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Publication numberUS3910008 A
Publication typeGrant
Publication dateOct 7, 1975
Filing dateAug 20, 1974
Priority dateAug 20, 1974
Publication numberUS 3910008 A, US 3910008A, US-A-3910008, US3910008 A, US3910008A
InventorsJohnson H William
Original AssigneeSvenska Manufacturing Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Vacuum packaging
US 3910008 A
Abstract
A vacuum packaging system whereby upper and lower films are vacuum sealed about an article. The article to be packaged is placed on a lower film having upwardly extending projections. A vacuum is drawn about the edges of the film and an upper sealing film is positioned above the article and pulled tightly thereabout by the vacuum. The projections allow substantially complete evacuation of air from the enclosed article before the films become completely sealed together to form an airtight package.
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Description  (OCR text may contain errors)

United States Patent Johnson Oct. 7, 1975 VACUUM PACKAGING Primary Examiner-Travis S. McGehee I t H. W ll h V t If. [75] nven or I lam J0 nson en ura Cal Attorney, Agent, or FirmKenneth J. Hovet [73] Assignee: Svenska Manufacturing Corporation, Santa Rosa, Calif.

Filed:

[5 7 ABSTRACT A vacuum packaging system whereby upper and lower films are vacuum sealed about an article. The article to be packaged is placed on a lower film having upwardly extending projections. A vacuum is drawn about the edges of the film and an upper sealing film is positioned above the article and pulled tightly thereabout by the vacuum. The projections allow substantially complete evacuation of air from the enclosed article before the films become completely sealed together to form an airtight package.

8 Claims, 16 Drawing Figures [22] Aug. 20, 1974 [21] Appl. No.: 499,051

[52] US. Cl. 53/112 A; 53/141 [51] Int. Cl. B65B 31/02 [58] Field of Search 53/22 A, 112 A, 141

[56] References Cited UNITED STATES PATENTS 3,449,886 6/1969 Connelly et al 53/22 A X 3,830,365 8/1974 Krueger et al. 53/22 A X US. Patent 00. 7,1975 Sheet 1 of 4 3,910,008

US. atent Oct. 7,1975

Sheet 2 of 4 FIG.8

U.S. Patent Oct. 7,1975

Sheet 3 of 4 3,910,008

mmlw" I 8 U.S. Patent Oct. 7,1975 Sheet 4 of 4 3,910,008

VACUUM PACKAGING BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packaging system and, more particularly, to the vacuum sealing of an article between packaging materials.

2. Description of the Prior Art Numerous techniques have evolved over the years for packaging products between films, or against a cardboard backing or within a pre-shaped container. For example, US. Pat. No. 3,377,770 discloses a skin packaging apparatus whereby a porous base pad is placed over a vacuum platen and a product is placed thereon. Plastic sheet material is heated and stretched tightly over the product by drawing a vacuum through the porous base pad. This process requires numerous manual manipulations and is not suitable for high volume packaging. Additionally, it is not suited for products which are desirably maintained in an airtight condition inasmuch the porous base pad will allow air to pass back into the package.

US. Pat. No. 3,634,993 to Pasco et al. provides a technique for sealing a product between a pair of films by placing the product on a bottom film which is on a heated reciprocable platen. A vacuum is pulled about the periphery of the platen while it is moved into seal ing engagement with an upper chamber having an upper film stretched thereacross. when the films contact each other, the vacuum is released and air is injected above and below the films to push out any air lingering about the product. The two films become heat sealed together to form an airtight package.

The above sequence of steps is substantially similar to that shown in US. Pat. No. 3,491,504 wherein movable platens and dome-like chambers operate in conjunction with sequential vacuum and air injections to pull and push, respectively, the films tightly against a product.

An inherent disadvantage with the prior art systems is the fact that when a vacuum is drawn from between upper and lower films, ambient air adjacent the edges of the films is removed first. As a result, the films have a tendency to become sealed together at their periphery before the interior of the package can be evacuated of air. Residual air, of course, can be highly deleterious to various types of food products. To compensate for this, packagers have used the aforementioned air injections, or they have injected nitrogen into the package to displace the harmful air or they have used preformed films to minimize the interstitial space about the product. The air injection technique requires the films to be sealingly enclosed between a chamber and platen means so that the pressurized air will operate to push against the films and expel any air trapped about the product. Unquestionably, such techniques require an unnecessary number of process steps, they require high capital costs in equipment, they are inefficient, time consuming, and are generally unsuitable for assembly line operation.

