US3058274A - Arrangement for heat-sealing of packages - Google Patents

Description

Oct. 16, 1962 Filed NOV. 9, 1959 o. v. CHRISTENSSON 3,058,274

ARRANGEMENT FOR HEAT-SEALING OF PACKAGES 3 Sheets-Sheet 1 INVENTOR 00 wk; FEW

cum c/ ATTORNEKS Oct. 16, 1962 o. v. CHRISTENSSON 3,058, 74

ARRANGEMENT FOR HEAT-SEALING OF PACKAGES Filed NOV. 9, 1959 3 Sheets-Sheet 3 IN V EN 1 OR 00 VIM/P O/F/S 7EK$-9GM ATTORNEYS United States Patent 3,058,274 ARRANGEMENT FGR HEAT-SEALWG 0F PACKAGES 0d Vikar Qhristensson, Vikavagen 5, Bromma, Sweden Filed Nov. 9, 1959, Ser. No. 13,412 Claims priority, application Sweden Mar. 16, 1959 1 Claim. (Cl. 53-112) This invention relates to the packaging of products, particularly food stuffs easily damaged by the outer atmosphere, wherein use is made of packages consisting of an outer covering of cardboard or similar material and an inner lining. The lining is of suitable airtight material, such as plastic. After filling the package with the material to be packed, the mouth of the lining may be heat sealed except for a rather small portion thereof, where after the package'is introduced into an evacuation machine. The machine is then supplied with a vacuum of rather high degree, thereby evacuating the interior of the package. The package is thereafter heat sealed along the remaining small part of the mouth. In this manner the package material is now contained in an atmosphere of greatly reduced air pressure, e.g., a few millimeters of mercury, and the package life is greatly increased.

In the execution of this principle of vacuum packing, the final heat sealing is provided while the package is still in an outer evacuated atmosphere within the evacuation machine.

To stand the change of shape occurring during the evacuation the lining must be of a very easily formable material, having little or no stiffness of its own. The change of form during the evacuation causes a tendency of the lining or the bag to assume many different shapes; and the month, which is to be heat-sealed can at the time of the heat-sealing be easily displaced. If the package is to be vacuum tight, then the heat-sealing must take place with the best possible care, and the heated tools, which are to be pressed against the two sides of the mouth for causing the heat-sealing, must contact the mouth along the whole length of the open part so that continuity is created between the earlier performed part of the heatsealing and the remaining part of the heat-sealing of the mouth. Further, the mouth must be in a smooth state, because any plait or crease in the mouth may cause leakage.

The difiiculties in meeting with these demands are expecially important when considering that, at the time of heat-sealing, the package is in the interior of a closed and evacuated chamber. Thus one cannot usually see the package or readily introduce any tools. Therefore the steps for correcting the position of the mouth of the package must take place automatically and accurately.

The automatic handling for these steps concerned must further be accomplished by the use of shafts or other controlled means entering into the evacuated chamber from the outside. In order to avoid leakage it is therefore very important that the number of such controlled means be limited.

The invention is based upon the principle that the mouth of the lining or the bag, in advance, before the package is introduced into the evacuation machine, is closed along the major part of its length, so that only a rather small part of the mouth remains open for the evacuation. This makes possible the use of special means embracing the already sealed part of the mouth at the introduction of the package into the evacuation machine and before the commencement of evacuation. Therefore the whole mouth is retained in an exact position relative to the heatsealing means. The invention further contemplates a device wherein the means which are thus used for embracing the ah'eady sealed part of the mouth, and the "ice means, by which the remaining part is heat-sealed can be operated by means of one single entering shaft or the like.

The invention will be described below in connection with the attached drawings, which show a form of execution of the invention. In the drawings FIG. 1 shows a perspective view of a package which is to be packed and closed according to this invention, FIG. 2 shows a schematic view of the packaging machine, in which the evacuation and closing takes place. FIGS. 3 and 4 show a pair of sectional views according to the lines IIIIII and lV-IV, respectively, in FIGS. 5 and 6 of an evacuation pocket, whereas FIGS. 5 and 6 show sections along the lines V-V and VI-VI, respectively in FIGS. 3 and 4.

FIG. 7 finally, shows a view of the tool used for the heat-sealing.

