped state, as generally described above, between the workpieces arranged in the lap joint. The required clamping force can be achieved by actuating the drive accordingly.

Preferably, a light sensor element is arranged in the second vacuum chamber, or a light sensor element is assigned to the second vacuum chamber. When using two vacuum chambers, i.e. an upper and a lower vacuum chamber, the light sensor element acts as a quality assurance. In particular, it can be used to detect and record the welding throughput.

The laser welding gun preferably has a housing for the laser beam between the optical coupling element and the first vacuum chamber. The vacuum region of the laser welding gun then preferably begins in the beam direction of the laser beam below or behind the optical coupling element. The vacuum is shielded from the atmosphere by the optical coupling element, the housing and the first clamping jaw with the first vacuum chamber. The housing is preferably designed as a membrane bellows or as a bellows. If the first, upper clamping jaw is movable, in particular linearly movable, the first vacuum chamber must also be movable in a corresponding manner. For safety reasons, however, the laser beam that is coupled in via the optical coupling element must be enclosed. When the first vacuum chamber is moved, the distance to the optical coupling element also changes. In order to ensure that the laser beam is shielded, the housing is preferably a membrane bellows, which is, for example, a bellows that takes on the function of a housing around the laser beam. A bellows is in particular a volume body, for example a ring-shaped cylinder or a multiple ck, for example quadrangular, in particular rectangular or square volume body, which has a wave-shaped, changing internal cross-section, for example diameter. A bellows can thus carry out movements in the axial direction by being pulled apart and compressed "accordion-like". The bellows is preferably made of metal, for example stainless steel. If the workpieces to be welded are firmly clamped in the laser welding gun, the membrane bellows or bellows can still be moved, for example if a device for generating and/or deflecting the laser beam is moved in the manner described above, in particular linearly. The housing can serve in particular as laser protection. The housing shields the laser beam, including reflected radiation, and thus protects people in the vicinity of the laser welding gun. There is therefore no need to house the entire welding device or the entire welding gun. In addition, circuit breakers with a performance level can also be connected to the welding gun, so that opacity and thus laser safety can be guaranteed in every case.

In a further embodiment, the laser welding gun preferably has a protective device for generating at least one protective gas jet, which is provided behind the optical coupling element in the beam direction of the laser beam to protect the optical coupling element. The protective gas jet enters via a protective gas inlet below the optical coupling element, for example into a housing beginning below the optical coupling element, flows past the optical coupling element, for example through the housing, and exits via a protective gas outlet, for example from the housing. The protective gas jet preferably flows parallel to the optical coupling element so that it does not become dirty. A sensor element that interacts with the optical coupling element and is designed to monitor and report a dirty optical coupling element can then, for example, also provide feedback to the protective device so that the protective gas jet can be adjusted if necessary.

Contaminants that arise during the welding process, such as vapors, splashes, and the like, can settle on the optical coupling element, such as a protective glass, and negatively affect the incoming laser radiation, for example partially absorbing it. This can have a negative impact on the welding process. To prevent this, the protective device described is used. If the sensor element detects, for example, that the optical coupling element is too dirty, it can be replaced if necessary. If the optical coupling element is located in a laser head described above, for example, this can have a corresponding holder, such as a drawer, for exchangeably holding the optical coupling element.

The protective gas jet creates a kind of curtain that prevents harmful process emissions from reaching the optical coupling element and settling on it. Process emissions that enter the protective gas jet are discharged via the protective gas outlet. The extraction can be arranged opposite the protective gas inlet to enable the gas flow to be as uniform as possible.

The laser welding gun can preferably have a gas flow device which is provided for flowing gas into the welding zone. This serves to keep the workpiece clean. It also helps to avoid process emissions and deposits on and next to the weld seam.

A method for laser welding workpieces in a vacuum is described below, which is carried out using a laser welding gun according to the invention. To avoid repetition, reference is made here to the explanations of the laser welding gun according to the invention for the sequence of the method and its functionality.

