EP2996847B1 - Device for cutting a process material using ultrasound and cuting method - Google Patents

Description

The invention relates to a method for cutting a process material, in particular food, such as meat, cheese, vegetables, bread or pasta, using ultrasound energy and a working according to this method cutting device having a blade which is acted upon by ultrasonic energy.

In many industrial applications, especially in the food industry, products of the intended dimensions must be provided. Often bread, meat products, in particular sausages, or cheese are divided into pieces and packed. For this purpose, various cutting devices are used in practice.

From [1], DE102005006506A1 , a cutting device is known in which a vertically vibrating saw blade is used for cutting. The oscillation path and the oscillation frequency of the saw blade are variably adjustable within certain limits. The saw blade is driven by a vibration motor integrated in the housing. The vibration motor drives the saw blade so that it makes a constant movement up and down. The path covered by the saw blade is adjustable between 1 / 10mm and 5mm. With such a cutting device, a process material can not normally be cut to the desired quality. Furthermore, the action of a vibration motor with a high load of the blade is to be expected.

Advantageously, the process material can be processed with a cutting device in which a knife with Ultrasonic energy is applied. A device of this kind is known from [2], EP2551077A1 , known. The ultrasound energy emitted by an ultrasound transducer is supplied to the knife via at least one arcuate, preferably U-shaped coupling element, which is welded on the one hand to the blade back of the blade and, on the other hand, is connected to the ultrasound transducer, for example via a threaded bore and a coupling screw. The cutting device described allows compared to conventional systems to process a process material faster and more precise.

The user specifies in this cutting device the operating parameters that are used when using the knife. These operating parameters depend in particular on the process material, which is to be processed or cut into pieces. In particular, the clock cycles are determined by means of which the knife is moved cyclically. Within one working cycle, the knife is either rotated once or moved back and forth. The clock cycles can only be increased within the range within which the quality of the executed cuts is guaranteed. As soon as deformations or cracks occur in the process material, the cutting speed must be reduced again.

If the consistency of the process material changes during a continuous cutting process, quality defects can occur. If the user has coordinated the cutting processes to a process material and a first batch has been processed, quality defects may occur when processing another batch, if the latter has different properties.

The cutting device known from [2] can be equipped with a long knife which is held on both sides and moved upwards and downwards perpendicular to its orientation, in order to alternately cut a process material fed above and below the knife. Such knives are expensive to manufacture and correspondingly expensive. On the other hand, these knives can be used for a long time if used optimally. If, on the other hand, operating parameters are wrongly selected for a given process material, increased wear on this knife can occur. Device parts may heat up and defects may occur.

From [3], DE102009045945A1 , a machine tool is known, which has a drive unit for ultrasonic excitation of a tool, wherein a device for outputting an information signal is provided, the frequency and / or amplitude of which is varied as a function of the operating parameters of the power tool. During operation of the electric machine tool, a slight vibration of the handle portion, which is felt by the user, can occur with a low amplitude, in order to impair the current operating state without affecting the handling of the power tool. On the other hand, this solution can not be used for fully automatic production equipment.

Within a scan or sweep, therefore, the optimal frequency in terms of power is only generated once, while outside this frequency point many less suitable frequencies are generated. The properties of the cutting device and the cutting properties of the blade therefore change during the frequency sweep.

The present invention is therefore based on the object to provide an improved method for cutting a process material using ultrasound energy and an improved cutting device with a blade, which operates according to this method.

Based on the inventive method, the blade should be operated as constant as possible in an optimal operating point. The blade should also be operated as gently as possible, so that stress and wear are avoided.

The cutting device should be able to operate with higher efficiency, in particular with higher clock cycles.

The process material should be able to be cut with high precision, high cycle rates and consistently high cutting quality. The cut products, in particular food slices should have flat cut surfaces and uniform thicknesses. The precision is to be maintained even when the strength properties of the supplied food or parallel supplied food units change.

When changing the properties of the process material, especially when processing different batches of process material, no quality defects and no higher loads on the blade or other device parts should occur.

This object is achieved by a method for cutting a process material using ultrasound energy and a cutting device operating according to this method, which have the features specified in claims 1 and 13, respectively having. Advantageous embodiments of the invention are specified in further claims.

The method is used to operate a cutting device, which is provided for processing, in particular for cutting a process material and which has at least one blade, which is driven by a drive device and which is supplied via at least one energy converter and a coupling element of ultrasonic energy from an ultrasonic unit.

According to the invention, a control unit is provided which controls the ultrasound unit such that the frequency of the ultrasound energy supplied via preferably only one coupling element of the blade is keyed between at least a first and a second operating frequency or the ultrasound energy of the blade via a first coupling element with a first operating frequency is preferably supplied via a second coupling element with a second operating frequency, which are fixed or each keyed between at least two frequency values or operating frequencies.

The inventive coupling of the ultrasonic energy allows the blade to cut the process material with little energy and virtually no effort. The surface waves occurring on the blade separate the structure of the process material before the blade is guided deeper against the process material. This allows a rapid penetration of the blade, without deformations occur in the process material.

Due to the Umtastung the operating frequencies or the coupling of two different operating frequencies a uniform distribution of the ultrasonic energy takes place along the cutting edge of the blade. Wave knots of standing waves occurring at the first frequency are superimposed or detached by wave tusks occurring at the second frequency. The cutting edge thus oscillates completely, which is why an optimal effect is achieved when the blade penetrates into the process material. Stationary wave nodes where the ultrasonic energy can not act are avoided.