The package, in the chosen form of execution, consists in an outer package of cardboard, which is rectangular in cross-section and has a broad side 10 and a small side 11. At each broad side there is connected a closing flap l2 and 13, respectively, and at each small side there is connected a closing flap 14 and 15, respectively. The lining has been previously closed at the bottom of the package according to FIG. 1, and the closing flaps have also been previously folded inwards and pasted together. At the top, however, the closing flaps are folded outwards after the packed material has been fed to the package, in a manner that will assist in the continuous handling of the package in the evacuation machine. In advance of the evacuation machine, the edge 16 formed at the closing of the lining has been heat-sealed (welded) along the major part of its length, but a small unwelded part 17 has been left at the outmost part at the one edge. The evacuation of the package then takes place through the unwelded opening.

When the packages are introduced into the evacuation and closing machine schematically shown in FIG. 2 the packages are in the state shown in FIG. 1. This machine consists in a carousel 20, which is in continuous movement in the direction of the arrow 21. In the carousel a number of chambers or pockets are provided separately so that each of them may be evacuated separately. This is done by means of a common evacuation conduit, a valve being provided in the connection conduit between the vacuum conduit and each pocket for controlling the increase of vacuum in the pocket. The carousel is shown to contain eighteen such pockets 12. The pockets are provided each with one shutter, covering all of the peripheral side of the pocket, the shutter being turned upwardly for opening access to the pocket by means of a horizontal shaft applied at the upper edge of the pocket.

The packages to be evacuated and closed are fed to the carousel 20 by means of an auxiliary carousel 23, receiving the packages from a path 24 and transferring them into an empty pocket 22. During the continuous movement of the carousel 20 in the direction of the arrow 21, the shutter is closed about in position 25. About when the pocket passes the position 26, it is connected to a low vacuum conduit. The low evacuation is assumed to be completed in the position 27, where the pocket 22 is then connected to a high vacuum conduit and the vacuum is further increased. The heat-sealing of the mouth of the lining then takes place in the position 28. In the position 29 air is introduced into the pocket for two different purposes. Firstly the vacuum is released, so that the shutter may be opened for removal of the package, and secondly the heat-sealing joint is cooled for obtaining the required rigidity. In the position 30 the shutter is again opened, and in the position 31 the package is removed. For the removal of the package a second auxiliary carousel is used, transferring the package to a conveyor path 33.

FIGS. 3 and 4 show a pocket with a package 34 introduced therein, as seen in the direction inwardly through the open shutter. This package has, in a manner described already, been closed at the bottom, filled, and folded together at the mouth of the lining. The mouth has been welded together along the major part of the length, leaving the small part 17 unwelded.

In the pocket the package is retained in correct position by partly resting on a support 35, which is carried up in its turn by a guide 36, as seen in FIGS. 5 and 6. The package is also partly embraced by a pair of embracer arms 37, 38. The two closing flaps 13 and 14 at the short sides are folded outwardly, so that they do not prevent the continuous handling of the package. The closing flaps 12, 13 along the long sides of the package are folded down closely to their respective long sides, as shown in FIGS. 5 and 6. The guide 36- and the function of the embracer arms 37, 38 do not form a part of the present invention, and therefore only a short deseription thereof is given here.

When the package passes from the position 30 into the position 31 in FIG. 2, the guide 36, under the influence of means not shown in the drawing, moves outwardly, out of the open pocket 22, so that the support 35 together with the package 34 are displaced out of the pocket. During the later part of this movement, simultaneously with the package arriving at the position 31, FIG. 2, the embracer arms are opened for freeing the package. The package simultaneously embraced by a pair of corresponding embracer arms on the carousel 32, which thereafter moves the completed package along the path 33. During the movement of the carousel from the position 31 to the position opposite to the carousel 23, the pocket 22 is aired for receipt of a new package when it passes the carousel 23. This new package has been brought forward to the exchange position by first passing along the path 24 and thereafter being turned around by the carousel 23, in which it has been caught by a pair of embracer arms. The package is then caught by the embracer arms 37, 38, simultaneously as the embracer arms in the carousel 23 release the package, and immediately the support 35 is again displaced inwardly together with the guide 36. Thereafter the shutter 39 is closed for covering the opening of the pocket 22.

