PatentDe  


Dokumentenidentifikation EP1465808 29.12.2005
EP-Veröffentlichungsnummer 0001465808
Titel VORRICHTUNG ZUM SIEGELN DER ÜBERLAPPENDEN RÄNDER EINES FOLIENSCHLAUCHES
Anmelder A.W.A.X. Progettazione e Ricerca S.r.l., Vignola, Modena, IT
Erfinder RIMONDI, Renato, I-40053 Bazzano, IT
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 60302430
Vertragsstaaten AT, BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HU, IE, IT, LI, LU, MC, NL, PT, RO, SE, SI
Sprache des Dokument EN
EP-Anmeldetag 03.07.2003
EP-Aktenzeichen 037404118
WO-Anmeldetag 03.07.2003
PCT-Aktenzeichen PCT/EP03/07120
WO-Veröffentlichungsnummer 0004009450
WO-Veröffentlichungsdatum 29.01.2004
EP-Offenlegungsdatum 13.10.2004
EP date of grant 23.11.2005
Veröffentlichungstag im Patentblatt 29.12.2005
IPC-Hauptklasse B65B 51/20
IPC-Nebenklasse B65B 51/26   B29C 65/10   

Beschreibung[en]

The invention relates to an apparatus for the continuous tight heat-sealing of the longitudinal overlapping edges of tubular pieces generally of thermoplastic film, the thickness of which may be limited, the apparatus being particularly suitable for machines for packaging products in barrier-effect stretch film, as disclosed in document WO 03/051715, published on 26 June 2003.

In this type of machine, the technical problem that had to be solved was to do with the continuous tight longitudinal sealing of the overlapping edges of the packaging film as it passes over the tubularizing mandrel. It has been impossible to find, either on the market or in the known literature, an apparatus capable of solving this technical problem. It should be remembered that the film used is characterized by high grip, high extensibility and limited thickness, of the order of tens of microns, e.g. about 40 microns. The seal must be formed and interrupted rapidly, in a few hundredths of a second, on a film which begins with a standing start, advances rapidly at speeds of for example more than 0.6 metres per second, and then stops again. The seal to be formed on the longitudinal edges of the film must be extremely reliable, absolutely tight, must be elastic so as to react without defects to the stretching applied to the film, must not form hard beads that could damage packagings with which the seal comes into contact when the packagings are stacked, and must also be visually pleasing.

Sealing thermoplastic materials by means of a hot air flow is not new in packaging and wrapping technology.

Document WO 98/40202 discloses an apparatus for the tight sealing of longitudinal overlapping edges of thermoplastic film comprising a sealing head for directing hot compressed air from a generator to the overlapping edges and means for approach and withdrawal of the sealing head, in accordance with the preamble of claim 1.

According to the invention, there is provided an apparatus for the continuous tight heat-sealing of the longitudinal overlapping edges of tubular pieces of thermoplastic film, the thickness of which may be limited, produced by unwinding the film from a reel and advancing the said film longitudinally through a tubularizing mandrel, which apparatus comprises:

  • a) means for guiding and for holding the said longitudinal edges of the tubularized film so that they overlap with an intimate and sufficiently distributed contact and
  • b) in an opposing position, a short distance from these guide means, a sealing head made in a material with good mechanical strength, with a low coefficient of friction in relation to the film to be sealed and with a high degree of thermal insulation, which directs onto the edges of the film to be sealed at least one continuous jet of air or other gas, heated to an appropriate temperature and at an appropriate pressure, which is connected by flexible or jointed means to a fixed generator of hot compressed air controlled by suitable supply and control means and which is mounted on means of approach and withdrawal, such that, when the film advances, the said head is placed at the correct time a short distance from the said film and already fully operational, whereas when the film stops, at the correct time the head is withdrawn from the said film; characterized in that
the means for guiding the edges of the film to be sealed longitudinally comprise a flat fixed opposing block of suitable thickness, over which the said edges of the film slide, this opposing block being appropriately rounded at its edges and being made in a suitable engineering polymer, and in that

immediately downstream of the opposing block is a further guide means that acts on the opposite face of the overlapping edges of the film from that on which the opposing block acts, this in order to ensure constant contact between the film and the opposing block, the further guide means also being made preferably in a suitable engineering polymer.

These and other features of the invention, and the advantages procured thereby, will be made clearer by the following description of a preferred embodiment thereof, illustrated purely by way of non-restrictive example in the figures of the accompanying plates of drawings, in which:

  • Fig. 1 is a side view with parts in section of the principal components of the packaging machine for which the present sealer has been expressly designed;
  • Fig. 1a is a schematic plan view of the principal working components of the packaging machine at the same stage as in Figure 1;
  • Fig. 2 is a rear end view with parts in section of the workstation of the packaging machine as in Figure 1, showing the supply circuit of the present sealer;
  • Fig. 3 is a side view with parts in section of the sealer in the high or working position;
  • Fig. 4 is a plan view of the head of the sealer;
  • Figs. 5 and 6 illustrate the principal components of the machine as in Figure 1, in successive stages of their working cycle; and
  • Fig. 7 illustrates schematically a diagram of the high or low position of the sealer in relation to the progress of the film through the tubularizing mandrel of the packaging machine.

