FI70185C - FOERFARANDE OCH ANORDNING FOER BILDANDE AV EN FOERPACKNING I EN VAKUUMKAMMARE - Google Patents

Description

70185

Method and apparatus for forming a package in a vacuum chamber -

The present invention relates to a method and apparatus for forming a hermetically sealed package in a vacuum chamber, in particular by fusing layers of film material (which may themselves be bonded multilayer film structures) to seal the package. Such a package may, for example, be a vacuum package, but it might as well contain an inert gas which helps to preserve the contents of the package, especially when the contents are perishable.

Various methods of sealing membranes are known. Today, the following methods are widely used: galvanizing to seal the neck of a film bag, heat sealing while applying heat and pressure to press the two film layers into one fusible contact, and an adhesive seal, e.g. by coating one or both surfaces that come into contact so as to seal them together; close when compressed.

In addition to heat sealing, in which the films are compressed together using mechanical pressing rods, it is also known from U.S. Patents 3,989,778 and 4,069,080 to irradiate the compressed film layers with laser energy to promote local melting of the surfaces in contact with each other. It is also known from U.S. Pat. Nos. 3,477,194 and 3,247,041 to irradiate compressed film layers with infrared radiation from a nearby source to bond the layers together.

All these known publications rely on the use of heat in membrane parts which have already been compressed together in such a way that the use of such a system requires precise coordination of the compressed membrane parts with the path of energy radiation from an infrared source or laser. In addition, especially when using infrared radiation, it is difficult to avoid gaps between the infrared source (s) and the compressed membrane parts (to allow sufficient space for handling the packaged product and surrounding material) which are so large that the radiation losses, which vary inversely to the square of the distance to the heat source, become considerable.

It is an object of the present invention to provide a method and apparatus for avoiding the above-mentioned disadvantages of known systems for enclosing a radiant thermoplastic material.

The invention therefore relates to a method of forming a package in a vacuum chamber, in which the article to be packaged is placed in a plastic film bag, the bag neck is kept inflated due to the mouth of the bag neck being flexibly contracted while the pressure in the chamber is reduced outside the bag, and the bag is heated by heating means. the pressure difference between the inside of the pouch and the outer side reaches the value at which the bag neck holding device is flexible through allowing the gas outlet mouth of the bag and the method according to the invention is characterized in that the bag neck is bulging neck spaced apart portions are heated by infrared radiation sources, which are located close to the bulging of the bag neck without touching it, and that the bulging neck of the bag is then broken to remove gas from the bag and the neck portions are brought into contact with each other to close the neck when the neck portions engage each other. due to.

The invention also relates to an apparatus for forming a package in a work carrier comprising a base for goods placed in a bag made of plastic film, means for keeping the neck of the bag bulged, means for shrinking the neck of the bag and means for heating the bulging bag on the base while the shrinkage means 70185 3 for sealing a package, characterized in that at least one infrared radiation source is placed in the vacuum chamber close to the neck of the bulging bag without touching it, for irradiating and heating opposite parts of the neck, and that the means for contacting opposite parts of the bag neck with each other comprise inside the bag to reverse the bulging of the neck after heating with an infrared source, as a result of which the heated neck material i comes into contact with itself and closes as a result of the contact.

In order that the present invention may be more readily understood, the following description is given by way of example only with reference to the accompanying drawings, in which: Figure 1 is a schematic side sectional view of a form of vacuum chamber in which the method of the present invention may be practiced; Figure 7A is a detailed sectional view of the chamber of Figure 1; Fig. 2B is an end sectional view of the closure mechanism of Fig. 2A, Fig. 3 is a schematic top plan view of an alternative form of vacuum chamber in which the method of the present invention may be implemented, Fig. 4 is a view similar to Fig. 3 showing another embodiment of the vacuum chamber in which the method may be implemented, and Fig. 5 -4 Wiring diagram of the simple form of the control system of the infrared heat sources used.

Figure 1 shows a vacuum chamber 1 comprising a base part 2 and a lid 3 closed together and sealed along their edges 20 so as to form a closed space in which two plastic bags 4 (in this case made of heat-shrinkable material) containing products 21 can be evacuated and close.

