ULTRASONIC SCANNING UNDER LOAD

Abstract

A method for operating an ultrasonic system (10) under load at startup, comprising scanning the impedance and phase of an ultrasonic stack (14) under operating load; determining, from the scan, the load resonance and the phase at that resonance; and, while contacting a part (24) under load at startup, operating the ultrasonic stack (14) at the determined resonance and phase. Abstract figure: Fig. 1

Description

Title of the invention: ULTRASONIC SCANNING UNDER CHARGE Technical field

[0001] The present disclosure relates to an ultrasonic scan under load. CONTEXT

[0002] This section provides background information related to this disclosure which is not necessarily prior art.

[0003] An ultrasonic power supply that starts with its ultrasonic battery under load has a different starting frequency than when the ultrasonic battery is in air. Often, the operating frequency of the ultrasonic battery in air is known because the battery is designed to have a particular resonance in air. Historically, ultrasonic power supplies were designed to have a default starting frequency for the battery in air. If the power supply tries to start with the battery under load, the frequency shift often leads to overloading the power supply. Historically, many ultrasonic power supplies allowed manual adjustment of the starting frequency, but this is an imprecise and non-automatic method. SUMMARY

[0004] This section provides a general summary of the disclosure and is not an exhaustive disclosure of its full scope or all of its features.

[0005] A method of operating an ultrasonic system under load at startup includes scanning the impedance and phase of an ultrasonic stack under operating load, determining from the scan the resonance under load and the phase at that resonance and, while contacting a part under load at startup, operating the ultrasonic stack at the determined resonance and phase.

[0006] A method for operating an ultrasonic system under load at startup comprises: a sweep of the impedance and phase of an ultrasonic battery under various operating loads; the determination, from the resonance scan under a given load, of the phase at that resonance; and while contacting a part under the load determined at startup, the operation of the ultrasonic battery at the determined resonance and phase.

[0007] According to another aspect, a target phase of a control loop for an ultrasonic device is modified when the load of the ultrasonic system changes.

[0008] According to another aspect, the charge determined at start-up is determined by a charge sensor which detects a charge applied by the ultrasonic battery against the part.

[0009] According to another aspect, as the charge detected by the charge sensor changes during a welding operation, the resonance and phase of the ultrasonic stack are modified according to the charge detected by the charge sensor.

[0010] According to another aspect, an actuator supports the ultrasonic stack and the actuator is controlled by a controller to apply a load to the ultrasonic stack against the part.

[0011] According to another aspect, the operating load determined at start-up is predetermined.

[0012] According to another aspect, the ultrasonic stack includes a converter and a horn.

[0013] According to another aspect, an ultrasonic system includes a power supply Ultrasonic. An ultrasonic battery is connected to the ultrasonic power supply. An actuator is configured to movably support the ultrasonic battery and to press the ultrasonic battery against a workpiece under load. A controller operates the actuator to apply a load to the ultrasonic battery against the workpiece at startup and to operate the ultrasonic power supply at startup according to a stored resonance and phase for the load applied to the workpiece.

[0014] According to another aspect, the controller has a memory which stores scanned resonance and phase data for the ultrasonic system at different operating loads and, at startup of the ultrasonic stack, the controller determines a resonance and phase from the memory for the operation of the ultrasonic power supply according to the corresponding load applied to the part.

[0015] According to another aspect, a load sensor detects a load applied to the part by the ultrasonic battery.

[0016] According to another aspect, the controller receives a load signal from the load sensor and activates the ultrasonic battery at a resonance and phase stored at startup that correspond to the load signal. The resonance and phase can be stored or interpolated values ​​that correspond to the load signal.

[0017] According to another aspect, the load applied to the part is predetermined by the controller.

[0018] According to another aspect, the ultrasonic stack includes a converter and a horn.

[0019] According to another aspect, a method of operating an ultrasonic system under Charge at startup, includes: - a sweep of the amplitude of an ultrasonic battery under various operating loads; - determining an operating load of the ultrasonic system against a part; - the determination, from the sweep, of the amplitude under the determined operating load; and - while contacting a part under the operating load at startup, the operation of the ultrasonic battery at the determined amplitude.

