JPH0487932A - Method and device for multi-staged shrink wrapping - Google Patents

Abstract

PURPOSE:To enable use of a container such as a deformable and thin tray and to eliminate loosening or overlapping at a sealing part by a method wherein the container and food are wrapped by high barrier plastic film which is formed with an exhaust hole, and heated on an upper part, then on a lower side and finally at both ends. CONSTITUTION:Food 4 is housed in a tray 1. Next, the tray 1 is wrapped with high barrier plastic film 5 to make lateral pillow wrapping. At this time, an exhaust hole 7 is formed in the high barrier plastic film 5 at a place which becomes a back surface of the tray 1. Then a lower side of the tray 1 is heated to make the high barrier plastic film 5 undergo a lower shrink. In this case, air and gas inside a pack are exhausted compulsorily by pressing the tray 1 on the upper surface with a compulsory exhausting conveyor 11. Next, an upper part of the tray 1 is heated to make the high barrier plastic film 5 undergo an upper shrink. Finally both end parts of the tray 1 are heated to make the high barrier plastic film 5 undergo both-end shrink.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to shrink packaging of fresh foods such as meat and seafood placed in containers.

(Prior Art) Stretch packaging has conventionally been generally used as a food packaging method.

Stretch packaging is a simple method that involves placing food in a container such as a tray and then wrapping it in a PVC film, so it is used for a wide range of foods such as fresh fish, meat, and vegetables. ing.

In addition, stretch packaging can reduce packaging costs compared to other types of packaging. Further advantages include the ability to clearly see the food inside through the stretched film.

(Problems to be Solved by the Invention) However, although conventional stretch packaging is easy to perform in packaging operations, it has a drawback in that it has a poor ability to maintain the freshness of the packaged food.

The reason is that stretch packaging does not have sealing properties. Additionally, there are limitations to the films used for stretch packaging, including weak barrier properties and lack of sealing properties.

Therefore, conventional stretch packaging has a problem in that the food contained therein is easily oxidized and contaminated with microorganisms.

In order to overcome these drawbacks of stretch wrapping, the applicant of the present application has already proposed shrink wrapping (see, for example, Japanese Patent Application No. 1-317830).

This shrink packaging looks similar to stretch packaging, but has significantly improved barrier properties and sealing properties, and can also enhance the freshness-keeping function of the packaged food.

Here, shrink packaging is a packaging method used for the exterior packaging of natto, etc. It uses a film with small holes for ventilation, is ramped and sealed in a packaging machine, and then shrink-formed in a heat tunnel. This is how it was done.

Such shrink packaging will be explained.

Using shrink film, horizontal pillow packaging machine or L
After packaging using a mold packaging machine, etc., the film is shrunk in a shrink tunnel. In the shrink tunnel, a blower blows air and heats the air to turn it into hot air, which is then blown onto the product. While the product is transported on a roller conveyor, the film is shrunk by being exposed to hot air from above, below, left and right. Furthermore, since the tunnel is sealed, the overall temperature inside has risen considerably. Shrinking conditions are controlled by conveyor speed, tunnel length, hot air temperature, and hot air outlet position, but since the entire tray is heated and shrunk at once, weak trays may be deformed by the shrinkage force of the film.

As described above, in conventional shrink packaging, containers such as trays were required to have structural strength in order to prevent the contents from deforming, since the packaging was simply passed through a heat tunnel using shrinkage.

Further, since the shrinking process was performed in one shot with lower heating and upper heating, there was a problem in that the sealed portion remained a little sluggish.

The present invention further improves such shrink packaging, and provides a multi-step shrink packaging method and its packaging device that can use containers such as thin trays that are easily deformed, eliminate looseness at the sealing part, and provide a snug fit. The purpose is to

(Means for Solving the Problems) According to the present invention, in order to achieve the above object, in a method for shrink-wrapping food contained in a container, the container and the food are wrapped in a high-barrier plastic film in which exhaust holes are formed. a step of performing bottom heating of the container and shrink-wrapping the bottom, and top heating of the container;
A step of shrink-wrapping the upper part is performed.

