Device for measuring welding force and recording electrical welding voltage during a welding process of a resistance welding device

Description

Technical area

[0001] The invention relates to a device for measuring the welding force and for detecting the electrical welding voltage during a welding process of a resistance welding device according to the preamble of the independent claim. State of the art

[0002] Resistance welding systems can be used to weld metal workpieces such as sheet metal, etc. Such resistance welding systems are used in welding robots and are widely employed in the metalworking industry. Typically, a resistance welding system has a welding gun with two electrode arms. At least one of the electrode arms is movable, while the other can be stationary. The welding gun can be opened and closed by moving the movable electrode arm. When the welding gun is open, workpieces are positioned between the electrode arms; when the welding gun is closed, a welding force of several kN is applied to the workpieces. The magnitude of the welding force, the magnitude of the electric welding current, and the magnitude of the electric welding voltage during the welding process are predefined.Typically, the welding process only begins once the workpieces have been subjected to a minimum welding force of 90% of the welding force. During the welding process, the workpieces are then welded using an electric welding current of several tens of kA at an electric welding voltage of several volts.

[0003] To ensure consistently high welding quality, a device measures the welding force applied during the welding process and records the electrical welding voltage present during the welding process. These measurements and recordings are regularly documented. This measurement and recording can also be used to determine the welding gun's maintenance requirements.

[0004] Such a device for measuring the welding force and detecting the electrical welding voltage during the welding process of a resistance welding system is commercially marketed by the applicant as the welding force calibration transmitter type 9831C and is described in the operating instructions 9831C_002.567d-04.11. The device has a handle with two contact sockets. The handle is used by a human operator to hold the device, and the contact sockets are used to center the device between the electrode arms in place of the workpieces.

[0005] The device has a piezoelectric sensor element that generates electrical polarization charges under the influence of the welding force. The number of electrical polarization charges is proportional to the magnitude of the welding force. The welding force is measured via the electrical polarization charges. The device has a charge amplifier unit that amplifies the electrical polarization charges into electrical direct voltages.

[0006] The device has a component that detects the electrical welding voltage present between the electrode arms.

[0007] The document KR20180110731A1 shows a resistance welding device with a welding gun and two electrode arms. A device for measuring the welding force has a lower and an upper contact socket. The device can be placed on one of the two lower electrode arms via the lower contact socket. The device measures the welding force using a force measuring cell.

[0008] The document KR20160065331A1 shows a resistance welding device with a welding gun and two electrode arms. A device for measuring the welding force and detecting the welding voltage can be placed on the electrode arms. For this purpose, the device has two contact sockets, each of which has a conical recess. Each of the contact sockets accommodates one of the electrode arms via its conical recess. The device measures the welding force using strain gauges and detects the welding voltage using a ring-shaped current sensor.

[0009] Now, the metalworking industry is seeking to operate such a device without the physical presence of an operator. For safety reasons, welding robots, in particular, should not work with a human operator without being physically separated by a protective device.

[0010] In this regard, document US2018236591A1 refers to a resistance welding device with a welding gun and two electrode arms. It discloses a device with a force measuring cell for measuring the welding force. The device can be temporarily fixed to the two electrode arms via a cup-shaped holder.

[0011] Furthermore, when the human operator holds the device during the welding force measurement and the recording of the electrical welding voltage during the welding process, vibrations and bending moments are introduced into the device via the handle. These vibrations and bending moments can distort the welding force measurement and the recording of the electrical welding voltage during the welding process. As a workaround, the measurements and recordings are repeated several times to obtain statistical averages, which reduces the influence of vibrations and bending moments on the accuracy of the measurements and recordings. However, repeating the welding force measurement and the recording of the electrical welding voltage several times during the welding process is time-consuming and therefore expensive.

[0012] It is therefore an object of the present invention to provide a device for measuring the welding force and for detecting the electrical welding voltage during a welding process of a resistance welding device, which device can be operated autonomously, without the presence of a human operator, which device enables the welding force and the detection of the electrical welding voltage during the welding process with high accuracy, and which carries out the measurement of the welding force and the detection of the electrical welding voltage during the welding process simply, quickly and inexpensively. Description of the invention

[0013] This problem is solved by the features of the independent claim.

[0014] The invention relates to a device for measuring the welding force and for detecting the electrical welding voltage during a welding process of a resistance welding device, which resistance welding device has a welding tongs with two electrode arms; with two contact sockets for placing the device on the electrode arms; with at least one sensor element for measuring the welding force exerted by the electrode arms during a welding process; and with at least one component for detecting the electrical welding voltage during the welding process; wherein the device has a coupling means, which coupling means, when the device is placed on the electrode arms, mechanically couples the device to the resistance welding device.

[0015] Because the coupling means according to the invention mechanically couples to the resistance welding device, it is no longer necessary for a human operator to hold the device for measuring the welding force and recording the electrical welding voltage during the welding process. Such a mechanical coupling is simple and quick to implement and enables autonomous operation of the device. Eliminating the need for a human operator to hold the device also prevents vibrations and bending moments from being introduced into the device, which increases the accuracy of the welding force measurement and the recording of the electrical welding voltage during the welding process.

[0016] Advantageous embodiments of the invention are claimed in the dependent claims.

[0017] According to the invention, the two electrode arms consist of a lower electrode arm and an upper electrode arm; wherein the two contact sockets consist of a lower contact socket and an upper contact socket; wherein the lower contact socket has a lower conical recess, which lower conical recess, when the device is placed on the electrode arms, receives a foremost tip of the lower electrode arm and centers it with respect to a vertical axis; and wherein, for the mechanical coupling of the device and the resistance welding device, the coupling means exerts a coupling force on the resistance welding device.

[0018] The coupling mechanism exerts a coupling force on the resistance welding device to mechanically couple the fixture and the resistance welding device. Applying a coupling force is quick and easy and allows the fixture to operate autonomously.

[0019] In an advantageous embodiment, the coupling means comprises a coupling body, which coupling body is fastened externally to the lower contact socket; wherein the coupling body has a coupling opening, which coupling opening extends along the vertical axis through the coupling body and communicates with the lower conical recess; wherein, when the device is placed on the electrode arms, the lower electrode arm protrudes through the coupling opening; and wherein the coupling means for mechanically coupling the device and the resistance welding device exerts the coupling force in the coupling opening on the lower electrode arm.

[0020] Thus, the device simply establishes a mechanical coupling with the lower electrode arm, since the latter protrudes through a coupling opening in the coupling means after the device is placed on the electrode arms. The mechanical coupling is also simple and quick to implement and allows the device to operate autonomously.

[0021] In an advantageous embodiment, the coupling means comprises a clamping element, which clamping element radially encloses the coupling opening; wherein the clamping element has a first clamping element end and a second clamping element end, which first and second clamping element ends are spaced apart from one another by a gap; and wherein a reduction in the width of the gap exerts the coupling force on the lower electrode arm.

