US20070227102A1

US20070227102A1 - Film Packaging Apparatus and Method

Info

Publication number: US20070227102A1
Application number: US11/631,151
Authority: US
Inventors: Alessandro Prataiola
Original assignee: Micromec Srl
Current assignee: Micromec Srl
Priority date: 2004-06-30
Filing date: 2005-06-30
Publication date: 2007-10-04
Also published as: WO2006003634A1; JP2008505024A; ITRM20040319A1; EP1776273A1

Abstract

A film packaging apparatus, operating on a flow of products movable along a feed direction and apt to package each product into a respective wrapping of heat-sensitive film, includes: a transversal sealing unit, having a heat sealer and a sealer receiving element, apt to seal transversal portions of the film transversally to the feed direction, an actuator with mechanical drive element for moving the heat sealer and the sealer receiving element in the direction of the flow; and a control unit, which controls the actuator so that, at a sealing section of the path of the products along which the heat sealer produces the sealing of the transversal portions of film, the speed of the heat sealer element and sealer receiving element in the direction of the flow is constant and equal to the speed of the flow of products.

Description

The present invention refers to a film packaging apparatus, and in particular to an apparatus of the kind operating on a flow of products movable at a substantially constant speed along a feed direction and apt to package each of said products into a respective sealed wrapping of heat-sensitive film. In addition, the invention refers to an associated packaging method.
The known packaging apparatuses of the kind mentioned hereto are used, in general, to package editorial products, like e.g. magazines, books, folders and the like or covers of any kind and nature whatsoever. Such apparatuses comprise various processing stations, operating in sequence on the flow of products, like e.g.: a wrapping station, in which the film is positioned with respect to the flow itself and just wrapped about the products; a longitudinal sealing station, in which longitudinal edges of the film are sealed the one to the other parallelly to the flow direction, so as to form a sort of continuous tube wrapping the products; and a transversal sealing station, in which transversal edges of the film are sealed the one to the other orthogonally to the feed direction of the flow, so as to enclose the products into respective separate sealed wrappings.
In order to produce a temporary local melting of the film and an optimal transversal sealing, to the opposed transversal portions of the film involved in such a sealing there should be transmitted a quantity of heat well-determined and at a preset temperature. In fact, any heat-sensitive film exhibits an optimal melting temperature range, of from 120 to 200° C. for the most commonly used films. In order to transmit to the film said predetermined quantity of heat at the desired temperature, the heat sealer of the transversal sealing station should remain into contact with the film portions to be sealed for a predetermined time period. Therefore, in order to utilize a flow of movable products uninterruptedly and not by fits and starts, i.e., to operate according to a continuous processing cycle, the heat sealer must be movable in the feed direction of the flow of products. The sequence of the positions that the heat sealer assumes during said transversal sealing operation defines a so-called sealing cycle. Such a sealing cycle may be conceived as subdivided into two main steps. In a first step, definable as contact step, the heat sealer is into contact just with the transversal portions of the film to be sealed and therefore the actual transversal sealing is carried out, via heat transmission by conduction between heat sealer and film. As mentioned above, this contact step should last enough to transmit to the film the quantity of heat required for its melting, at the temperature most suitable for the material of which the film itself is made of. Preferably, at the end of the contact step it will have been provided also the detachment, from said single tubular wrapping, of a wrapping that packages an individual product.
Once the sealing has ended, a second step of the transversal sealing cycle starts, called return step, in which the heat sealer has to move both in a direction orthogonal to the bearing plane, to move away from the sealed film, and in the direction of the flow of products, in a sense opposed thereto, to return to a position useful for a new sealing, i.e. the cycle start position. At the end of the return step the heat sealer lowers again to contact the heat-sensitive film.
To sum up the above, during a fall transversal sealing cycle the heat sealer should possess a trajectory resulting from the combination of two motion components, i.e. a component of reciprocating motion along the feed direction of the flow of products to be packaged and a motion component in a direction substantially orthogonal to said feed direction.
In known apparatuses this trajectory is obtained by means of a single motor and of associated mechanical driving members, e.g. a crank and slotted link mechanism, generating a substantially elliptical path of the heat sealer. Hence, in the hereto-described known apparatuses the two motion components are interdependent the one to the other. Such a packaging apparatus is, e.g., the subject-matter of the European patent application EP-A2-209184.
