JPH03231831A - Method and apparatus for ultrasonic sealing of film made of synthetic resin - Google Patents

Abstract

PURPOSE:To carry out sealing completely even in the case where the sealing of a film tube whose contents include an oily substance is intended, by providing an ultrasonic wave horn and/or a heating means for heating an anvil. CONSTITUTION:A tube into which contents are injected is sent downward in the state of being held and pressed by holding/pressing rollers 23, and a flattened part 2'B which contains no contents is formed. Under such a condition, a sealing device 24 works on the flattened part 2'B to complete sealing. In this case, the flattened part 2'B is held and pressed by an ultrasonic wave horn 24A and an anvil 24B having a heating source and is applied with an ultrasonic wave and heated as well to be sealed at this place. This sealing portion is formed into a linear shape by four protruding lines provided on the anvil 24B. However, the residue of the contents in the flattened part 2'B is eliminated from the sealing portion in the linear shape by the ultrasonic wave, and the inner surface of the film tube are directly contacted with each other, thereupon the ultrasonic sealing can be carried out. In this case, since the sealing portion is heated through its outer surface that contacts with the anvil 24B, the sealing operation can be promoted.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for ultrasonically welding overlapping parts of synthetic resin films.

[Prior Art] Conventionally, devices for welding the overlapping portion formed by overlapping a plurality of synthetic resin films include a thermal welding type in which the overlapping portion is compressed with a heating element, or an ultrasonic horn. A widely known type of welding is performed by applying ultrasonic waves while applying pressure with an anvil.

(Problems to be Solved by the Invention) However, when the above-mentioned welding device is adopted in such a conventional device, the heating element heats the film from the outside and applies heat to the welding layer on the inner surface of the film at the overlapped portion. Therefore, in order to weld in a short time, the outer surface of the film must be at a temperature higher than the melting point of the welding layer, and the temperature of the welding layer must be higher than the melting point of the welding layer. There is a problem that the film, which has softened significantly at the welding edge of the body, may be damaged, or the film may adhere to the heating element.Therefore, even if the welding strength is somewhat insufficient, the film may be damaged. The temperature must be kept at a level that will not cause it to stick.

Furthermore, in ultrasonic welding, since energy is directly supplied to the welding layer on the inner surface of the film, the outer surface of the film is not heated excessively, and there is no problem as in the case of welding using a heating element. However, since a commercially available ultrasonic vibrator is used, the frequency is usually fixed, and in order to increase the welding strength, the amplitude must be increased or the application time must be lengthened. However, if the amplitude is too large, there is a risk of damage such as holes in the film, which is not desirable when the purpose of welding is sealing, and therefore there is a limit to the sealing strength. This brings about the problem of reduced operating efficiency of the device, and is not a positive solution in any case.

Particularly harsh conditions are encountered when welding films, as the purpose of welding is for sealing, and tube-shaped films are formed by stacking the opposite edges of a band-shaped film in a position where the same sides of the film meet. This is the case of an automatic filling device that, after filling the container with the contents, locally applies pressure to form a flat portion without the contents, and laterally seals the flat portion.

In this conventional automatic filling and packaging device, the tube has a film edge piece that protrudes outward in the form of a band.
When forming the flat portion, the thickness of the flat portion differs between the edge portion and the other portions in the width direction of the tube, so that the problem with sealing becomes even greater in addition to the above-mentioned problem. In other words, there are four films on the edge and two films on the other parts. This also applies when the tube is in the form of a gusset with folds on both sides.
Particularly in this case, there are three parts including the edge piece part that have different thicknesses from the other parts. Even if such a tube is compressed to form a flat part where no contents exist, a small amount of the contents will be sucked into the area between the two films and return again, remaining there. If the tube is not completely sealed, the seal strength will decrease, the appearance of the sealed part will deteriorate, and furthermore, the contents will remain at the cut end of the tube when it is cut, resulting in spoilage at the cut end if the contents are food. This brings about the problem.

Furthermore, when ultrasonic sealing is employed as a solution to the sealing described above, there is an idea of increasing the sealing width (the length of the region in the longitudinal direction of the tube). This ultrasonic seal remains in the gap between the flat parts,
Alternatively, it has the advantage of sealing while eliminating the contents that enter through capillary action using ultrasonic waves. However, if you try to uniformly seal a wide area before and after the cut part with the aim of achieving a perfect seal, the limited energy will be dispersed over a wide area and the energy per unit area will decrease. In addition to the sealing failure, the contents to be excluded simply move within the area, and the objective cannot be achieved. This problem is particularly noticeable when the contents contain oil.