1. a) Ein erzeugter Laserstrahl wird über ein optisches Einkoppelelement in der ersten Vakuumkammer positioniert, wobei der Laserstrahl über eine Austrittsöffnung in einer ersten Spannbacke der Laserschweißzange in die erste Vakuumkammer eintritt und auf wenigstens einem zu schweißenden Werkstück in der Schweißzone positioniert wird;
2. b) Die erste Vakuumkammer wird auf das in der Schweißzone befindliche Werkstück aufgesetzt, wobei sich die Schweißzone innerhalb der ersten Vakuumkammer befindet, beziehungsweise die Schweißzone von der ersten Vakuumkammer begrenzt ist;
3. c) In der ersten Vakuumkammer wird um die Schweißzone herum ein begrenztes lokales Vakuum erzeugt;
4. d) Nach Evakuierung der ersten Vakuumkammer erfolgt der Laserschweißprozess in der ersten Vakuumkammer.

The procedure is characterized by the following steps:

1. a) A generated laser beam is positioned in the first vacuum chamber via an optical coupling element, wherein the laser beam enters the first vacuum chamber via an exit opening in a first clamping jaw of the laser welding gun and is positioned on at least one workpiece to be welded in the welding zone;
2. b) The first vacuum chamber is placed on the workpiece located in the welding zone, whereby the welding zone is located within the first vacuum chamber or the welding zone is delimited by the first vacuum chamber;
3. c) In the first vacuum chamber, a limited local vacuum is created around the welding zone;
4. d) After evacuation of the first vacuum chamber, the laser welding process takes place in the first vacuum chamber.

The sequence of the individual procedural steps is not fixed to the above-mentioned order.

The process is used to weld workpieces, for example sheets of metal to be welded, particularly in lap joints.

In principle, it is sufficient if only the first clamping jaw is provided with the first vacuum chamber. However, if a second clamping jaw with a second vacuum chamber is also used, the first clamping jaw with the first vacuum chamber is particularly movable, while the second clamping jaw with the second vacuum chamber is preferably fixed. The vacuum chambers are part of the clamping jaws, or correspond to the clamping jaws by means of which the workpiece to be processed is held and fixed during the welding process. The first, upper vacuum chamber is movable and can be moved up and down so that the workpieces to be welded can be clamped between the vacuum chambers.

When the laser welding gun is in operation, for example, a laser head, which is described in connection with the laser welding gun, is moved, in particular linearly, via a drive. The laser beam runs from the laser head into the optical coupling element and passes through it in the direction of the workpiece surface to be processed. The laser beam enters the first, upper vacuum chamber. If the upper clamping jaw is movable, i.e. linearly movable, the first vacuum chamber must also be movable in a corresponding manner. For safety reasons, however, the laser beam is preferably enclosed. In this way, the first upper vacuum chamber is preferably connected to the optical coupling element, and in particular to the laser head. In order to ensure the mobility of the first vacuum chamber, a membrane bellows, which is for example a bellows, is provided between the optical coupling element, for example the laser head, and the first, upper vacuum chamber, which takes on the function of a housing around the laser beam.

Preferably, the first vacuum chamber is open in the direction of the welding zone, the first vacuum chamber being delimited by a vacuum chamber wall, in particular by a circumferential web, and when the first vacuum chamber is placed on the workpiece to be processed, the first vacuum chamber is sealed against the atmosphere, in particular an elastic impression of the vacuum chamber wall, in particular the web, is created in the workpiece, which enables the vacuum to be generated. In this case, the first clamping jaw or the first vacuum chamber, which is open downwards, i.e. in the direction of the workpiece surface, is provided with or delimited by the vacuum chamber wall, in particular the circumferential web. As a result, when the vacuum chamber wall, in particular the web, hits the workpiece, an elastic impression is created in the workpiece, which enables the vacuum to be generated, since it shields the welding point, which is located within the vacuum chamber wall, in particular the web, from atmospheric pressure. A further effect of this impression is that the workpiece is elastically deformed at this point, whereby the required zero gap can be achieved. The same applies in an analogous manner to the second vacuum chamber. In this regard, reference is also made to the corresponding explanations regarding laser welding guns above.

