Apparatus for ultrasonic welding of workpieces and method of operating such an apparatus - Patents.com

Abstract

The invention relates to an apparatus for ultrasonic welding of workpieces (100), comprising a machine stand (20), a welding unit (50) with a sonotrode (55), a setting slide (30) connected to the machine stand (20), carrying the welding unit (50) and which can be moved relative to the machine stand (20) in a feed direction (Z) between a rear position and a front position, a processing slide (40) connected to the welding unit (50) and to the setting slide (30) is provided, which can be moved together with the welding unit (50) in the feed direction (Z) relative to the setting slide (30) between a start position and an end position, and a processing slide drive is provided by means of which the processing slide (40) can be moved relative to the setting slide in the feed direction (Z). In order to improve cycle times and welding accuracy, the present invention provides that a setting slide drive is provided, by means of which the setting slide (30) can be moved relative to the machine stand (20) in the feed direction (Z).

Description

[Technical field]

[0001] The invention relates to an apparatus for ultrasonic welding of workpieces, comprising a machine stand, a welding unit with a sonotrode, a setting slide connected to the machine stand, carrying the welding unit and which can be moved relative to the machine stand in a feed direction (Z) between a rear position and a front position, a processing slide connected to the welding unit and the setting slide is provided, which can be moved together with the welding unit in the feed direction (Z) relative to the setting slide between a start position and an end position, and a processing slide drive is provided, by means of which the processing slide can be moved in the feed direction relative to the setting slide. [Background technology]

[0002] An apparatus for ultrasonic welding is known from US Pat. No. 5,399,633.

[0003] In addition to the sonotrode, the welding unit comprises a converter and, if necessary, an amplitude transformer, to which the converter is either connected directly or, if present, via the amplitude transformer.

[0004] The converter converts the electrical AC voltage into mechanical vibrations. The individual elements of the welding unit are coordinated with one another in such a way that the welding unit has a resonant frequency, a so-called natural frequency, at the desired ultrasonic frequency. Thus, if the converter is provided with a suitable AC voltage, the welding unit vibrates at its natural frequency.

[0005] Furthermore, an anvil may be provided, which is arranged opposite the sonotrode. For machining the workpiece, the workpiece is arranged in the space between the sonotrode and the anvil. During machining, the sonotrode vibrates at ultrasonic frequencies and is pressed against the workpiece in the direction of the anvil, and the workpiece is ultrasonically welded between the sonotrode on the one hand and the anvil on the other hand.

[0006] For this purpose it is necessary that the sonotrode and the anvil can be moved relative to each other. For example, the spacing between the sonotrode and the anvil must be enlarged so that the workpiece can be inserted into the spacing. This spacing is then reduced during processing. The welding unit is therefore attached to a setting slide, which can be moved relative to the anvil so that the welding unit together with the setting slide can be moved in the direction of the force, i.e. towards or away from the anvil.

[0007] Frequently, no anvil is used. The workpiece to be processed is placed in a receptacle, whereby the sonotrode is sometimes pressed against a specific area of ​​the workpiece. To remove the welded workpiece from the receptacle, it is also necessary to move the sonotrode away from the workpiece. Afterwards, the sonotrode must be moved again in the opposite direction for the next weld process.

[0008] To achieve an optimum processing result, it is advantageous if the sonotrode is pressed against the workpiece with a predetermined deposition force.

[0009] In US Pat. No. 5,399,433 a device is proposed which comprises a force sensor for measuring the force being applied to a workpiece by a sonotrode.

[0010] The sonotrode is usually closely adapted to the workpiece to be welded. Different sonotrodes are therefore required for different workpieces. Some devices for ultrasonic welding are interchangeable. For these devices, the sonotrode or the entire welding unit can be exchanged. To ensure this interchangeability, the welding unit usually must be able to move long distances. This interchangeability increases the range of application of the device, but this advantage is often obtained at the expense of the cycle time, which is longer for an interchangeable device than for a device designed for a single application (one type of workpiece and one type of sonotrode).