SUMMARY OF THE INVENTION In accordance with the present invention, an. improved packaging system is provided whereby a substantially complete excavation of air from a package can be obtained with a simplified highly efficient apparatus. This is accomplished by providing a multiplicity of projections extending toward the interior of a package on at least one of the wrapping films.

In general, the invention contemplates the placement of a bottom film on a vacuum plate having vacuum ducts adjacent the film periphery. An article is placed on the film and a transfer housing moves an upper film over the article. Air is drawn through the vacuum ducts from the periphery of the bottom film to remove air from about the article. The evacuation of air continues during the downward movement of the upper film and after the upper and lower films contact each other. This is possible because of the passageways formed between the inwardly extending projections and the upper film. The removal of air continues until substantially all air is removed from about the article and the films become tightly drawn against each other.

A permanent airtight package results when the portions of the films that overlap the periphery of the article become sealed to each other. A suitable seal may be effected by heat, in which case the films comprise a heat sealable composition and the transfer housing and/or vacuum plate is provided with means for heating the films. Alternatively, a seal may be effected by coating at least one of the films with an adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view ofa packaging apparatus constructed in accordance with the present invention;

FIG. 2 is a side elevation view of the apparatus of FIG. 1;

FIG. 3 is an end elevation view taken along the line 3-3 of FIG. 2;

FIG. 4 is an elevation sectional view taken along the line 44 of FIG. 2;

FIG. 5 is a perspective view partially broken-away of the upper sheet transportation assembly of the apparatus of FIG. 1;

FIG. 6 is an elevation sectional view taken along the line 6-6 of FIG. 3;

FIG. 7 is an elevation sectional view taken along the line 77 of FIG. 3; a

FIG. 8 is an end elevation view taken along the line 8-8 of FIG. 2;

FIG. 9 is a side elevation view partially broken-away taken along line 9-9 of FIG 8;

FIG. 10 is a broken-away perspective view taken along line 10-10 of FIG. 9;

FIG. 11a is a vertical sectional view ofa modification of the vacuum plate of the apparatus of FIG. 1 showing vacuum duct shields operating in conjunction with a bottom film;

FIG. 11!) is a top plan view of the vacuum plate of FIG. 11a without a bottom film;

FIG. 12 is a modification of the bottom sheet-forming assembly shown in FIG. 1;

FIG. 13 is an enlarged scale broken-away partial sectional side elevation view showing the apparatus of FIG. 1 in operation; I

FIG. 14 is a sectional view taken along line 14-14 of FIG. 13; and,

FIG. 15 is a plan view taken along line 15-15 of FIG. 14.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and, more particularly to FIG. 1 thereof, a perspective view of the overall packaging apparatus is shown. This view includes an adjunct embossing assembly 12 for impressing projections onto a plain surfaced material for use as a bottom wrapping film. The assembly is readily detachable and may be operated as a separate unit for producing a packaging film in large quantities and stored in rolls for later use.

In general. the primary elements comprising the packaging apparatus of the present invention include support means shown generally as 90 and 94 in FIG. 1, vacuum plate means 14, a movable housing 18, and a film transfer means 22. An upper sheet transportation assembly is a desirable element of the invention, but its use is optional depending on how the apparatus is operated.

The support means preferably comprises two sections 90 and 94 located at opposite ends of the vacuum plate means 14. Both sections are elevated to a position about level with the top surface of vacuum plate 14. The first section 90 comprises a belt 130 mounted between end roller 132 and secondary drive roller 134. An intermediate plate 133 is used to provide support for the belt between the rollers 132,134, however, idler rollers could be utilized equally as well. It is desirable to provide an underlying support for the belt at this location since such area is convenient for the placement of articles to be packaged. An article to be packaged will preferably be placed on the bottom film 38 as it is drawn in the direction shown by arrow A in FIG. 2. Of course, it is desirable to rotate the belt 130 at the same speed the film is drawn through the apparatus.