[0020] According to this latter aspect, the process may further comprise one or more of the following features, taken alone or in combination: - the method further includes modifying a target phase of a control loop for an ultrasonic device when the load of the ultrasonic system changes; - the load determined at start-up is determined by a load sensor which detects a load applied by the ultrasonic battery against the part and the amplitude is interpolated from the scans; - as the load detected by the load sensor changes during a welding operation, the resonance and phase of the ultrasonic stack are modified according to the load detected by the load sensor; - an actuator supports the ultrasonic stack and the actuator is controlled by a controller to apply a load to the ultrasonic stack against the workpiece; - the operating load determined at start-up is predetermined; - The ultrasonic battery includes a converter and a horn.

[0021] Other areas of application will become apparent from the description provided herein. The description and specific examples in this summary are given for illustrative purposes only and are not intended to limit the scope of this disclosure. Brief description of the drawings

[0022] The drawings described herein are shown for the sole purpose of illustrating certain selected embodiments and not all possible embodiments, and they are not intended to limit the scope of this disclosure.

[0023] Fig. 1 is a schematic representation of an example of an ultrasonic welding device according to the principles of this disclosure;

[0024] The [Fig.2] is a graph of impedance and phase as a function of frequency with the ultrasonic battery out of contact;

[0025] Figures 3A and 3B are graphs of impedance and phase as a function of frequency with the ultrasonic stack under different contact load levels;

[0026] Figure 4 is a graph of impedance and phase as a function of frequency with the ultrasonic stack under actuation load; and

[0027] Figure 5 shows a graph of the impedance and phase under different actuation loads.

[0028] The corresponding reference numbers indicate the corresponding parts in all views of the drawings. DETAILED DESCRIPTION

[0029] Examples of embodiments will now be described in more detail with reference to the accompanying drawings.

[0030] An ultrasonic system 10 generally comprises an ultrasonic power supply 12, an ultrasonic stack 14, and an actuator 16, as shown in [Fig. 1]. The ultrasonic stack 14 generally comprises an ultrasonic converter 18 that converts the electrical energy from the power supply 12 into ultrasonic motion, an amplifier 20 that provides gain to the ultrasonic motion, and a horn 22 that performs the actual work on the part 24. The actuator 16 moves the ultrasonic stack 14 relative to the part 24 so that the tip 26 of the horn 22 comes into contact with the part 24.

[0031] The stack 14 can contain just a converter 18 and a horn 22, or a converter 18, an amplifier 20, and a horn 22. The stack 14 can be a linear stack, a rotary stack, a composite stack, a cross-horn stack, or any combination thereof. In other words, the stack can be anything powered by a converter. The ultrasonic system can be intended for any type of ultrasonic process such as, but not limited to, welding, riveting, crimping, sonication, cleaning, cutting, etc.

[0032] An ultrasonic battery 14 operates best when it is in series resonance when the impedance is at a minimum, or in parallel resonance when the impedance is at a maximum. When the ultrasonic battery 14 has no load, such as in air, resonance occurs when the phase between the current waveform and the voltage waveform is approximately zero, as shown in [Fig. 2]. When the ultrasonic battery 14 comes into contact with a semi-rigid load / part, however, the resonant frequency shifts, as also shown in [Fig. 3A]. The larger the load, the higher the frequency for both parallel and series resonance, but the overall impedance curve tends to flatten. Moreover, as shown in [Fig. 3B], the phase at each resonance is no longer zero.

[0033] An ultrasonic power supply 12 that starts with its ultrasonic battery 14 under load has a different starting frequency than it does when the ultrasonic battery 14 is in air. Often, the operating frequency in air of the ultrasonic battery 14 is known because the latter is designed to have a A particular resonance occurs in air. Historically, ultrasonic power supplies were designed to have a default starting frequency for battery 14 in air. If power supply 12 attempts to start with battery 14 under load, the frequency mismatch often leads to overloading power supply 12. Historically, many ultrasonic power supplies allowed manual adjustment of the starting frequency, but this is an imprecise and non-automatic method.

[0034] Furthermore, the ideal operating point of the ultrasonic power supply 12 is at the series or parallel resonance of the battery. In air, this corresponds to a phase between the current and voltage that is approximately zero. When the battery 14 is under load, however, the phase corresponding to the series or parallel resonance falls below zero, as shown in [Fig. 3B]. Historically, ultrasonic power supplies 12 have been operated at zero phase or at a fixed negative phase. This is not ideal and can lead to overload.

[0035] The present disclosure solves these two problems by performing an impedance and phase scan while the battery 14 is under full operating load, at increased or reduced power, reading the state of resonance (either series or parallel) and the phase at that resonance, and using this frequency to start the ultrasound at full power and this phase to operate the ultrasound under load. By way of example, with reference to Figures 3A and 3B, by inputting a contact load pressure of the ultrasonic device at startup, the controller 12 can select an impedance and a phase to operate the ultrasonic device at startup.