At this time the package assumes a position, in which the mouth is somewhat erected after the initial closing, as shown by 40, and the welded part is mainly upright. When the package is later subjected to evacuation by all of the pocket being evacuated, and gas or air leaves the package, and change of form takes place. Since the evacuation takes place primarily from the pocket, the air from the package escapes into the pocket through the opening 17, FIG. 1. In order that the packed material does not escape together with the air, the opening 17 is rather small, and the consequence is that during the proper progress of the evacuation an overpressure, relative to the pressure in the pocket 22, will exist in the interior of the package. This over-pressure can cause a change of shape in the package, particularly in the soft lining, thereby displacing the partly Welded mouth 17 from its proper welding position. Added to this is the fact that, when air is again let into the pocket 22, the pressure in the pocket will suddenly increase, thereby a practically explosive shrinking together of the lining to gether with its contents into a minimum volume. The packed material is now compressed so strongly, that it has a rather woodli'ke consistency.

With regard to these movements of the lining in the package it is utterly important, that the mouth of the lining is kept in an exact position relative to the welding blocks heat-sealing of the remaining mouth part 17. The character of the means provided for this purpose forms the object of the present invention.

The part of the mouth 16 shown at the right in FIGS. 1, 3 and 4 is supported by a support, applied in fixed relation in the pocket 22, and consisting of a border, for instance of rubber or similar material 41, which is kept in its place by means of a metal clamp 42. The clamp 42 is attached to the wall of the pocket 22 by means of a pair of screws 43. The clamp and the rubber border, of course, must be attached to each other and formed in such a Way, that they form an even surface against the lining edge 16 of the package. FIG. 6 shows these parts in section.

At the left end of the place of the lining edge in the pocket 22, the inner welding block 44 is provided. In order to insure good welding this is resiliently geared about a vertical, spring loaded shaft 45 attached to a holder 46, which in its turn, by means of screws 47, is attached to the wall of the pocket 22. Feed of current to the electrically heated welding block takes place by means of a pair of terminals 48. The character of this welding block will be described in connection with FIG. 7.

In the upper part of the pocket 22, a four-edge-shaft is provided for controlling the movable tightening means and the movable welding block, respectively. This four-edge-shaft is in rounded form carried through the wall of the pocket 22 as will be seen from FIG. 3, and outside of the pocket it is connected to a hub 51, which carries an arm 52, FIG. 6. This arm, which is only in part visible in the drawing, carries at its end, turned onto the interior of the carousel 20, a follower pulley in cooperation with a curve or cam disc, not shown in the drawing, by which the turning movement of the shaft in a given time will take place.

The curve or cam disc is formed in such a way, that its turning will take place in two different times. Immediately after the package has been introduced into the pocket 22, the shaft 50 is first turned an amount such that a rubber border will attack the edge 16- of the lining from the outside, the edge 16 of the lining being clamped between the two rubber borders 41 and 55. At a later time, after the evacuation is fulfilled, and the remaining part 17 of the edge 16 of the lining shall be heat-sealed, the shaft 50 is turned somewhat further, whereby a movable welding block 56 attacks the concerned part of the edge of the lining, and heat-sealing is provided.

The rubber border 55 is attached to the one arm 57 of double armed lever 5758, geared on a pin 59 in an arm 60, mounted on the shaft 50. At the outer end of the arm 60, a spring fixture 61 is provided, attached by means of a screw spring 62 to a pin 63 on the arm 58. Through a hole in the arm a setting screw 64 runs, which is limiting by means of its head the mutual movement between the arms 57 and 60'.

It will be evident from the above description, that when the edge 16 of the lining is not clamped, for instance during the introduction of the package 34 into the pocket 22, the arm construction 57-58-6t) is turned in such a way that the arms 57 and 69 stand right out in horizontal direction, whereas the arm 58 is directed upwardly, and consequently the now described arrangement will not act preventing for the introduction of the package 34 into the pocket 22. After the package has been introduced into the pocket 22, however, so that the edge 1617 of the lining is contacting the rubber border 41 and the welding block 42, a turning of the shaft 50 shall immediately take place, whereby the edge 16 of the lining is clamped. This turning, however, does not comprise full 90 but is stopped due to the form of the cam disc causing a turning movement of about Thereby the spring 62 has moved the pin 63 and the spring fixture 61 together, so that the arm 57 has been removed from the arms 60 as far as allowed by the setting screw 64. The consequence is that in this position, the rubber border 41 will attack the ridge 16 of the border, but the movable welding block 44 still is placed at a certain distance from the ridge of the border. Due to this no pressure will be applied against the part of the ridge of the border at 17, not yet closed. Thus there is a possibility for air to escape, so that when vacuum is created in the pocket 22, air will escape, and the package can be evacuated.

