Abstract:
A method is described for sealing a continuous tubular packaging ( 20 ), which is fed in a vertical direction, the continuous tubular packaging ( 20 ) being shaped as a continuous tubular element ( 20 ) exhibiting with a closed bottom ( 5 ), in which products are contained, and a group ( 1 ) for actuating the method. The group ( 1 ) comprises: sealing means ( 4 ), configured such as to act in a transversal direction with respect to the continuous tubular packaging ( 20 ) in order to separate an inner volume thereof, such that a closed stick pack ( 2 ), containing said products, and a new closed bottom ( 5 ) are formed; and compression means ( 8, 9 ) arranged downstream of the sealing means ( 4 ) with respect to the feeding direction (W) of the continuous tubular packaging ( 20 ), which are configured such as to compress the continuous tubular packaging ( 20 ), consequently eliminating air fluid contained therein, and which are activatable prior to sealing the continuous tubular packaging ( 20 ) with the sealing means ( 4 ). The method comprises steps of: sealing the continuous tubular packaging ( 20 ) in order to separate the internal volume thereof, thus forming a closed stick pack ( 2 ), containing the products, and a new closed bottom ( 5 ); and compressing the continuous tubular packaging ( 20 ), with a consequent evacuation of air fluid contained internally thereof, before sealing the continuous tubular packaging ( 20 ).

Description:
FIELD OF THE INVENTION 
     The present invention relates to a system for packaging loose products in envelopes made of a flimsy material, also known as stick-packs. In particular, the invention relates to a method for sealing a continuous tubular packaging and a group for actuating the method. 
     DESCRIPTION OF THE PRIOR ART 
     The prior art comprises machines for packaging products in stick packs which exhibit a vertical development, with output of the full stick packs in the lower zone, comprising: drawing means for intermittently unwinding a continuous sheet from a reel in a supply direction which is downwardly orientated; folding means which receive the continuous sheet in inlet and form in outlet a continuous tubular package which develops vertically and exhibits vertical edges that are superposed and in mutual contact; welding means for sealing the superposed vertical edges of the continuous tubular package; sealing means, arranged downstream of the welding means, for acting transversally on the tubular package forming a closed bottom thereof; dispensing means, activated in phase relation with the first sealing means, for introducing, on the bottom of the continuous tubular package, a batched quantity of product; cutting means, arranged downstream of the sealing means, for cutting from the continuous tubular package a stick pack containing a batched quantity of product and formed following the above-described stage of sealing the continuous tubular package Each tract of the continuous sheet therefore takes on a different configuration as it is moved along the machine, up until it acquires the shape of a stick pack into which a batched quantity of product has been introduced. 
     The drawing means are mobile pliers having alternating vertical motion for gripping the lower flap of the continuous tubular package, i.e. the lower flap of the lowest stick pack of the continuous tubular package, and impressing a downwards movement of the continuous tubular package corresponding to the desired length of each stick pack. The mobile pliers and the cutting means are activated in phase relation to each other and with the first and second sealing means and with the dispensing means. 
     The closed stick packs thus obtained exhibit a size which is connected to the relative internal volume, which internal volume is formed by the batched quantity of product introduced thereto and by an undesired quantity of air which has remained trapped during the stage of sealing. 
     Further, the greater volume of the stick packs makes the superposing of the stick packs problematic during the subsequent packing into containers thereof. 
     The aim of the present invention consists in providing a technical solution aimed at obviating the drawbacks of the prior art, mentioned herein above, costs of which are contained with respect to the results that are obtained. 
     SUMMARY OF THE INVENTION 
     This aim has been attained with a method for sealing a continuous tubular package supplied in a vertical direction and a sealing group which actuates the method. 
     In accordance with the invention, a group is defined for sealing a continuous tubular package in a vertical direction, the continuous tubular package having the shape of a continuous tubular element provided with a closed bottom, in which the products are contained, comprising: 
     sealing means configured such as to act transversally of the tubular packaging in order to separate an internal volume thereof, thus forming a closed stick pack, containing the products, and a new closed bottom characterized in that it further comprises: compression means arranged downstream of the sealing means with respect to the supply direction of the continuous tubular packaging, configured such as to compress the continuous tubular packaging with a consequent evacuation of air fluid contained internally thereof and activatable before sealing of the tubular packaging performed by the sealing means. 
     In accordance with the invention, a method is defined for sealing a continuous tubular packaging supplied in a vertical direction, the continuous tubular packaging having a shape of a continuous tubular element provided with a closed bottom wherein the products are contained, comprising a stage of sealing the continuous tubular packaging in order to separate the internal volume thereof, thus forming a closed stick pack containing the products, and a new closed bottom, characterized in that it further comprises a stage of compressing the continuous tubular packaging, with a consequent evacuation of air fluid contained therein, before sealing the continuous tubular packaging. 