By transposing between at least two advantageous operating frequencies, in which a good or optimal coupling of the ultrasonic energy into the blade, it is ensured that the blade is always operated optimally. A scan or sweep of the ultrasonic frequency is avoided, so that unfavorable ultrasonic frequency ranges are not passed through. According to the invention, therefore, an optimum operating frequency is always set, while in a scan or sweep, a large number of different frequencies is set step by step, of which only a few deliver optimal results.

The blade can be moved back and forth or rotated in a plane that is perpendicular to the drive axis. Furthermore, combined cutting movements can be realized. For example, the blade is guided forward and then moved laterally. During the rotation of the blade, it does not have to be slowed down and accelerated again, but can be continuously rotated in the same direction without energy losses. The control of the working cycles of the knife can thus be done in a simple manner by controlling a drive motor. The maximum working frequency is not determined by the performance of the drive device, but by the maximum cutting speed, with the Blade can be passed through the process material. Since this maximum cutting speed is very high in the inventive application of ultrasonic energy, very high clock cycles can be achieved.

Any process material can be processed or cut with the cutting device. In particular, foods, e.g. Meat, bread, pasta, dairy products, paper, cardboard, plastic, metal, precious metals, e.g. Gold and silver, can be processed with this cutting device advantageous.

The application of ultrasonic energy, for example at operating frequencies in the range of e.g. 30-40 kHz gives the inventively designed knife particularly advantageous properties. The ultrasonic energy is preferably coupled via the large side surfaces of the blade back transverse to the cutting direction of the blade in the blade. A blade facing the end of the coupling element is preferably perpendicular to the blade. Upon application of the ultrasonic energy, elastic waves result within and / or on the surface of the blade, which intensify towards the cutting edge. Particularly advantageous waves result in a curved or curved configuration of the coupling element, which is preferably designed U-shaped.

The blade can only be provided with a cutting edge on one side or on opposite sides. The cutting device is designed such that the blade can be moved or rotated in both directions and guided against a process material.

In a rotating blade, the drive shaft is mounted on at least one bearing element and connected to the drive shaft, which is directly or indirectly connected via drive elements, such as gears and timing belt, with a drive unit, such as an electric motor. The drive shaft further carries the energy converter or the energy converter and the ultrasonic unit. In principle, it is only necessary that the energy converter connected to the coupling element, for example a piezoelectric element, is rotated together with the drive shaft. Only in preferred embodiments, the ultrasonic unit is also connected to the drive shaft and rotatably supported.

Energy and / or control signals can be fed to the energy converter and / or the ultrasound generator or a control unit connected thereto and likewise held rotatably via an electrical coupling unit. Control signals can also be transmitted via a radio interface, for example according to the Bluetooth method. Also possible is the optical transmission of control signals.

In a rotating blade, the ultrasonic energy is transmitted via a coupling element or via two coaxially aligned coupling elements, which are aligned perpendicular to the blade. In a blade that is moved back and forth, the coupling of ultrasonic energy via a coupling element or via a plurality of coupling elements can be carried out. Preferably, a coupling element is provided on each side of the blade. By means of the two mutually separate coupling elements, it is advantageous to couple ultrasonic energy into the blade at a first and a second frequency.

According to the invention, the operating frequencies are selected taking into account the maximum values of the amplitudes, optionally the resonance frequencies, which occur when the blade penetrates into the process material.

For this purpose, an energy converter or sensor is preferably provided which detects the mechanical ultrasonic waves occurring on the blade and converts them into corresponding electrical signals which are evaluated, for example, in a signal processor.

The maximum values or the resonance frequencies are preferably determined while the process material is being cut. Based on the determined maximum values or resonant frequencies, the operating frequencies can be advantageously determined. If two or more maximum values or resonance frequencies, ie the global maximum and a local maximum of the measured amplitudes occur, the operating frequencies between these two resonance frequencies or maxima can be keyed over. In this case, the blade always works at resonance or at maximum values. If only a maximum occurs in the entire frequency response of the blade and in the work area, then a first operating frequency can be applied to the resonance frequency and a second operating frequency in the adjacent region of the resonance frequency such that only minimal losses occur in the second operating frequency. Alternatively, operating frequencies are selected, one on the lower and the other on the upper side of the resonant frequency. The distances from the resonance frequency are selected in such a way, preferably the same or different, that the smallest possible losses occur and at the same time the required displacement of the standing waves or the wave nodes is achieved. For example, frequency intervals between the operating frequencies in a range of preferably 5 Hz to 10 kHz selected.

The keying between the first and the second operating frequency can take place symmetrically or asymmetrically in time. For example, during a longer first time interval, the preferred operating frequency and, during a shorter second time interval, the operating frequency that deviates from the resonant frequency or at which greater losses occur are selected.

The keying between the operating frequencies is carried out with a Umtastfrequenz, which is preferably in a range of 2 Hz to 500 Hz. All parameters, in particular the Umtastfrequenz are preferably selected depending on the consistency of the process material and / or the molecular structure of the process material and / or the cutting speed. Even at a high cutting speed, it can therefore be ensured that the intersection of two stationary working frequencies or the scanning of operating frequencies results in the cut being made correctly, without interfering vibration nodes occurring at the cutting area where the material is compressed and only separated with a delay. With soft process material a higher Umtastfrequenz is usually selected. On the other hand, a higher Umtastfrequenz is preferably selected even with crystalline process material.

To optimize the cutting quality, measurements are carried out before and / or preferably during the cutting process. On the basis of these measurements, the vibration behavior of the blade is determined, which results in the coupling of ultrasonic energy with a certain frequency. Of particular interest is The behavior of the blade while the blade is passed through the process material.