Figure 5 shows that the machine referred to unwinds the stretch film 5 from the supply reel, assisted by rolls 27, 127; inserts this film into a horizontal mandrel 1 supported by means 101, to form a wrapping tube 5' sealed tightly along the overlapping longitudinal edges by a lower means 6; holds and closes the front end of said wrapping tube by a transverse pincer 7 which forms a double seal and an intermediate cut; and inserts the product P to be packaged through the said film-tubularizing mandrel, by means of a tubular guide 1' supported by means 14 and by means of a pusher 4, for introducing the product into the said tubular packaging, at a short distance from its closed front end which is held by the said transverse pincer 7 which advances horizontally away from the said forming mandrel. When the tubular wrapping containing the product has passed a sufficient distance out of the forming mandrel in proportion to the dimensions of the product, see Fig. 6, the film 5 is stopped and braked transversely by the activation of a brake 28 that stops the rolls 27, with the rubber-coated roll 127, while the said front pincer 7 continues to advance so as to stretch lengthwise by an appropriate amount the length of tubular wrapping, which progressively lengthens and which by reaction constricts transversely and clings tightly to the product inside it. When the product P is fully out of the assembly of the tubularizing mandrel 1 and is sufficiently distant from it (Fig. 1), the rear end of the stretched packaging is gripped transversely by a second pincer 7' which makes two transverse seals and one intermediate cut, to close the rear end of the packaging with the product and to hold it at the rear end, while the front pincer 7 opens, reverses back to the start-of-cycle position and leaves the packaged product standing on the comb 10' connected to the lower component of the pincer 7' which is active. The latter pincer holds the head end of the new tube of film coming out of the forming mandrel and the work cycle is repeated as described above. At the correct time relative to the rear closure of each packaging the brake 28 is released and the transverse clamping of the film, which had earlier allowed the completed packaging to be stretched longitudinally, is discontinued to avoid tearing of the film and to allow more tubular packaging film to be fed in, while the packaging formed in the previous cycle is carried away from the sealing and cutting pincer which is active and in the phase when this pincer is open, the said packaging is placed on a comb conveyor 11 which carries it away.

With this machine it is possible to make packagings that are not only secured tightly around the product but also completely tight, so that by using stretch film that is impermeable to gases or to certain gases, the packagings may be found useful for improving the preservation of fresh fruit and vegetable products, by limiting the migration of oxygen and encouraging the removal of carbon dioxide, or suitable for containing products in a modified atmosphere. For this latter purpose, special means are used to condition the atmosphere in the tubular packaging before its rear end is closed or to carry out the entire packaging operation in a modified-atmosphere chamber. In Figure 1, the number 29 denotes the main machine computer, with the programming and interrogation input 129. The computer 29 receives the electrical signal from the means 30 that sense the dimensions of the product P to be packaged, in response to which the computer will control by logic means, after the lifter 3 has cyclically raised one product from the supply line 2, the stroke of the pusher 4 which inserts the raised product through the guide 1', followed by the horizontal stroke of the pincers 7, 7', then the electromagnetic brake 28, the activation and deactivation means of the longitudinal sealer 6, and other working parts of the machine which have not been discussed here as being unnecessary to an understanding of the invention, including those which optionally inject preservative gases into the cyclically formed packaging.

It can be seen in Figures 1, 1a, 2 and 3 that in an opposing position to the sealing device 6, there is attached to the lower outer face of the bottom wall of the tubular guide 1' through which the product P is fed a flat opposing block 31 made in a suitable engineering polymer with a low coefficient of friction in relation to the film and with good properties of thermal insulation, consisting of a rectangular plate with bevelled edges which are in part fixed by screws or rivets to the said guide 1' and which is orientated so that its greatest dimension is in the direction of advance of the film. The opposing block 31 is housed with play in the central slits 32 (Fig. 1a) of the lower and mutually overlapping flanges of the forming mandrel 1 and its thickness is such that the longitudinal edges of the film controlled by these flanges overlap each other and touch each other as they slide over the component 31, as indicated in chain line in Figure 2. In Figures 2 and 3 it is also clear that immediately downstream of the opposing block 31, there are attached to the lower flanges of the mandrel 1 the ends of the spindle 133 of a cylindrical roller 33, set transversely to the direction of advance of the film and made for example in the same engineering polymer as the opposing block 31, its top being set at the same level as or preferably higher than the lower face of the said opposing block 31, so that, as the outer face of the longitudinal edges of the film pass over this roller, their inside face is kept pressed against the opposing block 31.

As can also be seen with reference to Figure 4, there is underneath and parallel to the opposing block 31, arranged centrally and in longitudinal alignment, the flat upper face 34 of the sealing head 6, formed by an essentially parallelepiped-shaped body, bevelled along the tops of its long sides and tapering at the bottom, and made in a suitable engineering polymer with good properties of mechanical strength, a low coefficient of friction in relation to the film and a high level of thermal insulation. The upper face 34 of the head 6 has one dimension approximately equal to or little different from that of the lower face by which the opposing block 31 operates in contact with the film to be sealed. Two longitudinal slits 35 are formed symmetrically in this face 34: their width may be for example about 0.3 mm and their separation about 6 mm; on the underside they lead into a horizontal cylindrical chamber 36 of appropriate volume, for example having a diameter of about 13 mm, which by means of a lower duct 136 is in communication with a flexible tube 38, made of a high-temperature-resistant material, connected to the discharge port 139 of the generator 39 which supplies hot air at a temperature of between 150 and 190°C, for example about 170°C, and at a pressure of between 0.1 and 0.8 bar, for example about 0.2-0.4 bar. It will be understood that the abovementioned values of pressure and temperature and other parameters discussed earlier relative to dimensions and/or positioning of the apparatus have to do with the use of a barrier-effect stretch-type packaging film with a thickness of about 40 microns, so it is obvious that the said values and parameters may be modified in the light of simple experiments for film of different characteristics. Via the pipe 239 and a pressure reducer 40, the generator 39 is connected to the source of compressed air, while the terminal 339 of the same generator is connected electrically to a supply interface 41 controlled by a processor 42 which senses the temperature of the hot air emitted by the generator 39, by means of a sensor 43 positioned for example in the discharge port 139 and connected to a programming and control unit 44. A sensor 143, of pressure type for example, is provided on the circuit supplying the compressed air to the generator 39 and it too is connected to the processor 42. By means of the supply and control chain 41-44, 143, it is possible to keep the operating parameters of the present sealer at constant and predetermined values. In the event of an anomaly, the terminal 142 of the processor 42 informs the computer 29 of the problem and the computer 29 moves the sealer 6 to the rest position and activates the emergency procedures.

