Packing machine

PACKING MACHINE

BACKGROUND OF THE INVENTION

This invention relates to packing machines, particu- 5 larly to thermal insulation packing machines and to the use of such packing machines to pack pre-compressed rolls of thermal insulation.

Thermal insulation such as glass fibre or rock wool is produced in the form of a continuous mat or web which 10 is cut to lengths and may be compression rolled on a machine such as that described in European Patent No. 131475. That machine ensures that the compressed roll is prevented from unwinding by applying a sheet of paper around the curved surface of the cylinder. To 15 prevent loss of fibres or damage to the roll so formed, it is usual to wrap this compressed cylinder in polythene. To do this the roll is transferred to a packing machine which first aligns the roll with the web from a large roll of polythene and then leads the edge of the polythene 20 around the roll of insulation. Nominally only one length of insulation cylinder can be wrapped by such a machine, which leads to the need to have multiple machines when production needs to be switched from one type of insulation product to another having a different 25 length. Furthermore, the exposed ends of the polythene need to be clipped to seal the package and in the known process this clipping operation requires the excess polythene to be gathered by rotating the entire roll and package slowly past gathering brushes and then apply- 30 ing the clips simultaneously to each end of the pack. The main drawbacks of this system are that the process is slow. Also it is not easy to get the polythene to wrap tightly about the insulation roll, which gives rise to ballooning of the package. This is both unsightly and 35 costly because it could entail the product taking up more room during storage and transport. The slow speed of operation means that several such machines have to be used to take the output of a single compression rolling machine and this is expensive and wastes 40 valuable floor space.

Insulation packing machines are also known in which the polythene wrapping material is welded into a continuous tube longitudinally around the insulating material. Such a machine is described in GB patent applica- 45 tion No. 2125760A which is primarily for wrapping stacks of insulation in slab form. The machine compresses the slabs between two conveyors which feed the compressed insulation into a welded plastic tube. The tube is formed from a special double folded roll of poly- 50 thene. Because the insulation will ultimately be held in compression by the polythene tube itself, it is necessary to allow the longitudinal heat weld to cool and strengthen before the conveyors can actually deliver the insulation into a free-standing tube of plastic. This 55 makes the process cycle time excessively long. In one version of this machine, transverse heat welds are made between the stacks of insulation slabs. To make such welds the polythene must be gathered between two bars and to prevent overstretching of the polythene during 60 this gathering, the insulation pack that is already inside the tube with its remote end sealed, must be free to move backwards. Thus, the excess tube length is created in the void between the two stacks of insulation slabs by removing the half sealed pack to a larger dis- 65 tance than is required for it to clear the transverse heat welding equipment and then allowing it to move back nearer to that minimum clearance. This extra movement

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slows the process considerably because the half sealed pack can only be removed at the rate that continuous tube can be formed by the longitudinal welding around the compression conveyors, and whilst in principle more heat could be applied, this would in practice cause overheating and increase the time that the weld would have to be allowed to cool before the process cycle could continue. A further disadvantage of this process is that air is trapped in the tube area between the two stacks of slabs and tends to be compressed when the volume is reduced by application of the gathering bars and backward motion of the half sealed pack. This air causes ballooning of the pack which is then partially eliminated when the pack and contents are removed from the effect of compression due to the conveyors above and below the pack. It will be appreciated that such over-compression is undesirable because it damages the insulation, particularly if it is glass fibre insulation. Furthermore, it is difficult to apply such compression to a roll which is sheathed in paper.

SUMMARY OF THE INVENTION

According to the present invention a packing machine for wrapping compressed insulation products in heat sealable plastic film, includes a forming tube having product feed means to move or hold the product within it, a former to reconfigure a web of heat sealable plastic film into a longitudinally open tube around the forming tube, a heat welder to close the longitudinal opening and provide a continuous plastic tube, take-off conveyors which receive the plastic tube containing the product at a point downstream of the forming tube and displace the product a preset distance from the forming tube to create a pocket, means to close the plastic tube behind the displaced product and ahead of the next product which is fed into the forming tube as the product is displaced, and means to cut the plastic tube between the two closures so formed, characterised in that air is removed from the pocket before closure by applying vacuum, which provides the advantage that the time for closing the plastic tube is considerably reduced and the overall cycle time for packaging a product is much faster. The application of vacuum in this way also reduces the moisture content of the product. Typically the number of products that can be packaged in a minute is increased by 50% e.g. from 8 to 12. Preferably the product feed means comprises one or more belt conveyors. Alternatively a pusher system could be used. The plastic film may be fed past the heat welder by means of plastic film feed conveyors.

The vacuum is advantageously applied within the forming tube and most advantageously it is applied by means of two extraction ducts adjacent either side of each product feed conveyor. This has the advantage that the air is being withdrawn from the space created by the inevitable distortion of the product as it is gripped and conveyed by the product feed conveyors.

Preferably the vacuum is provided by one or more bag filter assemblies which has the advantage that as the vacuum is applied loose fibres are removed from the insulation products and retained within the bag filter unit, thus leaving a cleaner and more dust-free final product.

