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
  • B65B11/00—Wrapping, e.g. partially or wholly enclosing, articles or quantities of material, in strips, sheets or blanks, of flexible material
  • B65B11/02—Wrapping articles or quantities of material, without changing their position during the wrapping operation, e.g. in moulds with hinged folders
  • B65B11/025—Wrapping articles or quantities of material, without changing their position during the wrapping operation, e.g. in moulds with hinged folders by webs revolving around stationary articles
• • 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
  • B65B2210/00—Specific aspects of the packaging machine
  • B65B2210/14—Details of wrapping machines with web dispensers for application of a continuous web in layers onto the articles
  • B65B2210/18—Details of wrapping machines with web dispensers for application of a continuous web in layers onto the articles the web dispenser being mounted on a rotary ring

Definitions

• the present invention relates to a wrapping machine for pallets.
• a wrapping machine for pallets in which the product to be wrapped is in a fixed position and packaging is performed by means of spiral winding of an extendable film onto the product.
• the tension of the film is approximately constant for an elongation variable from about 80% to about 300% and therefore it is preferred to stretch the film prior to winding thereof around the product, not only to provide it with the desired technical retaining characteristics, but also so as to use less material while achieving the same results.
• This elongation also referred to as pre-stretching, is generally performed at the same time as unwinding of the film, by causing the latter to pass between a pair of rubberized rollers, shortly spaced apart and having different rotational speeds: the downstream roller rotates faster than the upstream roller, causing elongation of the film.
• the short distance between the two rollers has the purpose of preventing transverse contraction of the extendable film, a contraction which would not allow the desired pre-stretching in the longitudinal direction.
• the pre-stretching unit over time, has assumed different forms and characteristics with a view to constantly improving its performance and overcoming the intrinsic problems associated with operation thereof.
• the pre-stretching unit must not only simply release the stretched film, causing it to unwind from the bobbin, but must be able to ensure that the operating parameters, such as the feed speed and the tension imparted to the film, remain as constant as possible despite the fact that the winding conditions vary with a certain regularity.
• the most simple and economical solution adopted generally consists in connecting the two rubberized idle rollers by means of a pair of fixed gears of different diameter. In this way the speed ratio between the two rollers - and hence the pre-stretching tension - remains constant and the film is unwound from the bobbin, causing rotation also of the rubberized rollers, owing to the tension imputed to the film and which is generated as a result of the relative movement between bobbin of reel and product.
• the most advanced wrapping machines for pallets use a motorized pre-stretching unit in which at least one of the two rollers is motor-driven and the speed of rotation of the pre- stretching unit, and indirectly the feed speed of the film, are regulated on the basis of the tension detected on the film downstream of the pre- stretching unit.
• the tension of the film is detected by means of a so-called "jockey roller” consisting of a roller which is mounted on the end of an oscillating arm and over which the film travels: the tension of the film causes the arm of the jockey roller to oscillate, activating electric systems which emit a regulating signal for driving the pre-stretching unit.
• the rubberized rollers may be driven independently, or use may be made of a motor-driven roller coupled with a braked one, and so on.
• the wrapping machines for pallets used hitherto in the art consist substantially of two constructional types: one type where the bobbin of extendable material and the pre-stretching unit are mounted so as to slide vertically on a column and the product is made to rotate on a rotating platform, and another type where the product is fixed and the bobbin with the pre-stretching unit are made to rotate in a spiral path around the product to be packaged.
• the second type is specially designed for high productivity and is the one to which the invention refers.
• the bobbin and the pre-stretching unit are mounted on a support bracket which describes a circular trajectory as it moves along the axis of the spiral.
• This movement is obtained substantially by two methods: by means of a rotating arm, hinged on a vertical axis at the top of the product, or by means of a rotating ring, surrounding the product, both moving vertically on suitable guides formed, normally, on a bridge frame which embraces the transportation line on which the palletized products travel.
• the bobbin and the pre-stretching unit mounted on the support bracket constitute a not insignificant mass, of the order of 70-80 kg, which shall be made to rotate along a circular trajectory with a wide radius (for palletized products, a minimum diameter of about 2 m is required) and with an angular speed of about one revolution per second, thus generating considerable centrifugal forces.
• a not insignificant mass of the order of 70-80 kg, which shall be made to rotate along a circular trajectory with a wide radius (for palletized products, a minimum diameter of about 2 m is required) and with an angular speed of about one revolution per second, thus generating considerable centrifugal forces.
• the motor for the driving system must be necessarily mounted together with the pre-stretching unit on the support bracket. This involves the transfer of power, an electric power for the most part of the cases of electric power, from a fixed installation to the motor in movement along a circular trajectory.
• the power supply line will therefore make use of sliding contacts or other known systems, but will nevertheless be complex and costly.
• the bobbin may run out at a time when the operator is involved in other operations and therefore the machine downtime will also be determined by the time necessary for the operator to realize that replacement is required and to interrupt the operation which he was already performing.