     The fact of compressing the continuous tubular packaging before the relative sealing advantageously enables evacuating the air fluid contained internally thereof: the closed stick packs thus obtained exhibit an internal volume which is constituted substantially by the batched quantity of product, with all the positive implications this brings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific embodiments of the invention, and advantageous technical-functional characteristics thereof related to the embodiments, only partly deducible from the above description, will be described in the following, in accordance with what is set out in the claims and with the aid of the accompanying figures of the drawings, in which: 
         FIGS. 1-5  illustrate a transversal section of a system for packaging products in stick packs, during five operating stages thereof. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying figures of the drawings, a preferred embodiment is illustrated of a part of a system for packaging products in stick packs, denoted by reference numeral  10 , comprising the sealing group  1  which is object of the present invention. 
     Only the parts of the system  10  which directly cooperate with the sealing group have been illustrated, though other parts not represented, of known type, will be mentioned in general terms in the following description, without reference numerals. 
     The system  10  exhibits a vertical development with the outlet of the stick packs  2  in the lower zone U, and comprises: drawing means  3  for intermittently unwinding a continuous sheet from a reel in a supply direction W directed downwards; folding means which receive the continuous sheet in inlet and form in outlet a continuous tubular packaging  20  which develops vertically and exhibits vertical edges that are superposed in mutual contact; welding means for sealing the superposed vertical edges of the continuous tubular packaging  20 ; sealing means  4  arranged downstream of the welding means, for acting transversally on the continuous tubular packaging  20  to form an overlying closed bottom  5 ; dispensing means, activated in phase relation with the activation of the welding means and the sealing means  4 , for releasing, on the bottom  5  of the continuous tubular packaging  20  a batched quantity of product; cutting means  6 , comprising two abutting heads  6 A,  6 B which respectively bear a blade and a counter-blade, acting downstream of the sealing means  4  for cutting from the continuous tubular packaging  20  the stick pack  2  containing a batched quantity of product and formed following the above-described sealing stages of the continuous tubular packaging  20 . 
     The drawing means  3  are mobile pliers having vertical alternating motion for gripping the flow flap of the continuous tubular packaging  20 , i.e. the lower flap  7  of the envelope  2  of the continuous tubular packaging  20 , and for impressing a downwards movement on the continuous tubular packaging  20 ; the movement that the mobile pliers  3  impose time by time on the continuous tubular packaging  20  corresponds to the length of each stick pack  2  which it is desired to obtain. 
     As will clearly emerge from the present description, the mobile pliers  3 , the cutting means  6  and the sealing means  4  are activated in suitable phase relation with one another. The sealing group  1  of the invention comprises: the above-mentioned sealing means  4 , comprising two sealing heads, a first sealing head  4 A and a second sealing head  4 B, mobile in mutual nearing and distancing; and compression means, comprising two deformable elements, a first deformable element  8  and a second deformable element  9 , mounted respectively below the welding heads  4 A,  4 B for acting respectively on the lower lateral walls  2 A,  2 B of the stick pack  2  under formation. 
     The deformable elements  8 ,  9  are mounted such as to project from the sealing heads  4 A,  4 B; thus the deformable elements  8 ,  9  act on the lower lateral walls  2 A, 2 B of the stick pack  2  under formation of the continuous tubular packaging  20  prior to the welding heads  4 A,  4 B; the compression exerted by the deformable elements  8 ,  9  on the continuous tubular packaging  20  pushes the air upwards along the continuous tubular packaging  20 , beyond the sealing heads  4 A,  4 B. 
     The application of the sealing heads  4 A,  4 B against the lateral walls of the continuous tubular packaging  20  determines the formation of an underlying closed stick pack  2 , containing a batched quantity of product, and an overlying new closed bottom  5  of the continuous tubular packaging  20 . 
     The closed stick pack  2  thus formed advantageously exhibits an internal volume substantially constituted by a batched quantity of product: the air has been almost totally expelled before the sealing of the continuous tubular packaging  20  thanks to the compressive action exerted by the stick pack  2  being formed by the deformable elements  8 ,  9 . 
     The deformable elements  8 ,  9  each exhibit, for example, a surface  8 A,  9 A which is inclined downwards with respect to the supply direction W of the continuous tubular packaging  20 . This facilitates evacuation of the air before the stage of sealing performed by the second sealing means  4 ; during the compression stage the deformable elements  8 ,  9  contact the lower lateral walls  2 A,  2 B of the stick pack  2  under formation of the tubular packaging  20 , and are moved along a contact surface which progressively grows and expands in an upwards direction, which enables the air to be effectively conveyed beyond the sealing heads  4 A,  4 B (see the arrows schematically represented on the continuous tubular packaging  20  in  FIG. 4 ). 