[0011] Thus, devices are already known which allow the welding units to be manually repositioned for each replacement operation.

[0012] 1a-1c show such a prior art apparatus in three positions. The apparatus 10 for ultrasonic welding of workpieces 100 comprises a machine stand 20, a setting slide 30, a working slide 40 and a welding unit 50. The apparatus 10 further comprises a control unit (not shown).

[0013] The machine stand 20 carries a setting slide 30. The setting slide 30 is movable relative to the machine stand 20 in the direction of the feed direction Z between a rear position and a front position. The rear position and the front position represent the extreme positions of the setting slide 30. The rear position is that which is assumed by the setting slide when it is located in its uppermost position in the figure, and the front position is that which is assumed by the setting slide 30 when it is located in its lowermost position in the figure.

[0014] The setting slide 30 is connected to the machine stand 20 via linear guides (not shown), which ensure that the setting slide 30 can only be moved in the feed direction Z.

[0015] The setting slide 30 is only adjusted during the set-up operation, for example to completely or partially change the welding unit 50 or to adapt the welding process to be performed on different workpieces having different geometries or different distances to the sonotrode.

[0016] The setting slide 30 is manually adjusted during the set-up operation. Once the setting slide 30 is in its desired position, it is manually fixed relative to the machine stand 20. Typically, a clamping device (not shown) is provided for this purpose. The desired position is typically between a front position and a rear position.

[0017] This is the basic position for the actual welding process and is shown in Figure 1a.

[0018] The working slide 40 is mounted on the setting slide 30, which in turn carries the welding unit 50, such that the movement of the setting slide 30 relative to the machine stand 20 during the setting process described above causes both the welding unit 50 and the working slide 40 to be moved relative to the machine stand 20.

[0019] The working slide 40 has a working slide drive, by means of which the working slide can be moved back and forth between a start position and an end position. The start and end positions represent the extreme positions of the working slide 30. The start position is that which is assumed by the working slide 40 when it is located in its uppermost position in the figure, and the end position is that which is assumed by the working slide 40 when it is located in its lowermost position in the figure.

[0020] With the aid of the working slide drive, the welding unit 50 is first brought into the position shown in Fig. 1b during the actual machining process, in which the welding unit 50 comes into contact with the workpiece 100. As a rule, in this position, the speed at which the welding unit 50 is moved towards the workpiece 100 is reduced and the actual welding process is carried out until it reaches the end position shown in Fig. 1c. The working slide 40 is now moved back to the position shown in Fig. 1a, the workpiece 100 is replaced by the next workpiece 100 to be machined and the machining process described above is started again. During this time, the position of the setting slide 30 is not changed. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] European Patent Application Publication No. 2105280 Summary of the Invention [Problem to be solved by the invention]

[0022] Therefore, based on the prior art, it is an object of the present invention to improve cycle time and weld accuracy. [Means for solving the problem]

[0023] This object is achieved by an apparatus for ultrasonic welding of workpieces as described at the beginning, which has a setting slide drive, by means of which the setting slide can be moved relative to the machine stand in the feed direction.

[0024] The device has two slide drives, both of which enable the movement of the welding unit in the feed direction, and which can be moved automatically and independently of each other.

[0025] As a result, the movements of the welding units can be much better adapted to the respective application: depending on the welding unit used or depending on the type of workpiece, the slides can be moved so that the cycle time on the one hand and the welding result on the other hand are optimized.

[0026] The sonotrode and / or the welding unit are preferably removably connected to the processing slide, in this way the sonotrode is exchangeable.

[0027] The welding unit is preferably equipped with a converter and / or an amplitude transformer.

[0028] In some instances, for example with workpieces requiring deep immersion, the slides can be moved together by two slide drives, allowing high movement speeds of the sonotrode in the feed direction. In this way, the cycle times for this type of component can be kept very short.

[0029] The slide drives are preferably each equipped with a drive unit which can preferably be activated independently of one another so that the two drives can be controlled or regulated separately.