[0036] Also, under conditions of dynamic variable loading of the stack, for example in a continuous textile line, the variation in loading could cause overloads of the ultrasonic power supply 12 during operation. The present disclosure solves this third problem by taking a family of impedance and phase scans under different loads of the stack 14 at full power, increased power, or reduced power, then operating the stack 14 at full power and reading the force signal 28 from the actuator 16, using the appropriate resonant phase under load and varying the phase according to the changing load.

[0037] The present disclosure measures the phase and impedance under various loads by having the power supply 12 perform a phase and impedance sweep under various loads. The sweep operates the power supply 12 in a frequency sweep and measures the phase and impedance while the actuator 16 applies a load to the workpiece 24. The sweeps can be recorded in a memory 32 of the power supply 12. The series and parallel resonances are calculated by a controller 30 and / or a processor 34 of the power supply 12, and their associated phases are calculated.

[0038] There are two ways to calculate the series and parallel resonances. Referring to [Fig. 4], the first way to find the series resonance is to take the frequency at which the impedance is a minimum. The first way to find the parallel resonance is to take the frequency at which the impedance is a maximum. The first way to find the associated phases is to read the phases at the impedance maxima and minima found. The second way to find the two resonances is to measure the peak phase of the frequency sweep. The two resonances are approximately in phase equal to half the peak phase and the -90-degree phase. The series resonance is at the lower frequency of the phase at this value, and the parallel resonance is at the higher frequency of the phase at this value.The second method has the advantages that only the phase needs to be measured during the scan and it is more accurate since impedance curves tend to be flattened under load, so it can be difficult to find peaks and troughs accurately.

[0039] When the power supply 12 starts up under actuator load, the power supply 12 uses the resonant frequency determined or interpolated from the loaded sweeps. This prevents overloads caused by starting the power supply 12 out of resonance, which would otherwise occur if the power supply 12 used resonance when starting the battery 14 in air. An overload condition exists when the voltage and / or current going to the converter is higher than what is safe for the power supply components. Typically, in a power supply 12, a power supply safety circuit disconnects the power supply 12 to protect the components when this condition occurs.

[0040] During operation of the power supply 12, resonance is maintained by controlling the phase between the current and voltage of the power supply 12. The target phase used for the power supply 12 when the battery is under load is that which is determined or interpolated from the loaded sweeps. This prevents overloads. Prior art used an arbitrary fixed zero phase or negative phase, which in both cases is not an accurate representation of the phase at loaded resonance, and was therefore more likely to cause overloads.

[0041] For applications requiring variable loads during operation, such as in a textile line, scans are performed at various load levels prior to operation. The family of impedance and phase curves is used to interpolate the resonance and phase at any given load. A force signal from the actuator 28 communicates with the controller 30 of the power supply 12 during operation and provides condition information. of variable load. The appropriate interpolation phase is used for the given load at any given time, changing as the load conditions change. This prevents overloads caused by variable load conditions.

[0042] The power supply 12 can operate at parallel or series resonance. If the power supply 12 operates at series resonance, only the series resonance needs to be calculated by the load sweep. If the power supply 12 operates at parallel resonance, only the parallel resonance needs to be calculated.

[0043] This disclosure may be used only for the load start-up frequency, in which case the load phase does not need to be known.

[0044] Impedance (Z) represents the opposition that an ultrasonic welding system offers to the alternating current (AC) flow due to the combined effects of resistance, capacitance, and inductance. During the bonding cycle, as the two surfaces come together and the bond size increases, the impedance changes. It increases as the bond forms. In constant current mode, the output of the ultrasonic generator maintains a constant current. As the impedance changes, the current remains constant, resulting in an increase in voltage (V) to maintain a constant displacement of the tool tip.

[0045] Refer to [Fig. 5], which is a graph of impedance and phase versus frequency showing different amplitudes under various loads. According to the principles of this disclosure, the amplitude can be controlled for start-up operation under various loads. A force signal from the actuator 28 communicates with the controller 30 of the power supply 12 during operation and provides information on the variable load condition. The appropriate amplitude derived from the interpolation is used for the given load at any given time, changing as the load conditions change. This prevents overloads caused by variable load conditions.

[0046] This disclosure may be used only for operation under a constant load, in which case the load starting frequency does not need to be known and only one load phase needs to be known. This disclosure may also be used only for operation under a variable load, in which case the load starting frequency does not need to be known, but the load-dependent phase family must be known. This disclosure may also be used with any combination of the above.