     In the embodiment illustrated in the figures, each deformable element  8 ,  9  affords a through-hole  8 B,  9 B for increasing the degree of flexibility; alternatively, or additionally, one or more undercuts can be fashioned. 
     The deformable elements  8 ,  9  are for example made of silicone; other deformable materials could also be used which are able to resist the temperatures which are reached in proximity of the sealing heads  4 A,  4 B. Advantageously the use of silicone enables a predetermined friction to be exerted on the continuous tubular packaging  20  when the deformable elements  8 ,  9  compress the continuous tubular packaging  20 . 
     The deformable elements  8 ,  9 , as mentioned, are respectively borne by the sealing heads  4 A,  4 B, and perform a nearing/distancing movement in a horizontal direction; the deformable elements  8 ,  9  are also configured such that following the intercepting of the continuous tubular packaging  20 , they exert thereon not only a lateral compression but also a traction force in a same direction as the supply direction W of the continuous tubular package  20 . In other words, the deformable elements  8 ,  9  exert on the continuous tubular packaging  20  opposite horizontal compressive forces and a substantially vertical force which tensions the continuous tubular packages  20 , in the same direction as the supply direction W. This derives in particular: from the fact that the deformable elements  8 ,  9  exhibit inclined surfaces  8 A,  9 A in a downwards direction with respect to the supply direction W; from the shape of the central zone of the deformable elements  8 ,  9  in which the through-holes  8 B,  9 B are afforded; and from the conformation of the through-holes  8 B,  9 B (which in general can also be undercuts, as mentioned herein above). 
     The above description of the packaging system  10  implicitly relates to a single channel C (illustrated in  FIGS. 1-5 ), but is equally valid for a multi-channel packaging system  10 . A multi-channel packaging system  10  generally comprises a plurality of identical flanked channels, in each of which operate drawing means  3 , the first sealing means, the dispensing means, the sealing group  1  and the cutting means  6 . In this case one common sheet is wound on a reel and a supplementary station arranged downstream cuts the common sheet into longitudinal portions which supply the various channels. 
     In particular, single function units are predisposed which operate contemporaneously on all the channels. For example, one sealing group only is provided, constituted by the sealing heads and a number of pairs of deformable elements which is equal to the number of channels, a single cutting group, constituted by a blade and a counter-blade, and a single gripping and drawing group constituted by a common member  21  moving alternatingly vertically, which bears a number of pliers which is the same as the number of channels. 
     For a multi-channel packaging system of this type, the use of pairs of deformable elements  8 ,  9  associated to each single channel has been shown to be extremely advantageous: this is thanks to the tensioning effect that each pair of deformable elements  8 ,  9  exerts singly on each corresponding continuous tubular packaging  20  before the intervention of the sealing heads  4 A,  4 B. 
     The prior art teaches that the tensioning of each continuous tubular packaging  20  along a corresponding channel is not known a priori and depends on various factors, such as the friction that the folding elements exert on the single longitudinal portions of sheet, the presence of dirt in the channels, the peripheral or central position of the channels (usually peripheral channels are more tensioned with respect to central channels) etc.: as a consequence of the different tensioning along the channels the lower flaps  7  of the continuous tubular packages  20  are not usually at the same height, such that the subsequent cutting can lead to the formation of stick packs  2  of different lengths. This difference in tensioning of the channels cannot be compensated for by the drawing and gripping group, which acts continuously on all the channels. 
     Each single pair of deformable elements  8 ,  9  advantageously exerts a certain tensioning on a corresponding continuous tubular packaging  20 : if the continuous tubular packaging  20  is already sufficiently tensioned, the action of the deformable elements  8 ,  9  is irrelevant; differently, the action exerted by the deformable elements  8 ,  9  will tend to “stretch” the corresponding continuous tubular element  20  more greatly, with a consequent lowering of the low flap  7 . Overall, the action of the deformable elements  8 ,  9  fixed to the sealing heads  4 A,  4 B will tend to annul the staggering in height which occurs between the flaps  7  of the continuous tubular packaging  20  associated to different channels and will therefore facilitate the formation of stick packs  2  of a same size. 
     There follows a description of the operating stages of the system for packaging products in stick packs, illustrated in  FIGS. 1 to 5  with reference to an operating cycle, from which it is possible to deduce the phase relations between the dispensing means, the sealing group  1 , the cutting means  6 , the pliers  3  and the pick-up group  16  of the stick pack  2  in the lower zone U (illustrated in  FIGS. 4 ,  5 ), also part of the packaging system  10 . 
