Packing machine

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Patent issued

01/12/1993

Inventor(s):	Norris, Jeffrey A. Jones, David
Assignee	Pilkington Insulation Limited ()
Application	No. 07/687,320 filed on 04/18/1991
Current US Class	53/433, 53/439, 53/450, 53/511, 53/529, 53/550
Field of search	53/87, 53/138.4, 53/405, 53/427, 53/432, 53/433, 53/439, 53/493, 53/450, 53/451, 53/511, 53/529, 53/530, 53/550, 53/551, 53/552
International Classes:	B65B 6302
Examiners
Primary	Sipos John
Secondary	Moon Daniel
Attorney, agent or firm:	Davis, IV; F. Eugene
US patent references	3274746, 3381440, 3458966, 3546846, 3837138, 4084390, 4106262, 4223508, 4251975, 4272944, 4537016, 4592193, 4727707, 4757668, 4964259
Foreign patents	0131475 (12/31/1984, EP), 2347259 (10/31/1977, FR), 2125760 (02/29/1984, GB)

A packing machine for wrapping compressed insulation products in heatsealable plastic film, including a forming tube having product feed meansto move or hold the product within it, a former to reconfigure a web ofheat sealable plastic film into a longitudinally open tube around theforming tube, a heat welder to close the longitudinal opening and providea continuous plastic tube, take-off conveyors which receive the plastictube containing the product at a point downstream of the forming tube anddisplace the product a preset distance from the forming tube to create apocket, means to close the plastic tube behind the displaced product andahead of the next product which is fed into the forming tube as theproduct is displaced, and means to cut the plastic tube between the twoclosures so formed, characterised in that air is removed from the pocketbefore closure by applying vacuum, thereby reducing the time for closingthe plastic tube. The invention also encompasses a method of using thepacking machine.
BACKGROUND OF THE INVENTION
This invention relates to packing machines, particularly to thermalinsulation packing machines and to the use of such packing machines topack pre-compressed rolls of thermal insulation.
Thermal insulation such as glass fibre or rock wool is produced in the formof a continuous mat or web which is cut to lengths and may be compressionrolled on a machine such as that described in European Patent No. 131475.That machine ensures that the compressed roll is prevented from unwindingby applying a sheet of paper around the curved surface of the cylinder. Toprevent loss of fibres or damage to the roll so formed, it is usual towrap this compressed cylinder in polythene. To do this the roll istransferred to a packing machine which first aligns the roll with the webfrom a large roll of polythene and then leads the edge of the polythenearound the roll of insulation. Nominally only one length of insulationcylinder can be wrapped by such a machine, which leads to the need to havemultiple machines when production needs to be switched from one type ofinsulation product to another having a different length. Furthermore, theexposed ends of the polythene need to be clipped to seal the package andin the known process this clipping operation requires the excess polytheneto be gathered by rotating the entire roll and package slowly pastgathering brushes and then applying the clips simultaneously to each endof the pack. The main drawbacks of this system are that the process isslow. Also it is not easy to get the polythene to wrap tightly about theinsulation roll, which gives rise to ballooning of the package. This isboth unsightly and costly because it could entail the product taking upmore room during storage and transport. The slow speed of operation meansthat several such machines have to be used to take the output of a singlecompression rolling machine and this is expensive and wastes valuablefloor space.