Claims

Demands

1. A method for operating an ultrasonic system (10) under load at startup, comprising: - scanning the impedance and phase of an ultrasonic stack (14) under various operating loads; - determining, from the scanning, the resonance under a determined load and the phase at that resonance; and - while contacting a part (24) under the load determined at startup, operating the ultrasonic stack (14) at the determined resonance and phase, wherein the load determined at startup is determined by a load sensor that detects a load applied by the ultrasonic stack (14) against the part (24) and the impedance and phase are interpolated from the scannings.

2. A method of operating an ultrasonic system (10) under load at start-up according to claim 1, further comprising modifying a target phase of a control loop for an ultrasonic device when the load of the ultrasonic system (10) changes.

3. A method of operating an ultrasonic system (10) under load at start-up according to claim 1, wherein, as the load detected by the load sensor changes during a welding operation, the resonance and phase of the ultrasonic stack (14) are modified according to the load detected by the load sensor.

4. Method of operating an ultrasonic system (10) under load at start-up according to claim 1, wherein an actuator (16) supports the ultrasonic stack (14) and the actuator (16) is controlled by a controller (30) to apply a load to the ultrasonic stack (14) against the part (24).

5. Method of operating an ultrasonic system (10) under load at start-up according to claim 1, wherein the operating load determined at start-up is predetermined.

6. Method of operating an ultrasonic system (10) under load at start-up according to claim 1, wherein the ultrasonic stack (14) comprises a converter (18) and a horn (22).

7. A method for operating an ultrasonic system (10) under load at startup, comprising: - a sweep of the amplitude of an ultrasonic stack (14) under various operating loads; - the determination of an operating load of the ultrasonic system (10) against a part (24); - the determination, from the sweep, of the amplitude under the determined operating load; and - while contacting a part (24) under the operating load at start-up, the operation of the ultrasonic stack (14) at the determined amplitude, in which the load determined at start-up is determined by a load sensor that detects a load applied by the ultrasonic stack (14) against the part (24) and the amplitude is interpolated from the sweeps.

8. A method of operating an ultrasonic system (10) under load according to claim 7, further comprising modifying a target phase of a control loop for an ultrasonic device when the load of the ultrasonic system (10) changes.

9. A method of operating an ultrasonic system (10) under load according to claim 7, wherein, as the load detected by the load sensor changes during a welding operation, the resonance and phase of the ultrasonic stack (14) are modified according to the load detected by the load sensor.

10. Method of operating an ultrasonic system (10) under load according to claim 7, wherein an actuator (16) supports the ultrasonic stack (14) and the actuator (16) is controlled by a controller (30) to apply a load to the ultrasonic stack (14) against the part (24).

11. Method of operating an ultrasonic system (10) under load according to claim 7, wherein the operating load determined at start-up is predetermined.

12. Method of operating an ultrasonic stack system (10) under load according to claim 7, wherein the ultrasonic stack (14) comprises a converter (18) and a horn (22).

13. Ultrasonic system (10), comprising: - an ultrasonic power supply; - an ultrasonic battery (14) connected to the ultrasonic power supply; - an actuator (16) configured to mobilitiously support the ultrasonic stack (14) and configured to press the ultrasonic stack (14) against a part (24) under a load; and - a controller (30) to operate the actuator (16) to apply a load to the ultrasonic stack (14) against a part (24) at start-up and to operate the ultrasonic power supply at start-up according to a stored resonance and phase for the load applied to the part (24).

14. Ultrasonic system (10) according to claim 13, wherein the controller (30) has a memory that stores scanned resonance and phase data for the ultrasonic system (10) at different operating loads and, at startup of the ultrasonic stack (14), the controller (30) determines a resonance and phase from the memory for the operation of the ultrasonic power supply according to the corresponding load applied to the part (24).

15. Ultrasonic system (10) according to claim 13, further comprising a load sensor for detecting a load applied to the part (24) by the ultrasonic battery (14).

16. Ultrasonic system (10) according to claim 15, wherein the controller (30) receives a charge signal from the charge sensor and activates the ultrasonic stack (14) at a resonance and phase stored at startup that correspond to the charge signal.

17. Ultrasonic system (10) according to claim 13, wherein the load applied to the part (24) is predetermined.

18. Ultrasonic system (10) according to claim 13, wherein the ultrasonic stack (14) comprises a converter (18) and a horn (22).

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