DK154882B - PROCEDURE AND APPARATUS FOR CREATING A SEALED PACKAGING IN A VACUUM ROOM - Google Patents

Description

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The present invention relates to a method of forming a sealed package and of the kind set forth in the preamble of claim 1.

Such packaging, for example, may be a vacuum pack, but may also contain an inert gas which helps to preserve the contents of the packaging, especially when the contents are perishable.

Various methods for sealing foils are known. Commonly used are currently: staple 10 for sealing the neck of a bag formed of the foil material, heat sealing by simultaneously applying heat and pressure to compress two layers of the foil together for melt contact and adhesive sealing, for example, by coating one or both of the surfaces to be contacted for sealing with one another with an adhesive composition such that their contacting surfaces are sealed when pressed together.

In addition to heat sealing by compressing foils using heated mechanical tension rods, it is also known from US Patents Nos. 3,989,778 and 4,069,080 to irradiate clamped layers of foil with energy from a laser to induce localized melting of the contacted ones. with adjacent surfaces. It is also known from United States Patent Nos. 3,477,194 25 and 3,247,041 to irradiate compacted film layers of infrared radiation from a nearby source in order to adhere them to one another.

These patents are all based on the application of heat to portions of the foils which are already clamped in the sealing position, so that the use of such a system requires that the clamped foil portions be carefully laid out on the path of transmitting energy from either the infrared source or the laser. Furthermore, especially with regard to the use of infrared radiation, it is difficult to provide ample space for handling

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2 of the packaged product and the surrounding material to avoid having distances between the source or sources of infrared radiation and the clamped foil portions so large that the radiation losses that change proportionally to the square of the distance from the heat source become significant.

The object of the invention is, by a method such as the one mentioned initially, to provide ample space for the position of the bag in the vacuum chamber and at the same time to minimize the distances between the source or sources of infrared radiation and the portions of the foil material to be irradiated. , so that the radiation losses become small.

This object is achieved by the characterizing part of claim 1.

By while the bag neck is disposed to heat the separate portions of the bag neck from infrared radiation from sources located in close proximity to the played bag neck without touching it, maximal utilization of the ΛΛ infrared radiation energy emitted from the sources to heat the bag material is obtained. , while the other measures specified in the claim serve for the intended sealing of the pouch neck, the portions of which are played out collapse and heat sealed by mutual contact.

Further preferred measures and features of the method of the invention are set forth in claims 2 and 3.

The invention also relates to an apparatus for forming a sealed package and of the kind specified in the preamble of claim 4, which apparatus is peculiar to the characterizing part of the claim.

Preferred embodiments and features of the apparatus of the invention are set forth in claims 5 to 12.

The invention will now be described in more detail with reference to the drawing, in which FIG. 1 is a schematic sectional side view of a form of a vacuum chamber in which the method of the present invention may be practiced; 3

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FIG. 2A shows in section a detail of the sealing mechanism included in the embodiment of FIG. 1; FIG. 2B, the one in FIG. 2A is an end view of the sealing mechanism; FIG. Figure 3 is a schematic top view of an alternative form of a vacuum chamber in which the method of the present invention may be practiced; 4 corresponding to FIG. 3 shows yet another embodiment of a vacuum chamber in which the method can be practiced; and FIG. 5 is a circuit diagram of a simple form of control system for the devices of FIG. 1 to 4 infrared heat sources used.

In FIG. 1, there is shown a vacuum chamber 1 comprising a bottom portion 2 and a cover 3 which are sealed together and sealed along their edges 20 to form a sealed enclosure within which plastic bags 4 (in this case made of heat-shrinkable material) enclose commodities 21 can be evacuated and sealed.

Shrinkage heat is supplied to each bag 4 by means of two fans 6 and 7 driven by motor 8 and 9 respectively and circulating hot air by means of circular heating elements 10 and 11, which, while shown from the side in FIG. 1 is identical to the configuration of the corresponding heating elements 10 and 11 shown from above in FIG. 3 and 4. The radially outward air flow from the centrifugal blower rotors 6 and 7 passes over the heating elements 10 and 11, thereby being heated and then coming into contact with the bags 4 over a support grid 30 5 in the chamber. The bags absorb heat from the air and shrink to the desired extent depending on the extent,. wherein the foil has been oriented during fabrication.