Further, after the main heating, a step of heating both ends of the container and shrink-wrapping both ends is performed.

Further, in a shrink-wrapping apparatus for food stored in a container, a means for wrapping the container and the food with a high-barrier plastic film in which an exhaust hole is formed, and a lower heating device for heating the container and shrink-wrapping the lower part; The container is further provided with a lower heating device which performs upper heating of the container and performs upper shrink wrapping.

Further, after the above-mentioned heating, both ends of the container are heated and both ends are shrink-wrapped.

(Function) Conventional shrink packaging for food was done by simply passing it through a heat tunnel using a heat shrink, which required structural strength of the tray etc. to prevent the contents from deforming. For example, first, lower heating is performed, then upper heating is performed, and multi-step shrinking is performed, so that even if the tray is thin and easily deformed, deformation can be suppressed and shrink packaging can be performed.

In addition, with bottom heating or top heating, some sluggishness remained in the sealed portion, but that sagging can be eliminated by adding heating at both ends.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view of a multi-stage shrink packaging process showing an embodiment of the present invention.

First, as shown in FIG. 1(a), a tray 1 as a container is supplied. A deaeration hole 2 is formed in the bottom surface of this tray 1.

Next, as shown in FIG. 1(b), an oxygen absorber 3 is placed in the I-ray 1. In this case, gas flushing
Gas replacement may be performed to achieve deoxygenation. However, depending on the type of food, it is not necessary to actively remove oxygen.

That is, the degree of deoxygenation can be appropriately set depending on the food to be stored.

Next, as shown in FIG. 1(c), the food 4 is placed in the tray 1.

Next, as shown in FIG. 1(d), the tray 1 is wrapped in a packaging machine using a high-barrier plastic film 5 to perform horizontal pillow packaging. At this time, an exhaust hole 7 is formed in the high-barrier plastic film 5 at a location that will be the back surface of the tray 1. In addition, 6 is a drum seal part.

Next, as shown in FIG. 1(e), the lower part is shrunk. That is, the lower part of the tray 1 is heated to shrink the high barrier plastic film 5 in the lower part. In that case, as shown in FIG. 6, the tray 1 is held down from above by a forced exhaust conveyor 11 to forcibly exhaust the air and gas inside the pack.

Next, as shown in FIG. 1(f), the upper part is shrunk. That is, the upper part of the tray 1 is heated to shrink the high barrier plastic film 5 in the upper part.

Furthermore, as shown in FIG. 1(g), the direction of the tray 1 is changed to shrink both ends. That is, tray 1
Finally, as shown in FIG. 1(h), heat the both ends of the high barrier plastic film 5 to shrink the high barrier plastic film 5.Finally, as shown in FIG.
Paste Rahel 8 on the back side of and seal it.

The above steps can be briefly summarized as a flow as shown in FIG.

First, step (■) is to feed the tray, then step (■) is to add the oxygen absorber to the tray, step (■) is to place the food in the tray, and then step (■) is to place the food into the tray. At the same time as packaging, perform deaeration holes (step ■), shrink the lower part while removing pressurized air (step ■), then shrink the upper part (step ■), and then shrink the upper part (step ■). Shrink (step ■) and finally seal by labeling (step ■).

FIG. 3 is a process perspective view of a multi-step shrink packaging method showing a specific embodiment of the present invention.

First, as shown in FIG. 3(a), a tray 1 containing food (not shown) is wrapped in a high-barrier plastic film 5 using horizontal pillow packaging.

Next, as shown in FIG. 3(b), the lower part of the high-barrier plastic film 5 is shrunk by upper heating. That is, only the back surface of the tray 1 is heated and shrunk first. Thereby, the top seal portion is located below the end surface (side surface) of the tray.