The same kind of transversal sealing station is used also when a heat transmission between heat sealer element and film is provided by irradiation rather than by conduction. In fact, this different heat transmission mode entails alike problems, having to take place with a predetermined distance between heat sealer element and film.
The kind of driving means used in known apparatuses, by causing said elliptical trajectory with non-independent motion components, forces the heat sealer to continual accelerations and decelerations. Therefore, during the contact step or generally that of transmission of heat to the film, the speed of the heat sealer is generally not equal to the speed of the flow of products, i.e. to the speed of the heat-sensitive film. This causes relevant imperfections in the transversal sealing. In fact, when a speed of the heat sealer is higher than that of the flow of products the film can tear, or holes and/or cumbersome stringy appendages can be generated. When instead the speed of the heat sealer is lower than that of the flow of products, the heat sealer itself, by opposing the motion of the film and of the products wrapped thereby, could cause jamming or anyhow the formation of wrinkling in the sealed film portions.
The technical problem underlying the present invention is to provide a film packaging apparatus and method overcoming the drawbacks mentioned hereto with reference to the known art.
Such a problem is solved by a film packaging apparatus according to claim 1 and by a method according to claim 26.
The present invention provides several relevant advantages. The main advantage lies in that it allows to obtain a heat sealer speed substantially constant in the feed direction of the products during the contact step of the transversal sealing cycle, speed that therefore can be set substantially equal to that of the flow of products, i.e. of the heat-sensitive film. Thus, the resulting transversal sealing exhibits optimal quality.
Further advantages, characteristics and the operation modes of the present invention will be made apparent in the following detailed description of preferred embodiments thereof, given by way of example and without limitative purposes. Reference will be made to the figures of the annexed drawings, wherein:
FIG. 1 shows a schematic depiction of an embodiment of the apparatus of the invention, in a side view thereof;
FIG. 2A shows a schematic perspective view of the apparatus of FIG. 1, and in particular of the flow of products packaged therein;
FIG. 2B shows a schematic top plan view of the apparatus of FIG. 1, and in particular of the flow of products packaged therein;
FIG. 3 shows an exemplary kinematic diagram of part of a transversal sealing unit of the apparatus of FIG. 1;
FIG. 4A shows a schematic depiction of a heat sealer element and of a sealer receiving element of the transversal sealing unit of FIG. 3 during their operation;
FIG. 4B shows a variant embodiment of the system of FIG. 4A;
FIG. 5A shows an exemplary kinematic diagram of a further system constituting the transversal sealing unit of FIG. 3;
FIG. 5B shows an exemplary kinematic diagram of the system illustrated in the preceding figure, according to a simplified version thereof;
FIG. 6 shows a representative graph of the pattern of the speed v_Cof a sealer receiving element of the apparatus of FIG. 1 as a function of its displacement x in the direction of the flow of products; and
FIG. 7 shows a representative graph of the pattern of the relative speed v_S/Cof a sealer receiving element and of a heat sealer element of the apparatus of FIG. 1 as a function of their displacement x in the direction of the flow of products.
With initial reference to FIGS. 1 and 2A-2B, a packaging apparatus according to the invention is generally indicated by 1. The apparatus 1 operates on a flow of products, each indicated by P, movable along a feed direction, the latter indicated by an arrow A.
As it will be apparent from the following description, the apparatus 1 is apt to package each of said products into a respective sealed wrapping I of heat-sensitive material film F. Such a film may be made, e.g., of a heat-sealable plastic material such as polyethylene, PVC, polypropylene or the like.
The apparatus 1 comprises various processing units, and the products transit from one unit to the subsequent one on conveying means that therefore cause said flow of products. Such conveying means typically consists in motor-driven conveyor belts, onto which the products to be packaged are laid according to a bearing plane parallel to the feed direction A of the flow.
In particular, in the present embodiment the apparatus 1 comprises a first conveyor belt 2, onto which there are applied known spacing pushers 3, interposed between each product of the flow and the subsequent one. The conveyor belt 2 is driven by a dedicated actuator 4, e.g. an associated known electromagnetic motor and optional driving members, them also conventional.
The apparatus 1 further comprises a second conveyor belt 5, arranged downstream of the first belt 2 with respect to the direction of the flow of products and it also driven by a dedicated actuator 6 that may be known.
Preferably, when the apparatus 1 is under working conditions the conveyor belts 2 and 5 move at a substantially constant speed.
