METHOD AND MACHINE FOR WRAPPING ARTICLES

Abstract: A method of wrapping articles (2) provides for feeding a sheet (3) of wrapping material onto a plate (17) of a conveyor (4); positioning the sheet (3) of wrapping material on the plate (17) in a substantially flat configuration; feeding an article (2) onto the sheet (3) of wrapping material on the plate (17); feeding the sheet (3) of wrapping material, the respective article (2) and the plate (17) at a given speed (V1) along a path (P1) extending in a given direction (D1); and folding the sheet (3) of wrapping material about the article (2) along the aforementioned path (P1).

Description: METHOD AND MACHINE FOR WRAPPING ARTICLES TECHNICAL FIELD The present invention relates to a method of wrapping articles. In particular, the present invention relates to a method of wrapping packets of cigarettes in sheets of overwrapping material, to which the following description refers purely by way of example. BACKGROUND ART Packets of cigarettes are normally wrapped in overwrapping material, in particular, respective sheets of polypropylene, to preserve the aroma and correct humidity of the tobacco. For which purpose, cellophaning machines are used, which comprise a first wrapping wheel along which a sheet of polypropylene is folded into a tube about a respective packet to form a tubular wrapping having projecting portions at the ends of the packet; and a second wheel along which the projecting portions of the tubular wrapping are folded onto the opposite ends of the packet of cigarettes. The method employed by known cellophaning machines provides for positioning a sheet of wrapping material in a fixed position along the path of a respective packet; feeding the packet against the sheet so that the sheet of wrapping material is drawn by the packet towards fixed folding surfaces located along the path of the packet and which form a first U-shaped fold about the packet; and completing the tubular wrapping by means of movable folding devices located along the path of the packet . The above method may be implemented in two ways : a first embodiment provides for feeding the packet along a given path on a wheel, positioning a sheet of wrapping material crosswise to the path of the packet, feeding the packet against the sheet of wrapping material, and drawing the sheet of wrapping material towards a fixed spindle to form the U-shaped fold about the packet; a second embodiment provides for rotating a wrapping wheel having pockets each comprising a bottom wall and two lateral walls, positioning a sheet of wrapping material opposite each pocket, keeping each sheet at a given distance from the bottom wall of the pocket by means of gripping members located at the lateral walls of the pocket, inserting a respective packet into the pocket so as to collide with the respective sheet of wrapping material , and drawing the sheet into and towards the bottom wall of the pocket so as to fold the sheet of wrapping material against the lateral walls and form the U-shaped fold about the packet. One form of the second embodiment is described in German Patent Application No. 1,511,585 in which the cellophaning machine is designed to operate i continuously. The demand for increasingly high-output cellophaning machines, in fact, calls for rotating the wrapping wheels continuously at relatively high speed. In actual fact, however, the cellophaning machine described in German Patent Application No. 1,511,585 and implementing the second embodiment of the wrapping method described above fails to provide for high production speeds on account of a number of drawbacks . One of the main drawbacks lies in the relatively high speed at which the packet on continuous machines collides with the sheet of wrapping material, thus resulting in stretching and, in some cases, in tearing of the sheet, on account of the continual reduction in the thickness of the polypropylene sheets for environment reasons and to reduce consumption of raw materials. A further drawback lies in the sheet slipping with respect to the packet as the sheet is drawn by the packet into the respective pocket. That is, though the distal ends of the lateral walls release the sheet as it is drawn inside the pocket, residual adherence of the sheet to the distal ends of the walls causes the sheet to slide with respect to packet. Adherence of the sheet to the ends of the walls is a frequent occurrence, and is caused by electrostatic charges or by residual suction exerted by suction retaining members . All the above drawbacks are therefore clearly