[0030] The slide drive may comprise further components or assemblies, for example a gear box or parts thereof.

[0031] The device preferably comprises a control unit. The slide drives, in particular the drive unit, are preferably connected to this control unit and can be controlled by it. In this way, this control unit allows a central control of the slide drives. In this way, the movements of the slides can be precisely coordinated with respect to one another.

[0032] In an advantageous embodiment, an anvil is provided and the welding unit can be moved in the feed direction towards or away from the anvil with the aid of a setting slide and / or a working slide. The workpiece is placed between the anvil and the sonotrode during the welding process. The workpiece can be a continuously conveyed workpiece and can be, for example, a material web or a piece good, for example a plastic housing. The workpiece can also include several parts that are welded together. The anvil is preferably adapted to the tool to be welded or can be adapted to different workpieces by means of adapters. The anvil and / or the adapter can be configured as a workpiece receptacle into which the workpiece can be placed.

[0033] The machine stand and / or the setting slide and / or the processing slide preferably have linear guides, which only allow a relative movement between the setting slide and the machine stand or between the processing slide and the setting slide in the feed direction. This ensures that the slides only move in the feed direction. A common linear guide can be provided for both slides, which simplifies the superstructure of the device. Alternatively, each transport part can have its own linear guide. In this example, the linear guide can be precisely adapted to the respective transport part, which in particular increases the precision of the movement.

[0034] In an advantageous embodiment, the setting slide drive and / or the working slide drive comprise an electric drive unit and / or a pneumatic drive unit and / or a hydraulic drive unit. It is particularly advantageous if the drive units of the two slide drives are of the same type, e.g. both are electric drive units. In this way, only a single type of power source, e.g. a power connection or a compressor, needs to be provided. However, in some embodiments the drive units are of different types. This has the advantage that the drive units can be precisely adapted to the slide and its movements. For example, if the setting slide only performs rough and fast positioning and the working slide performs very precise, i.e. small tolerance movements, then one type of drive unit can be used for the setting slide, e.g. an electric drive unit, and another type of drive unit can be used for the working slide, e.g. a pneumatic drive unit.

[0035] In an advantageous embodiment, a first displacement sensor is provided for detecting the relative position between the machine stand and the processing slide and / or a second displacement sensor is provided for detecting the relative position between the welding unit and the anvil or between the welding unit and the workpiece, the workpiece being arranged between the welding unit and the anvil. In this way, the movement of the slide and / or the welding unit can be detected precisely and compared to a set value, for example for controlling the movement. The displacement sensor is therefore preferably connected to a control unit and adapted to transmit the measured values ​​to the control unit. The control unit is preferably configured to receive the measured values ​​from the displacement sensor and adapted to compare them with the set values, and further preferably also adapted to control the drive unit depending on the measured values ​​and / or the comparison between the measured values ​​and the set values.

[0036] For the welding process, contact between the sonotrode and the workpiece is necessary. In principle, the sonotrode continues to be pressed against the workpiece after contact between the sonotrode and the workpiece has been made by moving the sonotrode in the feed direction. The sonotrode can be activated, i.e. set in a vibrating state, both before and after contact.

[0037] In an advantageous embodiment, a force sensor is provided for determining the welding force, with which the sonotrode is pressed against a workpiece arranged between the sonotrode and the anvil. The force sensor is preferably connected to a control unit and is configured to transmit measured values ​​to the control unit. The control unit is preferably configured to receive the measured values ​​from the force sensor and to compare them with set values, and is also preferably configured to control the drive unit depending on the measured values ​​and / or the comparison between the measured values ​​and the set values. The detection of the welding force can in particular be used to start and / or end the welding process. When a certain set value is reached, the control unit switches off the drive unit or controls it in such a way that the sonotrode moves away from the workpiece. This releases the workpiece and allows it to be removed from the anvil.