As can be seen in Figures 1, 3 and 4, the head 6 is attached by its base to a linear lifting and lowering actuator of any suitable type, e.g. to the non-rotating rod 145 of a double-acting pneumatic cylinder 45 controlled by means of a solenoid valve 50 by the main computer 29 and attached by means of its body to the side projection 146 of a small slide 46 which travels on end bushes up and down a pair of vertical rods 47, the latter in turn being mounted with downward orientation on a crossmember 60 of the machine frame at right angles to the direction of film advance. The rods 47 are enclosed in springs 48 which push the slide 46 down the said slide having, fixed rotatably to it midway between these rods, an upside-down adjusting screw 49 which is screwed to the crossmember 60. When the rod 145 of the cylinder 45 is in the high position, turning the screw 49 defines an appropriate distance between the upper face 34 of the sealing head 6 and the opposing block 31, for example a value of about 0.8-1 mm. When the rod of the cylinder 45 is lowered, the sealing head 6 is withdrawn a suitable distance from the sealed film so that the hot compressed air emerging from the slits 35 of the said head is dispersed into the environment and does not injure the film held immobile above it in the forming mandrel 1. It will be understood that suitable means can be provided to deflect away from the film the hot compressed air emerging from the sealing head 6 in the low or rest position. For this purpose screens may be provided and activated automatically when the head 6 descends, or the solution shown in Figure 1 may be used, in which a horizontal knife of cold compressed air 151 is directed over the head 6 when in the low position: this air knife physically cuts the hot rising airflow and disperses it into the environment. The air knife 151 may be emitted by a short fixed bar 51 for example on the crossmember 60 and having an upwardly-oriented emitting nozzle 251 that supplies an appropriate flow of cold air to the sealed portion of film emerging from the present longitudinal sealing apparatus, immediately downstream of the guide roller 33, so as to stabilize the completed seal. It will however be understood that in order to limit the consumption of compressed air by the packaging machine, reduce the sources of noise and optionally also limit the wastage of heat energy, it is conceivable for the discharge port 139 of the generator 39 to be fitted with a deflecting box, controlled by the computer 29 using an appropriate interface, in order to intercept at the requisite moment and possibly recycle the hot air produced by this generator 39 during periods when the sealing head 6 is not active. This solution has not been illustrated, but it should be understood to be protected inasmuch as it may easily be carried out by those skilled in the art on the basis of the account given herein.

The sealing apparatus as described operates in the following manner.

In Figure 5 it can be seen that when the pincer 7 is closed on the head of the tubularized film 5' emerging from the forming mandrel 1 and when this pincer prepares to move away from the mandrel, the sealing head 6 is in the raised position so as to form on the longitudinal edges of the film sliding across the mandrel 1, two parallel continuous tight sealing beads. In the diagram shown in Figure 7, the curves marked 52 f(5) and 53 f(6) relate respectively to the advancing of the film 5 and to the high or low position of the sealing head and the beginning 152 and 153 of each of these curves shows the phase of Figure 5. In the phase of Figure 1, when the film is clamped by the rolls 27, 127 and by the brake 28, and its advance is arrested as indicated at 252 in Figure 7, at the correct time the sealing head 6 is lowered as indicated at 253 in the same Figure 7. In the phase of Figure 1, the tubular packaging 5' with the product inside is stretched longitudinally and the tail end of the longitudinal seal of the film does not move significantly relative to the opposing block 31, because the film stretches mostly in the section downstream of the forming mandrel, owing in part to a suitable thermal treatment applied to the film by means which are not discussed here, being unnecessary to an understanding of the invention. Following stretching, at the right time relative to the closing of the pincer 7' the brake 28 comes off to allow enough film to advance through the forming mandrel to prevent the film being tom by the pincer 7'. During this phase the film advances by a small amount as indicated at 352 and the sealing head 6 is rapidly raised and lowered as indicated at 353 in the same graph, Figure 7, and as illustrated in broken lines and solid lines in Figure 5, thus ensuring continuity of the longitudinal seal of the overlapping edges of the film. Subsequently, when the pincer 7' begins to move away from the forming mandrel, the cycle is repeated with the longitudinal advance of the film as marked at 152' and with the raising of the sealing head 6 at the appropriate time, as indicated at 153' in the graph, Figure 7.

It will be understood that the description has referred to a preferred embodiment of the invention, to which it is possible to make many variations and modifications of construction, which may derive from the use of the longitudinal sealing apparatus in packaging machines other than that illustrated or in machines for forming bags, carrier bags etc., such as the type disclosed in Italian patent application No. BO2001A-91 belonging to this applicant. The pneumatic cylinder 45 can be replaced with some other linear actuator, such as a screw-and-nut or equivalent actuator powered by a motor with electronic control of speed and phase, so that the head 6 can be moved with gradients of acceleration and deceleration and, with speeds and phases controllable with greater ease by the main computer 29.