due to mating of the packet and respective sheet of wrapping material involving a collision, the consequences of which are not easily controllable. European Patent application EP-503215-A1 discloses a continuos wrapping machine, which partially overcomes the above drawbacks . However, the wrappings produced by the wrapping machine disclosed in EP-503215-A1 have a relatively poor quality, owing to the fact that each wrapping sheet is U-folded around a respective product by pliers means , which are not able to sufficiently stretch the wrapping sheet around the product. In particular, an insufficient stretching of the wrapping sheet around the respective product results in a poor- quality wrapping when the wrapping sheet is made by transparent plastic foil like polypropylene. DISCLOSURE OF INVENTION It is an object of the present invention to provide a method of wrapping articles, designed to eliminate the aforementioned drawbacks . According to the present invention, there is provided a method of wrapping articles as recited in claim 1. The invention provides for preventing deformation of the sheet of wrapping material as the article is brought into contact with the sheet, by the sheet being laid flat and supported rigidly on a plate so that the high speed of the packet does not damage the sheet or result in incorrect positioning of the sheet with respect to the article. The present invention also relates to a machine for wrapping articles . According to the present invention, there is provided a machine for wrapping articles in respective sheets of wrapping material, as recited in claim 12. BRIEF DESCRIPTION OF THE DRAWINGS A non-limiting embodiment of the invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a side view, with parts removed for clarity, of a cellophaning machine implementing the method according to the present invention; Figure 2 shows a larger-scale side view, with parts removed for clarity, of a detail of the Figure 1 machine; Figure 3 shows a larger-scale view in perspective, with parts removed for clarity, of a detail of the Figure 1 and 2 machine; Figure 4 shows a larger-scale view in perspective, with parts removed for clarity, of a detail of the Figure 1-3 machine. BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates as a whole a cellophaning machine for overwrapping packets 2 of cigarettes in sheets 3 of polypropylene. i Machine 1 comprises a wrapping wheel 4 ; a wrapping wheel 5 indicated by the dash line in Figure 1; a supply device 6 for supplying packets 2 ; and a supply device 7 for supplying sheets 3. Wheel 4 comprises a disk 8 rotating, anticlockwise in Figure 1 and in a direction Dl, about a respective axis 9 perpendicular to the Figure 1 plane; and a number of conveying units 10 for conveying packets 2 and respective sheets 3 along a path PI. Units 10 are equally spaced about axis 9 with a spacing S, and are supported by disk 8. Along path PI are arranged in succession anticlockwise in Figure 1 : a supply station 11 where sheets 3 are supplied to respective units 10; a supply station 12 where packets 2 are supplied to respective units 10; a wrap-around station 13 where sheets 3 are wrapped about respective packets 2 ; two folding stations 14 and 15 where sheets 3 are folded about respective packets 2; and a transfer station 16 where packets 2 together with respective sheets 3 folded into a tube about packets 2 are transferred to wheel 5. With reference to Figures 1 and 2, each unit 10 comprises a plate 17; a gripping device 18 for gripping packets 2; and a folding tool 19. Each plate 17 is located at the periphery of disk 8, extends perpendicularly with respect to disk 8, and comprises a flat portion 20, and a curved portion 21 which, in practice, is defined by a cylindrical plate curving I about axis 9. Portions 20 and 21 are connected to each other and so arranged that curved portion 21 is located in front of flat portion 20 in traveling direction Dl. Each plate 17 is defined by a face 22 facing axis 9, and by a supporting face 23 opposite face 22 and having a number of holes 24 equally spaced on face 23 and connected to known suction channels not shown. Each folding tool 19 comprises a rod 25 extending perpendicularly to portion 20 of plate 17 and engaged in a guide 26 integral with disk 8. The end of rod 25 facing plate 17 comprises a folding blade 27 tapering towards the end and housing a heating body 28 for sealing polypropylene sheet 3 along packet 2 , i.e. for making the longitudinal lateral seal . The end of rod 25 facing axis 9 comprises a tappet roller 29 