The heat of shrinkage is applied to each bag 4 by means of two fans 6 and 7 driven by respective motors 8 and 9 and circulating air through circular heating elements 10 and 11, shown in side view in Figure 1 and identical to those shown in plan views in Figures 3 and 4, with the respective heating elements 10 and 11. A radially outwardly directed air stream from the centrifugal fan motors flows over the heating elements 10 and 11, heats them and then contacts the bags 4 over the chamber support grid 12. The bags then receive heat from the air and shrink to the desired extent depending on the degree to which the film is oriented during manufacture.

The chamber further includes top and bottom heating units 13 and 14 including infrared heat radiating lamps (37 and 38 in Figure 2A) which radiate heat to separate membrane portions of the neck areas of the bags 4 and heat the neck areas sufficiently so that when these membrane the parts later contact each other, e.g. during the repressurization of the chamber 1, the film layers automatically merge together.

The detailed structure of these upper and lower heating units 13 and 14 will be explained with reference to the detailed drawings of Figs. 2A and 2B.

The mouth area of each bag is compressed by a flexible bag holding device having upper and lower members 33 and 35, also shown in Figures 2A and 2B, so that air can escape from the interior of the bag 4 through the upper and lower heating units 13 and 14 and the upper and lower heating units. between the lower members 33 and 35, but due to the flexible bag holding effect, air cannot return to the bag through the mouth area.

The evacuation cycle used in the chamber of Figure 1 can take several different forms.

As a first example, the heating heat can be applied to the bag 4 by activating the fan motors 8 and 9 and the heaters 10 and 11 before evacuating the chamber 1. This results in heat shrinkage of the bag material. This heat shrinkage tends to compress the air trapped between the product 21 and the bag 4, which keeps the bag "bulged" and separate from the relatively cold product as tension develops in the hot shrinkable bag 4.

The air trapped in the bag 4 is then released when the pressure overcomes the flexible blade 33, whereby the shrinkage energy retained in the tight bag can force the bag material onto the product 21. The vacuum pump is then started and the evacuation of chamber 1 takes place. After a suitable delay, the shape conductor 48 is energized, whereby the neck of the bag is broken, which allows the bag to be further evacuated through the neck. The evacuation of the chamber is continued to remove the remaining air from inside the bag 4 and to close the 6 70185 bag. Such a cycle is described in Figures 2A and 2B and in any case in GB patent application 8108437.

An alternative operating cycle of the chamber 1 is one in which the evacuation of the chamber 1 begins simultaneously with the activation of the heaters 10 and 11 and the fan motors 8 and 9 and continues so that compression of the bag mouth by flexible bag holding means delays air removal from inside the bag 4. As a result, the bag 4 bulges outwards out of the product 21 when the chamber pressure around the bag 4 decreases faster than the air pressure in the bag 4. When the bag has bulged to the desired extent (either by using a cycle timer based on the same membrane packed in the same chamber). the bulging of the batch of products subject to evacuation lasts for the same time, or by using mechanical sensors responsive to the bulging bag 4), the evacuation of the chamber ceases so that the bag is kept bulged during the circulation of the remaining air in the chamber 1 by the fan rotors 6 and 7. This circulation of hot air further causes heat transfer to the material of the bag 4, whereby the shrinkage energy of the bag 4 is recovered, as the bag is still kept separate from the product 21. When this heating of the bag 4 has progressed far enough, the chamber evacuation begins again. , when the inside of the bag has reached a sufficiently low residual pressure (high vacuum). Such a method is described in GB patent application 8023465.

Other operating cycles are possible, for example a cycle in which evacuation and hot air recirculation take place simultaneously and continue uninterrupted until a sufficiently low residual pressure (high vacuum) is reached, after which the bag is closed.

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In connection with all the above-mentioned operating cycles, the chamber of Fig. 1 preferably comprises the upper and lower heating units 13 and 14 shown in Figs. 2A and 2B.

As shown in Fig. 2A, the flexible bag holding device 30 is supported by the upper support member 31 forming the lid portion of the chamber 3 and the lower support member 32 of the lower chamber portion 2. As the lid 3 closes on the lower chamber 2, the upper support member 31 descends towards the lower support member 32, conforming to the shape shown in Fig. 2A.

A flexible bag holding blade 33, suitably made of fibrous material, is supported by an upper support member 31 to which it is secured by a set of screws 34. The resilient blade 33 contacts its lower edge along a counter member 35 supported by the lower support member 32. The counter member may alternatively be a blade 33. When the chamber lid 3 is in the raised position, lowering the chamber lid 3 to bring the upper and lower support members 31 and 32 to the position shown in Fig. 2A automatically causes the bag neck to remain with the counter member 35 so that any differential air pressure in the bag above a certain value can be removed by moving the blade 33.