The speeds of the belts 2 and 5 are controlled by a central control unit 100 of the apparatus 1 so as to meet the specific production needs and the kind of products that have to be packaged. The distinct and independent motor drive of the two belts 2 and 5 allows to control them just the one independently from the other one. In particular, by keeping constant the feed speed of the second belt 5 and decreasing that of the first belt 2 it is possible to obtain a greater relative distance between the products fed onto the second belt 5 itself. Of course, the same result can be obtained by keeping constant the speed of the first belt 2 and increasing the speed of the second belt 5. Vice versa, by increasing the speed of the first belt 2 at constant speed of the second belt 5—or by decreasing the speed of the second belt 5 at constant speed of the first belt 2—it is possible to decrease the relative distance among the products onto the second belt 5 itself.
Preferably, the choice will be that of keeping the constant speed of the first belt 2 and adjusting the speed of the second belt 5 thereto. Hence, by loading the first belt 2 according to a constant pitch imposed by the pushers 3, the relative distance between each product and the adjacent one thereonto will be all the greater the shorter their length is. In order to reduce the distance between the products onto the second belt 5, the more it is desirable to bring these products nearer, i.e. the more the latter are short, the lower the speed of the belt 5 should be with respect to the speed of the first belt 2.
In general, the adjustment of the relative distance between the products fed onto the belt 5 is needed for a correct operation of all the subsequent units of the apparatus 1 operating onto the flow of products conveyed thereonto.
The abovementioned unit 100, which controls the belts 2 and 5, controls also all of the other operating units of the apparatus 1.
As it is shown in greater detail in FIGS. 2 A and 2B, the second belt 5 feeds the products through a wrapping unit 7, in which the heat-sensitive material film F is positioned with respect to the flow of products so as to wrap them in a sort of single tubular wrapping.
For this purpose, the wrapping unit 7 comprises a bobbin 71, from which the film unwinds in the form of a continuous strip, and a laying system that lays the continuous strip of film onto the second conveyor belt 5, suitably positioning it with respect to the flow of products. In particular, when the products pass from the first belt 2 to the second belt 5, the continuous strip of film is interposed between the products 1 themselves and the second conveyor belt 5 onto which they lie.
As it is shown in FIGS. 2A and 2B, a folding device then folds the continuous strip of film about the products, so that a first longitudinal edge E and a second longitudinal edge L of the film F lie adjacent or overlapped the one to the other one. Since the wrapping unit 7 is known, a further description thereof will be omitted. Then, the flow of products crosses a processing unit 8, which will be referred to as longitudinal sealing unit. Therein, said first and second longitudinal edge E and L of the film F are longitudinally sealed the one to the other one. Thus, the single tubular wrapping that wraps the flow of products is longitudinally sealed about the latter. In the figures the unit 8 is depicted merely by way of example.
Since also the longitudinal sealing unit can be manufactured in a known way, a further description thereof will be omitted.
The packaging apparatus further comprises a transversal sealing unit 9. As it is schematically shown in FIG. 4A, in said unit 9 it is carried out, between each product of the flow and the subsequent one, just a transversal sealing between a first transversal portion B and a second transversal portion D of the film F, so as to form a wrapping I about each product. In other words, each pair of transversal portions B and D of the film F corresponds to a section of the continuous strip of film interposed between two contiguous products of the flow. Thus, from the abovementioned single tubular wrapping there are formed single wrappings I, each one wrapping a single product of the flow. Preferably, such a transversal sealing is pushed until causing the detachment of each sealed wrapping I from the single tubular wrapping arranged upstream thereof with respect to the flow of products.
Always with reference to said FIG. 4A, the transversal sealing unit 9 comprises a heat sealer 10, heated by means of resistors and apt to contact the film F to cause a partial or total melting thereof. The unit 9 further comprises a sealer receiving element 11, cooperating with the heat sealer 10 to produce said transversal sealing. In particular, in the present embodiment the sealer receiving element 11 is in the form of a plate positioned below the heat sealer 10, and the overall arrangement is such that the film to be sealed is interposed between the sealer receiving element 11 and the heat sealer 10 itself. At the sealer receiving element 11 the second conveyor belt is locally deviated by suitable transmission rollers.
Preferably, to the sealer receiving element 11 it is associated heating means, e.g. a resistor, and one or more temperature sensors apt to control the heating means itself, optionally by the control unit 100, so as to ensure that the sealer receiving element 11 be always at a desired temperature. Thus, it is avoided that the sealer receiving element 11 be excessively cold, thereby lowering the temperature of the film to be sealed into contact therewith, altering the sealing conditions with respect to the optimal ones.
