METHOD AND MACHINE FOR WRAPPING INFUSION BAGS IN OUTER ENVELOPES

Abstract: A method and related machine for wrapping filter-bags (1) in sealed outer envelopes (S) comprises the following steps: feeding single, plane sheets (6) to a station (7) for wrapping each sheet (6) over a corresponding filter bag (1); folding the sheet (6) into a U-shape about a transversal axis (X) of the sheet (6) itself so as to form at least two opposite wings (6a, 6b) between which the filter bag (1) is placed; rolling the longitudinal edges (8a, 8b) of the U-shaped sheet (6) so as to flatten them; and, lastly, joining at least the longitudinal edges (8a, 8b) of the U-shaped sheet (6) to form a sealed outer envelope (S) around the filter bag (1).

Description: Description METHOD AND MACHINE FOR WRAPPING INFUSION BAGS IN OUTER ENVELOPES Technical Field The present invention relates to a method for wrapping filter bags for products for infusion such as coffee, tea, camomile and the like in sealed outer envelopes and the machine that implements the method. Background Art At present, machines for making filter bags comprise a plurality of stations, located one after the other, in which the filter bags are made. Each filter bag contains a charge of product closed in a corresponding chamber. Depending on the type of product it contains and the machine used to make it, the filter bag has one or two chambers and is joined m one of several different known ways (for example, by knotting, heat sealing or by means of a heat sealed stamp) to a string that connects it to a pick-up tag which is joined in one of several different known ways (for example, by knotting, heat sealing or by means of a stamp) to the free end of the string. The string and the pick-up tag are suitably positioned on the filter bag thus made (for example wound around the bag and connected to it or tucked inside it) to form a product that is ready to be packed in suitable cartons or boxes. Before groups of filter bags are packed m boxes, the filter bags may be individually wrapped in an outer envelope consisting of a sheet of wrapping material folded around each filter bag and heat sealed m one of two different ways: on at least two longitudinal sides or edges of the outer envelope if the latter has an opening flap folded over one of the surfaces of the envelope itself; or simultaneous heat sealing on three sides of the outer envelope, that is to say, two longitudinal edges and one transversal edge, if the envelope is of the simple type, that is to say, without the opening flap. Known machines used to wrap the filter bags n individual outer envelopes have a filter bag handling station comprising a plurality of grippers mounted radially on a starwheel, each being designed to pick up a single filter bag. As the starwheel turns, the filter bags are carried to different stations where the string and tag are joined to each other and to the filter bag and then to an wrapping station where a web of wrapping material is cut into separate sheets, each of which will form the outer envelope of a corresponding filter bag. Close to this station, the filter bag is moved radially away from the starwheel to enable the sheet of wrapping material to be fed between it and the starwheel. The filter bag is then moved close to the starwheel again to enable the sheet of wrapping material to be folded into a U shape around the filter bag. During this step, the opening flap of the outer envelope may also be formed by suitable folding means at the station, the flap being held in place by a presser element on the gπpper elements on the starwheel. After this, the filter bag with the sheet of wrapping material folded in a U shape around it, is carried to a sealing station where two or three edges of the sheet formed by the previous folding operation are sealed by suitable sealing means consisting of two or three elements depending on the type of outer envelope to be made. The filter bag thus sealed in its outer envelope is then fed to the stacking and final cartoning stations. This method, consisting in sealing the edges of the outer envelope after simply folding it, often results in a poor quality finish owing to the difficulty of correctly sealing the two longitudinal edges and, m the case of a simple outer envelope without opening flap, the transversal edge simultaneously. Indeed, during the folding step, the longitudinal edges in particular, are difficult to place squarely over each other since the wrapping material follows the shape of the filter bag which is not firm enough to enable a neat, square fold to be made. This results m skew seals and crinkling along the edges of the outer envelope which are not only unattractive but which also do not adequately protect the product inside. This problem is accentuated by the physical properties of the wrapping material from which the outer envelope is made and whose relative rigidity prevents it from keeping its shape before and