The pulling of the neck of the bag to the left between the blade 33 and the counter member 35 is resisted by spring-loaded pushers, one of which 36 is shown in Figure 2A, which press the neck of the bag tightly over the counter member 35.

The angle of inclination of the flexible blade 33 is such that air under sufficient differential pressure can escape from inside the bag at least in the mouth areas between successive pushers 36.

The closure of the neck of the bag so as to create as little air space around the neck as possible in the bag is provided by upper and lower heat sources 37 and 38, which are strip lamps emitting infrared heat at a wavelength which results in an optimal mixture of plastic bags. heat absorption.

The wavelength of the light emitted by the lamps 37 and 38 is preferably selected to be the same as the wavelength most easily absorbed by the material of the bag. Suitably, this wavelength is 3-4 microns for most plastic films, including multilayer films and laminates such as heat shrinkable (i.e., oriented), three-layer ethylene vinyl acetate, polyvinylidene chloride, and irradiated ethylene vinyl acetate acetate.

A brief exposure of the neck area of the bag to radiation from the heat radiators 37 and 38 is sufficient to heat the bag material to its softening point so that when the bag material sheets are compressed together, they close in the mouth and neck areas.

Contact between the bag material and the upper and lower heat sources 37 and 38 is prevented by means of batten nets 39 and 40 supported by respective pairs of upper and lower support plates 41 and 42 pivotally mounted on pins 41a, 42a. Each support plate 41, 42 has a hole 41b, 42b slidably cooperating with respective cam pins 43 and 44 supported on the respective ends of the vertically movable upper and lower pressing bars 45 and 46, respectively. The lower compression rod 46 includes a main body with a resiliently flexible jaw member 46a connected thereto by helical compression springs 46b which ensure that the two compression rods 45 and 46 contact each other as the jaw member 46a springs.

The holding device 30 further includes a shape conductor 48 supported by a counter member 35 which, in the form of Figure 2A of the holding device, contacts the bulging neck of the bag. When a current pulse is applied to the conductor, the conductor breaks the neck of the bag so that gas (usually air) can escape from the bulging neck before closing. The conductor 48 may have, for example, a sawtooth shape or a sinusoidal wavy shape.

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As the upper compression bar 45 descends, its cam pins 43 slide down in the holes 41b and cause the upper pivotable support members 41 to rotate counterclockwise to pivot the heat source 37 and its batt net 39 to the right of the trajectory of the lowering upper compression bar 45.

Likewise, as the lower compression bar 46 rises, its cam pins 44 cooperate with the holes 42b of the lower brackets 42 to pivot these brackets to the side and move the lower heat source 38 and its batt net 40 away from the trajectory of the rising compression bar 46. This allows the film material to be pressed between the two press bars 45 and 46. At the same time, the blade 47 supported by the main body portion of the lower compression rod 46 is positioned above the resilient jaw 46a by the resilience of the compression springs 46b and can cut excess bag material from the neck during closure.

Fig. 2B shows a drive mechanism by which the upper pressing member 45 is operated during its vertical movement.

As shown in Fig. 2B, the upper pressing member 45 rests in two separate parts on a vertical guide pin 50 supported by the central bearing portion 49, so that the two parts of the upper pressing rod 45 can slide vertically.

The two compression rod parts are connected to the lower ends of the respective push joints 51, the upper ends of the joints of which in turn are articulated to the respective double-angle lever units 52, 52 ', one of which 52 is shown in Fig. 2A.

To the left of the angle levers 52 is a fixed pivot pin 53 at the first corner, a pivot pin 54 at the second corner that articulates it to the push joint 51, and an additional pivot pin 55 at the third corner that articulates it to the other end of the second drive bracket 56.

At 57, the other end of the second drive bracket 56 is articulated to the corresponding angle of the right-hand corner lever unit 52 '.

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The lever unit 52 also has pivot pins 53 'and 54' corresponding to the pins 53 and 54 described above.

The first drive bracket 58 is connected between the piston rod 59 of the piston 60 and the additional pivot pin 61 of the right angle lever unit 52 '. The extension and retraction of the piston rod 59 causes the counterclockwise and clockwise movement of the angle lever units 52, 52 ', respectively, and thus the upward and downward movement of the compression rods 45.