In preferred embodiments, the blade is connected directly or via one of the coupling elements to a sensor, preferably a transducer element, by means of which vibrations of the blade are detected, converted and transmitted as electrical signals to the control unit and evaluated there. In this way, the vibration behavior of the blade over the entire frequency range or work area can be determined.

By means of the sensor, the oscillation amplitude of the blade and / or the phase position of the vibrations of the blade with respect to a reference signal and / or the normally exponential decay of the vibrations of the blade are determined. For example, the ultrasonic waves emitted by the ultrasonic transducer serve as the reference signal. Data are determined in particular for new or already determined resonant frequencies, operating frequencies and / or for new test frequencies.

In a preferred embodiment, a broadband pulse is delivered to the blade as a test signal, after which the resulting vibrations are measured. For example, a signal having a plurality of frequencies is applied to the blade, of which at least one is preferably the operating frequency. As a result, the resulting oscillations, which decay faster or slower, can be evaluated, for example, by means of a Fourier transformation in order to determine resonance frequencies and their amplitudes and decay rates.

Alternatively, the frequency response of a frequency sweep can be measured by passing through the relevant frequency range with an ultrasonic signal and recording the resulting vibrations.

After determining the frequencies at which the blade has a good or optimal vibration behavior, the operating frequencies are set to these frequency values or moved into areas for the higher or maximum amplitudes and / or a lower phase shift and / or a slower decay of the vibrations were determined.

Measurements are performed continuously or at intervals, with the operating frequencies preferably being optimized while the blade is passing through the process material.

The reception of ultrasonic energy from the blade is preferably at intervals during which no ultrasonic energy is delivered to the blade, or in which the ultrasonic vibrations delivered to the blade have a zero crossing.

Alternatively, ultrasonic energy is continuously delivered to the blade, after which a corresponding portion of the delivered ultrasound energy is subtracted from the received ultrasound energy to determine the natural vibration of the blade.

In preferred embodiments, the control unit is designed such that the amplitude of the ultrasonic waves delivered to the blade can be controlled or regulated in order to be able to couple a desired power into the blade.

In preferred embodiments, the optimization of the operating frequencies is performed first. Subsequently, the readjustment of the vibration amplitudes to the desired values takes place. This readjustment or the resulting oscillation amplitude can in turn be checked by measuring the vibration behavior of the blade.

In preferred embodiments, at least one temperature sensor, for example an infrared sensor, is provided, by means of which the temperature of the sonotrode or the blade or the coupling elements is preferably measured without contact. In particular, in the region of the points where transitions are present and ultrasonic energy is coupled from a first into a second medium, the temperature is preferably measured. During operation of the cutting device, in particular during the regulation of the amplitude of the ultrasonic vibrations, the temperature is preferably monitored in order to detect mismatches or other defects. Once a conspicuous increase in temperature or a high power consumption of the blade is detected, an alarm can be triggered and the cutting device can be switched off. Alternatively, when a maximum temperature is exceeded, the supplied ultrasonic power is reduced. As a result, the cutting device, the process material and / or the process parameters are checked in order to determine any possible causes of the error.

The inventive method can be used particularly advantageously in cutting devices in which blades are used to cut a process material. On the other hand, the method according to the invention can also be advantageously used in devices which use any sonotrodes by means of which process goods, how foods or pharmaceuticals are processed. For example, the inventive method can be advantageously used in devices which have a blade as a sonotrode, which does not serve the cutting, but the sputtering or the transport of a process material. For example, the method according to the invention can also be used in devices which have a sieve as a sonotrode, by means of which, for example, a foodstuff or a pharmaceutical substance is sieved. This avoids that vibration nodes can remain in the region of individual pores of the sonotrode or the screen.

The inventive cutting device can be coupled with any other devices to cut a process material. For example, the cutting device is arranged at the end of a conveyor chain, on which a process material is to be cut into individual parts. Particularly advantageously, the inventive cutting device can also be arranged at the outlet of an extruder, so that the extruded material can optionally be divided into shorter or longer elements. A single cutting device can serve several extruders or conveyors. A device according to the invention can therefore be equipped with a sonotrode which performs various tasks, such as cutting, filtering, sieving, sputtering, transporting and fluidizing, e.g. Fluidizing a bulk material, can meet.

Fig. 1

eine erfindungsgemässe Vorrichtung zum Schneiden eines Prozessguts 8A, 8B, welches unterhalb und oberhalb einer Klinge 11 zugeführt wird, die von einer Antriebsvorrichtung 12 gehalten wird und der über zwei Ultraschallwandler 13 Ultraschallenergie von einer Ultraschalleinheit 4 zuführbar ist, die zudem zum Empfang von Ultraschallsignalen geeignet ist, die von der Klinge 11 wieder entnommen wurden;

Fig. 2

eine erfindungsgemässe Vorrichtung zum Schneiden eines Prozessguts 8, umfassend eine Schneidevorrichtung 1 mit vier Klingen 11A, ..., 11D, mittels denen ein Prozessgut 8, welches in Form von Stangen 8A, ..., 8L auf einem Fördertisch 93 zugeführt wird, in Scheiben 89 geschnitten wird;

Fig. 3

die Schneidevorrichtung 1 von Fig. 2, mit zwei Antriebseinheiten 12A, 12B mittels denen die Klingen 11A, ..., 11D nach unten und wieder nach oben verschiebbar sind;