In a further embodiment, a sealing device, in particular in the form of a sealing ring, can be provided outside the vacuum chamber wall, in particular the surrounding web, of the first vacuum chamber, or therein, whereby when the first vacuum chamber is placed on the workpiece to be processed, the sealing device first touches the workpiece and develops its sealing effect, and then the vacuum chamber wall, in particular the web, is placed on the workpiece to be processed, preferably without deforming the workpiece. This is an embodiment in which a workpiece deformation that occurs in the previously described embodiment is counteracted. For this purpose, the sealing device, for example in the form of a sealing ring, is provided outside the vacuum chamber wall, in particular the surrounding web, or therein. To fix the sealing ring, it is inserted in a groove, preferably wedge-shaped or dovetail-shaped or of another design. The required zero gap is again achieved via the vacuum chamber wall, in particular the web, which is located inside the sealing ring. When the clamping jaw is operated, the sealing ring first touches the workpiece and is pressed together. This creates a vacuum seal. As it is moved further together, the vacuum chamber wall, in particular the web, hits the workpiece surface and presses the workpiece parts together, which allows the zero gap to be created. However, since the vacuum chamber wall no longer has to be used to shield against atmospheric pressure, it can be made wider in this design. which creates a larger contact surface and prevents permanent deformation of the workpiece. The same applies analogously to the second vacuum chamber. In this regard, reference is also made to the corresponding statements in connection with the laser welding gun according to the invention.

To clamp the workpieces, the first clamping jaw and/or the second clamping jaw are preferably placed on the workpiece surface with a defined clamping force, in particular via the first vacuum chamber and/or the second vacuum chamber, preferably via the respective contact surface. This means that the first clamping jaw and/or the second clamping jaw are placed on the workpiece surface in such a way that the defined clamping force is exerted on the workpiece to be welded and that the workpiece to be welded is held with the defined clamping force. For example, the first clamping jaw and/or the second clamping jaw can be placed on the workpiece surface with a defined clamping force, in particular via the first vacuum chamber and/or the second vacuum chamber, preferably via the respective contact surface, which produces an elastic deformation of the workpiece in the clamped state. This means that when placed on the workpiece surface, an elastic deformation of the workpiece occurs. Alternatively or additionally, when two workpieces are welded in a lap joint, the first clamping jaw and/or the second clamping jaw can be placed on the workpiece surface with a defined clamping force, in particular via the first vacuum chamber and/or the second vacuum chamber, preferably via the respective contact surface, which in the clamped state creates a zero gap, as generally described above, between the workpieces arranged in the lap joint. This means that when placed on the workpiece surface, the two workpieces are pressed together so that there is a zero gap between them.

Preferably, the weld seam is created in a continuous movement of the laser beam within the vacuum chamber in the welding zone, with the laser beam being defocused at the end of the weld seam. This can be achieved, for example, by a displacement, in particular a linear displacement, of the scanning device, as described above in connection with the laser welding gun. In this way, end crater cracks in particular can be avoided. Usually a so-called end crater is formed at the end of the weld seam. This is a phenomenon familiar to those skilled in the art and therefore does not need to be described in detail here. In the end crater, there is often a strong undercurvature of the weld seam, which results in high three-dimensional stresses that lead to heating cracks in the solidifying molten pool. If the laser beam is defocused at the end of the weld seam, this leads to a temporally decreasing laser power being absorbed by the workpiece. This leads to slower solidification in the end crater. Surprisingly, it has now been discovered that if the laser beam is defocused at the end of the weld, i.e. the focus point is enlarged and the solidification rate of the melt volume is slowed down, a crack-free end crater can be achieved during laser welding in a vacuum.