Anspruch[de]
  1. Vorrichtung zum kontinuierlichen dichten Verschweißen von überlappenden Längskanten von schlauchförmigen Stücken thermoplastischer Folie, deren Dicke begrenzt sein kann, welche Stücke durch Abwickeln der Folie von einer Rolle und Vorschub dieser Folie in Längsrichtung über ein Schlauchformelement (1) ergibt, wobei die Vorrichtung Mittel (31, 33) zum Führen und Halten der Längskanten der schlauchförmig gelegten Folie aufweist, so dass diese einander mit engem und ausreichend verteilten Kontakt überlappen, wobei die Vorrichtung ferner einen den Führungsmitteln in geringem Abstand gegenüber angeordneten Schweißkopf (6) aufweist, der aus einem Material mit einer hohen mechanischen Festigkeit, einem gegenüber der zu verschweißenden Folie geringen Reibungskoeffizienten und mit einem hohen Maß an Wärmeisolierung hergestellt ist, der auf die zu verschweißenden Folienkanten mindestens einen kontinuierlichen Strahl von Luft oder einem anderen Gas richtet, das auf geeignete Temperatur erwärmt ist und bei unter geeignetem Druck steht, wobei der Schweißkopf mittels flexiblen oder gelenkigen Mitteln (38) mit einem festen, durch geeignete Versorgungs- und Steuer- bzw. Regelungsmittel (40-44) kontrollierten Erzeuger für heiße Druckluft (39) verbunden und an einer Vorschub- und Rückzugseinrichtung (45) angeordnet ist, so dass beim Vorlauf der Folie der Schweißkopf zur richtigen Zeit in geringem Abstand von der Folie positioniert und bereits voll einsatzfähig ist, während bei einem Stopp der Folie der Schweißkopf von der Folie zum richtigen Zeitpunkt zurückgezogen wird; dadurch gekennzeichnet, daß die Mittel zur Längsführung der zu verschweißenden Folienkanten einen flach fixiertes Widerlager (31)geeigneter Dicke aufweisen, über das die Folienkanten gleiten, wobei das Widerlager an seinen Kanten in geeigneter Weise abgerundet ist und aus einem geeigneten technischen Polymer besteht, und dadurch, dass in Durchlaufrichtung direkt hinter dem Widerlager (31) ein weiteres Führungsmittel (33) angeordnet ist, dass auf die dem Widerlager gegenüberliegende Seite der überlappenden Folienkanten wirkt, um einen ständigen Kontakt zwischen der Folie und dem Widerlager sicherzustellen, wobei dieses weitere Führungsmittel vorzugsweise auch aus einem geeigneten technischen Polymer besteht.
  2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß das weitere Führungsmittel (33) aus einer Rolle besteht, die mit ihrer Achse (133) rechtwinklig zu der Bewegungsrichtung der Folie angeordnet ist.
  3. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der Schweißkopf (6) aus einem geeigneten technischen Polymer gefertigt ist.
  4. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß in stirnseitiger Ansicht Transportrichtung der Folie gesehen der Schweißkopf (6) eine im wesentlichen rechteckige Form aufweist, wobei die oberen Längsseiten abgeschrägt sind und die Oberseite (34) des Schweißkopfs eine Grundfläche aufweist, die im wesentlichen gleich oder nur wenig abweichend von der wirksamen Grundfläche des Widerlagers (31) ist, über das die zu verschweißenden Folienkanten gleiten.
  5. Vorrichtung nach Anspruch 4, dadurch gekennzeichnet, daß der Schweißkopf (6) an seiner Oberseite mindestens einen rechteckigen Schlitz (35) aufweist, dessen Abmessungen an die Dicke und Eigenschaften der zu verschweißenden Folie angepasst sind, wobei der Schlitz sich mit seiner größten Ausdehnung in Transportrichtung der Folie erstreckt und mit einer in dem Schweißkopf ausgebildeten, ein geeignetes Volumen aufweisenden Pufferkammer (36) in Verbindung steht und über verzweigte Kanäle (136) mit den flexiblen und hitzeresistenten Rohrleitungen (38) von dem heiße Druckluft bereitstellenden Generator (39) verbunden ist.
  6. Vorrichtung nach Anspruch 5, dadurch gekennzeichnet, daß an der Oberseite (34) des Schweißkopfs (36) zwei offene rechteckigen Schlitzen (35) symmetrisch angeordnet sind , um längs der überlappenden Kanten der Folie zwei kontinuierliche Verschlussnähte zum sicheren Abdichten zu erzeugen.
  7. Vorrichtung nach Anspruch 5, , dadurch gekennzeich- net, daß die Schlitze (35) in dem Schweißkopf (6) eine Breite von ungefähr 0,3 mm haben, um Dehnungsfolie mit eine Sperreffekt mit einer Dicke von ungefähr 40 Mikrometer zu verschweißen.
  8. Vorrichtung nach Anspruch 7, dadurch gekennzeichnet, daß die Schlitze (35) in dem Schweißkopf (6) durch einen Abstand von ungefähr 6 Millimeter voneinander getrennt sind.
  9. Vorrichtung nach Anspruch 5, dadurch gekennzeichnet, daß zum Verschweißen von Sperreffekt-Dehnfolie mit einer Dicke von ungefähr 40 Mikrometer Strahlen heißer Luft aus den Schlitzen (35) in dem Schweißkopf mit einer Temperatur zwischen 160° bis 180°, z.B. 170° und einem Druck zwischen 0,1 und 0,8 Bar, z.B. ungefähr 0,2 bis 0,4 Bar, austreten.
  10. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß der die heiße Druckluft bereitstellende Generator (39) mit seinem Lufteinlass (239) mit einer die Druckluft bereitstellenden Quelle über einen Druckminderer (40) verbunden ist, während eine von einem Prozessor (42) gesteuerte elektrische Versorgungsschnittstelle (41) über einen elektrischen Anschluss (339) mit dem Generator verbunden ist, wobei der Prozessor (42) die Betriebstemperatur und den Druck des Generators mittels Wärmesensoren und Drucksensoren (143) ermittelt und mit einer Programmier- und Steuereinheit (44) verbunden ist, die mit einer Ausgabeeinrichtung ausgerüstet ist, die im Falle einer Unregelmäßigkeit dem Hauptcomputer der Verpackungsmaschine anzeigt, dass der Schweißkopf (6) angehalten werden muss und die Notfallmaßnahmen eingeleitet werden müssen.
  11. Vorrichtung nach Anspruch 10, , dadurch gekennzeich- net, daß der Wärmesensor (43) und der Drucksensor (143) des Heißdruckluftgenerators (39) an der Ablassöffnung (139) bzw. am Einlassanschluss (239) des Generators angeordnet sind.
  12. Vorrichtung nach Anspruch 10, dadurch gekennzeich- net, daß während eines normalen Betriebs der Schweißkopf (6) kontinuierlich mit einem regulären Ausstoß arbeitet, und daß abschirmende Mittel eingesetzt werden, um den aus dem Schweißkopf austreten heißen Druckluftstrom abzulenken, wenn der Schweißkopf abgesenkt wird, um ihn von der Folie wegzubewegen, weil die Folie stillsteht,.