after sealing. Disclosure of the Invention The present invention has for an object to overcome the above mentioned problem by providing a method and a machine for wrapping filter bags in sealed outer envelopes in an extremely simple, fast and efficient manner without altering the general structure of existing machinery for this purpose, so as to make outer envelopes of good quality and ensuring a proper seal. Accordingly, the invention provides a method for wrapping filter bags for products for infusion n individual sealed outer envelopes, the filter bags being of the type comprising at least one chamber containing a charge of product and a string connected at one end to the chamber itself, while the other end of the string is connected to a pick-up tag, the method comprising the following steps: feeding a succession of single, plane sheets to a station for wrapping each sheet over a corresponding filter bag; folding the sheet into a U-shape about a transversal axis of the sheet itself so as to form at least two opposite wings between which the filter bag is placed; and joining at least the longitudinal edges of the U-shaped sheet to form a sealed outer envelope around the filter bag; the method being characterised n that between the step of folding the sheet and the step of joining its longitudinal edges, it comprises a further step of rolling the longitudinal edges so as to flatten them. The present invention also provides a machine for wrapping filter bags for products for infusion m individual sealed envelopes, the filter bags being of the type comprising at least one chamber containing a charge of product and a string connected at one end to the chamber itself, while the other end of the string is connected to a pick-up tag, the machine comprising handling means for moving each filter bag m a working direction towards a station for wrapping a single, plane sheet of wrapping material around the filter bag; means for folding the sheet of wrapping material about a transversal axis of it to form a U- shaped wrapping around the filter bag, with at least two opposite wings between which the filter bag is placed; and a station for joining at least two longitudinal edges of the U-shaped wrapping sheet to form a single sealed envelope around the filter bag; the machine further comprising between the wrapping station and the joining station a rolling station designed to flatten the longitudinal edges. The technical characteristics of the invention, in accordance with the above-mentioned aims, are set out in the claims herein and the advantages more clearly illustrated in the detailed description which follows, with reference to the accompanying drawings, which illustrate preferred embodiments of the invention without restricting the scope of the inventive concept, and in which: - Figures 1 and 2 are front and perspective views showing a wrapping for a product for infusion with a sealed outer envelope, made using the method according to the present invention and having a front flap for opening the envelope itself; - Figure 3 is a front view of another wrapping for a product for infusion, with an outer envelope made using the method according to the present invention and sealed on three of its edges; - Figure 4 is a schematic perspective view, with some parts cut away for clarity, of a part of a machine for making filter bags and wrapping them in individual sealed outer envelopes according to the present invention; - Figure 5 is a partial perspective view of another embodiment of the machine illustrated m Figure 4; - Figure 6 is a schematic side view, with some parts cut away m order to better illustrate others, of an operating station forming part of the machine shown m Figures 4 and 5; - Figure 7 is a scaled-up schematic side view of a part of the machine illustrated m Figures 4, 5 and 6; - Figure 8 is a schematic top plan view of a portion of a web of wrapping material used to make outer envelopes for filter bags having some parts with cold glue on them. With reference to the accompanying drawings, in particular Figures 1 to 3, the method for wrapping filter bags m individual sealed outer envelopes can be used for filter bags 1 comprising one or two chambers 2, each containing a charge 3 of product and a string 4 connected at one end to the chamber or chambers 2 and a tag 5 connected to the other end of the string 4 (a double chamber filter bag is illustrated purely by way of example in Figure 2) . As shown in Figure 1 to 4, the filter bag 1 is wrapped in a sealed outer envelope S made from a sheet 6 of paper or heat- sealable wrapping material or material having some parts with cold glue on them (as described in more detail below) , which is folded into a U shape. In a first wrapping style (see Figures 1 and 2), the sealed outer envelope S is made from a sheet 6 preferably of paper, folded into a U shape to form two wings 6a and 6b, between which the filter bag 1 is placed, and has an