• 1 eine schematische Prinzipskizze einer erfindungsgemäßen Laserschweißzange;
• 2 bis 5 verschiedene Darstellungen eines Ausführungsbeispiels einer erfindungsgemäßen Laserschweißzange;
• 6 und 7 ein erstes Ausführungsbeispiel einer erfindungsgemäßen Vakuumkammer;
• 8 und 9 ein zweites Ausführungsbeispiel einer erfindungsgemäßen Vakuumkammer;
• 10 in schematischer Darstellung einen Schweißvorgang im Überlappstoß unter Verwendung der erfindungsgemäßen Laserschweißzange; und
• 11 und 12 zwei schematische Darstellungen zur Erläuterung des Nullspalts.

The invention is described in greater detail below using embodiments with reference to the accompanying drawings.

• 1 a schematic diagram of a laser welding gun according to the invention;
• 2 to 5 various representations of an embodiment of a laser welding gun according to the invention;
• 6 and 7 a first embodiment of a vacuum chamber according to the invention;
• 8th and 9 a second embodiment of a vacuum chamber according to the invention;
• 10 in schematic representation a welding process in the lap joint using the laser welding gun according to the invention; and
• 11 and 12 two schematic representations to explain the zero gap.

Each figure shows a laser welding gun 10 which is used for laser welding of workpieces in a vacuum.

Based on 1 First, the basic structure and the basic functionality of such a laser welding gun 10 are explained.

The laser welding gun 10 firstly has a support device 11 which extends along a longitudinal axis 12 and on which the components of the laser welding gun 10 are arranged. The laser welding gun can be arranged on a manipulator, for example on a robot arm, via the support device 11.

An optical coupling element 13 is arranged on the support device 11, by means of which a laser beam 16 is coupled into the laser welding gun 10. The beam direction of the laser beam 16 is shown by the arrow 16a. The optical The coupling element 13 can be a protective glass, for example. The laser beam is generated in a device 14 for generating the laser beam and is deflected in the desired manner by a device 15 for deflecting the laser beam, which is a laser scanner, a 1D optic or the like. The devices 14 and 15 can be part of the laser welding gun 10, and in this case are arranged on the support device 11, for example by means of a suitable laser head 32 (see 2 to 5 ).

A first support arm 17 is arranged on the support device 11 and is linearly movable along the longitudinal axis 12, which is done by means of a suitable drive 24, for example by means of an electric drive. At the end of the first support arm 17 there is a first clamping jaw 18, which is designed in the form of a first vacuum chamber 19. The first vacuum chamber 19 is located in the beam direction 16a of the laser beam 16 above the welding zone 23 in which the actual welding process takes place.

The laser beam 16 enters the first vacuum chamber 19 via an outlet opening of the first clamping jaw 18, whereby the safest vacuum chamber is located in the beam direction 16a of the laser beam 16 on the outlet side of the outlet opening ( 6 to 10 ).

Below the welding zone 23 there is a second clamping jaw 21, which is designed in the form of a second vacuum chamber 22 and which is firmly, i.e. immovably, connected to the support device 11 via a second support arm 20. The second support arm 20 could also be designed to be movable.

The two vacuum chambers 19, 22 are designed to generate a local limited vacuum, which is particularly important in connection with the 6 to 9 as explained below.

The workpieces to be welded, for example two sheets of metal to be welded on top of each other, are introduced into the welding zone 23. The welding process, for example the creation of a weld seam in the lap joint, takes place within the laser welding gun 10. According to the present invention, the clamping jaws 18, 21 simultaneously fulfill the function of the vacuum chambers 19, 22. In principle, it is sufficient if only one such clamping jaw 18 with vacuum chamber function is present. The clamping jaws 18, 21 are an essential component of the laser welding gun 10. This is because they are used to press the workpiece or workpieces to be welded together. This is a very important requirement because during the vacuum laser welding process there must be a zero gap between the workpieces to be welded.

