KR0151231B1 - High frequency welding device and apparatus for welding using the welding device - Google Patents

Abstract

[purpose]

In an apparatus for high frequency welding by sandwiching a film with an electrode, it is possible to accurately detect the high frequency welding state of the electrode and to perform impedance matching adjustment and the like with high accuracy.

[Configuration]

The oscillation output from the crystal oscillation circuit A1 is amplified by the power amplifier circuit A2 and supplied to the seal electrode 4 via the impedance matching circuit E. The high frequency power supplied to the seal electrode 4 is extracted to the sensor (detection circuit) 30 through the stray capacitance DELTA C, rectified and detected in the diode D1, smoothed in the capacitor C1, and the DC voltmeter It is indicated by 31 as a DC voltage. The DC voltage displayed on this DC voltmeter 31 is proportional to the high frequency voltage Vo between the seal electrode 4 and the ground. When adjusting the capacitance of the variable capacitor Vc of the impedance matching circuit E, the display voltage of the DC voltmeter 31 is maximized, whereby the best high frequency welding can be performed.

Description

High frequency welding device and film packing device using the same

1 is a block diagram showing an embodiment of the present invention, a supply path of high frequency power to a high frequency welding electrode and a detection unit of the high frequency power.

2 is a circuit diagram showing an example of a specific configuration of a crystal oscillation circuit.

3 is a partial side view showing the supporting structure of the welding electrode.

4 is a circuit diagram showing another circuit configuration of the high frequency power detector.

5 is a perspective view showing a partial structure of a continuous filling packaging device as an example of an apparatus in which a high frequency welding apparatus of a film is used.

6 is a front view showing a package in which a cut tape is adhered by a partial seal line on a cylindrical film.

7 is a block diagram showing the configuration of a conventional high frequency power supply path.

* Explanation of symbols for main parts of the drawings

1 Film 1a, 1b Edge of film

2a, 2b: guide shaft 3: forming member

3a, 3b: edge portion 4: seal electrode

5: grounding electrode 6a, 6b: feed roller

7: stepper nozzle 8: vacuum tube

9: LC oscillator 11: Crystal oscillator

12: field effect transistor (FET) 13, Vc: variable capacitor

14 inductance element 15 coaxial cable

16: disconnection feeder 17: sliding trance transformer

18: isolation transformer 19: rectifier circuit

20, C1, C2: smoothing capacitor 21: voltage divider

23, 24, 27, 28: mounting screw 25: ceramic substrate

26: metal support plate 30: sensor (detection circuit)

31 DC voltmeter 31a: rotation control unit

32: detection piece 36: aluminum wire clip

A: high frequency output A1: crystal oscillation circuit

A2, b: power amplifier circuit B: crystal oscillation circuit

C, E: Impedance matching circuit D: High frequency power meter

F: DC power circuit G: Gate

L: Inductance element La: Probe (winding)

S: seal line a: high frequency oscillation circuit

d: high frequency power meter f: frequency

V: DC voltage Va, Vb: DC voltage

Vf: Output signal Vo: High frequency voltage

Zi: Impedance Zo: Output Impedance

D1, D2: Detection diode △ C: Floating capacitance

R1: Resistor Rx: Variable resistor

The present invention relates to a high frequency welding device, which is particularly suitable for welding a film by continuously supplying high frequency power to a pair of high frequency electrodes sandwiching an overlapping portion of a film, and to a film packaging device in which the high frequency welding device is assembled. It is about.

Background Art Conventionally, in the packaging field of a film containing food or various industrial products as a content, a high frequency seal is widely used as a means for bonding an overlapping portion of a film together with a hot plate seal or an ultrasonic seal. This high frequency seal melts and welds films together using the self-heating based on the dielectric loss of the film made of synthetic resin sandwiched between a pair of welding electrodes.

The manufacturing method of the film packaging body made from the food etc. has the process of shape | molding a film to cylindrical shape according to the shape of the content or desired product shape, and the overlapping part by which the width direction edge part of the film formed into the cylindrical shape overlapped each other. To form a longitudinal seal line. In this manufacturing method, since the longitudinal seal line is continuously formed at the overlapping portions of the edges of the film, there is little electrical load variation due to the pair of electrodes and the film sandwiched therebetween. For this reason, it is suitable for the high frequency sealing which requires the impedance matching with respect to a load.

As a high frequency welding apparatus used for manufacture of a film package, etc., the structure shown in FIG. 7 is generally used.