According to a simplified variant embodiment, there can be provided also mere means for pre-heating, to be activated only at the starting of the apparatus 1, or heating means, operated at predetermined time intervals, for heating the sealer receiving element 11.
Moreover, according to a preferred embodiment shown in FIG. 4B, the transversal sealing unit 9 comprises means 15 for nearing the opposed film portions B and D prior to contact with the heat sealer 10 and/or with the sealer receiving element 11, arranged at the one and/or the other one. Such means 15 may be implemented, e.g., by one or more pairs of elongate elements, also called “straps”, arranged each at a side of the respective heat sealer element 10 or sealer receiving element 11. Such elongate elements may be made of or coated with Teflon and may be associated to elastic opposing elements such as, e.g., helical springs.
As schematically indicated in FIG. 1, the sealing assembly of the transversal sealing unit 9, and therefore the heat sealer 10 and the sealer receiving element 11, is movable in the direction of the flow of products, i.e., in the present embodiment, in the horizontal direction. Such a horizontal motion of said sealing assembly is caused by first driving means, which will presently be described with reference to FIG. 3. The integral transversal motion of translation of the heat sealer 10 and of the sealer receiving element 11 is obtained by mounting both said components onto a common trolley moved by said first driving means.
Moreover, in the present embodiment (FIG. 5A), both the heat sealer 10 and the sealer receiving element 11 are movable in a direction substantially orthogonal to that of the flow of products, i.e., with reference to the depicted example, in vertical direction, by second driving means distinct and independent from the hereto-introduced first driving means. Such second driving means will be detailed hereinafter with reference to FIG. 5A.
The first and the second driving means provide each a respective dedicated actuator, e.g. an electromagnetic motor, indicated by 14 and 18, respectively, always in FIG. 1.
To avoid excessive problems linked to the system inertia, preferably the second actuator 18 is not mounted onto the trolley effecting said transversal motion of the sealing assembly, rather being integral to the frame of the apparatus 1.
Concerning the first driving means, FIG. 3 shows just an exemplary kinematic diagram thereof according to the present embodiment. For simplicity's sake, in said figure the first actuating means has been depicted as acting directly on the sealer receiving element 11 instead of on said trolley onto which both said element 11 and the heat sealer 10 are mounted. Such first driving means, indicated by 110 in FIG. 3, is based on a connecting rod 12—crank 13 kinematic motion, the crank being set in rotation by said dedicated actuator 14. Moreover, the small end of the connecting rod 12 is rotationally connected to the sealer receiving element 11. Therefore, the sealing assembly 10-11 reciprocatingly translates in the sense of the flow and in the sense opposite thereto, depending on the position and the sense of rotation of the crank 13.
In brief, therefore, the heat sealer 10—sealer receiving element 11 assembly will alternatively cover a downstroke in the sense of the feed of the products, during which the actual transversal sealing takes place, and a backward stroke, with which the assembly returns to the initial position to carry out a new sealing at the opposite end of the product just processed. Moreover, at the end sections of said downstroke and backward stroke the heat sealer 10 and the sealer receiving element 11 move also in a direction orthogonal to the flow of products to rise/lower with respect to the product to be packaged, thereby avoiding to collide therewith, according to the modes that will presently be illustrated.
As highlighted in the introduction, the heat sealer 10 should remain into contact with the film for a predetermined and constant time period; hence the length of the downstroke section during which the heat sealer 10 is just into contact with the film is determined by the control unit 100 as a function of the speed of the film itself, i.e. of the strip 5.
In a connecting rod-crank mechanism of the kind described above with regard to the first driving means 110, the linear speed of the small end of the connecting rod, at constant angular speed of the crank, is variable over time according to a law that, roughly speaking, may be deemed sinusoidal. However, when said variable linear speed, entailing in particular continual accelerations and decelerations, is attributed to the sealer receiving element 11 and to the heat sealer 10 integral thereto, the transversal sealing is of poor quality; this because evidently the film to be sealed, fed with the flow of products, and the sealer 10—sealer receiving element 11 assembly would travel at substantially different speeds, with all the problems already highlighted in the introduction.