• the bobbin runs out without having completely enveloped a product: in this case the operator is obliged to eliminate the portion of film already wound on the product and recommence the packaging of that product so as to avoid the same remaining slack or incomplete.
• the object of the present invention is therefore that of eliminating entirely all the drawbacks mentioned above and, in particular, of providing a machine which is able to wrap a product, resting on the pallet in a fixed position, with an extendable film, by stretching the film itself, during feeding thereof, in a constant and uniform manner and without making use of complicated mechanisms for adjusting the tension; preferred embodiment, this machine must also allow elimination of the dead time resulting from machine stoppage and facilitate maintenance work by the operator; a final object is that of achieving the aforementioned features with a machine which is both streamlined and lightweight and which thus allows a reduction in the manufacturing and rigging costs.
• a wrapping machine for pallets of the type comprising a fixed frame on which there is mounted an annular - structure surrounding a product to be wrapped and translatable with respect thereto, wherein a film of plastic material is distributed around said product by the annular structure, wherein said annular structure has a configuration in the form of an epicycloidal gearing in which the spider, the planetary gears and the driving gear consist, respectively, of an annular support, a set of rollers rotatably mounted on parallel axes mounted on said annular support along a circular line, and a driving element operated by motor means and acting on said rollers, and wherein said film is supplied from the outside of said annular structure and, crossing said annular structure between two of its adjacent rollers, is distributed internally by the rotation of said annular structure, so as to be applied in turns on said product.
• Fig. 1 is a side elevation view, with parts removed, of a wrapping machine for pallets according to the invention
• Fig. 2 is a top plan view of the wrapping machine for pallets according to the invention.
• Fig. 3 is a view, on a larger scale, of a partial section along the line Ill-Ill of Fig. 2;
• Fig. 4 is a view, on a larger scale, of the details shown enclosed by the circle B in Fig. 1 ;
• Fig. 5 is a plan view, on a larger scale, of the driving system and the pre-stretching unit according to a preferred embodiment of the invention
• Fig. 6 is a view, similar to that of Fig. 2, of another embodiment of the invention.
• Fig. 7 is a view, similar to that of Fig. 4, of the embodiment shown in Fig. 6.
• a bridge frame P of a known type, is located across a transportation line T, at the position for packaging towards which a product C, resting on a pallet, moves.
• the machine which actually performs wrapping with the extendable film consists of a ring structure N (which can be seen in Fig. 1 in the raised position) mounted so as to slide vertically on the bridge frame P and raised and lowered by means of a raising system operated by a motor M.
• the annular structure N consists of a pair of annular rims - a lower one 1 and upper one 2 - which are fixed together by a set of pins arranged along an ideal circular line, on which there rotate rollers 3 mounted idle between said rims 1 and 2 which thus form an annular support for said rollers.
• the two rims 1 and 2 are guided on a guiding frame 4 so that they are free to rotate in their plane.
• the guiding frame 4 comprises a set of wheels 5, in particular eight wheels 5 (Fig. 3), which are arranged uniformly along the perimeter of the rims 1 and 2 and on which the annular structure N is supported, being free to rotate.
• An endless belt 6 extends over the rollers 3, on the outside thereof, embracing the entire set of rollers 3 as shown in Fig. 3, and also traveling over a driving pulley 7 of a power motor 8 (Figs. 4 and 5) arranged on the outside of the annular structure N.
• an epicycloidal transmission system in which the planetary gears are the rollers 3, the spider consists of the combined arrangement of the two rims 1 and 2, and the belt 6 forms the driving gear; the movement of the belt 6 is transmitted to the rollers 3 and to the rims 1 and 2 by suitably adjusting the resistance to the movement offered by them: should, for example, the two rims 1 and 2 be stopped, the movement of the belt would be converted totally into a rotation of the rollers 3 about their axes and, vice versa, if rotation of the rollers 3 were blocked, the movement of the belt 6 would produce rotational driving of the two rims 1 and 2 together with the rollers fixed thereto.
• rollers 3 - the roller 3a - is rubberized and is coupled with a corresponding rubberized roller 3b, arranged at a short distance from the roller 3a and further internally with respect to the ideal circular line described by the set of rollers (Fig. 5) .
• These two rollers 3a and 3b form a pre-stretching unit, which was discussed in detail above, having a well known configuration.
• they are connected by means of a gear-type coupling arrangement which provides a transmission ratio such that the roller 3b rotates at a greater speed than the roller 3a.
• a bobbin 9 of extendable plastic film is mounted, externally with respect to the ring structure N, on a suitable support (not shown) which allows free rotation thereof.
• an end of the film 10 is passed onto the roller 3a and then, in the opposite direction of rotation, onto the roller 3b as well, and, by means of a transmission roller 1 1 , is guided finally, with automatic gripper systems of the known type, which we shall not consider here, onto the product to be wrapped.
• the film 10 does not interfere with the belt 6 since the latter adheres to a upper portion of the rollers 3 (as can be clearly seen in Fig. 4), whereas the film adheres to the remaining portion thereof.
• the belt 6 causes rotation of the annular structure N which, in turn, causes rotation, about the product C, of the point where the extendable film 10 is released - which corresponds to the position of the transmission roller 1 1 - performing the desired winding action.