This high frequency welding apparatus has a high frequency output part which consists of a high frequency oscillation circuit (a), the power amplifier circuit (b) of a rear end, and the impedance matching circuit (c). The high frequency oscillation circuit (a) is a combination of a vacuum tube (8) and an LC (inductance capacitance) oscillation unit (9), and the high frequency power generated by the LC oscillation in the high frequency oscillation circuit (a) is amplified by the power amplifier circuit (b). Then, it is supplied between the pair of electrodes 4 and 5 via the impedance matching circuit c. The overlapping portions of the two films 1a and 1b sandwiched by the electrodes 4 and 5 are continuously welded. In addition, a measuring device such as a high frequency power meter d for detecting high frequency power is generally disposed between the power amplifier circuit b and the impedance matching circuit c.

In the production of the film packaging body, it is necessary that the high frequency welded portion of the film overlapping portion be in the best sealing state, and in order to do so, it is necessary to adjust and manage the sealing conditions (temperature, contact pressure, etc.) optimally. If this sealing condition is not optimal and the heating temperature of the film is too low, the welding of the films will be poor. On the contrary, if the heating temperature of the film is too high, the film material will be degraded or the film will be thinned at the welded portion. The welding strength is lowered. In particular, when packaging processed meat products, heat sterilization is performed after the film is packaged, or when the film shrinks due to heating, poor sealing or rupture of the package in a portion where the welding strength is reduced. It may occur. Therefore, in this kind of film package, it is necessary to adjust and manage the sealing conditions so that the films are welded to each other at high strength.

In the conventional high frequency welding apparatus, the sealing condition is monitored by the power instruction in the high frequency power meter d as shown in FIG. 7 or the detection value of the plate current of the vacuum tube 8 provided in the high frequency oscillation circuit a. Or, while the brightness of the neon tube provided in the seal electrode 4 was observed, the worker was performed by experience and feeling.

However, in the field of mutual welding of synthetic resin films, the dielectric constant of the film overlapping portion is higher than in other technical fields using high frequency, that is, induction heating of metal or semiconductor, and high frequency heating in dielectric heating of a living body (hyper thermite). There is a unique problem that the loss tan δ is low and therefore the load impedance is large.

Therefore, the difference between the output impedance from the power amplifier circuit b and the load impedance in the electrode part for welding is large. Therefore, even when the impedance matching circuit c is used, it is very difficult to completely match the output impedance with the load impedance. Therefore, in film packaging such as food, high frequency welding between films is performed in the presence of considerable reflected wave power and reactive power by radio wave radiation.

In such a state, when the power instruction by the high frequency power meter d or the flight current value of the vacuum tube is used as an index, the seal state control, adjustment and monitoring of the films cannot be sufficiently performed. This is because the reflected wave power and the magnitude of the radio wave radiation are also a function of the stray capacitance with respect to the ground potential of the single wire feed line and the seal electrode, and are easily changed thereby. When the reflectometer is installed in parallel with the high frequency power meter, the reflected wave power can be measured, but it is very difficult to quantitatively monitor the amount of radio wave radiation. In the display of the neon tube described above, since the luminance is visually observed, the accuracy of the index is low, and it is difficult to reproduce the adjustment operation of the impedance matching performed once.

Next, the high frequency oscillation circuit (a) using the vacuum tube (8) shown in FIG. 7 can be manufactured at a relatively low price because it is an electric circuit having a relatively small number of components and a relatively simple configuration. The vacuum tube is excellent in durability against stress.

On the other hand, however, since the oscillation frequency is dependent on the inductance and capacitance in the LC oscillation section 9, it is necessary to set this inductance and capacitance with high accuracy, which makes manufacturing and adjustment difficult. Since the vacuum tube 8 is used, the handling and mechanical durability at the time of transport and installation are inferior, and the use of the vacuum tube 8 also lowers the energy conversion efficiency from the power to the high frequency. have.

Thus, the inventors of the present invention fabricated a self-oscillating circuit using a field effect transistor (FET) instead of a vacuum tube, and assembled it into a high frequency welding apparatus such as the film of FIG. 7 to examine the suitability of the film for high frequency welding. . The result was a self-oscillating circuit having an LC oscillation section 9 depending on inductance and capacitance as a circuit even with a field effect transistor. Therefore, the load is based on the electrodes 4 and 5 and the film 1 sandwiched therebetween. When impedance matching with respect to impedance is performed, this adjustment operation also affects the oscillation frequency in the oscillation circuit, and it becomes apparent that the LC oscillation section 9 needs to be readjusted each time.

It is very inconvenient for the oscillation frequency to fluctuate every time the impedance matching is adjusted in the high frequency welding apparatus of the film in which impedance matching is always required according to the material and thickness dimension of the film to be used. In order to ensure the film packaging operation without any adverse influence on the outside, the interrelated tasks of impedance matching and frequency adjustment to the radiation frequency, which is recognized as industrial use in the radio wave method, are alternated so as to obtain optimum values simultaneously for each. It is required to carry out repeatedly. And this is a cumbersome and skillful task.