In the 2 to 5 Various representations of a preferred embodiment of a laser welding gun 10 according to the invention are shown. 2 shows a perspective view, 3 shows a view from the side, 4 shows a view from the front and 5 shows an exploded view.

The laser welding gun 10 has a support device 11 on which the individual components of the laser welding gun 10 are arranged. This is initially a device 14, shown only schematically, for generating the laser beam 16 and a device 15 for deflecting the laser beam 16 in the form of a scanner device. Both devices 14, 15 are connected to the support device 11 via a laser head 32. In the laser head 32 there is a holder 33 for receiving the optical coupling device in the form of a protective glass (see 1 ). On the support device 11 there is a first support arm 17, at the end of which there is the first clamping jaw 18, which in turn has or forms or accommodates the first vacuum chamber 19. The first support arm 17 can be moved linearly via a drive 24, so that the first vacuum chamber 19 can execute the direction of movement indicated by the arrow 35. The second clamping jaw 21, which has, forms or accommodates the second vacuum chamber 22, is fixed, i.e. immovably, on the support device 11 via a second support arm 20. Between the laser head 32 and the first vacuum chamber 19 there is a housing 34 in the form of a membrane bellows or bellows, by means of which the laser beam 16 is shielded.

The first vacuum chamber 19 forms an upper vacuum chamber, while the second vacuum chamber 22 forms a lower vacuum chamber. Between the two vacuum chambers 19, 22 is the welding zone 23, in which the actual welding process takes place. The welding zone 23 is located within the vacuum chambers 19, 22, i.e. it is surrounded by the vacuum chambers 19, 22, i.e. by corresponding circumferential webs 27 (see in particular the 6 to 9 ) limited.

To generate the vacuum within the vacuum chambers 19, 22, these are connected to corresponding evacuation devices 30. In addition, a gas flow device 31 is provided, which is provided for flowing gas into the welding zone 23. On the one hand, this serves to keep the workpiece clean. On the other hand, it can prevent process emissions and deposits on and next to the weld seam.

The laser beam 16 generated by the device 14, which is deflected in the desired manner by the deflection device 15, enters the first vacuum chamber 19 adjoining the housing via the optical coupling element in the laser head 32 and the housing 34 and is positioned in this for welding on the workpiece located in the welding zone 23. In principle, one-sided accessibility by placing the first, upper clamping jaw 18, or the first vacuum chamber 19, on the workpiece to be welded is sufficient for the invention. A second clamping jaw 21, or a second vacuum chamber 22, can be omitted here. The required sealing is then carried out in particular by pressing the first, upper vacuum chamber 18 on one side and welding it in, instead of welding it through, for example into the lower workpiece, when two workpieces lying on top of one another, for example two sheets of metal, are welded together. In the case of a full-through welding, the second, lower clamping jaw 21 is particularly provided with the second, lower vacuum chamber 22.

Preferably, the deflection device 15 is movable, in particular linearly movable, for example in the direction of movement marked with 35, on the support device 11, for example on the laser head 32. This allows the focus distance of the generated laser beam 16 to be varied. In particular, the laser beam 16 striking the workpiece can be defocused. This allows end craters of a weld seam to be optimized and in particular end crater crack formation to be reduced.

In the 6 and 7 Two different representations of a vacuum chamber according to the invention are shown. This is explained using a first vacuum chamber 19, whereby a second vacuum chamber 22 can be designed in the same way.