A similar drive joint and drive piston exist for down-pressing to move the main body of the rod 46 up and down.

As also shown in Fig. 2B, a protective member 62 is screwed onto the upper compression rod 45 so as to form a gap in which the blade 47 can fall when the upper and lower compression rods 45 and 46 come together.

The holding devices of Figures 2A and 2B operate in several stages throughout the machine cycle, as will be explained later.

The operation of the device shown in Fig. 1 is as follows when bags 4 formed of heat-shrinkable or oriented film material are used.

A filled, but unsealed, bag 4 made of heat-shrinkable packaging film is placed in the vacuum chamber 1, and the chamber lid 3 is moved downwards to close the chamber and allow the chamber to be sealed at its edge 20.

One form of hot shrinkable (i.e., oriented) film used for the bag 4 may be a three-layer ethylene-vinyl acetate, polyvinylidene chloride, and irradiated ethylene-vinyl acetate laminate disclosed in U.S. Patent 3,741,253 and sold under the trademark "Bar. W.R. Grace & Co."

During this time, the heat sources 37 and 38 are either de-energized or, more preferably, energized to a low heating level that does not allow them to heat the bag neck membrane to a sufficient melting temperature.

The compression of the mouth of the bag when touched by the flexible holding device 30 ensures that any excess pressure erc that may develop in the bag as convection is applied to the outside of the bag can be adjusted by removing gas (usually air) from inside the bag 4 to the extent that the bag remains "bulged". "separately from the surface of the product 21 contained therein. Since bulging depends on factors common to a particular batch of products 21 (e.g., surface temperature, amount of air contained in the product, and surface quality of the product, e.g., tack), it may be appropriate to observe when bulging is likely to occur and then schedule the process so that evacuation begins simultaneously for all products in the batch. This is timed by a suitable timer. Other control devices can also be used as required.

Because the bag is still held flexibly over its neck during the heat-shrinking phase, air can still escape from inside the bag through the neck if, albeit unlikely, an excessive pressure difference develops over the bag material. The rest of the bag, on the other hand, shrinks back to the surface of the product 21 to give a substantially wrinkle-free surface covering the product 21, but still the neck of the bag can close when the compression rods 45 and 46 close in contact with each other.

At the end of the bubbling step and before the evacuation of the bag begins, energy is briefly applied to the shape conductor 46 to break the neck of the bag and release the remaining gas.

Evacuation of the chamber atmosphere (and now the broken bag 4) continues until the desired vacuum level is reached. During or shortly before the evacuation phase, the lamps 37, 38 12 12011 85 can be energized to their maximum level so that they radiate radiant heat at the desired wavelength so that the film material optimally absorbs heat and the neck of the perforated bag is thus heated to the melting temperature.

The pistons 60 are then actuated to bring the upper and lower compression rods 45 and 46 together, thereby simultaneously pivoting away from the sources 37 and 38 and the associated tongue nets 39 and 40.

After the upper pressing bar 45 has come into contact with the bent pressing jaw 46a, the continued operation of the pistons 60 results in the blade 47 cutting the neck of the bag to remove excess fluid therefrom. The pressing members 45 and 46 ensure that the neck remains firmly next to the blade 47 to effect closure. Throughout this step, the mouth portion of the bag is further compressed between the resilient blade 33 and the counter member 35 so that the bag is still securely located within the holding device 30.

Retraction of the upper and lower compression rods 45 and 46 restores the heat sources 37 and 38 and their batten nets 39 and 40 to the formation of Figure 2A. The evacuation of the chamber takes place after this retraction of the compression rods 45, 46, so that any residual air can escape from the bag without hindrance.

When the vacuum chamber is re-pressurized when opened, the heated neck portions on the left side of the compression members 45 and 46 are pushed together to provide fusion welding and to reduce any excess around the sealing zone so that the final package has a neat appearance.

The excess bag material removed by the blade 47 still remains between the flexible blade 33 and the counter member 35 and can be removed from the chamber opened during or after removal of the package.

70185

The method described above is particularly suitable for use with moist products such as fresh meat in hot shrinkable bags because the increase in pressure on the surface of the meat during the bag bulging step tends to retain moisture in the product and prevent the inner surface of the bag from spraying when the bag is bulged. In addition, due to the rapid removal of air trapped in the bag, after the bag is punctured, the bag material can quickly contact the product before such spraying occurs. The appearance of the finished package is therefore particularly neat in the case of moist products such as fresh meat.