The power supply circuit of a conventional semiconductor high frequency power supply is a circuit for rectifying AC power from a commercial power supply to obtain a DC power. The DC power is a constant voltage for one of the high frequency oscillation circuit and the power amplifier circuit. In general, the other side is supplied as a variable voltage. Therefore, it is necessary to provide separate power supply paths to the high frequency oscillation circuit and the power amplification circuit, and there is a disadvantage that the whole structure becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to enable detection of a high frequency supplied to an electrode at or near the electrode for high frequency welding, and to allow impedance matching adjustment to be performed with high reproducibility and with high accuracy. It is done.

In addition, an object of the present invention is to make it possible to perform stable welding using a high frequency oscillation circuit having a semiconductor element such as a field effect transistor in a high frequency welding apparatus of a film, and to simplify the configuration of a power supply circuit. Doing.

The inventors of the present invention summarize the problems of the seal state control, adjustment, and monitoring method of the above-described films, and the solution is that it is necessary to accurately grasp the supply energy to the load. The present invention has been made in view of the fact that measurement is required, and that high frequency voltage is detected from the high voltage side electrode, and high frequency current is detected from the power supply to the electrode.

That is, in the high frequency welding apparatus which supplies high frequency electric power between a pair of high frequency electrodes through an impedance matching circuit from a high frequency output part, and welds by welding high frequency dielectric heating of the overlapping part of the film clamped between these high frequency electrodes, First, a detection circuit having a coupling portion capacitively coupled to the high voltage side electrodes of the pair of high frequency electrodes and a rectifying circuit for rectifying a signal obtained from the coupling portion is provided, and the detection circuit is applied to the high frequency electrode. A high frequency voltage is detected; or a probe inductively coupled to a feeder connecting the impedance matching circuit and the high voltage side electrodes of the pair of high frequency electrodes, and rectifying a signal from the probe. A detection circuit having a rectifier circuit is provided, and is provided to the high frequency electrode by this detection circuit. The high frequency current is detected.

In addition, the inventors of the present invention, as a high-frequency welding device for film, instead of a self-oscillating circuit based on a conventional LC oscillator, generate natural vibrations by vibrating elements such as quartz crystal oscillators, and use the field effect transistors for the vibrations. The use of the oscillation oscillation circuit tuned by the drain tuning circuit etc. was focused. According to the test oscillation circuit manufactured and tested, there is no change in the oscillation frequency even when the impedance matching with respect to the load on the welding electrode side is changed, and the oscillation does not stop due to the change of the supplied DC voltage. High frequency is output with sufficient change control range even if the variable DC is applied to both the high frequency oscillation circuit and the power amplification circuit in common. Accordingly, the power supply circuit can be simplified and the manufacturing cost can be reduced. Found.

That is, the high frequency welding apparatus of the film of this invention is characterized by consisting of an oscillation circuit having a high frequency output part having a vibration element and a tuning circuit for synchronizing with the natural vibration of the vibration element, and a power amplifier circuit at a subsequent stage.

As the power amplifier circuit, for example, a push-pull amplification circuit using a field effect transistor can be used.

In addition, a DC power supply circuit capable of varying the voltage output is provided, and the variable DC voltage obtained in the DC power supply circuit is divided to be supplied to the field effect transistor provided in the tuning circuit and the power amplifier circuit of the subsequent stage in common. It becomes possible.

Moreover, the film packaging apparatus which concerns on this invention is provided with the shaping | molding member which shape | molds a long strip | belt-shaped film in cylindrical shape, and the overlapping part of the edges of the film shape | molded in the cylindrical shape by this shaping | molding member is one of said high frequency welding The contents are filled into the film which is high frequency welded by the apparatus and further formed into a cylindrical shape.

In the above means, the high frequency voltage supplied to the high voltage side electrode of the pair of welding electrodes is extracted and rectified at the coupling portion of the detection circuit and displayed as, for example, a DC voltage. Alternatively, the high frequency current supplied to the high voltage side electrode is detected by the probe, rectified, and displayed as a DC voltage, for example. Since this DC voltage is roughly similar to the high frequency voltage or the high frequency current applied to the electrode for welding, high frequency welding can always be performed on the film under the best conditions when impedance matching is performed while monitoring the DC voltage. Become.

In the above means, the oscillation circuit of the high frequency output unit is constituted by a vibration element such as a crystal oscillator, a drain tuning circuit, and the like, and constitutes a vibration oscillation circuit which synchronizes and extracts the natural vibration of the vibration element by the tuning circuit. Since the oscillation frequency of the high frequency in this oscillation circuit is dependent on the natural frequency of the vibrating element, even if the impedance matching adjustment with respect to the load on the welding electrode side is performed, the oscillation frequency is not changed by this adjustment and the stable high frequency is maintained. Electric power can be provided to the welding electrode.