Insulation packing machines are also known in which the polythene wrappingmaterial is welded into a continuous tube longitudinally around theinsulating material. Such a machine is described in GB patent applicationNo. 2125760A which is primarily for wrapping stacks of insulation in slabform. The machine compresses the slabs between two conveyors which feedthe compressed insulation into a welded plastic tube. The tube is formedfrom a special double folded roll of polythene. Because the insulationwill ultimately be held in compression by the polythene tube itself, it isnecessary to allow the longitudinal heat weld to cool and strengthenbefore the conveyors can actually deliver the insulation into afree-standing tube of plastic. This makes the process cycle timeexcessively long. In one version of this machine, transverse heat weldsare made between the stacks of insulation slabs. To make such welds thepolythene must be gathered between two bars and to prevent overstretchingof the polythene during this gathering, the insulation pack that isalready inside the tube with its remote end sealed, must be free to movebackwards. Thus, the excess tube length is created in the void between thetwo stacks of insulation slabs by removing the half sealed pack to alarger distance than is required for it to clear the transverse heatwelding equipment and then allowing it to move back nearer to that minimumclearance. This extra movement slows the process considerably because thehalf sealed pack can only be removed at the rate that continuous tube canbe formed by the longitudinal welding around the compression conveyors,and whilst in principle more heat could be applied, this would in practicecause overheating and increase the time that the weld would have to beallowed to cool before the process cycle could continue. A furtherdisadvantage of this process is that air is trapped in the tube areabetween the two stacks of slabs and tends to be compressed when the volumeis reduced by application of the gathering bars and backward motion of thehalf sealed pack. This air causes ballooning of the pack which is thenpartially eliminated when the pack and contents are removed from theeffect of compression due to the conveyors above and below the pack. Itwill be appreciated that such over-compression is undesirable because itdamages the insulation, particularly if it is glass fibre insulation.Furthermore, it is difficult to apply such compression to a roll which issheathed in paper.
SUMMARY OF THE INVENTION
According to the present invention a packing machine for wrappingcompressed insulation products in heat sealable plastic film, includes aforming tube having product feed means to move or hold the product withinit, a former to reconfigure a web of heat sealable plastic film into alongitudinally open tube around the forming tube, a heat welder to closethe longitudinal opening and provide a continuous plastic tube, take-offconveyors which receive the plastic tube containing the product at a pointdownstream of the forming tube and displace the product a preset distancefrom the forming tube to create a pocket, means to close the plastic tubebehind the displaced product and ahead of the next product which is fedinto the forming tube as the product is displaced, and means to cut theplastic tube between the two closures so formed, characterised in that airis removed from the pocket before closure by applying vacuum, whichprovides the advantage that the time for closing the plastic tube isconsiderably reduced and the overall cycle time for packaging a product ismuch faster. The application of vacuum in this way also reduces themoisture content of the product. Typically the number of products that canbe packaged in a minute is increased by 50% e.g. from 8 to 12. Preferablythe product feed means comprises one or more belt conveyors. Alternativelya pusher system could be used. The plastic film may be fed past the heatwelder by means of plastic film feed conveyors.
The vacuum is advantageously applied within the forming tube and mostadvantageously it is applied by means of two extraction ducts adjacenteither side of each product feed conveyor. This has the advantage that theair is being withdrawn from the space created by the inevitable distortionof the product as it is gripped and conveyed by the product feedconveyors.
Preferably the vacuum is provided by one or more bag filter assemblieswhich has the advantage that as the vacuum is applied loose fibres areremoved from the insulation products and retained within the bag filterunit, thus leaving a cleaner and more dust-free final product.
Vacuum may also be applied to a nozzle in the forming tube, which isconveniently sited on the upper circumference of the forming tube upstreamof the area around which the plastic film is formed into a tube. Theadvantage of the provision of such a nozzle is that additional vacuum canbe applied to the volume within the forming tube in the case thatundersized units are being fed into the forming tube which would leave avoid space within the forming tube. The vacuum is desirably furtherenhanced by the provision of a suitably shaped baffle plate tosubstantially close the entrance to the forming tube around the stream ofundersized products.
The forming tube may be cylindrical and the product feed conveyors maycomprise two low profile conveyors located on opposite sides of theforming tube.
By the application of high levels of vacuum to the nozzle and the use of abaffle plate which completely seals the entrance to the forming tube,products can be vacuum shrunk and held in their reduced size by means ofclosely spaced take off conveyors until the pack is rendered airtight byclipping.