The second support section 94 includes pressure roller 104 and a multiplicy of rollers 97a,b,c, mounted across the top of opposing sidewalls 13:1,!) of frame housing 15. The second section will be described in detail hereinafter, however, it is to be understood that an endless belt conveyor, paddle or flight conveyor, chain mounted clamping means, hook means or the like would work equally well. It is contemplated that this section will support the sealed package prior to its removal for packing or, in the case where the bottom film is continuous. its conveyance to the cutting station 112. As such, the specific support means used will be dictated by the type of article being packaged, its size, weight and structure.

Located between the first and second support sections is the vacuum sealing station shown generally as reference numeral 92. At this location an article is vacuum sealed between an upper and lower film. Such occurs when housing 18 moves a film over a product located on an embossed film situated between fluid pas sageways 32 on a vacuum plate 14. In the preferred embodiment, the housing comprises a continuous conduit formed into an openwork such as the rectangularsh'aped housing frame 19 shown in FIGS. 1, 2, 4 and 14. The frame 19 has a bottom edge 44 which is constructed to sealingly impinge an upper film against the vacuum plate radially outside the vacuum plate passageways 32.

Also included with the housing assembly 18 is heating means 80 and heat shield 21 (see FIG. 4), The heat shield surrounds the heating means and operates to reflect and/or contain heat emanating from the heating means. The heating means may comprise one or more banks of conduction, radiant and/or convection type heaters such as for example, hot air units, infra-red lamps or electrical resistant units.

The housing assembly is connected for movement to reciprocation means 24. This reciprocation means includes a pneumatic or hydraulic cylinder and piston arrangement which is secured to stationary frame plate 23 which, in turn, is affixed to the basic apparatus frame structure shown as reference numeral 10. The reciprocation means 24 is located between cross plates 27 which are secured to a movable overhead support frame shown generally as 26. The support frame reciprocates within the basic frame structure on roller devices 23. The roller devices are affixed to cross beams 31 of the basic frame structure. Movement of the housing is guided and stabilized against rocking by four guide bars 29 which slide against the cross plates 27. The guide bars are secured to plate 25 and extend vertically therethrough.

Communicating with the conduit interior of frame 19 is fluid conductor 28. The conductor is connected to a valve and a means for supplying a vacuum to the interior of the conduit. The valve and vacuum means, being conventional, are not shown. The bottom edge portions 44 of frame 19 are provided with passageways 46. These passageways may take the form of slots, orifices or the like and are arranged to contact and retain by vacuum an upper film placed adjacent thereto either manually or by an upper sheet transportation assembly such that shown generally by reference numeral 16.

The upper sheet transportation assembly 16 comprises a carriage frame which is adapted for supporting a top film and moving it from a first position shown in phantom in FIG. 4 to a second position beneath housing 18, also shown in FIG. 4. To accomplish such movement the carriage frame includes a rectangularshaped vacuum frame 52 formed from a continuous hollow conduit and a set of spaced apart matching rollers. The top surface of the conduit contains fluid ducts 54 in the same manner as frame 19 and may conveniently be a mirror image of the bottom portion 44 of housing frame 19. The purpose of having the vacuum frame 52 correspond in shape to the housing frame 19 is to facilitate the transfer of a top film from the vacuum frame when its positioned beneath the housing frame. The interior of the conduit of vacuum frame 19 is in communication with fluid conductor 55 which, in turn, is connected to a vacuum source (not shown). A top film is held to the top surfaces of vacuum frame 52 by excavating air from ducts 54 through the vacuum frame conduit 52 and conductor 55. The film is situated on the vacuum frame in a manner to overlap the ducts such that a pressure differential will be created and atmospheric pressure will push the film against the regions of lower pressure about the ducts beneath the film.

It is to be understood that single precut top films may be manually positioned adjacent the bottom 44 of frame housing 19 or manually placed upon the vacuum frame and transported into the vacuum sealing section or, as shown ,in FIG. 4, predetermined lengths of film shown as 61 in FIG. 4 may be pulled into the sealing section from supply roll 60. To accomplish the latter alternative, the supply roll rests by gravity on idler rollers 62 so that when the carriage frame moves into the vacuum sealing section, the roll will freely rotate and allow the requisite amount of film to be withdrawn. A vacuum of 15 inches of mercury or more at ducts 54 creates sufficient pressure differential across the top film 61 to overcome any frictional resistance to the rotation of the supply roll and prevent the film from slipping off the vacuum frame. It is desirable to have the ducts, slots, orifices or the like located about a major portion of the top surface of the vacuum frame periphery so as to uniformly hold the top film and prevent creasing or wrinkles.