When all products are packaged by this method, the wrinkling of the product is improved by using a pre-shrinkage step followed by evacuation (in contrast to the conventional order of first vacuum sealing and later shrinkage).

In addition, the finished package of the present invention is much better than known shrink-cleaned packages using a water shrink bath to mitigate the "heat sink" effects of a relatively cool and high heat capacity product because shrinkage of the film upon contact with air allows for greater shrinkage energy recovery. As a result, the sealing properties of the bag (which are important to maintain the hermetic seal and freshness of the product until the time of use) are more effective. In addition, such a bag is more resistant to improper handling due to its greater thickness.

Since the air pocket left in the bag during the preheating shrinkage phase resists the bag collapsing and delays the contact between the bag and the cold product, this thickness-increasing effect is even more pronounced and the wrinkle-free appearance of the bag depends on the latent shrinkage energy recovery. In addition to shrinkage (14 701 85 promotes airflows around the entire product / the bag shrinks evenly around the product # which eliminates the risk of air pockets behind the product "equator" (i.e. behind the area with the largest cross section perpendicular to the longitudinal axis of the bag) .

In addition, the fact that there is little or no water vapor in the air between the product and the shrinkable bag (caused by starting the shrinkage before the pressure drops, which even causes a small pressure rise) ensures that less shrinking heat is needed because the dry air inside the bag absorbs less air containing heat rather than moisture.

Since the lower and upper support members 32 and 31 of the flexible holding device 30 are supported in the lower chamber part 2 and the upper chamber part 3, respectively, they close automatically in contact with each other when the chamber is closed. The only thing the operator needs to do is make sure that the neck of each bag 4 is placed on the respective counter members 35 before the chamber closes.

When the conveyor feeds the filled bags into the chamber 1, the conveyor may, if desired, be such as to ensure that when the bag 4 stops, the neck of the bag is correctly positioned for compression without the operator having to carefully position it.

As stated above, the second bag sealing mechanism strips can be used with the radiation heat sealing units 13 and 14 described above.

For example, the neck of the bag can be closed with a conventional leveling bar 70 (Figure 3), which both cuts off excess and closes the bag mouth along the line of compression between the upper and lower compression bars (by means of resistance heaters).

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When heat is applied to the neck area between the leveling barrier unit 70 and the product 21, when the chamber 1 is pressurized again, the substance in the neck area of the bag is heated to such an extent that it fuses when compressed, leaving a much cleaner neck area in the package.

Alternatively, the neck of the bag may be placed in the assembly unit 71 (Figure 4) so that it is assembled in a vacuum chamber as the chamber closes. The galvanizing unit 71 attaches a bracket to the neck of the bag when the evacuation and shrinking steps are completed. Such an in-chamber galvanizing device is disclosed, for example, in GB Patent 1,353,157.

Yet another possibility is to omit the galvanizing unit 71a from Fig. 4 and perform the assembling step after the current of the infrared heat sources has caused the bag neck to be heated in the area to be assembled. When the neck areas of the bag thus heated and softened are pulled together by means of a collecting unit 71 (which may, for example, be of the type described in GB 1 353 157, 1 361 142 and 1 496 740), the assembling effect is sufficient to cause the neck to adhere to itself and resemble galvanized neck shape without bracket. The mere thermal softening of the neck area of the bag is sufficient to cause close contact and closure of the assembled neck area.

For example, the schematically shown assembly unit 71 may operate in two steps, as disclosed in GB 1 353 157, so as to first assemble the bag into a horizontal slit when the chamber closes and provide sufficient gas flow restriction from inside the bag to promote the desired bulge effect before infrared sources flow. The second assembly step then reduces the length of that gap to collect the neck of the bag into a self-adhesive assembled shape. Alternatively, the bag may be subjected to some other contraction effect of the mouth of the bag, after which the collecting unit 71 is used so as to completely assemble the neck of the bag after the bulging heating step.

In connection with the chamber of Figure 1, the above description of possible different operating cycles relates to the use of a heat-shrinkable film throughout. However, the method according to the invention can be used in connection with other films, for example in connection with self-welding films, which are thermally softened, after which they weld when they come into contact with each other.