According to the invention there is also provided a method for packingcompressed insulation product in heat sealable plastic film comprising,feeding product into a forming tube by means of product feed conveyors,sensing when a lead unit has reached the downstream end of the formingtube and clamping it in that position by stopping the product feedconveyors, feeding a web of heat sealable plastic film around a former togenerate a plastic tube with a longitudinal opening around the formingtube, expelling the lead unit from the forming tube by action of theproduct feed conveyors whilst longitudinally heat welding the plastic tubeand feeding it over the downstream end of the forming tube to wrap aroundthe product, gripping the plastic tube containing the product by take-offconveyors and conveying the product until it is completely removed fromthe forming tube and is displaced from it by a preset distance, whilstadvancing the next product to the end of the forming tube by operation ofthe product feed conveyors, thereby creating a pocket within the plastictube between the rear of the lead unit and the front of the next unit,closing the plastic tube behind the lead unit and ahead of the next unitand optionally cutting the plastic tube between the two closures soformed, characterised in that air is removed from the pocket, prior to theclosing, by application of a vacuum.
Advantageously the plastic tube is fed into the pocket by further operationof plastic film feed conveyors after the lead unit has been displaced bythe preset distance. This is advantageous because it eliminates thenecessity to displace the lead unit further than the position that itneeds to be in for end closure and then reverse the direction of motion ofthe lead unit to generate the excess tube in the pocket space. Theparticular advantage of the new process is that the number of consecutiveprocess operations are reduced thereby reducing the overall process time.Desirably the closure is created by gathering the plastic first in oneplane and then in a second plane perpendicular to the first and thenfitting a clip to hold the plastic in the gathered configuration, theadvantage of using a clip in this way is that it provides a fast andsecure means to close the packages which is able to withstand the tensiondue to the tautness of the packing immediately without any requirement tocool a heat weld to strengthen it. The plastic film may be preprinted andsensing means may ensure that the units are aligned to be in register withthe printing. Such a system provides attractive packaging. The product andthe forming tube may be substantially cylindrical which allows the packingmachine to accept conventional rolls of compressed insulation materialwhich may be retained under compression prior to introduction into theforming tube by means of a cylindrical paper wrapping.
In a modification of the process a roll of insulation material, which has adiameter which is significantly less than the diameter of the forming tubeand the welded plastic tube, has the plastic tube wrapped tightly about itdue to the application of additional vacuum to the space above the rollwithin the forming tube and the use of a suitably shaped baffle plateacross the entrance to the forming tube to maintain the vacuum within theforming tube.
In a further modification of the process a roll of insulation having aninitial diameter substantially the same as or smaller than that of theforming tube is caused to have its average diameter reduced by theapplication of vacuum within the plastic tube and held at the reduceddiameter while it is clipped to render it substantially airtight. Acontainment sleeve may then be applied to retain the reduced diameter inthe event the pack becomes punctured.

What is claimed is:
1. A packing machine for wrapping compressed insulation products in heatsealable plastic film, comprising:
a forming tube having an upstream end into which compressed insulationproducts may be fed and downstream end out of which they may bedischarged, said forming tube including product feed conveyors and meansto selectively operate said product feed conveyors to advance or holdstationary a compressed insulation product within said forming tube;
a former capable of reconfiguring a web of said plastic film as a plastictube with a longitudinal opening;
a heat welder for closing the longitudinal opening and yielding acontinuous plastic tube of plastic film around said forming tube;
plastic film feed conveyors for advancing said continuous plastic tubebeyond the downstream end of said forming tube while said product feedconveyors are holding a said compressed insulation product stationarywithin said forming tube;
take-off conveyors located remotely from the downstream end of said formingtube and operable to displace a compressed insulation product dischargedform said forming tube;
closure means located adjacent the downstream end of said forming tube andoperable to form two adjacent closures in said continuous plastic tube;
a cutting tool operable to cut said continuous plastic tube between saidtwo adjacent closures; and
vacuum means operable to remove air form said forming tube and saidcontinuous plastic tube downstream of said forming tube.
2. A packing machine according to claim 1, wherein said vacuum meansincludes a duct associated with an interior of said forming tube forextracting air from within said forming tube.
3. A packing machine according to claim 1, wherein said vacuum meansincludes at least one filter assembly.
4. A packing machine according to claim 1, and a baffle plate to sealaround a continuous stream of substantially uniform cross-sectionedproducts entering said forming tube.