which cooperates with a fixed cam profile 30 shown by the dash line in Figures 1 and 2; and guide 26 houses a known spring (not shown) for pushing rod 25 towards profile 30 to keep roller 29 in contact with profile 30. With reference to Figures 1, 2 and 3, each device 18 for gripping packets 2 comprises a shaft 31, which is located between respective plate 17 and axis 9, extends perpendicularly through and on opposite sides of disk 8, and is supported by a bush 32 fitted to disk 8. Shaft 31 rotates about a respective axis 33 parallel to axis 9, and has one end integral with a rocker-arm lever 34 having two tappet rollers 35 and 36 guided by respective fixed cams 37 and 38 to orient shaft 31 about axis 33. A second end of shaft 31 is integral with a lever 39 supporting a rod 40, the ends of which in turn support for rotation two rocker arms 41 rotating about respective axes 42 parallel to each other and to the Figure 1 and 2 plane. As shown more clearly in Figure 3, each rocker arm 41 comprises a hub 43 which supports an arm 44 extending perpendicularly to axis 42 and supporting a gripping member 45 at the distal end, and an arm 46 extending perpendicularly to axis 42 and arm 44, and which supports at the distal end a tappet roller 47 cooperating with a respective cam 48 for controlling rotation of rocker arm 41 about axis 42. A spring 49 is provided between each hub 43 and rod 40 to transmit torque about axis 42 to the respective rocker arm 41, so that the two gripping members 45 are pushed towards each other . With reference to Figures 3 and 4, each gripping member 45 comprises a substantially parallelepiped plate 50 extending crosswise with respect to respective arm 44; and three blades 51, 52, 53 - which may be fewer or dispensed with entirely - extending parallel to axis 9 from three adjacent faces of plate 50 to grip a packet 2 of cigarettes . Each packet 2 of cigarettes comprises two parallel, opposite main faces 54 , two lateral faces 55 and two end faces 56, and has a longitudinal axis 57 parallel to faces 54 and 55. Gripping members 45 grip packets 2 by opposite end faces 56. That is, plates 50 are positioned contacting respective end faces 56, blades 51 and 52 are positioned contacting small end portions of opposite faces 54, and blades 53 are positioned contacting small end portions of front face 55 in traveling direction Dl. With reference to Figure 1, at station 11 for supplying sheets 3 to wheel 4 , device 7 comprises two pairs of rollers 58 for feeding a polypropylene strip 59, and a roller 60 cooperating with a counter-roller 61 to cut successive sheets 3 off strip 59. Roller 60 has known suction holes (not shown) for retaining sheet 3 about roller 60 and gradually releasing sheet 3 onto a respective plate 17. Roller 60, in fact, is substantially tangent to plates 17 so that each sheet 3 is fed tangentially onto a respective plate 17. At station 12 for supplying packets 2 to wheel 4 , device 6 feeds packets 2, equally spaced with a spacing SI and at a steady speed, along a path P2 substantially tangent to path PI and extending in a direction D2. Device 6 comprises two belt conveyors 62 and 63 and a plate 64; conveyors 62 and 63 comprise respective belts 65 and 66 along which respective draw teeth 67 are equally spaced with spacing SI; conveyor 62 comprises a top conveying branch 68 parallel to and partially facing a bottom conveying branch 69 of conveyor 63; and plate I 64 forms an extension of branch 68 and is parallel to and faces branch 69. Packets 2 are fed along path P2 with respective longitudinal axes 57 perpendicular to the Figure 1 and 2 plane, and are fed substantially tangentially onto respective plates 17. The end portion of plate 64 is located at wheel 4, directly over path PI, and, as a packet 2 reaches said end portion of plate 64, gripping members 45 of a unit 10 grip packet 2 as described previously, and transfer packet 2 onto a respective sheet 3 on plate 17 without altering the configuration of sheet 3. Wrap-around station 13 comprises a lobed drum 70 rotating about a respective axis 71 parallel to axis 9 and comprising two diametrically-opposite lobes 72, which have respective faces 73 in the form of a cylindrical sector curving about axis 71, and a number of suction holes 74 connected to known suction channels not shown. Each face 73 is tangent to face 23 of each plate 17 at curved portion 21 of plate 17. Folding station 14 comprises a curved plate 75 with a curvature centered with respect to axis 9, and having bristles 76 facing axis 9. Plate 75 is preceded, in traveling