The chamber further comprises an upper and lower heat units 13 and 14 comprising infrared heat emitting 35 strip lamps (37 and 38 in Fig. 2A) which radiate heat to the separated foil portions of the neck regions of the bags 4 and heat the neck regions to a sufficient extent so that the foil layers when these foil portions i

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the subsequent contact, for example, during the reconstruction of pressure in the chamber 1, automatically merges.

The construction of these upper and lower heating units 5 13 and 14 will be described in more detail later in connection with FIG. 2A and 2B.

The mouth area of each bag is clamped by a resilient bag head member 30 with upper and lower members 33 and 35, also shown in FIG. 2A and 2B, 10 in such a way that the air is able to escape from the interior of the bag 4 between the upper and lower heating units 13 and 14 and the upper and lower elements 33 and 35,. but due to the resilient bag holding effect, the air is unable to penetrate bag 15 again through the orifice area.

The evacuation cycle used in the FIG. 1 can take one of a number of different forms.

As a first example, it is possible that the shrink heat is 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 will cause shrinkage of the bag material. This heat shrinkage seeks to compress the air trapped between the product 21 and the bag 4, and the trapped air 25 keeps the bag "flushed" out of contact with the relatively cold product while the tensile stress of the heat shrinking bag 4 builds up. .

The air enclosed in the bag 4 is then released as its pressure overcomes the elastic blade 30 33, allowing the shrinkage energy trapped in the tight bag to 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, a trapped wire 48 is activated, piercing the bag neck 35 and allowing further evacuation of the bag through the neck.

The chamber 1 is still evacuated to extract the remaining air from the interior of the bag 4 and allow the bag to be sealed. Such a cycle is described in compound 5

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with FIG. 2A and 2B and are at least mentioned in the applicants' Danish Patent No. ........ (application no. 5093/81).

In an alternative operating cycle for the device shown in FIG. 1, the evacuation of the chamber 1 starts simultaneously with the activation of the heaters 10 and 11 and the fan motors 8 and 9 οή progressing in such a way that the narrowing of the bag mouth at the elastic bag holding means causes delayed suction of air from the interior of the bag 4 This causes the bag 4 to be dispensed away from the product 21 as the pressure in the chamber drops faster than the pressure inside the bag 4. Once the bag has been played out to the desired extent (which can be detected either by having a time management which is based on on the fact that a portion of the same product-15 products packaged in the same foil and subjected to chamber evacuation at the same rate will use the same time for flushing, or as detected by mechanical sensors responding to a spout bag 4), evacuation ceases of the chamber so that the discharged state of the bag is maintained while circulating the remaining air in the chamber 1 by means of the fan rotors 6 and 7. This circulation On warm air, further heat transfer to the material of the bag 4 results in the recovery of the shrinkage energy in the bag 4 because the bag is still kept out of contact with the product product 21 therein. Once this heating of the bag 4 is advanced to a desired degree, the evacuation of the chamber is resumed and then the bag neck is finally sealed once the interior 30 of the bag has reached a sufficiently low residual pressure (high vacuum). Such a process is disclosed in British Patent Application No. 8023465.

Other possible operating cycles may arise, in which, for example, the evacuation and hot air circulation 35 begin simultaneously and continue uninterrupted until a sufficiently low residual pressure (high vacuum) has occurred and the bag is then sealed.

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For each of the aforementioned forms of operation cycle, the chamber preferably comprises the ones in FIG. 2A and 2B show upper and lower heating units 13 and 14.

As shown in FIG. 2A, the resilient bag-holding 5 members 30. are supported by an upper support member 31 which forms part of the chamber cover 3 and a lower support member 32 which is part of the lower chamber portion 2. When the cover 3 is closed on the lower chamber portion 2 , the upper support member 31 moves downwardly against the lower support member 32 to assume the position shown in FIG. 2A.