[0038] As already mentioned, welding forces are applied during the welding process, which also puts a load on the drive unit. This can lead to faster / greater wear of the drive unit. In an advantageous embodiment, it is provided that the setting slide and / or the working slide have a clamping device, which can be switched or moved back and forth between a clamped and an unclamped state, in which in the clamped state a movement of the setting slide relative to the machine stand or of the working slide relative to the setting slide is prevented, and in the unclamped state a movement of the setting slide relative to the machine stand or of the working slide relative to the setting slide is not prevented. The clamping device reduces the load on the respective drive unit, which allows the drive unit to function with a weaker drive shaft. It is therefore particularly preferred that the load on the setting slide drive is reduced by the clamping device, and that only the working slide causes a movement of the welding unit during the welding process. The welding force is then introduced into the machine stand by the clamping device, and the drive unit of the setting slide drive is bypassed. In a preferred embodiment, the clamping device can be activated and deactivated with the aid of a control device, so that manual intervention to activate the control device is not necessary.

[0039] Several movement profiles for the setting slide drive and / or the working slide drive are preferably stored in a control unit connected to the setting slide drive and / or the working slide drive. The movement profiles preferably comprise set values ​​for the displacement sensor and / or the force sensor and / or control values ​​for controlling the slide drive, whereby the values ​​can be stored together with time designation information. In particular, the movement profiles are adapted for different workpieces and / or sonotrodes. In these embodiments, the sonotrodes are preferably interchangeable. For example, one movement profile may provide that the setting slide drive is switched off when the first displacement sensor transmits a pre-determined measured value to the control unit. In another movement profile, for example, it may be specified that the setting slide drive is first activated only for a pre-determined time. Each movement profile preferably comprises several such steps. Each movement profile represents a complete work process, including a movement of the sonotrode towards the workpiece, a welding process and a movement of the sonotrode away from the workpiece.

[0040] The control unit is preferably configured such that it can recognize the type of sonotrode. A movement profile can then be selected based on the detected sonotrode. The sonotrode or the welding unit can be detected, for example, using RFID (radio-frequency identification). In this case, the control unit is preferably connected to an RFID reader and each sonotrode or welding unit or its support or each workpiece receptacle or workpiece has an RFID transponder.

[0041] Alternatively, the type of sonotrode and / or the type of workpiece and / or the type of workpiece receptacle may be transmitted by a user to the control unit, in which case the control unit is configured to select a movement profile depending on the detected sonotrode.

[0042] The welding force influences the result of the welding process. Both too weak and too strong welding forces can result in welding failure. It is therefore desirable to set the welding force optimally. In an advantageous embodiment, it is therefore provided that a spring device is provided between the machine stand and the welding unit, which is arranged and configured such that the welding unit can be moved relative to the machine stand in the feed direction between the feed position and the welding position. The spring device can be preloaded. Preferably, the spring device is configured to press the welding unit in the direction of the welding position and preferably exerts a force on the welding unit in the direction of the welding position. This welding force can be pre-set by the design of the spring device, in particular in relation to its spring characteristic curve and the range of preload, in particular in relation to the range of deflection. In particular, the welding force is understood to be the force with which the sonotrode is pressed against the workpiece. The spring device can also be realised by a gas pressure spring. In a preferred embodiment, a control and / or regulating device is provided, by means of which the pressure of the gas pressure spring can be adjusted and / or regulated.

[0043] The apparatus is preferably a manually operable device (manual workstation). For this purpose, the apparatus preferably has a human machine interface (HMI) with at least one, preferably two buttons for starting the welding process. The HMI may also be a touch display. The HMI is preferably configured such that the user can use it to transmit the type of sonotrode and / or the type of workpiece to the control unit. The HMI is preferably connected to the control unit.

[0044] The apparatus preferably includes a workpiece receptacle.

[0045] The feed direction preferably runs in the direction of gravity.

[0046] The present invention also provides a method of operating an apparatus for ultrasonic welding of workpieces according to the above, comprising the steps of: (A) positioning a workpiece at a position spaced apart from the sonotrode in a feed direction; (B) moving the setting slide in a direction toward the front position to an initial position; (C) moving the working slide in the direction of the end position to a predetermined weld end position.