In the said oscillation circuit using the oscillation element, even if the DC voltage applied to the field effect transistors constituting the drain tuning circuit varies, oscillation of high frequency does not stop oscillation of the high frequency oscillation circuit and power. Even if it applies to both amplification circuits, it is possible to output a high frequency with sufficient change control width. Therefore, the power supply path can be single, and the structure of the power supply circuit can be simplified, thereby reducing the manufacturing cost of the entire apparatus.

Moreover, in the film packaging apparatus using these high frequency welding apparatuses, when welding the edges of a cylindrical packaging film, this welding state can be monitored with reproducibility, and the welding state can always be set satisfactorily, The film package of can be obtained.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, the Example of this invention is described based on drawing.

5 is a perspective view showing a part of a continuous filling packaging device for producing a so-called shell-shaped film package containing a food such as sausage.

In the continuous filling packaging device, the long band-shaped film 1 is guided to the cylindrical molding member 3 via the guide shafts 2a and 2b. This molding member 3 is formed in a cylindrical shape or the like by, for example, a plate material, and both edge portions 3a and 3b of the plate material are overlapped with a small gap. The film 1 is folded from the upper edge of the molding member 3 to the inner surface of the cylinder, and is molded into a shape substantially coincident with the inner surface shape of the molding member 3. At this time, both edge portions 1a and 1b of the film 1 are sandwiched by a gap where both edge portions 3a and 3b of the molding member 3 overlap each other and overlap each other.

The film formed in a cylindrical shape and overlapping the edges 1a and 1b is continuously sent downward by the transfer rollers 6a and 6b provided at the bottom, and the overlapping portions of the film edges are sealed with the seal electrode 4 and the ground. It passes between the electrodes 5. High frequency electric power is supplied between these electrodes 4 and 5, and the continuous longitudinal seal line S by high frequency welding is formed in the said overlap part of a film. Inside the film formed in a cylindrical shape, contents such as processed meat are filled and filled from the stepper nozzle 7, and the cylindrical film filled with contents is filled with a powder roller (not shown) disposed at the lower end again. By the bundle / cutting unit (not shown), and the bundle portion is bundled with an aluminum wire or the like and cut to form a shell-shaped film package such as holding.

As a material of the film 1 applicable to the apparatus which performs this kind of high frequency welding, a polyvinylidene chloride-type resin film is mentioned.

FIG. 1 is a block diagram showing a supply path of high frequency power to the electrodes 4 and 5 of the continuous charging packaging apparatus and a detection unit of the high frequency power.

The high frequency power supply path A, the high frequency power meter B, the impedance matching circuit 9E and the DC power supply circuit F are provided in the supply path of the high frequency power.

The high frequency output section A includes a crystal oscillation circuit A1 as a high frequency oscillation circuit and a power amplifier circuit A2 at a subsequent stage thereof.

The crystal oscillation circuit A1 is a circuit oscillating in synchronization with the natural frequency of the crystal oscillator 11, and an industrial radiation frequency of 13.56 MHz or 27.12 MHz is generally selected as the natural frequency of the crystal oscillator 11. .

The crystal oscillation circuit A1 has a structure as shown in FIG. 2, for example. The crystal oscillation circuit A1 has a field effect transistor (FET) 12, and the crystal oscillator 11 is connected between the gate G of the FET 12 and the ground. Between the drain D of the FET 12 and the ground, the variable capacitor 13 and the inductance element 14 are connected in parallel to form a drain tuning circuit. The fundamental frequency of the crystal oscillator 11 is tuned by adjusting the capacitance of the variable capacitor 13 and extracted as the oscillation signal Vf. In addition, the variable DC voltage Va applied in the DC power supply circuit F described below is supplied between the drain D and the gate G of the FET 12.

As the vibrating element capable of generating vibrations of natural frequency, in addition to the crystal oscillator 11, for example, a SAW element using a surface acoustic wave can be used.

As the power amplification circuit A2, a push-pull amplification circuit using a known FET is suitably used. The high frequency output signal Vf from the crystal oscillation circuit A1 is amplified with the power required for high frequency welding, and a coaxial cable is used. Via (15), it is supplied to the high frequency power meter (B). The amplification factor in this power amplifier circuit A2 changes on the basis of the DC voltage value from the DC power supply circuit F.

The high frequency power meter B measures and displays the high frequency power output from the high frequency output unit A. For example, the signal from the detection circuit that detects the high frequency power is displayed as traveling wave power and reflected wave power. A well-known display can be used, but a commercially available pass-type high frequency power crab is used in this embodiment. This pass-type high frequency power meter can change the detection range by replacing the element, and can also detect the power of the reflected wave by reversing the direction of the element as well as the traveling wave power, and is suitable for the high frequency welding apparatus of the film of the present invention.