direction Dl in Figures 1 and 2 , by a roller 77 rotating about a respective axis 78 parallel to axis 9. At the next folding station 15, a movable folding tool 79 comprises a fixed support 80 supporting a plate 81 rotating with respect to support 80 about an axis 82 parallel to axis 9. In actual use, wheel 4 is rotated at a constant speed VI about axis 9 in direction Dl . At station 11, device 7 feeds sheets 3 successively onto respective plates 17 of units 10 as described previously. Each sheet 3 is fed tangentially onto respective plate 17, and has a portion 83 contacting flat portion 20, a portion 84 contacting curved portion 21, and an end portion 85 projecting from flat portion 20 at the rear of plate 17 in traveling direction Dl. Each sheet 3 is arranged on respective plate 17 in a preferably flat configuration; portions 83 and 84 in fact adhere to face 23 of plate 17, and portion 85 is maintained coplanar with portion 83 by the air resistance as wheel 4 rotates. Each unit 10 with respective sheet 3 travels through station 12 where device 18 removes packet 2 off plate 64 and deposits it onto flat portion 20 with sheet 3 interposed between packet 2 and portion 20 of plate 17. More specifically, as unit 10 nears station 12, shaft 31 is rotated anticlockwise in Figures 1 and 2 to move gripping members 45 away from plate 17 and into a position facing end faces 56 of a packet 2 on the end portion of plate 64. At the same time, cam 48 acts on rocker arms 41 so as to part gripping members 45 of unit 10. When members 45 are positioned facing faces 56, cam 48 is interrupted and rocker arms 41 are rotated by respective springs 49 to move plates 50 up to respective end faces 56 of packet 2. At this stage, plates 50 are brought into contact with faces 56, blades 51 and 52 are brought into contact with respective portions of faces 54 , and blades 53 are brought into contact with front face 55 in traveling direction Dl . As unit 10 advances further, shaft 31 is rotated clockwise in Figures 1 and 2 to deposit packet 2 onto plate 17. Transfer of packet 2 onto respective plate 17 is performed gradually and along a given portion of path PI , so that packet 2 contacts respective sheet 3 with absolutely no deformation of sheet 3. At station 13, unit 10 travels past lobed drum 70, which rotates clockwise in Figures 1 and 2 to bring faces 73 of lobes 72 into tangential contact with respective faces 23 of curved portions 21. As unit 10 advances further, the suction through holes 74 in face 73 is activated, and the suction through holes 24 in face 23 at curved portion 21 is deactivated, so that portion 84 of sheet 3 is wrapped about axis 71 of drum 70 and therefore lifted off plate 17 and decelerated with respect to portion 83 and packet 2 traveling in direction Dl . When detached from plate 17, portion 84 occupies a position of interference with path PI, i.e. is positioned crosswise with respect to path PI of respective packet 2 ; the deceleration of portion 84 causes packet 2 and gripping members 45 holding packet 2 in position to gradually collide with portion 84; and, as wheel 4 and drum 70 rotate further, portion 84 is gradually released by face 73, is wrapped gradually about front face 55, and, when finally released by face 73, is simply blown by air resistance onto face 54 of the packet. In other words, at this stage, sheet 3 is substantially folded into a U about packet 2. In particular, portion 83 is located between one face 54 and portion 20, and portion 84 is positioned contacting front face 55 and a main face 54, and has a portion 86 projecting from face 54 and facing portion 85. At station 14 , packet 2 and respective U-folded sheet 3 are fed past roller 77 - which rolls along portion 84 contacting face 54 to ensure portion 84 adheres firmly to face 54 - and in rapid succession past plate 75, the bristles 76 of which iron portion 84 to iron sheet 3 on packet 2 and so smooth out any wrinkles in sheet 3. At station 15, tool 79 brings plate 81 into contact with rear face 55 so as to fold portion 86 onto rear face 55. As unit 10 advances further, rod 25 is pushed by profile 30 outwards of wheel 4 to bring blade 27 into contact with rear face 55 and fold portion 85 onto portion 86 on rear face 55. Blade 27 is maintained contacting the folded portion 85 to enable body 28 to seal portion 85 to portion 86, i.e. to effect the longitudinal lateral seal. At this point, packet 2 and respective tubular- folded sheet 3 are transferred at station 16 to wheel 5 on which further known folding operations (not shown) are performed.