As this bottom heating device, as shown in FIG. 6, a conveyor 12 (described in detail in the direction change device described later) having rollers 13 that can rotate on its own axis is arranged, and a hot air blowing device 14 is installed below the conveyor 12. has been done. As shown in FIG. 9, the hot air blowing device 14 is composed of a base 16 provided with a hot air blowing hole 15 at the lower end, and a lid 17 attached to the base 16 and having a hot air blowing hole 18 formed therein. .

Next, as shown in FIG. 3(c), the high barrier plastic film 5 is subjected to upper shrinkage by upper heating. That is, the surface of the tray 1 is heated and shrunk.

Furthermore, there are two methods of heating as shown below.

(1) As shown in FIG. 7, the lower heating device 25 is
By blowing hot air intensively onto the surface, conveyor 21
(2) A method of shrinking the high-barrier plastic film 5 wrapping the upper tray 1; and (2) a method of shrinking the high-barrier plastic film 5 wrapping the upper tray 1; and (2) a method of shrinking the high-barrier plastic film 5 wrapping the upper tray 1;
There is a method in which the lower heating device 30 blows hot air only onto the surface.

Choose one of these. The former is effective when the food is frozen or comes into direct contact with the protruding film from the depth of the tray, and the latter is effective in other cases. In this case, if the heating is too strong, the tray 1 will be exposed to the high barrier plastic film 5.
Because the shrinkage force causes deformation, it is desirable to perform heat shrinkage relatively slowly. In addition, in FIG. 7, 23 is a bottom heating device, and 27 is a lateral heating device.

In addition, if it is possible to shrink the tray 1 upside down, first shrink-wrap the bottom of the tray 1 using a bottom heating device, and then shrink-wrap the top of the tray 1 using a bottom heating device. Then, shrink wrapping may be performed.

Next, as shown in FIG. 3(d), the direction of the tray 1 is changed. In this direction change, as shown in FIG. 4, the tray 1 traveling on the line is guided by a guide plate 31, and the pin 36 hits the tray 1, causing the direction to change by 90 degrees. This point will be specifically explained using FIG. 5. A roller 33 is provided at the tip of the line 37 and is rotated by a drive belt 35.
When the rollers 34 rotate, a group of rollers 34 are rotated by a transmission belt 38 that is applied so as to be driven one after another. Note that these rollers are supported by both side frames 32 so as to be freely rotatable.

Then, the tray 1 that has undergone the upper and lower shrinks is guided by the guide plate 31, and a pin 36 hits the tip slightly below the guide plate 31. Then, the tray 1 is turned 90 degrees and transferred to a both-end heating device having a plurality of wire-shaped endless belts 42 for performing the next step of heating both ends. Note that 41 is a driven pulley, and although not disclosed, it is desirable that guide plates are disposed on both sides of this portion for smoothly guiding the tray 1 whose direction has been turned by 90 degrees to the both-end heating device.

Next, as shown in FIG. 3(e), both ends of the high barrier plastic film 5 are shrunk by heating both ends. That is, only the ends of the product that have not undergone sufficient heat shrinkage due to top heating are heated.

Here, as shown in FIG.
The upper surface and side surfaces of both ends can be heated simultaneously by hot air from the hot air blowing holes 52 to the top surface of both ends of the both ends heating device 50 and the hot air blowing holes 53 to the side surfaces of both ends. do. Note that 51 is a hot air outlet.

Next, as shown in FIG. 3(f), the direction is changed again, and as shown in FIG. 3(g), after being changed to the original direction, it is transported out as a product. Note that here as well, the direction change is performed in the same manner as described above.

In this way, (1) top heating and (2) top heating are performed on the line.

In addition, (2) multi-stage shrink packaging can be performed by adding heating at both ends and performing heating in sequence.

Further, in the above embodiments, a tray is shown as the container, but it goes without saying that various types of containers can be used.