5. A packing machine according to claim 1, in which said forming tube issubstantially a cylinder.
6. A packing machine according to claim 1, and a vacuum sealing plate toseal the upstream end of said forming tube, and said take-off conveyorsare arranged to retain products at a reduced size whilst said closures areformed.
7. A process for wrapping compressed insulation products in heat sealableplastic film, comprising:
feeding units of comprised insulation product into an upstream end of aforming tube by means of product feed conveyors, said forming tube alsohaving a downstream end from which units of compressed insulation productmay be discharged;
stopping a first said unit of compressed insulation product as it reaches aposition at the downstream end of said forming tube by stopping saidproduct feed conveyors;
feeding a web of heat sealable plastic film around a former to generate aplastic tube, with a longitudinal opening, around said forming tube,
expelling the first unit from said forming tube by action of the productfeed conveyors whilst longitudinally heat welding said plastic tube andfeeding it over the downstream end of said forming tube by means ofoperation of plastic film feed conveyors, to wrap around the first unit;
gripping the plastic tube containing the first unit by take-off conveyorsand conveying the first unit until it is completely removed from saidforming tube and is displaced from it by a preset distance whilstadvancing a second said unit of compressed insulation productsubstantially to the downstream end of said forming tube by furtheroperation of the product feed conveyors, thereby creating a pocket withinsaid plastic tube in a space between an upstream end of the first unit anda downstream end of the second unit, wherein air is removed from saidpocket between the first and second units by application of vacuum, andsaid plastic tube is fed into said space by further operation of saidplastic film feed conveyors after the first unit has been displaced bysaid preset distance and during said application of vacuum; and thenclosing said plastic tube behind the first unit and ahead of the secondunit.
8. A process according to claim 7, wherein the closing step includesgathering said plastic tube firstly in a first plane and then in a secondplane substantially perpendicular to the first plane, and then fittingretaining means to hold the plastic tube in a gathered configuration.
9. A process according to claim 8, wherein said retaining means comprises ametal clip.
10. A process according to claim 7, in which the product is a roll ofinsulation material retained under compression by means of a cylindricalwrapping.
11. A process according to claim 10, in which said roll of insulationmaterial has a diameter which is significantly less than the diameter ofsaid forming tube and said plastic tube is caused to wrap tightly aboutsaid roll by the application of additional vacuum to the space above saidroll within said forming tube and the use of a suitably shaped baffleplate across the upstream end of said forming tube to maintain the vacuumwithin said forming tube.
12. A process according to claim 10, in which said roll of insulationmaterial is caused to have its average diameter reduced by the applicationof vacuum, whilst said forming tube is sealed by means of a vacuum sealingplate, said roll of insulation material then being held at the reduceddiameter while said wrapping is closed to render its substantiallyairtight.
13. A process according to claim 10, in which said roll of insulationmaterial has an initial diameter substantially the same as that of saidforming tube and is caused to have its average diameter reduced by theapplication of vacuum, whilst said forming tube is sealed by means of avacuum sealing plate, said roll of insulation material then being held atthe reduced diameter while said wrapping is closed to render itsubstantially airtight.
14. A process according to claim 7, wherein the step of closing saidplastic tube comprises forming a first closure behind said first unit anda second closure ahead of said second unit, the process further comprisingthe step of cutting said plastic tube between said first and secondclosures.
15. A process according to claim 7, including filtering said air removedfrom said pocket.
16. A process according to claim 7, wherein the plastic tube is formed fromplastic film with preprinted markings, and wherein the process includessensing said preprinted markings and adjusting said space between saidfirst and second units to bring said markings into registry withsuccessive said units.

BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described, by way of example only, and withreference to the accompanying drawings, of which:
FIG. 1 is a schematic side elevation of a thermal insulation packingmachine,
FIG. 2 is a transverse cross section taken through x-x on FIG. 1,
FIG. 3 shows part of a gathering and clipping system,
FIGS. 4, 5 and 6 show the operating cycle of a packing machine,
FIG. 4A taken along the line 4A--4A of FIG. 4 shows a baffle plate 60.