[0047] Steps (A), (B) and (C) are preferably performed in that order, alternatively the working slide may be moved first and then the setting slide.

[0048] Preferably, during step (C) the sonotrode is induced to vibrate ultrasonically. The sonotrode may also be induced to vibrate ultrasonically before the start of step (C) and / or after the end of step (C).

[0049] Preferably, the setting slide and / or the working slide are moved in a subsequent step (D) such that the sonotrode is removed from the workpiece, after which the workpiece can be removed. Preferably, both slides are moved such that the workpiece is quickly released.

[0050] In step (B), the initial position is preferably selected such that the sonotrode is directly in front of or in contact with the workpiece in the initial position. In this way, only the working slide performs the actual welding movement. In such a case, the working slide drive can be a very precise drive compared to the setting slide drive, which allows a very precise welding.

[0051] In a preferred embodiment, in step (B), the initial position is selected such that the setting slide is moved a little further towards the front position after contact with the workpiece. If the processing slide is spring-loaded, it is moved towards the start position by the force exerted by the workpiece on the sonotrode. As soon as a pre-determined welding start position, for example determined by the welding force exerted by the spring, is reached, the actual welding process can be started immediately in the subsequent step (C). It is therefore particularly preferred that the welding force is recorded in step (B) and the initial position is determined as the position at which the pre-determined welding force is reached.

[0052] In a further preferred embodiment, an apparatus as claimed in claim 9 is used, in which during or before step (B) the working slide is moved to its end position, in which the setting slide is moved in the direction of the front position until the working slide contacts the workpiece, and the setting slide is pushed by the workpiece in the direction of the rear position against the spring force of the spring device, and the spring force reaches the predetermined welding force, in this way the initial position is determined by the predetermined welding force. [Brief description of the drawings]

[0053] The invention is illustrated and explained below with reference to the drawings.

[0054] [Figure 1] Figures 1a-1c show the prior art device in three positions. [Diagram 2] Figures 2a to 2d show the device according to the invention in four positions according to a first embodiment of the method according to the invention. [Diagram 3] Figures 3a to 3d show the device according to the invention in four positions according to a second embodiment of the method according to the invention. [Figure 4] 4a to 4e show the device according to the invention in five positions according to a third embodiment of the method according to the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0055] The device shown in FIGS. 1a-1c and the welding method shown therein are already known from the prior art and have already been described above.

[0056] Figures 2a to 2d show an embodiment of the device according to the invention, in which the same reference numbers are used as in Figures 1a to 1c.

[0057] The essential difference is that according to the invention the setting slide 30 has a setting slide drive (not shown), by means of which the setting slide 30 can be moved relative to the machine stand 20 during operation. The device 10 according to the invention can be used, for example, to realize the embodiment of the method according to the invention shown in figures 2a to 2d.

[0058] Figure 2a shows the basic position where the machining process of the workpiece 100 is started. In a first step, the setting slide 30 is moved by means of a control unit (not shown) towards its front position, i.e. towards the bottom of the figure, a distance X1, to reach the working position shown in Figure 2b.

[0059] In this position, the clamping device is activated with the aid of the control unit, which prevents further relative movement between the machine stand 20 and the setting slide 30 and relieves the load on the setting slide drive.

[0060] In the next step, the processing slide 40 is used to move the welding unit or sonotrode a distance X2 in the direction of the end position, up to the position shown in FIG. 2c where the sonotrode 55 is in contact with the workpiece 100.

[0061] It may be the case that during the movement over the distance X2 the welding unit is already subjected to ultrasonic vibrations, so that the sonotrode 55 is already vibrating, although it is also possible to activate the ultrasonic vibrations only when the position shown in figure 2c is reached.

[0062] The working slide 40 is now moved further towards its end position for machining the workpiece 100. As soon as the machining is completed, both the working slide 40 and the setting slide 30 are moved back to their starting positions shown in Fig. 2a. This can be done in the reverse order, i.e. first the working slide 40 is moved back and then the setting slide 30 is moved back, or simultaneously. The simultaneous movement of both the working slide 40 and the setting slide 30 allows for a shorter cycle time.