• the spiral path of the point where the film adheres onto the product C is obtained by combining the rotary movement of the annular structure N with vertical translation thereof on the bridge frame P.
• the epicycloidal system described has a fairly important characteristic feature, namely it constitutes a superb self-adjusting mechanism for the feeding tension of the film 10.
• the feeding tension of a greater quantity of film is required, resulting in an increase in the tension exerted thereon.
• the increase in tension immediately produces an equal and opposite reaction on the transmission roller 1 1 and on the pre-stretching unit, resulting in a braking action on the annular structure N.
• This equilibrium condition is typical of the particular working condition of the epicycloidal system, in particular the internal friction of the system and speed of the belt 6, and therefore may be regulated, for example, by suitably adjusting the braking system mentioned above.
• the ideal braking condition is the one where, with practically zero tension, i.e. where no film is required, there is also no feeding of the film, namely rotation of the annular structure occurs exclusively without rotation of the rollers.
• Another fairly interesting aspect of the wrapping machine for pallets according to the invention consists in the fact that, since the bobbin is mounted externally of the annular structure, it unwinds the film both onto the product C and onto the perimeter of the annular structure itself.
• the maximum thickness which the strip 10a may assume is 10 mm, which, for a diameter of 2 m typical of the annular structure N, means a variation in length of 1 % between the innermost ring and the outermost ring. This variation is entirely negligible, in terms of the behaviour of the strip 10a, for a material which is able to undergo elongation of up to 300%.
• the latter are preferably connected together, for example either by means of a series of short belts 1 2 which connect each roller 3 to the next one, or via a single peripheral belt when the perimeter to be embraced is small.
• These short belts 1 2 are preferably arranged on the upper portion of the rollers 3, underneath the drive belt 6. This arrangement also allows the movement to be transferred to the feed roller 3a, and hence to the pre-stretching unit, when the feed roller is located in the position illustrated in Fig. 5, i.e. at a position where it is not affected by the direct action of the belt 6.
• the winding tension can be regulated from the outside by adjusting the braking system of the annular structure, also during operation of the pallet wrapping machine;
• the accumulated strip provides an excellent support onto which the terminal end of the used-up bobbin may be joined to the initial end of the new bobbin, the joining operation being able to be performed simply by affixing of one end onto the other taking advantage of the adhesive properties of the extendable plastic material; in this way continuity is ensured between one bobbin and another one, completely eliminating the wastage of material following running out of the bobbin, both due to precautionary stoppage of the pallet wrapping machine and due to that portion of film wrapped only partially on the product;
• the optimum arrangement of the bobbin also simplifies the design of an automatic bobbin-changing machine
• the internal diameter of the annular structure N shall be greater than about 1 900 mm and its maximum dimension may be easily contained within 2300 mm, compared to the 2500 - 2600 mm of pallet wrapping machines constructed in accordance with the known art: this means that the entire machine may be loaded into the storage container of a lorry (width 2400 mm) without having to disassemble and reassemble the machine at its destination.
• a pallet wrapping machine which is simplified compared to the one described above, i.e. in which the bobbin is mounted fixed to the annular support defined by the two circular rims 1 and 2 (Figs. 6 and 7), is provided.
• the bobbin 9 there is no longer a relative movement between the bobbin 9 and the rims which results in the film being wound gradually onto the external perimeter of the rollers 3. Therefore, in the absence of the accumulating function of these rollers 3, it is no longer necessary for them to have a length at least equivalent to the height of the film, but it is sufficient for them to have an adequate length for engagement with the short belts 12.
• Only the rollers 3a and 3b, forming part of the pre-stretching unit, and where applicable the transmission roller 1 1 have an extension such that they are able to guide the entire height of the film.
• the bobbin is mounted entirely in cantilever fashion, projecting perpendicularly from one of the two annular rims, and likewise the rollers of the pre-stretching unit also project from the same side.
• This solution involves an advantageous constructional simplification, which consists in a greater lightness of the annular structure and in a reduction in costs, even though it means having to dispense with some of the advantages described above, including the possibility of creating an accumulation of film, so as to allow more efficient changing of the bobbin, and the elimination of eccentric masses, so as to lighten the supporting structure.
• the driving belt 6 could be replaced by a crown gear which engages, internally, with the rollers provided with pinions and, externally, with a driving pinion made to rotate by the motor 8.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Basic Packing Technique (AREA)
• Pallets (AREA)
• Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
• Liquid Crystal Substances (AREA)
• Steroid Compounds (AREA)

Applications Claiming Priority (3)

Publications (2)

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Cited By (2)

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• 1996
  • 1996-11-18 IT IT96MI002394A patent/IT1287108B1/it active IP Right Grant
• 1997
  • 1997-07-09 WO PCT/EP1997/003628 patent/WO1998022346A1/en not_active Ceased
  • 1997-07-09 DE DE69703359T patent/DE69703359T2/de not_active Expired - Fee Related
  • 1997-07-09 ES ES97935515T patent/ES2151291T3/es not_active Expired - Lifetime
  • 1997-07-09 AT AT97935515T patent/ATE197027T1/de not_active IP Right Cessation
  • 1997-07-09 EP EP97935515A patent/EP0938428B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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