FIG. 7 shows a packing machine packing and shrinking the package by use ofvacuum.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 shows a packing machine 1 located between an incoming conveyor 2 andan outgoing conveyor 3. Adjacent the incoming conveyor 2 are four beltfeed conveyors 4 each having a diverging portion 5 immediately adjacentthe end of the incoming conveyor 1. Immediately adjacent the end of thebelt feed conveyors 4 remote from the incoming conveyor 2 is a cylindricalforming tube 6 having a flared entry portion 7.
As shown in FIG. 2, disposed laterally along the interior wall of theforming tube 6 are two product feed conveyors 8. Above and below each ofthe product feed conveyors 8 is an extraction duct 9
Referring again to FIG. 1 provision is also made for further vacuum to beapplied to forming tube 6 through nozzle 10 located on the upper portionof forming tube 6 towards the end having the flared entry portion 7.
Beneath the forming tube 6 is a system for continuously feeding a web ofheat sealable plastic film 11 from one or more of rolls 12. The film 11 isfed around an accumulator 13 before being led over a forming shoulder 14so shaped that the film is formed into a cylinder around the forming tube6. A heat welder 15 is provided to weld the plastic cylinder into acontinuous plastic tube and plastic film feed conveyors 16 are provided toadvance the continuous plastic tube over the forming tube 6.
Downstream of the forming tube 6 are situated two plastic tube gatheringand clipping systems 17 and 18. One of these is shown in more detail inFIG. 3. It comprises two horizontal bars 19,20 which can move towards andaway from each other. An upper bar 19 is positioned above the plastic tubeand a lower bar 20 is positioned below it. Each bar has a groove runningalong its length on the side facing the plastic tube. Pistons 21 arearranged to move inwardly along the grooves when the bars 19 and 20 arebrought together. A metal clip 22 is held by on of the pistons and aforming head 23 on the other piston is arranged to bend the clip around agathered plastic tube when the pistons, 21, meet at the center of thegrooves. A reciprocating cutting tool 23A is positioned between the twogathering and clipping systems 17 and 18.
Downstream of the plastic tube gathering and clipping system 18 aretake-off conveyors 24 which adjoin outgoing conveyor 3.
A typical operating cycle of the packing machine is shown in FIGS. 4 to 6.
FIG. 4 shows three product rolls 40, 41 and 42 in abutting relationshipwithin the forming tube 6 and the belt feed conveyors 4. A fourth productroll 43 is shown leaving the take-off conveyors 24. Product roll 40 isshown in a fixed position with its end aligned with the downstream end offorming tube 6. It is held gripped in that position by product feedconveyors 8. The heat welder 15 is swung away from the plastic tube 44which is held stationary by the plastic film feed conveyors 16. Theplastic tube 44 is shown gathered at the end of product roll 40 andclipped and cut to form a small tail 45.
Now, by simultaneous operation of conveyors 4, 8, 16 and 24 the productroll 40 is moved forward from the forming tube 6 along with the plastictube 44 which is fed forward at about the same rate. In practice it isfound to be beneficial to feed the plastic tube 44 slightly slower thanthe product roll 4U in order to stretch the tube 44 over the roll 4Q. Theheat welder 15 is lowered and activated whilst the plastic film feedconveyors 16 are in operation.
When the product roll 41 reaches the downstream end of the forming tube 6the product feed conveyors 8 are stopped and product roll 41 is held inthis position whilst product roll 40 continues to be moved downstream bythe take-off conveyors 24 until its rearward facing end is clear of thegathering and clipping system 18, whereupon it is held at that position bystopping the take-off conveyors 24. Throughout the movement of productroll 40, plastic film has been continuously welded into plastic tube 44and has been fed first onto product roll 40 and then allowed to stretchfrom the end of forming tube 6 to the back of product roll 40, thusforming a tube 46 enclosing a pocket 47 (shown in FIG. 5).