[0022] It is thus a clamping element with two clamping element ends which are spaced apart from each other by a gap, which exerts the coupling force by reducing the width of the gap, which is simple and quick to carry out and allows the autonomous operation of the device.

[0023] In an advantageous embodiment, the coupling means comprises a clamping means which is arranged on the clamping element; wherein the clamping means comprises a sleeve element and a screw element; wherein the sleeve element is fastened to the first clamping element end and holds the screw element; and wherein the screw element can be screwed into the second clamping element end and reduces the width of the gap by screwing in.

[0024] Such screwing of a screwing means into a second clamping element end to reduce the width of the gap is simple and quick to perform and allows autonomous operation of the device.

[0025] In a further advantageous embodiment, a holding element is arranged in the coupling opening; wherein, when the device is placed on the electrode arms, the lower electrode arm protrudes through the coupling opening and compresses the holding element; and wherein the compressed holding element exerts the coupling force on the lower electrode arm.

[0026] The arrangement of a compressible holding element in the coupling opening, which holding element exerts the coupling force on the lower electrode arm in the compressed state, is simple and quick to carry out and allows the autonomous operation of the device.

[0027] In a further advantageous embodiment, the resistance welding device comprises a carrier; wherein the device, when placed on the electrode arms, is mechanically coupled to the carrier; wherein the coupling means consists of a further fastening means; and wherein the further fastening means exerts the coupling force on the carrier for the mechanical coupling of the device and the resistance welding device.

[0028] Such a mechanical coupling of a coupling means, which only consists of an additional fastening means on a support of the resistance welding device, can also be carried out easily and quickly and allows the autonomous operation of the device.

[0029] According to the invention, the device comprises a lower housing part, an upper housing part and an insulator; wherein the two contact sockets consist of a lower contact socket and an upper contact socket; wherein the lower contact socket is fastened externally to the lower housing part; wherein the upper contact socket is fastened externally to the upper housing part; wherein the insulator electrically insulates the lower housing part from the upper housing part; wherein the lower housing part and the upper housing part are mechanically connected to one another via the insulator; wherein the lower housing part, the upper housing part and the insulator enclose at least one interior space in the connected state; and wherein the sensor element and the component are arranged in the interior space.

[0030] The device has a three-part housing consisting of a lower housing section, an upper housing section, and an insulator, which houses the sensor element and two electrodes in an interior space. Two contact sockets are attached to the outside of the lower and upper housing sections and transmit the welding force to be measured to the sensor element inside. Such a three-part housing can be easily and quickly attached to the electrode arms and allows autonomous operation of the device. The insulator electrically isolates the lower housing section from the upper housing section, preventing the electrical welding current of several tens of kA from flowing through the three-part housing and distorting the welding force measurement by the sensor element, which is what enables accurate welding force measurement.

[0031] In a further advantageous embodiment, the sensor element is arranged in the interior in the main force circuit of the welding force.

[0032] Due to the arrangement of the sensor element in the main force circuit, almost the entire welding force acts on the sensor element, resulting in its high sensitivity. For the purposes of the invention, the term "sensitivity" refers to the ratio of the force values ​​generated by the sensor element under the influence of the welding force to the magnitude of the actual welding force. Such a sensitive sensor element has a low response threshold of less than or equal to 0.02 N for the welding force to be measured, allowing it to measure even low welding forces very accurately.

[0033] In a further advantageous embodiment, the device comprises a first sensor element, a second sensor element, and a third sensor element; wherein the three sensor elements are identical single-component force transducers that measure the same welding force acting along the longitudinal axis; and wherein the three sensor elements generate force values ​​for the measured welding force.

[0034] Compared to multi-component force transducers, single-component force transducers are inexpensive to purchase. Because the fixture features three identical single-component force transducers, the measuring range of the welding force to be measured is tripled compared to a fixture with only one single-component force transducer, which increases the accuracy of the welding force measurement.

[0035] In a further advantageous embodiment, the first sensor element is arranged in a first interior space, the second sensor element is arranged in a second interior space, and the third sensor element is arranged in a third interior space; wherein the three sensor elements lie in a horizontal plane perpendicular to a vertical axis; wherein the three sensor elements are arranged at an equal radial distance from the vertical axis; and wherein the three sensor elements are arranged at an angle of 120° to one another at a uniform distance.

[0036] This symmetrical design of three sensor elements in three interior spaces with respect to the longitudinal axis largely avoids bending moments which act on the device in the horizontal plane on one side and distort the welding force acting along the vertical axis, thus increasing the accuracy of the welding force measurement.

[0037] In a further advantageous embodiment, the component is arranged in a fourth interior space; wherein the component comprises a lower electrode, an upper electrode, and an optocoupler; wherein the lower electrode is fastened to the inside of the housing lower part; wherein the upper electrode is fastened to the inside of the housing upper part; and wherein the optocoupler detects an electrical welding voltage present between the lower electrode and the upper electrode and converts it into measured values.

[0038] The component features two electrodes and an optocoupler to detect the electrical welding voltage present between the lower and upper housing sections during the welding process and convert it into measured values. Such an optocoupler is cost-effective and features galvanically isolated inputs and outputs. This prevents the electrical welding voltage of several volts from entering the three-part housing and distorting the welding force measurement by the sensor element, enabling accurate measurement of the welding force.

[0039] In a further advantageous embodiment, the device has an evaluation unit for evaluating the force values; wherein the evaluation unit is arranged in a fifth interior space; wherein the three interior spaces of the three sensor elements and the interior space of the component communicate with the fifth interior space of the evaluation unit via passages in the lower housing part; wherein the three sensor elements have electrical lines and derive the force values ​​via the electrical lines to the evaluation unit; wherein the optocoupler has at least one electrical line and derives the measured values ​​via the electrical line to the evaluation unit; and wherein the electrical lines of the three sensor elements and the electrical line of the optocoupler are laid in the passages.

[0040] Thus, not only the sensor element and the component, but also the evaluation unit are housed in the three-part housing. This spatially compact arrangement leads to a significant reduction in the weight and size of the device. This allows the device to be coupled mechanically and securely to the welding gun with a comparatively low coupling force, which is quick and easy to perform and allows autonomous operation of the device. Furthermore, the measured welding force is already evaluated in the device, thus avoiding the need for the force values ​​generated by the sensor element for the measured welding force to be transmitted through an environment outside the device to a spatially distant evaluation unit. On the way to the spatially distant evaluation unit, the force values ​​can be distorted by harmful environmental influences, thus increasing the accuracy of the welding force measurement.