In some instances, such as when a full heavy supply roll is being used, it has been found desirable to use supplementary retention means 58. This may take the form of a pair of pneumatic or hydraulic operated plungers 48 mounted on frame 50. The plungers reciprocate up and down as shown by arrow B in FIG. 4. In the down position the plungers contact the film 61 and press it against the top surface of the vacuum frame. Additionally, it may be desirable to provide the vacuum frame with a center plate, shown as 57 in FIG. 5. This is to provide a flat support area for the film and prevent it from sagging at its midpoint. The plate will also facilitate the positioning of single precut films over the frame when such are used.

To provide for movement of the carriage frame, a lower offset portion 59 is utilized in conjunction with a roller assembly shown generally by reference numberal 63 in FIG. 5. In the embodiment shown, the roller assembly includes two pairs of spaced-apart upper rol- Iers 66,67 mounted for rotation above frame portion 59 and on opposite sides thereof. Two pairs of spacedapart lower rollers 68,69 are mounted beneath frame portion 59. Each of the lower rollers are positioned directly beneath a corresponding upper roller and -are spaced therefrom a distance sufficient to engage a pair of opposing tracks 70 which are affixed to the top edge portion of support angles 71. Preferably, tracks 70 are in the shape of a rod and the upper rollers 66,67 presem a concave circumferential surface. In this manner, the frame will be effectively guided and maintained in position during its traverse to and from the aforementioned first and second positions. Note also that rollers 68,69 engage the underside of angles 71 thereby preventing forward tipping of the carriage frame.

Movement of the carriage frame along the track is accomplished by carriage drive means 72. As shown in FIG. 4, this includes a cylinder 75 which pneumatically or hydraulically moves an internal rod and piston assembly (not shown) which is connected to drive chain or wire 73. Attached to the wire is connector 74 which is also secured to the bottom of the carriage frame. In this way hydraulic or pneumatic force from drive means 72 is transmitted through the wire 73 and connector 74 to frame 50 thereby causing the movement thereof along track 70. Mechanical eccentric means, electric drive means or various combinations of each could also be used for the drive means of the present invention.

An advantage of the above-described system is that it is substantially trouble-free and can very easily be adjusted for different stroke lengths. For example, differ ent sized products will require different lengths and/or widths of top film to be pulled into the sealing section 92. As such, it is a simple matter to adjust either the distance the wire 73 and connector 74 move or the position of the connector on the wire.

When carriage frame 50 is in the second position, a film cutting mechanism shown generally as 78 in FIG. 6 is activated to sever the film. The severing occurs only after the film has been released from vacuum frame 52 and retained on the lower edge portions 44 of housing frame 19 and the vacuum frame retracted back to its first position. the cutting means 78 may be a hot cutting wire shown as 79 in the preferred embodiment or rotary cutters or conventional knife means known in the art.

When the carriage frame has been retracted to its first position, the cutting mechanism'is actuated causing fluid to enter cylinders '84 and effect the downward movement of shafts 84. Opposite ends of resistance wire 79 are secured to shafts by ceramic connectors 83. The lowermost position of the cutting wire 79 after it has passed through film 61 is shown in phantom in FIG. 6.

After the film 61 has been severed, housing 18 will reciprocate to a lower position to sealingly engage the vacuum plate 14. In a preferred embodiment of the present invention, the housing 18 is provided with the aforementioned heating means 80. The heating devices are conveniently mounted on shield 21 so that the upper film will become more efficiently softened by both reflection and convection currents.

As illustrated in FIG. 15, an essential feature of the present invention is the position of the top film 61 and housing frame 19 relative to fluid passageways 32 and the side edges of bottom film 38. The passageways 32 are in communication with fluid conduits 34 which are connected to a vacuum source (not shown). It is important that the passageways 32 remain unobstructed during the sealing process so that the evacuation of air may be as complete as possible from the package. In part, this can be accomplished by locating the passageways proximate the side edges of the bottom film and preferably beyond the periphery thereof shown in FIGS.s l4 and 15. Alternatively, shields shown as 42 in FIGS. 11a and 1 117 may be used to maintain the passageways open when wide bottom films are used or to prevent in advertent misplacement or misalignment of the bottom film from obstructing the passageways.