[0063] Figures 3a-3d show a second embodiment of the method according to the invention with the device according to the invention. Figure 3a shows a basic position identical to that shown in figure 2a. In a first step, the setting slide 30 is moved a distance X1 and at the same time the working slide is moved a distance X2 until the sonotrode 55 touches the workpiece 100, thus reaching the position shown in figure 3b. The method shown in figures 3a-3d differs from the method shown in figures 2a-2d in that the movement of both the setting slide 30 and the working slide 40 towards the workpiece is not performed sequentially but simultaneously, which allows to reduce cycle times.

[0064] In this embodiment, there are two options for applying ultrasonic vibrations to the workpiece: in a first variant, the setting slide 30 is stopped in the position shown in Fig. 3b and, if necessary, automatically fixed by means of a locking device. The actual machining is then carried out by moving only the machining slide in the direction of the end position until the position shown in Fig. 3c is reached.

[0065] Alternatively, in a second variant, the actual machining, i.e. the movement of the sonotrode towards the workpiece while it is in contact with the workpiece whilst being exposed to ultrasound, can be caused both by a movement of the setting slide 30 and by a movement of the machining slide 40. This possibility is shown diagrammatically in Fig. 3d.

[0066] After completion of the welding process, both the supply slide 30 and the working slide 40 are returned to the home position shown in Figure 3a.

[0067] 4a to 4e show a third embodiment of the method according to the invention.

[0068] In FIG. 4a the same basic position is again shown as was shown in FIGS. 2a and 3a.

[0069] In a first step, the sonotrode 55 is moved with the aid of the processing slide 40 in the direction of the workpiece 100. This is particularly preferred if the processing slide is moved up to its end position, for example up to a provided end stop. This position is shown in FIG. 4b.

[0070] In the next step, the setting slide 30 is used to move the welding unit 50 together with the working slide towards the front position of the setting slide 30 until the sonotrode contacts the workpiece. This situation is shown in figure 4c.

[0071] However, the movement of the setting slide 30 does not end in this position. Instead, the setting slide 30 is moved further in the direction of the workpiece 100. As the sonotrode is already in contact with the workpiece, the workpiece 100 exerts a force on the sonotrode 55. In the illustrated embodiment, the working slide 40 is spring-loaded. This can be, for example, a gas pressure spring. The force exerted by the workpiece 100 on the sonotrode 55 and thus on the working slide 40 pushes the working slide 40 in the direction of the starting position. In other words, the setting slide 30 moves a certain distance in the direction of the workpiece 100, while the welding unit 50 only moves a slightly shorter distance in the direction of the workpiece 100. Such a spring-loaded load allows the desired welding pressure to be applied to the workpiece.

[0072] In this position, i.e. when the desired welding force has been reached, the movement of the setting slide 30 is stopped and, if necessary, fixed relative to the machine stand with the aid of a clamping device, and further processing is carried out, i.e. the movement of the processing slide 40 towards the workpiece is carried out via the drive of the processing slide 40.

[0073] The described apparatus and methods allow for rapid and reliable conversion of equipment to achieve deep welds with short cycle times. [Explanation of symbols]

[0074] 10 equipment 20 Machine Stand 30 Setting Slide 40 Processing Slide 50 Welding unit 55 Sonotrode 60 Anvil / Workpiece Receptacle 100 work pieces Z supply direction

Claims

1. An apparatus (10) for ultrasonic welding of a workpiece (100), said apparatus comprising: A machine stand (20); a welding unit (50) having a sonotrode (55); a setting slide (30) connected to the machine stand (20), carrying the welding unit (50) and capable of being moved relative to the machine stand (20) in a feed direction (Z) between a rear position and a front position, 1. An apparatus (10) comprising a processing slide (40) connected to the welding unit (50) and to the setting slide (30), the processing slide (40) together with the welding unit (50) being capable of being moved relative to the setting slide (30) in the feed direction (Z) between a start position and an end position, and a processing slide drive is provided by means of which the processing slide (40) can be moved in the feed direction (Z) relative to the setting slide, characterized in that a setting slide drive is provided by means of which the setting slide (30) can be moved in the feed direction (Z) relative to the machine stand (20).