The impedance matching circuit E loads the electrode (more precisely, the electrodes 4 and 5 and the disconnection feed line 16) by the overlapping portion of the film 1 being sandwiched between the pair of welding electrodes 4 and 5. Load circuit included] and the impedance matching between the high frequency output unit A and the L type impedance matching circuit having the inductance element L and the variable capacitor Vc. The distance between the impedance matching circuit E, the seal electrode 4 and the ground electrode 5 is the shortest distance allowed in the device arrangement, and between the impedance matching circuit E and the seal electrode 4 is the disconnection feed line. It is connected by (16). In this impedance matching circuit E, impedance matching adjustment is performed by adjusting the capacitance of the variable capacitor Vc.

This impedance matching circuit E has a relationship between the Q value and the frequency f of the impedance matching circuit E when the output impedance of the power amplifier circuit A2 is Zo and the impedance by the load on the electrode side is Zi. The setting adjustment as shown in Equation 1 below is performed.

The DC power supply circuit F has a sliding transformer 17 for varying the commercial AC voltage, and the DC voltage exceeds a predetermined value even when the voltage transformed by the sliding transformer 17 is maximum. The insulating transformer 18, the rectifier circuit 19, and the smoothing capacitor 20 are selected so as to be selected. In this DC power supply circuit (F), a direct current rectified by the rectifying circuit (19) and smoothed by the smoothing capacitor (20) is obtained, and the DC voltage (V) is tunably adjusted by the sliding motion (17). have.

The voltage divider 21 is provided in the supply path of the DC power obtained by the DC power supply circuit F, and the DC voltage V is divided by resistance by the voltage divider 21 at a predetermined ratio. This divided DC voltage Va is supplied between the drain D and the gate G of the FET 12 of the crystal oscillation circuit A1 as shown in FIG. Similarly, the divided DC voltage Vb is supplied to the drain and the gate of the FET installed in the power amplifier circuit A2.

That is, in the present embodiment, the DC voltage variably adjusted by the sliding transformer 17 in the DC power supply circuit F is divided, so that the amplification factor in the power amplifier circuit A2 is variably adjusted. In (A1), it was confirmed that the power amplifier circuit A2 had a sufficient output control range without the oscillation being stopped.

It was also found that the crystal oscillation circuit A1 can obtain stable oscillation without causing a change in the oscillation frequency by the impedance matching adjustment.

Next, the configuration of the detection unit of the high frequency power will be described.

The supporting structures of the seal electrode 4 and the ground electrode 5 used in the continuous filling packaging device are as shown in FIG.

The ground electrode 5 is provided inside the overlapping portion of the edge portions 1a and 1b of the film 1 which is molded into a cylindrical shape and continuously sent downward, and is in contact with the ground. The seal electrode 4 faces the overlapping portions of the edge portions 1a and 1b of the film 1 from the outside and is fixed with mounting screws 23 and 24 to the ceramic substrate 25 for insulation. . The disconnection feed line 16 from the impedance matching circuit E is in terminal contact with one of the mounting screws 24 and electrically connected to the seal electrode 4.

The ceramic substrate 25 fixed to the metal support plate 26 with mounting screws 27 and 28 is provided with a sensor 30 including a detection circuit, which is fixed by the mounting screw 27. have. The metal support plate 26 is connected to ground, and the metal support plate 26 and the ground electrode 5 are set to approximately the same potential. Specifically, the metal support plate 26 is mounted on a known inter-electrode distance control device or contact pressure control device mounted on the crosspiece of the packaging device.

In the sensor 30 for measuring the voltage value of the high frequency power applied to the seal electrode 4, a small circuit board is accommodated in the shield case, and the shield case is made of metal through the mounting screw 27. It is connected to ground by the support plate 26.

In the small circuit board in the sensor 30, as shown in FIG. 1, electronic components such as resistor R1, smoothing capacitor C1, and die diagram D1 are mounted to form a detection circuit. The sensor 30 is provided with a detection piece 32, which is close to the seal electrode 4 and faces through the space. DELTA C shown in FIG. 1 and FIG. 3 is a stray capacitance between the detection piece 32 and the seal electrode 4. As shown in FIG.

As shown in FIG. 3, the sensor 30 is connected with a DC voltmeter 31 as a voltage display section. Rx in FIG. 1 is a variable resistor for sensitivity adjustment. As shown in Fig. 3, the DC voltmeter 31 is provided with a rotation control unit 31a for sensitivity adjustment. The resistance value of the variable resistor Rx is varied by the operation of the rotary operation unit 31a, whereby the sensitivity adjustment of the detection voltage by the DC voltmeter 31 is performed.

Next, the operation of the detection unit of the high frequency power will be described.