The passageways 32 are shown as slots in the drawings but couldjust well be a series of orifices or other type of duct. The passageways should be located substantially parallel to the side edges of the bottom film to produce the most effective air evacuation from the region between the packaging media. It is essential that there should be at least one passageway on the vacuum plate, but preferably two should be used adjacent each opposite side edge of the bottom film to effect a balanced evacuation of air. This is advantageous because it provides a quicker and more thorough removal of air. It also facilitates a more balanced vacuum draw of the top film over the item to be packaged and it produces a more uniform wrinkle-free bond between the films at their interface about the periphery of the item.

It is to be understood that the vacuum plate 14 can be removed and exchanged for a plate having passageways and/or templates or the like located in different positions to accommodate various types and sizes of products. Of course, the configuration of housing frame 19 could likewise be changed to accommodate the different products and conform to the changed vac uum plate. It is important, however, that the bottom edges 44 encompass the fluid passageways 32 to form an effective seal against the vacuum plate in a manner to be hereinafter described.

As advantageous aspect of the present invention resides in the use of an integral continuous bottom film conveying system operable with a unitary drive means. In general, the system comprises a drive means, shown generally 22 in FIG. 8, the previously described first and second support sections, a drive roller 104, and a pair of friction wheels 96. The wheels operate to frictionally engage the flattened side portions of the completed package at the nip between the wheels and drive roller. Since the bottom film is continuous, fresh film will be drawn from a storage roll or from the embossing assembly through the apparatus is an amount equal to the distance each successive package is moved. The amount of rotation is predetermined so that the appropriate amount of film will be drawn into the sealing section to adequately cover the product being packaged. It is to be noted that due to the inherent resilience of the packaging films, a package will be pushed downstream from the friction rollers as it passes therethrough into the cutting and unloading zone.

To provide the necessary pressure adjustment on the wheels 96 for effectively frictionally engaging the package periphery, the friction wheels are mounted on pivot arms 98. Downward pressure of the friction wheels against drive roller 104 is effected by adjustment of threaded bolts 106. As the bolts are screwed down against housing plates 107, their offset position on arms 98 causes the arms and wheels to rotate counterclockwise against the drive roller. It is to be understood that opposing clamp means reciprocating on a track would work equally as well as a means for moving the bottom film and packages through the system.

In the preferred embodiment the drive means 22 of the bottom film conveying system includes pneumatic cylinder 116 having a rod 120 pneumatically reciprocated therein. Attached to the top of the rod is bracket 1 I8 which is secured to connector plate 124. The plate links together the ends of primary drive chain 122. The drive chain engages the teeth of idler sprocket 130 and drive roller socket 132. The drive roller socket is equipped with a conventional ratchet mechanism such that the drive roll 104 will be power driven only in the direction shown by arrow C in FIG. 9.

Located on the opposite end of drive roll I04, sprocket I35 transmits the rotational force thereof, through chain I21 to the auxiliary rollers 97u,b,c. (See FIGS. 2 and I3). Roller 970 is equipped with a double sprocket I40 so that the rotational force of roll 104 will be further transmitted by chain I23 to a sprocket 139 on the end of secondary drive roller 134. As previously described, the secondary drive roller I34 functions to rotate belt 130 of the first support section.

It can be seen that the above drive system provides a highly advantageous unitary means for not only moving a bottom film and package through the packaging apparatus, but it also drives the cooperating supplemental conveying means embodied in the two support sections. The drive system also imparts a high degree of versatility to the conveying system of the present invention in that different sized sprockets may be used to effect variable ratios of rotation to slow down or speed up the rollers and/or belt. Of course, the system can be operated intermittently without the conveying system to individually package items.

Referring now to the package severing means 112 (see FIGS 1, 9 and located immediately downstream from the friction wheels, the use of a movable hot wire system is shown. This system consists of a thin resistance wire 142 connected at opposite ends to a eeramie adaptor 141 which is mounted on bracket 144. The bracket is provided with a roller assembly adapted to engage and roll against a side portion of support housing 15 adjacent slot 146. A pair of guide rollers 152 are mounted on the lower inner face of the bracket and are positioned to slide along the inner edges 153 of slot 146. A transverse support roller I54 Slides along the outside sidewalls of housing 15 adjacent the slot 146. Bracket 144 is secured to cross plate 156 which is reciprocated up and down by lift devices 158. When a package formed from the continuous bottom film 38 reaches the unloading zone 160 (see package M in FIG. 13), the lift devices are actuated to move the hot wire through the film.