Likewise, the alternative chamber structures shown in Figures 3 and 4 can be used with any suitable film, including heat shrink films and self-welding films.

Fig. 5 shows a schematic diagram of a possible switching circuit for supplying current to the radiant heat radiating lamps 37 and 38. The control transformer 72 is connected across the input terminals 73 and 74. Also connected over the same terminals 73 and 74 is a side power line including a microswitch 75 and a timer 76. The second side power line includes a switch 77 and a circuit breaker 78 which is itself connected to switch contacts 79 and 80 in the secondary circuit of the control transformer 72. The two switch contacts 79 and 80 thus control the supply of current to the infrared radiation lamps 37 and 38, which are connected in parallel to the secondary circuit of the control transformer 72.

The control transformer is permanently energized, and the beginning of the cycle is triggered by the operation of a microswitch 75, which microswitch reacts to a moving mechanical component, e.g. to the closing of the chamber lid 3. Closing the microswitch 75 initiates a timer timing cycle so that the switch 77 closes immediately, energizing the circuit breaker 78, which closes the contacts 79 and 80 to supply power to the lamps 37 and 38.

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After a time delay determined by the timer 76, the switch 77 opens, disconnecting the circuit breaker 78, which then opens the contacts 79 and 80 to stop supplying power to the lamps 37 and 38.

In a particularly suitable variation of the circuit of Figure 5, arrangements may be made so that the wattage of the lamps is reduced to backup power (e.g., to 20% of their full wattage) instead of the power supply being completely stopped when the circuit breaker 78 is de-energized. This can be accomplished, for example, by using a two-way switch system at contacts 79 and 80 so that a "backup circuit" is provided in the second position of the movable contacts to energize the lamps 37 and 38 in their backup power setting, and the main circuit shown in Figure 5 can be energized.

By adjusting the control transformer 72, the wattage of the lamps can be varied. The timer 76 may also be adjustable to allow a time delay, e.g. 2-6 seconds, for the operation of the lamps 37 and 38.

One preferred lamp type to be used as lamps 37 and 38 is a Philips type 13195 X / 98 lamp sold by Philips Electrical Company.

An advantage of the defrost barrier system described and illustrated herein is that the thermal inertia of the infrared lamps 37 and 38 is so small that they can be ignited only when a defrost barrier is required. In addition, the melt barrier has the advantage that there is no physical contact between the heat supply lamps and the plastic material to be attached.

A particularly important advantage of the present invention is that heat is applied to the films by radiation before they come into contact with each other, which ensures that the shortest possible path of radiant energy can be obtained in the films compressed from the lamps without having to place the lamps 37 and 38 close together. Conversely, the lamps may be located quite far apart and the neck of the bag may bulge in the vicinity of the lamps to shorten the distance from the heat source to the bag material. This provides a much simpler device in terms of (a) feeding the bag into the chamber, or (b) more generally (when melt sealing the film wrapper to form a package without using a vacuum chamber) placing the two film parts to be welded in a position ready for melt heating with the device of the invention.

In addition, the amount of energy supplied to the membranes can be quickly and easily adjusted either by changing the voltage supplied to the lamps or by varying the time they are "on", or by adjusting both parameters.

If desired, the neck area of the bag can be printed with a material with a high absorption coefficient, so that an even stronger local heat absorption is obtained.

The vacuum levels used in the methods described above can be on the order of 5 torr. However, the vacuum can be much softer (higher residual pressure) if necessary (e.g. when packing products such as high-gas-emitting cheeses that naturally emit gas - e.g. carbon dioxide - and do much more if packaged under high vacuum conditions).

In Figures 1, 3 and 4, the means for applying heat to the bag material are hot air circulating fans. Alternatively, other bag heating devices may be used in conjunction with the radiant heat radiating heating units 13 and 14.

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Temperatures of 90-140 ° C are required in the bulged film to achieve hot shrinkage of the biaxially oriented shrink film. However, the radiant heat radiating heating units 13 and 14 may apply higher temperatures in the neck region of the film to promote melt sealing.

The above description relates generally to the effect on one bag in the chamber, although it is quite clear that two separate bags 4 are used in Figure 1. The method and apparatus of the invention can be used in one package or in two or more simultaneously sealed packages. This applies in the same way to the three different embodiments shown in Figures 1, 3 and 4 as to any of the other embodiments within the scope of the claims.