The first vacuum chamber 19 is part of the first clamping jaw 18. The first clamping jaw 18 has an exit opening 26 in the form of an exit slot which is formed in a base plate 25 of the clamping jaw 18. The laser beam enters the first vacuum chamber 19 in beam direction 16a via the exit opening 26. The first vacuum chamber 19 is located in beam direction 16a of the laser beam behind the exit opening 26 in the first clamping jaw 18. In this respect, it provides in particular an extension of the exit opening 26. The first vacuum chamber 19 is open in the direction of the welding zone 23, wherein the first vacuum chamber 19 is delimited by a circumferential web 27, via which a seal of the first vacuum chamber 19 against the atmosphere is created when the first vacuum chamber 19 is placed on the workpiece to be processed. The circumferential web 27 delimits the first vacuum chamber 19, whereby the circumferential web 27 surrounds the outlet opening 26 and thus also the welding zone 23. At the free end, the web 27 has a contact surface 27a, via which the first vacuum chamber 19 comes into contact with the workpiece to be welded. If the vacuum chamber 19 is placed on the workpiece to be welded via the web 27, the vacuum is generated locally only in the immediate area of the welding process in the welding zone 23, i.e. in the area within the circumferential web 27. In particular, an elastic impression of the web 27 is generated in the workpiece, which enables the vacuum to be generated, since it shields the welding zone 23, which is located within the web 27, from atmospheric pressure. A further effect of this impression is that the workpiece deforms elastically at this point, whereby a required zero gap can be realized, as explained in detail in connection with the general description above.

In 10 an embodiment is shown of how two workpieces 36, 37 in the form of metal sheets are welded in an overlap joint using such a laser welding gun 10. The two workpieces 36, 37 are placed on top of one another. The two clamping jaws 19 and 21 clamp the workpieces 36, 37, with the first vacuum chamber 19 of the first clamping jaw 18 or its circumferential web 27 and the second vacuum chamber 22 of the second clamping jaw 21 or its circumferential web 27 pressing against the workpieces 36 from above and below. The welding zone 23 lies within the outlet openings 26. The workpieces 36, 37 and thus the workpiece surfaces 36a, 37a are pressed together via the clamping jaws 18, 21 or the vacuum chambers 19, 22 in such a way that an elastic deformation of the workpieces 36, 37 occurs. In this way, a zero gap 38 is created between the workpieces 36, 37. Air, especially drafts, can no longer penetrate between the workpieces 36, 37 to be welded, which could then press the molten material into the vacuum chamber 19, 22 due to the pressure difference.

The 8th and 9 The embodiment shown corresponds in basic structure to that shown in the 6 and 7 shown embodiment, but is supplemented by further components. Here, a sealing device 28, in particular in the form of a sealing ring, is provided in the circumferential web 27 of the first vacuum chamber 18, in particular in the contact surface 27a, whereby when the first vacuum chamber 18 is placed on the workpiece to be processed, the sealing device 28 first touches the workpiece and develops its sealing effect, and whereby the web 27 is then the workpiece to be machined, preferably without deforming the workpiece. This is a design in which the deformation of the workpiece that occurs in the previously described design is counteracted. To fix the sealing device 28, it is inserted in a preferably wedge-shaped or dovetail-shaped groove 29. Since the web 27 no longer has to be used to shield from atmospheric pressure, the web 27 can be made wider in this design, which creates a larger contact surface and prevents permanent deformation of the workpiece.

In the 11 and 12 The zero gap topic is explained using two principle sketches.

11 shows a preferred situation in which a zero gap 38 is realized between the workpieces 36, 37. Two workpieces 36 and 37 are welded in an overlap joint. The workpieces 36, 37 are pressed together by the first vacuum chamber 19 and the second vacuum chamber 22, in particular with elastic deformation of the workpiece surfaces 36a, 37a, so that a zero gap 38 is realized between the workpiece surfaces 36a, 37a and the weld seam 40 can be produced without any problems in the welding zone 23.