Continuing on the optional bottom sheet-forming assembly shown generally by referene numeral 12 in FIGS. 1 and 2 and schematically in FIG. 12, a supply roll 201 is shown having a plain flat film drawn therefrom over a portion of vacuum drum 206 and across tension roller 205 into the apparatus shown by arrow D. The drum surfaces are provided with a series of orifices 204 such that after the film has been heated, either by internal means within the drum or by auxilliary heating means 208, the film becomes pliant and can be partially drawn into the orifices on the face of the drum. Upon cooling, the film will have a series of projections spaced throughout its surface. The optional heating section of the drum is shown by reference numeral 210 and the vacuum section is shown by numeral 212.

Alternatively, it is within the purview of the present invention to utilize a mechanical device for creating a series of projections on the bottom film. This may be accomplished by passing a film through the nip ofa pair of rollers 214, 2l6one of which has outwardly extending projections 218 that engage matching recesses 220 on the opposing roller. The film may be optionally heated by heated rollers or external means as it passes through the forming device.

The advantage of the mechanical device is that it is simpler and presents no problem of the film becoming overheated due to the sequential operation of the apparatus.

As previously mentioned, it may be convenient to have the projections formed in the bottom film in a separate operation and stored in rolls. In such case, the embossed film would simply be substituted for roll 201 and fed directly into the apparatus.

To obtain a better understanding of the method of the present invention reference should be made to FIGS. 13, I4 and 15. In FIG. I3 products being packaged in a sequential manner on a continuous bottom film are shown schematically by letters M, N, O, and P. To begin operation, the bottom film with its projections directed upwardly is pulled through both the first and second support sections and the sealing section, and inserted between the nip of wheels 96 and drive roller 104. Similarly, an upper film is placed over the vacuum frame 52. The vacuum source is opened such that when the machine is activated, a predetermined sequence of events will occur.

With the vacuum source in communication with conduit 55which is opened by conventional valve means (not shown). air will be removed'from the vicinity of ducts 54. The resultant pressure differential will function to retain the top plastic film about the perimeter of the vacuum frame. Additionally, the supplementary retention plungers 48 may be activated to press the film against the vacuum frame to further prevent the film from being twisted or slipping off the frame. An electronic control means activates carriage drive means 72 to move the carriage assembly from the first position shown in phantom in FIG. 4 to the second position beneath the housing 18. At this point the hold-down plungers 48 are released and the vacuum to the frame 52 is shut-off. Simultaneously a vacuum source is placed in communication with fluid conduit 28 and housing frame 19. Air is evacuated through orifices 46 and about the bottom edge portion 44 such that the top film will be released from the vacuum frame 52 and become pushed by pressure differential against the bottorn edges 44 of the housing frame. Note that the second position of the carriage assembly facilitates this in that it extends to a location substantially directly beneath the housing and in close proximity to the lower edges 44.

After the housing has received the top film 61, the carriage drive means 72 operates to return the carriage frame to its first position. Immediately after this has occured. top film severing means 78 is activated to move a hot wire through the film and sever it completely. The housing is now ready to move to a lower position upon the vacuum-sealing plate 14. Of course the above sequence could be eliminated by simply manually placing a precut sheet of film into place against the edges 44. Such may be more convenient when packaging separate or unusual items rather than a large number of similar articles where speed and high volume are not the criteria.

About the time the severing means 78 is operated heaters 80 are activated so that the upper film is being warmed into a pliant or formable state. This occurs a result of the heating action of the heating means located within the housing and beneath shield 21. Depending upon the type of heaters being used, it may be preferable to leave them on continuously.

Before the housing descends to a lower position, a vacuum source is placed into communication with conduits 34 and passageways 32. At this point it will be recalled that the dimpled film has been stretched across the vacuum sealing plate 14 and is located between the passageways 32 as shown in FIGS. 14 and 15. Note that an article of manufacture, a meat product, a foodstuff, or some other type of product designated has been placed upon the embossed bottom film. This preferably occurs at the first support means located which has now been sequenced into the vacuum sealing section.