opening flap 9 formed by an extension of the wing 6a folded over itself and over the other wing 6b, and two longitudinal edges 8a and 8b made by joining the corresponding longitudinal edges of the wings 6a and 6b of the sheet 6. In a second wrapping style (see Figure 3) , the sealed outer envelope S is made from a sheet 6 preferably of heat-sealable material or of material having parts with cold glue on them, folded into a U shape to form two wings 6a and 6b between which the filter bag 1 is placed. This wrapping has a top end 10 made by joining, preferably by heat sealing or by simply pressing, the transversal edges or ends 10a and 10b of the corresponding wings 6a and 6b of the sheet 6, and two longitudinal ends 8a and 8b made by joining, preferably by heat sealing or by simply pressing, the corresponding longitudinal edges of the wings 6a and 6b. The wrapping method, implemented by the machine M illustrated m Figure 4 as described in more detail below, comprises the following steps: feeding a succession of single, plane sheets, cut off from a web of wrapping material, to a station 7 for wrapping the sheets 6 around the filter bags 1; at the station 7, folding each sheet 6 about a transversal axis X of the sheet 6 to form a U-shaped wrapping around a corresponding filter bag 1 with at least two wings 6a and 6b facing each other; looking n more detail, the folding operation itself is performed in a known manner by lowering the filter bag 1, placing the sheet 6 between the filter bag 1 and suitable handling means 12, and then raising the filter bag 1 towards the means 12 (see arrows F3 and F4 in Figures 4 and 5) ; rolling the longitudinal edges 8a and 8b of the wings 6a and 6b of each U-shaped wrapping together on both sides of the U-shaped wrapping so as to flatten the longitudinal edges 8a and 8b and keep them aligned; joining the longitudinal edges 8a and 8b of the sheet 6 to a form a single, sealed outer envelope S containing a filter bag 1. If sheets 6 with cold glue on the edges 8a and 8b and on the transversal ends 10a and 10b (as shown in Figure 8) are being used, the rolling and joining steps are performed simultaneously since the rolling action also has the effect of pressing together the parts with the cold glue on them. If the sheet 6 folded into a U shape includes the opening flap 9 (shown n Figures 1 and 2), previously formed according to a known method, which is not illustrated, during the step of folding the wings 6a and 6b, the rolling step is also applied to the outer edges 9a and 9b of the open flap 9 itself, so as to correctly align the outer edges 9a and 9b with the longitudinal edges 8a and 8b below them. Instead, if the U-shaped sheet 6 is of the type illustrated n Figure 3 to be joined preferably by heat sealing on three edges or sides, the method comprises a further step of joining the transversal edges 10a and 10b preferably by heat sealing before the step of rolling the longitudinal edges 8a and 8b of the wings 6a and 6b (see Figure 5 m particular) . In this case too, if the transversal edges 10a and 10b have cold glue on them, the joining step s performed by simply pressing the eαges 10a and 10b together. Tne method described above is implemented by the machine M illustrated m Figure 4. The specific part of the machine to which the present invention relates comprises handling means 12 for moving the filter bag 1 in a working direction A towards a plurality of stations for simultaneously completing the formation of the filter bag 1 with string 4 and pick-up tag 5. In particular, as illustrated in Figure 7, the handling means 12 comprise a rotary drum 12t equipped radially with a plurality of gripper elements 12p for picking up, handling and releasing the individual filter bags 1 and designed to carry each filter bag 1 to the wrapping station 7. The station 7 is equipped with means (of known type and therefore not illustrated) for folding the sheet 6 into a U shape about a transversal axis X of it, so as to form the two wings 6a and 6b. After the station 7, there is a station 11 for joining the superposed longitudinal edges 8a and 8b of the U-shaped sheet 6 to form a sealed outer envelope S. As shown clearly in Figure 4, between the wrapping station 7 and the station 11 for joining the longitudinal edges 8a and 8b, there is a station 14 for rolling the longitudinal edges 8a and 8b in order to flatten them. If the sheets 6 used have edges 8a, 8b and 10a, 10b with cold glue on them, the rolling station 14 also constitutes the station 11 for joining the longitudinal edges 8a and 8b. In other words, the station 11 is not used (that is, it is disabled or not fitted to the machine) . As illustrated in Figures 4, 5 and 6, the rolling station 14 comprises roller means 15 for the simultaneous and bilateral rolling of the longitudinal edges 8a and 8b so as to align the longitudinal edges 8a and 8b prior to being joined or to actually join them. As shown in more detail