The present invention solves the problems of the above-mentioned conventional devices in this type of device, and uses ultrasonic welding to seal films whose contents contain oil. It is an object of the present invention to provide an ultrasonic welding method and an apparatus therefor that can perform a complete seal even if there is a problem.

[Means to solve the problem]

According to the present invention, the above object is achieved by: heating an ultrasonic horn and/or an anvil in a method of ultrasonically welding overlapping portions of synthetic resin films.

Furthermore, regarding the apparatus for carrying out the above method, the apparatus for welding the overlapped parts of synthetic resin films by ultrasonic waves is equipped with a heating means for heating the ultrasonic horn and/or the anvil. .

(Function) In the present invention as described above, heat from the outside by the ultrasonic horn and/or anvil is transmitted to the welding layer on the inner surface of the film, and the welding layer is heated and softened.

On the other hand, ultrasonic waves are directly applied to the welding layer to easily weld the softened welding layer. In other words, the temperature of the horn and/or anvil of the present invention, which is also a heating element, is sufficient to promote ultrasonic welding as long as the temperature of the welding layer is raised to a certain degree, without requiring the high temperature required by conventional heating elements alone. A good weld can be obtained. As a result, the outer surface of the film is at a much lower temperature than in the conventional case. Note that it is sufficient that the ultrasonic application and heating times overlap at least, and the start and end times do not necessarily have to coincide.

Further, the amplitude or time of the ultrasonic wave application and the degree of heating may be extremely small compared to conventional devices that perform each of them individually. Furthermore, heating! It is possible to use either a sonic horn or an anvil.

(Example) Hereinafter, an example of the present invention will be described based on the accompanying drawings.

In addition, in the examples, the welding conditions for welding the overlapped parts of synthetic resin films are particularly severe, as described above, in the case of sealing in automatic filling and packaging equipment, and in addition, the number of films in the overlapped parts differs depending on the location. A case of gusset-type packaging will be explained. However, the present invention is not limited to this case, and can be widely applied to welding of the above film.

In FIG. 1, reference numeral 1 denotes a raw material, and a band-shaped film 2 made of synthetic resin is wound into a roll. The film 2 passes through a guide roller 3.4 to a forming plate 5, where it is formed into a cylindrical shape with an edge portion 2A.

A welding device 6 is disposed below the forming plate 5. The welding device 6 includes a guide tube 6A that guides the cylindrical film, and a vertical sealing hot plate 6B that includes a pair of block-shaped bodies disposed above the side of the guide tube 6A.
(see FIG. 1(B)) and a pair of pressure rollers 6C (see FIG. 1(C)) located below the rollers. In this welding device 6, the edge portion 2A of the cylindrical film is heated and melted by passing between the pair of vertical sealing hot platens 6B, and is then pressed by a pressure roller 6C. It is then sent in two tubes.

A nozzle 7 serving as an injection device for injecting the contents is inserted through the upper opening of the forming plate 5, passes through the guide tube 6A of the welding device, and its tip reaches a position below the guide tube 6A.

The upper end of the nozzle 7 is connected to a pump 9, for example a gear pump, for discharging the contents in the hopper 8, and the nozzle 7 is further connected at its intermediate portion to an accumulator 10 with a piston device 10A. The pump 9 rotates continuously, and the piston device 10A of the accumulator 10 operates at the same cycle as the operating cycle of a sealing device, which will be described later.

U-shaped guides 11 extending in the vertical direction are attached to both side surfaces of the lower end portion 7A of the nozzle 7, which is a portion of the welding device that projects downward from the guide tube 6A. The guide 11
is a U that opens radially outward as shown in Figure 1(D).
It is shaped like a letter and guides the tube 2° so that its cross section is approximately square, and a folding plate 12 is inserted into the U-shaped groove of the guide 11 to form folds on the side of the tube 2°. However, it has a so-called gusset shape. The guide 11 and the folding plate 12 are provided at three locations above and below, and a pair of feed rollers 13 are provided at an intermediate position as shown in FIG. 1(E).
is provided, and the tube 2° is continuously fed downward while sandwiching the folded portion between the folding plates 12. Therefore, the film 2 before forming the tube 2' is also continuously fed.

A tube 2 is provided on the surface of the guide 11 and the folding plate 12.
In order to avoid undesirable wrinkles when forming folds on the tube, it is desirable to coat the tube with a low-friction material, such as a fluorine-based synthetic resin material, so that the tube can be fed smoothly.