[0041] In a further advantageous embodiment, the device comprises an evaluation unit for evaluating the measured welding force; wherein the sensor element comprises piezoelectric material which generates electrical polarization charges under the action of the welding force; wherein the sensor element diverts the electrical polarization charges to the evaluation unit; wherein the evaluation unit comprises a charge amplifier which amplifies the electrical polarization charges into electrical DC voltages; and wherein the evaluation unit has calibration data of the sensor element, with which calibration data the evaluation unit linearizes the electrical DC voltages.

[0042] The piezoelectric material generates force values ​​in the form of electrical polarization charges for the welding force to be measured. The number of electrical polarization charges is proportional to the magnitude of the applied welding force. However, external influences such as fluctuations and changes in ambient temperature can cause measurement errors in the force values. Therefore, the evaluation unit amplifies the electrical polarization charges into DC voltages and linearizes the DC voltages using calibration data from the sensor element. This linearization reduces the measurement errors in the force values. In general, and also in the context of the invention, the term "linearity" refers to the deviation of the force signals generated by the sensor element under the influence of the welding force from the magnitude of the actual welding force. Linearity is specified as a percentage of the full-scale signal (%FS).The device's linearized force signals exhibit a high linearity of less than or equal to 1% FS and thus accurately represent the welding force to be measured. Furthermore, a sensor element made of piezoelectric material exhibits a small measurement uncertainty compared to strain gauges. For the purposes of the present invention, the term "measurement uncertainty" refers to the accuracy of the agreement between consecutive welding force measurements. The measurement uncertainty of the sensor element made of piezoelectric material is less than or equal to 0.01%, which is approximately two orders of magnitude smaller than that of strain gauges.

[0043] In a further advantageous embodiment, the evaluation unit provides the linearized electrical DC voltages as analog force signals and as digital force signals; wherein the evaluation unit provides the measured values ​​as analog measurement signals or digital measurement signals; wherein the device has an electrical feedthrough; wherein the evaluation unit derives the analog force signals and the digital force signals to the electrical feedthrough; wherein the evaluation unit derives the analog measurement signals and the digital measurement signals to the electrical feedthrough; and wherein, at the electrical feedthrough, optionally analog force signals and digital force signals as well as analog measurement signals and digital measurement signals can be tapped from an environment outside the device.

[0044] Thus, analog force signals and digital force signals, as well as analog measurement signals and digital measurement signals, can be tapped at the electrical feedthrough of the device. This simplifies the measurement of the welding force and the recording of the electrical welding voltage during the welding process by the device, as the device can be connected to both an analog and a digital measurement chain already present outside the device. Further evaluation of the force signals and measurement signals takes place in the measurement chain, for example, to monitor the quality of the welding process. Short description of the characters

[0045] In the following, the invention is explained in more detail using exemplary embodiments with reference to the figures. Fig. 1 is a view, partially in section along a transverse plane YZ, of a part of a first embodiment of the device 1 for measuring the welding force and for detecting the electrical welding voltage during the welding process of a resistance welding device 2; Fig. 2 is a view, partially in section along a longitudinal plane XZ, of a part of a second embodiment of the device 1 for measuring the welding force and for detecting the electrical welding voltage during the welding process of a resistance welding device 2; Fig. 3 is a view, partially in section along a transverse plane YZ, of a part of a third embodiment of the device 1 for measuring the welding force and for detecting the electrical welding voltage during the welding process of a resistance welding device 2; Fig. 4 is an exploded view of a part of the first embodiment of the device 1 according to Fig. 1; Fig. 5 a perspective view of a part of the embodiment of the device 1 according to one of the Fig. 1 to 3 ; Fig. 6 a perspective view of the first embodiment of the device 1 according to Fig. 1 ; and Fig. 7 a perspective view of the embodiment of the device 1 according to one of the Fig. 1 or 2 .

[0046] In all figures, the same reference symbols refer to the same objects. Ways to implement the invention

[0047] The Fig. 1 to 7show a device 1 for measuring the welding force and for recording the electrical welding voltage during the welding process of a resistance welding device 2. The device 1 and the resistance welding device 2 are arranged in a rectangular coordinate system with a longitudinal axis X, a transverse axis Y and a vertical axis Z. A horizontal plane XY is spanned by the longitudinal axis X and the transverse axis Y. A longitudinal plane XZ is spanned by the longitudinal axis X and the vertical axis Z. A transverse plane YZ is spanned by the transverse axis Y and the vertical axis Z. In the following, the adjective "lower" is used for an object of the device 1 or the resistance welding device 2, which in the views according to Fig. 1 to 3 is arranged below the horizontal plane XY and the adjective "upper" is used for an object of the device 1 or the resistance welding device 2, which in the views according to Fig. 1 to 3 is arranged above the horizontal plane XY.

[0048] The resistance welding device 2 comprises a welding gun 20 with a lower electrode arm 20.1 and an upper electrode arm 20.2. The lower electrode arm 20.1 can be arranged stationary, while the upper electrode arm 20.2 is arranged movable. The two electrode arms 20.1, 20.2 are made of electrically conductive material such as copper, copper alloys, etc. By moving the upper electrode arm 20.2 along the vertical axis Z, the welding gun 20 can be opened and closed. The movement of the upper electrode arm 20.2 along the vertical axis Z is shown in the views according to Fig. 1 and 2 marked by a double arrow. During a welding process, the electrode arms 20.1, 20.2 exert a welding force along the vertical axis Z, and an electrical welding voltage is applied between the electrode arms 20.1, 20.2.

[0049] When the welding tongs 20 are open, the device 1 can be placed on the electrode arms 20.1, 20.2. For this purpose, the device 1 has a lower contact socket 12 and an upper contact socket 13. The two contact sockets 12, 13 are made of mechanically resistant material such as steel, tool steel, etc. The lower contact socket 12 is cylindrical and has a lower conical recess 12.1. The upper contact socket 13 is also cylindrical and has an upper conical recess 13.1. Preferably, the two conical recesses 12.1, 13.1 have an opening angle of 45° with respect to the vertical axis Z. Each of the two conical recesses 12.1, 13.1 can accommodate a foremost tip of an electrode arm 20.1, 20.2 and center it with respect to the vertical axis Z. Preferably, the device 1 is placed on the electrode arms 20.1, 20.2 by placing the lower contact socket 12 on the lower electrode arm 20.1.The foremost tip of the lower electrode arm 20.1 is centered in the lower conical recess 12.1. When the welding gun 20 is closed, the upper electrode arm 20.2 moves into the upper conical recess 13.1 and is centered.

[0050] The device 1 comprises a lower housing part 10 and an upper housing part 11. The lower housing part 10 and the upper housing part 11 are made of mechanically resistant material such as steel, tool steel, etc. The lower housing part 10 and the upper housing part 11 are cylindrical in some areas.