An elastic bag-holding blade 33 of a suitable rubber-like material is supported by the upper support member 31 and is secured thereto by a set of screws 34.

Along its lower edge, the elastic blade 33 touches a counter member 35 carried by the lower support member 32. Alternatively, the counter member may be a blade similar to the blade 33. After the neck of a plastic bag is placed on the counter member 35, while chamber-20 the cover 3 was in the raised position, lowering the chamber cover 3 to bring the upper and lower support members 31 and 32 to the one shown in FIG. 2A, the bag neck automatically shown to be retained on the counter member 35 so that any build-up of air pressure difference within the bag over a certain value can be vented by moving the blade 33. Retraction of the bag neck to the left between the blade 33 and the counter member 35 is counteracted by spring-loaded pressure pistons, one of which (36) is shown in FIG. 2A, and as 30 press the bag neck firmly against the counter element 35.

The angle of inclination of the resilient blade 33 is such that, under a sufficient pressure difference, air is able to escape from the interior of the bag at least in the orifice regions between successive pressure pistons 36.

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Sealing of the neck of the bag in such a way that a minimum of air space within the bag around the neck is obtained is achieved by means of upper and lower heat sources respectively.

5 37 and 38 in the form of strip lamps which radiate infrared heat at a wavelength providing optimum heat absorption in the plastic composition of the bags 4 within the chamber.

The wavelength of the light emitted by the lamps 37 and 38 is preferably selected so that it coincides with the wavelength most readily absorbed by the bag material. Suitably, the present wavelength ranges from 3 to 4 microns for most plastic films, including multilayer films and laminates such as heat shrinkable (i.e. oriented) three-layer laminates of ethylene vinyl acetate, polyvinylidene chloride and irradiated ethylene vinyl acetate.

A brief exposure of the bag neck area to radiation from the heat emitters 37 and 38 will be sufficient to heat the bag material to its softening point so that the layers of bag material 20 when compressed will be sealed at the mouth and throat areas.

Contact between the bag material and the upper and lower heat source is prevented by wire shields 39 and 40 carried by each of the upper and lower pairs of retaining plates 41 and 42, 25 pivotally suspended on pins 41a and 42a. Each holding plate 41, 42 has a slot 41b, 42b, which displaceably cooperates with each of the curve pins 43 or 44, which are supported by the associated end of a vertically movable upper or lower clamping rod, respectively. 45 or 46. The lower 30 clamping rod 46 comprises a body portion with an elastically prestressed jaw member 46a connected thereto by screw spring springs 46b, which ensures that the jaw member 46a yields when the two clamping bars come into contact with each other.

The retaining means 30 further comprises a shaped thread 48 which is carried by the counter member 35

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in FIG. 2A, the position of the retaining means touches the pouched neck. When applied to a current pulse, the wire pierces the bag neck to allow gas (usually air) to escape inside the discharged throat 5 before sealing. For example, the wire 48 may have a sawtooth shape or a sinusoidal, wavy shape.

As the upper clamping rod moves downward, its curve pins 43 slide down into the slots 41b causing the upper pivotal holding members 41 to pivot 10 clockwise to pivot the heat source 37 and its wire shield 39 to the right away from the path of the downward movement. of the upper clamping rod 45.

Similarly, as the lower clamping rod 46 moves upwardly, its curve pins 44 interact with the slots 42b of the lower holders 32 to swing these holders aside and move the lower heat source 38 and its wire shield away from the path of movement of the upward clamping rod 46. allows the foil material to be clamped between the two clamping bars 45 20 and 46. At the same time, a knife 47, carried by the main part of the lower clamping rod 46, is exposed over the resilient jaw 46a because the compression springs 46b yield and the knife is then in able to cut off the excess bag material from the neck under the seal.

FIG. 2B shows the drive mechanism by which the upper clamp bar is operated during its vertical movement.

