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
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.