Fig. 4a

ein eine Klinge 11 mit einem Kopplungselement 15, auf dem ein erster Energiewandler 131 angeordnet ist, dem Ultraschallenergie zugeführt wird, und auf dem ein zweiter Energiewandler 132 angeordnet ist, welcher auf der Klinge 11 auftretende Ultraschallwellen erfasst und in elektrische Signale wandelt, die von der Steuereinheit 6 ausgewertet werden;

Fig. 4b

ein Spektrogramm mit einem Ultraschall-Impuls TP mit Schwingungen mehrerer Frequenzen f1, f2 und f3, welche an die Klinge 11 abgegeben werden sowie dem Verlauf der Schwingungen, der anschliessend gemessen und ausgewertet wird;

Fig. 5

die Klinge 11 von Fig. 4a mit zwei Kopplungselementen 15A, 15B, an die Ultraschallwandler 13A, 13B angeschlossen sind;

Fig. 6

die mehrkanalige Ultraschalleinheit 4 und die Steuereinheit 6 in einer vorzugsweisen Ausgestaltung;

Fig. 7a

die Klinge 11 von Fig. 5 mit den Ultraschallwandlern 13A, 13B, die mit einer Ultraschalleinheit 4 verbunden sind, die Ultraschallsignale abgibt und empfängt;

Fig. 7b

ein Frequenzdiagramm mit Frequenzen f1, 11a, f1b; f2, f2a, f2b, die durch Überprüfung des Schwingungsverhaltens der Klinge 11 bzw. anhand des Frequenzgangs V der Klinge 11 optimiert werden; und

Fig. 7c

an der Klinge 11 auftretende stehende Wellen sw1, die Schwingungsknoten swk und Schwingungsbäuche swb aufweisen.

The invention will be explained in more detail with reference to drawings. Showing:

Fig. 1

an inventive device for cutting a process material 8A, 8B, which below and is supplied above a blade 11, which is held by a drive device 12 and the ultrasound energy can be supplied via two ultrasonic transducers 13 from an ultrasound unit 4, which is also suitable for receiving ultrasonic signals, which were removed again from the blade 11;

Fig. 2

an inventive device for cutting a process material 8, comprising a cutting device 1 with four blades 11A, ..., 11D, by means of which a process material 8, which is supplied in the form of rods 8A, ..., 8L on a conveyor table 93, in Slices 89 is cut;

Fig. 3

the cutting device 1 of Fig. 2 with two drive units 12A, 12B by means of which the blades 11A, ..., 11D are displaceable downwards and upwards again;

Fig. 4a

a blade 11 with a coupling element 15, on which a first energy converter 131 is arranged, to which ultrasonic energy is supplied, and on which a second energy converter 132 is arranged, which detects ultrasonic waves occurring on the blade 11 and converts them into electrical signals, which are generated by the Be evaluated control unit 6;

Fig. 4b

a spectrogram with an ultrasonic pulse TP with oscillations of several frequencies f1, f2 and f3, which are delivered to the blade 11 and the course of the vibrations, which is subsequently measured and evaluated;

Fig. 5

the blade 11 of Fig. 4a with two coupling elements 15A, 15B to which ultrasonic transducers 13A, 13B are connected;

Fig. 6

the multi-channel ultrasonic unit 4 and the control unit 6 in a preferred embodiment;

Fig. 7a

the blade 11 of Fig. 5 with the ultrasonic transducers 13A, 13B connected to an ultrasonic unit 4 which outputs and receives ultrasonic signals;

Fig. 7b

a frequency diagram with frequencies f1, 11a, f1b; f2, f2a, f2b, which are optimized by checking the vibration behavior of the blade 11 or by the frequency response V of the blade 11; and

Fig. 7c

Standing waves sw1 occurring on the blade 11 and having nodes swk and antinodes swb.

Fig. 1 shows a device 1 for cutting a process material 8A, 8B, which is supplied below and above a cutting tool or a blade 11 which is held by a drive device 12. It is shown that the drive device 12 holds the blade 11 on both sides with holding arms 121 which can be moved synchronously vertically downwards and upwards. The holding arms 121 may be connected to holding members fixed to the blade 11. Advantageously, the retaining arms 121 can be connected to the coupling elements 15A, 15B, via which the ultrasonic energy is coupled into the blade 11 (see Fig. 5 ).

By means of the drive device 12, the blade 11 can be guided downwards and upwards in order to cut a first or a second portion of the supplied process material 8A, 8B in each direction of movement. The blade 11 has for this purpose an upper cutting edge 101 and a lower cutting edge 102.

For carrying out the method according to the invention, the cutting device 1 has a correspondingly designed control unit 6, a correspondingly configured ultrasound unit 4 and correspondingly configured ultrasonic transducers 13a, 13b. The ultrasonic transducers 13a, 13b are connected by means of coupling elements 15A, 15B to the blade 11, preferably welded. In principle, any coupling or any desired configuration of the coupling elements 15A, 15B can be used to implement the method according to the invention.

The ultrasound unit 4, which communicates with and is controlled by the control unit 6, has at least one transmission channel 41 and preferably at least one reception channel 42. A transmission channel 41 has, for example, a fixed or variable oscillator, for example a voltage-controlled oscillator VCO or a synthesizer. By means of the preferably controllable oscillator or synthesizer frequencies are optionally generated in the ultrasonic range and fed to a preferably controllable output amplifier, as described below with reference to Fig. 6 will be described in more detail.