As shown in FIG. 2B, the upper clamping rod 45 is provided in two separate parts supported by a central bearing member 30 49 on a vertical guide pin 50 to allow vertical displacement of the two parts of the upper clamping rod 45.

The two clamping rod portions are connected to the lower ends of each of their compression joints 51, which in turn have their upper ends articulated with each of their two double arm units 52, 35 52 ', one of which, 52, can be seen in FIG. 2A.

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The left weight arm 52 has a fixed pivot pin 53 at one corner, a pivot pin 54 at another corner which connects it to the thrust joint 51, and a further pivot pin 55 at the third corner which joins 5 to one end thereof. a secondary drive rod 56.

The other end of the secondary drive rod 56 is articulated at 57 to a corresponding corner of the right double lever arm 52 'which also has 10 pivot pins 531 and 54' which correspond to the pins 53 and 54 described above.

A primary drive rod 58 is connected between a piston rod 59 in a cylinder unit 60 and a further linkage pin 61 on the right double lever arm 52 '. The advance and retraction of the piston rod 59 causes movement counterclockwise and clockwise by the lever units 52, 52, and consequently the raising and lowering movement of the tensioning rod 45.

A similar actuator connection is provided to drive the main body of the lower tension rod 46 up and down.

As also shown in FIG. 2B, the upper clamping rod 45 has screwed on a protective element 62 for the purpose of defining a slot into which the knife 47 can penetrate 25 when the upper and lower clamping bars 45 and 46 are brought together.

The Figures 2A and 2B operate at several stages during the cycle of the machine, which it must describe.

The mode of operation shown in FIG. 1, using 30 of bag 4 formed of heat shrinkable, i.e. oriented, foil material is as follows:

A filled with unsealed bag 4 of heat-shrinkable packaging film is placed in the vacuum chamber 1 and the chamber cover 3 is driven downward to close the chamber and allow the sealing of the chamber at its rim 20.

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One form of a heat shrinkable (i.e. oriented) film used for the bag 4 may be a three-layer laminate of ethylene-vinyl acetate, polyvinylidene chloride and irradiated ethylene-vinyl acetate as disclosed in U.S. Patent No. 3,741,253 and sold by W.R. Grace under the heat label "Barrier Bag" ®.

As explained above, the lowering of the chamber cover 3 brings the elastic blade 33 down towards the bag to hold the neck to the upper surface of the counter member 10 35. At this stage, the upper and lower clamping bars 45 and 46 are retracted and the heat sources 37 and 38 are located. in the i: 'fig. 2A. Shrinkage heat is applied to the exterior of the bag prior to a substantial evacuation of air from the interior of the chamber, and the applied warts cause the bag material to begin to shrink.

The air enclosed in the effectively sealed bag (retained by the elastic blade 33) opposes the shrinkage action and keeps the bag material "spilled" away from the surface of the product therein 20 (for example, a cut of fresh red meat). Thus, while keeping the bag free from the surface of the product, the circulation of warm air around the outside of the spouted bag material provides additional heat to the bag material and completes the heat shrinkage by withdrawing the foil material down towards the surface of the product. However, the bag material will have been spilled away from the surface of the product long enough to allow sufficient heat transfer to the spilled film which is unable to deliver any significant heat to the product 21 and to have heated the film to its shrinkage temperature. so that a very large part of the shrinkage energy can be recovered.

During this time, the heat sources 37 and 38 will either be inoperative or preferably in operation at a low heating level which will not enable them to heat the foil material in the bag neck to achieve fusion.

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Narrowing of the bag mouth when retained by the resilient retaining means 30 ensures that the application of heat by convection to the exterior of the bag proceeds that any excessive pressure difference built up inside the bag can be controlled. by venting the gas (usually air) from the interior of the bag to an extent which still keeps the bag material spilling away from the surface of the product 21 therein. Since the spilling effect depends on factors common to a particular portion of products 21 (e.g., surface temperature, amount of air contained in the product, and surface product of the product, e.g. stickiness), it may be useful in observing to determine when spilling may occur. is expected to occur, and then time the process so that the evacuation begins at the same time for all products in one batch and is time-controlled by appropriate time management. Any other control means can be used if desired.

