PACKAGING MACHINE

Abstract: A VFFS (vertical form, fill and seal) packaging machine, in which a web of bag-forming material (23) is driven downwards at a cyclically varying speed around a former (24) to overlap the edges of the web, and including a hot air device (10) for directing hot air onto the overlapping edges so as to seal them, characterised in that the hot air device (10) is supplied with air by a variable-speed blower (13) which automatically varies the velocity of the hot air directed towards the edges of the web, depending upon the speed of the web.

Description: ι Packaging Machine 2 3 This invention is concerned with packaging machines of the type * commonly referred to as a VFFS (vertical form, fill and seal) packaging 5 machine. An example of such a machine is described in British patent β specification No. 2056940. That specification describes a machine of 7 the type in which horizontal seals are formed intermittently and in which β the tube of bag forming material is accordingly fed intermittently. The 9 present invention is concerned particularly (though not exclusively) with ιo a machine of the type described in which the bag-forming material is fed ιι continuously or substantially continuously, and in which each horizontal i2 seal is formed by a pair of cooperating sealing jaws which move with the i3 bag material while forming the seal and usually also while forming a ι« horizontal cut to separate successive bags. is In a continuous motion machine, the horizontal seals may be i6 formed by cooperating rotary sealing jaws (or rotary double jaws forming i7 two seals during each revolution) or by cooperating sealing jaws which is move in a constant orientation along a D-shaped path so as to remain in i9 contact with the bag material while moving through a predetermined 20 straight-line path during which each seal is formed. The present 2i invention is more particularly concerned with machines including such 22 D-motion sealing jaws. 23 The longitudinal seam by which the edges of a web forming the 2« tube are joined may be achieved in various ways. In the past use has 25 been made of heated bands and there has also been a proposal 26 according to which hot air could be used to form the heat seal with 2 suitable packaging material of which an example is polythene. A prior 28 proposal involving the use of hot air is described in US patent 29 specification No. 5,466,326. 30 According to the present invention, in a machine of the type 3i described, the web of bag-forming material is driven downwards at a 32 cyclically varying speed around a former to overlap the edges of the web 33 (in simple overlap fashion or to form a butt joint), and the means for 3 4 sealing the overlapped edges longitudinally comprises a hot air device 35 for directing hot air onto the overlapping edges so as to seal them, 36 characterised in that the hot air device is supplied with air by a 37 variable-speed blower which automatically varies the velocity of the hot 38 air directed towards the edges of the web, depending upon the speed of 1 the web. 2 Downstream of the hot air device there is preferably means for 3 blowing cool air onto the seam to set the seal. 4 The web speed is varied cyclically in a controlled manner in order 5 to allow control of the bag length. For the same purpose, the speed of β the sealing jaws is preferably also varied cyclically. During each cycle, 7 between successive sealing operations, the web speed may be 8 increased to increase the bag length and/or the speed of the sealing 9 jaws may be decreased to increase the bag length. In practice a range ιo of bag lengths may be achieved by suitable control of the speed patterns π of both the web and the sealing jaws, the only essential criterion in a i2 continous-motion machine being that the speeds should be equal while i3 the sealing jaws are in contact with the bag material. i The speed of the hot air blower may be stepped between two is levels, one corresponding to the speed of the web during sealing, and i6 the other to the speed or average speed of the web between successive i7 sealing operations. Preferably, however, the blower is driven by a is variable speed motor which is continuously controlled by an inverter i9 control circuit in response to the speed of the web. 20 This invention enables a substantially uniform longitudinal seam to 2i be formed, notwithstanding variations in the speed of the bag-forming 22 material. 23 The air heating section of the hot air gun is preferably maintained 24 at a substantially constant but adjustable temperature. In contrast, the 25 disclosure of US patent 5,466,326 is based on control of the heating 26 element temperature and is not believed to be practically capable of 27 achieving as uniform a seam as can be achieved by the present 28 invention. The reason for this is that the temperature of a heating 29 element cannot be rapidly altered to allow the hot air temperature to 30 track the speed of the web. Alternatives described in US patent 3i 5,466,326 are also not believed to be as satisfactory as the present 32 invention in terms of allowing rapid control of the air sealing operation in 33 response to web speed. Furthermore, the application of cool air, 34 preferably in the form of a thin film of air, is believed to be important, 35 though other means of cooling the seam may alternatively be 36 substituted. 37 An example of a longitudinal seam forming arrangement 38 according to this invention is shown in the accompanying drawings. In l these drawings: 2 Figure 1 is a side view of the hot and cold air blowing 3 arrangements; 4 Figure 2 is a view from the right of Figure 1 , showing the nozzles 5 through which hot and cold air are blown; and 6 Figure 3 is a plan view of part of the apparatus. 7 Figure 1 shows a hot air gun 10 into which air is blown through a β duct 12 by a suitable blower represented diagramatically as item 13. 9 Power is supplied to the gun 10 by a cable 14, and the gun includes a ιo temperature adjuster 16. ιι Hot air from the gun 10 enters a hollow body 18 having a side i2 outlet formed by converging walls 18A and 18B (see particularly Figure i3 3) leading to a narrow nozzle portion formed by closely spaced parallel i4 walls 20 and 22 (see Figure 2). The walls 20 and 22 may be spaced is apart, for example, by 2mm or less. A hot air jet is thus directed from the i6 nozzle towards the overlapping edges of a web of packaging material 23 i7 formed into a tube around a cylindrical former 24 (Figure 3) , the is overlapping edges being in the region 23A. i9 Immediately after passing the hot air nozzle, the seam is secured 20 by a film of cool air directed towards it by a nozzle 26 supplied with cool 2i air via a tube 28. As shown in Figure 2, the nozzle 26 may comprise 22 three closely spaced parallel walls 26A so as to direct towards the seam 23 two thin films of cool air. Alternatively, however, the nozzle 26 may direct 24 a single film of air towards the seam and may be inclined to the centre 25 line of the seam so as to cover the entire width of the seam. 26 By way of example, the hot air nozzle 1 0 may be one 27 manufactured by Leister Elektro-Geratebau, of 6056 Kagiswil, 28 Switzerland, for example their device identified as the Leister Hot Air Tool 29 3000. The variable-speed blower, including a variable speed motor, may 30 also be of a type offered by the same company. 3i The cold air nozzle or "air knife" may be of a type manufactured by 32 Lechler. It may receive its air supply from the blower which supplies air 33 to the hot air nozzle, so that the air velocity will also vary according to the 34 bag material speed. 35 As shown in Figure 2, two non-metallic cheeks 32,34 are secured 36 to the outside surfaces of both of the walls 20,22 forming the hot air 37 nozzle. These cheeks prevent the packaging material from contacting 38 the nozzle, for which purpose the outer edges of the nozzle walls are 1 recessed within the outer surfaces of the cheeks 32,34, which may be 2 chamfered as shown in Figure 3. 3 Figure 3 shows the hot air nozzle in a retracted position allowing a 4 pivoted cover plate 36 to be moved into line with the nozzle. This s prevents hot air from the nozzle reaching the packaging material while e the machine is temporarily stationary. The hot air gun is maintained at a 7 constant working temperature even while the machine is temporarily β stationary, and the blower may be kept running at a slow speed. The 9 cover plate 36 is moved automatically, by a cam action, to the position in ιo line with the hot air nozzle when the nozzle is retracted. ιι The bag-forming material may be drawn along the former 24, for i2 example, by means of bands on opposite sides of the mandrel which i3 may drive the material with the aid of suction applied through apertures i4 in the bands. Alternatively, bands (possibly without suction) may be is used to pull the material forward and maintain it in tension while the i6 actual speed of the material is controlled by other means, for example i7 rollers upstream of the former 24. is As shown in Figure 3, the longitudinal seam forming apparatus is i9 mounted on a horizontal rod 38. It can be set at various positions along 20 the rod, by means of a clamp 40, to accommodate formers of different 2i sizes. 22 This invention may also be applied to an intermittent machine, that 23 is to say one in which the web stops to allow intermittently moving 24 sealing jaws to operate to form successive horizontal seals serving as 25 the top of each bag and the bottom of the next bag. The blower is 26 preferably arranged to run at a fixed low speed while the web is 27 stationary, and at a higher variable speed while the web is moving; as 28 before, the web speed preferably varies cyclically in a predeterminable 29 pattern to achieve the desired (adjustable) bag length. 30 31 32 33 34 35 36 37 38