A transmission channel 41 of the ultrasound unit 4 can be connected to a plurality of ultrasound transducers 13A, 13B or energy converters 131 (see FIG Fig. 6 ), which convert the electrical ultrasonic vibrations into mechanical ones Convert ultrasonic vibrations and feed the blade 11 via the coupling elements 15A, 15B. The ultrasonic transducers 13A, 13B can be supplied with identical ultrasonic signals. Alternatively, the ultrasound transducers 13A, 13B can be supplied via switches with ultrasonic signals having different frequencies in the time-sharing method. Furthermore, a separate transmission channel 41 can be provided for each ultrasonic transducer 13A or 13B.

By means of the control unit 6, the ultrasound unit 4 is controllable such that the frequency of the ultrasound waves supplied to the blade 11 can be keyed between at least a first and a second operating frequency f1a, f1b. Both ultrasound transducers 13A, 13B may have the same frequencies, which are preferably keyed within a few milliseconds. Preferably, however, the ultrasonic energy of the blade 11 is supplied via a first coupling element having a first operating frequency f1 and via a second coupling element having a second operating frequency f2, which are fixed or between at least two operating frequencies f1, f2 and f1a, f1b; f2a, f2b are keyed over (see the frequency diagram in Fig. 7b ). The two ultrasonic transducers 13A, 13B are preferably supplied with different frequencies, so that a frequency mixture results on the blade 11 and vibration nodes do not appear or appear only for a very short time.

If only one coupling element is provided, then the frequencies f1, f2 or f1a, f1b; f2a, f2b keyed in the time sharing method. Alternatively, two or more frequencies may be superimposed and coupled into the blade 11.

In Fig. 1 It is further shown that in a preferred embodiment, ultrasound energy can be coupled out from the blade 11 and transmitted to the control unit 6 via one or more receiving channels 42 provided in the ultrasound unit 4. As will be described below, the ultrasonic vibrations sensed on the blade 11 are evaluated to determine the vibration behavior of the blade 11 at the selected process parameters.

In Fig. 1 It is illustrated that measurements during a cutting operation are preferably performed several times. While the blade 11 passes through the process material 8A, signals sk1,..., Sk5 are coupled out by the blade 11 at short time intervals and transmitted via the receiving channels 42 to the control unit 6. If an optimal vibration behavior of the blade 11 is determined, then the process parameters are not changed. If, however, a disadvantageous vibration behavior is detected, the process parameters are changed in such a way that the vibration behavior is gradually improved. The process parameters are preferably readjusted after each scan of vibrations on the blade 11 and their evaluation. While the blade 11 is guided through the process material 8, thus, improvements and adjustments of the cutting process can be made continuously. The cutting processes are therefore not only optimized in cases where the preceding and following process material differ. Corrections are also effective for process material, which has different properties along the cross section or the cut surface.

Through optimizations and adjustments, not only will the best cutting quality be achieved, but also a minimum of stress achieved the cutting device. On the one hand, partial blockages during the execution of the cut are prevented. On the other hand, energy losses and a corresponding heating of the blade 11 are avoided.

An optimal vibration behavior of the blade 11 occurs in the region of the resonance frequency of the blade 11. As a starting point for the choice of process parameters, therefore, the specified by the manufacturer resonant frequency of the blade 11 can be selected. Depending on the nature of the process material 8, which is to be processed by the blade 11, the resonance frequency and thus the vibration behavior of the blade 11 will change, so that by means of the in Fig. 1 illustrated measurements of the signals sk1, ..., sk5 a continuous optimization by determination of the resonant frequency is sought, which currently occurs during processing of the process material.

In particular, the global maximum within the frequency response of the blade 11 is determined. Advantageously, local maxima which occur within the frequency response can also be determined. As a result, a frequency shift keying is preferably carried out between the determined maxima. In particular, care is taken that the operating frequencies f1a, f1b or f1, f2 are selected and keyed in such a way that resulting vibration nodes swk do not overlap.

The operating frequencies are preferably chosen such that the first and the second operating frequency f1a, f1b are preferably at the same frequency spacing below and above the detected resonant frequency f1, or that one of the operating frequencies f1a precise at the resonant frequency f1 and the second operating frequency f1b in an area where only minimal attenuation occurs.

When using only one resonance frequency or only one maximum, the distance between the first operating frequency, which occurs at resonance or at a maximum, and the at least one second operating frequency is preferably kept as small as possible and as large as necessary, so that stationary wave nodes are avoided and the ultrasonic energy can act on the process material over the entire cutting edge of the blade. For example, in this case, a frequency spacing in the range of 5 Hz to 500 Hz is selected. Advantageously, an asymmetric switching can be provided with a longer residence time in the range of the frequency at which higher amplitudes occur.

The distance between the operating frequencies f1a and f1b is preferably in a range of 5 Hz to 10 kHz. Depending on the frequency response of the blade 11 smaller or higher frequency intervals are selected.

The keying of the first and the second operating frequency f1a, f1b or f1, f2 takes place with a Umtastfrequenz, which is preferably in a range of 2 Hz to 500 Hz. The keying is temporally symmetric or asymmetrical. For example, during a longer first time interval, the resonance frequency is applied to the blade 11, while a different working frequency is applied to the blade 11 for a shorter second time interval. In this case, by means of the blade 11 during the first time interval, an optimal effect on the process material 8 and during the second time interval a Elimination of obstacles that remain after the first time interval.

As mentioned, the method according to the invention can be used with different cutting devices or also with other devices with other ultrasonic sonotrodes.

Fig. 2 shows a cutting device 1 with four cutting tools 11A, ..., 11D, a pushing unit 95 with a pushing tool 94, two drive devices 12A, 12B for driving the cutting tools 11A, ..., 11D, and a conveyor table 3, on which the process material 8 stored and can be pushed by means of the pushing tool 94 toward the cutting tools 11A, ..., 11D. The cutting device 1 is held by a mounting structure 5.

