Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
  • B65B7/00—Closing containers or receptacles after filling
  • B65B7/16—Closing semi-rigid or rigid containers or receptacles not deformed by, or not taking-up shape of, contents, e.g. boxes or cartons
  • B65B7/162—Closing semi-rigid or rigid containers or receptacles not deformed by, or not taking-up shape of, contents, e.g. boxes or cartons by feeding web material to securing means
  • B65B7/167—Securing by heat-shrinking
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
  • B65B51/00—Devices for, or methods of, sealing or securing package folds or closures; Devices for gathering or twisting wrappers, or necks of bags
  • B65B51/10—Applying or generating heat or pressure or combinations thereof
  • B65B51/20—Applying or generating heat or pressure or combinations thereof by fluid pressure acting directly on folds or on opposed surfaces, e.g. using hot-air jets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65B—MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING
  • B65B53/00—Shrinking wrappers, containers, or container covers during or after packaging
  • B65B53/02—Shrinking wrappers, containers, or container covers during or after packaging by heat

Definitions

• TITLE "Apparatus for the final heat treatment of a packaging with a thermoplastic film" DESCRIPTION
• Fresh food products are often packed to protect them from contact and prolong their life, in tubs or trays closed or wrapped in thermoplastic film.
• the present-day packaging techniques are fundamentally as follows: a) the tray is completely wrapped in thermoplastic film. If the tray containing the product may be likened to a parallelepiped, the packaging film covers all six faces of this parallelepiped; b) the tray is closed with a film welded to the open top of the tray. On the other five faces, again if likened to a parallelepiped, the tray itself is directly exposed.
• Thermoplastic films normally have a heat-shrink property which is prepared at the production stage and/or is the result of pre-stretching treatments at the use stage of these films, and this property can be used to improve the packaging process, i.e. to cause the film to cling very closely to the tray with the product inside.
• This packaging technique has the drawback that the whole of the package must be exposed to a large amount of heat by immersing it in a fluid at a very high temperature for a considerable period of time. This is necessary in order to raise all of the film around the tray to a high enough temperature to set off the shrinkage process in order to cause the film which would otherwise be loose, to cling to the tray.
• the film has barrier or fluid-impermeability properties and is heated by convection by a stream of hot air, there will inevitably be an increase in the temperature of the atmosphere contained within the film envelope, tending to increase the volume and consequently the internal pressure of the packaging precisely because of this impermeability of the film to fluids.
• This increase in the internal pressure stretches the packaging film, which deforms much like a balloon being inflated.
• the atmosphere inside the packaging cools down and the internal pressure is removed, the creases and wrinkles that existed before the heat treatment return, sometimes worse than before. It is an object of the invention to solve this serious technical problem with the following idea for a solution.
• At least the top of the packaging film, the part that covers the tray and through which the product is seen, is heated essentially by heat conduction by any suitable means which physically touches the outer surface of the top of the packaging film, in such a way as to "spread” over it, by physical contact, the minimum amount of heat necessary to "heat-shrink” this surface, without significantly modifying the temperature of the atmosphere inside the packaging.
• the said means of heat treatment of the top of the packaging consists of at least one roller or at least one other means of rolling type, such as a belt for example.
• Fig. 1 is a perspective view of the present apparatus; and Fig. 2 shows the apparatus in plan view from above and with parts in section.
• Fig. 3 and 4 are views respectively in side elevation and in plan view from above of another embodiment of the invention.
• reference 1 denotes the belt conveyer which travels in the direction F carrying the packaging 2 with the product 102 inside a tray packed in a thermoplastic stretch film, which may optionally also have a barrier effect or fluid- tightness properties, coming from the packaging machine.
• the stretch film wrapped around the product may be of the usual type that allows all gases to pass through it, or of the type impermeable to all gases or of the type that allows some gases to pass through it and others not.
• at least one preferably rolling means such as for example a belt, or preferably a roller 3 of suitable diameter, which may be idle, constructed at least superficially with any material that does not stick to the packaging film and that is heated by any suitable means to a temperature at which, when this roller is rolled over the top surface of the packaging and touches it with slight interference (see below), it transfers to this surface directly, by conduction, the moderate amount of heat necessary to remove any creases or wrinkles from this surface without significantly modifying the temperature of the atmosphere inside the packaging.