[0051] The device 1 has a lower fastening means 12.1 and an upper fastening means 13.1. The lower fastening means 12.1 and the upper fastening means 13.1 are made of mechanically resistant material such as steel, tool steel, etc. Preferably, the lower fastening means 12.2 and the upper fastening means 13.2 are screws. The lower contact socket 12 is fastened externally to the housing base 10 via a lower fastening means 12.2. The adjective "external" refers to a side of the housing base 10 facing away from the housing top 11. The lower fastening means 12.2, in the form of a screw, protrudes through an opening in the lower contact socket 12. It rests with a screw head on the outside of the lower contact socket 12. It can be screwed into threads of the housing base 10, forming a screw connection. The screw connection presses the lower contact socket 12 against the housing base 10.The upper contact socket 13 is attached to the outside of the housing upper part 11 via an upper fastening element 13.2. The adjective "outside" refers to a side of the housing upper part 10 facing away from the housing lower part 10. The upper fastening element 13.2, in the form of a screw, protrudes through an opening in the upper contact socket 13. Its screw head rests on the outside of the upper contact socket 13. It can be screwed into threads in the housing upper part 11, forming a screw connection. The screw connection presses the upper contact socket 13 against the housing upper part 11.

[0052] The device 1 has an insulator 16. The insulator 16 is made of an electrically insulating and mechanically rigid material such as ceramic, polyimide, etc. The insulator 16 is arranged between the housing lower part 10 and the housing upper part 11 with respect to the vertical axis Z. The insulator 16 electrically insulates the housing lower part 10 from the housing upper part 11. The housing lower part 10 and the housing upper part 11 are mechanically connected to one another via the insulator 16.

[0053] When connected, the lower housing part 10 and the upper housing part 11 enclose at least one interior space 10.1 - 10.5. The mechanical connection between the lower housing part 10 and the upper housing part 11 is hermetically sealed. The term "hermetically sealed" in the context of the invention means that humidity, liquids, and gases from the environment cannot enter the interior space 10.1 - 10.5. The environment is the three-dimensional space outside the device 1.

[0054] The device 1 comprises at least one sensor element 15.1 - 15.3 and an evaluation unit 18, which are arranged in the interior space 10.1 - 10.5. The lower housing part 10 and the upper housing part 11 thus protect the sensor element 15.1 - 15.3 and the evaluation unit 18 from harmful environmental influences such as contaminants (dust, moisture, etc.) and from electrical and electromagnetic interference in the form of electromagnetic radiation.

[0055] The sensor element 15.1 - 15.3 measures the welding force exerted by the electrode arms 20.1, 20.2 during a welding process. The sensor element 15.1 - 15.3 generates force values ​​for the measured welding force. The sensor element 15.1 - 15.3 is arranged between the lower housing part 10 and the upper housing part 11 with respect to the vertical axis Z and lies in the horizontal plane XY. The sensor element 15.1 - 15.3 has a sensor housing made of mechanically resistant material such as steel, tool steel, etc. The sensor element 15.1 - 15.3 is preferably hollow-cylindrical with two sensor end faces, two sensor outer surfaces, and a central sensor bore. The sensor end faces are parallel to the horizontal plane XY. A bore axis of the central sensor bore is parallel to the vertical axis Z.

[0056] Preferably, the sensor element 15.1 - 15.3 comprises piezoelectric material made of a single crystal such as quartz (SiO 2 ), calcium gallo-germanate (Ca 3 Ga 2 Ge 4 O 14 or CGG), langasite (La 3 Ga 5 SiO 14 or LGS), tourmaline, gallium orthophosphate, etc., and of piezoceramic such as lead zirconate titanate (Pb[Zr x Ti 1-x ]O 3 , 0 ≤ x ≤ 1), etc. Under the action of the welding force to be measured, the piezoelectric material generates force values ​​in the form of piezoelectric charges. The piezoelectric material is oriented such that it has the highest sensitivity for the welding force acting along the vertical axis Z. For the purposes of the invention, sensitivity is a ratio of the number of electrical polarization charges generated by the welding force to the magnitude of the welding force acting on the piezoelectric material. At the highest sensitivity, the piezoelectric material generates the largest number of electrical polarization charges.

[0057] As shown in the perspective views according to Fig. 5 and 6 As shown, the sensor element 15.1 - 15.3 preferably consists of a first sensor element 15.1, a second sensor element 15.2 and a third sensor element 15.3. The first sensor element 15.1 is arranged in a first interior space 10.1. The second sensor element 15.2 is arranged in a second interior space 10.2. The third sensor element 15.3 is arranged in a third interior space 10.3. Preferably, all three sensor elements 15.1 - 15.3 are located in the horizontal plane XY. Preferably, the three sensor elements 15.1 - 15.3 are arranged at the same radial distance R to the vertical axis Z. Preferably, the three sensor elements 15.1 - 15.3 are arranged at an angle of 120° to one another at equal distances. Preferably, a center of mass M of the device 1 lies within the radial distance R. Preferably, a center of mass M of the device 1 lies as shown in the Fig. 1 to 3, 5 and 6 shown, largely on the longitudinal axis X.

[0058] Preferably, the three sensor elements 15.1 - 15.3 are identical and measure the same welding force acting along the longitudinal axis X. Preferably, the sensor element 15.1 - 15.3 is a single-component force transducer, which measures the welding force acting along the vertical axis Z as its sole force component. Such a single-component force transducer is marketed commercially by the applicant as type 9133C and is described in data sheet 9130C_003-418d-04.21. The single-component force transducer has an outer diameter of 16.0 mm defined by the outer sensor surface, a central sensor bore with an inner diameter of 6.1 mm, and a height of 3.5 mm between the sensor faces. The single-component force transducer type 9133C has a sensitivity of 4 pC / N.

[0059] The device 1 has a lower insulation element 15.4 and an upper insulation element 15.5. The lower insulation element 15.4 and the upper insulation element 15.5 are disc-shaped and have a central through-opening. The lower insulation element 15.4 and the upper insulation element 15.5 are made of electrically insulating and mechanically rigid material such as ceramic, polyimide, etc. The lower insulation element 15.4 is arranged between the housing lower part 10 and the sensor element 15.1 - 15.3 with respect to the vertical axis Z. The upper insulation element 15.5 is arranged between the sensor element 15.1 - 15.3 and the housing upper part 11 with respect to the vertical axis Z. The device 1 preferably has exactly one lower insulation element 15.4 and exactly one upper insulation element 15.5 for each sensor element 15.1 - 15.3. The lower insulation element 15.4 and the upper insulation element 15.5 insulate the sensor element 15.1 - 15.3 electrically opposite the lower housing part 10 and the upper housing part 11. Thus, the sensor element 15.1 - 15.3 is not at the potential of the electrical welding voltage of a few V, which can falsify the measurement of the welding force.

[0060] Preferably, the sensor element 15.1 - 15.3 has pick-off electrodes. The pick-off electrodes pick up the electrical polarization charges from the piezoelectric material. The pick-off electrodes are not shown in the figures.