As the housing [8 descends over the product, the top film being in a softened state and secured about its periphcry by vacuum, stretches over the product while the housing continues its downward movement. Simultaneously. air is being evacuated from the edges of the embossed bottom film. As the top film continues to be lowered air is removed from the area shown as 90 in FIG. 14. This is defined as the region below the upper film and within the perimeter of the area of sealing engagement between frame portion 44 and the vacuum plate. With the present invention. evacuation of air continues even after the top film has made initial contact with the top surfaces of the projections of the bottom film. This occurs through the interstices between the projections as shown by the arrows in FIGS. 14 and 15.

After substantially all the air is removed, it is believed that the somewhat resilient projections become collapsed due to the pressure differential between the atmosphere and the reduced pressure between the films. At this point the top film Commences to bond with the bottom film at the annular area of their overlap about the product periphery. Alternatively, depending on the type of product being packaged, it may be desirable to heat the bottom sealing plate to enhance the seal. However, this is entirely optional and not necessary or even desirable in some cases.

After the top film has been tightly stretched over the product and sealed about the product periphery, the vacuum source is shut-off to both the vacuum plate and housing 18. The housing reciprocates back to its upper position and drive means 22 is actuated to transport the package from the vacuum sealing section to the second support section. It is contemplated that the sealing process is taking place, an operator will be placing another product, shown as P in FIG. 15, upon the bottom film at the first support section. Therefore, it can be seen that product P will be drawn into the sealing section product 0 is pulled to the second support section.

As successive products are placed onto the bottom film, a continuous chain will be formed until the bottom film is severed. Since the :sealing process requires a certain period of time, newly formed packages will have a brief dwell period, corresponding to the sealing time, in which the films may cool. The package will then be alternately pulled and then pushed between wheels 96 and roller 104 to an unloading area denoted by reference numeral 160. At this point the package shown M will be severed from the continuous bottom film by severing means 112 and removed for final stacking, storage and/or shipment.

Note that with the present invention there is no airtight chamber required above the upper film 61. A seal is formed about the periphery of the housing 18 at edges 44 the housing engages the upper film and presses it against the surface of the vacuum sealing plate 14. To enhance this seal a resilient gasket shown at 92 in FIG. 15 may be provided on the vacuum plate to engage frame portion 44. When the housing engages the bottom film radially outward from passageways 32 and presses it against the vacuum plate or gasket (and transverse portions of the bottom film if such is continuous), all air contained within region will be evacuated. When the pressure differential is great enough to overcome the inherent resilience of the upwardly extending projections and cause: their collapse and/or cause the upper film to flatten against the bottom film, an airtight seal will be formed. Because of the seal delaying action caused by the projections, the interstitial air evacuation passageways formed thereby, and the fact that air is being removed from opposite sides of the package, it can be seen how the present invention produces a tightly sealed package with substantially all air removed.

Of course, the type of film, its resilience andability to stretch are important. The films are preferably of a thermoplastic material such as 'Surlyn or various thermoplastic coated laminates such as polyethylene, cellulose acetate, polyethylene-regenerated cellulose, regenerated cellulose films, rubber hydrochloride films,

polyvinyl films or metallic laminated foil films having a thermoplastic coating. Plastic or adhesive-coated embossed members whether they are rigid or semi-rigid, could be substituted for the bottom film. Note that with the present invention substantially any configuration or arrangement of projections may be utilized on the bottom packaging material. Hemispherical protuberances are shown as uniformly spaced about the surface of the bottom film in the drawings of the preferred embodiment. However, the projections may take the shape of pyramidal protuberances, straight or zigzag ridges, or any other design providing a number of intersticies between which air may be drawn.

it should be noted that the closer together the projections, the less susceptible they are to flattening by the pressure differential during evacuation and sealing. Similarly, the more resilient and/or the closer together the projections, the more thorough will be the excavation of air about the product. However, the material or projections should not be too rigid to prevent a final seal to occur with the top film. Of course, due to the preferred softening of the upper film, this would be an uncommon occurrence. in this regard, reference is made to the disclosure of US. Pat. No. 2,778,171

which discloses the use of various types of film projections and packaging materials to facilitate the evacuation of air from a pouch. To the extent of utilizing various types of projections and packaging materials, this patent is hereby incorporated by reference.