The process material 8 is fed in parallel to the four cutting tools 11A,..., 11D in twelve cylindrical or rod-shaped units 8A,..., 8L, so that in each case three of the process material units 8A,..., 8L of one of the cutting tools 11A; ...; 11D cut simultaneously. On the front side, the processing units 8A,..., 8L fed in parallel are held in a desired position by a hold-down while the cut is being carried out.

The cutting unit 1 comprises the four cutting tools 11A; ...; 11D, which are each connected to an ultrasonic transducer 13 and can be vertically lowered by the driving devices 12A, 12B and raised again to cut off slices 89 from the process material units 8. The discs 89 fall on a conveyor belt 92 of a receiving conveyor 9, which has a drive motor 91.

Furthermore, a control unit 6 is provided which can control the cutting device 1, the conveying devices and the ultrasound unit 4. The control unit 6 is connected via a first control line 61 to the drive devices 12A, 12B, a second control line 62 to the conveyor devices, a third control line 63 to the ultrasonic unit 4 and a fourth control line 69 to the take-off conveyor 9. The control unit 6 can be supplied with information via a keyboard and measuring devices 71, 72, such as measuring formers and sensors, by means of which the cutting process and the conveying process can be controlled.

Fig. 3 shows the dismantled cutting device 1 of Fig. 1 comprising two identically constructed cutting modules held by a mounting plate which is part of the mounting structure 5 of the device. Each of the cutting modules comprises a drive unit 12A; 12B and a bearing device 128A connected to the mounting structure 5; 128B, which allows a respective first and second bearing block 129A, 129B to lower and raise vertically. At each storage block 129A; 129B, two ultrasonic transducers 13A, 13B and 13C, 13D are each arranged, which are each connected via a coupling element 15 with a cutting tool 11A, 11B, 11C or 11D.

The cutting tools 11A, ..., 11D each comprise a blade 11, at the back of which the arcuate coupling elements 15 are welded, whereby the ultrasonic energy can be coupled into the blades 11.

Fig. 4a shows that the coupling element 15 is connected to a beam 130, for example screwed, on the one the first energy converter 131 is arranged, to which ultrasonic energy is supplied, and on which a second energy converter 132 is arranged, which detects ultrasonic waves occurring on the blade 11 and converts them into electrical signals which are transmitted to the control unit 6. The beam 130, which forms an ultrasonic transducer 13 together with the energy converters 131, 132, has, for example, a screw on the front, which is screwed into a threaded bore in the coupling part 15. The ultrasound unit 4 has a plurality of transmission channels 41 and a plurality of reception channels 42, so that a plurality of ultrasound transducers 13 can be operated.

The energy converters 131, 132 preferably each comprise a piezoelement, which is enclosed between two electrodes, for example metal plates, one of which abuts against the beam 130 and the other is connected to an electrical connection line 401, 402. The first energy converter 131 is supplied from a transmitting channel 41 of the ultrasonic unit 4 via the connecting line 401 electrical ultrasonic signals. The second energy converter 131 or the sensor 71 detects mechanical ultrasonic waves from the blade 11 and converts them into electrical ultrasonic waves, which are supplied from the second connecting line 402 to a receiving channel 42 of the ultrasound unit 4. The received ultrasonic waves are optionally amplified, filtered and converted and fed to an evaluation module 600 in the control unit 6. The evaluation module 600 determines the current vibration behavior of the blade 11 and compares this with target values, after which corrective measures are determined. For example, it is determined that at least one of the operating frequencies is to be postponed, or that the signal amplitude of at least one of the operating frequencies should be increased or reduced. Corresponding information is output by the evaluation module 600 to a control module 60, which determines the operating frequencies, the Umtastfrequenzen, the Umtastintervalle and the signal amplitude and provides corresponding control signals. For controlling the evaluation module 600 and the control module 60, an operating program is provided which controls the program sequence and can communicate via interfaces with the user and external computers or electronic units.

The process optimization can be done in different ways. As mentioned, the vibration behavior of the sonotrode or the blade 11 can be continuously monitored and optimized. However, the control unit 6 can also automatically try to optimize the process parameters. For this purpose, the control unit 6 can deliver test signals TP to the blade 11 during the working process or during test phases and evaluate the echo signals f1, f2, f3. The evaluation of the test signals and the operating signals or operating frequencies, which are detected during the course of the process, can take place in the same way.

Fig. 4b shows by way of example a spectrogram with an ultrasonic pulse TP, which comprises vibrations with several frequencies f1, f2 and f3. After the ultrasonic pulse has been applied to the blade 11, the vibration behavior of the blade 11 or the further course of the vibrations f1, f2 and f3 is examined. It is checked with which amplitudes the individual vibrations f1, f2 and f3 occur and how quickly they decay. The curves df1, df2 and df3 show the courses of the decay of the oscillations f1, f2 and f3. After the evaluation module 600 those Has detected frequencies at which a maximum oscillation amplitude and a minimum attenuation occur, the corresponding information is passed to the control module 60.

If the frequency f2 is the operating frequency, the test pulse TP, for example, two frequencies f1, f3 are added, which are below and above the operating frequency f2. As a result of the evaluation of the echo signals of these three frequencies f1, f2, and f3, it can be ascertained that a higher amplitude and a lower attenuation occur at the frequency f1. The evaluation module 600 will therefore output the information to the control module 60, after which a better oscillation behavior of the blade 11 can be achieved with the frequency f1 as the new operating frequency. The control module 60 can take over the frequency f1 directly as a new operating frequency or include the information in the further evaluation process. Preferably also parameters are included in the evaluation, which affect the properties or expected changes of the process material 8.