A pair of auxiliary rollers 14 are provided at the lower end 7A of the nozzle 7 to assist the feed roller 13 and to bend the edge portion 2°A of the tube 2° so as to overlap the surface of the tube 2. A small roller (not shown) is provided on the side surface of the lower end 7A of the nozzle 7, and together with the auxiliary roller 14, the tube 2' is fed while sandwiching a 2° film therebetween.

A pinching roller 23 is arranged below the nozzle 7. The pinching roller 23 consists of a small roller 23A that directly presses the tube 2' and a backup roller 23B that applies back pressure and rotation to the small roller 23'. The pinching rollers 23 are as described above, and the direct pinching is performed by the small rollers, so that a step-like shoulder can be formed on the product, allowing a large amount of content to be filled into the product and a uniform appearance. . Furthermore, the drawback of large-diameter rollers (that is, unnecessary portions are pinched) is also eliminated.

A sealing device 24 and a cutting blade 25 as a cutting device are disposed below the pinching roller 23.

The cutting blade 25 is integrally assembled with the sealing device 24, and is attached to a reciprocating plate 20 which intermittently descends at the same speed as the film speed during the sealing operation cycle, and quickly returns to its original position and ascends. On the reciprocating disk 20, an ultrasonic horn 24A and an anvil 24B, which are close to each other during sealing, are arranged facing each other. Of the ultrasonic horn 24A and anvil 24B, a heating source (not shown) having a control device is disposed on the anvil 24B so that the anvil 24B is heated to a predetermined temperature. In this embodiment, the anvil 24B is heated, but the ultrasonic horn 24A is heated.
or both may be heated. The anvil 24B is formed as four protrusions whose tips extend in a direction perpendicular to the plane of the paper, and a cutting blade 25 is provided at an intermediate position between the four protrusions, that is, at a position where there are two protrusions in each direction in the film feeding direction. It is provided. The cutting blade 2
No. 5 is set so that the ultrasonic horn 24A and anvil 24B approach each other, press the film and weld it together, and then protrude to the cutting position.

In this embodiment, the vibration frequency of the ultrasonic horn 24A is as follows:
A desirable range is set to 20 KHz to 50 KHz, and is determined as appropriate within this range. In this example, the lower limit of this frequency (20 KHz) is a value necessary to ensure a sufficient seal, but the upper limit (50 KHz) is particularly important because higher frequencies only increase energy loss. This frequency is sufficient.

In addition, the melting point used in the test described below is 130 to 140 °C.
For a film with a sealing layer of
It is not necessary to raise the temperature to near C (160° C. or lower, for example, around 120° C., which was considered difficult with conventional devices), and sealing can be achieved sufficiently.

Generally speaking, the heating temperature of the heating element should be set so that the seal layer on the inner surface of the film is heated to a temperature above the softening point and below the melting point. The standard is preferably in the range of (melting point -60''C) to (melting point +30''C), more preferably (melting point -
30°C) to (melting point).

Next, the filling and packaging process in this embodiment having the above-mentioned configuration will be explained step by step with reference to FIG.

The film 2 drawn out from the original fabric 1 is shaped into a cylinder with an edge portion 2A by a forming plate 5, and then formed into a tube 2' by a welding device 6. This tube formation is as described above.

The contents to be filled are contained in the hopper 8 and are sent to the nozzle 7 by a pump 9. The contents are stored in the accumulator 10 through the nozzle 7, and are intermittently ejected by the piston device 10A to inject a fixed amount into the tube 2' from the lower end 7A of the nozzle 7. At this time, the sealing device 24 is in the sealing position and the lower end of the tube 2' is closed. In addition, the pinching roller 23
is in the retracted position and is not operating (squeezing).

Since the above-mentioned contents are filled while the tube is continuously fed, the reciprocating plate 20 also descends at the same speed as the feeding speed of the tube, and therefore the sealing device 24
It also descends while maintaining a seal. When the tube descends to a predetermined position, that is, when a predetermined amount of the contents is injected at once, the piston device 108 causes the piston of the accumulator 10 to retreat and transfers the contents continuously supplied by the pump 9 to the accumulator. Pull into lO.

Next, the tube into which the contents have been injected is sent downward while being pinched by the pinching rollers 23 to form a flat portion 2'B in which the contents are not present. Under such conditions, the sealing device 24 operates on the flat portion 2'B, and sealing is completed.

At this time, the flat portion 2°B is pressed between the ultrasonic horn 24A and the anvil 24B, receives ultrasonic waves, and is heated and sealed here. This sealing part is formed into a linear shape by the four protrusions of the anvil 24B, but the contents remaining in the flat part 2'B are removed from the cotton-like sealing part by ultrasonic waves, and the film is sealed. The inner surfaces are in direct contact and ultrasonically sealed. At this time, since the outer surface of the film that is in contact with the anvil 24B is heated, the above-mentioned sealing action is promoted and becomes extremely efficient and reliable. It should be noted that the number of seals does not need to be two in front and behind the cutting blade 25 as shown in the figure, but it is sufficient to have one seal in front and behind the cutting blade 25.