Throughout the packaging operational cycle vacuum is applied along thelength of the product roll in the forming tube 6 by means of suctionapplied to the four perforated extraction ducts 9. This suction is createdby connecting a bag filter 10A to pipes 11A leading from the extractionducts 9 and nozzle to. The vacuum applied is equivalent to a column ofabout 500 mm of water. The advantage of using a bag filter to supply thesuction in this way is that loose fibres in the product roll are removedand collected, thus preventing airborne fibres from contaminating theproduction environment and also beneficially reducing the dust and loosefibre content of the product.
Because product rolls are not exactly the same length, the precise positionwhere roll 40 is held stationary is made variable so that pre-printedpackaging can be kept in register with the product rolls. Take-offconveyors 24 stop the motion of product roll 40 when a registration markon the plastic film 11 passes a photosensor system 40A (FIG. 6). By thismeans equal lengths of packaging can be used for rolls having the samenominal size.
The plastic film feed conveyors 16 continue to feed the plastic tube intothe space between product rolls 40 and 41 after product roll 40 has ceasedto move. The vacuum applied to the extraction ducts 9 and nozzle 10 causesthe plastic tube to collapse into the pocket 47 until it disappears asshown at 46 in FIG. 6.
Towards the end of the collapse the horizontal gathering bars 19,20 arebrought together and then the pistons 21 are brought together in thegrooves in the gathering bars to gather the tube 46 tightly and clip it atthe two clipping points generally indicated at 17 and 18. Thus closing therear end of product roll 40 and the front end of product roll 41. Thegathered plastic tube is now cut by knife 23A between the two clips andproduct roll 40 is carried away by conveyors 24 and 3. The cycle is nowreturned to the position shown in FIG. 4 except that product roll 40 hasreplaced roll 43 and roll 41 has replaced roll 40.
The position that the cut is made between the two clips is arranged to benearer to one clip than the other so that a larger tail 50 (see FIG. 4) isgenerated on one end of the product roll to facilitate carrying by hand.Alternatively cuts can be made only between every second product roll tocreate two product rolls joined together by a collapsed length of plastictube, which then serves as a carrying handle. Furthermore several rollscan be packed together between clipped portions to enable multiple packsto be produced.
Thus far the operation of the packaging machine has been described only inrelation to cylindrical product rolls which both start and finish withsubstantially the same diameter as the forming tube 6. It has been foundthat, by means of a minor modification, it is possible to use the machineto package product rolls having considerably smaller diameters than thatof the s/ forming tube e.g. 350 mm diameter rolls in the case of a 450 mmdiameter forming tube. This is possible by applying further suction to thenozzle 10 whilst positioning a baffle plate 60 with an eccentric 350 mmopening 61 at the upstream end of the forming tube 6 (see FIG. 4A). Theextra vacuum thereby created within the forming tube 6 causes the 450 mmdiameter plastic tube to be sucked onto the 350 mm diameter product rollto produce a neat tight package which, after clipping, retains its shapeeven if it is subsequently punctured.
In a further modification of the invention it is possible to applysubstantially more vacuum to nozzle 10 to cause a 450 mm product roll tobe compressed by the higher pressure acting on the outside of the plastictube, thereby creating packages of reduced size and higher density whichcan be transported more efficiently. The degree of compression can befurther increased by arranging to supply product rolls to the forming tubeone at a time through an air lock system (not shown). Alternatively asystem such as that shown in FIG. 7 may be used. Here, with baffle plate60 removed, 450 mm diameter product rolls. 51, are led into the formingtube 6 one at a time and a vacuum sealing plate 52 is lowered behind theproduct roll 51. Vacuum is then applied through nozzle 10 and ducts 9until the reduced diameter product roll 51A is held in a compressed statedownstream of the clipping system. Retaining means (not shown) may be usedto prevent rearward motion of the roll 51A. It is then fully clipped andbecause it is airtight it remains as a package of substantially reducedsize, 51B, when it emerges downstream of conveyors 53. The vacuum packedroll may then have a containment sleeve applied to hold the diameter downif the pack becomes punctured. By use of a larger diameter forming tube itis possible to use vacuum to compress the insulation from a size largerthan 450 mm to a diameter of between 300 and 450 mm. Such products havebeen found to have better thickness recovery characteristics whenunwrapped.