     In  FIG. 1  the sealing heads  4 A,  4 B are arranged in an engaged position A 1  in which they are in mutual contact in order to seal a portion of the continuous tubular packaging  20 , forming an underlying stick pack  2  and an overlying closed bottom  5 ; the deformable elements  8 ,  9  compress the stick pack  2  thus formed, contacting the lateral walls  2 A,  2 B of the stick pack. The cutting means  6  are in a disengaged position B 2 . The pliers  3  are in a raised position PS and the relative jaws  3 A,  3 B are in a disengaged position C 2 . 
     When the deformable elements  8 ,  9  contact the lateral walls of the stick pack  2  they guarantee a stable and certain positioning of the stick pack  2 , which advantageously facilitates the following grip of the lower flap  7  of the stick pack  2  by the pliers  3 . Further, the certain knowledge of the position of the stick pack  2  enables reducing the opening of the jaws  3 A,  3 B of the pliers  3  to a minimum and thus reducing the run of the jaws  3 A,  3 B from the engaged position C 1 , in which the jaws  3 A,  3 B grip the lower flap  7  of the stick pack  2 , and the disengaged position C 2 , in which the jaws  3 A,  3 B are opened. This enables the productivity of the packaging system  10  to be increased, thanks to the certain knowledge of the position assumed time by time by each stick pack  2 . 
     In prior art solutions, on the other hand, one or more stick packs were supported only by the tops thereof and could therefore oscillate about an equilibrium position, such that the position thereof was not precisely known during the functioning of the system: further, residual welding tension and/or residual tensions in the polymer material of the stick pack might combine to determine an equilibrium position of the stick pack which was different from the vertical position. Consequently, the jaws of the pliers had to be kept in an open position with an angular opening that took account of the uncertainty of the position assumable by the stick pack. Notwithstanding this, impacts between the jaws and the stick pack were not infrequent, which impacts prevented the stick pack from being gripped or even wrinkled it up, causing blockage in the packaging machine. 
     The solution of the present invention advantageously solves these drawbacks, as described herein above. 
     Following sealing of the continuous tubular packaging  20  by the sealing heads  4 A,  4 B, the dispensing means are activated to release a batched quantity of product (not illustrated) onto the closed bottom  5  thus formed. 
     In  FIG. 2  the sealing heads  4 A,  4 B have reached a disengaged position A 2  and the jaws  3 A,  3 B of the pliers  3  have reached an engaged position C 1 , in which they grip the lower flap  7  of the stick pack  2 . 
     In particular, the system  10  is activated such that the jaws  3 A,  3 B grip the lower flap  7  of the stick pack  2  before (or immediately after) the deformable elements  8 ,  9  have become completely disengaged from the lateral walls  2 A,  2 B of the stick pack  2  itself; in this way the stick pack  2  is gripped by the pliers  3  when it is still in a certain position, i.e. substantially vertical. 
     In  FIG. 3  the cutting means  6  have reached an engaging position B 1  in which the relative abutting heads  6 A,  6 B grip the stick pack  2  and the pliers  3 , while the jaws  3 A,  3 B in the engaged position C 1 , have reached a lowered position PA which has brought the stick pack  2  into the lower zone U of the packaging system  10 . 
     In the position illustrated in  FIG. 3 , the stick pack  2  laterally contacts an abutment  15  of the packaging system  10 . 
     In  FIG. 4  the cutting means  6 , which are in the engaged position B 1 , cut the stick pack  2  from the continuous tubular packaging  20 .  FIG. 4  also illustrates pick-up organs  16 , also belonging to the packaging system  10  and acting horizontally to pick up a stick pack  2  arranged in the lower zone U in contact with the abutment  15 . The pick-up organs  16  are provided for example with suckers  17  and are represented in  FIG. 4  in the act of picking up the stick pack  2 . 
     In  FIG. 4  the jaws  3 A,  3 B of the pliers  3 , which are in the lowered position PA, have reached the disengaged position C 2  in which they have released the lower flap  7  of the stick pack  2 , while the sealing heads  4 A,  4 B are reaching the engaged position A 1 . 
     The movement of the jaws  3 A,  3 B into the disengaged position C 2  occurs in phase relation with the picking-up of the stick pack  2  by the pick-up organs  16 . 
     In  FIG. 5  the sealing heads  4 A,  4 B have reached the engaged position A 1 , the cutting means  6  have reached the disengaged position B 2  and the pick-up organs  16  are bringing the stick pack  2  away from the lower zone U. 
     The above has been described by way of non-limiting example, and any constructional variants are considered to fall within the ambit of protection of the present technical solution, as claimed in the following.