Because the bag during the heat shrinkage step is still resiliently retained across its neck, further air escape may occur through the neck from the interior of the bag in the unlikely event that an excessive pressure difference across the bag material occurs while the remainder of the bag shrinks back onto the surface of the product. nc the product 21, so as to provide a substantially wrinkle-free surface covering the product 21, and nevertheless allow the bag neck to be capable of sealing as the clamping bars 45 and 46 close together for contact with each other.

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At the end of the play-off phase, and before the evacuation of the bag has to begin, short-term current is sent through it. thread 48 to pierce the pouch neck and to release the air contained therein.

The evacuation of the chamber atmosphere (and of the now 35 breakthrough bag 4) progresses until the desired vacuum level is achieved. By or slightly before the end of 12

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In the evacuation phase, the lamps 37, 38 can be fed to their maximum output to emit radiant heat at the desired wavelength for optimum heat absorption in the film material, thereby heating the pierced bag neck to the melting temperature.

The cylinders 60 are then actuated to bring the upper and lower clamping elements 45 and 46 together and simultaneously swing away the heat sources 37 and 38 and their associated wire shields 39 and 40.

Once the upper clamping rod 45 has come into contact with the prestressed clamping jaw 46a, further operation of the cylinders 60 causes the knife 47 to cut the bag neck to separate the excess material therefrom. The clamping elements 45 and 46 ensure retention of the neck along the knife 47 to effect sealing. Throughout this operation, the bag will still be clamped between the resilient blade 33 and the counter member 35 so that the bag will still be securely located in the holding means 30.

The retraction of the upper and lower tension bars 45 and 46 will return heat sources 37 and 38 and their respective wire shields 39 and 40 to that of FIG. 2A. The evacuation of the chamber takes place after this withdrawal of the clamping bars 45, 46, 25 so that any possible escape of any residual air from the bag can take place.

When the vacuum chamber is re-pressurized upon opening, the heated neck portions of the bag to the left of the clamping members 45 and 46 are compressed so as to obtain a fusion weld and a reduction of any excess bag material around the sealing zone to obtain a neat appearance of the finished packaging. .

The excess bag material cut off by the knife 47 is still retained between the elastic blade 33 and the counter member 35 and may be removed during or after removal of the package from the opened chamber.

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The method described above is particularly suitable for use with moist products such as fresh / red meat in heat-shrinkable bags, because the pressure increase on the surface of the meat during bag play acts to retain the moisture in the product and counteracts the dew formation on the inner surface of the bag. is in play mode. Furthermore, the rapid venting of the entrapped air, after breaking through the bag, allows the bag material to quickly contact the product before any such dew formation occurs.

Folgelia is the appearance of the finished packaging especially appealing when it comes to moist products such as fresh red meat.

Against all products packaged by this method, the wrinkle-free nature of the product is enhanced by the introduction of a preliminary shrinkage step followed by a subsequent evacuation (as opposed to the usual vacuum sealing order and shrinkage afterwards).

Furthermore, the finished packaging of the present invention 20 is much improved over prior art shrinkable packages, where a water shrinkage bath has been used to mitigate the heat dissipation effects of the relatively cold high-density product, since shrinkage of the film in contact with air enables 25 a greater degree of recovery of the shrinkage energy and consequently a greater increase in the thickness, with the result that the barrier properties of the bag are more effective (important for keeping the product hermetically sealed and fresh until the time of use). Furthermore, due to the increased thickness, such a 30 bag is more resistant to abuse.

Because the air pocket trapped in the bag during the preheat shrinkage phase opposes collapse of the bag and releases contact between the bag and the 35 cold product, this thickness-enhancing effect is even more noticeable, and this is also the wrinkle-free appearance of the bag, which in turn depends on the extent of recovery. of latent shrinkage energy in the foil material.