Vacuum may also be applied to a nozzle in the forming tube, which is conveniently sited on the upper circumference of the forming tube upstream of the area around which the plastic film is formed into a tube. The advantage of the provision of such a nozzle is that additional vacuum can be applied to the volume within the forming tube in the case that undersized units are being fed into the forming tube which would leave a void space within the forming tube. The vacuum is desirably further enhanced by the provision of a suitably shaped baffle plate to substantially close the entrance to the forming tube around the stream of undersized products.

The forming tube may be cylindrical and the product feed conveyors may comprise two low profile conveyors located on opposite sides of the forming tube.

By the application of high levels of vacuum to the nozzle and the use of a baffle plate which completely seals the entrance to the forming tube, products can be vacuum shrunk and held in their reduced size by means of closely spaced take off conveyors until the pack is rendered airtight by clipping.

According to the invention there is also provided a method for packing compressed 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 forming tube and clamping it in that position by stopping the product feed conveyors, feeding a web of heat sealable plastic film around a former to generate a plastic tube with a longitudinal opening around the forming tube, expelling the lead unit from the forming tube by action of the product feed conveyors whilst longitudinally heat welding the plastic tube and feeding it over the downstream end of the forming tube to wrap around the product, gripping the plastic tube containing the product by take-off conveyors and conveying the product until it is completely removed from the forming tube and is displaced from it by a preset distance, whilst advancing the next product to the end of the forming tube by operation of the product feed conveyors, thereby creating a pocket within the plastic tube 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 unit and optionally cutting the plastic tube between the two closures so formed, characterised in that air is removed from the pocket, prior to the closing, by application of a vacuum.

Advantageously the plastic tube is fed into the pocket by further operation of plastic film feed conveyors after the lead unit has been displaced by the preset distance. This is advantageous because it eliminates the necessity to displace the lead unit further than the position that it needs to be in for end closure and then reverse the direction of motion of the lead unit to generate the excess tube in the pocket space. The particular advantage of the new process is that the number of consecutive process operations are reduced thereby reducing the overall process time. Desirably the closure is created by gathering the plastic first in one plane and then in a second plane perpendicular to the first and then fitting a clip to hold the plastic in the gathered configuration, the advantage of using a clip in this way is that it provides a fast and secure means to close the packages which is able to withstand the tension due to the tautness of the packing immediately without any requirement to cool a heat weld to strengthen it. The plastic film may be preprinted and sensing means may ensure that the units are aligned to be in register with the printing. Such a system provides attractive packaging. The product and the forming tube may be substantially cylindrical which allows the packing machine to accept conventional rolls of compressed insulation material

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which may be retained under compression prior to introduction into the forming tube by means of a cylindrical paper wrapping.

In a modification of the process a roll of insulation

5 material, which has a diameter which is significantly less than the diameter of the forming tube and the welded plastic tube, has the plastic tube wrapped tightly about it due to the application of additional vacuum to the space above the roll within the forming tube and the

10 use of a suitably shaped baffle plate across the entrance to the forming tube to maintain the vacuum within the forming tube.

In a further modification of the process a roll of insulation having an initial diameter substantially the same

15 as or smaller than that of the forming tube is caused to have its average diameter reduced by the application of vacuum within the plastic tube and held at the reduced diameter while it is clipped to render it substantially airtight. A containment sleeve may then be applied to

20 retain the reduced diameter in the event the pack becomes punctured.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of ex25 ample only, and with reference to the accompanying drawings, of which:

FIG. 1 is a schematic side elevation of a thermal insulation packing machine,

FIG. 2 is a transverse cross section taken through x-x 30 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 35 shows a baffle plate 60.

FIG. 7 shows a packing machine packing and shrinking the package by use of vacuum.

DESCRIPTION OF THE PREFERRED 4Q EMBODIMENTS

FIG. 1 shows a packing machine 1 located between an incoming conveyor 2 and an outgoing conveyor 3. Adjacent the incoming conveyor 2 are four belt feed conveyors 4 each having a diverging portion 5 immedi

45 ately adjacent the end of the incoming conveyor 1. Immediately adjacent the end of the belt feed conveyors 4 remote from the incoming conveyor 2 is a cylindrical forming tube 6 having a flared entry portion 7. As shown in FIG. 2, disposed laterally along the

50 interior wall of the forming tube 6 are two product feed conveyors 8. Above and below each of the product feed conveyors 8 is an extraction duct 9

Referring again to FIG. 1 provision is also made for further vacuum to be applied to forming tube 6 through

55 nozzle 10 located on the upper portion of 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 of heat sealable plastic film 11 from one or more of rolls 12. The film 11 is fed around an

60 accumulator 13 before being led over a forming shoulder 14 so shaped that the film is formed into a cylinder around the forming tube 6. A heat welder 15 is provided to weld the plastic cylinder into a continuous plastic tube and plastic film feed conveyors 16 are provided to

65 advance the continuous plastic tube over the forming tube 6.

Downstream of the forming tube 6 are situated two plastic tube gathering and clipping systems 17 and 18.