The high frequency voltage applied to the seal electrode 4 is divided by the impedance of the stray capacitance DELTA C and the resistance R1. The high frequency voltage divided by and induced by the resistor R1 is rectified by the diode D1 and smoothed by the capacitor C1, and is also displayed as a DC voltage by the DC voltmeter 31. At this time, by adjusting the resistance value of the variable resistor Rx by the rotation operation unit 31a, the sensitivity of the detected voltage by the DC voltmeter 31 is adjusted.

The DC voltage displayed on the DC voltmeter 31 is proportional to the high frequency voltage Vo between the seal electrode 4 and the ground. Therefore, by monitoring the DC voltage displayed on the DC voltmeter 31, the strength and weakness of the high frequency voltage applied to the seal electrode 4 can be known. When the impedance matching adjustment is performed by the impedance matching circuit E, the high frequency voltage Vo of the seal electrode 4 when the tuning frequency adjusted by the impedance matching coincides with the frequency oscillated in the crystal oscillation circuit A1. This is the maximum.

Accordingly, when adjusting the capacitance of the variable capacitor Vc of the impedance matching circuit E, the high frequency voltage Vo of the seal electrode 4 is found by finding the adjustment point at which the display voltage of the DC voltmeter 31 is maximized. Can be maximized and the high frequency induction heating of the film 1 can be carried out most efficiently.

Next, the initial adjustment of the high frequency welding apparatus of the said film, and the adjustment operation at the time of operation are demonstrated.

[Initial adjustment]

① Between the seal electrode 4 and the ground electrode 5, the overlapping portions of the edge portions 1a and 1b of the film 1 are sandwiched and the feed rollers 6a and 6b are driven to drive the film 1. Send continuously downwards.

② By adjusting the sliding transformer 17 of the DC power supply circuit F, the DC voltage V output from the DC power supply circuit F is gradually raised. By raising this DC voltage V, the high frequency power from the high frequency output part A gradually rises, and this is monitored by the high frequency power meter B. As shown in FIG. At this time, when the indicator hand of the DC voltmeter 31 is slightly shaken, the adjustment of the sliding transformer 17 is stopped.

③ Adjust the variable capacitor Vc of the impedance matching circuit E so that the display voltage of the DC voltmeter 31 is maximized. At this point in time, the output impedance Zo of the high frequency output unit A and the impedance Zi on the electrode side are matched, whereby the film 1 can be in a state where the high frequency induction heating can be performed most efficiently.

(4) Next, while watching the formation state of the vertical seal line S (refer FIG. 5) formed in the film 1, the sliding motion transformer 17 is added and subtracted and the high frequency voltage Vo is obtained so that the best sealing state may be obtained. ).

When the adjustment up to (4) is completed, the display voltage of the DC voltmeter 31 is set as a subsequent working reference value. The power display at the high frequency power meter B at this time is a reference value.

[Adjustment at the time of driving]

After performing the said initial adjustment, when carrying out the film welding of the same product, it becomes possible only by the following operation adjustments.

(1) The film (1) is sandwiched between the seal electrode (4) and the ground electrode (5), and the film (1) is continuously sent downward by the rotation of the transfer rollers (6a, 6b).

② Adjust the sliding transformer 17 to match the indicated voltage of the DC voltmeter 31 with the reference value obtained in the initial setting.

Only by this operation, the same welding seal state can always be reproduced, and the welding quality of a film can be improved and made uniform.

Moreover, when the kind, thickness dimension, etc. of the film to be used are changed, the impedance Zi of an electrode side will change. In this case, the initial setting is performed again, and the indication voltage of the DC voltmeter 31 is set to the new reference value in the state of being in the best sealing state. This is done by adjusting the transformer 17.

Incidentally, the structure of the detection unit of the high frequency power is not limited to that shown in FIG. 1, but can also be a structure shown in FIG.

4, a winding probe (La) is wound around the single wire feed line (16) from the impedance matching circuit (E) to the seal electrode (4), and the feed line (16) and the probe (La) of high frequency power are wound. ) Is inductively coupled. The coupling portion of the probe La is set at a position as close as possible to the seal electrode 4.

If the winding number of the winding of the probe La is T turn and the high frequency current flowing through the disconnection feed line 16 is I, a high frequency current of (i = I / T) is induced in the circuit of the probe La. do. The DC voltage is displayed on the DC voltmeter 31 by detecting the voltage when the detection current i flows through the variable resistor Rx, rectifying it in the diode D2, and smoothing it with the smoothing capacitor C2. .

The DC voltage display of this voltmeter 31 is similar to the value I of the high frequency current flowing through the disconnection feed line 16 and the seal electrode 4. When the impedance matching is performed by the impedance matching circuit E, the high frequency current is maximized so that the display voltage of the DC voltmeter 31 becomes maximum. Therefore, by adjusting the variable capacitor Vc of the impedance matching circuit E so that the display of this DC voltmeter 31 becomes the maximum, the best high frequency welding is attained.