Hence, according to the invention, the dedicated actuator 14 is speed-controlled by the unit 100 according to an algorithm that can be likened to a so-called “electronic cam”, i.e., so as to obtain desired motion curves. In particular, according to the invention the actuator 14 is controlled so that the linear speed of the small end of connecting rod, i.e., of the sealer receiving element 11, is substantially constant and equal to that of the flow of products for all the actual time provided for the transversal sealing. An exemplary graph of such control modes is shown in FIG. 6. This graph reports just the speed v_Cof the sealer receiving element 11 as a function of its displacement (feed) x in the direction of the flow of products. The portion delimited by a broken line in the graph indicates the pattern exhibited by the speed without said control effect. As it is apparent in said graph, in the sealing section X, i.e. in the downstroke portion in which the heat sealer 10 is actually into contact with the heat-sensitive film, the linear speed of the heat sealer 10—sealer receiving element 11 assembly in the direction of the flow of products is substantially constant. With reference to FIG. 5A, the apparatus 1 further comprises said second driving means, here indicated by 17, apt to move the heat sealer 10 and the sealer receiving element 11 in a direction orthogonal to the flow of products. An exemplary kinematic scheme of said second means 17 is depicted just in FIG. 5A. With reference to this latter figure, the means 17 comprises said dedicated actuator 18 connected to a crank 20, the latter in turn hinged at one end to a connecting rod 21.
Moreover, a further rocker arm 211 is hinged to the connecting rod 21 at a median position thereof. The rocker arm 21 has a fulcrum 22, off-center with respect to the point of hinging onto the connecting rod 21.
Moreover, at opposite ends of the rocker arm 211 there are articulated two additional elements, indicated by 23 and 24, respectively, and integral to the heat sealer 10 and to the sealer receiving element 11, respectively.
The overall arrangement described hereto is such that at the start of the sealing section X the actuator 18 causes a rotation of the rocker arm 211 about its own fulcrum 22 such as to produce a lowering of the heat sealer 10 and a rising of the sealer receiving element 11, i.e. a nearing of such elements in a direction orthogonal to the flow of products. Vice versa, at the end of the sealing section X the actuator 18 is rotated in the opposite sense of rotation, so as to cause a rising of the heat sealer 10 and a lowering of the sealer receiving element 11, i.e. a moving away of such elements, always in said direction orthogonal to the flow.
Hence, the second means 17 allows to concomitantly modify the position of both elements, the heat sealer element 10 and the sealer receiving element 11, and not, like in known systems, merely that of heat sealer 10. Thus, as it can be better appreciated in FIG. 4A, both transversal edges of film to be sealed, i.e. the bottom edge D and the top one B, are correctly tensioned prior to the sealing, as the latter is carried out about at the center line of the product to be packaged. On the contrary, were the vertical position of the sealer receiving element 11 unmodifiable, the bottom edge D of the film would not be tensioned, with the risk of overtensioning and eventually tearing the top edge B, and the sealing would anyhow take place at the bearing plane of the second belt 5; therefore in a less-than-optimal position, both in terms of ease of management of the final cover and of correct tensioning of the edges.
As it is shown always in FIG. 5A, at the connecting rod 21 there can also be provided a pneumatic shock absorber 25.
For the same reasons, related to the quality of the transversal sealing, already outlined above as well as in the introduction, the relative speed between heat sealer 10 and sealer receiving element 11 in the contact section X is preferably nil. In a transversal direction, i.e. parallel to the flow of products, the speed components of the two elements 10 and 11 are alike, since, as mentioned hereto, they are mounted onto the same trolley.
Concerning the vertical component of the speed of said elements, the difference in speed can be related to the optional different distance of the elements 10-11 themselves from the fulcrum 22.
The control of the actuator 18 can be carried out so as to compensate any motion profile, in terms of acceleration, speed and/or position, optionally associated to the specific mechanical drive used and in general to any other cause of differences in speed between the elements 10 and 11. Hence, in order to obtain a substantially nil relative speed of said two elements 10 and 11 at the sealing section X, also the dedicated actuator 18 can be speed-controlled by the unit 100 according to an algorithm that can be likened to a so-called “electronic cam”. An exemplary graph of said relative speed is shown in FIG. 7. Such a graph reports just the vertical component of the speed v_S/Cof the heat sealer 10 with respect to the sealer receiving element 11 as a function of the feed x in the direction of the flow of products. As it is apparent in said graph, at the sealing section X the relative speed of the heat sealer 10 with respect to the sealer receiving element 11 is substantially nil.
Moreover, the control of the motion of the actuator 18 by the unit 100 is such as to maximize the lowering and rising acceleration of the heat sealer 10 and of the sealer receiving element 11 between adjacent products to be packaged, thereby avoiding the collision of said elements with said products and yet concomitantly maximizing the operating speed of the apparatus 1, also in the presence of long products.