[0061] Preferably, the device 1 comprises at least one biasing element 15.6. To ensure that the tapping electrodes tap all generated electrical polarization charges from the piezoelectric material, and to prevent any electrical polarization charges remaining on the piezoelectric material and thus distorting the welding force measurement, the tapping electrodes are mechanically biased against the piezoelectric material by the biasing element 15.6. The mechanical prestress closes micropores between the tapping electrodes and the piezoelectric material. Preferably, the device 1 comprises precisely one biasing element 15.6 for each sensor element 15.1-15.3. The biasing element 15.6 protrudes through the central through-opening of the lower insulation element 15.4, the central sensor bore of the sensor element 15.1-15.3, the central through-opening of the upper insulation element 15.5, and an opening in the upper housing part 11.Preferably, the preload element 15.6 is a screw whose head rests on the outside of the housing upper part 11 and which can be screwed into threads of the housing lower part 10, forming a screw connection. The screw connection presses the sensor element 15.1 - 15.3 against the housing lower part 10. Here, too, the adjective "outside" refers to a side of the housing upper part 11 facing away from the housing lower part 10.

[0062] Preferably, the sensor element 15.1 - 15.3 is arranged in the interior space 10.1 - 10.5 in the main force distribution of the welding force. For this purpose, the majority of the welding force acts along the vertical axis Z on the sensor element 15.1 - 15.3, and only a small portion of the welding force flows through the insulator 16 and the prestressing element 15.6. For the purposes of the invention, the adjective "largely" means "greater than or equal to 90%."

[0063] The sensor element 15.1-15.3 has at least one electrical line. The electrical line is electrically connected to the evaluation unit 18. The sensor element 15.1-15.3 transmits the measured welding force as force values ​​to the evaluation unit 18 via the electrical line. Preferably, each of the three sensor units 15.1-15.3 has an electrical line.

[0064] The device 1 has at least one component 17.1-17.3. The component 17.1-17.3 is preferably arranged in a fourth interior space 10.4. The component 17.1-17.3 preferably comprises a lower electrode 17.1, an upper electrode 17.2, and an optocoupler 17.3. The lower electrode 17.1 is attached to the inside of the housing bottom part 10. The adjective "inside" in this context refers to a side of the housing top part 10 facing the housing bottom part 10. The upper electrode 17.2 is attached to the inside of the housing top part 11. The adjective "inside" in this context refers to a side of the housing bottom part 10 facing the housing top part 11. The lower electrode 17.1 and the upper electrode 17.2 are electrically connected to the optocoupler 17.3. The optocoupler 17.3 has galvanically isolated inputs and outputs. The two electrodes 17.1, 17.2 detect the voltages between the electrode arms 20.1, 20.2, and the optocoupler 17.3 converts the detected welding voltage into measured values. The measured values ​​at the optocoupler output are galvanically isolated from the welding voltage at the optocoupler input. The measured values ​​are electrical voltages with an amplitude proportional to the magnitude of the welding voltage. The measured values ​​can be digital or analog. The optocoupler 17.3 has at least one electrical line and is connected to the evaluation unit 18 via the electrical line, where it transmits the measured values ​​to the evaluation unit 18.

[0065] The evaluation unit 18 evaluates the force values ​​and the measured values. The evaluation unit 18 is arranged in a fifth interior space 10.5. Preferably, the three interior spaces 10.1-10.3 of the three sensor elements 15.1-15.3 and the fourth interior space 10.4 of the component 17.1-17.3 communicate with the fifth interior space 10.5 of the evaluation unit 18 via passages 10.6 in the housing base 10. The electrical lines of the three sensor elements 15.1-15.3 and the electrical line of the optocoupler 17.3 are routed in the passages 10.6 of the housing base 10.

[0066] The spatially compact arrangement of three sensor elements 15.1 - 15.3, one component 17.1 - 17.3 and an evaluation unit 18 leads to a significant reduction in weight and size of the device 1. Compared with the welding force calibration transmitter type 9831C, the weight of the device 1 is reduced from 1.40 kg to less than half, at 0.64 kg.

[0067] The evaluation unit 18 is an electrical circuit with electrical and electronic components mounted on at least one printed circuit board. To insert the evaluation unit 18 into the fifth interior space 10.5, the lower housing part 10 has a cover plate 10.7. The cover plate 10.7 is made of mechanically resistant material such as steel, tool steel, etc. The cover plate 10.7 is attached to the lower housing part 10. The attachment of the cover plate 10.7 to the lower housing part 10 hermetically seals the fifth interior space 10.5. The attachment of the cover plate 10.7 to the lower housing part 10 is detachable. When the attachment of the cover plate 10.7 to the lower housing part 10 is released, the fifth interior space 10.5 is accessible from outside the device 1 for inserting the evaluation unit 18.

[0068] The evaluation unit 18 is electrically insulated from the lower housing part 10 and the upper housing part 11. Thus, the evaluation unit 18 is not at the potential of the electrical welding voltage of several volts, which can distort the evaluation of the measured welding force and the evaluation of the measured electrical welding voltage.

[0069] The evaluation unit 18 preferably has a charge amplifier unit that amplifies the force values ​​derived from the electrical lines in the form of electrical polarization charges into electrical direct voltages. The electrical direct voltages are analog force signals AKS from the evaluation unit 18. The evaluation unit 18 preferably digitizes the analog force signals AKS into digital force signals DKS. The evaluation unit 18 preferably has calibration data from the sensor element 15.1 - 15.3, which calibration data the evaluation unit 18 uses to linearize the force signals. The evaluation unit 18 can linearize analog force signals AKS or digital force signals DKS. The calibration data is preferably a calibration curve with coefficients of a polynomial function.

[0070] Preferably, the evaluation unit 18 provides measured values ​​of the electrical welding voltage recorded during the welding process as analogue measuring signals AMS or digital measuring signals DMS.

[0071] In the embodiments according to Fig. 3 to 7 The device 1 has an electrical feedthrough 19. The electrical feedthrough 19 is attached to the lower housing part 10. The attachment of the electrical feedthrough 19 to the lower housing part 10 is hermetically sealed. Preferably, the electrical feedthrough 19 is arranged in regions within the fifth interior space 10.5. The electrical feedthrough 19 is electrically connected to the evaluation unit 18. The force signals and the measurement signals from the evaluation unit 18 can be diverted from the fifth interior space 10.5 to the outside of the device 1 via the electrical feedthrough 19.