  13. Vorrichtung nach Anspruch 12, dadurch gekennzeich- net, daß die Ablenkmittel aus einem horizontal angeordneten kalten oder Raumtemperatur aufweisenden scharfen Druckluftstrahl (151) bestehen, der mittels einer kurzen, fixierten Leiste (51) ausgestoßen wird, wobei der Schweißkopf (6) auf ein niedrigeres Niveau als die Leiste gebracht wird, wenn er in der unteren oder der Ruheposition ist.
  14. Vorrichtung nach Anspruch 13, dadurch gekennzeich- net, daß die kurze feststehende Leiste (51), die den Luftstrahl (151) ausstößt, um den von dem Schweißkopf in der Ruheposition ausgestoßenen Luftstrom abzuschirmen, mit einer Düse (251) versehen ist, die einen Strom Kühlluft auf die kontinuierlichen, von dem Schweißkopf (6) in der Betriebsstellung hergestellten Schweißnähte ausstößt.
  15. Vorrichtung nach Anspruch 10, dadurch gekennzeich- net, daß an der Austrittsöffnung des Heißdruckluftgenerators (39) eine Deflektorvorrichtung angeordnet sein kann, die phasengleich mit der Aufwärts- oder Abwärtsbewegung des Schweißkopfes (6) ihren Zustand wechselt, um den Schweißkopf mit dem Schweißfluid zu versorgen oder dieses in eine andere Richtung abzulenken, wobei wahlweise ein Rückgewinnungs- oder Rücklaufkreislauf vorgesehen sein kann und das Ganze so ausgestaltet ist, dass beim Anheben des Schweißkopfes dieser sofort vollkommen betriebsbereit ist.
  16. Vorrichtung nach Anspruch 1, dadurch gekennzeich- net, daß der Schweißkopf an dem beweglichen Teil eines geradlinigen Stellantriebs (45) befestigt ist, der auf einem in einer Führung (47) beweglichen Schlitten (46) parallel zu der Bewegung des Stellantriebs gelagert ist, wobei der Schlitten in eine Richtung durch elastische Mittel (48) gedrängt wird und in die entgegengesetzte Richtung mittels einer Justierschraube (49) bewegbar ist, wobei es möglich ist, den Abstand des Schweißkopfes (6) in der gebrauchsbereiten Stellung zum Schweißen der Folie einzustellen.
  17. Vorrichtung nach Anspruch 16, dadurch gekennzeich- net, daß der Stellantrieb ein doppelt wirkender Flüssigkeitsdruckzylinder mit einem nicht drehbaren Stößel ist.
  18. Vorrichtung nach Anspruch 16, dadurch gekennzeich- net, daß der geradlinige Stellantrieb (45) durch einen Motor mit einer elektronischen Regelung oder Steuerung der Geschwindigkeit und Phase geregelt oder gesteuert werden kann, so dass der Schweißkopf (6) mit geeigneter Beschleunigung und Verzögerung izu der Folie hin und von dieser weg bewegt werden kann, die mit dem Starten und Stoppen der Folie korreliert ist.
  19. Vorrichtung nach Anspruch 2, gekennzeichnet durch die Verwendung in einer Maschine zum Verpacken von Produkten in Dehnfolie mit Sperrwirkung, die ein horizontal angeordnetes Schlauchformelement (1) aufweist, wobei die überlappenden Längskanten der Folie unterhalb des Schlauchformelements dicht durch spezielle Mittel (6) verschweißt werden, und die eine feststehende röhrenförmige Führung 1' aufweist, die in Längsrichtung durch das Schlauchformelement greift, um das zu verpackende Produkt in die schlauchförmige Verpackung einzubringen, die dem Schlauchformelement vorgeschaltete Mittel (27, 127, 28) zur steuer- bzw. regelbaren Versorgung mit Verpackungsfolie aufweist, und die dem Schlauchformelement nachgeschaltet zugreifende Greifer (7, 7') zum doppelten Verschweißen und zwischenzeitlichen Abschneiden aufweist, die zwischen einer Position vor und hinter dem Produkt in der schlauchförmigen Verpackungstasche hin und her wechseln, um die Verpackungstasche durch ein voriges Strecken der Folie in Längsrichtung zu formen, dadurch gekennzeichnet, dass das Widerlager (31), an das die zu verschweißenden Längskanten der Folie gedrückt und entlang dessen sie geführt werden, an der Außenseite der Bodenwand der Führung (1') angeordnet ist, während die Führungsrohre auf ihrer Achse (133) an den unteren Kanten des Schlauchformelements (1) montiert sind, das einen großen Schlitz (32) aufweist, durch den das Widerlager hindurchgeht und durch den die überlappenden Kanten der Folie sichtbar sind und durch den Schweißkopf aufbereitet werden können, wobei der von dem Hauptcomputer (29) gesteuerte bzw. geregelte Stellantrieb (45) zum Anheben und Absenken so synchronisiert ist, dass der Schweißkopf in der oberen Position ist, während die Folie vorläuft und in der unteren Position ist, wenn die Folie gestoppt ist, wobei der Schweißkopf zeitweise während der Phase des Strecken der Verpackungen in Längsrichtung angehoben wird, bevor das Ende der Verpackung verschlossen wird.
Anspruch[en]
  1. Apparatus for the continuous tight heat-sealing of the longitudinal overlapping edges of tubular pieces of thermoplastic film, the thickness of which may be limited, produced by unwinding the film from a reel and advancing the said film longitudinally through a tubularizing mandrel (1), which apparatus comprises means (31, 33) for guiding and for holding the said longitudinal edges of the tubularized film so that they overlap with an intimate and sufficiently distributed contact and in an opposing position, a short distance from these guide means, a sealing head (6) made in a material with good mechanical strength, with a low coefficient of friction in relation to the film to be sealed and with a high degree of thermal insulation, which directs onto the edges of the film to be sealed at least one continuous jet of air or other gas, heated to an appropriate temperature and at an appropriate pressure, which is connected by flexible or jointed means (38) to a fixed generator of hot compressed air (39) controlled by suitable supply and control means (40-44), and which is mounted on means of approach and withdrawal (45), such that, when the film advances, the said head is placed at the correct time a short distance from the said film and already fully operational, whereas when the film stops, at the correct time the head is withdrawn from the said film; characterized in that