In particular, since multi-stage shrinking is performed, the deformation force of the stored food can be significantly reduced compared to conventional one-shot shrinking, and thin-walled containers and inexpensive materials that could not be used in the past can be used. For example, a container made of high impact polystyrene or expanded polystyrene can be used.

In addition, in the case of hamburger packaging, the tray material thickness is 50 mm.
0μm, shrink wrapping is possible even when the tray material thickness is as large as 275 mm in length, 160 mm in width W, and 35 mm in depth D, as shown in Figures 11 and 12. Ta.

Note that the present invention is not limited to the above embodiments,
Various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

(Effects of the Invention) As described above in detail, according to the present invention, the following effects can be achieved.

(1) Shrink packaging using thin trays, trays made of inexpensive materials, or large trays is possible, so costs can be reduced.

(2) Even a tray with a complicated structure that is easily deformed can be shrink-wrapped while suppressing deformation.

(3) By adding heating at both ends, the sagging of the sealed portion can be eliminated and packaging can be provided with a snug fit.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a multi-stage shrink packaging process showing an embodiment of the present invention, Fig. 2 is a schematic flowchart of the multi-stage shrink packaging, and Fig. 3 is a multi-stage shrink packaging method showing a specific embodiment of the invention. Fig. 4 is an explanatory diagram of the tray direction change, Fig. 5 is a perspective view of the tray direction change device, Fig. 6 is a configuration diagram of the heating device, and Fig. 7 is the shrink tunnel. 8 is a configuration diagram of the heating device, FIG. 9 is an exploded perspective view of the hot air blowing device, FIG. 10 is a configuration diagram of the heating device at both ends, and FIG. Perspective view showing (without), 1st
FIG. 2 is a rear perspective view showing the shrink-wrapped state. 1... Tray, 2... Deaeration hole, 3... Oxygen absorber,
5...Hyperia plastic film, 7...
Exhaust hole, 8... Rahel, 11...'J Exhaust control conveyor, 1221... Conhair, 13.33.34...
・Roller, 14...Hot air blowing device, 15...Hot air outlet, 16...Hose, 17...Lid body, 18.
...Hot air outlet, 20...Shrink tunnel,
23, 30... Upper heating device, 25... Upper heating device,
27... Lateral heating device, 31... Guide plate, 32...
・Both side frames, 33. 34... Roller, 35... Drive belt, 36... Pin, 37... Line, 38...
Transmission belt, 41... Driven pulley, 42... Endless belt, 50... Both end heating device, 52... Hot air blowing hole, 53... Hot air blowing hole. Patent applicant Primaham Co., Ltd. Agent Patent attorney Mamoru Shimizu (1 other person) Figure 10

Claims (7)

[Claims] (1) A shrink-wrapping method for food stored in a container, which includes: (a) wrapping the container and the food with a high-barrier plastic film in which exhaust holes are formed; (b) heating the container at the bottom and shrink-wrapping the lower part. and (c) heating the container and shrink-wrapping the upper part. 2. The multi-step shrink packaging method according to claim 1, further comprising the step of (d) heating both ends of the container and shrink-wrapping both ends after step (c). (3) The multi-step shrink packaging method according to claim 1 or 2, wherein air and gas are forcibly discharged at the same time as the container is heated. (4) A shrink-wrapping apparatus for food stored in a container, which includes: (a) means for wrapping the container and the food with a high-barrier plastic film in which an exhaust hole is formed; and (c) a top heating device that performs top heating of the container and shrink-wrapping the container. (5) The multi-stage shrink packaging method according to claim 4, further comprising a both ends heating device which heats both ends of the container and performs shrink wrapping of both ends after the top heating. (6) The multi-stage shrink packaging apparatus according to claim 5, further comprising means for, after top-heating the container, bringing the container into contact with a pin, automatically inverting the container, and transferring the container to the top-heating device. (7) Claim 5, further comprising means for automatically inverting and discharging the container by bringing it into contact with a pin after heating both ends of the container.
Multi-stage shrink wrapping equipment as described.