[0072] Preferably, analog force signals AKS and digital force signals DKS are optionally applied to the electrical feedthrough 19. Preferably, the analog force signals AKS and digital force signals DKS applied to the electrical feedthrough 19 are linearized. Preferably, analog measurement signals AMS and digital measurement signals DMS are optionally applied to the electrical feedthrough 19. Preferably, the electrical feedthrough 19 has four electrical contacts. The analog force signals AKS and the analog measurement signals AMS as well as the digital force signals DKZ and the digital measurement signals DMS are optionally applied to these four contacts. Technical information signals TIS such as a type designation of the device 1, a serial number of the device 1, a website of the manufacturer of the device 1, a calibration date of the sensor element 15.1 - 15.3, a measuring range of the sensor element 15.1 - 15.3, the sensitivity of the sensor element 15.1 - 15.3, the operational readiness of the device 1, etc., can be read from the evaluation unit 18. The technical information signals TIS simplify the measurement of the welding force, as the technical information signals TIS can be read by a nearby measuring chain and simplify the further evaluation of the force signals and measurement signals in the measuring chain. An electrical supply voltage can be fed to the evaluation unit 18 via the electrical feedthrough 19.

[0073] The electrical feedthrough 19 is electrically insulated from the housing base 10 and the housing top 11. Thus, the electrical feedthrough 19 is not at the potential of the electrical welding voltage of several volts, which can distort the derivation of the force signals and the measurement signals.

[0074] Even if the device 1 can autonomously measure the welding force and the electrical welding voltage, the operating status of the device 1 must still be monitored. For this purpose, the device 1 has a display device 10.8. The display device 10.8 is attached to the lower housing part 10. The display device 10.8 is hermetically sealed to the lower housing part 10. The display device 10.8 has at least one light or a screen. On the display device 10.8, technical information signals TIS, such as the operating status of the device 1, etc., can be visually displayed for a human operator outside the device 1. According to Fig. 5 and 7The display device 10.8 has five lights. For the visual representation of the technical information signals TIS, the lights can illuminate in different colors, flash for different lengths of time, etc. The operating status of the device 1 can be "ready for operation," "not ready for operation," etc. The display device 10.8 is clearly visible to the human operator even from a distance of 1 or 2 meters and allows the autonomous operation of the device 1. This allows malfunctions in the operating status of the device 1 to be easily and quickly detected and rectified by the human operator, which in turn minimizes the time required for measuring the welding force and the electrical welding voltage.

[0075] The device 1 has a coupling means 14. In the first embodiment according to Fig. 1 the coupling means 14 is a clamp coupling. In the second embodiment according to Fig. 2the coupling means 14 is a positive coupling. In the third embodiment according to Fig. 3 The coupling element 14 is a force-locking coupling. The coupling element 14 is made of mechanically resistant material such as steel, tool steel, aluminum, thermoplastic, etc.

[0076] In the first embodiment according to Fig. 1The coupling means 14 comprises a coupling body 14.1 and at least one further fastening means 14.4. The coupling body 14.1 is fastened externally to the lower contact socket 12 via the further coupling means 14.4. The adjective "external" refers to a side of the lower contact socket 12 facing away from the housing base 10. Preferably, the further fastening means 14.4 is a screw, which screw protrudes through an opening in the coupling body 14.1, which screw rests with a screw head on the outside of the coupling body 14.1, and which screw can be screwed into threads of the lower contact socket 12, forming a screw connection. The screw connection presses the coupling body 14.1 against the lower contact socket 12.

[0077] In the first embodiment according to Fig. 1The coupling means 14 has a clamping element 14.3. The clamping element 14.3 is formed integrally with the coupling body 14.1. Preferably, the clamping element 14.3 is molded onto the outside of the coupling body 14.1. The adjective "outside" refers to a side of the coupling body 14.1 facing away from the lower contact socket 12. The coupling body 14.1 and the clamping element 14.3 are hollow cylindrical.

[0078] In the first embodiment according to Fig. 1The coupling means 14 has a coupling opening 14.5. The coupling opening 14.5 extends along the vertical axis Z through the coupling body 14.1 and the clamping element 14.3. The coupling opening 14.5 communicates with the conical recess 12.1 of the lower contact socket 12. The device 1 can thus be placed on the electrode arms 20.1, 20.2 by placing the coupling means 14 on the lower electrode arm 20.1 such that the lower electrode arm 20.1 protrudes through the coupling opening 14.5 and the foremost tip of the lower electrode arm 20.1 comes to lie centered in the lower conical recess 12.1 of the lower contact socket 12. The coupling opening 14.5 has a diameter which corresponds to the outer diameter of the lower electrode arm 20.1. The diameter of the coupling opening 14.5 and the outer diameter of the lower electrode arm 20.1 have a small mechanical play of preferably 0.1 mm.

[0079] In the first embodiment according to Fig. 1 The clamping element 14.3 radially encloses the coupling opening 14.5 arranged in the coupling body 14.1. The clamping element 14.3 has a first clamping element end 14.31 and a second clamping element end 14.32. The two clamping element ends 14.31, 14.32 are spaced apart from each other by a gap 14.33. In the perspective view according to Fig. 6 the gap 14.33 has a width of preferably 1 mm along the longitudinal axis X.

[0080] In the first embodiment according to Fig. 1 The coupling means 14 comprises a clamping means 14.2. The clamping means 14.2 is arranged on the clamping element 14.3. The clamping means 14.2 comprises a sleeve element 14.21, a screw element 14.22 and a handle element 14.23. The sleeve element 14.21 is hollow cylindrical with a hollow axis. In the perspective view according to Fig. 6The sleeve element 14.21 extends along the longitudinal axis X. The sleeve element 14.21 is fastened to the first clamping element end 14.31. The screw element 14.22 is arranged in the hollow axis in some areas and is held in the sleeve element 14.21 by positive locking. The screw element 14.22 has a first end and a second end. The grip element 14.23 is attached to the first end of the screw element 14.22. The screw element 14.22 can be rotated about the longitudinal axis X via the grip element 14.23. The rotatability of the screw element 14.22 about the longitudinal axis X is shown in the perspective view according to Fig. 6marked by a curved double arrow. The screw element 14.22 has an external thread at its second end. By rotating it around the longitudinal axis X, the external thread at the second end of the screw element 14.22 can be screwed into threads in the second clamping element end 14.32, forming a screw connection. By rotating the screw element 14.22 in a first direction around the longitudinal axis X, the screw element screws into the second clamping element end 14.32. Since the screw element 14.22 is held in the sleeve element 14.21, and thus also in the first clamping element end 14.31 to which the sleeve element 14.21 is fastened, the width of the gap 14.33 along the longitudinal axis X is reduced by turning. The reduction in the width of the gap 14.33 is more pronounced than the mechanical play between the diameter of the coupling opening 14.5 and the outer diameter of the lower electrode arm 20.1, which means that in the electrode arms 20.1, 20.2, where the lower electrode arm 20.1 protrudes through the coupling opening 14.5, the reduction in the width of the gap 14.33 clamps the lower electrode arm 20.1 in the clamping element 14.3 and exerts a coupling force K on the lower electrode arm 20.1. The coupling means 14 and the lower electrode arm 20.1 are thus coupled by clamping. The coupling force K is sufficient to couple the device 1 to the welding gun 2 in a mechanically stable manner. The term "mechanically stable coupling" means, in the context of the invention, that the device 1 is immovably coupled to the lower electrode arm 20.1 during operation of the resistance welding device 2.