Claims: CLAIMS 1) A method of wrapping articles, the method comprising the steps of feeding a sheet (3) of wrapping material to a conveyor (4) , said sheet (3) of wrapping material comprising a first portion (83) and a second portion (84) ; feeding an article (2) to said conveyor (4) and onto said sheet (3) of wrapping material; feeding said sheet (3) of wrapping material and the respective article (2) at a given speed (VI) along a path (PI) extending in a given direction (Dl) , said first portion (83) being located upstream from the second portion (84) with respect to said direction (Dl) ; and folding said sheet (3) of wrapping material about said article (2) along said path (PI) ; said sheet (3) of wrapping material being positioned on said conveyor (4) in a substantially flat configuration contacting a respective plate (17) of said conveyor (4) ; and said article (2) being positioned contacting the respective sheet (3) of wrapping material on said plate (17) ; the method being characterized in that said article (2) is positioned contacting said first portion (83) , and in comprising the steps of detaching the second portion (84) of said sheet (3) of wrapping material from said plate (17) to position the second portion (84) in a position of interference with said path (PI) , and decelerating said second portion (84) with respect to said first portion (83) in said direction (Dl) so as to partially wrap said sheet (3) of wrapping material around said article (2) . 2) A method as claimed in Claim 1, and comprising the further steps of gradually releasing said second i portion (84) ; and feeding along said path (PI) the article (2) and respective sheet (3) of wrapping material partially wrapped around said article (2) . 3) A method as claimed in Claim 1 or 2 , wherein said plate (17) has a face (23) substantially parallel to said path (PI) ; said sheet (3) of wrapping material being fed onto said respective plate (17) tangentially to said face (23) . 4) A method as claimed in any one of Claims 1 to 3, wherein said article (2) is transferred to said conveyor (4) along a further path (P2) substantially tangent to said path. 5) A method as claimed in Claim 4, wherein said article (2) is transferred from said further path (P2) to said path (Pi) by a gripping device (18) associated with said plate (17) . 6) A method as claimed in Claim 5, characterized in that said articles (2) are picked up by gripping members (45) associated with said gripping device (18) ; said gripping members (45) being movable in directions crosswise to said path (PI) and said further path (P2) . 7) A method as claimed in Claim 6, wherein said articles (2) are parallelepiped packets (2) comprising six faces (54, 55, 56) parallel in pairs; said gripping members (45) comprising respective gripping plates (50) ; and said gripping plates (50) engaging a said packet (2) by two opposite parallel faces (56) of the packet (2) . 8) A method as claimed in Claim 7, wherein each gripping member (45) comprises blades (51, 52, 53) extending crosswise with respect to said gripping plate (50); said blades (51, 52, 53) being brought into contact with further faces (54, 55) of said packet (2). 9) A method as claimed in any one of Claims 1 to 8, wherein said step of partially wrapping said sheet (3) of wrapping material around said article (2) comprises folding the sheet (3) substantially into a U about said article (2) ; the method comprising the further step of ironing said second portion (84) of the sheet (3) of wrapping material folded into a U about said article (2) by means of a fixed plate (75) located along said path (PI) . 10) A method as claimed in Claim 9, wherein said sheet (3) of wrapping material folded into a U comprises two end portions (85, 86) projecting with respect to said article (2) ; the method comprising the further step of folding said two end portions (85, 86) onto said article (2) and one on top of the other to form from said sheet (3) of wrapping material a tubular wrapping about said article (2) . 11) A method as claimed in Claim 10, and comprising the step of sealing said two end portions (85, 86) to each other. 