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Furthermore, because the shrinkage is caused by air currents moving around the entire product, the shrinkage of the bag will be uniform around the product and this will eliminate the risk of entrapment of air pockets behind the "equator" of the product (i.e., the largest cross-sectional area of a plane). perpendicular to the longitudinal axis of the bag).

Furthermore, the aforementioned feature ensures that there is little or no water vapor in the air between the product and the shrink bag (caused by shrinkage 10 beginning before any pressure reduction, and even causes a slight increase in pressure) that less shrinkage heat is required because the dry air on the inside of the bag absorbs less heat than humid air would.

Because the upper and lower support members 31 and 32 of the resilient retaining means 30 are supported by the lower chamber portion 2 and the chamber cover portion 3 respectively, they automatically close together for contact with each other as the chamber is closed, and all the operator needs to do is to ensure that the neck of the bag 4 is disposed on the counter element 35 before closing the chamber.

When the filled bags are introduced into the chamber 1 by a conveyor, the conveyor can, if desired, ensure that the bag neck, when the bag 4 is stopped, is properly positioned for narrowing clamping without the need for careful placement with the aid of an operator.

As stated above, other bag closure mechanisms may be provided for use with the jet heat sealing units 13 and 14 described above.

For example, the bag neck can be closed with a conventional 30 sealing rod 70 (Fig. 3) which both cuts off excess material and seals the bag mundane along the line of pressure between upper and lower clamping bars (by means of a resistor heater). The application of heat to the neck area between the trim sealer 70 35 and the product 21 results in the fact that when the chamber 1 is re-pressurized, the bag material in the neck area will

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have been heated to such an extent that it melts to itself upon collapse, leaving a much nicer neck area on the packaging.

Alternatively, the bag neck may be placed in an assembly unit 5 71 (Fig. 4) so that it is assembled as the chamber closes and a staple is attached to the neck of the bag with a staple unit 71a after the evacuation and shrinkage is completed. Such staple means placed in the chamber are disclosed, for example, in British Patent Specification no.

10 1,353,157.

Yet another possibility is that the stapler 71a is omitted in FIG. 4, and that the assembly function is performed after the activation of the infrared heat sources has caused heating of the bag neck in the area to be assembled.

15 When the thus heated and softened neck areas are contracted by the function of the assembly unit (which may be, for example, of the kind disclosed in British Patents Nos. 1,353,157, 1,361,142 and 1,496,740), the assembly effect is sufficient to produce 20 the neck material to adhere to itself and to resemble the appearance of a staple but without a staple. The mere softening of the bag neck area will suffice to cause intimate contact and sealing of the overall neck area.

For example, the schematically illustrated assembly unit 71 can operate in two stages as contemplated by British Patent Specification No. 1,353,157, first assembling the bag for a horizontal, groove-like appearance when the chamber is closed, and sufficiently limiting gas flow 30 from the bag interior. to produce the desired playback effect before activating the infrared radiation sources. In another assembly step, the length of the grooves is then reduced so that the bag neck is laced together to a self-adhesive, overall design. Alternatively, another mouth-restricting function can be performed on the bag, and the assembly unit 71 can then function to completely assemble the bag neck after the outward heating.

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The foregoing description of the various operating cycles possible with the one shown in FIG. 1, throughout, refers to the use of a heat shrinkable film. However, it will be possible to practice the process of the present invention with other films, for example self-welding films which are heat softened and will then weld together as they come into contact with one another.

Likewise, the alternative chamber designs 10 shown in FIG. 3 and 4 are used with any suitable foil including heat shrinkable foil and self-welding foil.

FIG. 5 schematically shows a possible control circuit for activating the radiant heat emitting lamps 37 and 38.

A variable transformer bridge 72 is connected across input terminals 73 and 74, and over the same two terminals 73 and 74 is connected a shunt line comprising a micro switch 75 and a timing switch 76. A further shunt line comprises a switch 77 and a circuit breaker 78, 20 the circuit breaker itself being connected to two contacts 79 and 80 of the secondary circuit of the transformer 72. Thus, the two contacts 79 and 80 control the activation of the infrared emitting lamps 37 and 38 which are connected in parallel in the secondary circuit of the transformer 25 72 .