2. 2. The device (10) according to claim 1, characterized in that an anvil (60) is provided and that the welding unit (50) can be moved in the feed direction (Z) towards or away from the anvil (60) with the aid of the setting slide (30) and / or the working slide (40).

3. 3. The device (10) according to claim 1, characterized in that the machine stand (20) and / or the setting slide (30) and / or the working slide (40) have linear guides, which only allow a relative movement between the setting slide (30) and the machine stand (20) or between the working slide (40) and the setting slide (30) in the feed direction (Z).

4. 4. Apparatus (10) according to one of the preceding claims, characterized in that the setting slide drive and / or the working slide drive comprise an electric drive unit and / or a pneumatic drive unit and / or a hydraulic drive unit.

5. 5. The device (10) according to claim 1, characterized in that a first displacement sensor is provided for detecting the relative position between the machine stand (20) and the working slide (40) and / or a second displacement sensor is provided for detecting the relative position between the welding unit (50) and the anvil (60) or between the welding unit (50) and a workpiece (100), the workpiece (100) being arranged between the welding unit (50) and the anvil (60).

6. 6. The apparatus (10) according to claim 1, characterized in that a force sensor is provided for determining the welding force, with which the sonotrode (55) is pressed against a workpiece (100) arranged between the sonotrode (55) and the anvil (60).

7. 7. The apparatus (10) according to claim 1, characterized in that the setting slide (30) and / or the working slide (40) have a clamping device which can be switched or moved back and forth between a clamped state and an unclamped state, and in which in the clamped state a relative movement of the setting slide (30) to the machine stand (20) or a relative movement of the working slide (40) to the setting slide (30) is prevented, and in which in the unclamped state a relative movement of the setting slide (30) to the machine stand (20) or a relative movement of the working slide (40) to the setting slide (30) is not prevented.

8. The device (10) according to any one of claims 1 to 7, characterized in that the device (10) comprises a control unit, which is connected to the setting slide drive and / or the working slide drive, and in which a plurality of movement profiles for the setting slide (30) and / or the working slide (40) are stored.

9. 9. The apparatus (10) according to claim 1, characterized in that a spring device is provided between the machine stand (20) and the welding unit (50), the spring device being arranged and configured such that the welding unit (50) can be moved relative to the machine stand (20) in the feed direction (Z) between a feed position and a welding position.

10. A method of operating an apparatus (10) according to any one of claims 1 to 9 for ultrasonic welding of a workpiece (100), comprising the steps of: (A) positioning the workpiece (100) at a position spaced apart from the sonotrode (55) in the feed direction (Z); (B) moving the setting slide (30) in the direction of the front position to an initial position; (C) moving said working slide (40) in the direction of said end position to a predetermined weld end position.

11. 11. The method according to claim 10, characterized in that during step (C), the sonotrode (55) is induced to vibrate ultrasonically.

12. 12. The method according to claim 10 or 11, characterized in that in step (B), the initial position is selected such that the sonotrode (55) contacts the workpiece (100) in the initial position.

13. 13. The method according to claim 10, wherein in step (B) the working slide (40) is additionally moved in the direction of the end position up to a predetermined welding start position.

14. 14. The method according to claim 10, characterized in that in step (B) a welding force is detected and the initial position is determined as the position at which a predetermined welding force is reached.

15. 16. The method according to claim 10, characterized in that an apparatus according to claim 9 is used, that during or before step (B) the working slide is moved to its end position, and that in step (B) the setting slide is moved in the direction of the front position until it contacts the workpiece and the setting slide is pushed by the workpiece in the direction of the rear position against the spring force of the spring device and the spring force reaches a predetermined welding force.

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