Immediately after the sealing, a cutting blade 25 protrudes and cuts the tube between the two upper and lower seal lines to obtain individual products as shown in FIG.

As mentioned above, the present invention has been explained based on the embodiments in the case of horizontally sealing a gazette package, but the present invention can also be used for vertical sealing instead of the vertical sealing hot plate 6B and the pressure roller 6C. Of course, it can also be used when welding an opening piece to the surface of a packaging film.

Next, the test results conducted in this example will be compared with the results of the conventional apparatus using specific numerical values.

Test conditions> ■ Film material The film forming the tube includes a polyolefin sealing layer (melting point: 130-140"C) on the inner surface, a barrier layer in the middle, and a strength layer (melting point: 230-240"C) on the outer surface.
) and a total thickness of about 70 μm was used.

■Test method Processed meat food is packaged with the film described in (■) above, a gusset package as shown in Figure 2 is made, the lower part of the package including the flat part is immersed in salt water in a test tank, and the tester is heated. A continuity test was performed by inserting one terminal into the saline solution and the other terminal into the package outside the saline solution. In the test, a product with a resistance of 30 OKΩ or more was judged to be a good seal product.

Note that the resistance of the contents inside the package in the resistance measuring circuit is less than IKΩ, which is negligibly small compared to the criterion of 300Ω.

<Test results> (A) Conventional example (heat seal only) As a result of sealing with a contact pressure of 1.8 kg/cm2 and a sealing time of 0.48 seconds, even if the sealing temperature was raised to 200°C,
The non-defective product rate was 73.3%.

CB) Conventional example (ultrasonic seal only) Contact pressure 1.8 kg/cm", vibration frequency 40 KHz, sealing time 0.19 seconds, resulting in an amplitude of 12.5
In terms of μm, the non-defective product rate was 76.6%.

(C) This example (ultrasonic and heat seal) contact pressure 1.8
kg/ctth", frequency 40K) lz', amplitude 12
．． As a result of sealing with 5 μm, the anvil temperature was 120″C.
In this case, a 100% non-defective product rate was obtained with a sealing time of 0.09 seconds.

Thus, according to the present invention, complete welding can be achieved in a very short time by applying ultrasonic waves while heating within a temperature range that does not have an excessive effect on the film.

〔Effect of the invention〕

In the present invention, as described above, welding is carried out using ultrasonic waves while heating, so ultrasonic welding is carried out by ensuring that the films are brought into direct contact with each other while removing the contents, if any, from the welding area using ultrasonic waves. , and at that time, we decided to use heating to promote the ultrasonic welding effect, so unlike conventional equipment (there is no need to increase the amplitude of the ultrasonic waves or raise the heating temperature), there is no need to increase the amplitude of the ultrasonic waves or raise the heating temperature, so there is no need to damage the film or There is no problem of adhesion to the heating element, welding can be performed more reliably and in a shorter time, and even when used in filling and packaging equipment, it can eliminate problems during work, improve quality, and further improve work efficiency. bring about.

[Brief explanation of drawings]

Fig. 1 shows a device according to an embodiment of the present invention, Fig. 1 (Δ) is a partially cutaway front view of the entire device, Fig. 1 (B) to E)
1A shows a sectional view taken along line B-B to E-E in FIG. 1(A), FIG. 2 is a perspective view of the product obtained by the device in FIG. FIG. 4A ・・・・・・・・・Ultrasonic horn 4B ・・・・・・Anvil

Claims (4)

[Claims] (1) A method for ultrasonic welding of synthetic resin films, which comprises heating an ultrasonic horn and/or an anvil in the method of ultrasonic welding of overlapping parts of synthetic resin films. (2) The method for ultrasonic welding of synthetic resin films according to claim (1), wherein the overlapping portion is a plurality of parts having different numbers of overlapping films. (3) The film is formed in a cylindrical shape, and after filling the cylindrical film with contents and locally compressing it from the outside to form a part without content, the part is subjected to ultrasonic waves. The method for ultrasonic welding of synthetic resin films according to claim 1 or claim 2, wherein the synthetic resin films are welded. (4) An apparatus for ultrasonic welding of overlapping parts of synthetic resin films, characterized in that the apparatus is equipped with a heating means for heating an ultrasonic horn and/or an anvil. Device.