    the means for guiding the edges of the film to be sealed longitudinally comprise a flat fixed opposing block (31) of suitable thickness, over which the said edges of the film slide, this opposing block being appropriately rounded at its edges and being made in a suitable engineering polymer, and in that

    immediately downstream of the opposing block (31) is a further guide means (33) that acts on the opposite face of the overlapping edges of the film from that on which the opposing block acts, this in order to ensure constant contact between the film and the opposing block, the further guide means also being made preferably in a suitable engineering polymer.
  2. Apparatus according to Claim 1, in which the said further guide means (33) consists of a roller positioned with its axis (133) perpendicular to the direction of advance of the film.
  3. Apparatus according to Claim 1, in which the sealing head (6) is made in a suitable engineering polymer.
  4. Apparatus according to Claim 1, in which the sealing head (6), viewed end-on in the direction of advance of the film to be sealed, is of an essentially rectangular shape, with the upper long sides bevelled, and the upper face (34) of the head has a footprint essentially the same as or little different from the effective footprint of the said opposing block (31) over which the edges of the film to be sealed slide.
  5. Apparatus according to Claim 4, in which there is open, on the upper face (34) of the sealing head (6), at least one rectangular slit (35) whose dimensions are correlated to the thickness and characteristics of the film to be sealed, the slit being oriented so that its greatest dimension is in the direction of advance of the film and communicating with a buffer chamber (36) of suitable volume formed inside the said head and connected by branched ducts (136) to the flexible and heat-resistant pipe (38) leading from the generator (39) supplying hot compressed air.
  6. Apparatus according to Claim 5, in which there are open, on the upper face (34) of the sealing head (6), two rectangular slits (35) symmetrically arranged to produce on the overlapping edges of the film two continuous longitudinal seals to ensure tightness.
  7. Apparatus according to Claim 5, characterized in that in order to seal barrier-effect stretch films with a thickness of about 40 microns, the said slits (35) in the sealing head (6) have a width of about 0.3 mm.
  8. Apparatus according to Claim 7, in which the slits (35) in the sealing head (6) are separated by a distance of about 6 mm.
  9. Apparatus according to Claim 5, characterized in that in order to seal barrier-effect stretch films with a thickness of about 40 microns, jets of hot air pass out through the slits (35) in the sealing head at a temperature of between 160 and 180°C, for example about 170°C, and at a pressure of between 0.1 and 0.8 bar, for example about 0.2-0.4 bar.
  10. Apparatus according to Claim 1, in which the generator (39) supplying the hot compressed air is connected by its air inlet (239) to a source supplying compressed air, through a pressure reducer (40), while its electrical terminal (339) connects the generator to an electrical supply interface (41) controlled by a processor (42) which, by means of heat sensors (43) and pressure sensors (143), senses the operating temperature and pressure, respectively, of the generator, which is connected to a programming and control unit (44) and which is equipped with an output terminal (142) which in the event of an anomaly tells the general computer (29) of the packaging machine that the sealing head (6) must be rested and the emergency measures activated.
  11. Apparatus according to Claim 10, in which the heat sensor (43) and the pressure sensor (143) of the hot compressed air generator (39) are located at the discharge port (139) and at the inlet port (239), respectively, of the said generator.
  12. Apparatus according to Claim 10, in which, in normal operating situations, the sealing head (6) works continuously at normal output and, when lowered to move it away from the film because the film is stationary, screening means are activated to deflect the flow of hot compressed air emerging from the head.
  13. Apparatus according to Claim 12, in which the said screening means consist of a horizontal cold or room-temperature compressed-air knife (151) emitted by a short fixed bar (51), the said sealing head (6) moving to a lower level than this bar when in the low or rest position.
  14. Apparatus according to Claim 13, in which the short fixed bar (51) that emits the air knife (151) to screen the air jets emitted by the sealing head (6) in the rest position is provided with a nozzle (251) that emits a jet of cooling air onto the continuous seals produced by the said head (6) in the active position.
  15. Apparatus according to Claim 10, in which there may be located at the discharge port of the hot compressed air generator (39) a deflector device which in phase with the up or down movement of the sealing head (6) switches its state so as to supply the sealing fluid to the head or deflect it in other directions, optionally to a recovery or recirculating circuit, respectively, the whole being such that when the sealing head is raised, it is promptly fully operational.
  16. Apparatus according to Claim 1, in which the sealing head (6) is attached to the moving part of a rectilinear actuator (45) mounted on a slide (46) that moves on guide means (47) parallel to the movement of the said actuator, the said slide being pushed in one direction by elastic means (48) and being movable in the opposite direction by means of an adjusting screw (49), all in such a way that it is possible to adjust the distance of the sealing head (6) from the film to be sealed when in the active sealing position.
  17. Apparatus according to Claim 16, in which the actuator (45) is a double-acting fluid-pressure cylinder with a non-rotating rod.