In 12 a situation is shown in which there is a gap 39 between the workpieces 36, 37, so that the vacuum chambers 19, 22 are not sealed and have a leak. In this case, air, in particular drafts, can penetrate into the gap 39 between the workpieces 36, 37 to be welded, which then presses the molten material in the weld seam 40 into the vacuum chambers 19, 22 due to the pressure difference. This makes the welding result unusable, even if the gap 39 is only a few micrometers in size.

How to 11 and 12 As can be seen, the clamping technology according to the invention, with which a zero gap 38 is realized, has a decisive influence on the quality of the welding result, since gaps 39 between the workpieces 36, 37 are avoided.

List of reference symbols

10

Laser welding gun

11

Support device

12

Longitudinal axis

13

Optical coupling element

14

Device for generating a laser beam

15

Device for deflecting a laser beam

16

laser beam

16a

Beam direction of the laser beam

17

First support arm

18

First clamping jaw

19

First vacuum chamber

20

Second support arm

21

Second clamping jaw

22

Second vacuum chamber

23

Welding zone

24

drive

25

Base plate

26

Outlet opening

27

web

27a

Contact surface

28

Sealing device

29

Groove

30

Evacuation facility

31

Gas flow device

32

Laser head

33

Mounting for coupling device

34

Enclosure

35

Direction of movement of the first vacuum chamber

36

workpiece

36a

Workpiece surface

37

workpiece

37a

Workpiece surface

38

Zero gap

39

gap

40

Weld

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2149421 B1 [0010]
• WO 2014/063153 A1 [0011]
• US5170028 [0012]
• DE 102019102233 A1 [0013]

Claims (17)