[0081] Also in the second embodiment according to Fig. 2The coupling means 14 has a coupling body 14.1. The coupling body 14.1 is arranged on the outside of the lower contact socket 12. The adjective "outside" refers to a side of the lower contact socket 12 facing away from the housing base 10. The coupling body 14.1 is preferably located in the lower conical recess 12.1 of the lower contact socket 12.

[0082] The coupling body 14.1 of the second embodiment according to Fig. 2is also hollow cylindrical and has a coupling opening 14.5. The coupling opening 14.5 extends along the vertical axis Z through the coupling body 14.1. The coupling opening 14.5 communicates with the conical recess 12.1 of the lower contact socket 12. The coupling opening 14.5 has a diameter which corresponds to the outer diameter of the lower electrode arm 20.1. A holding element 14.51 is arranged in the coupling opening 14.5. The holding element 14.51 is annular and arranged in a groove in the coupling opening 14.5. The holding element 14.51 is made of an elastic material such as rubber, perfluoro rubber, etc. Preferably, two holding elements 14.51 are arranged in the coupling opening 14.5. The holding element 14.51 arranged in the groove projects slightly radially into the coupling opening 14.5. The device 1 can thus be attached to the electrode arms 20.1, 20.2 by placing the coupling means 14 onto the lower electrode arm 20.1 such that the lower electrode arm 20.1 protrudes through the coupling opening 14.5 and the foremost tip of the lower electrode arm 20.1 is centered in the lower conical recess 12.1 of the lower contact socket 12. In doing so, the retaining element 14.51 arranged in the groove is radially compressed by the lower electrode arm 20.1. The coupling means 14 and the lower electrode arm 20.1 are thus coupled by positive engagement. The compressed retaining element 14.51 exerts a coupling force K on the lower electrode arm 20.1.

[0083] In the third embodiment according to Fig. 3The coupling means 14 consists merely of a further fastening means 14.4. The resistance welding device 2 has a carrier 21.1 and a bearing element 21.2. The carrier 21.1 is arranged so close to the two electrode arms 20.1, 20.2 that the device 1, when placed on the two electrode arms 20.1, 20.2, can be mechanically coupled to the carrier 21.1. The bearing element 21.2 is preferably made of an elastic material such as rubber, caoutchouc, etc., and elastically mounts the device 1 on the carrier 21.1. Vibrations are dampened by the bearing element 21.2 and cannot pass from the resistance welding device 2 to the device 1 and distort the measurement of the welding force and the detection of the electrical welding voltage during the welding process. The device 1 is also supported via the bearing element 21.2 is electrically insulated from the electrical potential of the resistance welding device 2, so that fluctuations in the electrical potential of the resistance welding device 2 cannot affect the measurement of the welding force and the detection of the electrical welding voltage during the welding process. Preferably, the additional fastening means 14.4 consists of two screws. The support 21.1 has two through-holes for the two screws. Each screw protrudes through a through-hole in the support 21.1. Each screw head rests on the outside of the support 21.1. Each screw can be screwed into threads of the housing base 10, thus forming a screw connection. The adjective "outside" refers to a side of the support 21.1 facing away from the housing base 10. The screw connection of the additional fastening means 14.4 presses the housing base 10 against the support 21.The coupling means 14 thus mechanically couples the housing lower part 10 and the carrier 21.1 by frictional engagement. List of reference symbols

[0084] 1Device 2Resistance welding device 10Lower housing section 10.1First interior space 10.2Second interior space 10.3Third interior space 10.4Fourth interior space 10.5Fifth interior space 10.6Cable 10.7Cover plate 10.8Indicating device 11Upper housing section 12Lower contact socket 12.1Lower conical recess 12.2Lower fastening means 13Upper contact socket 13.1Upper conical recess 13.2Upper fastening means 14Coupling means 14.1Coupling body 14.2Clamping element 14.21Sleeve element 14.22Screw element 14.23Handle element 14.3Clamping element 14.31First clamping element end 14.32Second clamping element end 14.33Gap 14.4 Additional fastening element 14.5 Coupling opening 14.51 Holding element 15.1 First sensor element 15.2 Second sensor element 15.3 Third sensor element 15.4 Lower insulation element 15.5 Upper insulation element 15.6 Pre-tensioning element 16 Insulator 17.1 Lower electrode 17.2 Upper electrode 17.3 Optocoupler 18 Evaluation unit 19 Electrical feedthrough 20 Welding tongs 20.1 Lower electrode arm 20.2Upper electrode arm 21.1Carrier 21.2Bearing element AKSanalog force signals DKSdigital force signals AMSanalog measurement signals DMSdigital measurement signals KKluting force MCenter of mass Rradial distance TIStechnical information signals XLongitudinal axis XYHorizontal plane XZLongitudinal plane YTransverse axis YZTransverse plane ZVertical axis.

Claims

1. A device (1) for measuring a welding force and for detecting a welding voltage during a welding process of a resistance welding device (2), which resistance welding device (2) comprises a welding gun (20) with two electrode arms (20. 1, 20.2), which two electrode arms (20.1, 20.2) consist of a lower electrode arm (20.1) and an upper electrode arm (20.2); comprising two contact sockets (12, 13) for placing the device (1) at the electrode arms (20.1, 20.2), which two contact sockets (12, 13) consist of a lower contact socket (12) and an upper contact socket (13), which lower contact socket (12) has a lower conical recess (12.1), wherein, when the device (1) is placed at the electrode arms (20.1, 20.2), said lower conical recess (12.1) accommodates a foremost tip of the lower electrode arm (20.1) and centers it with respect to a vertical axis (Z); comprising at least one sensor element (15.1 - 15.3) for measuring the welding force applied by the electrode arms (20.1, 20.2) during a welding process; and comprising at least one component (17.1 - 17.3) for detecting the welding voltage during the welding process; characterized in that the device (1) comprises a coupling means (14), wherein, when the device (1) is placed at the electrode arms (20.1, 20.2), said coupling means (14) mechanically couples the device (1) to the resistance welding device (2); in that, for mechanical coupling of the device (1) and the resistance welding device (2), the coupling means (14) exerts a coupling force (K) onto the resistance welding device (2); in that the device (1) comprises a lower housing part (10), an upper housing part (11) and an insulator (16); in that the lower contact socket (12) is fastened on the outside of the lower housing part (10); in that the upper contact socket (13) is fastened on the outside of the upper housing part (11); in that the insulator (16) electrically insulates the lower housing part (10) from the upper housing part (11); in that the lower housing part (10) and the upper housing part (11) are mechanically connected to each other by the insulator (16); in that the lower housing part (10) and the upper housing part (11), when connected, enclose at least one interior space (10.1 - 10.5); and in that the sensor element (15.1 - 15.3) and the component (17.1 - 17.3) are arranged in said interior space (10.1 - 10.5).