  18. Apparatus according to Claim 16, in which the rectilinear actuator (45) is of the type controlled by a motor with electronic control of speed and phase, so that the sealing head (6) can be moved towards and away from the film with appropriate decelerations and accelerations correlated to the starting and stopping of the film.
  19. Apparatus according to Claim 2, characterized in that in the application to a machine for packaging products in barrier-effect stretch film, of the type that comprises a horizontal film-tubularizing mandrel (1), with the longitudinal edges of the film overlapped underneath the mandrel and sealed tightly by special means (6), that comprises a fixed tubular guide (1') passing longitudinally through the said mandrel in order to insert the product to be packaged in the tubular packaging, that comprises, upstream of the mandrel, means (27, 127, 28) for the controlled supply of packaging film, and that comprises, downstream of the said mandrel, gripping pincers (7, 7') for double sealing and intermediate cutting, that alternate upstream and downstream of the tubular packaging with the product inside, to form the said packaging with a prior longitudinal stretching operating, characterized in that the opposing block (31) on which the longitudinal edges of the film to be sealed are pressed and guided is fixed to the outer face of the bottom wall of the said guide (1'), while the guide roller (33) is mounted by its spindle (133) to the lower flanges of the said mandrel (1), which has a large slot (32) through which the said opposing block passes and through which the overlapping edges of the film are visible and can be prepared by the sealing head (6), the lifting and lowering actuator (45) of which is controlled by the main computer (29) in such a way that the said head is up while the film is advancing is synchronized to be down when the said film is stopped, and is temporarily raised during the phase of longitudinal stretching of each packaging, before the back of the packaging is closed.
Anspruch[fr]
  1. Dispositif de thermoscellage étanche continu des bords longitudinaux à recouvrement de pièces tubulaires de film thermoplastique dont l'épaisseur peut être limitée, produit en déroulant le film d'une bobine et en faisant avancer le film longitudinalement dans un mandrin (1) de tubularisation, le dispositif comprenant des moyens (31, 33) de guidage et de maintien des bords longitudinaux du film tubularisé, de façon à ce qu'ils se recouvrent en ayant un contact intime et réparti suffisamment et dans une position d'opposition, à peu de distance de ces moyens de guidage, une tête (6) de scellage en un matériau ayant une bonne résistance mécanique et ayant un petit coefficient de frottement par rapport au film à sceller et un grand degré d'isolation thermique, qui dirige sur les bords du film à sceller au moins un jet continu d'air ou d'un autre gaz porté à une température appropriée et sous une pression appropriée, qui communique par des moyens (38) souples ou à raccord avec un générateur fixé d'air (39) comprimé chaud commandé par des moyens (40 à 44) appropriés d'alimentation et de commande, et qui est montée sur des moyens de rapprochement et d'éloignement (45), de sorte que lorsque le film avance, la tête est placée au bon moment à une distance courte du film et est déjà pleinement opérationnelle, tandis que lorsque le film s'arrête, la tête est retirée au bon moment du film ; caractérisé en ce que les moyens de guidage des bords du film à sceller longitudinalement comprennent un bloc (31) plat d'opposition fixe d'une épaisseur appropriée sur lequel les bords du film glissent, ce bloc d'opposition étant arrondi d'une manière appropriée sur ses bords et étant en un polymère technique approprié, et en ce qu'il y a, immédiatement en aval du bloc (31) d'opposition, un autre moyen (33) de guidage qui agit sur la face des bords à recouvrement du film opposée à celle sur laquelle le bloc d'opposition agit, ceci afin d'assurer un contact constant entre le film et le bloc d'opposition, l'autre moyen de guidage étant, de préférence, aussi en un polymère technique.
  2. Dispositif suivant la revendication 1, dans lequel l'autre moyen (33) de guidage consiste en un galet ayant son axe (133) perpendiculaire à la direction d'avance du film.
  3. Dispositif suivant la revendication 1, dans lequel la tête (6) de scellage est en un polymère technique approprié.
  4. Dispositif suivant la revendication 1, dans lequel la tête (6) de scellage, vue en bout dans la direction d'avance du film à sceller, est d'une forme sensiblement rectangulaire, dont les grands côtés supérieurs sont biseautés et la face (34) supérieure de la tête a une empreinte qui est sensiblement la même ou qui ne diffère que peu de l'empreinte effective du bloc (31) d'opposition sur lequel glissent les bords du film à sceller.
  5. Dispositif suivant la revendication 4, dans lequel s'ouvre, sur la face (34) supérieure de la tête (6) de scellage, au moins une fente (35) rectangulaire dont les dimensions sont corrélées à l'épaisseur et aux caractéristiques du film à sceller, la fente étant orientée de façon à ce que sa dimension la plus grande soit dans la direction d'avance du film et communiquant avec une chambre (36) tampon d'un volume approprié formée à l'intérieur de la tête et communiquant par des conduits (136) ramifiés avec le conduit (38) souple et résistant à la chaleur partant du générateur (39) fournissant de l'air comprimé chaud.
  6. Dispositif suivant la revendication 5, dans lequel s'ouvrent, sur la face (34) supérieure de la tête (6) de scellage, deux fentes (35) rectangulaires disposées symétriquement pour produire sur les bords à recouvrement du film deux joints longitudinaux continus pour assurer l'étanchéité.
  7. Dispositif suivant la revendication 5, caractérisé en ce qu'afin de sceller des films étirables à effet de barrière d'une épaisseur d'environ 40 microns, les fentes (35) de la tête (6) de scellage ont une largeur d'environ 0,3 mm.
  8. Dispositif suivant la revendication 7, dans lequel les fentes (35) de la tête (6) de scellage sont séparées d'une distance d'environ 6 mm.