The present invention is particularly suitable to the packaging of food products wherein packaging materials having a relatively low air or oxygen permeability should be utilized. in this regard, substantially impermeable films may be coated with heat activatable adhesives and utilized. Examples of such would be the use of a polyethylene film with a coating of ethylene vinyl acetate. Such a film when heated will allow the tight bonding and sealing of upper films to lower films. Of course, a film must be chosen that will stretch and draw down over the shape of the product being packaged without being disproportionately stretched, weakened or torn.

As mentioned previously, the present apparatus operates sequentially with the dwell period between movements being conveniently dictated by the time required to seal the product at the vacuum sealing section. This may be automatically controlled by timer means and electrical circuitry which coordinates the activation of the carriage frame movement and the housing means movement together with the vacuum conduit openings and closings.

Although pneumatic or hydraulic means have been shown to drive the carriage frame, housing and support means, electric motors, cam mechanisms or the like, operated by solenoid devices would work equally well. Likewise, a central vacuum source may be utilized in conjunction with the sequential operation of valves in the various fluid conduits connecting the various outlets at the appropriate time.

While the invention has been described with respect to a specific embodiment, it will be apparent to those skilled'in the art that various modifications and improvements may be made without departing from the scope and spirit of the invention. Accordingly, it is to be understood that the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims.

I claim:

1. in an apparatus for packaging articles between an upper and lower sheet comprising;

vacuum forming means;

a vacuum base member supported by a frame, said base member including passageways in communication with said vacuum forming means, said passageways being open at predetermined locations on said member proximate peripheral portions of a lower sheet placed thereon;

a lower sheet conveying system comprising drive means engagable with said lower sheet at a point downstream from said vacuum base member, and sheet support members located along the path of travel of said lower sheet adjacent said vacuum base member; and,

a movable housing mounted above said base member on said frame including means to reciprocate said housing between an upper position and lower position, and including heating means and upper sheet retaining means operating in response to the position of the housing, said housing being adapted to substantially sealingly engage said base member radially outward from said passageways.

2. The apparatus of claim 1 including sheet cutting means located downstream from said drive means to sever individual packages from said lower sheet.

3. The apparatus of claim 1 including an upper sheet transportation assembly adjacent said housing assembly including a carriage means for carrying the upper sheet of packaging material from a first position to a second position beneath said housing when said housing is in the upper position, retention means on said carriage means for releasably retaining said upper sheet on said carriage means, and means for moving said car riage means from said first position to said second posi tion.

4. The apparatus of claim 3 wherein said upper sheet retaining means and the carriage retention means comprise vacuum ducts in communication with the vacuum forming means and located about the sheetcontacting portions of said housing and carriage means.

5. The apparatus of claim 3 wherein said upper sheet is initially in a continuous roll, including sheet cutting means located between said carriage means and said housing and activated to cut individual sheets from the continuous roll when said carriage means is in the second position.

6. the apparatus of claim 5 wherein said upper sheet transportation assembly includes secondary retention means mounted on said carriage means for securing said upper sheet against slippage during movement from said first position to said second position.

7. The apparatus of claim 1 including control means comprising:

means to activate said upper sheet retaining means for retaining the upper sheet on said housing;

means to activate the movement of said housing from said upper position to said lower position; and,

means for activating said heating means at least during the period said housing moves from said upper position to said lower position.

8. The apparatus of claim 3 including control means comprising:

means to cause said upper sheet retaining means to retain the upper sheet upon said housing;

13 14 means for activating said heating means at least durmoved to said first position; and,

8 the Period Said housing move-S from Said pp said control means further including means to conposition to fi l position; trol the time said housing is in said lower position means for activating the movement of said carriage means between said first and second positions; and means to aqnvate Swd dnve means when Sald means to activate the movement of said housing to housing moves said pp Positionsaid lower position after said carriage means has

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Classifications
U.S. Classification53/509, 53/141, 53/511
International ClassificationB65B11/52, B65B31/02, B65B11/50
Cooperative ClassificationB65B11/52, B65B31/02
European ClassificationB65B11/52, B65B31/02