Next, the film packaging test using the high frequency welding apparatus of this invention and the performance test result of the obtained package are demonstrated.

Automatic filling packaging apparatus [trade name "KAP"; The semiconductor high frequency welding apparatus shown in FIG. 1 instead of the conventional high frequency welding apparatus (the apparatus shown in FIG. 7) of Kureha Kagaku Kogyo Kagashi Co., Ltd. of Japan, and Using a device modified to have a high frequency voltage detection device, a vinylidene chloride-based resin film (trade name "Creharon", a thickness of 40 µm, a width of 70 mm, and the product described above) was supplied to the method described in this specification. Thus, a cylindrical package was produced.

First, only the operation | work which shape | molded the film to cylindrical shape and continuously longitudinally welded to the seal line S, without performing content filling and binding with an aluminum wire was performed. The obtained cylindrical bag was cut into a predetermined length and the performance test was performed. One end of the sample of the cylindrical bag was sealed, and an internal pressure test was performed while gradually increasing the air pressure of 0 to 1.5 kg G / cm 2 from the opening side of the other end. This pressure test was carried out on each of ten samples. As a result, there was no problem that the seal line S was injured or air leaked from the seal line S, and it was found that a seal line having an internal pressure of at least 1.5 kgG / cm 2 or more could be formed.

Next, a shell-shaped sausage package body having a diameter of about 20 mm and a length of 150 mm was manufactured by using the ground meat. 100 packages were put in a pressure-resistant container and subjected to a retort sterilization test at a hot water temperature of 120 ° C. for 15 minutes (internal pressure of 2 kgG / cm 2). There was no rupture or any abnormal package.

As described above, the high-frequency power detecting circuit according to the present embodiment has a high-frequency voltage applied near the high-frequency electrode as shown in FIG. 1 or both high-frequency currents as shown in FIG. It corresponds to the current, but only relative value. Of course, it is possible to make the absolute value with proper calibration, but from the original purpose of the detection circuit to control and monitor the welding state of the film, there is no particular difference between the relative value and the absolute value. Rather, in the high frequency welding which induces internal heat generation to the thin synthetic resin film which is an electrical insulator, the load impedance is much higher than that of the induction furnace and the bio heating, so that the internal impedance of the high frequency power source (high frequency output unit) Although the large difference between the two can be best matched in the impedance matching circuit, the amount of the invalid electromagnetic energy and the reflected wave power radiated in the form of radio waves in the disconnection feed line 16 and the seal electrode 4 of FIG. The fact that the electric power meter B not only obtains an uncertain power value that does not correspond to the seal state but also is very susceptible to the influence of the external environment is a problem.

The present invention provides a means for solving the above problem, and since it detects a high frequency voltage or a high frequency current in the vicinity of the high frequency electrode, the present invention is hardly affected by the radiant energy and the reflected power, and is realized by the welding state of the film. It is based on the knowledge that accurate and accurate control and monitoring is possible. Further, both the high frequency voltage detection circuit (FIG. 1) and the high frequency current detection circuit (FIG. 4) of the present invention may be used to detect high frequency power by an arithmetic unit giving the product of these outputs.

In the above embodiment, the case where the overlapping portions of the edge portions 1a and 1b of the packaging film 1 wound in the cylindrical shape as shown in FIG. 5 has been described is high frequency welding. When using the simple strip | belt-shaped film which is not shape | molded by etc., this film can also be performed also when two sheets of this film are piled up planarly, and the overlap part is continuously high frequency welded.

Further, in the embodiment shown in FIG. 5, the processed food is continuously filled in the tubular molded film 1 by the stepper nozzle 7, but the film packaging apparatus of the present invention is of this kind. It is not limited to the continuous filling device, for example, after the film is molded into a cylindrical shape, a solid food or the like is supplied therein, and the film is flattened at a position between the contents to be welded. This also applies to the case where the film shrinks by heating. Moreover, in this case, the contents are not only limited to food but also to industrial products and the like.

FIG. 6 shows a shell-shaped package as shown in FIG. 1 of Japanese Patent Application Laid-Open No. 1, 1989). In the manufacturing process of this package, in the apparatus like FIG. 5, the edge parts 1a and 1b of the film 1 are overlapped, and high frequency welding is carried out by the electrodes 4 and 5, and the longitudinal seal line S is formed. At the same time, a narrow cut tape 35 is attached over the entire length of the cylindrical bag, and the electrodes 4 and 5 shown in FIG. 5 are cut tape 35 by seal electrodes and ground electrodes provided separately. And the film 1 of the package body are partially high frequency welded, so that a partial seal line S is formed. The contents are filled in the cylindrical bag, and are divided at predetermined intervals and tied together by the aluminum wire claws 36.