Claims (12)

701 85 20 A method of forming a package in a vacuum chamber, wherein the article to be packaged is placed in a plastic film bag (4), the neck of the bag is kept inflated by keeping the mouth of the bag flexibly contracted while reducing the pressure outside the bag, and the bag is heated by heating means ( 6, 7, 8, 9, 10, 11), until reaching the differential pressure of the bag between the inner side and outer side of the equality, wherein the bag neck holding device (30) is flexible through allowing the gas outlet mouth of the bag, characterized in that the bag (4) of the neck of the bulging portions of the neck are heated by infrared radiation from sources (13, 14) located near the neck of the bulging bag without touching it, and that the bulging neck of the bag is then broken to remove gas from the bag (4) and the neck portions are contacted to close the neck due to contact with each other. Method according to Claim 1, characterized in that the bulging of the bag is effected by heat-shrinking the bag material when the neck of the bag is kept compressed. A method according to claim 1 or 2, characterized in that the film material is a multilayer film comprising at least one ethylene vinyl acetate layer, a polyvinylidene chloride layer and an irradiated ethylene vinyl acetate layer, and that the wavelength of the infrared radiation is 3-4 microns. An apparatus for forming a package in a vacuum chamber (2, 3) comprising a base (5) for goods placed in a bag (4) of plastic film, means for keeping the neck of the bag bulged, said means (30) for constricting the neck of the bag (4) and means (6) 8, 10) and (7, 9, 11) for heating the bulging bag on the base (5) as it is constricted by the constriction means (30), and means for contacting opposite parts of the neck of the bag with each other to close the package, characterized in that the vacuum chamber (2) , 3) at least one infrared radiation source (13, 14) is placed close to the neck of the bulging bag without touching it, for irradiating and heating opposite parts of the neck, and that means for contacting opposite parts of the neck of the bag comprise means (48) for passing gas to the bag (4) from the inside to heat up the bulge of the neck with an infrared radiation source (13, 14) as a result of which the heated neck material comes into contact with itself and closes upon contact. Device according to claim 4, characterized in that the means for bringing opposite parts of the neck of the bag (4) into contact with each other comprise a bag neck assembly unit (71) adapted to compress the neck of the bag by assembling it to provide a closure, and programmed to assemble the bag neck after energizing the means (13, 14) emitting infrared radiation. Device according to claim 4 or 5, characterized in that the means for contacting opposite parts of the neck of the bag with each other comprise: (a) means (48) for breaking the neck of the bulging bag and (b) cooperating holding jaws (45, 46a) which are placed adjacent the bag neck breaking means (48) on the side of said breaking means (48) located closer to the bag base (5) for squeezing the bag neck for resealing after gas has escaped through the broken neck portion. Device according to one of Claims 4 to 6, characterized in that the means for emitting infrared radiation comprise a pair of strip lamps (13, 14) arranged side by side on each side of the intended location of the bulging neck of the bag (4), and that the bag (4) the neck constriction means comprise a pair of parallel press bars (33, 35) 22 70185 arranged adjacent to the space between the strip lamps (13, 14) and capable of squeezing the bag (4) between the necks. Device according to Claim 7, characterized in that at least one (33) of the pressing rods can be flexible during its pressing operation, so that gas can escape from the bag (4) if an excessive pressure difference occurs over the film material of the bag. Device according to claims 6 and 8, characterized in that the holding jaws (45, 46a) move towards and away from each other along the operating path, and that the strip lamps (13, 14) are mounted to move in the operating position in which they are located along the trajectory between the spaced apart positions of the holding jaws (45, 46a) and between the inactive position where they are spaced apart from the trajectory so that the holding jaws can close together. The device according to claim 9, further characterized by nets (39, 40) associated with the strip lamps, which prevent the strip lamps (13, 14) from physically coming into contact with the bulging neck of the bag during heating. Device according to one of Claims 7 to 10, characterized in that it comprises means for energizing the strip lamps (13, 14) in a first level in which they emit infrared radiation with an intensity sufficient to heat the neck of the bulging bag and in a second level in which they operate extensively. with lower power consumption in standby mode. Device according to one of Claims 7 to 11, characterized in that it comprises a timer (75) for timing the time of infrared radiation from the strip lamps (13, 14) and means (72) for adjusting the intensity with which they emit infrared radiation heating the bag. 23,701 85