in Figure 7, if the sealed outer envelope S has an opening flap 9, each gripper 12p forming part of the handling means 12 comprises a presser element 12a which keeps the flap 9 in a fixed position against the outer surface of the wing 6b until it gets near the rolling station 14. Instead, if the outer envelope S is of the type sealed on three sides or edges, there is a station 16 for joining the top edges 10a and 10b of the sheet 6 by heat sealing or by simply pressing them together. The station 16 is located, relative to the working direction A, after the wrapping station 7 and before the rolling station 14. The joining station 16 (see Figure 5) comprises a gripper element 17 with heated jaws, in the event of heat sealed outer envelope, designed to heat seal the top ends 10a and 10b of the sheet 6 which is folded into a U shape. The rolling station 14, illustrated n more detail n Figure 6, comprises two opposite pairs of rollers 18 and 19 (shown schematically also m Figures 4 and 5) . The roller pairs 18 and 19 are supported by a bridge structure 20 forming a channel C to allow the sheet 6 folded into a U shape to pass through in a radial direction of feed F away from the grippers 12p. The roller pairs 18 and 19 are located on the sides of the bridge structure 20 and the rollers of each pair are in tangential contact with each other in such a way as to flatten the sheet 6 folded into a U between them while feeding it to the station 11 where the longitudinal edges 8a and 8b are joined. The joining station 11, which operates only if the edges 8a and 8b are heat sealed, comprises a rotary drum 21, whose outer surface has recesses 22 formed n it to accommodate the single sheets 6 wrapped in a U around the filter bags 1 feeding in from the rolling station 14, and a pressure head 23 mounted radially relative to the drum 21 and designed to join the longitudinal edges 8a and 8b, each recess 22 being moved to a position facing the head 23 and the head 23 then being moved towards and pressed against it (see arrows FI n Figure 6) . If the sealed outer envelope S is of the type illustrated in Figures 1 and 2, the pressure head 23 comprises a knurled presser element 23 of known type designed to oin the edges 8a and 8b by knurling, acting in conjunction with the recesses 22, which are also preferably knurled. Instead, if the sealed outer envelope S is of the type illustrated in Figure 3, the pressure head 23 comprises a heated element 23 designed to join the edges 8a and 8b by heat sealing. Close to the drum 21, there are means 24 designed to guide the U-shaped sheet 6 as it feeds out of the rolling station 14 so that the sheet 6 is accommodated securely n the recess 22 prior to the joining operation performed by the head 23, which is angularly spaced relative to the guide means 24. The guide means 24 comprise a frame 25 closed on at least three sides, located close to the drum 21 to delimit an area through which the U-shaped sheet 6 feeds out of the rolling station 14 and where a recess 22 is already positioned. In addition to the frame 25, the guide means 24 may comprise a presser element 26 fitted above the frame 25 to form a top closure operated by suitable synchronised drive means 27 that move it between a raised position where the element 26 is away from the recess 22 and a lowered position where the element 26 is in contact with a single U-shaped sheet 6 feeding out of the rolling station 14 so as to locate it n the recess 22. The method and the related machine described above therefore achieve the above mentioned aims by introducing a rolling station that flattens the longitudinal edges of the sheet so as to align and correctly position the edges over each other before the step of heat sealing them. The method provides sealed outer envelopes of high quality and without crinkled edges. Also, the rolling station introduced does not increase the complexity of the machine M since it is simply placed between the starwheel and an existing roller on the machine, even if it is now also used for sealing and not only to convey the sealed outer envelopes to further cartoning stations. Furthermore, it should be stressed that the rollers also act as feed means between the starwheel and the longitudinal sealing roller, which means that the rolling station has a twofold function. Moreover, if the sheets 6 being used are of the type with cold glue on them, the rolling station also functions as the sealing station where the edges can be joined by simply pressing them together, thus simplifying the structure of the machine. The use of rollers to flatten the edges of the outer envelope improves the quality of the end product because even if the material used is relatively rigid, the edges remain properly in place until they reach the point where the final seal is made. The invention described can be subject to modifications and variations without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements.