  9. Dispositif suivant la revendication 5, caractérisé en ce qu'afin de sceller des films étirables à effet de barrière d'une épaisseur d'environ 40 microns, des jets d'air chaud sortent par les fentes (35) de la tête de scellage à une température comprise entre 160 et 180°C, par exemple d'environ 170°C, et sous une pression comprise entre 0,1 et 0,8 bar, par exemple d'environ 0,2 à 0,4 bar.
  10. Dispositif suivant la revendication 1, dans lequel le générateur (39) fournissant l'air comprimé chaud communique par son entrée (239) pour de l'air avec une source fournissant de l'air comprimé, par l'intermédiaire d'un détendeur (40), alors que sa borne (339) électrique relie le générateur à une interface (41) d'alimentation électrique commandée par un processeur (42) qui, au moyen de capteurs (43) de la chaleur et de capteurs (143) de la pression, détecte la température et la pression de fonctionnement, respectivement, du générateur qui est relié à une unité (44) de programmation et de commande et qui est équipé d'une borne (142) de sortie qui, dans le cas d'une anomalie, indique à l'ordinateur (29) général de la machine d'emballage que la tête (6) de scellage doit être mise au repos et que des mesures d'urgence doivent être prises.
  11. Dispositif suivant la revendication 10, dans lequel le capteur (43) de chaleur et le capteur (143) de pression du générateur (39) d'air comprimé chaud sont placés à l'orifice (139) de sortie et à l'orifice (239) d'entrée, respectivement, du générateur.
  12. Dispositif suivant la revendication 10, dans lequel, dans des situations de fonctionnement normales, la tête (6) de scellage fonctionne continuellement à un débit normal et, lorsqu'elle est abaissée pour l'éloigner du film parce que le film est fixe, des moyens d'écran sont activés pour dévier le courant d'air comprimé chaud sortant de la tête.
  13. Dispositif suivant la revendication 12, dans lequel les moyens d'écran consistent en une lame (151) horizontale d'air comprimé froid ou à la température ambiante émis par une courte barre (51) fixe, la tête (6) de scellage se déplaçant vers un niveau inférieur à celui de cette barre lorsqu'elle est en la position basse ou en la position de repos.
  14. Dispositif suivant la revendication 13, dans lequel la barre (51) courte fixe, qui émet la lame (151) d'air pour dévier les jets d'air émis par la tête (6) de scellage dans la position de repos, est munie d'une buse (251) qui émet un jet d'air de refroidissement sur les joints continus produits par la tête (6) dans la position active.
  15. Dispositif suivant la revendication 10, dans lequel il peut être disposé à l'orifice de sortie du générateur (39) d'air comprimé chaud un dispositif de déviation qui, en phase avec le mouvement ascendant ou descendant de la tête (6) de scellage, passe d'un état à un autre, de manière à envoyer le fluide de scellage à la tête ou à le dévier dans d'autres directions, éventuellement vers un circuit de récupération ou de recirculation, respectivement, le tout étant tel que, lorsque la tête de scellage est soulevée, elle est rapidement pleinement opérationnelle.
  16. Dispositif suivant la revendication 1, dans lequel la tête (6) de scellage est fixée à la partie mobile d'un actionneur (45) rectiligne monté sur un coulisseau (46) qui se déplace sur des moyens (47) de guidage parallèles au mouvement de l'actionneur, le coulisseau étant poussé dans un sens par des moyens (48) élastiques et étant mobile dans le sens opposé au moyen d'une vis (49) de réglage, le tout de façon à ce qu'il soit possible de régler la distance de la tête (6) de scellage au film à sceller lorsque l'on est dans la position active de scellage.
  17. Dispositif suivant la revendication 16, dans lequel l'actionneur (45) est un vérin à fluide sous pression à double action ayant une tige qui ne tourne pas.
  18. Dispositif suivant la revendication 16, dans lequel l'actionneur (45) rectiligne est du type commandé par un moteur ayant une commande électronique de vitesse et de phase, de sorte que la tête (6) de scellage peut être rapprochée et éloignée du film en ayant des décélérations et des accélérations corrélées au démarrage et à l'arrêt du film.
  19. Dispositif suivant la revendication 2,caractérisé en ce que, dans l'application à une machine d'emballage de produits dans du film étirable à effet de barrière du type qui comprend un mandrin (1) horizontal de tubularisation du film, alors que les bords longitudinaux du film sont à recouvrement sous le mandrin et sont scellés d'une manière étanche par un moyen (6) spécial, qui comprend un guide (1') tubulaire fixe passant longitudinalement dans le mandrin afin d'insérer le produit à emballer dans l'emballage tubulaire, qui comprend en amont du mandrin des moyens (27, 127, 28) pour l'alimentation réglée du film d'emballage, et qui comprend en aval du mandrin des pinces (7, 7') de préhension pour le scellage double et le coupage intermédiaire, qui alternent en amont et en aval de l'emballage tubulaire ayant le produit à l'intérieur, pour former l'emballage par une opération antérieure d'étirage longitudinal, caractérisé en ce que le bloc (31) d'opposition sur lequel les bords longitudinaux du film à sceller sont pressés et guidés est fixé à la face extérieure de la paroi de fond du guide (1'), le galet (33) de guidage est monté par sa broche (133) sur les joues inférieures du mandrin (1) qui a une grande fente (32) par laquelle passe le bloc d'opposition et par laquelle les bords à recouvrement du film sont visibles et peuvent être préparés par la tête (6) de scellage, dont l'actionneur (45) de soulèvement et d'abaissement est commandé par l'ordinateur (29) principal, de façon à ce que la tête soit en haut alors que le film avance et en synchronisation soit en bas lorsque le film est arrêté, et soit soulevée temporairement pendant la phase d'étirage longitudinal de chaque emballage avant que le dos de l'emballage soit fermé.






IPC
A Täglicher Lebensbedarf
B Arbeitsverfahren; Transportieren
C Chemie; Hüttenwesen
D Textilien; Papier
E Bauwesen; Erdbohren; Bergbau
F Maschinenbau; Beleuchtung; Heizung; Waffen; Sprengen
G Physik
H Elektrotechnik

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