• the roller 3 may have its own heat sources, which may be internal to it, or may receive its heat from a stream of hot fluid striking it, produced for example by the apertures B1 and B2 on the sides of the intermediate-final part of the conveyer 1 , which dispense hot air at the right temperature onto the perimeter of the packaging 2, also flowing over the roller 3 and transferring to it the heat required for the heat treatment of the top of the packaging 2.
• the roller 3 must not only be non-stick towards the film of the packaging 2 but also light enough not to induce harmful interference with the said packaging and must have good thermal inertia. Good results have been obtained for example with aluminium rollers covered with silicone rubber or with rollers made of carbon-fibre composite and epoxy matrix, which has the great advantage of reducing their weight.
• the roller 3 is supported rotatably ⁇ n bearings or other means with a low coefficient of friction 4, by a spindle 5 attached to the free end of a U-shaped arm 6, which extends from the roller in the direction from which the packaging has arrived and which at the other end is mounted rotatably, via bushes 7 with a low coefficient of friction, on a horizontal shaft 8 parallel to the said roller.
• the shaft 8 passes through straight vertical slots 10, 110 in brackets 11 , 111 attached to the sides of the frame of the conveyer 1 , and attached to the insides of these brackets are vertical racks 12, 112 meshing with pinions 13, 113 keyed to the said shaft 8, which last has on at least one end a knob 108 which can be turned to rotate the shaft 8 and modify its distance from the conveyer 1.
• the shaft 8 is stabilized at the height selected by rotating it in this way by means of the friction exerted against the brackets 11 , 111 by pairs of washers 9, 109 which are made of a material suitable for the purpose, are mounted on this shaft 8, and touch the opposite faces of the said brackets.
• stepper motor or equivalent type conveniently arranged so as not to be affected by the temperatures of the operating station in which it operates and controlled by the processor at the packaging machine which with the aid of means normally present in the said packaging machine knows the dimensions of the various products inserted into the packaging cycle.
• the said height adjustment of the shaft 8 also modifies the height of the roller 3 and its distance from the conveyer 1 , as does the possibility of pivoting upwards, by the device which will now be described.
• a lever 16 formed for example from a metal sheet by cutting and bending.
• roller 3 turns and is suspended from a structure that enables its minimum distance from the conveyer 1 to be adjusted in such a way that the roller can operate in contact with that part of the packaging 2 film which closes the top of the tray with the product inside, without significantly touching the tray itself.
• the roller 3 In contact with the packaging film, the roller 3 rotates because of friction between it and the packaging and spreads onto the said film the heat necessary for neutralizing any creases or wrinkles.
• Good results have been obtained when packaging with film having a thickness of approximately 40 microns, with the film being treated by the roller 3 at a temperature of between approximately 40° and 80°C, the said packaging being advanced by the conveyer 1 at a speed of between 0.05 and 0.5 m/s.
• a modified atmosphere is created inside the packaging to prolong the life of the packaged product. This atmosphere is at a slightly higher pressure than the external atmosphere, so the top of the film of the packaging is not perfectly flat but slightly domed, with a slight outward convexity.
• the roller 3 will therefore on average touch the highest part of this dome of film, without significantly interfering with the tray, as any serious interference between these two parts could result in impact damage to the packaging or could stop the packaging on the conveyer 1 , with obvious negative consequences.
• the entire moving part of the device, including the roller 3 and the arm 6, must be kept as light as possible -so that it can be raised with the least possible effort during the interference between the roller and the incoming packaging 2.
• the objective of lightening the said moving part can be achieved, in combination with or as an alternative to the matters described with reference to limiting the weight of the roller 3, by the additional application of a suitable counterweight (not shown), for example on the crossbar 106 of the arm 6.
• the arm 6 may support one after the other, two or more mutually parallel rollers 3, as illustrated in dashes in Figure 1 , in such a way as to create a rotating grid which limits the direct exposure of the top of the packaging to the external environment and is therefore better able to treat this part essentially by heat conduction.
• the pivoting arm 6 may advantageously be replaced by a parallel-motion mechanism and the array of rollers 3 will be supported by that side of the parallelogram which is opposite the fixed side, so that the said array of rollers can pivot while always remaining parallel to the conveyer 1 beneath it.