Fig. 5 shows blade 11 of Fig. 4a with two coupling elements 15A, 15B to which ultrasonic transducers 13A, 13B are connected. In principle, the ultrasound units 4 can also be partially or completely integrated into the ultrasound transducers 13A, 13B. It is shown that the blade 11 is held by the coupling elements 15A, 15B which are welded to the blade 11. The coupling elements 15A, 15B in turn are held by symbolically shown holding arms 121, as described with reference to FIG Fig. 1 has been described.

Fig. 6 shows by way of example the multi-channel ultrasound unit 4, which is connected via a bus system 63 to the control unit 6 in order to exchange data. The ultrasound unit 4 has two transmission channels 41 and two reception channels 42.

Each transmit channel 41 comprises a D / A converter 411, which converts the digital commands of the control unit 6 into analog control signals which can be fed to a controllable oscillator 412. Instead, it is also possible to use a synthesizer which can be controlled directly by the control unit 6 and at the same time can deliver a plurality of operating frequencies. The vibrations emitted by the controllable oscillators 412 are each supplied to a controllable amplifier 413, which outputs the oscillations with an optional amplitude to the energy converter 131. The control of the amplifiers 413 again takes place through the control unit 6 or the control module 60. At the same time, therefore, a plurality of ultrasound signals having a selected frequency and selected amplitude can be output to the envisaged energy converters 131 and ultrasound transducers 13.

Each receive channel 42 preferably includes an input amplifier 421, preferably a subsequent filter stage 422 which passes only the frequencies of interest, and an A / D converter which converts the analog signals to digital data. The digital data is passed to the evaluation module 600, which comprises, for example, a signal processor and is preferably suitable for carrying out the Fourier transformation.

Fig. 7a shows the blade 11 of Fig. 5 with the ultrasonic transducers 13A, 13B, which are connected via line systems 40A, 40B to an ultrasound unit 4, the Transmitting and receiving ultrasonic signals, as with respect to the FIGS. 4a, 4b and 6 has been described.

It is shown that the cutting device 1 is in operation and at the cutting edge of the blade 11 two standing waves sw1, sw2 occur, which overlap each other, so that wave nodes swk of one standing wave sw1 are within shaft tails swb of the other standing wave. The two shafts sw1, sw2 can be superimposed on one another or switched on alternately, so that each zone of the process material to be cut is exposed to the maximum intensity of the ultrasonic energy within a few milliseconds, if appropriate within a fraction of a millisecond, and an optimum cutting profile is ensured. In Fig. 7c is the first standing wave sw1 illustrated with wave node swk and wave bumps swb.

In Fig. 7a are also temperature sensors 72, 73, preferably infrared sensors, shown by means of which the temperature of the blade 11 or the coupling elements 15A, 15B, in particular the connection points, can be monitored. If a critical temperature rise is detected, the power delivered to the blade 11 can be reduced. Furthermore, a test procedure can be performed to detect erroneous process parameters. For example, the frequency response of the blade 11 is recorded to detect shifts in the resonance frequencies. In this way, it can be prevented in time that the blade 11 is damaged.

Fig. 7b shows a frequency diagram with frequencies f1, f1a, f1b, f2, f2a, f2b, which are adjustable by the control module 60. To determine the operating frequencies of the frequency response V of the blade 11 is preferably added, the in Fig. 7b is shown as an example. It can be seen that the frequency response V has four maxima which are above a defined threshold value s.

The maxima M1,..., M4 are at the points where the ultrasonic energy optimally penetrates into the blade 11 and can cause it to oscillate. The mechanical vibrations are converted for example by piezoelectric elements into electrical signals whose voltage profile or amplitudes in Fig. 7b are drawn.

The frequencies of the maxima lying above this threshold value s are suitable as working frequencies. M3 is the global maximum while M1, M2 and M4 are local maximum. The operating frequencies are now selected such that the wave nodes and the antinodes of the resulting standing waves overlap. In the present example, the operating frequencies f1 and f2 were chosen at the locations of the global maximum M3 and the local maximum of the M2. Alternatively, combinations of the frequencies of said maxima, e.g. M3 and M4 or M1, M2 and M4, and M1 and M4, respectively. Alternatively, a resonant frequency f1 is determined, after which operating frequencies f1a, f1b are determined on both sides of the resonant frequency f1 and fed to only one or both ultrasonic transducers 13A, 13B. It is shown that the maxima, for example due to the change in the consistency of the process material 8, migrate and the operating frequencies f1, f2 or f1a, f1b are adjusted accordingly and continuously optimized according to the method according to the invention.

Preferably, several recipes are provided with which certain process parameters for a blade 11 and preferably a certain process material 8 are fixed. Process parameters are, for example, the operating frequencies, the vibration amplitudes preferably for each of the operating frequencies, the Umtastfrequenz, the minimum and maximum power, and the maximum temperature of the blade 11. Recipes can be permanently adjusted or sequentially or randomly selected and set. By measuring the vibration behavior of the blade 11 in each recipe, the optimal formulations can be immediately selected and applied. In preferred embodiments, therefore, not only a switching of a single process parameter, but a group of process parameters, possibly an entire recipe. The formulations are preferably continuously optimized and stored again by means of the measuring methods according to the invention. If changes in the process material 8 occur, therefore, suitable formulations can be used immediately.