Claims: i CLAIMS 2 3 1. A packaging machine of the type described, in which a 4 web of bag-forming material (23) is driven downwards at a cyclically 5 varying speed around a former (24) to overlap the edges of the web, and 6 including a hot air device (10) for directing hot air onto the overlapping 7 edges so as to seal them, characterised in that the hot air device (10) is β supplied with air by a variable-speed blower (13) which automatically 9 varies the velocity of the hot air directed towards the edges of the web, ιo depending upon the speed of the web. 11 i2 2. A machine according to claim 1 , including means (26) for i3 blowing cool air onto the seam downstream of the hot air device (10) to i4 set the seam. 15 i6 3. A machine according to claim 1 or claim 2, in which the i7 web of packaging material (28) is driven continuously at a cyclically is varying speed. 19 20 4. A machine according to claim 3, in which the blower speed 2i is continuously variable so as to increase when the web speed increases 22 and vice versa. 23 24 5. A machine according to claim 3, in which the blower is set 25 to operate at two or more set speeds. 26 2 6. A machine according to claim 1 or claim 2, in which the 28 web is arranged to be stopped at regular intervals while horizontal seals 29 are made which form the top of each bag and the bottom of the next 30 bag. 31 32 7. A machine according to claim 6, in which the hot air device 33 includes a nozzle which is arranged to move away from the web while 34 the web is stationary. 35 36 8. A machine according to claim 7, in which the blower is set 37 to run at a fixed low speed while the web is stationary and at a higher 38 variable speed while the web is moving. 1 2 9. A machine according to any one of claims 1 to 8, in which 3 the hot air device (10) including an air heating device which is 4 maintained at a constant but adjustable temperature. 5 6 10. A method of packaging products involving a machine of the 7 type described, in which a web of bag-forming material is driven β downwards at a cyclically varying speed around a former to overlap the 9 edges of the web, and a hot air device is arranged to direct a stream of ιo hot air onto the overlapping edges so as to seal them, characterised in ιι that the hot air device is supplied with air by a variable-speed blower i2 which automatically varies the velocity of the air directed towards the i3 edges of the web, depending upon the speed of the web. 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

Inventors: FINCHAM KEVIN RICHARD, THUMS JAMIE, FINCHAM, KEVIN, RICHARD, THUMS, JAMIE
Applicants: FINCHAM KEVIN RICHARD, MOLINS PLC, THUMS JAMIE, FINCHAM, KEVIN, RICHARD, THUMS, JAMIE
Application year: 1998
Main classification: B29C65
IPC codes: B29C65, B65B51