Laser welding gun (10) for producing a weld seam for connecting workpieces (36, 37), in particular in an overlap joint, comprising a support device (11) which extends along a longitudinal axis (12), an optical coupling element (13) which is provided for coupling a laser beam (16) onto a welding zone (23) in the laser welding gun (10) and which is arranged or formed on the support device (11), a first clamping jaw (18) in the form of a holding element which is provided for holding the workpieces (36, 37) during the welding process, which is arranged or formed in front of the welding zone (23) in the beam direction (16a) of the laser beam (16), wherein the first clamping jaw (18) is arranged or formed on the support device (11) so as to be axially displaceable along the support device (11), in particular via a first support arm (17), or wherein the first clamping jaw (18) is a component of the support device (11), which is axially is displaceable, and a drive (24) which is provided for displacing the first clamping jaw (18) or the first support arm (17) or the support device (11) between a starting position and a welding position, or an interface to a drive (24) which is provided for displacing the first clamping jaw (18) or the first support arm (17) or the support device (11) between a starting position and a welding position, characterized in that the laser welding gun (10) is provided for laser welding workpieces in a vacuum, that the first clamping jaw (18) is designed as a first vacuum chamber (19), or that the first clamping jaw (18) has a first vacuum chamber (19), that the first vacuum chamber (19) is optically coupled to the optical coupling element (15), that an exit opening (26) for the laser beam (16) is formed in the first clamping jaw (18), and that the first vacuum chamber (19) in the beam direction (16a) of the laser beam (16) is arranged or formed around the exit opening (26) on the exit side of the exit opening (26), wherein the first vacuum chamber (19) is configured to enclose the welding zone (23) in the welding position and to generate a limited local vacuum around the welding zone (23). Laser welding gun according to Claim 1 , characterized in that it has a second clamping jaw (21) for holding the workpieces (36, 37) during the welding process, wherein the second clamping jaw (21) is arranged or formed behind the welding zone (23) in the beam direction (16a) of the laser beam (16), that the second clamping jaw (21) is arranged or formed axially displaceable along the support device (11) or fixedly on the support device (11), in particular via a second support arm (20), that the welding zone (23) is formed between the first (18) and second (21) clamping jaw, and that the second clamping jaw (21) is formed as a second vacuum chamber (22), or that the second clamping jaw (21) has a second vacuum chamber (22). Laser welding gun according to Claim 2 , characterized in that an exit opening (26) for the laser beam (16) is formed in the second clamping jaw (21) and that the second vacuum chamber (21) is arranged or formed around the exit opening (26). Laser welding gun according to one of the Claims 1 until 3 , characterized in that a force measuring device is assigned to the first clamping jaw (18) and/or the second clamping jaw (21), that the force measuring device is arranged or formed in particular on or in the first support arm (17) and/or the second support arm (20), and that the force measuring device is provided such that it is able to monitor the forces applied to the workpieces (36, 37) to be welded during the welding process. Laser welding gun according to one of the Claims 1 until 4 , characterized by a device (14) for generating a laser beam (16) which is arranged on the support device (11), or that the laser welding gun (10) has an interface to a device (14) for generating a laser beam, and that at least individual components of the device (14) for generating a laser beam (16) are optionally, preferably linearly, displaceable. Laser welding gun according to one of the Claims 1 until 5 , characterized by a device (15) for deflecting a generated laser beam (16), which is arranged on the support device (11), or that the laser welding gun (10) has an interface to a device for deflecting a generated laser beam (16), and that the device (15) for deflecting the generated laser beam (16) is optionally, preferably linearly, displaceable. Laser welding gun according to one of the Claims 1 until 6 , characterized in that the first vacuum chamber (19) and/or the second vacuum chamber (22) have a contact surface (27a) for the workpieces (36, 37). Laser welding gun according to one of the Claims 1 until 7 , characterized in that the first vacuum chamber (19) is open in the direction of the welding zone (23), and that the first vacuum chamber (19) is delimited by a circumferential web (27) which projects in the direction of the welding zone (23), and/or that the second vacuum chamber (22) is open in the direction of the welding zone (23), and that the second vacuum chamber (22) is delimited by a circumferential web (27) which projects in the direction of the welding zone (23). Laser welding gun according to Claim 8 , characterized in that a sealing device (28), in particular in the form of a sealing ring, is provided outside the circumferential web (27) or in the web (27), and that optionally a groove (29) for receiving the sealing device (28) is provided for fixing the sealing device (28). Laser welding gun according to one of the Claims 1 until 9 , characterized in that the first vacuum chamber (19) and/or the second vacuum chamber (22) is/are connected to an evacuation device (30) to generate a negative pressure. Laser welding gun according to one of the Claims 1 until 10 , characterized in that the first clamping jaw (18) and/or the second clamping jaw (21), in particular via the first vacuum chamber (19) and/or the second vacuum chamber (22), preferably via the respective contact surface (27a), are provided for exerting a defined clamping force on the workpiece surface (36a, 37a), and that the defined clamping force has a magnitude which, in the clamped state, produces an elastic deformation of the workpiece surface (36a, 37a), and/or, when two workpieces (36, 37) are welded in an overlap joint, that the clamping force has a magnitude which, in the clamped state, produces a zero gap (38) between the workpieces (36, 37) arranged in the lap joint. Laser welding gun according to one of the Claims 2 until 11 , characterized in that a light sensor element is arranged in the second vacuum chamber (22), or that a light sensor element is assigned to the second vacuum chamber (22). Laser welding gun according to one of the Claims 1 until 12 , characterized in that it has a housing (34) for the laser beam (16) between the optical coupling element (13) and the first vacuum chamber (19). Laser welding gun according to Claim 13 , characterized in that the housing (34) is provided as laser protection which shields the laser beam and reflected beams. Laser welding gun according to Claim 13 or 14 , characterized in that the housing (24) is designed as a membrane bellows or as a bellows. Laser welding gun according to one of the Claims 1 until 15 , characterized in that it has a protective device for generating at least one protective gas jet, which is provided behind the optical coupling element (13) in the beam direction of the laser beam (16) to protect the optical coupling element (13). Laser welding gun according to one of the Claims 1 until 16 , characterized by a gas flow device (31) which is provided for flowing gas into the welding zone (23).

Images