Claims (15)

1. Method for operating a cutting device (1), which is designed for cutting a process material, particularly foodstuff (8) and which comprises at least one cutting tool in the embodiment of a blade (11), which is driven by a drive device (12) and to which ultrasonic energy is supplied from an ultrasound unit (4) via at least one energy converter (13) and a coupling element (15), characterised in that a control unit (6) is provided, which controls the ultrasound unit (4) during cutting of the process material in such a way, that the frequency of the ultrasonic energy, which is supplied to the blade (11) via only one coupling element (15), is keyed between at least a first and a second operating frequency (fla, f1b) or that the ultrasonic energy is supplied to the blade (11) via a first coupling element (15A) with a first operating frequency (f1) and via a second coupling element (15B) with a second operating frequency (f2), which first and second frequencies are fixed or keyed between at least two operating frequencies (f1, f2 or f1a, f1b; f2a, f2b).
2. Method according to claim 1, characterised in that the oscillation amplitudes of the blade (11) are measured before or during processing the process material (8) for a plurality of test frequencies or operating frequencies and that one or a plurality of frequencies are determined, at which an absolute or relative maximum value of the oscillation amplitude occurs.
3. Method according to claim 1 or 2, characterised in that the operating frequencies (fla, f1b or f1, f2) are selected and keyed in such a way, that the resulting nodes (swk) do not overlap.
4. Method according to claim 1, 2 or 3, characterised in

   a) that the first and the second operating frequency (fla, f1b or f1, f2) are located preferably in an equal frequency distance below and above a determined frequency, at which the maximum value of the oscillation amplitude occurs, or

   b) that one of the operating frequencies (fla) is located at the frequency, at which a maximum value of the oscillation amplitude occurs,

   c) wherein the distance between the operating frequencies (fla, f1b or f1, f2) is selected in a range of preferably 5 Hz to 10 kHz.
5. Method according to one of the claims 1 - 4, characterised in that keying between the first and the second operating frequency (fla, f1b or f1, f2) is done with a keying frequency that is located preferably in a range of 2 Hz to 500 Hz and/or that keying between the first and the second operating frequency (fla, f1b or f1, f2) is done symmetrically or asymmetrically in time.
6. Method according to one of the claims 1 - 5, characterised in that the blade (11) is connected directly or via one of the coupling elements (15A, 15B) to a sensor (71), preferably a converter element (132), with which oscillations of the blade (11) are sensed, converted and forwarded as electrical signals to the control unit (6) and are evaluated there.
7. Method according to claim 6, characterised in that during an interval one or a plurality of test frequencies (f1, f2, f3) are applied to the blade (11), whereafter the resulting oscillations are sensed, converted, optionally processed by applying a Fourier-transformation and are evaluated.
8. Method according to claim 7, characterised in that the receipt of ultrasonic energy from the blade (11) is done during intervals, in which no ultrasound oscillation is applied to the blade (11).
9. Method according to claim 6, 7 or 8, characterised in that the amplitude or the duration of the decay of the oscillations of the test frequencies is determined, whereafter the test frequencies are used as operating frequencies (fla, f1b or f1, f2), for which the higher amplitudes or a slower decay of the oscillations had been registered.
10. Method according to one of the claims 6-9, characterised in that measurements are made continuously or in time distances and the operating frequencies (f1, f2 or f1a, f1b; f2a, f2b) are optimised, while the blade (11) is guided through the process material (8).
11. Method according to claim 8 or 9, characterised in that ultrasonic energy is supplied continuously to the blade (11) and that a corresponding share of the supplied ultrasonic energy is subtracted from the received ultrasonic energy, in order to determine the self-oscillation of the blade (11).
12. Method according to one of the claims 9 - 11, characterised in that sensors (72, 73) are provided, with which the temperature of the blade (11) or of the coupling elements (15A, 15B) is measured and that the supplied ultrasonic energy is reduced when a predetermined maximum temperature is exceeded.
13. Cutting device (1) designed for the application of the method according to one of the claims 1-12 with at least one cutting tool in the embodiment of a movable or rotatable blade (11) that is connected with a drive device (12) and to which ultrasonic energy can be supplied from a ultrasound unit (4) via at least one energy converter (13) and a coupling element (15), characterised in that a control unit (6) is provided, with which the ultrasound unit (4) is controllable during cutting of the process material in such a way, that the frequency of the ultrasonic energy, which is supplied to the blade (11) via only one coupling element (15), can be keyed between at least a first and a second operating frequency (fla, f1b) or that the ultrasonic energy is supplied to the blade (11) via a first coupling element (15A) with a first operating frequency (f1) and via a second coupling element (15B) with a second operating frequency (f2), which first and second frequencies are fixed or keyed between at least two operating frequencies (f1, f2 or f1a, f1b; f2a, f2b).
14. Cutting device (1) according to claim 13, characterised in that at least one sensor (71, 72) and one converter (41) are provided, with which ultrasonic energy can be sensed at the blade (11), can be converted and transferred to the control unit (6), in which a signal processing module (60) is provided, with which signals derived from the blade (11) can be evaluated and corresponding measurement results can be gathered and that a control module (600) is provided, with which the ultrasound unit (4) is controllable according to the gathered measurement results, in order to further optimise the measurement results.
15. Cutting device (1) according to claim 13 or 14, characterised in that at least one temperature sensor (72, 73) is provided, which is mechanically coupled, directly or indirectly, with the blade (11) and that is connected to the control unit (6), which is designed for observing the temperature of the blade (11) or of the coupling element (15A, 15B) as well as for controlling the ultrasound unit (4), so that at high temperatures the ultrasound power is reduced and/or or an alarm signal is provided.

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