Furthermore, the actuator 18 is controlled by the unit 100, always by an electronic cam control, to ensure that during the backward stroke of the sealing assembly 10-11 the distance between the two elements 10 and 11 remains substantially constant, and this also in order to avoid impacts with the products of the flow. In fact, the transversal motion of the carriage can cause a variation of the tilt of the rocker arm 211 of the second driving means 17, with an entailed variation of the relative position of the elements 10 and 11.
With reference to FIG. 5B, a simplified variant of the means for moving the sealing assembly 10-11 is depicted and described.
The actuator 18 is connected to a crank 20 commanding a connecting rod 21 directly connected to the heat sealer 10, which therefore is moved according to a vertical line with respect to the sealer receiving element 11, which, in this embodiment, is stationary onto the frame.
In this embodiment the connecting rod 22 comprises also a pneumatic shock absorber 25.
Thus, only the sealing element 10 follows the law of motion described above with reference to the entire sealing assembly 10-11.
Therefore, it is understood that the actuator 18, in both said embodiments (FIGS. 5A and 5B, respectively) operates so that the relative speed (v_S/C) of at least the heat sealer element 10 with respect to the flow of products movable along a feed direction A at said sealing section X is substantially nil.
In the first embodiment (FIG. 5A), also the heat sealer will have said relative speed substantially nil.
Returning to consider FIG. 1, the apparatus 1 further comprises a system for adjusting the working height of the sealing assembly 10-11 in a direction orthogonal to the flow of products prior to the start of the processing. Such a system substantially consists in a hoisting system provided with a dedicated actuator 16, e.g. an electromagnetic motor. Such a hoisting system acts onto the entire transversal sealing unit 9 described hereto. Therefore, said adjusting system allows to have the transversal sealing take place always at the center line of the product to be packaged, with the entailed advantages already illustrated above.
Returning to FIG. 1, the apparatus further comprises, downstream of the transversal sealing unit 9, a pair of drawing rollers, 26 and 27 respectively, opposedly arranged and apt just to draw each packaged product therebetween. The rollers 26 and 27 are driven by a dedicated actuator 28, e.g. an electromagnetic motor.
Preferably, the apparatus 1 comprises also means for adjusting the relative position of said drawing rollers 26 and 27 along the flow direction. E.g., in the present embodiment it is provided that the top roller 26 may be shifted in the direction of the flow of products with respect to the bottom roller 27. The top roller 26 is shifted back with respect to the bottom one, i.e. is shifted in a sense opposite to that of the flow of products, to draw products of reduced length. Vice versa, the top roller 26 is shifted in the sense of the flow of products, and arranged substantially aligned with the bottom roller 27, in case of products of greater length.
The control unit 100 can carry out its function even with the aid of sensors distributed in the different units of the apparatus 1. E.g., in the present embodiment there are provided position, speed and/or acceleration sensors onto the heat sealer 10 and/or onto the sealer receiving element 11 apt to allow a feedback control of the respective dedicated actuators.
It will be understood that the present invention is susceptible of several embodiments alternative to that described hereto. E.g., the transversal sealing unit may incorporate heat-sealing means of a kind different with respect to the heat sealer and sealer receiving element envisaged above.
it will be understood that the invention provides also a packaging method operating on a flow of products movable along a feed direction and apt to package each of said products into a respective wrapping of heat-sensitive film, comprising a step of transversal sealing as described above and, optionally, a preliminary step of wrapping and one of longitudinal sealing, them also according to what has been described hereto with reference to the apparatus of the invention.
By now, it will have been appreciated that the apparatus and the method of the invention are very flexible with respect to independent variations of the ranges of the motion of the heat sealer and of the sealer receiving element in a direction parallel and orthogonal to the flow of products. This allows to simply and reliably adjust the motion of the heat sealer and of the sealer receiving element to different thicknesses of the products to be packaged and to different operative speeds of the packaging apparatus.
Moreover, it will be appreciated that, by providing independent motor drives for the motion in the direction of the flow of products and in a direction orthogonal thereto, the apparatus and the method of the invention are extremely versatile with respect to the range of heights and lengths of workable products to be packaged. Likewise, the apparatus and the method of the invention allow to widen the range of viable operating speeds.
The present invention has hereto been described with reference to preferred embodiments thereof. It is understood that other embodiments afferent to the same inventive kernel may exist, all falling within the protective scope of the appended claims.