The variable transformer is permanently connected and the start of the cycle is triggered by the function of micro switch 75 which responds to some movable mechanical component, for example, closing the chamber cover 30 3. Closing of the micro switch 75 starts the time cycle of the timer 76 so that the switch 77 immediately connects and activates circuit breaker 78 which terminates contacts 79 and 80 to turn on lamps 37 and 38.

After a time lapse determined by timing 35 76, switch 77 disconnects circuitry for circuit breaker 78 which disconnects switches 79 and 80 and turns off lamps 37 and 38.

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In a particularly convenient modification of the embodiment shown in FIG. 5, the lamps 37 and 38 may be reduced to a standby power setting (for example, 20% of their full 5 power), instead of being completely switched off when circuit breaker 78 is switched off. This can be done, for example. is achieved by having a double contact system at the switches 79 and 80, so that in one position of the contacts a "standby circuit" is switched on for switching on the lamps 37 and 38 with their steady-state power setting, and in the other position of the contacts it is shown in FIG. 5, the main circuit shown is closed.

Adjusting the variable transformer 72 can allow the lamp power to be changed and likewise the timing 76 can be adjustable to allow 15 a time interval of, for example, from 2 to 6 seconds for the operation of the lamps 37 and 38.

A preferred lamp type for use as lamps 37 and 38 is Philips lamp type 13195 X / 98, which is sold by Philips.

Advantages of using the melt seal system described and illustrated herein include the fact that the thermal inertia of the infrared lamps 37 and 38 is very small, so that it is possible to switch them on only when melt seal is needed. In addition, melt-sealing has the advantage that no physical contact exists between the heat-supplying lamps and the plastic material to be connected.

It is a particularly important advantage of the present invention that heat is applied to the films by radiation before contacting them, thereby ensuring that the shortest possible radiant energy path can be provided from the lamps to the clamped films. the lamps 37 and 38 need to be placed close together. Instead, the lamps may be quite apart and the bag material may be spilled into the vicinity of the lamps to reduce the distance from the lamps.

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the heat source of the bag material. Thereby, a much less cumbersome apparatus is provided from the point of view of (a) placing the bag in the chamber or (b) more generally (when the melt sealing of a foil envelope 5 is performed without the use of a vacuum chamber) placing any two foil portions to be welded, i. a position ready for melt heating with the apparatus of the present invention.

In addition, the amount of energy communicated to the foils can be quickly and easily adjusted either by changing the supply voltage of the lamps or by changing the time during which they are switched on or by setting both parameters.

If desired, the neck area of the bag may be imprinted with a material having a high adsorption coefficient to provide even more intense heat absorption.

The vacuum levels that can be considered for the processes described above will be of the order of 5 Torr. However, the vacuum may, if desired, be much "softer" (greater residual pressure). For example, by packaging products such as high-gas cheeses which naturally emit gas, for example carbon dioxide, and will do so to a much greater extent if packaged under high vacuum conditions.

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

Temperatures of 90 to 140 ° C in the unfolded film will be necessary to obtain heat shrinkage in the case of biaxially oriented shrinkable foils. However, higher temperatures of the radiant heat emitting heating units 35 13 and 14 on the neck region of the foil to promote melt sealing can be announced.

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The foregoing description generally refers to the effect on a single bag 4 in the chamber, although it is clear that in FIG. 1, two separate bags are provided. 4. The method and apparatus according to the invention may be adapted for use with one package or with two or more packages which are sealed simultaneously, and this versatility applies equally to the three separate embodiments depicted in FIG. FIG. 1, 3 and 4 as well as any other embodiments which fall within the scope of the claims.