Claims: Claims 1. A method for wrapping filter bags (1) for products for infusion in individual sealed outer envelopes (S) , the filter bags (1) being of the type comprising at least one chamber (2) containing a charge (3) of product, and a string (4) connected at one end to the chamber (2) itself, while the other end of the string (4) is connected to a pick-up tag (5), the method comprising the following steps: feeding a succession of single, plane sheets (6) to a station (7) for wrapping each sheet (6) over a corresponding filter bag (1); folding the sheet (6) into a U- shape about a transversal axis (X) of the sheet itself around the filter bag (1) so as to form at least two opposite wings (6a, 6b) between which the filter bag (1) is placed; and joining at least the longitudinal edges (8a, 8b) of the sheet (6) folded into a U shape to form a sealed outer envelope (S) around the filter bag (1); the method being characterised in that after the step of folding the sheet (6) it further comprises at least a step of rolling the longitudinal edges (8a, 8b) so as to flatten them. 2. The method according to claim 1, characterised m that the step of rolling the longitudinal edges (8a, 8b) is performed between the step of folding the sheet (6) and the step of joining the longitudinal edges (8a, 8b) . 3. The method according to claim 1, where each sheet (6) has parts (8a, 8b) with cold glue on them, characterised m that the step of rolling the longitudinal edges (8a, 8b) also constitutes the step of joining the longitudinal edges (8a, 8b) which are the parts with the cold glue on them. 4. The method according to claim 1, characterised m that the step of rolling the longitudinal edges (8a, 8b) is performed simultaneously on both longitudinal edges (8a, 8b) and m such a way as to align the edges (8a, 8b) with each other. 5. The method according to claims 1 and 2, characterised in that the sheet (6) folded into a U shape also has on it an opening flap (9), extending from one of the wings (6a, 6b) and formed by folding a portion of the wing (6a) over itself n such a way that its inner surface comes into contact with the outer surface of the other wing (6b); the rolling step being performed also on the longitudinal outer edges (9a, 9b) of the opening flap (9) so as to also align them with the underlying longitudinal edges (8a, 8b) of the U-shaped sheet (6) . 6. The method according to claims 1 and 3, where each sheet (6) has parts (8a, 8b; 9a, 9b) with cold glue on them, characterised n that the sheet (6) folded into a U shape also has on it an opening flap (9), extending from one of the wings (6a, 6b) and formed by folding a portion of the wing (6a) over itself in such a way that its inner surface comes into contact with the outer surface of the other wing (6b); the rolling step being performed also on the longitudinal outer edges (9a, 9b) of the opening flap (9) with cold glue on them so as to also align them with and join them to the underlying longitudinal edges (8a, 8b) of the U-shaped sheet ( 6 ) . 7. The method according to claim 1, characterised in that the step of joining the longitudinal edges (8a, 8b) is performed after the rolling step which precedes a further step of joining top transversal edges (10a, 10b) of the wings (6a, 6b) of the U-shaped sheet ( 6) . 8. The method according to claim 7, characterised in that the joins are effected by heat sealing. 9. The method according to claim 7, where each sheet (6) has parts (8a, 8o; 9a, 9b; 10a, 10b) with cold glue on them, characterised in that the joins are effected by pressing. 10. Tne method according to claim 2 or 4 , characterised m that the rolling step is performed while the sheet (6) which is folded into a U shape around the filter bag (1) is being fed to a station (11) where the longitudinal edges (8a, 8b) are joined. 11. A machine (M) for wrapping filter bags (1) for products for infusion in individual sealed envelopes (S) , the filter bags (1) being of the type comprising at least one chamber (2) containing a charge (3) of product and a string (4) connected at one end to the chamber [ 2 ) itself, while the other end of the string (4) is connected to a pick-up tag (5), the machine comprising handling means (12) for moving each filter bag (1) in a working direction (A) towards a station (7) for wrapping a single, plane sheet (6) of wrapping material around the filter bag (1); means (13) for folding the sheet (6) of wrapping material about a transversal axis (X) of it to form a U-shaped wrapping around the filter bag (1), with at least two opposite wings (6a, 6b) between which the filter bag (1) is placed; and a station (11) for joining at least two longitudinal edges (8a, 8b) of the U-shaped wrapping sheet (6) to form a single sealed envelope (S) around the filter bag (1); the machine (M) being characterised in that t further comprises, after the wrapping station (7), at least a rolling station (14) designed to flatten and join the longitudinal edges (8a, 8b). 