Claims

1-34. (canceled)

35. A film packaging apparatus, operating on a flow of products movable along a feed direction and apt to package each of said products into a respective wrapping of heat-sensitive film, comprising:

a transversal sealing unit, which in turn comprises:

heat sealer means, apt to seal transversal portions of the film transversally to said feed direction and along a sealing section of the path of the products; and

first driving means, apt to move said heat sealer means according to said feed direction, said first driving means comprising an actuator and mechanical drive means interposed between said actuator and said heat sealer means; and

a control unit, apt to control said actuator of said first driving means so that, at said sealing section, the speed of said heat sealer means in said feed direction is substantially equal to the speed of the flow of products.

36. The apparatus according to claim 35, wherein said control unit is apt to control said actuator of said first driving means so that the speed of said heat sealer means at said sealing section is substantially constant.

37. The apparatus according to claim 35, wherein said mechanic drive means of said first driving means is based on a connecting rod-crank kinematic motion.

38. The apparatus according to claim 35, wherein said transversal sealing unit comprises also second driving means, distinct from said first driving means and apt to move said heat sealer means in a direction substantially orthogonal to said feed direction.

39. The apparatus according to claim 38, wherein said second driving means comprises a respective dedicated actuator.

40. The apparatus according to claim 35, wherein said heat sealer means comprises at least one heat sealer element and at least one corresponding sealer receiving element, the overall arrangement being such that, in said sealing section, the transversal portions of film to be sealed are arranged between said elements.

41. The apparatus according to claim 40, wherein said first driving means is apt to move said heat sealer element and said sealer receiving element according to said feed direction.

42. The apparatus according to claim 40, wherein said transversal sealing unit comprises also second driving means, distinct from said first driving means and apt to move said heat sealer means in a direction substantially orthogonal to said feed direction, and wherein said second driving means is apt to simultaneously move said heat sealer element and said sealer receiving element in opposite senses.

43. The apparatus according to claim 42, wherein said second driving means comprises a rocker arm mechanism connected to said heat sealer element and sealer receiving element.

44. The apparatus according to claim 40, wherein said transversal sealing unit comprises also second driving means, distinct from said first driving means and apt to move said heat sealer means in a direction substantially orthogonal to said feed direction and comprising a respective dedicated actuator, and wherein said control unit is apt to control said dedicated actuator of said second driving means so that the relative speed (v_S/C) of at least said heat sealer element with respect to said flow of products movable along a feed direction at said sealing section is substantially nil.

45. The apparatus according to claim 40, wherein said transversal sealing unit comprises also second driving means, distinct from said first driving means and apt to move said heat sealer means in a direction substantially orthogonal to said feed direction and comprising a respective dedicated actuator, and wherein said control unit is apt to control said dedicated actuator of said second driving means so that the relative speed (v_S/C) of said heat sealer element and of said sealer receiving element with respect to said flow of products movable along a feed direction at said sealing section is substantially nil.

46. The apparatus according to claim 40, wherein said transversal sealing unit comprises also second driving means, distinct from said first driving means and apt to move said heat sealer means in a direction substantially orthogonal to said feed direction and comprising a respective dedicated actuator, and wherein said control unit is apt to control said dedicated actuator of said second driving means so that during a backward stroke of the sealing the relative distance between said sealer receiving element and heat sealer element remains substantially constant.