12) A machine for wrapping articles in respective sheets (3) of wrapping material, the machine comprising a conveyor (4) having a number of conveying units (10) equally spaced along the conveyor (4) ; said conveying units (10) being movable along a path (PI) in a given direction (Dl) and at a given speed (VI) ; each conveying unit (10) comprising a plate (17) for conveying a respective sheet (3) of wrapping material in a substantially flat configuration, and a gripping device (18) for gripping said articles (2) and placing a respective article (2) on the respective sheet (3) of wrapping material in said substantially flat configuration; and said machine being characterized in that said gripping device (18) is movable with respect to said plate (17) between a lowered position and a raised position; said gripping device (18) keeping a said article (2) in contact with a first portion (83) of said sheet of wrapping material; said machine comprising wrap-around means (70) for picking up a second portion (84) of said sheet (3) of wrapping material; said first portion (83) being located upstream from the second portion (84) with reference to said direction (Dl) ; said wrap-around means (70) being movable for detaching the second portion (84) of said sheet (3) of wrapping material from said plate (17) , positioning said second portion (84) in a position of interference with said path (PI) , and decelerating said second portion (84) with respect to said first portion (83) in said direction (Dl) so as to partially wrap said sheet (3) of wrapping material around said article (2) . 13) A machine as claimed in Claim 12, wherein said wrap-around means (70) are located along said path (PI) ; said wrap-around means (70) comprising a lobed drum (70) rotating about an axis (71) crosswise to said path (PI) ; said lobed drum (70) having at least one face (73) tangent to said plate (17) along said path (PI) ; and said face (73) having means (74) for retaining said second portion (84) of the sheet (3) of wrapping material . 14) A machine as claimed in Claim 15, wherein said conveyor (4) is a wrapping wheel (4) rotating about a further axis (9) ; said axis (71) being parallel to said further axis (9) ; and the conveying units (10) being equally spaced about said further axis (9) . 15) A machine as claimed in any one of Claims 12 to 14, and comprising a device (7) for supplying sheets (3) of wrapping material and located along said path (PI) ; said device (7) for supplying sheets (3) of wrapping material comprising a drum (60) tangent to said plates (17) along said path (PI) . 16) A machine as claimed in any one of Claims 12 to 15, and comprising a device (6) for supplying said articles (2) to said conveyor (4) ; said device (6) for supplying said articles (2) extending along a further path (P2) substantially tangent to said path (PI) . 17) A machine as claimed in Claim 16, wherein said gripping device (18) is movable about a respective axis (33) of oscillation parallel to said further axis (9) ; said gripping device (18) comprising gripping members (45) for gripping said articles (2) along said further path (P2) and depositing the articles (2) on the respective plates (17) along said path (PI) . 18) A machine as claimed in Claim 17, wherein said gripping members (45) are movable crosswise to said direction (Dl) . 19) A machine as claimed in Claim 18, wherein each gripping device (18) comprises two respective gripping members (45) located on opposite sides of said path (PI) ; each gripping member (45) being movable with respect to the other gripping member (45) to grip and release said articles (2) . 20) A machine as claimed in Claim 19, wherein said two gripping members (45) comprise respective gripping plates (50) ; said gripping plates (50) being selectively brought into contact with and on opposite sides of said articles (2) . 21) A machine as claimed in Claim 20, wherein said two gripping members (45) comprise respective blades (51, 52, 53) extending from said gripping plates to engage respective portions of said articles (2) .

Inventors: DRAGHETTI FIORENZO, DRAGHETTI, FIORENZO
Applicants: DRAGHETTI FIORENZO, GD SPA, DRAGHETTI, FIORENZO, G.D SOCIETA' PER AZIONI
Application year: 2000
Main classification: B65B11
IPC codes: B65B11