2. The device (1) according to claim 1, characterized in that the coupling means (14) comprises a coupling body (14.1), which coupling body (14.1) is attached to the lower contact socket (12) on the outside thereof; in that the coupling body (14.1) comprises a coupling opening (14.5), which coupling opening (14.5) extends through the coupling body (14.1) along the vertical axis (Z) and communicates with the lower conical recess (12.1); in that, when the device (1) is placed at the electrode arms (20.1, 20.2), the lower electrode arm (20.1) projects through the coupling opening (14.5); and in that, for mechanical coupling of the device (1) and the resistance welding device (2), the coupling means (14) exerts the coupling force (K) in the coupling opening (14.5) onto the lower electrode arm (20.1).

3. The device (1) according to claim 2, characterized in that the coupling means (14) comprises a clamping member (14.3), which clamping member (14.3) surrounds the coupling opening (14.5) in a radial direction; in that the clamping member (14.3) has a first clamping member end (14. 31) and a second clamping member end (14.32), which first and second clamping member ends (14.31, 14.32) are spaced apart from each other by a gap (14.33); and in that a reduction in the width of the gap (14.33) exerts the coupling force (K) onto the lower electrode arm (20.1).

4. The device (1) according to claim 3, characterized in that the coupling means (14) comprises a clamping means (14.2), which clamping means (14.2) is arranged at the clamping member (14.3); in that the clamping means (14.2) comprises a bushing member (14.21) and a screw member (14.22); in that the bushing member (14.21) is fastened to the first clamping member end (14.31) and holds the screw member (14.22); and in that the screw member (14.22) can be screwed into the second clamping member end (14.32) and, by being screwed in, in reduces the width of the gap (14.33).

5. The device (1) according to claim 2, characterized in that a retaining member (14.51) is arranged in the coupling opening (14.5); in that, when the device (1) is placed at the electrode arms (20.1, 20.2), the lower electrode arm (20.1) protrudes through the coupling opening (14.5) and compresses the retaining member (14.51); and in that the compressed retaining member (14.51) exerts the coupling force (K) onto the lower electrode arm (20.1).

6. The device (1) according to claim 1, characterized in that the resistance welding device (2) comprises a support (21.1); in that the device (1), when placed at the electrode arms (20.1, 20.2), can be mechanically coupled to the support (21.1); in that the coupling means (14) consists of a further fastening means (14.4); and in that the further fastening means (14.4) exerts the coupling force (K) onto the support (21.1) for the mechanical coupling of the device (1) and the resistance welding device (2).

7. The device (1) according to any of the claims 1 to 7, characterized in that the sensor element (15.1 - 15.3) is arranged in the interior space (10.1 - 10.5) in the main force path of the welding force.

8. The device (1) according to any of the claims 1 to 7, characterized in that the device (1) comprises a first sensor element (15.1), a second sensor element (15.2) and a third sensor element (15.3); in that the three sensor elements (15.1 - 15.3) are identical single-component force transducers which measure the same welding force acting along the longitudinal axis (X); and in that the three sensor elements (15.1 - 15.3) generate force values for the welding force measured.

9. The device (1) according to claim 8, characterized in that the first sensor element (15.1) is arranged in a first interior space (10.1), the second sensor element (15.2) is arranged in a second interior space (10.2) and the third sensor element (15.3) is arranged in a third interior space (10.3); in that the three sensor elements (15.1 - 15.3) lie in a horizontal plane (XY) perpendicular to a vertical axis (Z); in that the three sensor elements (15.1 - 15.3) are arranged at an equal radial distance (R) from the vertical axis Z; and in that the three sensor elements (15.1 - 15.3) are arranged evenly spaced apart from each other at an angle of 120°.

10. The device (1) according to any of the claims 8 or 9, characterized in that the component (17.1 - 17.3) is arranged in a fourth interior space (10.4); in that the component (17.1 - 17.3) comprises a lower electrode (17.1), an upper electrode 17.2 and an optocoupler (17.3); in that the lower electrode (17.1) is fastened to the lower housing part (10) on the inside thereof; in that the upper electrode (17.2) is fastened to the upper housing part (11) on the inside thereof; and in that the optocoupler (17.3) detects an electrical welding voltage acting between the lower electrode (17.1) and the upper electrode (17.2) and converts it into measured values.

11. The device (1) according to claim 10, characterized in that the device (1) comprises an evaluation unit (18) for evaluating the force values; in that the evaluation unit (18) is arranged in a fifth interior space (10.5); in that the three interior spaces (10.1 - 10.3) of the three sensor elements (15.1 - 15.3) and the interior space (10.4) of the component (17.1 - 17.3) communicate with the fifth interior space (10.5) of the evaluation unit (18) by passages (10.6) in the lower housing part (10); in that the three sensor elements (15.1 - 15.3) have electrical wires and transmit the force values to the evaluation unit (18) by the electrical wires; in that the optocoupler (17.3) has at least one electrical wire and transmits the measured values to the evaluation unit (18) by the electrical wire; and in that the electrical wires of the three sensor elements (15.1 - 15.3) and the electrical wire of the optocoupler (17.3) are guided in the passages (10.6).

12. The device (1) according to any of the claims 10 or 11, characterized in that the device (1) comprises an evaluation unit (18) for evaluating the welding force measured; in that the sensor element (15.1 - 15.3) comprises piezoelectric material that generates electrical polarization charges under the action of the welding force; in that the sensor element (15.1 - 15.3) transmits the electrical polarization charges to the evaluation unit (18); in that the evaluation unit (18) comprises a charge amplifier that amplifies the electrical polarization charges to give direct electrical voltages; and in that the evaluation unit (18) has calibration data of the sensor element (15.1 - 15.3) wherein the evaluation unit (18) uses said calibration data for linearizing the direct electrical voltages.

13. The device (1) according to claim 12, characterized in that the evaluation unit (18) provides the linearized electrical DC voltages as analog force signals (AKS) and as digital force signals (DKS); in that the evaluation unit (18) provides the measured values as analog measurement signals (AMS) or digital measurement signals (DMS); in that the device (1) comprises an electrical feedthrough (19); in that the evaluation unit (18) transmits the analog force signals (AKS) and the digital force signals (DKS) to the electrical feedthrough (19); in that the evaluation unit (18) transmits the analog measurement signals (AMS) and the digital measurement signals (DMS) to the electrical feedthrough (19); and in that analog force signals (AKS) and digital force signals (DKS) as well as analog measurement signals (AMS) and digital measurement signals (DMS) can be picked off from an environment outside of the device (1) at said electrical feedthrough (19).