47. The apparatus according to claim 40, comprising means for adjusting the working height of said heat sealer element and/or sealer receiving element in a direction substantially orthogonal to said feed direction.

48. The apparatus according to claim 47, wherein said means for adjusting said working height comprises a respective dedicated actuator.

49. The apparatus according to claim 40, comprising means for pre-heating said sealer receiving element.

50. The apparatus according to claim 40, comprising means for heating said sealer receiving element and sensing means apt to control said heating means depending on the temperature of said sealer receiving element.

51. The apparatus according to claim 35, comprising means for nearing opposed transversal portions of film at said sealing section.

52. The apparatus according to claim 51, wherein said heat sealer means comprises at least one heat sealer element and at least one corresponding sealer receiving element, the overall arrangement being such that, in said sealing section, the transversal portions of film to be sealed are arranged between said elements and wherein said means for nearing opposed transversal portions of film is arranged at said heat sealer element and/or said sealer receiving element.

53. The apparatus according to claim 52, wherein said means for nearing comprises at least a pair of elongate elements arranged each at one side of a respective heat sealer or sealer receiving element.

54. The apparatus according to claim 35, comprising, upstream of said transversal sealing unit, a wrapping unit, wherein said film is positioned with respect to said flow.

55. The apparatus according to claim 35, comprising, upstream of said transversal sealing unit, a longitudinal sealing unit, for sealing longitudinal portions of said film parallelly to said feed direction.

56. The apparatus according claim 35, comprising means for drawing each packaged product, arranged downstream of said transversal sealing unit and driven by a dedicated actuator.

57. The apparatus according to claim 56, wherein said means for drawing comprises a pair of opposedly arranged drawing rollers.

58. The apparatus according to claim 57, comprising means for adjusting the relative positions of said drawing rollers along said feed direction.

59. The apparatus according to claim 35, comprising first conveying means, apt to feed the products to be packaged to said transversal sealing unit, and second conveying means for providing the products to be packaged through said transversal sealing unit, wherein said first and second conveying means have independent actuators.

60. The apparatus according to claim 35, comprising one or more position, speed and/or acceleration sensors arranged at said heat sealer means and apt to provide feedback signals to said control unit.

61. A packaging method operating on a flow of products movable along a feed direction and apt to package each of said products into a respective wrapping of heat-sensitive film, comprising a step of transversal sealing, in which transversal portions of the film are sealed transversally to said feed direction and along a sealing section of the path of the products, said step being carried out by heat sealer means driven by first driving means, apt to move such heat sealer means according to said feed direction, such first driving means comprising an actuator and mechanical drive means interposed between said actuator and said heat sealer means, in said step of transversal sealing said actuator of said first driving means being controlled so that, at said sealing section, the speed of the heat sealing means in said feed direction is substantially equal to the speed of the flow of products.

62. The method according to claim 61, wherein in said step of transversal sealing said actuator of said first driving means is controlled so that the speed of the heat sealer means at said sealing section is substantially constant.

63. The method according to claim 61, wherein said step of transversal sealing provides that a heat sealer element and a sealer receiving element of said heat sealer means be moved both in a feed direction by said first driving means and in a direction substantially orthogonal to said feed direction by second driving means, distinct from said first driving means and provided with a dedicated actuator.

64. The method according to claim 63, wherein said step of transversal sealing provides that said dedicated actuator of said second driving means be controlled so that the relative speed (v_S/C) of said heat sealer element with respect to said sealer receiving element at said sealing section is substantially nil.

65. The method according to claim 63, wherein said dedicated actuator of said second driving means is controlled so that during a backward stroke of the sealing the relative distance between said sealer receiving element and said heat sealer element remains substantially constant.

66. The method according to claim 63, providing a step of adjusting the working height of said heat sealer element and sealer receiving element in a direction substantially orthogonal to said feed direction.

67. The method according to claim 61, providing, upstream of said step of transversal sealing, a step of wrapping, wherein said film is positioned with respect to said flow.

68. The method according to claim 61, providing, upstream of said step of transversal sealing, a step of longitudinal sealing, for sealing longitudinal portions of said film parallelly to said feed direction.