In the manufacture of such a package, the partial seal line S is welded to the welding (main seal) which forms the longitudinal seal line S at the overlapping part of the film edge, and the cut tape 35 and the film 1. The welding (tape seal) to form is performed simultaneously.

When the high frequency welding device for the main seal which continuously forms the longitudinal seal line S as described above, and the high frequency welding device for the tape seal which oscillates intermittently to form the partial seal line S1 are operated in parallel,

(a) Place two pairs of high frequency electrodes as far apart as possible,

(b) two pairs of high frequency electrodes are arranged in a radial direction of the cylindrical film at an angle of 90 degrees;

(c) Take countermeasures such as varying the oscillation frequency of the high frequency power supply. However, in the case of using the conventional vacuum tube high frequency welding apparatus having a large radiant energy and a high reflected power, when the high frequency for tape sealing is periodically It can be seen that the high frequency intensity of the main seal is generally weakened by interfering with the high frequency for the main seal. Technically adjusting this interference to make both compatible is a great task that requires skill and time. However, when the high frequency welding apparatus of the present invention is used for both the main seal and the tape seal, or at least for the main seal, there is little interference on the high frequencies of both seals, but almost no adjustment is required. The longitudinal seal line S and the partial seal line S are always formed stably. Therefore, this Example becomes one of the very preferable embodiment about manufacture of the package like FIG.

In the invention according to claim 1 or 2, since the high frequency is detected at or near the electrode for high frequency welding of the film, a high frequency detection value proportional to the high frequency voltage value or the high frequency current value is obtained. Detection corresponding to the state is possible. By using the detected value based on the high frequency current, the high frequency voltage diagram can accurately monitor the welding state of the film, and on the basis of this detected value, high accuracy adjustment of the output impedance of the high frequency output unit and the load impedance of the electrode unit can be performed. It can be carried out in the process, and it can always reproduce the best welding condition.

In the invention as recited in claim 3, the high frequency oscillation circuit provided in the high frequency output unit is a vibration oscillation circuit composed of a vibration element such as a crystal oscillator and a tuning circuit that tunes to the natural frequency of the element. Even when the impedance matching adjustment with the electrode side is performed, the oscillation frequency is always stabilized, thus eliminating the need for frequent adjustment of the high frequency oscillation circuit.

In the invention described in claim 4, the power amplifier circuit is constituted by a push-pull amplifier circuit, whereby stable high frequency amplification can be achieved by a small circuit.

In the invention according to claim 5, in the case where the amplification of the power amplifier circuit is adjusted by the variable DC voltage from the DC power supply circuit, even if the variable DC voltage is directly applied to the high frequency oscillation circuit, Oscillation does not stop. By applying a variable DC voltage to both the high frequency oscillation circuit and the power amplifier circuit in this way, since a single DC power supply circuit can be provided, the device structure can be simplified and the manufacturing cost can be reduced.

Claims (5)

A high frequency welding device for supplying high frequency power between a pair of high frequency electrodes through an impedance matching circuit from a high frequency output unit, and welding the overlapping portions of a film sandwiched between the high frequency electrodes by high frequency dielectric heating to weld the pair of high frequency electrodes. A detection circuit having a coupling portion capacitively coupled to the high voltage side electrode, and a rectifying circuit for rectifying a signal obtained from the coupling portion, wherein the detection circuit detects a high frequency voltage applied to the high frequency electrode. High frequency welding apparatus of film to be made. A high frequency welding device for supplying high frequency electric power between a pair of high frequency electrodes through an impedance matching circuit from a high frequency output unit, and welding the overlapping portions of the film sandwiched between the high frequency electrodes by high frequency dielectric heating and welding the same. A detection circuit having a probe inductively coupled to the feeder portion connecting the high voltage side electrodes of the pair of high frequency electrodes and a rectifying circuit for rectifying the signal from the probe is provided. A high frequency welding apparatus of a film, characterized in that a high frequency current applied to the film is detected. In the high frequency welding apparatus which supplies a high frequency electric power between a pair of high frequency electrodes through an impedance matching circuit from a high frequency output part, and welds the overlapping part of the film clamped between these high frequency electrodes by high frequency dielectric heating, and the said high frequency output part vibrates. An oscillation circuit having an element and a tuning circuit for synchronizing with the natural vibration of the vibrating element, and a power amplification circuit at a rear end thereof, wherein the film is a high frequency welding apparatus. The film high frequency welding apparatus according to claim 3, wherein the power amplification circuit is a push-pull amplification circuit. The DC power supply circuit according to claim 3 or 4, wherein one DC power supply circuit capable of varying the output voltage is provided, and the output voltage obtained from the DC power supply circuit is divided and installed in the tuning circuit. High frequency welding device for film supplied to amplification circuit.