12. The machine according to claim 11, characterised in that the station (14) for rolling the longitudinal edges (8a, 8b) is located between the wrapping station (7) and the joining station (11) . 13. The machine according to claim 11, where each sheet (6) has parts (8a, 8b) with cold glue on them, characterised m that the station (14) for rolling the longitudinal edges (8a, 8b) also constitutes the joining station (11) since it presses together the edges (8a, 8b) with the cold glue on them so as to join them. 14. The machine according to claim 11, characterised m that the rolling station (14) comprises roller means (15) for simultaneously rolling the longitudinal edges (8a, 8b) and designed to align the longitudinal edges (8a, 8b) with each other. 15. The machine according to claim 11, characterised in that it further comprises means for forming from one of the wings (6a, 6b) on the U-shaped sheet (6) a flap (9) by folding a portion of the wing (6a) over itself n such a way that its inner surface comes into contact with the outer surface of the other wing (6b); the filter bag (1) handling means (12) comprising a presser element (12a) which keeps the flap (9) in a fixed position against the outer surface of the wing (6b) at least until it gets near the rolling station (14). 16. The machine according to claim 11, characterised in that between the wrapping station (7) and the rolling station (14) there is a further station (16) for joining the top transversal edges or ends (10a, 10b) of the U-shaped sheet (6). 17. The machine according to claim 16, characterised in that the further joining station (16) comprises a heated gripper element (17) designed to heat seal the top transversal edges or ends (10a, 10b) of the U-shaped sheet (6) . 18. The machine according to claim 16, where each sheet (6) has parts (8a, 8b; 10a, 10b) with cold glue on them, characterised in that the further joining station (16) comprises a gripper element (17) designed to press together the top transversal edges or ends (10a, 10b) of the U-shaped sheet (6) which have cold glue on them. 19. The machine according to claim 11, characterised in that the rolling station (14) comprises two opposite pairs of rollers (18, 19), supported by a bridge structure (20) forming a channel (C) to allow the sheet (6) folded into a U shape to pass through n a radial direction of feed (F) away from the handling means (12); the roller pairs (18, 19) being located at the ends of the channel (C) and the rollers of each pa r (18, 19) being m tangential contact with each other m such a way as to flatten the sheet (6) folded into a U between them while at the same time feeding it forward. 20. The machine according to claims 11 and 12, characterised n that the station (11) for joining the longitudinal edges (8a, 8b) comprises a rotary drum (21), whose outer surface has recesses (22) formed n it to accommodate the single sheets (6) wrapped in a U around the filter bags (1) feeding n from the rolling station (14), and a pressure head (23) mounted radially relative to the drum (21) and designed to join the longitudinal edges (8a 8b), each recess (22) being moved to a position facing the head (23) and the latter then being moved towards and pressed against it. 21. The machine according to claim 20, characterised in that the pressure head (23) comprises a heated element (23) designed to join the edges (8a, 8b) by heat sealing. 22. The machine according to claim 20 or 21, characterised in that the drum (21) is acted upon by means (24) designed to guide the U-shaped sheet (6) as it feeds out of the rolling station (14) so that the sheet (6) is accommodated securely n the recess (22) prior to the joining operation performed by the head (23), which is angularly spaced relative to the guide means (24) . 23. The machine according to claim 22, characterised m that the guide means (24) comprise a frame (25) closed on at least three sides, located close to the drum (21) to delimit an area through which the U-shaped sheet (6) feeds out of the rolling station (14), such area also comprising a recess (22). 24. The machine according to claim 23, characterised in that the guide means (24) further comprise a presser element (26) fitted above the frame (25) to form a top closure operated by suitable synchronised drive means (27) that move it between a raised position where the element (26) is away from the recess (22) and a lowered position where the element (26) is m contact with a single U-shaped sheet (6) feeding out of the rolling station (14) so as to locate it m the recess (22) .

Inventors: GHIRLANDI DANTE, GHIRLANDI, DANTE
Applicants: GHIRLANDI DANTE, IMA SPA, GHIRLANDI, DANTE, I.M.A. INDUSTRIA MACCHINE AUTOMATICHE S.P.A.
Application year: 2001
Main classification: B65B29
IPC codes: B65B11, B65B29, B65B51