After evacuation heat-sealing takes place by plastic welding at the place 17 of the ridge of the border. The cam disc, controlling the turning movement of the shaft 50, thereby is formed in such a way that, at a suitable time, this shaft will describe the remaining part of its turning movement from the above indicated angular position of approximately 75 to fully 90. Thereby the welding block 56 is brought into contact with the mouth of the lining, but the rubber border 55 will not change its position in relation to the mouth of the lining, because the movement is received by the spring 62. Simultaneously electric current is fed to the two welding blocks 44 and 56, so that the mouth of the lining is closed along all of its length.

For securing good contact between the welding blocks 44 and 56 and the intermediate part of the ridge 16 of the lining, the outer welding block is mounted resiliently about a spring loaded pin 66. This pin 66 is geared in a holder 67 on an arm 68, which is, by means of a screw 69, attached to the shaft 50.

The shaft 50 is geared in ball bearings 70, 71. The bearing 70 is tightened against air entering from outside by means of a plate 72. A cuff-tightening 73 is provided inside of the ball bearing 71, for providing a corresponding tightening at the outside shaft end to the hub 51 and the arm 52.

The welding blocks 44 and 56 are made in a manner shown in FIG. 7. The active part of the welding block consists of a resistance band 76, running partly on the attacking side of the welding block and partly around its edge sides. The resistance band, at its one end, is attached to a terminal 77, which is carried by the piece 78 made of insulating material, and at its other end is carried by a part 80, which is attached to the piece 78 and hinged by means of the pin 79. Part 80 is in turn hinged on the pin 81. The part 80 in its interior, is provided with a conductor not visible in the drawing, connecting the end of the resistance tape 76 with the terminal 82.

Due to the resistance band 76 resting along the major part of its length against the insulation piece 78, and this is carried in a hiugeable way into directions perpendicular to each other by means of the pins 79 and 81, the welding block will obtain a setting of its own, so that a good surface contact and heating with the mouth of the lining will result, when electrical current is fed to the resistance band.

What I claim is:

In a means for heat sealing an edge of a substantially closed liner comprising a pocket, means for opening said pocket and inserting the liner to be evacuated and heat sealed, means for closing said pocket, means for evacuating said pocket when closed, and means for holding and heat sealing said liner in the pocket while said pocket is closed and evacuated, the improvement wherein said holding and heat sealing means comprises opposed support jaws pivotably movable between open and clamping positions disposed in said pocket at a position to receive between said jaws in their open position a previously sealed length of one edge of the liner, opposed welding blocks pivotably movable between open and clamping positions and disposed in said pocket in line with said support jaws at a position to receive between said welding blocks an open portion of said one edge of the liner, a common shaft on which at least one of said support jaws and at least one of said welding blocks are mounted in axial alignment, said shaft being rotatable through a predetermined number of degrees, and operating means for sequentially closing said support jaws and said welding blocks while said pocket is closed operable to first close said support jaws before the pocket is evacuated by rotation of the shaft through a portion of the predetermined number of degrees and then to close said welding blocks at the edge after the pocket is evacuated by rotation of said shaft through the remainder of said number of degrees, and heating means for heating at least one of said opposed welding blocks.

References Cited in the file of this patent UNITED STATES PATENTS 2,672,268 Bower Mar. 16, 1954 2,676,440 Campbell Apr. 27, 1954 2,692,074 Mueller et al. Oct. 19, 1954 2,778,177 Mahafiey et al Jan. 22, 1957 2,889,673 Rockland et a1. June 9, 1959 2,933,868 Graefingholt Apr. 26, 1960 2,966,019 Graefingholt Dec. 27, 1960

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