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Claims (12)

A method of forming a sealed package in a vacuum chamber, wherein a product to be packaged is placed in a sachet (4) of plastic wrap, the neck of the bag being held out by keeping the mouth of the bag resiliently clamped at the same time as the outside pressure in the chamber prevailing in the chamber is reduced and the bag is heated using heating means (6,7,8,9,10,11) until the pressure difference between the interior and exterior of the bag achieves a value at which a holding device (30) for the neck of the bag yields and permits gas discharge through the mouth of the bag, characterized in that while the neck of the bag (4) is spaced out, the separated sections of the neck are heated by sources of infrared radiation (13,14) located in the near-immediate vicinity the throat neck without touching it, and the neck throat of the bag is then perforated for gas removal from the bag (4) and the neck portions are brought into contact with each other to close the neck as the neck portions liable to each other as a result of the touch. Method according to claim 1, characterized in that the playback of the bag is provided by heat shrinkage of the bag material while the bag neck is kept compressed. Process according to claim 1, characterized in that the film material consists of a multilayer film comprising at least one layer of ethylene vinyl acetate, one layer of polyvinylidene chloride and one irradiated layer of ethylene vinyl acetate and the infrared radiation has a wavelength of 3-4 microns. An apparatus for forming a sealed package in a vacuum chamber (2,3) comprising a support (5) for a product placed in a bag (4) of plastic film, means for holding the bag neck, which means comprises means (30) ) for clamping the neck and organs (6,8,10 and 7,9,11) of the bag (4) for heating the played bag on the support (5), and while clamped by the clamping means (30), and means for bringing the opposite portions of the bag neck into contact with one another for the purpose of closing the package, characterized in that at least one infrared radiation source (13,14) is inserted in the vacuum chamber (13,14) near the played bag neck without touching it to radiate and heat the opposite portions of the neck, and the means for contacting the middle portions of the neck of the bag include means (48) for the discharge of gas from the bag (4) for lifting the neck out. -flushing after heating with the in source of radiated radiation (13, 1 ° 14) as a result of which the heated neck material contacts itself and closes as a result of the contact. Apparatus according to claim 4, characterized in that the means for contacting the opposite parts of the neck of the bag (4) include a neck clamping unit (71) which is arranged to compress the bag neck by assembling it for providing a barrier and being programmed to collect the bag neck after the infrared radiation emitting sources (13, 14) are energized. 1:20 Apparatus according to claim 4 or 5, characterized in that the means for contacting the opposite parts of the bag neck include (a) a means (48) for perforating the played bag neck and (b) cooperating holding jaws (45). (46a) located at the perforating member (48) of the bag neck and at the side thereof closest to the bag support (5) for compression of the bag neck to re-close it after the gas has passed through the perforated neck party. Apparatus according to any one of claims 4 to 6, characterized in that the sources of infrared radiation include a pair of strip lamps (13, 14) arranged parallel to each other on both sides of the intended location of the bag (4). The neck means for clamping the neck of the bag (4) include a pair of parallel pressing rods (33,35) arranged at the space between the strip lamps (13,14) and arranged to press the neck of the bag. O DK 154882 B Apparatus according to claim 7, characterized in that at least one (33) of the pressing rods can yield during its pressing function, so that gas can escape from the bag (4) if there is an excessive pressure difference over the film material of the bag. . Apparatus according to claims 6 and 8, characterized in that the holding jaws (45, 46a) are movable towards and away from one another along a functional path and that the strip lamps (13, 14) are mounted for movement between a working position in which arranged along said path of movement between separate positions of the holding jaws (45, 46a), and an inactive position in which they are free of this operating path so that the holding jaws can close together. Apparatus according to claim 9, characterized by 15 wire screens (39,40) attached to the strip lamps, which prevent physical contact between the strip lamps (13,14) and the bag's throat material during heating. Apparatus according to any one of claims 7 to 10, characterized in that it includes means for supplying the strip lamps (13, 14) at a first level, at which they emit infrared radiation of a strength sufficient to heat the played bag neck, and another level at which they operate at a much lower energy consumption in a standby mode. 25 Apparatus according to any one of claims 7 to 11, characterized in that it includes a timing (75) for controlling the emission of infrared radiation from the strip lamps (13, 14) and means (72) for controlling the power at which they emit the bag-heating infrared radiation. 30 35