• the roller or rollers 3 may be driven in some suitable way rather than being idle. According to the embodiment which will now be described with reference to Figures 3 and 4, there are provided means for automatically adapting the height position of the rollers for the final heat treatment of the packaging to the different sizes of the said packagings.
• reference numeral 1 indicates the belt conveyer which travels in the direction of arrow F and onto which there rests the packaging F with the product arranged at the interior of a tray and tightly wrapped by a thermoplastic film which is stretchable and can be also of the barrier effect or fluid tight.
• the stretchable film which wraps the product can be of the common type which permits the passage or all gases or of a type impermeable to all gases or of the type which permits the passage of some gases and not of other gases.
• top portion of the packaging 2 is thermally treated by a set of rollers 3 of suitable diameters, for example freely rotatable, constructed at least superficially with any material that does not stick to the packaging film and that is heated by any suitable means to a temperature at which, when this roller is rolled over the top surface of the packaging and touches it with slight interference (see below), it transfers to this surface directly, by conduction, the moderate amount of heat necessary to remove any creases or wrinkles from this surface without significantly modifying the temperature of the atmosphere inside the packaging.
• suitable diameters for example freely rotatable
• the rollers 3 may have their own heat sources, which may be internal, or may receive the heat from a stream of hot fluid striking it, produced for example by the apertures B1 and B2 on the sides of the intermediate-final part of the conveyer 1, which dispense hot air at the correct temperature onto the perimeter of the packaging 2, also flowing over the rollers 3 and transferring to them the heat required for the heat treatment of the top of the packaging 2.
• the rollers 3 and the conveyer 1 are preferably insulated from the outer environment by a removable hood 18 preferably of suitable transparent plastic material, open at both ends, which has the function of maintaining the heat produced by the apertures B1 and B2 suitably concentrated onto the travelling packages and onto the rollers 3.
• the rollers 3 are mounted rotatable the one following the other, co-planarly and at a short distance the one from the other onto the horizontal portion of side members 19, 119, for example having the shape of a rectangular triangle or of a square and they are hinged at 20 and 120 to parallel link rods 21, 121 , of which the upper ones 21 are rotatably mounted by their other end to a rod 22 parallel to the hinge points 20, 120 and secured by its end to supports 23, 123 which on their turn a secured to the side members of the frame of the conveyer 1 , while the lower link rods 121 are secured by their other end, for example by means of a stop dowel 24 to a shaft 25 parallel to the said rod 22, which by its ends is rotatably supported by the supporting members 23, 123.
• the link rods 121 carry on their end keyed to the shaft 25, appendices 221 directed upwards and provided with circular sector slots, having their axes of curvature on the axis of shaft 25 and traversed by the rod.
• one of the link rods 121 carries an appendix 321 directed downwardly, linked to a fork 27 secured to the stem of a linear actuator 28, for example to a simple-action cylinder and piston group, the body of which is secured by a bracket 29 to the near support 23.
• the slots 26 and the fork 27 which constitute the articulation of the appendix 321 add to the system a correct degree of freedom in the vertical displacement of the unit of rollers, which in this manner can bear by gravity onto the packaging to be treated and adapt itself to possible irregularities thereof.
• a photocell 30 which is acted upon by the passage of the packaging 2.
• the photocell 30 is connected to a processor 31 which is connected to the motor 32 which controls the conveyer 1 , and to the same processor there is connected also the electro-valve 33 which controls the cylinder 28. In correct time relationship therefore the processor will control the operation of the valve 33, by properly causing the lifting and lowering of the unit of roller 3, upon the passage of any packaging to be treated.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Fluid Mechanics (AREA)
• Basic Packing Technique (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Auxiliary Devices For And Details Of Packaging Control (AREA)
• Shaping Of Tube Ends By Bending Or Straightening (AREA)

Applications Claiming Priority (3)

Publications (2)

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Family Applications (1)

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• 2004
  • 2004-12-02 DE DE602004008671T patent/DE602004008671T2/de not_active Expired - Fee Related
  • 2004-12-02 ES ES04820458T patent/ES2291985T3/es active Active
  • 2004-12-02 AT AT04820458T patent/ATE371587T1/de not_active IP Right Cessation
  • 2004-12-02 WO PCT/EP2004/053232 patent/WO2005058705A1/en active IP Right Grant
  • 2004-12-02 EP EP04820458A patent/EP1699702B1/de not_active Not-in-force

Non-Patent Citations (1)

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